Sample records for plant competition
-
Decision-making in plants under competition
Gruntman, Michal; Groß, Dorothee; Májeková, Maria; Tielbörger, Katja
2017-01-01
Plants can plastically respond to light competition in three strategies, comprising vertical growth, which promotes competitive dominance; shade tolerance, which maximises performance under shade; or lateral growth, which offers avoidance of competition. Here, we test the hypothesis that plants can ‘choose’ between these responses, according to their abilities to competitively overcome their neighbours. We study this hypothesis in the clonal plant Potentilla reptans using an experimental setu...
-
Plant-plant competition outcomes are modulated by plant effects on the soil bacterial community.
Hortal, S; Lozano, Y M; Bastida, F; Armas, C; Moreno, J L; Garcia, C; Pugnaire, F I
2017-12-19
Competition is a key process that determines plant community structure and dynamics, often mediated by nutrients and water availability. However, the role of soil microorganisms on plant competition, and the links between above- and belowground processes, are not well understood. Here we show that the effects of interspecific plant competition on plant performance are mediated by feedbacks between plants and soil bacterial communities. Each plant species selects a singular community of soil microorganisms in its rhizosphere with a specific species composition, abundance and activity. When two plant species interact, the resulting soil bacterial community matches that of the most competitive plant species, suggesting strong competitive interactions between soil bacterial communities as well. We propose a novel mechanism by which changes in belowground bacterial communities promoted by the most competitive plant species influence plant performance and competition outcome. These findings emphasise the strong links between plant and soil communities, paving the way to a better understanding of plant community dynamics and the effects of soil bacterial communities on ecosystem functioning and services.
-
Decision-making in plants under competition.
Gruntman, Michal; Groß, Dorothee; Májeková, Maria; Tielbörger, Katja
2017-12-21
Plants can plastically respond to light competition in three strategies, comprising vertical growth, which promotes competitive dominance; shade tolerance, which maximises performance under shade; or lateral growth, which offers avoidance of competition. Here, we test the hypothesis that plants can 'choose' between these responses, according to their abilities to competitively overcome their neighbours. We study this hypothesis in the clonal plant Potentilla reptans using an experimental setup that simulates both the height and density of neighbours, thus presenting plants with different light-competition scenarios. Potentilla reptans ramets exhibit the highest vertical growth under simulated short-dense neighbours, highest specific leaf area (leaf area/dry mass) under tall-dense neighbours, and tend to increase total stolon length under tall-sparse neighbours. These responses suggest shifts between 'confrontational' vertical growth, shade tolerance and lateral-avoidance, respectively, and provide evidence that plants adopt one of several alternative plastic responses in a way that optimally corresponds to prevailing light-competition scenarios.
-
Picking battles wisely: plant behaviour under competition.
Novoplansky, Ariel
2009-06-01
Plants are limited in their ability to choose their neighbours, but they are able to orchestrate a wide spectrum of rational competitive behaviours that increase their prospects to prevail under various ecological settings. Through the perception of neighbours, plants are able to anticipate probable competitive interactions and modify their competitive behaviours to maximize their long-term gains. Specifically, plants can minimize competitive encounters by avoiding their neighbours; maximize their competitive effects by aggressively confronting their neighbours; or tolerate the competitive effects of their neighbours. However, the adaptive values of these non-mutually exclusive options are expected to depend strongly on the plants' evolutionary background and to change dynamically according to their past development, and relative sizes and vigour. Additionally, the magnitude of competitive responsiveness is expected to be positively correlated with the reliability of the environmental information regarding the expected competitive interactions and the expected time left for further plastic modifications. Concurrent competition over external and internal resources and morphogenetic signals may enable some plants to increase their efficiency and external competitive performance by discriminately allocating limited resources to their more promising organs at the expense of failing or less successful organs.
-
Antagonistic interactions between plant competition and insect herbivory.
Schädler, Martin; Brandl, Roland; Haase, Josephine
2007-06-01
Interspecific competition between plants and herbivory by specialized insects can have synergistic effects on the growth and performance of the attacked host plant. We tested the hypothesis that competition between plants may also negatively affect the performance of herbivores as well as their top-down effect on the host plant. In such a case, the combined effects of competition and herbivory may be less than expected from a simple multiplicative response. In other words, competition and herbivory may interact antagonistically. In a greenhouse experiment, Poa annua was grown in the presence or absence of a competitor (either Plantago lanceolata or Trifolium repens), as well as with or without a Poa-specialist aphid herbivore. Both competition and herbivory negatively affected Poa growth. Competition also reduced aphid density on Poa. This effect could in part be explained by changes in the biomass and the nitrogen content of Poa shoots. In treatments with competitors, reduced aphid densities alleviated the negative effect of herbivory on above- and belowground Poa biomass. Hence, we were able to demonstrate an antagonistic interaction between plant-plant interspecific competition and herbivory. However, response indices suggested that antagonistic interactions between competition and herbivory were contingent on the identity of the competitor. We found the antagonistic effect only in treatments with T. repens as the competitor. We conclude that both competitor identity and the herbivore's ability to respond with changes in its density or activity to plant competition affect the magnitude and direction (synergistic vs. antagonistic) of the interaction between competition and herbivory on plant growth.
-
Plant Size and Competitive Dynamics along Nutrient Gradients.
Goldberg, Deborah E; Martina, Jason P; Elgersma, Kenneth J; Currie, William S
2017-08-01
Resource competition theory in plants has focused largely on resource acquisition traits that are independent of size, such as traits of individual leaves or roots or proportional allocation to different functions. However, plants also differ in maximum potential size, which could outweigh differences in module-level traits. We used a community ecosystem model called mondrian to investigate whether larger size inevitably increases competitive ability and how size interacts with nitrogen supply. Contrary to the conventional wisdom that bigger is better, we found that invader success and competitive ability are unimodal functions of maximum potential size, such that plants that are too large (or too small) are disproportionately suppressed by competition. Optimal size increases with nitrogen supply, even when plants compete for nitrogen only in a size-symmetric manner, although adding size-asymmetric competition for light does substantially increase the advantage of larger size at high nitrogen. These complex interactions of plant size and nitrogen supply lead to strong nonlinearities such that small differences in nitrogen can result in large differences in plant invasion success and the influence of competition along productivity gradients.
-
Orrock, John L; Dutra, Humberto P; Marquis, Robert J; Barber, Nicholas
2015-04-01
Direct and indirect effects can play a key role in invasions, but experiments evaluating both are rare. We examined the roles of direct competition and apparent competition by exotic Amur honeysuckle (Lonicera maackii) by manipulating (1) L. maackii vegetation, (2) presence of L. maackii fruits, and (3) access to plants by small mammals and deer. Direct competition with L. maackii reduced the abundance and richness of native and exotic species, and native consumers significantly reduced the abundance and richness of native species. Although effects of direct competition and consumption were more pervasive, richness of native plants was also reduced through apparent competition, as small-mammal consumers reduced richness only when L. maackii fruits were present. Our experiment reveals the multiple, interactive pathways that affect the success and impact of an invasive exotic plant: exotic plants may directly benefit from reduced attack by native consumers, may directly exert strong competitive effects on native plants, and may also benefit from apparent competition.
-
Competition overwhelms the positive plant-soil feedback generated by an invasive plant.
Crawford, Kerri M; Knight, Tiffany M
2017-01-01
Invasive plant species can modify soils in a way that benefits their fitness more than the fitness of native species. However, it is unclear how competition among plant species alters the strength and direction of plant-soil feedbacks. We tested how community context altered plant-soil feedback between the non-native invasive forb Lespedeza cuneata and nine co-occurring native prairie species. In a series of greenhouse experiments, we grew plants individually and in communities with soils that differed in soil origin (invaded or uninvaded by L. cuneata) and in soils that were live vs. sterilized. In the absence of competition, L. cuneata produced over 60% more biomass in invaded than uninvaded soils, while native species performance was unaffected. The absence of a soil origin effect in sterile soil suggests that the positive plant-soil feedback was caused by differences in the soil biota. However, in the presence of competition, the positive effect of soil origin on L. cuneata growth disappeared. These results suggest that L. cuneata may benefit from positive plant-soil feedback when establishing populations in disturbed landscapes with few interspecific competitors, but does not support the hypothesis that plant-soil feedbacks influence competitive outcomes between L. cuneata and native plant species. These results highlight the importance of considering whether competition influences the outcome of interactions between plants and soils.
-
The dynamic relationship between plant architecture and competition.
Ford, E David
2014-01-01
In this review, structural and functional changes are described in single-species, even-aged, stands undergoing competition for light. Theories of the competition process as interactions between whole plants have been advanced but have not been successful in explaining these changes and how they vary between species or growing conditions. This task now falls to researchers in plant architecture. Research in plant architecture has defined three important functions of individual plants that determine the process of canopy development and competition: (i) resource acquisition plasticity; (ii) morphogenetic plasticity; (iii) architectural variation in efficiency of interception and utilization of light. In this review, this research is synthesized into a theory for competition based on five groups of postulates about the functioning of plants in stands. Group 1: competition for light takes place at the level of component foliage and branches. Group 2: the outcome of competition is determined by the dynamic interaction between processes that exert dominance and processes that react to suppression. Group 3: species differences may affect both exertion of dominance and reaction to suppression. Group 4: individual plants may simultaneously exhibit, in different component parts, resource acquisition and morphogenetic plasticity. Group 5: mortality is a time-delayed response to suppression. Development of architectural models when combined with field investigations is identifying research needed to develop a theory of architectural influences on the competition process. These include analyses of the integration of foliage and branch components into whole-plant growth and precise definitions of environmental control of morphogenetic plasticity and its interaction with acquisition of carbon for plant growth.
-
Negative plant-soil feedbacks increase with plant abundance, and are unchanged by competition.
Maron, John L; Laney Smith, Alyssa; Ortega, Yvette K; Pearson, Dean E; Callaway, Ragan M
2016-08-01
Plant-soil feedbacks and interspecific competition are ubiquitous interactions that strongly influence the performance of plants. Yet few studies have examined whether the strength of these interactions corresponds with the abundance of plant species in the field, or whether feedbacks and competition interact in ways that either ameliorate or exacerbate their effects in isolation. We sampled soil from two intermountain grassland communities where we also measured the relative abundance of plant species. In greenhouse experiments, we quantified the direction and magnitude of plant-soil feedbacks for 10 target species that spanned a range of abundances in the field. In soil from both sites, plant-soil feedbacks were mostly negative, with more abundant species suffering greater negative feedbacks than rare species. In contrast, the average response to competition for each species was unrelated with its abundance in the field. We also determined how competitive response varied among our target species when plants competed in live vs. sterile soil. Interspecific competition reduced plant size, but the strength of this negative effect was unchanged by plant-soil feedbacks. Finally, when plants competed interspecifically, we asked how conspecific-trained, heterospecific-trained, and sterile soil influenced the competitive responses of our target species and how this varied depending on whether target species were abundant or rare in the field. Here, we found that both abundant and rare species were not as harmed by competition when they grew in heterospecific-trained soil compared to when they grew in conspecific-cultured soil. Abundant species were also not as harmed by competition when growing in sterile vs. conspecific-trained soil, but this was not the case for rare species. Our results suggest that abundant plants accrue species-specific soil pathogens to a greater extent than rare species. Thus, negative feedbacks may be critical for preventing abundant species from
-
Natal Host Plants Can Alter Herbivore Competition.
Pan, Huipeng; Preisser, Evan L; Su, Qi; Jiao, Xiaoguo; Xie, Wen; Wang, Shaoli; Wu, Qingjun; Zhang, Youjun
2016-01-01
Interspecific competition between herbivores is widely recognized as an important determinant of community structure. Although researchers have identified a number of factors capable of altering competitive interactions, few studies have addressed the influence of neighboring plant species. If adaptation to/ epigenetic effects of an herbivore's natal host plant alter its performance on other host plants, then interspecific herbivore interactions may play out differently in heterogeneous and homogenous plant communities. We tested wether the natal host plant of a whitefly population affected interactions between the Middle-east Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species of the whitefly Bemisia tabaci by rearing the offspring of a cabbage-derived MEAM1 population and a poinsettia-derived MED population together on three different host plants: cotton, poinsettia, and cabbage. We found that MED dominated on poinsettia and that MEAM1 dominated on cabbage, results consistent with previous research. MED also dominated when reared with MEAM1 on cotton, however, a result at odds with multiple otherwise-similar studies that reared both species on the same natal plant. Our work provides evidence that natal plants affect competitive interactions on another plant species, and highlights the potential importance of neighboring plant species on herbivore community composition in agricultral systems.
-
East-Asia nuclear/fossil power plant competitiveness
International Nuclear Information System (INIS)
Braun, Ch.
1996-01-01
The competitiveness of a new nuclear plant vs. a new oil or gas fired combined cycle plant or a coal fired plant in East-Asia, is reviewed in the paper. Both the nuclear and the fossil fired plants are evaluated as either utility financed or independent power producer (IPP) financed. Two types of advanced light water reactors (ALWRs) are considered in this paper, namely evolutionary ALWRs (1200 MWe size) and passive ALWRs (600 MWe class). A range of capital and total generation costs for each plant type is reported here. The comparison centers on three elements of overall competitiveness: generation costs, hard currency requirements, and employment requirements. Each of these aspects is considered perspective. Year-by-Year generation cost history over the plant lifetime is shown in some cases. It is found here that a utility financed evolutionary and passive ALWRs are broadly competitive with an IPP financed gas fired combined cycle plant and are more economic than oil fired combined cycle or a coal fired plant. A single unit evolutionary ALWR may have a 12 - 15 % capital cost advantage over a single passive ALWR then adjusted on a per KWe basis. Front-end hard currency requirements of a passive ALWR are 2.5 times higher than for a combined plant and evolutionary ALWRs requires 3.6 times higher up-front cost. However, on a lifetime basis, passive ALWR net hard currency requirements are two times lower than for a combined cycle plant. Evolutionary ALWR net hard currency requirements are three times over than those of a combined cycle plant. The effects of domestic vs. world price of fossil fuels on relative nuclear competitiveness are reviewed in this nuclear competitiveness paper. Employment requirements in an ALWR during both the construction period and lifetime operation, exceed the requirements for oil or gas fired plants by a factor of five. While contributing to overall plant cost, employment requirements can also be viewed as opportunity to increase national
-
Competition between herbage plants
Wit, de C.T.; Bergh, van den J.P.
1965-01-01
Starting from work with annuals a model of competition between herbage plants is discussed. It is shown that their mutual interference can only be described adequately if they are grown in mixture and also in monoculture
-
Negative plant-soil feedbacks increase with plant abundance, and are unchanged by competition
John L. Maron; Alyssa Laney Smith; Yvette K. Ortega; Dean E. Pearson; Ragan M. Callaway
2016-01-01
Plant-soil feedbacks and interspecific competition are ubiquitous interactions that strongly influence the performance of plants. Yet few studies have examined whether the strength of these interactions corresponds with the abundance of plant species in the field, or whether feedbacks and competition interact in ways that either ameliorate or exacerbate their...
-
Resource competition in plant invasions: emerging patterns and research needs.
Gioria, Margherita; Osborne, Bruce A
2014-01-01
Invasions by alien plants provide a unique opportunity to examine competitive interactions among plants. While resource competition has long been regarded as a major mechanism responsible for successful invasions, given a well-known capacity for many invaders to become dominant and reduce plant diversity in the invaded communities, few studies have measured resource competition directly or have assessed its importance relative to that of other mechanisms, at different stages of an invasion process. Here, we review evidence comparing the competitive ability of invasive species vs. that of co-occurring native plants, along a range of environmental gradients, showing that many invasive species have a superior competitive ability over native species, although invasive congeners are not necessarily competitively superior over native congeners, nor are alien dominants are better competitors than native dominants. We discuss how the outcomes of competition depend on a number of factors, such as the heterogeneous distribution of resources, the stage of the invasion process, as well as phenotypic plasticity and evolutionary adaptation, which may result in increased or decreased competitive ability in both invasive and native species. Competitive advantages of invasive species over natives are often transient and only important at the early stages of an invasion process. It remains unclear how important resource competition is relative to other mechanisms (competition avoidance via phenological differences, niche differentiation in space associated with phylogenetic distance, recruitment and dispersal limitation, indirect competition, and allelopathy). Finally, we identify the conceptual and methodological issues characterizing competition studies in plant invasions, and we discuss future research needs, including examination of resource competition dynamics and the impact of global environmental change on competitive interactions between invasive and native species.
-
Resource competition in plant invasions: emerging patterns and research needs
Gioria, Margherita; Osborne, Bruce A.
2014-01-01
Invasions by alien plants provide a unique opportunity to examine competitive interactions among plants. While resource competition has long been regarded as a major mechanism responsible for successful invasions, given a well-known capacity for many invaders to become dominant and reduce plant diversity in the invaded communities, few studies have measured resource competition directly or have assessed its importance relative to that of other mechanisms, at different stages of an invasion process. Here, we review evidence comparing the competitive ability of invasive species vs. that of co-occurring native plants, along a range of environmental gradients, showing that many invasive species have a superior competitive ability over native species, although invasive congeners are not necessarily competitively superior over native congeners, nor are alien dominants are better competitors than native dominants. We discuss how the outcomes of competition depend on a number of factors, such as the heterogeneous distribution of resources, the stage of the invasion process, as well as phenotypic plasticity and evolutionary adaptation, which may result in increased or decreased competitive ability in both invasive and native species. Competitive advantages of invasive species over natives are often transient and only important at the early stages of an invasion process. It remains unclear how important resource competition is relative to other mechanisms (competition avoidance via phenological differences, niche differentiation in space associated with phylogenetic distance, recruitment and dispersal limitation, indirect competition, and allelopathy). Finally, we identify the conceptual and methodological issues characterizing competition studies in plant invasions, and we discuss future research needs, including examination of resource competition dynamics and the impact of global environmental change on competitive interactions between invasive and native species. PMID
-
Neighbour tolerance, not suppression, provides competitive advantage to non-native plants.
Golivets, Marina; Wallin, Kimberly F
2018-05-01
High competitive ability has often been invoked as a key determinant of invasion success and ecological impacts of non-native plants. Yet our understanding of the strategies that non-natives use to gain competitive dominance remains limited. Particularly, it remains unknown whether the two non-mutually exclusive competitive strategies, neighbour suppression and neighbour tolerance, are equally important for the competitive advantage of non-native plants. Here, we analyse data from 192 peer-reviewed studies on pairwise plant competition within a Bayesian multilevel meta-analytic framework and show that non-native plants outperform their native counterparts due to high tolerance of competition, as opposed to strong suppressive ability. Competitive tolerance ability of non-native plants was driven by neighbour's origin and was expressed in response to a heterospecific native but not heterospecific non-native neighbour. In contrast to natives, non-native species were not more suppressed by hetero- vs. conspecific neighbours, which was partially due to higher intensity of intraspecific competition among non-natives. Heterogeneity in the data was primarily associated with methodological differences among studies and not with phylogenetic relatedness among species. Altogether, our synthesis demonstrates that non-native plants are competitively distinct from native plants and challenges the common notion that neighbour suppression is the primary strategy for plant invasion success. © 2018 John Wiley & Sons Ltd/CNRS.
-
Evaluating plant-soil feedback together with competition in a serpentine grassland.
Casper, Brenda B; Castelli, Jeffrey P
2007-05-01
Plants can alter biotic and abiotic soil characteristics in ways that feedback to change the performance of that same plant species relative to co-occurring plants. Most evidence for this plant-soil feedback comes from greenhouse studies of potted plants, and consequently, little is known about the importance of feedback in relation to other biological processes known to structure plant communities, such as plant-plant competition. In a field experiment with three C4 grasses, negative feedback was expressed through reduced survival and shoot biomass when seedlings were planted within existing clumps of conspecifics compared with clumps of heterospecifics. However, the combined effects of feedback and competition were species-specific. Only Andropogon gerardii exhibited feedback when competition with the clumps was allowed. For Sorghastrum nutans, strong interspecific competition eliminated the feedback expressed in the absence of competition, and Schizachyrium scoparium showed no feedback at all. That arbuscular mycorrhizal (AM) fungi may play a role in the feedback was indicated by higher AM root colonization with conspecific plant neighbours. We suggest that feedback and competition should not be viewed as entirely separate processes and that their importance in structuring plant communities cannot be judged in isolation from each other.
-
Molecular mechanisms of plant competition: neighbour detection and response strategies
Pierik, R.; Mommer, L.; Voesenek, L.A.C.J.
2013-01-01
Plant competition determines the diversity and species abundance of natural communities as well as potential yields in agricultural systems. Understanding the mechanisms of plant competition is instrumental to understanding plant performance in true vegetations. In this review, we will address
-
Limiting conditions for nuclear power plant competitiveness vs. fossil and wind plants
International Nuclear Information System (INIS)
Feretic, Danilo; Cavlina, Nikola
2010-01-01
The aim of this paper is to compare potential energy options for future electricity generation. The paper considers comparison of discounted total cost of electricity generated by nuclear power plant and by combined natural gas and wind plants, having in total equal electricity generation. Large uncertainty in the future fuel costs makes planning of optimal power generating mix very difficult to justify. Probabilistic method is used in the analysis which allows inclusion of uncertainties in future electricity generating cost prediction. Additionally, an informative functional relation between nuclear plant investment cost, natural gas price and wind plant efficiency, that determines competitive power generation between considered options, is also shown. Limiting conditions for nuclear power plant competitiveness vs. fossil and wind plants are presented. (authors)
-
Are invasive plants more competitive than native conspecifics? Patterns vary with competitors
Zheng, Yulong; Feng, Yulong; Valiente-Banuet, Alfonso; Li, Yangping; Liao, Zhiyong; Zhang, Jiaolin; Chen, Yajun
2015-10-01
Invasive plants are sometimes considered to be more competitive than their native conspecifics, according to the prediction that the invader reallocates resources from defense to growth due to liberation of natural enemies [‘Evolution of Increased Competitive Ability’ (EICA) hypothesis]. However, the differences in competitive ability may depend on the identity of competitors. In order to test the effects of competitors, Ageratina adenophora plants from both native and invasive ranges competed directly, and competed with native residents from both invasive (China) and native (Mexico) ranges respectively. Invasive A. adenophora plants were more competitive than their conspecifics from native populations when competing with natives from China (interspecific competition), but not when competing with natives from Mexico. Invasive A. adenophora plants also showed higher competitive ability when grown in high-density monoculture communities of plants from the same population (intrapopulation competition). In contrast, invasive A. adenophora plants showed lower competitive ability when competing with plants from native populations (intraspecific competition). Our results indicated that in the invasive range A. adenophora has evolved to effectively cope with co-occurring natives and high density environments, contributing to invasion success. Here, we showed the significant effects of competitors, which should be considered carefully when testing the EICA hypothesis.
-
Spatial heterogeneity in soil microbes alters outcomes of plant competition.
Directory of Open Access Journals (Sweden)
Karen C Abbott
Full Text Available Plant species vary greatly in their responsiveness to nutritional soil mutualists, such as mycorrhizal fungi and rhizobia, and this responsiveness is associated with a trade-off in allocation to root structures for resource uptake. As a result, the outcome of plant competition can change with the density of mutualists, with microbe-responsive plant species having high competitive ability when mutualists are abundant and non-responsive plants having high competitive ability with low densities of mutualists. When responsive plant species also allow mutualists to grow to greater densities, changes in mutualist density can generate a positive feedback, reinforcing an initial advantage to either plant type. We study a model of mutualist-mediated competition to understand outcomes of plant-plant interactions within a patchy environment. We find that a microbe-responsive plant can exclude a non-responsive plant from some initial conditions, but it must do so across the landscape including in the microbe-free areas where it is a poorer competitor. Otherwise, the non-responsive plant will persist in both mutualist-free and mutualist-rich regions. We apply our general findings to two different biological scenarios: invasion of a non-responsive plant into an established microbe-responsive native population, and successional replacement of non-responders by microbe-responsive species. We find that resistance to invasion is greatest when seed dispersal by the native plant is modest and dispersal by the invader is greater. Nonetheless, a native plant that relies on microbial mutualists for competitive dominance may be particularly vulnerable to invasion because any disturbance that temporarily reduces its density or that of the mutualist creates a window for a non-responsive invader to establish dominance. We further find that the positive feedbacks from associations with beneficial soil microbes create resistance to successional turnover. Our theoretical
-
Spatial heterogeneity in soil microbes alters outcomes of plant competition.
Abbott, Karen C; Karst, Justine; Biederman, Lori A; Borrett, Stuart R; Hastings, Alan; Walsh, Vonda; Bever, James D
2015-01-01
Plant species vary greatly in their responsiveness to nutritional soil mutualists, such as mycorrhizal fungi and rhizobia, and this responsiveness is associated with a trade-off in allocation to root structures for resource uptake. As a result, the outcome of plant competition can change with the density of mutualists, with microbe-responsive plant species having high competitive ability when mutualists are abundant and non-responsive plants having high competitive ability with low densities of mutualists. When responsive plant species also allow mutualists to grow to greater densities, changes in mutualist density can generate a positive feedback, reinforcing an initial advantage to either plant type. We study a model of mutualist-mediated competition to understand outcomes of plant-plant interactions within a patchy environment. We find that a microbe-responsive plant can exclude a non-responsive plant from some initial conditions, but it must do so across the landscape including in the microbe-free areas where it is a poorer competitor. Otherwise, the non-responsive plant will persist in both mutualist-free and mutualist-rich regions. We apply our general findings to two different biological scenarios: invasion of a non-responsive plant into an established microbe-responsive native population, and successional replacement of non-responders by microbe-responsive species. We find that resistance to invasion is greatest when seed dispersal by the native plant is modest and dispersal by the invader is greater. Nonetheless, a native plant that relies on microbial mutualists for competitive dominance may be particularly vulnerable to invasion because any disturbance that temporarily reduces its density or that of the mutualist creates a window for a non-responsive invader to establish dominance. We further find that the positive feedbacks from associations with beneficial soil microbes create resistance to successional turnover. Our theoretical results constitute an
-
Measuring competition in plant communities where it is difficult to distinguish individual plants
DEFF Research Database (Denmark)
Damgaard, Christian
2011-01-01
A novel method for measuring plant-plant interactions in undisturbed semi-natural and natural plant communities where it is difficult to distinguish individual plants is discussed. It is assumed that the ecological success of the different plant species in the plant community may be adequately...... measured by plant cover and vertical density (a measure that is correlated to the 3-dimensional space occupancy and biomass). Both plant cover and vertical density are measured in a standard pin-point analysis in the beginning and at the end of the growing season. In the outlined competition model....... The method allows direct measurements of the competitive effects of neighbouringzplants on plant performance and the estimation of parameters that describe the ecological processes of plantplant interactions during the growing season as well as the process of survival and recruitment between growing seasons...
-
Interactive effects of herbivory and competition intensity determine invasive plant performance.
Huang, Wei; Carrillo, Juli; Ding, Jianqing; Siemann, Evan
2012-10-01
Herbivory can reduce plant fitness, and its effects can be increased by competition. Though numerous studies have examined the joint effects of herbivores and competitors on plant performance, these interactive effects are seldom considered in the context of plant invasions. Here, we examined variation in plant performance within a competitive environment in response to both specialist and generalist herbivores using Chinese tallow as a model species. We combined tallow plants from native and invasive populations to form all possible pairwise combinations, and designated invasive populations as stronger neighbours and native populations as weaker neighbours. We found that when no herbivory was imposed, invasive populations always had higher total biomass than natives, regardless of their neighbours, which is consistent with our assumption of increased competitive ability. Defoliation by either generalist or specialist herbivores suppressed plant growth but the effects of specialists were generally stronger for invasive populations. Invasive populations had their lowest biomass when fed upon by specialists while simultaneously competing with stronger neighbours. The root/shoot ratios of invasive populations were lower than those of native populations under almost all conditions, and invasive plants were taller than native plants overall, especially when herbivores were present, suggesting that invasive populations may adopt an "aboveground first" strategy to cope with herbivory and competition. These results suggest that release from herbivores, especially specialists, improves an invader's performance and helps to increase its competitive ability. Therefore, increasing interspecific competition intensity by planting a stronger neighbour while simultaneously releasing a specialist herbivore may be an especially effective method of managing invasive plants.
-
Cost-competitive, inherently safe LFMBR pool plant
International Nuclear Information System (INIS)
McDonald, J.S.; Brunings, J.E.; Chang, Y.I.; Hren, R.R.; Seidensticker, R.W.
1984-01-01
The Cost-Competitive, Inherently Safe LMFBR Pool Plant design was prepared in GFY 1983 under a DOE-sponsored program. This plant design was developed as a joint effort by Rockwell International and the Argonne National Laboratory with major contributions from the Bechtel Group, Inc.; Combustion engineering, Inc.; the Chicago Bridge and Iron Company; and the General Electric Company. Using current LMFBR technology, many innovative features were developed and incorporated into the design to meet the ultimate objectives of the Breeder Program, i.e., energy costs competitive with LWRs and inherent safety features to maintain the plant in a safe condition following assumed accidents without requiring operator action. This paper provides a description of the principal features that were incorporated into the design to achieve low cost and inherent safety
-
Competition for light and nutrients in layered communities of aquatic plants.
van Gerven, Luuk P A; de Klein, Jeroen J M; Gerla, Daan J; Kooi, Bob W; Kuiper, Jan J; Mooij, Wolf M
2015-07-01
Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that at high supply of light and nutrients, floating plants always dominate due to their primacy for light, even when submerged plants have lower minimal resource requirements. The model also shows that floating-plant dominance cannot be an alternative stable state in light-limited environments but only in nutrient-limited environments, depending on the plants' resource consumption traits. Compared to unlayered communities, the asymmetry in competition for light-coincident with symmetry in competition for nutrients-leads to fundamentally different results: competition outcomes can no longer be predicted from species traits such as minimal resource requirements ([Formula: see text] rule) and resource consumption. Also, the same two species can, depending on the environment, coexist or be alternative stable states. When applied to two common plant species in temperate regions, both the model and field data suggest that floating-plant dominance is unlikely to be an alternative stable state.
-
Competitive positioning of power generation plants in a deregulated market
International Nuclear Information System (INIS)
Stephens, J.
1998-01-01
As industrialized countries deregulate their electric power industries, there is a fundamental shift from guaranteed cost recovery to open market competition on a deregulated grid. Utilities generally competitively bid into a power exchange where the lowest cost power providers are dispatched first. Therefore, the competitiveness of utilities determines their profitability. This commercial structure compels power generators to seek out ways of improving their equipment and plant performance. The inevitability of this trend is demonstrated by a look at the installed base in the US where the move toward deregulation is gaining momentum. More than half of the generating plants in the US are over 20 years old. The average thermal efficiency nation-wide is 33%. In contrast, contemporary coal-and gas-fired plants can operate at efficiency levels up to 45 percent and 55 to 60%, respectfully. With new facilities coming on-line, existing plants will need to make improvements to be dispatched. When deregulation fully envelopes the US market, utilities will not all fit into one pattern; their strategies and actions will depend on a multiple set of factors. Their success will be based on their ability to change landscapes from guaranteed cost recovery to competitive bidding. This paper discussers technical and commercial options available to power producers to improve their competitive positions in a deregulated market as well as software for determining the competitiveness of specific power plants and the location-based market prices of electricity. Examples of the application of alternatives will be cited along with expected payback and impact on cents per kilowatt-hour production costs
-
Chapter 8. Controlling plant competition
Stephen B. Monsen
2004-01-01
Generally, range or wildlife habitat improvement projects seek to achieve desirable plants through the elimination or replacement of undesirable species or both. Control measures are thus designed to: (1) reduce the competitive effects of existing species (Evans and Young 1987a,b; Robertson and Pearse 1945), (2) allow the establishment of seeded species (Harper and...
-
Reduced plant competition among kin can be explained by Jensen's inequality.
Simonsen, Anna K; Chow, Theresa; Stinchcombe, John R
2014-12-01
Plants often compete with closely related individuals due to limited dispersal, leading to two commonly invoked predictions on competitive outcomes. Kin selection, from evolutionary theory, predicts that competition between relatives will likely be weaker. The niche partitioning hypothesis, from ecological theory, predicts that competition between close relatives will likely be stronger. We tested for evidence consistent with either of these predictions by growing an annual legume in kin and nonkin groups in the greenhouse. We grew plant groups in treatments of symbiotic nitrogen fixing bacteria differing in strain identity and composition to determine if differences in the microbial environment can facilitate or obscure plant competition patterns consistent with kin selection or niche partitioning. Nonkin groups had lower fitness than expected, based on fitness estimates of the same genotypes grown among kin. Higher fitness among kin groups was observed in mixtures of N-fixing bacteria strains compared to single inoculations of bacteria strains present in the soil, which increased fitness differences between kin and nonkin groups. Lower fitness in nonkin groups was likely caused by increased competitive asymmetry in nonkin groups due to genetic differences in plant size combined with saturating relationships with plant size and fitness- i.e. Jensen's inequality. Our study suggests that microbial soil symbionts alter competitive dynamics among kin and nonkin. Our study also suggests that kin groups can have higher fitness, as predicted by kin selection theory, through a commonly heritable trait (plant size), without requiring kin recognition mechanisms.
-
How light competition between plants affects trait optimization and vegetation-atmosphere feedbacks
van Loon, M.P.
2016-01-01
How plants respond to climate change is of major concern, as plants will strongly impact future ecosystem functioning, food production and climate. Competition between plants for resources is an important selective force. As a result competition through natural selection determines vegetation
-
Competitiveness of biomass-fueled electrical power plants.
Bruce A. McCarl; Darius M. Adams; Ralph J. Alig; John T. Chmelik
2000-01-01
One way countries like the United States can comply with suggested rollbacks in greenhouse gas emissions is by employing power plants fueled with biomass. We examine the competitiveness of biomass-based fuel for electrical power as opposed to coal using a mathematical programming structure. We consider fueling power plants from milling residues, whole trees, logging...
-
How light competition between plants affects their response to climate change.
van Loon, Marloes P; Schieving, Feike; Rietkerk, Max; Dekker, Stefan C; Sterck, Frank; Anten, Niels P R
2014-09-01
How plants respond to climate change is of major concern, as plants will strongly impact future ecosystem functioning, food production and climate. Here, we investigated how vegetation structure and functioning may be influenced by predicted increases in annual temperatures and atmospheric CO2 concentration, and modeled the extent to which local plant-plant interactions may modify these effects. A canopy model was developed, which calculates photosynthesis as a function of light, nitrogen, temperature, CO2 and water availability, and considers different degrees of light competition between neighboring plants through canopy mixing; soybean (Glycine max) was used as a reference system. The model predicts increased net photosynthesis and reduced stomatal conductance and transpiration under atmospheric CO2 increase. When CO2 elevation is combined with warming, photosynthesis is increased more, but transpiration is reduced less. Intriguingly, when competition is considered, the optimal response shifts to producing larger leaf areas, but with lower stomatal conductance and associated vegetation transpiration than when competition is not considered. Furthermore, only when competition is considered are the predicted effects of elevated CO2 on leaf area index (LAI) well within the range of observed effects obtained by Free air CO2 enrichment (FACE) experiments. Together, our results illustrate how competition between plants may modify vegetation responses to climate change. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.
-
The Use of Canopy Models to Analyze Light Competition Among Plants
Anten, N.P.R.; Bastiaans, L.
2016-01-01
Competition for light among plants is an important factor determining plant trait evolution and community dynamics. It may also strongly modulate crop production. Canopy models provide a useful means of analyzing light competition. This use however entails that these models take account of the
-
Host plant quality mediates competition between arbuscular mycorrhizal fungi
Knegt, B.; Jansa, J.; Franken, O.; Engelmoer, D.J.P.; Werner, G.D.A.; Bücking, H.; Kiers, E.T.
2016-01-01
Arbuscular mycorrhizal fungi exchange soil nutrients for carbon from plant hosts. Empirical works suggests that hosts may selectively provide resources to different fungal species, ultimately affecting fungal competition. However, fungal competition may also be mediated by colonization strategies of
-
Evidence for competition between carnivorous plants and spiders.
Jennings, David E; Krupa, James J; Raffel, Thomas R; Rohr, Jason R
2010-10-07
Several studies have demonstrated that competition between disparate taxa can be important in determining community structure, yet surprisingly, to our knowledge, no quantitative studies have been conducted on competition between carnivorous plants and animals. To examine potential competition between these taxa, we studied dietary and microhabitat overlap between pink sundews (Drosera capillaris) and wolf spiders (Lycosidae) in the field, and conducted a laboratory experiment examining the effects of wolf spiders on sundew fitness. In the field, we found that sundews and spiders had a high dietary overlap with each other and with the available arthropod prey. Associations between sundews and spiders depended on spatial scale: both sundews and spiders were found more frequently in quadrats with more abundant prey, but within quadrats, spiders constructed larger webs and located them further away from sundews as the total sundew trapping area increased, presumably to reduce competition. Spiders also constructed larger webs when fewer prey were available. In the laboratory, our experiment revealed that spiders can significantly reduce sundew fitness. Our findings suggest that members of the plant and animal kingdoms can and do compete.
-
Root plasticity buffers competition among plants: theory meets experimental data.
Schiffers, Katja; Tielbörger, Katja; Tietjen, Britta; Jeltsch, Florian
2011-03-01
Morphological plasticity is a striking characteristic of plants in natural communities. In the context of foraging behavior particularly, root plasticity has been documented for numerous species. Root plasticity is known to mitigate competitive interactions by reducing the overlap of the individuals' rhizospheres. But despite its obvious effect on resource acquisition, plasticity has been generally neglected in previous empirical and theoretical studies estimating interaction intensity among plants. In this study, we developed a semi-mechanistic model that addresses this shortcoming by introducing the idea of compensatory growth into the classical-zone-of influence (ZOI) and field-of-neighborhood (FON) approaches. The model parameters describing the belowground plastic sphere of influence (PSI) were parameterized using data from an accompanying field experiment. Measurements of the uptake of a stable nutrient analogue at distinct distances to the neighboring plants showed that the study species responded plastically to belowground competition by avoiding overlap of individuals' rhizospheres. An unexpected finding was that the sphere of influence of the study species Bromus hordeaceus could be best described by a unimodal function of distance to the plant's center and not with a continuously decreasing function as commonly assumed. We employed the parameterized model to investigate the interplay between plasticity and two other important factors determining the intensity of competitive interactions: overall plant density and the distribution of individuals in space. The simulation results confirm that the reduction of competition intensity due to morphological plasticity strongly depends on the spatial structure of the competitive environment. We advocate the use of semi-mechanistic simulations that explicitly consider morphological plasticity to improve our mechanistic understanding of plant interactions.
-
Competition between Plant-Populations with Different Rooting Depths. 1. Theoretical Considerations
Berendse, F.
1979-01-01
As an extension of De Wit's competition theory a theoretical description has been developed of competition between plant populations with different rooting depths. This model shows that in mixtures of plants with different rooting depths the value of the Relative Yield Total can be expected to
-
Competition Between Plant Populations with Different Rooting Depths I. Theoretical Considerations
Berendse, Frank
1979-01-01
As an extension of De Wit’s competition theory a theoretical description has been developed of competition between plant populations with different rooting depths. This model shows that in mixtures of plants with different rooting depths the value of the Relative Yield Total can be expected to
-
The competitiveness of medicinal plants in Central Java Indonesia
Riptanti, E. W.; Qonita, R. A.; Fajarningsih, R. U.
2018-03-01
Indonesia hold a potential opportunity to be a pharmaceutical production country. In the other side, Indonesia facing agriculture product and market competition internationally and domestically. Improving competitiveness of specific products are aimed to hit the export market and also to be able to compete with import products in domestic market. Considering Indonesian market opportunity, therefore we perform this study aiming to examine the competitiveness of medicinal plants in Central Java area. The basic method applied in this study was descriptive and data sources are primary and secondary data. Data were analyzed using Revealed Comparative Advantage (RCA) and Trade Specialization Index (TSI) approaches. According to the study, we reveal that medicinal plant commodities in Central Java province have average score 8.52, indicating a strong comparative advantage in global markets, while the commodities appear to have average score of 0.97 at 0 to 1 range, representing a strong competitiveness. Those results are attributed to natural and environmental condition, as well as high demand of global market. This competitiveness will encourage traditional/modern medicinal industries in global market.
-
Growth rates of rhizosphere microorganisms depend on competitive abilities of plants for nitrogen
Blagodatskaya, Evgenia; Littschwager, Johanna; Lauerer, Marianna; Kuzyakov, Yakov
2010-05-01
Rhizosphere - one of the most important ‘hot spots' in soil - is characterized not only by accelerated turnover of microbial biomass and nutrients but also by strong intra- and inter-specific competition. Intra-specific competition occurs between individual plants of the same species, while inter-specific competition can occur both at population level (plant species-specific, microbial species-specific interactions) and at community level (plant - microbial interactions). Such plant - microbial interactions are mainly governed by competition for available N sources, since N is one of the main growth limiting nutrients in natural ecosystems. Functional structure and activity of microbial community in rhizosphere is not uniform and is dependent on quantity and quality of root exudates which are plant specific. It is still unclear how microbial growth and turnover in the rhizosphere are dependent on the features and competitive abilities of plants for N. Depending on C and N availability, acceleration and even retardation of microbial activity and carbon mineralization can be expected in the rhizosphere of plants with high competitive abilities for N. We hypothesized slower microbial growth rates in the rhizosphere of plants with smaller roots, as they usually produce less exudates compared to plants with small shoot-to-root ratio. As the first hypothesis is based solely on C availability, we also expected the greater effect of N availability on microbial growth in rhizosphere of plants with smaller root mass. These hypothesis were tested for two plant species of strawberry: Fragaria vesca L. (native species), and Duchesnea indica (Andrews) Focke (an invasive plant in central Europe) growing in intraspecific and interspecific competition. Microbial biomass and the kinetic parameters of microbial growth in the rhizosphere were estimated by dynamics of CO2 emission from the soil amended with glucose and nutrients. Specific growth rate (µ) of soil microorganisms was
-
Apparent competition with an invasive plant hastens the extinction of an endangered lupine.
Dangremond, Emily M; Pardini, Eleanor A; Knight, Tiffany M
2010-08-01
Invasive plants may compete with native plants by increasing the pressure of native consumers, a mechanism known as "apparent competition." Apparent competition can be as strong as or stronger than direct competition, but the role of apparent competition has rarely been examined in biological invasions. We used four years of demographic data and seed-removal experiments to determine if introduced grasses caused elevated levels of seed consumption on native plant species in a coastal dune system in California, USA. We show that the endangered, coastal dune plant Lupinus tidestromii experiences high levels of pre-dispersal seed consumption by the native rodent Peromyscus maniculatus due to its proximity to the invasive grass, Ammophila arenaria. We use stage-structured, stochastic population models to project that two of three study populations will decline toward extinction under ambient levels of consumption. For one of these declining populations, a relatively small decrease in consumption pressure should allow for persistence. We show that apparent competition with an invasive species significantly decreases the population growth rate and persistence of a native species. We expect that apparent competition is an important mechanism in other ecosystems because invasive plants often change habitat structure and plant-consumer interactions. Possible implications of the apparent-competition mechanism include selective extinction of species preferred by seed consumers in the presence of an invasive species and biological homogenization of communities toward non-preferred native plant species.
-
Hendriks, Marloes; Ravenek, Janneke M; Smit-Tiekstra, Annemiek E; van der Paauw, Jan Willem; de Caluwe, Hannie; van der Putten, Wim H; de Kroon, Hans; Mommer, Liesje
2015-08-01
Plant-soil feedback is receiving increasing interest as a factor influencing plant competition and species coexistence in grasslands. However, we do not know how spatial distribution of plant-soil feedback affects plant below-ground interactions. We investigated the way in which spatial heterogeneity of soil biota affects competitive interactions in grassland plant species. We performed a pairwise competition experiment combined with heterogeneous distribution of soil biota using four grassland plant species and their soil biota. Patches were applied as quadrants of 'own' and 'foreign' soils from all plant species in all pairwise combinations. To evaluate interspecific root responses, species-specific root biomass was quantified using real-time PCR. All plant species suffered negative soil feedback, but strength was species-specific, reflected by a decrease in root growth in own compared with foreign soil. Reduction in root growth in own patches by the superior plant competitor provided opportunities for inferior competitors to increase root biomass in these patches. These patterns did not cascade into above-ground effects during our experiment. We show that root distributions can be determined by spatial heterogeneity of soil biota, affecting plant below-ground competitive interactions. Thus, spatial heterogeneity of soil biota may contribute to plant species coexistence in species-rich grasslands. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
-
Competition increases sensitivity of wheat (Triticum aestivum) to biotic plant-soil feedback.
Hol, W H Gera; de Boer, Wietse; ten Hooven, Freddy; van der Putten, Wim H
2013-01-01
Plant-soil feedback (PSF) and plant competition play an important role in structuring vegetation composition, but their interaction remains unclear. Recent studies suggest that competing plants could dilute pathogenic effects, whereas the standing view is that competition may increase the sensitivity of the focal plant to PSF. In agro-ecosystems each of these two options would yield contrasting outcomes: reduced versus enhanced effects of weeds on crop biomass production. To test the effect of competition on sensitivity to PSF, we grew Triticum aestivum (Common wheat) with and without competition from a weed community composed of Vicia villosa, Chenopodium album and Myosotis arvensis. Plants were grown in sterilized soil, with or without living field inoculum from 4 farms in the UK. In the conditioning phase, field inocula had both positive and negative effects on T. aestivum shoot biomass, depending on farm. In the feedback phase the differences between shoot biomass in T. aestivum monoculture on non-inoculated and inoculated soils had mostly disappeared. However, T. aestivum plants growing in mixtures in the feedback phase were larger on non-inoculated soil than on inoculated soil. Hence, T. aestivum was more sensitive to competition when the field soil biota was present. This was supported by the statistically significant negative correlation between shoot biomass of weeds and T. aestivum, which was absent on sterilized soil. In conclusion, competition in cereal crop-weed systems appears to increase cereal crop sensitivity to soil biota.
-
Strategies for competitive nuclear power plants
International Nuclear Information System (INIS)
1999-11-01
This technical publication on competitive strategies for nuclear power plants (NPPs) is part of an ongoing project on management of NPP operations in a competitive environment. The overall objective of this project is to assist the management of operating organizations and NPPs in identifying and implementing appropriate measures to remain competitive in a rapidly changing business environment. Other documents that have been written on this topic have focused on how the environment in which NPPs operate is changing. This report instead focuses on strategies and techniques that operating organization and NPP managers can use to succeed in this environment. Of particular note is ongoing OECD/NEA work to describe the environment for nuclear power in competitive electricity markets. The main objective of the OECD/NEA study is to review the impacts of increasing market competition on the nuclear power sectors in OECD Member countries. The OECD/NEA study is identifying various nuclear aspects which have to be considered in relation to the regulatory reform of the electricity sector in OECD Member States. The OECD/NEA work was co-ordinated with the development of this IAEA report; staff members from the two organizations participated in the development and review of the associated documents. Thus, the strategies and techniques identified in this report are consistent with the impacts of increasing market competition identified in the OECD/NEA study
-
Joshi, Srijana; Gruntman, Michal; Bilton, Mark; Seifan, Merav; Tielbörger, Katja
2014-01-01
Background and Aims A common hypothesis to explain plants' invasive success is that release from natural enemies in the introduced range selects for reduced allocation to resistance traits and a subsequent increase in resources available for growth and competitive ability (evolution of increased competitive ability, EICA). However, studies that have investigated this hypothesis have been incomplete as they either did not test for all aspects of competitive ability or did not select appropriate competitors. Methods Here, the prediction of increased competitive ability was examined with the invasive plant Lythrum salicaria (purple loosestrife) in a set of common-garden experiments that addressed these aspects by carefully distinguishing between competitive effect and response of invasive and native plants, and by using both intraspecific and interspecific competition settings with a highly vigorous neighbour, Urtica dioica (stinging nettle), which occurs in both ranges. Key Results While the intraspecific competition results showed no differences in competitive effect or response between native and invasive plants, the interspecific competition experiment revealed greater competitive response and effect of invasive plants in both biomass and seed production. Conclusions The use of both intra- and interspecific competition experiments in this study revealed opposing results. While the first experiment refutes the EICA hypothesis, the second shows strong support for it, suggesting evolutionarily increased competitive ability in invasive populations of L. salicaria. It is suggested that the use of naturally co-occurring heterospecifics, rather than conspecifics, may provide a better evaluation of the possible evolutionary shift towards greater competitive ability. PMID:25301818
-
de Vries, Jorad; Poelman, Erik H; Anten, Niels; Evers, Jochem B
2018-01-24
Plants usually compete with neighbouring plants for resources such as light as well as defend themselves against herbivorous insects. This requires investment of limiting resources, resulting in optimal resource distribution patterns and trade-offs between growth- and defence-related traits. A plant's competitive success is determined by the spatial distribution of its resources in the canopy. The spatial distribution of herbivory in the canopy in turn differs between herbivore species as the level of herbivore specialization determines their response to the distribution of resources and defences in the canopy. Here, we investigated to what extent competition for light affects plant susceptibility to herbivores with different feeding preferences. To quantify interactions between herbivory and competition, we developed and evaluated a 3-D spatially explicit functional-structural plant model for Brassica nigra that mechanistically simulates competition in a dynamic light environment, and also explicitly models leaf area removal by herbivores with different feeding preferences. With this novel approach, we can quantitatively explore the extent to which herbivore feeding location and light competition interact in their effect on plant performance. Our results indicate that there is indeed a strong interaction between levels of plant-plant competition and herbivore feeding preference. When plants did not compete, herbivory had relatively small effects irrespective of feeding preference. Conversely, when plants competed, herbivores with a preference for young leaves had a strong negative effect on the competitiveness and subsequent performance of the plant, whereas herbivores with a preference for old leaves did not. Our study predicts how plant susceptibility to herbivory depends on the composition of the herbivore community and the level of plant competition, and highlights the importance of considering the full range of dynamics in plant-plant-herbivore interactions
-
Lauren P. Waller; Ragan M. Callaway; John N. Klironomos; Yvette K. Ortega; John L. Maron
2016-01-01
1. Arbuscular mycorrhizal (AM) fungi can exert a powerful influence on the outcome of plantâplant competition. Since some exotic plants interact differently with soil biota such as AM fungi in their new range, range-based shifts in AM responsiveness could shift competitive interactions between exotic and resident plants, although this remains poorly studied. 2. We...
-
The effect of competition from neighbours on stomatal conductance in lettuce and tomato plants.
Vysotskaya, Lidiya; Wilkinson, Sally; Davies, William J; Arkhipova, Tatyana; Kudoyarova, Guzel
2011-05-01
Competition decreased transpiration from young lettuce plants after 2 days, before any reductions in leaf area became apparent, and stomatal conductance (g(s) ) of lettuce and tomato plants was also reduced. Stomatal closure was not due to hydraulic signals or competition for nutrients, as soil water content, leaf water status and leaf nitrate concentrations were unaffected by neighbours. Competition-induced stomatal closure was absent in an abscisic acid (ABA)-deficient tomato mutant, flacca, indicating a fundamental involvement of ABA. Although tomato xylem sap ABA concentrations were unaffected by the presence of neighbours, ABA/pH-based stomatal modulation is still likely to underlie the response to competition, as soil and xylem sap alkalization was observed in competing plants. Competition also modulated leaf ethylene production, and treatment of lettuce plants with an ethylene perception inhibitor (1-methylcyclopropene) diminished the difference in g(s) between single and competing plants grown in a controlled environment room, but increased it in plants grown in the greenhouse: ethylene altered the extent of the stomatal response to competition. Effects of competition on g(s) are discussed in terms of the detection of the absence of neighbours: increases in g(s) and carbon fixation may allow faster initial space occupancy within an emerging community/crop. © 2011 Blackwell Publishing Ltd.
-
Raynaud, Xavier; Jaillard, Benoît; Leadley, Paul W
2008-01-01
Plants modify nutrient availability by releasing chemicals in the rhizosphere. This change in availability induced by roots (bioavailability) is known to improve nutrient uptake by individual plants releasing such compounds. Can this bioavailability alter plant competition for nutrients and under what conditions? To address these questions, we have developed a model of nutrient competition between plant species based on mechanistic descriptions of nutrient diffusion, plant exudation, and plant uptake. The model was parameterized using data of the effects of root citrate exudation on phosphorus availability. We performed a sensitivity analysis for key parameters to test the generality of these effects. Our simulations suggest the following. (1) Nutrient uptake depends on the number of roots when nutrients and exudates diffuse little, because individual roots are nearly independent in terms of nutrient supply. In this case, bioavailability profits only species with exudates. (2) Competition for nutrients depends on the spatial arrangement of roots when nutrients diffuse little but exudates diffuse widely. (3) Competition for nutrients depends on the nutrient uptake capacity of roots when nutrients and exudates diffuse widely. In this case, bioavailability profits all species. Mechanisms controlling competition for bioavailable nutrients appear to be diverse and strongly depend on soil, nutrient, and plant properties.
-
Competitive ability, stress tolerance and plant interactions along stress gradients.
Qi, Man; Sun, Tao; Xue, SuFeng; Yang, Wei; Shao, DongDong; Martínez-López, Javier
2018-04-01
Exceptions to the generality of the stress-gradient hypothesis (SGH) may be reconciled by considering species-specific traits and stress tolerance strategies. Studies have tested stress tolerance and competitive ability in mediating interaction outcomes, but few have incorporated this to predict how species interactions shift between competition and facilitation along stress gradients. We used field surveys, salt tolerance and competition experiments to develop a predictive model interspecific interaction shifts across salinity stress gradients. Field survey and greenhouse tolerance tests revealed tradeoffs between stress tolerance and competitive ability. Modeling showed that along salinity gradients, (1) plant interactions shifted from competition to facilitation at high salinities within the physiological limits of salt-intolerant plants, (2) facilitation collapsed when salinity stress exceeded the physiological tolerance of salt-intolerant plants, and (3) neighbor removal experiments overestimate interspecific facilitation by including intraspecific effects. A community-level field experiment, suggested that (1) species interactions are competitive in benign and, facilitative in harsh condition, but fuzzy under medium environmental stress due to niche differences of species and weak stress amelioration, and (2) the SGH works on strong but not weak stress gradients, so SGH confusion arises when it is applied across questionable stress gradients. Our study clarifies how species interactions vary along stress gradients. Moving forward, focusing on SGH applications rather than exceptions on weak or nonexistent gradients would be most productive. © 2018 by the Ecological Society of America.
-
Joshi, Srijana; Gruntman, Michal; Bilton, Mark; Seifan, Merav; Tielbörger, Katja
2014-12-01
A common hypothesis to explain plants' invasive success is that release from natural enemies in the introduced range selects for reduced allocation to resistance traits and a subsequent increase in resources available for growth and competitive ability (evolution of increased competitive ability, EICA). However, studies that have investigated this hypothesis have been incomplete as they either did not test for all aspects of competitive ability or did not select appropriate competitors. Here, the prediction of increased competitive ability was examined with the invasive plant Lythrum salicaria (purple loosestrife) in a set of common-garden experiments that addressed these aspects by carefully distinguishing between competitive effect and response of invasive and native plants, and by using both intraspecific and interspecific competition settings with a highly vigorous neighbour, Urtica dioica (stinging nettle), which occurs in both ranges. While the intraspecific competition results showed no differences in competitive effect or response between native and invasive plants, the interspecific competition experiment revealed greater competitive response and effect of invasive plants in both biomass and seed production. The use of both intra- and interspecific competition experiments in this study revealed opposing results. While the first experiment refutes the EICA hypothesis, the second shows strong support for it, suggesting evolutionarily increased competitive ability in invasive populations of L. salicaria. It is suggested that the use of naturally co-occurring heterospecifics, rather than conspecifics, may provide a better evaluation of the possible evolutionary shift towards greater competitive ability. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
-
Interactive effect of herbivory and competition on the invasive plant Mikania micrantha.
Li, Junmin; Xiao, Tao; Zhang, Qiong; Dong, Ming
2013-01-01
A considerable number of host-specific biological control agents fail to control invasive plants in the field, and exploring the mechanism underlying this phenomenon is important and helpful for the management of invasive plants. Herbivory and competition are two of the most common biotic stressors encountered by invasive plants in their recipient communities. We predicted that the antagonistic interactive effect between herbivory and competition would weaken the effect of herbivory on invasive plants and result in the failure of herbivory to control invasive plants. To examine this prediction, thus, we conducted an experiment in which both invasive Mikania micrantha and native Coix lacryma-job i were grown together and subjected to herbivory-mimicking defoliation. Both defoliation and competition had significantly negative effects on the growth of the invader. However, the negative effect of 75% respective defoliation on the above- and below-ground biomass of Mikania micrantha was alleviated by presence of Coix lacryma-jobi. The negative effect of competition on the above- and below-ground biomass was equally compensated at 25%, 50% and 100% defoliation and overcompensated at 75% defoliation. The interactive effect was antagonistic and dependent on the defoliation intensity, with the maximum effect at 75% defoliation. The antagonistic interaction between defoliation and competition appears to be able to release the invader from competition, thus facilitating the invasiveness of Mikania, a situation that might make herbivory fail to inhibit the growth of invasive Mikania in the invaded community.
-
Uddin, Md Nazim; Robinson, Randall William
2017-12-01
Phragmites australis, a ubiquitous wetland plant, has been considered one of the most invasive species in the world. Allelopathy appears to be one of the invasion mechanisms, however, the effects could be masked by resource competition among target plants. The difficulty of distinguishing allelopathy from resource competition among plants has hindered investigations of the role of phytotoxic allelochemicals in plant communities. This has been addressed via experiments conducted in both the greenhouse and laboratory by growing associated plants, Melaleuca ericifolia, Rumex conglomeratus, and model plant, Lactuca sativa at varying densities with the allelopathic plant, P. australis, its litter and leachate of P. australis litter. This study investigated the potential interacting influences of allelopathy and resource competition on plant growth-density relationships. In greenhouse, the root exudates mediated effects showed the strongest growth inhibition of M. ericifolia at high density whereas litter mediated results revealed increased growth at medium density treatments compared to low and high density. Again, laboratory experiments related to seed germination and seedling growth of L. sativa and R. conglomeratus exhibited phytotoxicity decreased showing positive growth as plant density increased and vice versa. Overall, the differential effects were observed among experiments but maximum individual plant biomass and some other positive effects on plant traits such as root and shoot length, chlorophyll content occurred at an intermediate density. This was attributed to the sharing of the available phytotoxin among plants at high densities which is compatible to density-dependent phytotoxicity model. The results demonstrated that plant-plant interference is the combined effect of allelopathy and resource competition with many other factors but this experimental design, target-neighbor mixed-culture in combination of plant grown at varying densities with varying
-
Predicting coexistence of plants subject to a tolerance-competition trade-off.
Haegeman, Bart; Sari, Tewfik; Etienne, Rampal S
2014-06-01
Ecological trade-offs between species are often invoked to explain species coexistence in ecological communities. However, few mathematical models have been proposed for which coexistence conditions can be characterized explicitly in terms of a trade-off. Here we present a model of a plant community which allows such a characterization. In the model plant species compete for sites where each site has a fixed stress condition. Species differ both in stress tolerance and competitive ability. Stress tolerance is quantified as the fraction of sites with stress conditions low enough to allow establishment. Competitive ability is quantified as the propensity to win the competition for empty sites. We derive the deterministic, discrete-time dynamical system for the species abundances. We prove the conditions under which plant species can coexist in a stable equilibrium. We show that the coexistence conditions can be characterized graphically, clearly illustrating the trade-off between stress tolerance and competitive ability. We compare our model with a recently proposed, continuous-time dynamical system for a tolerance-fecundity trade-off in plant communities, and we show that this model is a special case of the continuous-time version of our model.
-
DEFF Research Database (Denmark)
Ransijn, Johannes; Damgaard, Christian; Schmidt, Inger K
2015-01-01
Plant community patterns in space and time may be explained by the interactions between competing plant species. The presented study investigates this in a nutrient and species poor ecosystem. The study presents a methodology for inferring competitive interactions from yearly vegetation inventories...... to predict the community dynamics of C. vulgaris and D. flexuosa. This was compared with the observed plant community structure at 198 Danish dry heathland sites. Interspecific competition will most likely lead to competitive exclusion of D. flexuosa at the observed temporal and spatial scale...... and uses this to assess the outcome of competitive interactions and to predict community patterns and dynamics in a Northwest-European dry heathland. Inferred competitive interactions from five consecutive years of measurements in permanent vegetation frames at a single dry heathland site were used...
-
Gonzales, Emily K; Arcese, Peter
2008-12-01
The dominance of nonnative plants coupled with declines of native plants suggests that competitive displacement drives extinctions, yet empirical examples are rare. Herbivores, however, can alter vegetation structure and reduce diversity when abundant. Herbivores may act on mature, reproductive life stages whereas some of the strongest competitive effects might occur at early life stages that are difficult to observe. For example, competition by perennial nonnative grasses can interfere with the establishment of native seeds. We contrasted the effects of ungulate herbivory and competition by neighboring plants on the performance of native plant species at early and established life stages in invaded oak meadows. We recorded growth, survival, and flowering in two native species transplanted as established plants, six native species grown from seed, and five extant lily species as part of two 2 x 2 factorial experiments that manipulated herbivory and competition. Herbivory reduced the performance of nearly all focal native species at early and established life stages, whereas competition had few measurable effects. Our results suggest that herbivory has a greater local influence on native plant species than competition and that reducing herbivore impacts will be required to successfully restore endangered oak meadows where ungulates are now abundant.
-
Zhu, Qing; Riley, William J; Tang, Jinyun
2017-04-01
Terrestrial plants assimilate anthropogenic CO 2 through photosynthesis and synthesizing new tissues. However, sustaining these processes requires plants to compete with microbes for soil nutrients, which therefore calls for an appropriate understanding and modeling of nutrient competition mechanisms in Earth System Models (ESMs). Here, we survey existing plant-microbe competition theories and their implementations in ESMs. We found no consensus regarding the representation of nutrient competition and that observational and theoretical support for current implementations are weak. To reconcile this situation, we applied the Equilibrium Chemistry Approximation (ECA) theory to plant-microbe nitrogen competition in a detailed grassland 15 N tracer study and found that competition theories in current ESMs fail to capture observed patterns and the ECA prediction simplifies the complex nature of nutrient competition and quantitatively matches the 15 N observations. Since plant carbon dynamics are strongly modulated by soil nutrient acquisition, we conclude that (1) predicted nutrient limitation effects on terrestrial carbon accumulation by existing ESMs may be biased and (2) our ECA-based approach may improve predictions by mechanistically representing plant-microbe nutrient competition. © 2016 by the Ecological Society of America.
-
de Vries, Jorad; Poelman, Erik H; Anten, Niels; Evers, Jochem B
2018-01-01
Abstract Background and Aims Plants usually compete with neighbouring plants for resources such as light as well as defend themselves against herbivorous insects. This requires investment of limiting resources, resulting in optimal resource distribution patterns and trade-offs between growth- and defence-related traits. A plant’s competitive success is determined by the spatial distribution of its resources in the canopy. The spatial distribution of herbivory in the canopy in turn differs between herbivore species as the level of herbivore specialization determines their response to the distribution of resources and defences in the canopy. Here, we investigated to what extent competition for light affects plant susceptibility to herbivores with different feeding preferences. Methods To quantify interactions between herbivory and competition, we developed and evaluated a 3-D spatially explicit functional–structural plant model for Brassica nigra that mechanistically simulates competition in a dynamic light environment, and also explicitly models leaf area removal by herbivores with different feeding preferences. With this novel approach, we can quantitatively explore the extent to which herbivore feeding location and light competition interact in their effect on plant performance. Key Results Our results indicate that there is indeed a strong interaction between levels of plant–plant competition and herbivore feeding preference. When plants did not compete, herbivory had relatively small effects irrespective of feeding preference. Conversely, when plants competed, herbivores with a preference for young leaves had a strong negative effect on the competitiveness and subsequent performance of the plant, whereas herbivores with a preference for old leaves did not. Conclusions Our study predicts how plant susceptibility to herbivory depends on the composition of the herbivore community and the level of plant competition, and highlights the importance of considering
-
Evidence for competition and cooperation among climbing plants.
Biernaskie, Jay M
2011-07-07
A plant's best strategy for acquiring resources may often depend on the identity of neighbours. Here, I ask whether plants adjust their strategy to local relatedness: individuals may cooperate (reduce competitiveness) with kin but compete relatively intensely with non-kin. In a greenhouse experiment with Ipomoea hederacea, neighbouring siblings from the same inbred line were relatively uniform in height; groups of mixed lines, however, were increasingly variable as their mean height increased. The reproductive yield of mixed and sibling groups was similar overall, but when adjusted to a common mean height and height inequality, the yield of mixed groups was significantly less. Where this difference in yield was most pronounced (among groups that varied most in height), mixed groups tended to allocate more mass to roots than comparable sibling groups, and overall, mixed groups produced significantly fewer seeds per unit mass of roots. These results suggest that, from the group perspective, non-kin may have wasted resources in below-ground competition at the expense of reproduction; kin groups, on the other hand, displayed the relative efficiency that is expected of reduced competitiveness.
-
Uddin, Md Nazim; Robinson, Randall William
2017-01-01
Background Phragmites australis, a ubiquitous wetland plant, has been considered one of the most invasive species in the world. Allelopathy appears to be one of the invasion mechanisms, however, the effects could be masked by resource competition among target plants. The difficulty of distinguishing allelopathy from resource competition among plants has hindered investigations of the role of phytotoxic allelochemicals in plant communities. This has been addressed via experiments conducted in ...
-
Bongers, Franca J; Pierik, Ronald; Anten, Niels P R; Evers, Jochem B
2017-12-21
Although phenotypic plasticity has been shown to be beneficial for plant competitiveness for light, there is limited knowledge on how variation in these plastic responses plays a role in determining competitiveness. A combination of detailed plant experiments and functional-structural plant (FSP) modelling was used that captures the complex dynamic feedback between the changing plant phenotype and the within-canopy light environment in time and 3-D space. Leaf angle increase (hyponasty) and changes in petiole elongation rates in response to changes in the ratio between red and far-red light, two important shade avoidance responses in Arabidopsis thaliana growing in dense population stands, were chosen as a case study for plant plasticity. Measuring and implementing these responses into an FSP model allowed simulation of plant phenotype as an emergent property of the underlying growth and response mechanisms. Both the experimental and model results showed that substantial differences in competitiveness may arise between genotypes with only marginally different hyponasty or petiole elongation responses, due to the amplification of plant growth differences by small changes in plant phenotype. In addition, this study illustrated that strong competitive responses do not necessarily have to result in a tragedy of the commons; success in competition at the expense of community performance. Together, these findings indicate that selection pressure could probably have played a role in fine-tuning the sensitive shade avoidance responses found in plants. The model approach presented here provides a novel tool to analyse further how natural selection could have acted on the evolution of plastic responses.
-
Kim, Tania N; Underwood, Nora; Inouye, Brian D
2013-08-01
Insect herbivores can affect plant abundance and community composition, and theory suggests that herbivores influence plant communities by altering interspecific interactions among plants. Because the outcome of interspecific interactions is influenced by the per capita competitive ability of plants, density dependence, and intrinsic rates of increase, measuring herbivore effects on all these processes is necessary to understand the mechanisms by which herbivores influence plant communities. We fit alternative competition models to data from a response surface experiment conducted over four years to examine how herbivores affected the outcome of competition between two perennial plants, Solidago altissima and Solanum carolinense. Within a growing season, herbivores reduced S. carolinense plant size but did not affect the size of S. altissima, which exhibited compensatory growth. Across seasons, herbivores did not affect S. carolinense density or biomass but reduced both the density and population growth of S. altissima. The best-fit models indicated that the effects of herbivores varied with year. In some years, herbivores increased the per capita competitive effect of S. altissima on S. carolinense; in other years, herbivores influenced the intrinsic rate of increase of S. altissima. We examined possible herbivore effects on the longer-term outcome of competition (over the time scale of a typical old-field habitat), using simulations based on the best-fit models. In the absence of herbivores, plant coexistence was observed. In the presence of herbivores, S. carolinense was excluded by S. altissima in 72.3% of the simulations. We demonstrate that herbivores can influence the outcome of competition through changes in both per capita competitive effects and intrinsic rates of increase. We discuss the implications of these results for ecological succession and biocontrol.
-
Nuclear Power Plants in a Competitive Electricity Market
International Nuclear Information System (INIS)
Jankauskas, V.
2002-01-01
Electricity demand is growing in the world by an average rate of 3% and, according to the International Energy Agency, is going to keep this pace of growth for the 1st quarter of the 21st century. At the same time, the role of the nuclear in the world energy mix is diminishing, and in 2020 only 9% of the world electricity will be produced at the nuclear plants versus 17% in 2000. The main reasons for the nuclear power diminishing share in the world market are not environmental or safety problems, as one may assume, but technical and economical. Long construction time, high capital cost, huge liabilities connected with the spent nuclear fuel and radioactive waste treatment, storage and final disposal are the main factors restricting the further growth of the nuclear power. Nevertheless, in the liberalized markets (U.K., Germany, Scandinavian countries) nuclear power plants are operating rather successfully. In a short run nuclear plants may become very competitive as they have very low short-run marginal costs, but in the long run they may become very in competitive. The Ignalina NPP plays the dominant ro]e in the Lithuanian electricity market, producing more than 75% of the total domestic electricity. It produces the cheapest electricity in Lithuania, mostly due to its higher availability, than the thermal power plants. The price of electricity sold by Ignalina is also lower as it does not cover all costs connected with the future decommissioning of the plant, spent fuel storage and final disposal. If at least part of this cost were included into the selling price, Ignalina might become highly competitive in a liberalised electricity market. As the Lithuanian Electricity law requires to deregulate electricity. generation prices, these prices should be set by the market. (author)
-
It's about time - a critique of macroecological inferences concerning plant competition
DEFF Research Database (Denmark)
Damgaard, Christian Frølund; Weiner, Jacob
2017-01-01
Several macroecological studies have used static spatial data to evaluate plant competition in natural ecosystems and to investigate its role in plant community dynamics and species assembly. The assumptions on which the inferences are based have not been consistent with ecological knowledge....... Inferences about processes, such as competition, from static data are weak. Macroecology will benefit more from dynamic data, even if limited, than from increasingly sophisticated analyses of static spatial patterns....
-
Dohn, Justin; Augustine, David J; Hanan, Niall P; Ratnam, Jayashree; Sankaran, Mahesh
2017-02-01
The majority of research on savanna vegetation dynamics has focused on the coexistence of woody and herbaceous vegetation. Interactions among woody plants in savannas are relatively poorly understood. We present data from a 10-yr longitudinal study of spatially explicit growth patterns of woody vegetation in an East African savanna following exclusion of large herbivores and in the absence of fire. We examined plant spatial patterns and quantified the degree of competition among woody individuals. Woody plants in this semiarid savanna exhibit strongly clumped spatial distributions at scales of 1-5 m. However, analysis of woody plant growth rates relative to their conspecific and heterospecific neighbors revealed evidence for strong competitive interactions at neighborhood scales of up to 5 m for most woody plant species. Thus, woody plants were aggregated in clumps despite significantly decreased growth rates in close proximity to neighbors, indicating that the spatial distribution of woody plants in this region depends on dispersal and establishment processes rather than on competitive, density-dependent mortality. However, our documentation of suppressive effects of woody plants on neighbors also suggests a potentially important role for tree-tree competition in controlling vegetation structure and indicates that the balanced-competition hypothesis may contribute to well-known patterns in maximum tree cover across rainfall gradients in Africa. © 2016 by the Ecological Society of America.
-
Competitive interaction in plant populations exposed to supplementary ultraviolet-B radiation
International Nuclear Information System (INIS)
Fox, F.M.; Caldwell, M.M.; Utah State Univ., Logan
1978-01-01
Changes in plant growth and competitive balance between pairs of competing species were documented as a result of supplementary ultraviolet-B radiation (principally in the 290-315 nm waveband) under field conditions. This component of the terrestrial solar spectrum would be intensified if the atmospheric ozone layer were reduced. A method for calculating and statistically analyzing relative crowding coefficients was developed and used to evaluate the competitive status of the species pairs sown in a modified replacement series. The effect of the supplementary UV-B irradiance was generally detrimental to plant growth, and was reflected in decreased leaf area, biomass, height and density as well as changes competitive balance for various species. For some species, interspecific competition apparently accentuated the effect of the UV-B radiation, while more intense intraspecific competition may have had the same effect for other species. A few species when grown in a situation of more severe mutual interspecific competition exhibited enhanced growth under the UV-B radiation treatment. This, however, was usually associated with a detrimental effect of the radiation, on its competitor and thus was likely the result of its improved competitive circumstance rather than a benefical physiological effect of the radiation. (orig.) [de
-
Jing, Y.; Raaijmakers, C.; Kostenko, O.; Kos, M.; Mulder, P.P.J.; Bezemer, T.M.
2015-01-01
Competition and herbivory are two major factors that can influence plant growth and plant defence. Although these two factors are often studied separately, they do not operate independently. We examined how aboveground herbivory by beet armyworm larvae (Spodoptera exigua) and belowground herbivory
-
Directory of Open Access Journals (Sweden)
Carmen B. Rosa
2018-04-01
Full Text Available Photovoltaic (PV power generation is embedded in a globally competitive environment. This characteristic forces PV power plants to perform most processes relevant for their competitiveness with maximum efficiency. From managers’ point of view, the evaluation of solar energy performance from installed plants is justified to indicate their level of organizational competitiveness, which supports the decision-making process. This manuscript purposes a computational tool that graphically presents the level of competitiveness of PV power plants units based on performance indicators. This tool was developed by using the Key Performance Indicators (KPIs concept, which represents a set of measures focusing on the most critical aspects for the success of the organizations. The KPIs encompass four Fundamental Viewpoints (FV: Strategic Alliances, Solar Energy Monitoring, Management and Strategic Processes, and Power Generation Innovations. These four FVs were deployed on 26 Critical Success Factors (CSFs and 39 KPIs. Sequentially, the tool was applied in four solar generation plants, where three presented an organizational competitiveness global level “potentially competitive”. The proposed computational tool allows managers to assess the degree of organization competitiveness as well as aid in prospecting of future scenarios and decision-making.
-
It's About Time: A Critique of Macroecological Inferences Concerning Plant Competition.
Damgaard, Christian; Weiner, Jacob
2017-02-01
Several macroecological studies have used static spatial data to evaluate plant competition in natural ecosystems and to investigate its role in plant community dynamics and species assembly. The assumptions on which the inferences are based have not been consistent with ecological knowledge. Inferences about processes, such as competition, from static data are weak. Macroecology will benefit more from dynamic data, even if limited, than from increasingly sophisticated analyses of static spatial patterns. Copyright © 2016 Elsevier Ltd. All rights reserved.
-
Directory of Open Access Journals (Sweden)
Pu Wang
Full Text Available Spatial heterogeneity in light supply is common in nature. Many studies have examined the effects of heterogeneous light supply on growth, morphology, physiology and biomass allocation of clonal plants, but few have tested those effects on intraspecific competition. In a greenhouse experiment, we grew one (no competition or nine ramets (with intraspecific competition of a stoloniferous clonal plant, Duchesnea indica, in three homogeneous light conditions (high, medium and low light intensity and two heterogeneous ones differing in patch size (large and small patch treatments. The total light in the two heterogeneous treatments was the same as that in the homogeneous medium light treatment. Both decreasing light intensity and intraspecific competition significantly decreased the growth (biomass, number of ramets and total stolon length of D. indica. As compared with the homogeneous medium light treatment, the large patch treatment significantly increased the growth of D. indica without intraspecific competition. However, the growth of D. indica with competition did not differ among the homogeneous medium light, the large and the small patch treatments. Consequently, light heterogeneity significantly increased intraspecific competition intensity, as measured by the decreased log response ratio. These results suggest that spatial heterogeneity in light supply can alter intraspecific interactions of clonal plants.
-
Jing, Jingying; Bezemer, T. Martijn; Van der Putten, Wim H.
2015-01-01
Plant–soil feedback can affect plants that belong to the same (intraspecific feedback) or different species (interspecific feedback). However, little is known about how intra- and interspecific plant–soil feedbacks influence interspecific plant competition. Here, we used plants and soil from
-
Interspecific competition in plants: how well do current methods answer fundamental questions?
Connolly, J; Wayne, P; Bazzaz, F A
2001-02-01
Accurately quantifying and interpreting the processes and outcomes of competition among plants is essential for evaluating theories of plant community organization and evolution. We argue that many current experimental approaches to quantifying competitive interactions introduce size bias, which may significantly impact the quantitative and qualitative conclusions drawn from studies. Size bias generally arises when estimates of competitive ability are erroneously influenced by the initial size of competing individuals. We employ a series of quantitative thought experiments to demonstrate the potential for size bias in analysis of four traditional experimental designs (pairwise, replacement series, additive series, and response surfaces) either when only final measurements are available or when both initial and final measurements are collected. We distinguish three questions relevant to describing competitive interactions: Which species dominates? Which species gains? and How do species affect each other? The choice of experimental design and measurements greatly influences the scope of inference permitted. Conditions under which the latter two questions can give biased information are tabulated. We outline a new approach to characterizing competition that avoids size bias and that improves the concordance between research question and experimental design. The implications of the choice of size metrics used to quantify both the initial state and the responses of elements in interspecific mixtures are discussed. The relevance of size bias in competition studies with organisms other than plants is also discussed.
-
McNutt, David W; Halpern, Stacey L; Barrows, Kahaili; Underwood, Nora
2012-12-01
Tolerance to herbivory (the degree to which plants maintain fitness after damage) is a key component of plant defense, so understanding how natural selection and evolutionary constraints act on tolerance traits is important to general theories of plant-herbivore interactions. These factors may be affected by plant competition, which often interacts with damage to influence trait expression and fitness. However, few studies have manipulated competitor density to examine the evolutionary effects of competition on tolerance. In this study, we tested whether intraspecific competition affects four aspects of the evolution of tolerance to herbivory in the perennial plant Solanum carolinense: phenotypic expression, expression of genetic variation, the adaptive value of tolerance, and costs of tolerance. We manipulated insect damage and intraspecific competition for clonal lines of S. carolinense in a greenhouse experiment, and measured tolerance in terms of sexual and asexual fitness components. Compared to plants growing at low density, plants growing at high density had greater expression of and genetic variation in tolerance, and experienced greater fitness benefits from tolerance when damaged. Tolerance was not costly for plants growing at either density, and only plants growing at low density benefited from tolerance when undamaged, perhaps due to greater intrinsic growth rates of more tolerant genotypes. These results suggest that competition is likely to facilitate the evolution of tolerance in S. carolinense, and perhaps in other plants that regularly experience competition, while spatio-temporal variation in density may maintain genetic variation in tolerance.
-
Dlusskiĭ, G M
2013-01-01
Many species of entomophylous plants have a wide range of pollinators, and the same insects visit flowers of many plants. The competition for pollination leads to decreasing in seed production of competing species. However, there exists a variety of adaptations that allow plants to reduce the intensity of competition. A comparative analysis of pollinators spectra has allowed to designate groups (subcomplexes) of plants with regard to dominance of various groups of pollinators: myiophylous (flies from the superfamily Muscomorha dominate), syphidophylous (flies from the family Syrphidae dominate), psychophylous (butterflies dominate), cantharophylous (beetles dominate), nonspecialized and specialized melittophylous (Apidae, mainly bumblebees, dominate). The belonging of plants to a specific subcomplex is defined mainly by the structure of flowers and inflorescences. Modes of mechanical and attractive isolation are discussed that lead to restriction of pollinators composition. Competition abatement between species with similar spectra of pollinators and belonging to the same subcomplex is achieved mainly by spatial (ecological) and temporal (different timing of flowering) isolation.
-
Manea, Anthony; Leishman, Michelle R
2011-03-01
We hypothesized that the greater competitive ability of invasive exotic plants relative to native plants would increase under elevated CO(2) because they typically have traits that confer the ability for fast growth when resources are not limiting and thus are likely to be more responsive to elevated CO(2). A series of competition experiments under ambient and elevated CO(2) glasshouse conditions were conducted to determine an index of relative competition intensity for 14 native-invasive exotic species-pairs. Traits including specific leaf area, leaf mass ratio, leaf area ratio, relative growth rate, net assimilation rate and root weight ratio were measured. Competitive rankings within species-pairs were not affected by CO(2) concentration: invasive exotic species were more competitive in 9 of the 14 species-pairs and native species were more competitive in the remaining 5 species-pairs, regardless of CO(2) concentration. However, there was a significant interaction between plant type and CO(2) treatment due to reduced competitive response of native species under elevated compared with ambient CO(2) conditions. Native species had significantly lower specific leaf area and leaf area ratio under elevated compared with ambient CO(2). We also compared traits of more-competitive with less-competitive species, regardless of plant type, under both CO(2) treatments. More-competitive species had smaller leaf weight ratio and leaf area ratio, and larger relative growth rate and net assimilation rate under both ambient and elevated CO(2) conditions. These results suggest that growth and allocation traits can be useful predictors of the outcome of competitive interactions under both ambient and elevated CO(2) conditions. Under predicted future atmospheric CO(2) conditions, competitive rankings among species may not change substantially, but the relative success of invasive exotic species may be increased. Thus, under future atmospheric CO(2) conditions, the ecological and
-
Analysis of future nuclear power plants competitiveness with stochastic methods
International Nuclear Information System (INIS)
Feretic, D.; Tomsic, Z.
2004-01-01
To satisfy the increased demand it is necessary to build new electrical power plants, which could in an optimal way meet, the imposed acceptability criteria. The main criteria are potential to supply the required energy, to supply this energy with minimal (or at least acceptable) costs, to satisfy licensing requirements and be acceptable to public. The main competitors for unlimited electricity production in next few decades are fossil power plants (coal and gas) and nuclear power plants. New renewable power plants (solar, wind, biomass) are also important but due to limited energy supply potential and high costs can be only supplement to the main generating units. Large hydropower plans would be competitive under condition of existence of suitable sites for construction of such plants. The paper describes the application of a stochastic method for comparing economic parameters of future electrical power generating systems including conventional and nuclear power plants. The method is applied to establish competitive specific investment costs of future nuclear power plants when compared with combined cycle gas fired units combined with wind electricity generators using best estimated and optimistic input data. The bases for economic comparison of potential options are plant life time levelized electricity generating costs. The purpose is to assess the uncertainty of several key performance and cost of electricity produced in coal fired power plant, gas fired power plant and nuclear power plant developing probability distribution of levelized price of electricity from different Power Plants, cumulative probability of levelized price of electricity for each technology and probability distribution of cost difference between the technologies. The key parameters evaluated include: levelized electrical energy cost USD/kWh,, discount rate, interest rate for credit repayment, rate of expected increase of fuel cost, plant investment cost , fuel cost , constant annual
-
CO2 Price Impacts on Nuclear Power Plant Competitiveness in Croatia
International Nuclear Information System (INIS)
Tomsic, Z.; Pasicko, R.
2010-01-01
Long term power system planning faces growing number of concerns and uncertainties, which is especially true for nuclear power plants due to their high investment costs and financial risk. In order to analyze competitiveness of nuclear power plants and optimize energy mix, existing models are not sufficient anymore and planners need to think differently in order to face these challenges. Croatia will join EU ETS (European Emission Trading Scheme) with accession to EU (probably in 2012). Thus, for Croatian electrical system it is very important to analyze possible impacts of CO 2 emissions. Analysis presented in this paper is done by electricity market simulation model PLEXOS which was used for modelling Croatian electrical system during development of the Croatian Energy Strategy in 2008. Paper analyzes impacts of CO 2 price on competitiveness of nuclear power plant within Croatian power system between 2020 and 2025. Analyzes are focused on how nuclear power plant influences total emission from the power system regarding coal and gas prices, average electricity price regarding CO 2 , coal and gas prices price. Results of this paper are showing that with emissions from Energy strategy development scenario with two new coal power plants (600 MW each) and two new gas power plants (400 MW each) until 2020, Croatia does not meet Kyoto target due to this emissions from power system. On the other side, introduction of nuclear power plants presented in this paper (1000 MW instead of one coal and one gas power plant) means nearly 6.5 Mt CO 2 emissions less annually and gives possibility to achieve Kyoto target (as this reduced amount represents nearly 22 % of Croatian Kyoto target). Results are also showing how increase in CO 2 price is enhancing competitiveness of a nuclear power plant.(author).
-
Enhancing the economic competitiveness of the Olkiluoto Nuclear Power Plants
International Nuclear Information System (INIS)
Paavola, M.
1996-01-01
The two 710 MWe BWRs at Olkiluoto in Finland have been running for the past ten years with a capacity factor of over 90%. The success of these reactors in being competitive with various forms of fossil fuel power production is attributed to a number of key factors. Of these, the most important is that the staff of the utility and contractors and suppliers personnel are well trained, committed and able to learn new things. Strict safety regulations contribute to competitiveness because the good practice required and the need to keep the plant in mint condition lead to fewer production interruptions and to lower operational costs in the long run. Continuous investment in updating the plant is necessary to maintain high productivity throughout its lifetime. A long-term operational plan coupled with carefully prepared maintenance outages and high quality workmanship also helps to ensure good performance. Better fuel designs and high quality have enabled the plant output to be increased while stabilising or reducing fuel costs. Money for waste management has been reserved since the start of plant operation so that economic production can be ensured during the latter part of the plant lifetime. (UK)
-
Weremijewicz, Joanna; Sternberg, Leonel da Silveira Lobo O'Reilly; Janos, David P
2016-10-01
Arbuscular mycorrhizal (AM) fungi interconnect plants in common mycorrhizal networks (CMNs) which can amplify competition among neighbors. Amplified competition might result from the fungi supplying mineral nutrients preferentially to hosts that abundantly provide fixed carbon, as suggested by research with organ-cultured roots. We examined whether CMNs supplied (15) N preferentially to large, nonshaded, whole plants. We conducted an intraspecific target-neighbor pot experiment with Andropogon gerardii and several AM fungi in intact, severed or prevented CMNs. Neighbors were supplied (15) N, and half of the target plants were shaded. Intact CMNs increased target dry weight (DW), intensified competition and increased size inequality. Shading decreased target weight, but shaded plants in intact CMNs had mycorrhizal colonization similar to that of sunlit plants. AM fungi in intact CMNs acquired (15) N from the substrate of neighbors and preferentially allocated it to sunlit, large, target plants. Sunlit, intact CMN, target plants acquired as much as 27% of their nitrogen from the vicinity of their neighbors, but shaded targets did not. These results suggest that AM fungi in CMNs preferentially provide mineral nutrients to those conspecific host individuals best able to provide them with fixed carbon or representing the strongest sinks, thereby potentially amplifying asymmetric competition below ground. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.
-
O'Brien, Michael J; Pugnaire, Francisco I; Armas, Cristina; Rodríguez-Echeverría, Susana; Schöb, Christian
2017-04-01
The stress-gradient hypothesis predicts a higher frequency of facilitative interactions as resource limitation increases. Under severe resource limitation, it has been suggested that facilitation may revert to competition, and identifying the presence as well as determining the magnitude of this shift is important for predicting the effect of climate change on biodiversity and plant community dynamics. In this study, we perform a meta-analysis to compare temporal differences of species diversity and productivity under a nurse plant ( Retama sphaerocarpa ) with varying annual rainfall quantity to test the effect of water limitation on facilitation. Furthermore, we assess spatial differences in the herbaceous community under nurse plants in situ during a year with below-average rainfall. We found evidence that severe rainfall deficit reduced species diversity and plant productivity under nurse plants relative to open areas. Our results indicate that the switch from facilitation to competition in response to rainfall quantity is nonlinear. The magnitude of this switch depended on the aspect around the nurse plant. Hotter south aspects under nurse plants resulted in negative effects on beneficiary species, while the north aspect still showed facilitation. Combined, these results emphasize the importance of spatial heterogeneity under nurse plants for mediating species loss under reduced precipitation, as predicted by future climate change scenarios. However, the decreased water availability expected under climate change will likely reduce overall facilitation and limit the role of nurse plants as refugia, amplifying biodiversity loss.
-
Zhou, Jian; Dong, Bi-Cheng; Alpert, Peter; Li, Hong-Li; Zhang, Ming-Xiang; Lei, Guang-Chun; Yu, Fei-Hai
2012-03-01
Fine-scale, spatial heterogeneity in soil nutrient availability can increase the growth of individual plants, the productivity of plant communities and interspecific competition. If this is due to the ability of plants to concentrate their roots where nutrient levels are high, then nutrient heterogeneity should have little effect on intraspecific competition, especially when there are no genotypic differences between individuals in root plasticity. We tested this hypothesis in a widespread, clonal species in which individual plants are known to respond to nutrient heterogeneity. Plants derived from a single clone of Alternanthera philoxeroides were grown in the greenhouse at low or high density (four or 16 plants per 27·5 × 27·5-cm container) with homogeneous or heterogeneous availability of soil nutrients, keeping total nutrient availability per container constant. After 9 weeks, measurements of size, dry mass and morphology were taken. Plants grew more in the heterogeneous than in the homogeneous treatment, showing that heterogeneity promoted performance; they grew less in the high- than in the low-density treatment, showing that plants competed. There was no interactive effect of nutrient heterogeneity and plant density, supporting the hypothesis that heterogeneity does not affect intraspecific competition in the absence of genotypic differences in plasticity. Treatments did not affect morphological characteristics such as specific leaf area or root/shoot ratio. Results indicate that fine-scale, spatial heterogeneity in the availability of soil nutrients does not increase competition when plants are genetically identical, consistent with the suggestion that effects of heterogeneity on competition depend upon differences in plasticity between individuals. Heterogeneity is only likely to increase the spread of monoclonal, invasive populations such as that of A. philoxeroides in China.
-
Essarioui, Adil; LeBlanc, Nicholas; Kistler, Harold C; Kinkel, Linda L
2017-07-01
Plant community characteristics impact rhizosphere Streptomyces nutrient competition and antagonistic capacities. However, the effects of Streptomyces on, and their responses to, coexisting microorganisms as a function of plant host or plant species richness have received little attention. In this work, we characterized antagonistic activities and nutrient use among Streptomyces and Fusarium from the rhizosphere of Andropogon gerardii (Ag) and Lespedeza capitata (Lc) plants growing in communities of 1 (monoculture) or 16 (polyculture) plant species. Streptomyces from monoculture were more antagonistic against Fusarium than those from polyculture. In contrast, Fusarium isolates from polyculture had greater inhibitory capacities against Streptomyces than isolates from monoculture. Although Fusarium isolates had on average greater niche widths, the collection of Streptomyces isolates in total used a greater diversity of nutrients for growth. Plant richness, but not plant host, influenced the potential for resource competition between the two taxa. Fusarium isolates had greater niche overlap with Streptomyces in monoculture than polyculture, suggesting greater potential for Fusarium to competitively challenge Streptomyces in monoculture plant communities. In contrast, Streptomyces had greater niche overlap with Fusarium in polyculture than monoculture, suggesting that Fusarium experiences greater resource competition with Streptomyces in polyculture than monoculture. These patterns of competitive and inhibitory phenotypes among Streptomyces and Fusarium populations are consistent with selection for Fusarium-antagonistic Streptomyces populations in the presence of strong Fusarium resource competition in plant monocultures. Similarly, these results suggest selection for Streptomyces-inhibitory Fusarium populations in the presence of strong Streptomyces resource competition in more diverse plant communities. Thus, landscape-scale variation in plant species richness may be
-
Simulation of power plant construction in competitive Korean electricity market
International Nuclear Information System (INIS)
Ahn, Nam Sung; Huh, Sung Chul
2001-01-01
This paper describes the forecast of power plant construction in competitive Korean electricity market. In Korea, KEPCO (Korean Electric Power Corporation, fully controlled by government) was responsible for from the production of the electricity to the sale of electricity to customer. However, the generation part is separated from KEPCO and six generation companies were established for whole sale competition from April 1st, 2001. The generation companies consist of five fossil power companies and one nuclear power company. Fossil power companies are schedule to be sold to private companies including foreign investors. Nuclear power company is owned by government. The competition in generation market will start from 2003. ISO (Independence System Operator) will purchase the electricity from the power exchange market. The market price is determined by the SMP (System Marginal Price) which is decided by the balance between demand and supply of electricity in power exchange market. Under this uncertain circumstance, the energy policy planners are interested to the construction of the power plant in the future. These interests are accelerated due to the recent shortage of electricity supply in California. In the competitive market, investors are no longer interested in the investment for the capital intensive, long lead time generating technologies. Large nuclear and coal plants were no longer the top choices. Instead, investors in the competitive market are interested in smaller, more efficient, cheaper, cleaner technologies such as CCGT (Combined Cycle Gas Turbine). Electricity is treated as commodity in the competitive market. The investor's behavior in the commodity market shows that the new investment decision is made when the market price exceeds the sum of capital cost and variable cost of the new facility and the existing facility utilization depends on the marginal cost of the facility. This investor's behavior can be applied to the new investments for the
-
Competition between Plant-Populations with Different Rooting Depths. 2. Pot Experiments
Berendse, F.
1981-01-01
In a previous paper in this series a model was proposed lor the competition between plant populations with different rooting depths. This model predicts that in mixtures of plant populations with different rooting depths the Relative Yield Total will exceed unity. Secondly it predicts that in these
-
Competition for light and nutrients in layered communities of aquatic plants
Van Gerven, Luuk P.A.; de Klein, J.J.M; Gerla, Daan J.; Kooi, B.W.; Kuiper, Jan J.; Mooij, Wolf M.
2015-01-01
Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that at
-
Competition for Light and Nutrients in Layered Communities of Aquatic Plants
van Gerven, L.P.A.; de Klein, J.J.M.; Gerla, D.J.; Kooi, B.W.; Kuiper, J.J.; Mooij, W.M.
2015-01-01
Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that at
-
Competition for light and nutrients in layered communities of aquatic plants
Gerven, van Luuk P.A.; Klein, de Jeroen J.M.; Gerla, Daan J.; Kooi, Bob W.; Kuiper, Jan J.; Mooij, Wolf M.
2015-01-01
Dominance of free-floating plants poses a threat to biodiversity in many freshwater ecosystems. Here we propose a theoretical framework to understand this dominance, by modeling the competition for light and nutrients in a layered community of floating and submerged plants. The model shows that
-
Plant traits related to nitrogen uptake influence plant-microbe competition.
Moreau, Delphine; Pivato, Barbara; Bru, David; Busset, Hugues; Deau, Florence; Faivre, Céline; Matejicek, Annick; Strbik, Florence; Philippot, Laurent; Mougel, Christophe
2015-08-01
Plant species are important drivers of soil microbial communities. However, how plant functional traits are shaping these communities has received less attention though linking plant and microbial traits is crucial for better understanding plant-microbe interactions. Our objective was to determine how plant-microbe interactions were affected by plant traits. Specifically we analyzed how interactions between plant species and microbes involved in nitrogen cycling were affected by plant traits related to 'nitrogen nutrition in interaction with soil nitrogen availability. Eleven plant species, selected along an oligotrophic-nitrophilic gradient, were grown individually in a nitrogen-poor soil with two levels of nitrate availability. Plant traits for both carbon and nitrogen nutrition were measured and the genetic structure and abundance of rhizosphere. microbial communities, in particular the ammonia oxidizer and nitrate reducer guilds, were analyzed. The structure of the bacterial community in the rhizosphere differed significantly between plant species and these differences depended on nitrogen availability. The results suggest that the rate of nitrogen uptake per unit of root biomass and per day is a key plant trait, explaining why the effect of nitrogen availability on the structure of the bacterial community depends on the plant species. We also showed that the abundance of nitrate reducing bacteria always decreased with increasing nitrogen uptake per unit of root biomass per day, indicating that there was competition for nitrate between plants and nitrate reducing bacteria. This study demonstrates that nitrate-reducing microorganisms may be adversely affected by plants with a high nitrogen uptake rate. Our work puts forward the role of traits related to nitrogen in plant-microbe interactions, whereas carbon is commonly considered as the main driver. It also suggests that plant traits related to ecophysiological processes, such as nitrogen uptake rates, are more
-
Resource competition in plant invasions: emerging patterns and research needs
Czech Academy of Sciences Publication Activity Database
Gioria, Margherita; Osborne, B. A.
2014-01-01
Roč. 5, č. 501 (2014), s. 1-21 ISSN 1664-462X Institutional support: RVO:67985939 Keywords : plant invoasions * resource competition * dominance Subject RIV: EF - Botanics Impact factor: 3.948, year: 2014
-
Investigation of ecological constraints influence on competitiveness of nuclear power plants
Marchenko, O.V.; Solomin, S.V.
2015-01-01
The purpose of the present study is to compare economic efficiency of nuclear power plants and plants on fossil fuel for short-term and long-term (until 2050) perspective and further forecasts specification of nuclear power generation development in Russia and in the world on the background of world energy as a whole. Technical and economic indicators of power plants of different types are systematized taking into account their uncertainty margins. Competitiveness of power plants of differ...
-
You, Wenhua; Fan, Shufeng; Yu, Dan; Xie, Dong; Liu, Chunhua
2014-01-01
Many notorious invasive plants are clonal, however, little is known about the different roles of clonal integration effects between invasive and native plants. Here, we hypothesize that clonal integration affect growth, photosynthetic performance, biomass allocation and thus competitive ability of invasive and native clonal plants, and invasive clonal plants benefit from clonal integration more than co-occurring native plants in heterogeneous habitats. To test these hypotheses, two stoloniferous clonal plants, Alternanthera philoxeroides (invasive), Jussiaea repens (native) were studied in China. The apical parts of both species were grown either with or without neighboring vegetation and the basal parts without competitors were in nutrient- rich or -poor habitats, with stolon connections were either severed or kept intact. Competition significantly reduced growth and photosynthetic performance of the apical ramets in both species, but not the biomass of neighboring vegetation. Without competition, clonal integration greatly improved the growth and photosynthetic performance of both species, especially when the basal parts were in nutrient-rich habitats. When grown with neighboring vegetation, growth of J. repens and photosynthetic performance of both species were significantly enhanced by clonal integration with the basal parts in both nutrient-rich and -poor habitats, while growth and relative neighbor effect (RNE) of A. philoxeroides were greatly improved by clonal integration only when the basal parts were in nutrient-rich habitats. Moreover, clonal integration increased A. philoxeroides's biomass allocation to roots without competition, but decreased it with competition, especially when the basal ramets were in nutrient-rich sections. Effects of clonal integration on biomass allocation of J. repens was similar to that of A. philoxeroides but with less significance. These results supported our hypothesis that invasive clonal plants A. philoxeroides benefits
-
Mahmoudi, Reza; Hafezalkotob, Ashkan; Makui, Ahmad
2014-06-01
Pollution and environmental protection in the present century are extremely significant global problems. Power plants as the largest pollution emitting industry have been the cause of a great deal of scientific researches. The fuel or source type used to generate electricity by the power plants plays an important role in the amount of pollution produced. Governments should take visible actions to promote green fuel. These actions are often called the governmental financial interventions that include legislations such as green subsidiaries and taxes. In this paper, by considering the government role in the competition of two power plants, we propose a game theoretical model that will help the government to determine the optimal taxes and subsidies. The numerical examples demonstrate how government could intervene in a competitive market of electricity to achieve the environmental objectives and how power plants maximize their utilities in each energy source. The results also reveal that the government's taxes and subsidiaries effectively influence the selected fuel types of power plants in the competitive market.
-
Jing, Jingying; Bezemer, T. Martijn; Van der Putten, Wim H.
2015-01-01
Plant–soil feedback can affect plants that belong to the same (intraspecific feedback) or different species (interspecific feedback). However, little is known about how intra- and interspecific plant–soil feedbacks influence interspecific plant competition. Here, we used plants and soil from early-stage ex-arable fields to examine how intra- and interspecific plant–soil feedbacks affect the performance of 10 conditioning species and the focal species, Jacobaea vulgaris. Plants were grown alon...
-
J.Stephen Brewer; W. Chase Bailey
2014-01-01
Despite widespread acknowledgment that disturbance favors invasion, a hypothesis that has received little attention is whether non-native invaders have greater competitive effects on native plants in undisturbed habitats than in disturbed habitats. This hypothesis derives from the assumption that competitive interactions are more persistent in habitats that have not...
-
Facelli, Evelina; Smith, Sally E; Facelli, José M; Christophersen, Helle M; Andrew Smith, F
2010-03-01
*We studied the effects of two arbuscular mycorrhizal (AM) fungi, singly or together, on the outcome of competition between a host (tomato cultivar, wild-type (WT)) and a surrogate nonhost (rmc, a mycorrhiza-defective mutant of WT) as influenced by the contributions of the direct and AM phosphorus (P) uptake pathways to plant P. *We grew plants singly or in pairs of the same or different genotypes (inoculated or not) in pots containing a small compartment with (32)P-labelled soil accessible to AM fungal hyphae and determined expression of orthophosphate (P(i)) transporter genes involved in both AM and direct P uptake. *Gigaspora margarita increased WT competitive effects on rmc. WT and rmc inoculated with Glomus intraradices both showed growth depressions, which were mitigated when G. margarita was present. Orthophosphate transporter gene expression and (32)P transfer showed that the AM pathway operated in single inoculated WT, but not in rmc. *Effects of AM fungi on plant competition depended on the relative contributions of AM and direct pathways of P uptake. Glomus intraradices reduced the efficiency of direct uptake in both WT and rmc. The two-fungus combination showed that interactions between fungi are important in determining outcomes of plant competition.
-
Al-Namazi, Ali A; El-Bana, Magdy I; Bonser, Stephen P
2017-04-01
Nurse plant facilitation in stressful environments can produce an environment with relatively low stress under its canopy. These nurse plants may produce the conditions promoting intense competition between coexisting species under the canopy, and canopies may establish stress gradients, where stress increases toward the edge of the canopy. Competition and facilitation on these stress gradients may control species distributions in the communities under canopies. We tested the following predictions: (1) interactions between understory species shift from competition to facilitation in habitats experiencing increasing stress from the center to the edge of canopy of a nurse plant, and (2) species distributions in understory communities are controlled by competitive interactions at the center of canopy, and facilitation at the edge of the canopy. We tested these predictions using a neighbor removal experiment under nurse trees growing in arid environments. Established individuals of each of four of the most common herbaceous species in the understory were used in the experiment. Two species were more frequent in the center of the canopy, and two species were more frequent at the edge of the canopy. Established individuals of each species were subjected to neighbor removal or control treatments in both canopy center and edge habitats. We found a shift from competitive to facilitative interactions from the center to the edge of the canopy. The shift in the effect of neighbors on the target species can help to explain species distributions in these canopies. Canopy-dominant species only perform well in the presence of neighbors in the edge microhabitat. Competition from canopy-dominant species can also limit the performance of edge-dominant species in the canopy microhabitat. The shift from competition to facilitation under nurse plant canopies can structure the understory communities in extremely stressful environments.
-
Developing an economic performance system to enhance nuclear power plant competitiveness
International Nuclear Information System (INIS)
2002-01-01
In 1999 about 16% of the world's electricity was produced by nuclear power, and the total worldwide operating experience of nuclear power plants was over 9200 reactor-years. Some 16 countries are dependent on nuclear power for more than 25% of their electricity generation. In some countries deregulation of the electricity market has either happened or is currently ongoing, while in others it is planned for the future. Nevertheless, many countries are already facing open electricity markets and operating costs are under unprecedented pressure, with competition expected to come soon to the nuclear industry worldwide. To a certain extent, however, the industry has already prepared or is currently preparing to face competition. This report is primarily intended for nuclear power plant and utility managers. It discusses the means and principal issues for the development of the nuclear economic performance international system (NEPIS), which should enhance nuclear power plant competitiveness. The following issues are addressed: The major transformations occurring in the electricity generation industry that require reductions in operations and maintenance costs at nuclear utilities; The methods that nuclear plant management use to identify and justify the economic optimum level of a plant and its use of resources; The value of collecting cost and performance data and the analysis techniques that use that data; The cost data required to be collected; The difficulty of collecting data with existing cost accounting systems; The new cost accounting and collection systems that will be required, The cost effectiveness of the overall process. This report also presents the preliminary results of a pilot project that was established to collect cost data on a few nuclear power plants and was used to verify the adequacy of the definitions and terminology set for NEPIS
-
Effects of clonal fragmentation on intraspecific competition of a stoloniferous floating plant.
Wang, P; Xu, Y-S; Dong, B-C; Xue, W; Yu, F-H
2014-11-01
Disturbance is common and can fragment clones of plants. Clonal fragmentation may affect the density and growth of ramets so that it could alter intraspecific competition. To test this hypothesis, we grew one (low density), five (medium density) or nine (high density) parent ramets of the floating invasive plant Pistia stratiotes in buckets, and newly produced offspring ramets were either severed (with fragmentation) or remained connected to parent ramets (no fragmentation). Increasing density reduced biomass of the whole clone (i.e. parent ramet plus its offspring ramets), showing intense intraspecific competition. Fragmentation decreased biomass of offspring ramets, but increased biomass of parent ramets and the whole clone, suggesting significant resource translocation from parent to offspring ramets when clones were not fragmented. There was no interaction effect of density x fragmentation on biomass of the whole clone, and fragmentation did not affect competition intensity index. We conclude that clonal fragmentation does not alter intraspecific competition between clones of P. stratiotes, but increases biomass production of the whole clone. Thus, fragmentation may contribute to its interspecific competitive ability and invasiveness, and intentional fragmentation should not be recommended as a measure to stop the rapid growth of this invasive species. © 2014 German Botanical Society and The Royal Botanical Society of the Netherlands.
-
Farji-Brener, Alejandro G.; Lescano, María Natalia
2017-11-01
In arid environments, the high availability of sunlight due to the scarcity of trees suggests that plant competition take place mainly belowground for water and nutrients. However, the occurrence of soil disturbances that increase nutrient availability and thereby promote plant growth may enhance shoot competition between neighboring plants. We conducted a greenhouse experiment to evaluate the influence of the enriched soil patches generated by the leaf-cutting ant, Acromyrmex lobicornis, on the performance of the alien forb Carduus thoermeri (Asteraceae) under different intraspecific competition scenarios. Our results showed that substrate type and competition scenario affected mainly aboveground plant growth. As expected, plants growing without neighbors and in nutrient-rich ant refuse dumps showed more aboveground biomass than plants growing with neighbors and in nutrient-poor steppe soils. However, aboveground competition was more intense in nutrient-poor substrates: plants under shoot and full competition growing in the nutrient-rich ant refuse dumps showed higher biomass than those growing on steppe soils. Belowground biomass was similar among focal plants growing under different substrate type. Our results support the traditional view that increments in resource availability reduce competition intensity. Moreover, the fact that seedlings in this sunny habitat mainly compete aboveground illustrates how limiting factors may be scale-dependent and change in importance as plants grow.
-
Weed-crop competition effects on growth and yield of sugarcane planted using two methods
International Nuclear Information System (INIS)
Zafar, M.; Tanveer, A.; Cheema, Z.A.; Ashraf, M.
2010-01-01
Effect of planting techniques and weed-crop competition periods on yield potential of spring planted sugarcane variety HSF-240 was studied at the Ayub Agricultural Research Institute, Faisalabad, Pakistan. The experiment was laid out in RCBD with a split-plot arrangement, with four replications and net plot size of 3.6m x 10m. In the experiment, two planting techniques viz., 60 cm apart rows in flat sowing technique and 120 cm apart rows in trench sowing technique were randomized in main plots. Seven weed-crop competition periods viz., Zero (weed free), weed-crop competition for 45, 60, 75, 90, 105 days after sowing (DAS) and weedy check (full season weed-crop competition) were randomized in sub-plots. Sugarcane sown by trench method exhibited more leaf area index (LAI), average crop growth rate (ACGR) and yield contributing attributes. Trench sowing by yielding 72.22 and 75.08 t ha/sup -1/ stripped cane yields, significantly showed superiority over the flat sowing, which gave 64.13 and 66.04 t ha/sup -1/ stripped cane yields in 2005-06 and 2006- 07, respectively. Generally, there was an increase in weed population and biomass but decrease in leaf area index, crop growth rate and yield components with an increase in weed-crop competition period. A decrease of 10.06, 17.90, 22.42, 28.65, 37.64 and 56.89% in stripped cane yield was observed for weed-crop competition periods of 45, 60, 75, 90, 105 DAS and weedy check as compared with zero competition in 2005-06, respectively. In 2006-07, the respective decrease in stripped cane yield was 9.84, 18.76, 22.92, 27.98, 38.75, and 54.98%. Trench sowing at 1.2 m row spacing proved better sowing technique and 45 DAS was the critical period of weed-crop competition. (author)
-
Czech Academy of Sciences Publication Activity Database
Dostál, Petr
2011-01-01
Roč. 177, č. 5 (2011), s. 655-667 ISSN 0003-0147 R&D Projects: GA ČR GAP504/10/0132 Institutional research plan: CEZ:AV0Z60050516 Keywords : competitive equivalence * invasive plants * phylogenetic similarity Subject RIV: EF - Botanics Impact factor: 4.725, year: 2011
-
Implications of competitive markets for operation and funds flow at nuclear plants
International Nuclear Information System (INIS)
Bright, R.N.; Leigh, R.W.; Mubayi, V.
1997-01-01
The authors employ a detailed electric utility production costing and capacity planning model to examine the use of nuclear power plants under the current (utility-owned) arrangements and under situations which may arise in a competitive market for electric service. The modeling is carried out for a synthetic but realistic power pool based on components of actual utilities in the northeast United States. Under the current arrangements, the costs of nuclear power plant operation are subsumed under capital costs and entered into the open-quotes raw base,close quotes the totality of which determines customer charges. A future competitive environment may be characterized by the absence of a open-quotes rate base,close quotes at least for generation. In this environment, all generation units are in effect independently owned. The authors examine this possibility by estimating the revenue which would flow to nuclear plants at competitive market prices and compare that revenue, to anticipated expenses for fuel, O ampersand M and amortization of capital (where appropriate), and for potential additional expenses such as safety requirements and payments to decommissioning funds. They also incorporate financial relief for the portion of these costs which can be considered open-quotes stranded investmentsclose quotes based on FERC and prospective state regulatory policies. In this competitive environment some nuclear plants may not remain economically viable. Their replacement by newly constructed fossil-fueled units will require substantial capital and lead to increased emissions and fuel use, which are calculated. The authors calculations show that while it may be clearly economically advantageous for individual owners to shut down unviable nuclear capacity, such early retirements may result in significant economic losses to the power pool as a whole
-
Competition for light and water in a coupled soil-plant system
Manoli, Gabriele; Huang, Cheng-Wei; Bonetti, Sara; Domec, Jean-Christophe; Marani, Marco; Katul, Gabriel
2017-10-01
It is generally accepted that resource availability shapes the structure and function of many ecosystems. Within the soil-plant-atmosphere (SPA) system, resource availability fluctuates in space and time whereas access to resources by individuals is further impacted by plant-to-plant competition. Likewise, transport and transformation of resources within an individual plant is governed by numerous interacting biotic and abiotic processes. The work here explores the co-limitations on water losses and carbon uptake within the SPA arising from fluctuating resource availability and competition. In particular, the goal is to unfold the interplay between plant access and competition for water and light, as well as the impact of transport/redistribution processes on leaf-level carbon assimilation and water fluxes within forest stands. A framework is proposed that couples a three-dimensional representation of soil-root exchanges with a one-dimensional description of stem water flow and storage, canopy photosynthesis, and transpiration. The model links soil moisture redistribution, root water uptake, xylem water flow and storage, leaf potential and stomatal conductance as driven by supply and demand for water and carbon. The model is then used to investigate plant drought resilience of overstory-understory trees simultaneously competing for water and light. Simulation results reveal that understory-overstory interactions increase ecosystem resilience to drought (i.e. stand-level carbon assimilation rates and water fluxes can be sustained at lower root-zone soil water potentials). This resilience enhancement originates from reduced transpiration (due to shading) and hydraulic redistribution in soil supporting photosynthesis over prolonged periods of drought. In particular, the presence of different rooting systems generates localized hydraulic redistribution fluxes that sustain understory transpiration through overstory-understory interactions. Such complex SPA dynamics
-
Planted Black Walnut Does Well on Cleared Forest Sites -- if Competition is Controlled
John E. Krajicek
1975-01-01
After seven growing seasons, survival of black walnut seedlings planted in cleared forest openings did not differ by competition control treatments. The trees grew somewhat larger where all competing vegetation was controlled but almost as large where only herbaceous competition was controlled. Controlling only woody vegetation was no better than no control of any...
-
2017-01-01
Plant performance (i.e., fecundity, growth, survival) depends on an individual’s access to space and resources. At the community level, plant performance is reflected in observable vegetation patterning (i.e., spacing distance, density) often controlled by limiting resources. Resource availability is, in turn, strongly dependent on plant patterning mediated by competitive and facilitative plant–plant interactions. Co-occurring competition and facilitation has never been specifically investigated from a hydrodynamic perspective. To address this knowledge gap, and to overcome limitations of field studies, three intermediate-scale laboratory experiments were conducted using a climate-controlled wind tunnel–porous media test facility to simulate the soil–plant–atmosphere continuum. The spacing between two synthetic plants, a design consideration introduced by the authors in a recent publication, was varied between experiments; edaphic and mean atmospheric conditions were held constant. The strength of the above- and belowground plant–plant interactions changed with spacing distance, allowing the creation of a hydrodynamic conceptual model based on established ecological theories. Greatest soil water loss was observed for the experiment with the smallest spacing where competition dominated. Facilitation dominated at the intermediate spacing; little to no interactions were observed for the largest plant spacing. Results suggest that there exists an optimal spacing distance range that lowers plant environmental stress, thus improving plant performance through reduced atmospheric demand and conservation of available soil water. These findings may provide a foundation for improving our understanding of many climatological, ecohydrological, and hydrological problems pertaining to the hydrodynamics of water-limited environments where plant–plant interactions and community self-organization are important. PMID:28807999
-
Yuan, Zhiyou; Liu, Weixing; Niu, Shuli; Wan, Shiqiang
2007-10-01
Numerous studies have examined the effects of climatic factors on the distribution of C(3) and C(4) grasses in various regions throughout the world, but the role of seasonal fluctuations in temperature, precipitation and soil N availability in regulating growth and competition of these two functional types is still not well understood. This report is about the effects of seasonality of soil N availability and competition on plant N dynamics and N-use strategies of one C(3) (Leymus chinensis) and one C(4) (Chloris virgata) grass species. Leymus chinensis and C. virgata, two grass species native to the temperate steppe in northern China, were planted in a monoculture and a mixture under three different N seasonal availabilities: an average model (AM) with N evenly distributed over the growing season; a one-peak model (OM) with more N in summer than in spring and autumn; and a two-peak model (TM) with more N in spring and autumn than in summer. The results showed that the altered N seasonality changed plant N concentration, with the highest value of L. chinensis under the OM treatment and C. virgata under the TM treatment, respectively. N seasonality also affected plant N content, N productivity and N-resorption efficiency and proficiency in both the C(3) and C(4) species. Interspecific competition influenced N-use and resorption efficiency in both the C(3) and C(4) species, with higher N-use and resorption efficiency in the mixture than in monoculture. The C(4) grass had higher N-use efficiency than the C(3) grass due to its higher N productivity, irrespective of the N treatment or competition. The observations suggest that N-use strategies in the C(3) and C(4) species used in the study were closely related to seasonal dynamics of N supply and competition. N seasonality might be involved in the growth and temporal niche separation between C(3) and C(4) species observed in the natural ecosystems.
-
Suwa, Tomomi; Louda, Svata M
2012-06-01
The biotic resistance hypothesis is a dominant paradigm for why some introduced species fail to become invasive in novel environments. However, predictions of this hypothesis require further empirical field tests. Here, we focus on evaluating two biotic factors known to severely limit plants, interspecific competition and insect herbivory, as mechanisms of biotic resistance. We experimentally evaluated the independent and combined effects of three levels of competition by tallgrass prairie vegetation and two levels of herbivory by native insects on seedling regeneration, size, and subsequent flowering of the Eurasian Cirsium vulgare, a known invasive species elsewhere, and compared its responses to those of the ecologically similar and co-occurring native congener C. altissimum. Seedling emergence of C. vulgare was greater than that of C. altissimum, and that emergence was reduced by the highest level of interspecific competition. Insect leaf herbivory was also greater on C. vulgare than on C. altissimum at all levels of competition. Herbivory on seedlings dramatically decreased the proportion of C. vulgare producing flower heads at all competition levels, but especially at the high competition level. Competition and herbivory interacted to significantly decrease plant survival and biomass, especially for C. vulgare. Thus, both competition and herbivory limited regeneration of both thistles, but their effects on seedling emergence, survival, size and subsequent reproduction were greater for C. vulgare than for C. altissimum. These results help explain the unexpectedly low abundance recorded for C. vulgare in western tallgrass prairie, and also provide strong support for the biotic resistance hypothesis.
-
Plant root proliferation in nitrogen-rich patches confers competitive advantage
Robinson, D.; Hodge, A.; Griffiths, B. S.; Fitter, A. H.
1999-01-01
Plants respond strongly to environmental heterogeneity, particularly below ground, where spectacular root proliferations in nutrient-rich patches may occur. Such 'foraging' responses apparently maximize nutrient uptake and are now prominent in plant ecological theory. Proliferations in nitrogen-rich patches are difficult to explain adaptively, however. The high mobility of soil nitrate should limit the contribution of proliferation to N capture. Many experiments on isolated plants show only a weak relation between proliferation and N uptake. We show that N capture is associated strongly with proliferation during interspecific competition for finite, locally available, mixed N sources, precisely the conditions under which N becomes available to plants on generally infertile soils. This explains why N-induced root proliferation is an important resource-capture mechanism in N-limited plant communities and suggests that increasing proliferation by crop breeding or genetic manipulation will have a limited impact on N capture by well-fertilized monocultures.
-
Directory of Open Access Journals (Sweden)
A. Yadavi
2012-06-01
Full Text Available Unsuitable planting and weed competition are the most important factors that greatly reduce the yield of bean. In order to study the effect of planting date on yield and yield components of three white bean cultivars in weed infest and weed free condition a factorial experiment with randomized complete block design and three replications was carried out at Semirom in 2009. The treatments were planting date (May10, May 25 and June 9 and white bean cultivars (Shekofa, Pak and Daneshkade and two levels of weed infestation (weedy and weed free. Results showed that planting date, weed competition and cultivars had significant effects on yield and yield components of white bean. The 30-day delay in planting date reduced the number of pods per plant, seeds per pod, 100 seed weight and biological yield of white bean cultivars, 22.5, 18, 20.1 and 22.5 percent respectively. Also weed competition, reduced the number of seeds per pod, 100 seed weight and biological yield respectively by 13.5, 5.7 and 27.1 percent. Result of planting date and weed competition interaction effects indicated that the weed competition decreased grain yield (53% in third planting date more than others and delay in planting date was companion with increasing weed density and dry weight in flowering stage of bean. Also Shekofa cultivar had highest grain yield (3379 kg/ha at the first planting date and weed free condition.
-
Physiological integration affects growth form and competitive ability in clonal plants
Czech Academy of Sciences Publication Activity Database
Herben, Tomáš
2004-01-01
Roč. 18, - (2004), s. 493-520 ISSN 0269-7653 R&D Projects: GA ČR(CZ) GA206/02/0953 Institutional research plan: CEZ:AV0Z6005908 Keywords : competitive ability * Physiological integration * clonal plants Subject RIV: EF - Botanics Impact factor: 3.215, year: 2004
-
Competitive drivers and international plant configuration strategies: A product level test
Belderbos, R.A.; Sleuwaegen, L.
2005-01-01
We analyze the determinants of the decision to invest abroad and the choice of spatial configurations of overseas plants for 120 Japanese firms active in 36 well-defined electronic product markets. We find that key competitive drivers at the firm and industry levels have a critical impact on the
-
Liao, Zhi-Yong; Zhang, Ru; Barclay, Gregor F.; Feng, Yu-Long
2013-01-01
The evolution of competitive ability of invasive plant species is generally studied in the context of adaptive responses to novel biotic environments (enemy release) in introduced ranges. However, invasive plants may also respond to novel abiotic environments. Here we studied differences in competitive ability between Chromolaena odorata plants of populations from nonnative versus native ranges, considering biogeographical differences in both biotic and abiotic environments. An intraspecific competition experiment was conducted at two nutrient levels in a common garden. In both low and high nutrient treatments, C. odorata plants from nonnative ranges showed consistently lower root to shoot ratios than did plants from native ranges grown in both monoculture and competition. In the low nutrient treatment, C. odorata plants from nonnative ranges showed significantly lower competitive ability (competition-driven decreases in plant height and biomass were more), which was associated with their lower root to shoot ratios and higher total leaf phenolic content (defense trait). In the high nutrient treatment, C. odorata plants from nonnative ranges showed lower leaf toughness and cellulosic contents (defense traits) but similar competitive ability compared with plants from native ranges, which was also associated with their lower root to shoot ratios. Our results indicate that genetically based shifts in biomass allocation (responses to abiotic environments) also influence competitive abilities of invasive plants, and provide a first potential mechanism for the interaction between range and environment (environment-dependent difference between ranges). PMID:23977140
-
Peeters, Edwin T H M; Neefjes, Rozemarijn E M; Zuidam, Bastiaan G van
2016-01-01
Nutrients can determine the outcome of the competition between different floating plant species. The response of floating plants to current phosphorus levels may be affected by previously experienced phosphorus concentrations because some species have the ability to store excess phosphorus for later use. This might have an impact on their competition. Here, we investigate the effect of previous and actual phosphorus concentrations on the growth rate of free-floating plant species (Azolla filiculoides, Lemna minor/gibba and Ricciocarpus natans)and the effect of phosphorus history on the competition between L. minor/gibba and A. filiculoides and between L. minor/gibba and R. natans. As expected, plant growth was lower when previously kept at low instead of high phosphorus concentrations. Growth of L. minor/gibba and A. filiculoides with a phosphorus rich history was comparable for low and high actual phosphorus concentrations, however, internal phosphorus concentrations were significantly lower with low actual phosphorus concentration. This indicates that both species perform luxury phosphorus uptake. Furthermore, internal P concentration in Azolla and Lemna increased within two weeks after a period of P deficit without a strong increase in growth. A. filiculoides in a mixture with L. minor/gibba grew faster than its monoculture. Morphological differences may explain why A. filiculoides outcompeted L. minor/gibba and these differences may be induced by phosphorus concentrations in the past. Growth of L. minor/gibba was only reduced by the presence of A. filiculoides with a high phosphorus history. Growth of L. minor/gibba and R. natans in mixtures was positively affected only when they had a high phosphorus history themselves and their competitor a low phosphorus history. These observations clearly indicate that phosphorus history of competing plants is important for understanding the outcome of the competition. Therefore, actual and previously experienced phosphorus
-
Dietz, Hansjörg; Steinlein, Thomas; Ullmann, Isolde
1998-02-01
The competitive abilities of six perennial ruderal plants of three different growth forms were compared via yield measures using an additive diallel experimental design with unbalanced mixtures (9:3 or 3:9 plants per pot, respectively). Thus, in a given mixture species A was grown in two configurations: three individuals in centre position of the pot together with nine plants of species B in border position and vice versa. Effect competitive abilities as well as response competitive abilities of the species were significantly related to canopy height and plant biomass. The species with lower rosette growth form and smaller biomasses were weaker competitors than the species possessing elevated canopies along with higher biomasses, whereas total leaf area was not significantly correlated with competitive ability between species. Species differences in competitive ability were stronger between the plants grown in the central position than between those grown in the border position. Furthermore, interactions between species-specific traits and configuration could be observed, indicating the importance of species proportions and arrangement patterns for evaluation of competitive outcome in the field. The degree of complete transitivity of the competitive network of the six ruderal species, which was significantly higher than expected under the null model in our experimental design, also seemed to depend on species proportions in mixture. Shifts in root:shoot ratio of the centre plants when faced with competition by the border plants were in the direction of higher shoot allocation for the weak competitors with rosette growth form irrespective of the neighbour species, except for Bunias orientalis, which showed a more plastic response. The stronger competitors showed higher root allocation ( Urtica dioica) or were hardly affected at all. Consistent with the results of our experiment, the weaker competitors occur at rather frequently disturbed and therefore transient
-
New rules for competition: Ontario to cap power plant emissions
International Nuclear Information System (INIS)
Anon.
1999-01-01
The Ontario government through the Dept. of the Environment announced on November 16, 1999 that it would cut the emissions from Ontario coal burning power plants that cause acid rain and smog. This announcement was a much anticipated clarification of the government's plans to clean up the power industry since the enactment of the Electricity Competition Act more than one year past. The announcement signals the beginning of a public discussion process between government and stakeholders on the environmental rules for electricity generation in Ontario. The Ontario government is expected to release draft regulations for controlling coal burning power plant emissions in the near future. Consulations with stakeholders on the regulations, as well as the rules for disclosure and labeling, are anticipated to begin in a few months. The announcement set out four principles for environmental performance in the competitive electricity market. Anti-smog requirements will be included in the stringent environmental requirements to be built into Ontario's new, competitive electricity market. The strong measures which the government will put into place when the market opens later in 2000 include: (1) regulations to cut smog and acid gas emissions for all Ontario electricity generators on the grid - these regulations will include Ontario Hydro's voluntary nitrogen oxide limits; (2) emission performance standards to define maximum acceptable emission levels for all generators wanting to sell in the Ontario market; (3) a framework to support opportunities to make greater use of more efficient, environmentally responsible technologies; and (4) disclosure requirements to ensure that electricity consumers can understand the environmental implications of their purchasing decisions
-
Size-symmetric competition in a shade-tolerant invasive plant
DEFF Research Database (Denmark)
Pan, Xiao-Yun; Weiner, Jacob; Li, Bo
2013-01-01
competition need not be size asymmetric, and suggest that tolerance to low light levels involves a reduction in phenotypic plasticity. Responses of the invasive A. philoxeroides to crowding may be an example of an invasive plant’s success in establishing dense stands of closely related individuals......, a shade‐tolerant invasive species. Stem fragments of A. philoxeroides were grown at either low or high densities (6 vs. 24 plants per pot) under three light levels (10%, 34%, and 100% full sun). After 8 weeks, survival was 31% lower in pots with a higher initial density. Both high density and low light...... levels reduced plant size substantially. Mean plant biomass ranged from 0.23 g in high‐density and low‐light pots to 4.41 g in low‐density and high‐light pots. There were no strong or significant effects of density or light level on size inequality of survivors. Most of the variation in allocation...
-
Jing, Y.; Bezemer, T.M.; Putten, van der W.H.
2015-01-01
Plant–soil feedback can affect plants that belong to the same (intraspecific feedback) or different species (interspecific feedback). However, little is known about how intra- and interspecific plant–soil feedbacks influence interspecific plant competition. Here, we used plants and soil from
-
Yuan, Yongge; Tang, Jianjun; Leng, Dong; Hu, Shuijin; Yong, Jean W H; Chen, Xin
2014-01-01
Secondary metabolites released by invasive plants can increase their competitive ability by affecting native plants, herbivores, and pathogens at the invaded land. Whether these secondary metabolites affect the invasive plant itself, directly or indirectly through microorganisms, however, has not been well documented. Here we tested whether activated carbon (AC), a well-known absorbent for secondary metabolites, affect arbuscular mycorrhizal (AM) symbioses and competitive ability in an invasive plant. We conducted three experiments (experiments 1-3) with the invasive forb Solidago canadensis and the native Kummerowia striata. Experiment 1 determined whether AC altered soil properties, levels of the main secondary metabolites in the soil, plant growth, and AMF communities associated with S. canadensis and K. striata. Experiment 2 determined whether AC affected colonization of S. canadensis by five AMF, which were added to sterilized soil. Experiment 3 determined the competitive ability of S. canadensis in the presence and absence of AMF and AC. In experiment 1, AC greatly decreased the concentrations of the main secondary metabolites in soil, and the changes in concentrations were closely related with the changes of AMF in S. canadensis roots. In experiment 2, AC inhibited the AMF Glomus versiforme and G. geosporum but promoted G. mosseae and G. diaphanum in the soil and also in S. canadensis roots. In experiment 3, AC reduced S. canadensis competitive ability in the presence but not in the absence of AMF. Our results provided indirect evidence that the secondary metabolites (which can be absorbed by AC) of the invasive plant S. canadensis may promote S. canadensis competitiveness by enhancing its own AMF symbionts.
-
Model of annual plants dynamics with facilitation and competition.
Droz, Michel; Pękalski, Andrzej
2013-10-21
An individual-based model describing the dynamics of one type of annual plants is presented. We use Monte Carlo simulations where each plant has its own history and the interactions among plants are between nearest neighbours. The character of the interaction (positive or negative) depends on local conditions. The plants compete for two external resources-water and light. The amount of water and/or light a plant receives depends on the external factor but also on local arrangement. Survival, growth and seed production of plants are determined by how well their demands for the resources are met. The survival and seeds production tests have a probabilistic character, which makes the dynamics more realistic than by using a deterministic approach. There is a non-linear coupling between the external supplies. Water evaporates from the soil at a rate depending on constant evaporation rate, local conditions and the amount of light. We examine the dynamics of the plant population along two environmental gradients, allowing also for surplus of water and/or light. We show that the largest number of plants is when the demands for both resources are equal to the supplies. We estimate also the role of evaporation and we find that it depends on the situation. It could be negative, but sometimes it has a positive character. We show that the link between the type of interaction (positive or negative) and external conditions has a complex character. In general in favourable environment plants have a stronger tendency for competitive interactions, leading to mostly isolated plants. When the conditions are getting more difficult, cooperation becomes the dominant type of interactions and the plants grow in clusters. The type of plants-sun-loving or shade tolerating, plays also an important role. © 2013 Elsevier Ltd. All rights reserved.
-
Merrild, Marie P; Ambus, Per; Rosendahl, Søren; Jakobsen, Iver
2013-10-01
Common mycorrhizal networks (CMNs) influence competition between plants, but reports regarding their precise effect are conflicting. We studied CMN effects on phosphorus (P) uptake and growth of seedlings as influenced by various disruptions of network components. Tomato (Solanum lycopersicon) seedlings grew into established networks of Rhizophagus irregularis and cucumber (Cucumis sativus) in two experiments. One experiment studied seedling uptake of (32)P in the network in response to cutting of cucumber shoots; the other analysed seedling uptake of P and nitrogen (N) in the presence of intact or severed arbuscular mycorrhizal fungus networks and at two soil P concentrations. Pre-established and intact networks suppressed growth of tomato seedlings. Cutting of cucumber shoots mitigated P deficiency symptoms of seedlings, which obtained access to P in the extraradical mycelium and thereby showed improved growth. Solitary seedlings growing in a network patch that had been severed from the CMN also grew much better than seedlings of the corresponding CMN. Interspecific and size-asymmetric competition between plants may be amplified rather than relaxed by CMNs that transfer P to large plants providing most carbon and render small plants P deficient. It is likely that grazing or senescence of the large plants will alleviate the network-induced suppression of seedling growth. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.
-
Directory of Open Access Journals (Sweden)
Edwin T H M Peeters
Full Text Available Nutrients can determine the outcome of the competition between different floating plant species. The response of floating plants to current phosphorus levels may be affected by previously experienced phosphorus concentrations because some species have the ability to store excess phosphorus for later use. This might have an impact on their competition. Here, we investigate the effect of previous and actual phosphorus concentrations on the growth rate of free-floating plant species (Azolla filiculoides, Lemna minor/gibba and Ricciocarpus natansand the effect of phosphorus history on the competition between L. minor/gibba and A. filiculoides and between L. minor/gibba and R. natans. As expected, plant growth was lower when previously kept at low instead of high phosphorus concentrations. Growth of L. minor/gibba and A. filiculoides with a phosphorus rich history was comparable for low and high actual phosphorus concentrations, however, internal phosphorus concentrations were significantly lower with low actual phosphorus concentration. This indicates that both species perform luxury phosphorus uptake. Furthermore, internal P concentration in Azolla and Lemna increased within two weeks after a period of P deficit without a strong increase in growth. A. filiculoides in a mixture with L. minor/gibba grew faster than its monoculture. Morphological differences may explain why A. filiculoides outcompeted L. minor/gibba and these differences may be induced by phosphorus concentrations in the past. Growth of L. minor/gibba was only reduced by the presence of A. filiculoides with a high phosphorus history. Growth of L. minor/gibba and R. natans in mixtures was positively affected only when they had a high phosphorus history themselves and their competitor a low phosphorus history. These observations clearly indicate that phosphorus history of competing plants is important for understanding the outcome of the competition. Therefore, actual and previously
-
Peeters, Edwin T. H. M.; Neefjes, Rozemarijn E. M.; van Zuidam, Bastiaan G.
2016-01-01
Nutrients can determine the outcome of the competition between different floating plant species. The response of floating plants to current phosphorus levels may be affected by previously experienced phosphorus concentrations because some species have the ability to store excess phosphorus for later use. This might have an impact on their competition. Here, we investigate the effect of previous and actual phosphorus concentrations on the growth rate of free-floating plant species (Azolla filiculoides, Lemna minor/gibba and Ricciocarpus natans)and the effect of phosphorus history on the competition between L. minor/gibba and A. filiculoides and between L. minor/gibba and R. natans. As expected, plant growth was lower when previously kept at low instead of high phosphorus concentrations. Growth of L. minor/gibba and A. filiculoides with a phosphorus rich history was comparable for low and high actual phosphorus concentrations, however, internal phosphorus concentrations were significantly lower with low actual phosphorus concentration. This indicates that both species perform luxury phosphorus uptake. Furthermore, internal P concentration in Azolla and Lemna increased within two weeks after a period of P deficit without a strong increase in growth. A. filiculoides in a mixture with L. minor/gibba grew faster than its monoculture. Morphological differences may explain why A. filiculoides outcompeted L. minor/gibba and these differences may be induced by phosphorus concentrations in the past. Growth of L. minor/gibba was only reduced by the presence of A. filiculoides with a high phosphorus history. Growth of L. minor/gibba and R. natans in mixtures was positively affected only when they had a high phosphorus history themselves and their competitor a low phosphorus history. These observations clearly indicate that phosphorus history of competing plants is important for understanding the outcome of the competition. Therefore, actual and previously experienced phosphorus
-
Directory of Open Access Journals (Sweden)
K. Bohn
2011-05-01
Full Text Available While the regional climate is the primary selection pressure for whether a plant strategy can survive, however, competitive interactions strongly affect the relative abundances of plant strategies within communities. Here, we investigate the relative importance of competition and perturbations on the development of vegetation community structure. To do so, we develop DIVE (Dynamics and Interactions of VEgetation, a simple general model that links plant strategies to their competitive dynamics, using growth and reproduction characteristics that emerge from climatic constraints. The model calculates population dynamics based on establishment, mortality, invasion and exclusion in the presence of different strengths of perturbations, seed and resource competition. The highest levels of diversity were found in simulations without competition as long as mortality is not too high. However, reasonable successional dynamics were only achieved when resource competition is considered. Under high levels of competition, intermediate levels of perturbations were required to obtain coexistence. Since succession and coexistence are observed in plant communities, we conclude that the DIVE model with competition and intermediate levels of perturbation represents an adequate way to model population dynamics. Because of the simplicity and generality of DIVE, it could be used to understand vegetation structure and functioning at the global scale and the response of vegetation to global change.
-
Felker-Quinn, Emmi; Schweitzer, Jennifer A; Bailey, Joseph K
2013-03-01
Ecological explanations for the success and persistence of invasive species vastly outnumber evolutionary hypotheses, yet evolution is a fundamental process in the success of any species. The Evolution of Increased Competitive Ability (EICA) hypothesis (Blossey and Nötzold 1995) proposes that evolutionary change in response to release from coevolved herbivores is responsible for the success of many invasive plant species. Studies that evaluate this hypothesis have used different approaches to test whether invasive populations allocate fewer resources to defense and more to growth and competitive ability than do source populations, with mixed results. We conducted a meta-analysis of experimental tests of evolutionary change in the context of EICA. In contrast to previous reviews, there was no support across invasive species for EICA's predictions regarding defense or competitive ability, although invasive populations were more productive than conspecific native populations under noncompetitive conditions. We found broad support for genetically based changes in defense and competitive plant traits after introduction into new ranges, but not in the manner suggested by EICA. This review suggests that evolution occurs as a result of plant introduction and population expansion in invasive plant species, and may contribute to the invasiveness and persistence of some introduced species.
-
Farrer, Emily C; Suding, Katharine N
2016-10-01
Although ecologists have documented the effects of nitrogen enrichment on productivity, diversity and species composition, we know little about the relative importance of the mechanisms driving these effects. We propose that distinct aspects of environmental change associated with N enrichment (resource limitation, asymmetric competition, and interactions with soil microbes) drive different aspects of plant response. We test this in greenhouse mesocosms, experimentally manipulating each factor across three ecosystems: tallgrass prairie, alpine tundra and desert grassland. We found that resource limitation controlled productivity responses to N enrichment in all systems. Asymmetric competition was responsible for diversity declines in two systems. Plant community composition was impacted by both asymmetric competition and altered soil microbes, with some contributions from resource limitation. Results suggest there may be generality in the mechanisms of plant community change with N enrichment. Understanding these links can help us better predict N response across a wide range of ecosystems. © 2016 John Wiley & Sons Ltd/CNRS.
-
Directory of Open Access Journals (Sweden)
Yongge Yuan
Full Text Available Secondary metabolites released by invasive plants can increase their competitive ability by affecting native plants, herbivores, and pathogens at the invaded land. Whether these secondary metabolites affect the invasive plant itself, directly or indirectly through microorganisms, however, has not been well documented. Here we tested whether activated carbon (AC, a well-known absorbent for secondary metabolites, affect arbuscular mycorrhizal (AM symbioses and competitive ability in an invasive plant. We conducted three experiments (experiments 1-3 with the invasive forb Solidago canadensis and the native Kummerowia striata. Experiment 1 determined whether AC altered soil properties, levels of the main secondary metabolites in the soil, plant growth, and AMF communities associated with S. canadensis and K. striata. Experiment 2 determined whether AC affected colonization of S. canadensis by five AMF, which were added to sterilized soil. Experiment 3 determined the competitive ability of S. canadensis in the presence and absence of AMF and AC. In experiment 1, AC greatly decreased the concentrations of the main secondary metabolites in soil, and the changes in concentrations were closely related with the changes of AMF in S. canadensis roots. In experiment 2, AC inhibited the AMF Glomus versiforme and G. geosporum but promoted G. mosseae and G. diaphanum in the soil and also in S. canadensis roots. In experiment 3, AC reduced S. canadensis competitive ability in the presence but not in the absence of AMF. Our results provided indirect evidence that the secondary metabolites (which can be absorbed by AC of the invasive plant S. canadensis may promote S. canadensis competitiveness by enhancing its own AMF symbionts.
-
Economic competitiveness of small modular reactors versus coal and combined cycle plants
International Nuclear Information System (INIS)
Alonso, Gustavo; Bilbao, Sama; Valle, Edmundo del
2016-01-01
Small modular reactors (SMRs) may be an option to cover the electricity needs of isolated regions, distributed generation grids and countries with small electrical grids. Previous analyses show that the overnight capital cost for SMRs is between 4500 US$/kW and 5350 US$/kW, which is between a 6% and a 26% higher than the average cost of a current large nuclear reactor. This study analyzes the economic competitiveness of small modular reactors against thermal plants using coal and natural gas combined cycle plants. To assess the economic competitiveness of SMRs, three overnight capital costs are considered 4500 US$/kW, 5000 US$/kW and 5350 US$/kW along with three discount rates for each overnight cost considered, these are 3, 7, and 10%. To compare with natural gas combined cycle (CC) units, four different gas prices are considered, these are 4.74 US$/GJ (5 US$/mmBTU), 9.48 US$/GJ (10 US$/mmBTU), 14.22 US$/GJ (15 US$/mmBTU), and 18.96 US$/GJ (20 US$/mmBTU). To compare against coal, two different coal prices are considered 80 and 120 US$/ton of coal. The carbon tax considered, for both CC and coal, is 30 US$/ton CO_2. The results show what scenarios make SMRs competitive against coal and/or combined cycle plants. In addition, because the price of electricity is a key component to guarantee the feasibility of a new project, this analysis calculates the price of electricity for the economically viable deployment of SMRs in all the above scenarios. In particular, this study shows that a minimum price of electricity of 175 US$/MWh is needed to guarantee the feasibility of a new SMR, if its overnight capital cost is 5350 US$/kWe and the discount rate is 10%. Another result is that when the price of electricity is around 100 US$/MWh then the discount rate must be around 7% or less to provide appropriate financial conditions to make SMRs economically feasible. - Highlights: • Small modular reactor (SMR) are economically assessed. • SMR are compared against gas and coal
-
Trinder, Clare J; Brooker, Rob W; Davidson, Hazel; Robinson, David
2012-01-01
Although rarely acknowledged, our understanding of how competition is modulated by environmental drivers is severely hampered by our dependence on indirect measurements of outcomes, rather than the process of competition. To overcome this, we made direct measurements of plant competition for soil nitrogen (N). Using isotope pool-dilution, we examined the interactive effects of soil resource limitation and climatic severity between two common grassland species. Pool-dilution estimates the uptake of total N over a defined time period, rather than simply the uptake of ¹⁵N label, as used in most other tracer experiments. Competitive uptake of N was determined by its available form (NO₃⁻ or NH₄⁺). Soil N availability had a greater effect than the climatic conditions (location) under which plants grew. The results did not entirely support either of the main current theories relating the role of competition to environmental conditions. We found no evidence for Tilman's theory that competition for soil nutrients is stronger at low, compared with high nutrient levels and partial support for Grime's theory that competition for soil nutrients is greater under potentially more productive conditions. These results provide novel insights by demonstrating the dynamic nature of plant resource competition.
-
Directory of Open Access Journals (Sweden)
Clare J Trinder
Full Text Available Although rarely acknowledged, our understanding of how competition is modulated by environmental drivers is severely hampered by our dependence on indirect measurements of outcomes, rather than the process of competition. To overcome this, we made direct measurements of plant competition for soil nitrogen (N. Using isotope pool-dilution, we examined the interactive effects of soil resource limitation and climatic severity between two common grassland species. Pool-dilution estimates the uptake of total N over a defined time period, rather than simply the uptake of ¹⁵N label, as used in most other tracer experiments. Competitive uptake of N was determined by its available form (NO₃⁻ or NH₄⁺. Soil N availability had a greater effect than the climatic conditions (location under which plants grew. The results did not entirely support either of the main current theories relating the role of competition to environmental conditions. We found no evidence for Tilman's theory that competition for soil nutrients is stronger at low, compared with high nutrient levels and partial support for Grime's theory that competition for soil nutrients is greater under potentially more productive conditions. These results provide novel insights by demonstrating the dynamic nature of plant resource competition.
-
Energy Technology Data Exchange (ETDEWEB)
Cseresnyés, I.; Takács, T.; Füzy, A.; Végh, K.R.; Lehoczky, E.
2016-11-01
Applicability of root electrical capacitance (EC) measurement for monitoring of crop–weed competition was studied in a pot experiment. Maize (Zea mays L.) was grown both alone and with Echinochloa crus-galli or Abutilon theophrasti in different densities with regular measurement of root EC. Plants were harvested 42 days after planting to determine above- and belowground biomass. Depending on weed density, E. crus-galli-A. theophrasti interaction reduced the root EC of maize by 22–66% and 3–57%, respectively. Competitive effect of crop on weeds and intraspecific competition among weeds could also be detected by EC values: E. crus-galli was less sensitive both to the presence of maize and to intraspecific competition than A. theophrasti. Strong linear correlations between root dry mass and root EC for crop and weeds (with R2 from 0.901 to 0.956) were obtained by regression analyses at the end of the experiment. EC monitoring informed us on the emergence time of competition: E. crus-galli interfered with maize root growth a week earlier then A. theophrasti, and increasing weed densities accelerated the emergence of competition. In conclusion, the simple, non-destructive EC method should be considered a potential in situ technique for pot studies on crop–weed competition, which may partially substitute the intrusive techniques commonly used in agricultural researches. (Author)
-
Just, Winfried; Nevai, Andrew L.
2008-12-01
It is demonstrated that a Kolmogorov-type competition model featuring species allocation and gain functions can possess multiple coexistence statesE Two examples are constructed: one in which the two competing species possess rectangular allocation functions but distinct gain functions, and the other in which one species has a rectangular allocation function, the second species has a bi-rectangular allocation function, and the two species share a common gain function. In both examples, it is shown that the species nullclines may intersect multiple times within the interior of the first quadrant, thus creating both locally stable and unstable equilibrium points. These results have important applications in the study of plant competition for sunlight, in which the allocation functions describe the vertical placement of leaves for two competing species, and the gain functions represent rates of photosynthesis performed by leaves at different heights when shaded by overlying leaves belonging to either species.
-
Interactive effects of copper pollution, competition and drought on plant growth
DEFF Research Database (Denmark)
Pedersen, Marianne Bruus; Kjær, C.
Previous studies have indicated that the toxicity of copper to plants in the field is enhanced compared to single-species laboratory tests with the same soil, i.e. under similar bioavailability conditions. The purpose of the present study was to examine whether this difference in toxicity between...... laboratory and field conditions may be explained by interactions between copper toxicity and climate (drought) or competition....
-
Andrew B. Bernard; J. Bradford Jensen; Peter K. Schott
2002-01-01
We examine the relationship between import competition from low wage countries and the reallocation of US manufacturing from 1977 to 1997. Both employment and output growth are slower for plants that face higher levels of low wage import competition in their industry. As a result, US manufacturing is reallocated over time towards industries that are more capital and skill intensive. Differential growth is driven by a combination of increased plant failure rates and slower growth of surviving ...
-
Grandy, S.; Jilling, A.; Keiluweit, M.
2016-12-01
Recent research on the rate limiting steps in soil nitrogen (N) availability have shifted in focus from mineralization to soil organic matter (SOM) depolymerization. To that end, Schimel and Bennett (2004) argued that together with enzymatic breakdown of polymers to monomers, microsite processes and plant-microbial competition collectively drive N cycling. Here we present new conceptual models arguing that while depolymerization is a critical first step, mineral-organic associations may ultimately regulate the provisioning of bioavailable organic N, especially in the rhizosphere. Mineral-associated organic matter (MAOM) is a rich reservoir for N in soils and often holds 5-7x more N than particulate or labile fractions. However, MAOM is considered largely unavailable to plants as a source of N due to the physicochemical forces on mineral surfaces that stabilize organic matter. We argue that in rhizosphere hotspots, MAOM is in fact a potentially mineralizable and important source of nitrogen for plants. Several biochemical strategies enable plants and microbes to compete with mineral-organic interactions and effectively access MAOM. In particular, root-deposited low molecular weight compounds in the form of root exudates facilitate the biotic and abiotic destabilization and subsequent bioavailability of MAOM. We believe that the competitive balance between the potential fates of assimilable organic N — bound to mineral surfaces or dissolved and available for assimilation — depends on the specific interaction between and properties of the clay, soil solution, mineral-bound organic matter, and microbial community. For this reason, the plant-soil-MAOM interplay is enhanced in rhizosphere hotspots relative to non-rhizosphere environments, and likely strongly regulates plant-microbe competition for N. If these hypotheses are true, we need to reconsider potential soil N cycle responses to changes in climate and land use intensity, focusing on the processes by which
-
Peeters, E.T.H.M.; Neefjes, Rozemarijn; Zuidam, van B.G.
2016-01-01
Nutrients can determine the outcome of the competition between different floating plant species. The response of floating plants to current phosphorus levels may be affected by previously experienced phosphorus concentrations because some species have the ability to store excess phosphorus for later
-
Improving competitive ability of chickpea with sowthistle
Cici, S.-Z.-H.; Kristiansen, P.; Sindel, B.M.
2005-01-01
An experiment was conducted to examine the extent of root and canopy interference of chickpea (Cicer arietinum L.) with sowthistle (Sonchus oleraceus L.). Sowthistle was surrounded with either two or eight chickpea plants. There were different types of competition: no competition, shoot competition, root competition and full competition (root and shoot). The performance of sowthistle grown in full competition with two chickpea plants was the same as that grown with root competition only. Al...
-
International Nuclear Information System (INIS)
Rogeaux, B.
2006-01-01
Will coal electrical plants be more competitive in the coming years? Answering this one cannot be limited to merely comparing estimates based on reference electricity production costs. The competitiveness of coal will indeed depend on the final product marketed, as the MWhs are not equal: is the purpose to produce base, half-base MWh? Does the electrical equipment structure require flexible MWh (for instance in the event of significant intermittent renewable energy amounts), and therefore plants able to adjust their power rapidly? But the competitiveness of coal will also depend on many factors that will correct reference cost estimates: uncertainties, risks, externalities. These factors will need to be appreciated on a case by case basis. We introduce some of the reasoning used to better appreciate the future competitiveness of coal, and the main factors conditioning it in three contrasting regions of the world: Europe, USA, china. (author)
-
Incorporating the soil environment and microbial community into plant competition theory.
Ke, Po-Ju; Miki, Takeshi
2015-01-01
Plants affect microbial communities and abiotic properties of nearby soils, which in turn influence plant growth and interspecific interaction, forming a plant-soil feedback (PSF). PSF is a key determinant influencing plant population dynamics, community structure, and ecosystem functions. Despite accumulating evidence for the importance of PSF and development of specific PSF models, different models are not yet fully integrated. Here, we review the theoretical progress in understanding PSF. When first proposed, PSF was integrated with various mathematical frameworks to discuss its influence on plant competition. Recent theoretical models have advanced PSF research at different levels of ecological organizations by considering multiple species, applying spatially explicit simulations to examine how local-scale predictions apply to larger scales, and assessing the effect of PSF on plant temporal dynamics over the course of succession. We then review two foundational models for microbial- and litter-mediated PSF. We present a theoretical framework to illustrate that although the two models are typically presented separately, their behavior can be understood together by invasibility analysis. We conclude with suggestions for future directions in PSF theoretical studies, which include specifically addressing microbial diversity to integrate litter- and microbial-mediated PSF, and apply PSF to general coexistence theory through a trait-based approach.
-
Incorporating the soil environment and microbial community into plant competition theory
Ke, Po-Ju; Miki, Takeshi
2015-01-01
Plants affect microbial communities and abiotic properties of nearby soils, which in turn influence plant growth and interspecific interaction, forming a plant-soil feedback (PSF). PSF is a key determinant influencing plant population dynamics, community structure, and ecosystem functions. Despite accumulating evidence for the importance of PSF and development of specific PSF models, different models are not yet fully integrated. Here, we review the theoretical progress in understanding PSF. When first proposed, PSF was integrated with various mathematical frameworks to discuss its influence on plant competition. Recent theoretical models have advanced PSF research at different levels of ecological organizations by considering multiple species, applying spatially explicit simulations to examine how local-scale predictions apply to larger scales, and assessing the effect of PSF on plant temporal dynamics over the course of succession. We then review two foundational models for microbial- and litter-mediated PSF. We present a theoretical framework to illustrate that although the two models are typically presented separately, their behavior can be understood together by invasibility analysis. We conclude with suggestions for future directions in PSF theoretical studies, which include specifically addressing microbial diversity to integrate litter- and microbial-mediated PSF, and apply PSF to general coexistence theory through a trait-based approach. PMID:26500621
-
Incorporating the soil environment and microbial community into plant competition theory
Directory of Open Access Journals (Sweden)
Po-Ju eKe
2015-10-01
Full Text Available Plants affect microbial communities and abiotic properties of nearby soils, which in turn influence plant growth and interspecific interaction, forming a plant-soil feedback (PSF. PSF is a key determinant influencing plant population dynamics, community structure, and ecosystem functions. Despite accumulating evidence for the importance of PSF and development of specific PSF models, different models are not yet fully integrated. Here, we review the theoretical progress in understanding PSF. When first proposed, PSF was integrated with various mathematical frameworks to discuss its influence on plant competition. Recent theoretical models have advanced PSF research at different levels of ecological organizations by considering multiple species, applying spatially explicit simulations to examine how local-scale predictions apply to larger scales, and assessing the effect of PSF on plant temporal dynamics over the course of succession. We then review two foundational models for microbial- and litter-mediated PSF. We present a theoretical framework to illustrate that although the two models are typically presented separately, their behavior can be understood together by invasibility analysis. We conclude with suggestions for future directions in PSF theoretical studies, which include specifically addressing microbial diversity to integrate litter- and microbial-mediated PSF, and apply PSF to general coexistence theory through a trait-based approach.
-
Pujol, B; McKey, D
2006-01-01
The effects of competition on the genetic composition of natural populations are not well understood. We combined demography and molecular genetics to study how intraspecific competition affects microevolution in cohorts of volunteer plants of cassava (Manihot esculenta) originating from seeds in slash-and-burn fields of Palikur Amerindians in French Guiana. In this clonally propagated crop, genotypic diversity is enhanced by the incorporation of volunteer plants into farmers' stocks of clonal propagules. Mortality of volunteer plants was density-dependent. Furthermore, the size asymmetry of intraspecific competition increased with local clustering of plants. Size of plants was correlated with their multilocus heterozygosity, and stronger size-dependence of survival in clusters of plants, compared with solitary plants, increased the magnitude of inbreeding depression when competition was severe. The density-dependence of inbreeding depression of volunteer plants helps explain the high heterozygosity of volunteers that survive to harvest time and thus become candidates for clonal propagation. This effect could help favour the maintenance of sex in this 'vegetatively' propagated crop plant.
-
Garbuzov, Mihail; Reidinger, Stefan; Hartley, Susan E.
2011-01-01
Background and Aims The herbivore defence system of true grasses (Poaceae) is predominantly based on silicon that is taken up from the soil and deposited in the leaves in the form of abrasive phytoliths. Silicon uptake mechanisms can be both passive and active, with the latter suggesting that there is an energetic cost to silicon uptake. This study assessed the effects of plant-available soil silicon and herbivory on the competitive interactions between the grasses Poa annua, a species that has previously been reported to accumulate only small amounts of silicon, and Lolium perenne, a high silicon accumulator. Methods Plants were grown in mono- and mixed cultures under greenhouse conditions. Plant-available soil silicon levels were manipulated by adding silicon to the soil in the form of sodium silicate. Subsets of mixed culture pots were exposed to above-ground herbivory by desert locusts (Schistocerca gregaria). Key Results In the absence of herbivory, silicon addition increased biomass of P. annua but decreased biomass of L. perenne. Silicon addition increased foliar silicon concentrations of both grass species >4-fold. Under low soil-silicon availability the herbivores removed more leaf biomass from L. perenne than from P. annua, whereas under high silicon availability the reverse was true. Consequently, herbivory shifted the competitive balance between the two grass species, with the outcome depending on the availability of soil silicon. Conclusions It is concluded that a complex interplay between herbivore abundance, growth–defence trade-offs and the availability of soil silicon in the grasses' local environment affects the outcome of inter-specific competition, and so has the potential to impact on plant community structure. PMID:21868406
-
Wang, Yong-Jian; Shi, Xue-Ping; Meng, Xue-Feng; Wu, Xiao-Jing; Luo, Fang-Li; Yu, Fei-Hai
2016-01-01
Spatial heterogeneity in two co-variable resources such as light and water availability is common and can affect the growth of clonal plants. Several studies have tested effects of spatial heterogeneity in the supply of a single resource on competitive interactions of plants, but none has examined those of heterogeneous distribution of two co-variable resources. In a greenhouse experiment, we grew one (without intraspecific competition) or nine isolated ramets (with competition) of a rhizomatous herb Iris japonica under a homogeneous environment and four heterogeneous environments differing in patch arrangement (reciprocal and parallel patchiness of light and soil water) and patch scale (large and small patches of light and water). Intraspecific competition significantly decreased the growth of I. japonica, but at the whole container level there were no significant interaction effects of competition by spatial heterogeneity or significant effect of heterogeneity on competitive intensity. Irrespective of competition, the growth of I. japonica in the high and the low water patches did not differ significantly in the homogeneous treatments, but it was significantly larger in the high than in the low water patches in the heterogeneous treatments with large patches. For the heterogeneous treatments with small patches, the growth of I. japonica was significantly larger in the high than in the low water patches in the presence of competition, but such an effect was not significant in the absence of competition. Furthermore, patch arrangement and patch scale significantly affected competitive intensity at the patch level. Therefore, spatial heterogeneity in light and water supply can alter intraspecific competition at the patch level and such effects depend on patch arrangement and patch scale.
-
Yu, Kailiang; D'Odorico, Paolo; Carr, David E; Personius, Ashden; Collins, Scott L
2017-10-01
Plants with crassulacean acid metabolism (CAM) are increasing their abundance in drylands worldwide. The drivers and mechanisms underlying the increased dominance of CAM plants and CAM expression (i.e., nocturnal carboxylation) in facultative CAM plants, however, remain poorly understood. We investigated how nutrient and water availability affected competition between Mesembryanthemum crystallinum (a model facultative CAM species) and the invasive C 3 grass Bromus mollis that co-occur in California's coastal grasslands. Specifically we investigated the extent to which water stress, nutrients, and competition affect nocturnal carboxylation in M. crystallinum . High nutrient and low water conditions favored M. crystallinum over B. mollis , in contrast to high water conditions. While low water conditions induced nocturnal carboxylation in 9-week-old individuals of M. crystallinum , in these low water treatments, a 66% reduction in nutrient applied over the entire experiment did not further enhance nocturnal carboxylation. In high water conditions M. crystallinum both alone and in association with B. mollis did not perform nocturnal carboxylation, regardless of the nutrient levels. Thus, nocturnal carboxylation in M. crystallinum was restricted by strong competition with B. mollis in high water conditions. This study provides empirical evidence of the competitive advantage of facultative CAM plants over grasses in drought conditions and of the restricted ability of M. crystallinum to use their photosynthetic plasticity (i.e., ability to switch to CAM behavior) to compete with grasses in well-watered conditions. We suggest that a high drought tolerance could explain the increased dominance of facultative CAM plants in a future environment with increased drought and nitrogen deposition, while the potential of facultative CAM plants such as M. crystallinum to expand to wet environments is expected to be limited.
-
Bauer, S.; Wyszomirski, T.; Berger, U.; Hildenbrandt, H.; Grimm, V.
2004-01-01
Numerous attempts have been made to infer the mode of competition from size or biomass distributions of plant cohorts. However, since the relationship between mode of competition and size distributions may be obscured by a variety of factors such as spatial configuration, density or resource level,
-
Wu, Hao; Ismail, Mohannad; Ding, Jianqing
2017-01-01
Global warming could accelerate the spread of invasive species to higher latitudes and intensify their effects on native species. Here, we report results of two years of field surveys along a latitudinal gradient (21°N to 31°N) in southern China, to determine the species structure of the invasive plant Alternanthera philoxeroides community. We also performed a replacement series experiment (mono and mixed) to evaluate the effects of elevated temperature on the competitiveness of A. philoxeroides with the native co-occurring species Digitaria sanguinalis. In the field survey, we found that the dominance of A. philoxeroides increased with increasing of latitude gradient while cover of D. sanguinalis decreased. In monospecific plantings, artificial warming reduced the length of D. sanguinalis roots. In mixed plantings, warming reduced both A. philoxeroides abundance and D. sanguinalis stem length when A. philoxeroides was more prevalent in the planting. Warming also significantly reduced D. sanguinalis biomass, but increased that of A. philoxeroides. In addition, elevated temperatures significantly reduced the relative yield (RY) of D. sanguinalis, particularly when A. philoxeroides was planted in higher proportion in the plot. These results suggest that the invasiveness of A. philoxeroides increased with increasing latitude, and that warming may increase the effectiveness of its interspecific competition with D. sanguinalis. Hence, under global warming conditions, the harm to native species from A. philoxeroides would increase at higher latitudes. Our findings are critical for predicting the invasiveness of alien species under climate change. Copyright © 2016 Elsevier B.V. All rights reserved.
-
Liu, Gang; Yang, Ying-Bo; Zhu, Zhi-Hong
2018-02-16
Elevated nitrogen associated with global change is believed to promote the invasion of many vigorous exotic plants. However, it is unclear how a weak exotic plant will respond to elevated nitrogen in the future. In this study, the competitive outcome of a weak invasive plant (Galinsoga quadriradiata) and two non-invasive plants was detected. The plants were subjected to 3 types of culture (mixed, monoculture or one-plant), 2 levels of nitrogen (ambient or elevated at a rate of 2 g m -2 yr -1 ) and 2 levels of light (65% shade or full sunlight). The results showed that elevated nitrogen significantly promoted the growth of both the weak invader and the non-invasive plants in one-plant pots; however, growth promotion was not observed for the non-invasive species in the mixed culture pots. The presence of G. quadriradiata significantly inhibited the growth of the non-invasive plants, and a decreased negative species interaction was detected as a result of elevated nitrogen. Our results suggest that competitive interactions between G. quadriradiata and the non-invasive plants were altered by elevated nitrogen. It provides exceptional evidence that an initially weak invasive plant can become an aggressive invader through elevated nitrogen deposition.
-
Rossbach, A; Löhr, B; Vidal, S
2008-04-01
Interspecific competition between an introduced parasitoid species aimed at controlling a herbivorous pest species and a native parasitoid parasitising the same host may influence the success of classical biological control programmes. In Kenya, interspecific competition between an introduced and a local parasitoid on two diamondback moth populations (DBM, Plutella xylostella) was investigated on two different host plants. We tested simultaneous and delayed competition of the local parasitoid Diadegma mollipla Holmgren and its exotic congenus D. semiclausum Hellen on a newly aquired DBM host plant (snowpea) in the laboratory. Under simultaneous competition, D. mollipla produced more progeny than D. semiclausum on snowpea. A head start of D. Mollipla, of four and eight hours before its congenus was introduced, resulted in a similar number of progeny of both species. In delayed competition (time intervals of 24 h, 48 h and 72 h), progeny production was similar for both parasitoids when the time interval was 24 h, irrespective of which species parasitized first. More progeny was produced by the species which attacked first, when the time interval was greater than 24 h, although it was only significant at 72 h. Competitive abilites of both parasitoids on the new host plant differed largely between laboratory and semi-field conditions. The influence of two host plants (snowpea and cabbage) on competition was studied in the greenhouse with different host and parasitoid densities. Parasitism levels of D. semiclausum were significantly higher than those of D. mollipla, regardless of host plant, host and parasitoid densities, but progeny production of D. mollipla on snowpea was still slightly higher than on cabbage. As compared to the confinement of parasitoids and larvae to small containers, D. mollipla parasitized very few larvae in the cages. Competitive ability of the two parasitoid species tested was influenced both by the density of the searching females and by
-
Reproductive efficiency and shade avoidance plasticity under simulated competition
Fazlioglu, Fatih; Al?Namazi, Ali; Bonser, Stephen P.
2016-01-01
Abstract Plant strategy and life?history theories make different predictions about reproductive efficiency under competition. While strategy theory suggests under intense competition iteroparous perennial plants delay reproduction and semelparous annuals reproduce quickly, life?history theory predicts both annual and perennial plants increase resource allocation to reproduction under intense competition. We tested (1) how simulated competition influences reproductive efficiency and competitiv...
-
International Nuclear Information System (INIS)
Theodose, T.A.; Jaeger, C.H.; Bowman, W.D.; Schardt, J.C.
1996-01-01
Several potential components of competitive ability were determined for 13 plant species in a N-limited alpine moist meadow community in order to determine if competition had an influence on relative abundance in this stressful environment. The components of competitive ability examined were 15 N uptake rate, 15 N allocation, whole plant biomass, root:shoot ratio, and tissue N concentrations. It was hypothesized that 15 N uptake rate would be the component most correlated with relative abundance. However, 15 N uptake rate was negatively correlated with percent cover in the community. In contrast, whole plant biomass and root:shoot ratio were positively correlated with relative abundance. Tissue N concentrations and 15 N allocation were not important predictors of relative abundance. These results suggest that in a harsh environment, high resource uptake rates are not indicative of competitive ability, but may instead by a mechanism by which rare species are able to coexist with competitive dominants. (au) 47 refs
-
Soliveres, Santiago; Eldridge, David J.; Maestre, Fernando T.; Bowker, Matthew A.; Tighe, Matthew; Escudero, Adrián
2015-01-01
Studies of facilitative interactions as drivers of plant richness along environmental gradients often assume the existence of an overarching stress gradient equally affecting the performance of all the species in a given community. However, co-existing species differ in their ecophysiological adaptations, and do not experience the same stress level under particular environmental conditions. Moreover, these studies assume a unimodal richness-biomass curve, which is not as general as previously thought. We ignored these assumptions to assess changes in plant-plant interactions, and their effect on local species richness, across environmental gradients in semi-arid areas of Spain and Australia. We aimed to understand the relative importance of direct (microhabitat amelioration) and indirect (changes in the competitive relationships among the understorey species: niche segregation, competitive exclusion or intransitivity) mechanisms that might underlie the effects of nurse plants on local species richness. By jointly studying these direct and indirect mechanisms using a unifying framework, we were able to see how our nurse plants (trees, shrubs and tussock grasses) not only increased local richness by expanding the niche of neighbouring species, but also by increasing niche segregation among them, though the latter was not important in all cases. The outcome of the competition-facilitation continuum changed depending on the study area, likely because the different types of stress gradient considered. When driven by both rainfall and temperature, or rainfall alone, the community-wide importance of nurse plants remained constant (Spanish sites), or showed a unimodal relationship along the gradient (Australian sites). This study expands our understanding of the relative roles of plant-plant interactions and environmental conditions as drivers of local species richness in semi-arid environments. These results can also be used to refine predictions about the response of
-
Soliveres, Santiago; Eldridge, David J; Maestre, Fernando T; Bowker, Matthew A; Tighe, Matthew; Escudero, Adrián
2011-11-20
Studies of facilitative interactions as drivers of plant richness along environmental gradients often assume the existence of an overarching stress gradient equally affecting the performance of all the species in a given community. However, co-existing species differ in their ecophysiological adaptations, and do not experience the same stress level under particular environmental conditions. Moreover, these studies assume a unimodal richness-biomass curve, which is not as general as previously thought. We ignored these assumptions to assess changes in plant-plant interactions, and their effect on local species richness, across environmental gradients in semi-arid areas of Spain and Australia. We aimed to understand the relative importance of direct (microhabitat amelioration) and indirect (changes in the competitive relationships among the understorey species: niche segregation, competitive exclusion or intransitivity) mechanisms that might underlie the effects of nurse plants on local species richness. By jointly studying these direct and indirect mechanisms using a unifying framework, we were able to see how our nurse plants (trees, shrubs and tussock grasses) not only increased local richness by expanding the niche of neighbouring species, but also by increasing niche segregation among them, though the latter was not important in all cases. The outcome of the competition-facilitation continuum changed depending on the study area, likely because the different types of stress gradient considered. When driven by both rainfall and temperature, or rainfall alone, the community-wide importance of nurse plants remained constant (Spanish sites), or showed a unimodal relationship along the gradient (Australian sites). This study expands our understanding of the relative roles of plant-plant interactions and environmental conditions as drivers of local species richness in semi-arid environments. These results can also be used to refine predictions about the response of
-
Wundrow, Emily J; Carrillo, Juli; Gabler, Christopher A; Horn, Katherine C; Siemann, Evan
2012-01-01
Ecosystems that are heavily invaded by an exotic species often contain abundant populations of other invasive species. This may reflect shared responses to a common factor, but may also reflect positive interactions among these exotic species. Armand Bayou (Pasadena, TX) is one such ecosystem where multiple species of invasive aquatic plants are common. We used this system to investigate whether presence of one exotic species made subsequent invasions by other exotic species more likely, less likely, or if it had no effect. We performed an experiment in which we selectively removed exotic rooted and/or floating aquatic plant species and tracked subsequent colonization and growth of native and invasive species. This allowed us to quantify how presence or absence of one plant functional group influenced the likelihood of successful invasion by members of the other functional group. We found that presence of alligatorweed (rooted plant) decreased establishment of new water hyacinth (free-floating plant) patches but increased growth of hyacinth in established patches, with an overall net positive effect on success of water hyacinth. Water hyacinth presence had no effect on establishment of alligatorweed but decreased growth of existing alligatorweed patches, with an overall net negative effect on success of alligatorweed. Moreover, observational data showed positive correlations between hyacinth and alligatorweed with hyacinth, on average, more abundant. The negative effect of hyacinth on alligatorweed growth implies competition, not strong mutual facilitation (invasional meltdown), is occurring in this system. Removal of hyacinth may increase alligatorweed invasion through release from competition. However, removal of alligatorweed may have more complex effects on hyacinth patch dynamics because there were strong opposing effects on establishment versus growth. The mix of positive and negative interactions between floating and rooted aquatic plants may influence local
-
Directory of Open Access Journals (Sweden)
Emily J Wundrow
Full Text Available Ecosystems that are heavily invaded by an exotic species often contain abundant populations of other invasive species. This may reflect shared responses to a common factor, but may also reflect positive interactions among these exotic species. Armand Bayou (Pasadena, TX is one such ecosystem where multiple species of invasive aquatic plants are common. We used this system to investigate whether presence of one exotic species made subsequent invasions by other exotic species more likely, less likely, or if it had no effect. We performed an experiment in which we selectively removed exotic rooted and/or floating aquatic plant species and tracked subsequent colonization and growth of native and invasive species. This allowed us to quantify how presence or absence of one plant functional group influenced the likelihood of successful invasion by members of the other functional group. We found that presence of alligatorweed (rooted plant decreased establishment of new water hyacinth (free-floating plant patches but increased growth of hyacinth in established patches, with an overall net positive effect on success of water hyacinth. Water hyacinth presence had no effect on establishment of alligatorweed but decreased growth of existing alligatorweed patches, with an overall net negative effect on success of alligatorweed. Moreover, observational data showed positive correlations between hyacinth and alligatorweed with hyacinth, on average, more abundant. The negative effect of hyacinth on alligatorweed growth implies competition, not strong mutual facilitation (invasional meltdown, is occurring in this system. Removal of hyacinth may increase alligatorweed invasion through release from competition. However, removal of alligatorweed may have more complex effects on hyacinth patch dynamics because there were strong opposing effects on establishment versus growth. The mix of positive and negative interactions between floating and rooted aquatic plants may
-
Gremer, Jennifer R; Kimball, Sarah; Keck, Katie R; Huxman, Travis E; Angert, Amy L; Venable, D Lawrence
2013-10-01
A functional approach to investigating competitive interactions can provide a mechanistic understanding of processes driving population dynamics, community assembly, and the maintenance of biodiversity. In Sonoran Desert annual plants, a trade-off between relative growth rate (RGR) and water-use efficiency (WUE) contributes to species differences in population dynamics that promote long-term coexistence. Traits underlying this trade-off explain variation in demographic responses to precipitation as well as life history and phenological patterns. Here, we ask how these traits mediate competitive interactions. • We conducted competition trials for three species occupying different positions along the RGR-WUE trade-off axis and compared the effects of competition at high and low soil moisture. We compared competitive effect (ability to suppress neighbors) and competitive response (ability to withstand competition from neighbors) among species. • The RGR-WUE trade-off predicted shifts in competitive responses at different soil moistures. The high-RGR species was more resistant to competition in high water conditions, while the opposite was true for the high-WUE species. The intermediate RGR species tended to have the strongest impact on all neighbors, so competitive effects did not scale directly with differences in RGR and WUE among competitors. • Our results reveal mechanisms underlying long-term variation in fitness: high-RGR species perform better in years with large, frequent rain events and can better withstand competition under wetter conditions. The opposite is true for high-WUE species. Such resource-dependent responses strongly influence community dynamics and can promote coexistence in variable environments.
-
Zhang, Rui-Chang; Lin, Yue; Yue, Ming; Li, Qian; Zhang, Xiao-Fei; Liu, Xiao; Chi, Hong; Chai, Yong-Fu; Wang, Mao
2012-01-01
(1) The effects of facilitation on the structure and dynamics of plant populations have not been studied so widely as competition. The UV-B radiation, as a typical environmental factor causing stress, may result in direct stress and facilitation. (2) The effects of UV-B radiation on intraspecific competition and facilitation were investigated based on the following three predictions on self-thinning, size inequality, and phenotypic plasticity: i) Self-thinning is the reduction in density that results from the increase in the mean biomass of individuals in crowded populations, and is driven by competition. In this study, the mortality rate of the population is predicted to decrease from UV-B irradiance. ii) The size inequality of a population increases with competition intensity because larger individuals receive a disproportionate share of resources, thereby leaving limited resources for smaller individuals. The second hypothesis assumes that direct stress decreases the size inequality of the population. iii) Phenotypic plasticity is the ability to alter one's morphology in response to environmental changes. The third hypothesis assumes that certain morphological indices can change among the trade-offs between competition, facilitation, and stress. These predictions were tested by conducting a field pot experiment using mung beans, and were supported by the following results: (3) UV-B radiation increased the survival rate of the population at the end of self-thinning. However, this result was mainly due to direct stress rather than facilitation. (4) Just as competitor, facilitation was also asymmetric. It increased the size inequality of populations during self-thinning, whereas stress decreased the size inequality. (5) Direct stress and facilitation influence plants differently on various scales. Stress inhibited plant growth, whereas facilitation showed the opposite on an individual scale. Stress increased survival rate, whereas facilitation increased individual
-
RELATIVE COMPETITIVENESS OF GOOSEGRASS BIOTYPES AND SOYBEAN CROPS
Directory of Open Access Journals (Sweden)
JADER JOB FRANCO
2017-01-01
Full Text Available he goosegrass ( Eleusine indica (L. Gaertn is an annual plant that has a low - level resistance to glyphosate (LLRG, resulting in control failure in genetically modified soybean crops for resistance to this herbicide. Alleles related to resistance may cause changes in the plant biotype, such as inferior competitive ability. Thus, the objective of this work was to evaluated the competitive ability of soybean crops and susceptible and resistant (LLRG goosegrass biotypes. Replacement series experiments were conducted with soybean crops and goosegrass biotypes. The ratios of soybean to susceptible or resistant (LLRG goosegrass plants were 100:0, 75:25, 50:50, 25:75 and 0:100, with a total population of 481 plants m - 2 . The leaf area, plant height and shoot dry weight were evaluated at 40 days after emergence of the soybean crops and weeds. The soybean crop had superior competitive ability to the susceptible and resistant (LLRG goosegrass biotypes. The soybean crop showed similar competitive ability in both competitions, either with the susceptible or resistant (LLRG goosegrass biotypes. The intraspecific competition was more harmful to the soybean crop, while the interspecific competition caused greater damage to the goosegrass biotypes competing with the soybean crop
-
Selective inhibition of plant serine hydrolases by agrochemicals revealed by competitive ABPP.
Kaschani, Farnusch; Nickel, Sabrina; Pandey, Bikram; Cravatt, Benjamin F; Kaiser, Markus; van der Hoorn, Renier A L
2012-01-15
Organophosphate and -phosphonates and their thio derivatives are often used in agroindustry as herbicides and insecticides, but their potential off-targets in the plant are poorly investigated. Here, we use competitive activity-based protein profiling (ABPP) of serine hydrolases (SHs) to detect targets of these agrochemicals and other compounds in Arabidopsis thaliana. Using broad-range and specific probes, and by overexpression of various SHs in planta, we are able to confirm eight SH-compound interactions, including selective inhibition of carboxylesterase CXE12, prolyloligopeptidase, methylesterase MES2 and tripeptidyl peptidase TPP2. These observations can be used for the design of novel probes and selective inhibitors and may help to assess physiological effects of agrochemicals on crop plants. Copyright © 2011 Elsevier Ltd. All rights reserved.
-
International Nuclear Information System (INIS)
Martin, T.D.
1996-01-01
Staffing at US nuclear plants has been sharply reduced in recent years, as nuclear plants strive for aggressive cost reduction in a deregulating energy market. These steps have proved necessary to make nuclear plant production competitive with alternative sources. (author)
-
Segarra, Guillem; Casanova, Eva; Avilés, Manuel; Trillas, Isabel
2010-01-01
Trichoderma asperellum strain T34 has been reported to control the disease caused by Fusarium oxysporum f.sp. lycopersici (Fol) on tomato plants. To study the importance of iron concentration in the growth media for the activity and competitiveness of T34 and the pathogen, we tested four iron concentrations in the nutrient solution [1, 10, 100, and 1000 microM provided as EDTA/Fe(III)] in a biological control experiment with T34 and Fol in tomato plants. The reduction of the Fusarium-infected shoot by T34 was only significant at 10 microM Fe. We hypothesized that Fe competition is one of the key factors in the biocontrol activity exerted by T34 against Fol, as an increase in Fe concentration over 10 microM would lead to the suppression of T34 siderophore synthesis and thus inhibition of Fe competition with Fol. T34 significantly reduced the populations of Fol at all the doses of Fe assayed. In contrast, Fol enhanced the populations of T34 at 1 and 10 microM Fe. Nevertheless, several plant physiological parameters like net CO(2) assimilation (A), stomatal conductance (g(s)), relative quantum efficiency of PSII (Phi(PSII)), and efficiency of excitation energy capture by open PSII reactive centers (Fv'/Fm') demonstrated the protection against Fol damage by treatment with T34 at 100 microM Fe. The first physiological parameter affected by the disease progression was g(s). Plant dry weight was decreased by Fe toxicity at 100 and 1,000 microM. T34-treated plants had significantly greater heights and dry weights than control plants at 1,000 microM Fe, even though T34 did not reduce the Fe content in leaves or stems. Furthermore, T34 enhanced plant height even at the optimal Fe concentration (10 microM) compared to control plants. In conclusion, T. asperellum strain T34 protected tomato plants from both biotic (Fusarium wilt disease) and abiotic stress [Fe(III) toxic effects].
-
Modelling the effect of size-asymmetric competition on size inequality
DEFF Research Database (Denmark)
Rasmussen, Camilla Ruø; Weiner, Jacob
2017-01-01
Abstract The concept of size asymmetry in resource competition among plants, in which larger individuals obtain a disproportionate share of contested resources, appears to be very straightforward, but the effects of size asymmetry on growth and size variation among individuals have proved...... to be controversial. It has often been assumed that competition among individual plants in a population has to be size-asymmetric to result in higher size inequality than in the absence of competition, but here we question this inference. Using very simple, individual-based models, we investigate how size symmetry...... of competition affects the development in size inequality between two competing plants and show that increased size inequality due to competition is not always strong evidence for size-asymmetric competition. Even absolute symmetric competition, in which all plants receive the same amount of resources...
-
Directory of Open Access Journals (Sweden)
Tobias Ceulemans
Full Text Available Anthropogenic activities have severely altered fluxes of nitrogen and phosphorus in ecosystems worldwide. In grasslands, subsequent negative effects are commonly attributed to competitive exclusion of plant species following increased above-ground biomass production. However, some studies have shown that this does not fully account for nutrient enrichment effects, questioning whether lowering competition by reducing grassland productivity through mowing or herbivory can mitigate the environmental impact of nutrient pollution. Furthermore, few studies so far discriminate between nitrogen and phosphorus pollution. We performed a full factorial experiment in greenhouse mesocosms combining nitrogen and phosphorus addition with two clipping regimes designed to relax above-ground competition. Next, we studied the survival and growth of seedlings of eight common European grassland species and found that five out of eight species showed higher survival under the clipping regime with the lowest above-ground competition. Phosphorus addition negatively affected seven plant species and nitrogen addition negatively affected four plant species. Importantly, the negative effects of nutrient addition and higher above-ground competition were independent of each other for all but one species. Our results suggest that at any given level of soil nutrients, relaxation of above-ground competition allows for higher seedling survival in grasslands. At the same time, even at low levels of above-ground competition, nutrient enrichment negatively affects survival as compared to nutrient-poor conditions. Therefore, although maintaining low above-ground competition appears essential for species' recruitment, for instance through mowing or herbivory, these management efforts are likely to be insufficient and we conclude that environmental policies aimed to reduce both excess nitrogen and particularly phosphorus inputs are also necessary.
-
Economical assessment of competitive enhanced limestones for CO2 capture cycles in power plants
International Nuclear Information System (INIS)
Romeo, Luis M.; Lara, Yolanda; Lisbona, Pilar; Martinez, Ana
2009-01-01
CO 2 capture systems based on the carbonation/calcination loop have gained rapid interest due to promising carbonator CO 2 capture efficiency, low sorbent cost and no flue gases treatment is required before entering the system. These features together result in a competitively low cost CO 2 capture system. Among the key variables that influence the performance of these systems and their integration with power plants, the carbonation conversion of the sorbent and the heat requirement at calciner are the most relevant. Both variables are mainly influenced by CaO/CO 2 ratio and make-up flow of solids. New sorbents are under development to reduce the decay of their carbonation conversion with cycles. The aim of this study is to assess the competitiveness of new limestones with enhanced sorption behaviour applied to carbonation/calcination cycle integrated with a power plant, compared to raw limestone. The existence of an upper limit for the maximum average capture capacity of CaO has been considered. Above this limit, improving sorbent capture capacity does not lead to the corresponding increase in capture efficiency and, thus, reduction of CO 2 avoided cost is not observed. Simulations calculate the maximum price for enhanced sorbents to achieve a reduction in CO 2 removal cost under different process conditions (solid circulation and make-up flow). The present study may be used as an assessment tool of new sorbents to understand what prices would be competitive compare with raw limestone in the CO 2 looping capture systems. (author)
-
Directory of Open Access Journals (Sweden)
Martina Lardi
2017-08-01
Full Text Available Members of the genus Burkholderia (β-proteobacteria have only recently been shown to be able to establish a nitrogen-fixing symbiosis with several legumes, which is why they are also referred to as β-rhizobia. Therefore, very little is known about the competitiveness of these species to nodulate different legume host plants. In this study, we tested the competitiveness of several Burkholderia type strains (B. diazotrophica, B. mimosarum, B. phymatum, B. sabiae, B. symbiotica and B. tuberum to nodulate four legumes (Phaseolus vulgaris, Macroptilium atropurpureum, Vigna unguiculata and Mimosa pudica under our closely defined growth conditions. The assessment of nodule occupancy of these species on different legume host plants revealed that B. phymatum was the most competitive strain in the three papilionoid legumes (bean, cowpea and siratro, while B. mimosarum outcompeted the other strains in mimosa. The analysis of phenotypes known to play a role in nodulation competitiveness (motility, exopolysaccharide production and additional in vitro competition assays among β-rhizobial strains suggested that B. phymatum has the potential to be a very competitive legume symbiont.
-
Mycorrhiza-mediated competition between plants and decomposers drives soil carbon storage.
Averill, Colin; Turner, Benjamin L; Finzi, Adrien C
2014-01-23
Soil contains more carbon than the atmosphere and vegetation combined. Understanding the mechanisms controlling the accumulation and stability of soil carbon is critical to predicting the Earth's future climate. Recent studies suggest that decomposition of soil organic matter is often limited by nitrogen availability to microbes and that plants, via their fungal symbionts, compete directly with free-living decomposers for nitrogen. Ectomycorrhizal and ericoid mycorrhizal (EEM) fungi produce nitrogen-degrading enzymes, allowing them greater access to organic nitrogen sources than arbuscular mycorrhizal (AM) fungi. This leads to the theoretical prediction that soil carbon storage is greater in ecosystems dominated by EEM fungi than in those dominated by AM fungi. Using global data sets, we show that soil in ecosystems dominated by EEM-associated plants contains 70% more carbon per unit nitrogen than soil in ecosystems dominated by AM-associated plants. The effect of mycorrhizal type on soil carbon is independent of, and of far larger consequence than, the effects of net primary production, temperature, precipitation and soil clay content. Hence the effect of mycorrhizal type on soil carbon content holds at the global scale. This finding links the functional traits of mycorrhizal fungi to carbon storage at ecosystem-to-global scales, suggesting that plant-decomposer competition for nutrients exerts a fundamental control over the terrestrial carbon cycle.
-
Pankoke, Helga; Höpfner, Ingo; Matuszak, Agnieszka; Beyschlag, Wolfram; Müller, Caroline
2015-10-01
Plants are sessile organisms that suffer from a multitude of challenges such as abiotic stress or the interactions with competitors, antagonists and symbionts, which influence their performance as well as their eco-physiological and biochemical responses in complex ways. In particular, the combination of different stressors and their impact on plant biomass production and the plant's ability to metabolically adjust to these challenges are less well understood. To study the effects of mineral nitrogen (N) availability, interspecific competition and the association with arbuscular mycorrhizal fungi (AMF) on biomass production, biomass allocation patterns (root/shoot ratio, specific leaf area) and metabolic responses, we chose the model organism Plantago lanceolata L. (Plantaginaceae). Plants were grown in a full factorial experiment. Biomass production and its allocation patterns were assessed at harvest, and the influence of the different treatments and their interactions on the plant metabolome were analysed using a metabolic fingerprinting approach with ultra-high performance liquid chromatography coupled with time-of-flight-mass spectrometry. Limited supply of mineral N caused the most pronounced changes with respect to plant biomass and biomass allocation patterns, and altered the concentrations of more than one third of the polar plant metabolome. Competition also impaired plant biomass production, yet affected the plant metabolome to a much lesser extent than limited mineral N supply. The interaction of competition and limited mineral N supply often caused additive changes on several traits. The association with AMF did not enhance biomass production, but altered biomass allocation patterns such as the root/shoot ratio and the specific leaf area. Interestingly, we did not find significant changes in the plant metabolome caused by AMF. A targeted analysis revealed that only limited mineral N supply reduced the concentrations of one of the main target defence
-
Shen, Shicai; Xu, Gaofeng; Clements, David Roy; Jin, Guimei; Chen, Aidong; Zhang, Fudou; Kato-Noguchi, Hisashi
2015-01-28
There are a variety of ways of increasing crop diversity to increase agricultural sustainability and in turn having a positive influence on nearby natural ecosystems. Competitive crops may provide potent management tools against invasive plants. To elucidate the competitive mechanisms between a sweet potato crop (Ipomoea batatas) and an invasive plant, mile-a-minute (Mikania micrantha), field experiments were carried out in Longchuan County of Yunnan Province, Southwest China, utilizing a de Wit replacement series. The trial incorporated seven ratios of sweet potato and mile-a-minute plants in 25 m(2) plots. In monoculture, the total biomass, biomass of adventitious root, leafstalk length, and leaf area of sweet potato were all higher than those of mile-a-minute, and in mixed culture the plant height, branch, leaf, stem node, adventitious root, flowering and biomass of mile-a-minute were suppressed significantly (P competition was less than interspecific competition. The competitive balance index of sweet potato demonstrated a higher competitive ability than mile-a-minute. Except pH, other soil nutrient contents of initial soil (CK) were significantly higher than those of seven treatments. The concentrations of soil organic matter, total N, total K, available N, available P, available K, exchange Ca, exchange Mg, available Mn, and available B were significantly greater (P competition of sweet potato in the mixture. Evidently sweet potato has a competitive advantage in terms of plant growth characteristics and greater absorption of soil nutrients. Thus, planting sweet potato is a promising technique for reducing infestations of mile-a-minute, providing weed management benefits and economic returns from harvest of sweet potatoes. This study also shows the potential value of replacement control methods which may apply to other crop-weed systems or invaded natural ecosystems.
-
New nuclear power plants and the electricity market competition
International Nuclear Information System (INIS)
Ruska, M.; Koreneff, G.
2009-11-01
The study assesses the effects the different nuclear power plant projects would have on crossownership, market concentration and market power in electricity market. The analyses are given both for Finnish and Nordic power markets. The authors feel that the electricity market should primarily be viewed as a common Nordic market in the future. During 2000 to 2008 the hours when Finland was an own price area ranged from 1 % to 29 % as annual averages. In the future it will be more and more seldom that Finland will become an own deficit price area, because the cross-border transmission capacity to Sweden will increase as will Finnish electricity production capacity. In addition, the extension of Nord Pool to the Baltic will increase the size of the market. The ownership of power plants is typically organized through power share companies in Finland. Two of the three nuclear power plant projects are joint ventures with several electricity producers and consumers. The current ownership relations and what effects the new projects might have on them were analyzed in this study. The competitiveness of different electricity production forms in the future was assessed using different market scenarios based on varying demand expectations. The capacity structure was assumed to stay quite unchanged, where the biggest change is expected to come from new renewable power capacity due to EU targets. Conventional condensing power production will decrease and Nordic electricity exports will increase in the future. The market concentration would increase in Finland with new nuclear plants, the most if Fortum were the builder. Vattenfall has a decidedly larger electricity production in the Nordic countries than Fortum, and Vattenfall's capacity would be unchanged by the new planned nuclear plants. The nuclear power plant projects do not therefore increase market concentration significantly on a Nordic level. Nuclear power is not used for day or hour regulation in Finland, which means
-
Electricity market competition and nuclear power
International Nuclear Information System (INIS)
Varley, C.; Paffenbarger, J.
1999-01-01
Throughout the world, the Organization for Economic Cooperation and Development (OECD) member countries' governments are promoting competitive electricity markets. In particular, there is a move away from administrative price-setting by government institutions to market price-setting through the introduction of competition. Today this is often focused on competition in generation. However, competition among final electricity suppliers and distributors to provide effective consumer choice is a further step that governments are likely to pursue as experience with market reform grows. This competitive environment will undoubtedly impact upon the nuclear generation industry. Competition will provide an opportunity to reinvigorate nuclear power; it will improve the transparency of energy policy-making and the policy framework for nuclear power; it will spur innovation in existing plants and help prospects for new plant build; and provide a strong impetus for cost reduction and innovation. This paper discusses these issues in detail. It looks at the potential benefits and challenges to the nuclear generation industry arising from an increasingly competitive market. (author)
-
Separation of allelopathy from resource competition using rice/barnyardgrass mixed-cultures.
Directory of Open Access Journals (Sweden)
Hai Bin He
Full Text Available Plant-plant interference is the combined effect of allelopathy, resource competition, and many other factors. Separating allelopathy from resource competition is almost impossible in natural systems but it is important to evaluate the relative contribution of each of the two mechanisms on plant interference. Research on allelopathy in natural and cultivated plant communities has been hindered in the absence of a reliable method that can separate allelopathic effect from resource competition. In this paper, the interactions between allelopathic rice accession PI312777, non-allelopathic rice accession Lemont and barnyardgrass were explored respectively by using a target (rice-neighbor (barnyardgrass mixed-culture in hydroponic system. The relative competitive intensity (RCI, the relative neighbor effect (RNE and the competitive ratio (CR were used to quantify the intensity of competition between each of the two different potentially allelopathic rice accessions and barnyardgrass. Use of hydroponic culture system enabled us to exclude any uncontrolled factors that might operate in the soil and we were able to separate allelopathy from resource competition between each rice accession and barnyardgrass. The RCI and RNE values showed that the plant-plant interaction was positive (facilitation for PI312777 but that was negative (competition for Lemont and barnyardgrass in rice/barnyardgrass mixed-cultures. The CR values showed that one PI312777 plant was more competitive than 2 barnyardgrass plants. The allelopathic effects of PI312777 were much more intense than the resource competition in rice/barnyardgrass mixed cultures. The reverse was true for Lemont. These results demonstrate that the allelopathic effect of PI312777 was predominant in rice/barnyardgrass mixed-cultures. The most significant result of our study is the discovery of an experimental design, target-neighbor mixed-culture in combination with competition indices, can successfully
-
Nuclear power in the competitive environment
International Nuclear Information System (INIS)
Schlissel, D.A.
1995-01-01
Nuclear power was originally promoted as being able to produce electricity that would be open-quotes too cheap to meter.close quotes However, large construction cost overruns and rapidly rising operating costs caused many nuclear power plants instead to be very expensive sources of electricity. As a result, many nuclear utilities will face increasing cost pressures in the future competitive environment from lower-cost producers. In fact, the threat to nuclear utilities is so severe that many industry analysts are projecting that more that $70 billion of the utilities' remaining investments in nuclear plants will be open-quotes stranded,close quotes i.e., unrecoverable in the competitive environment. Others in the industry have speculated that many of the 150 major U.S. electric utilities, a large number of which are nuclear, could be swept away by competition, leaving fewer than fifty utilities. This paper will examine how utilities are attempting to improve the cost competitiveness of operating today's nuclear power plants. It will also identify some of the potential consequences of competition for nuclear power and the regulatory role of the U.S. Nuclear Regulatory Commission (NRC). Finally, this paper will address how the changing power markets will affect the prospects for the next generation of nuclear power plants
-
Thinking outside the mainstream; Canadian NGL plants face global competition and decline
International Nuclear Information System (INIS)
Jaremko, D.
2005-01-01
The nature of the natural gas liquids (NGL) market, and the future prospects of the Canadian NGL industry are discussed. In the short term, demand for NGLs like propane, ethane and condensate is up, the supply picture is good, and the profit margins for Canadian gas plants look positive. At the same time, staying competitive with oil-based naptha and global NGL imports is expected to become more difficult, and the longer term future is far from being without significant problems. Competition is likely to grow as the Canadian energy industry is increasingly looking to heavy oil and bitumen to meet coming energy demand needs; given that it takes about a thousand cubic feet of natural gas to produce each barrel of oil from the oilsands, serious impact on natural gas availability is inevitable, which in turn will affect the supply of NGLs. To reduce the pressure on natural gas, there is an urgent need to come up with other sources of heavy oil production; various options such as coal, nuclear power and even coal gasification are being investigated, albeit too slowly to arrest the decline of North American conventional gas production that started in 2001. Expert opinion is that the real hope for the NGL industry, as well as for the future of natural gas, is the stranded reserve in the Arctic which, however, is expected to flow soon from the Mackenzie Delta. While Arctic gas is expected to negate the impact of waterborne imports from other countries by the USA, the absence of overseas imports does not alter the fact that North America as a petrochemical manufacturer is no longer as competitive with other countries as it once was. The unpleasant reality is that new petrochemical plants are more likely to be built in the Far East and China, where both the feedstock as well as the labour, are much cheaper. 3 photos
-
International Nuclear Information System (INIS)
Galic, T.; Tomsic, Z.
2012-01-01
Production of electricity from renewable energy sources and energy-efficient power sources to be connected to the electricity distribution network is still not competitive with electricity production from conventional sources of electricity. A powerful technological development of distributed energy sources and technologies for electricity storage has reduced their production costs, production costs of electricity from distributed energy sources, the costs of simultaneous production of electricity and thermal energy from cogeneration distributed energy sources and thus has facilitated their increased use in practice. It also allows them to interconnect systems such as virtual power plants in order to achieve full economic feasibility of their use. Current electricity and gas customers, now also in the role of small power producers, interconnected by virtual power plants operators, in addition to buying electricity and gas on retail markets for electricity and gas, will be able to sell electricity and new energy services also on wholesale electricity markets. Development and application of new distributed technologies will enable the production of new quantities of electricity which will increase the competitiveness of electricity producers, competitiveness of electricity suppliers of end-customers and elasticity of supply and demand in the electricity market. These processes will also increase the efficiency of the entire systems of electricity supply and of the gas supply systems.(author)
-
Varga, S; Vega-Frutis, R; Kytöviita, M-M
2017-03-01
Plants usually interact with other plants, and the outcome of such interaction ranges from facilitation to competition depending on the identity of the plants, including their sexual expression. Arbuscular mycorrhizal (AM) fungi have been shown to modify competitive interactions in plants. However, few studies have evaluated how AM fungi influence plant intraspecific and interspecific interactions in dioecious species. The competitive abilities of female and male plants of Antennaria dioica were examined in a greenhouse experiment. Females and males were grown in the following competitive settings: (i) without competition, (ii) with intrasexual competition, (iii) with intersexual competition, and (iv) with interspecific competition by Hieracium pilosella - a plant with similar characteristics to A. dioica. Half of the pots were grown with Claroideoglomus claroideum, an AM fungus isolated from the same habitat as the plant material. We evaluated plant survival, growth, flowering phenology, and production of AM fungal structures. Plant survival was unaffected by competition or AM fungi. Competition and the presence of AM fungi reduced plant biomass. However, the sexes responded differently to the interaction between fungal and competition treatments. Both intra- and interspecific competition results were sex-specific, and in general, female performance was reduced by AM colonization. Plant competition or sex did not affect the intraradical structures, extraradical hyphae, or spore production of the AM fungus. These findings suggest that plant sexual differences affect fundamental processes such as competitive ability and symbiotic relationships with AM fungi. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.
-
DEFF Research Database (Denmark)
Gallandt, Eric R.; Weiner, Jacob
2015-01-01
importantly, weed density and time of emergence relative to the crop. Practices that (1) reduce the density of weeds, (2) maximise occupation of space or uptake of resources by the crop or (3) establish an early-season size advantage of the crop over the weeds will minimise the competitive effects of weeds...... on crops. Longer term management of crop–weed competition can be achieved through crop rotations, specifically crop sequences that reduce the weed seed bank, and therefore seedling density, and prevent proliferation of perennial weeds. Key ConceptsKey Concepts * Plant growth requires sunlight, water...... an early-season competitive advantage to the crop and (3) maximising resource capture by the crop using competitive species, competitive cultivars, high sowing densities, optimal spatial arrangement, intercropping complimentary species or transplanting....
-
Common mycelial networks impact competition in an invasive grass.
Workman, Rachael E; Cruzan, Mitchell B
2016-06-01
Mycorrhizal hyphal complexes can connect multiple host plants to form common mycelial networks (CMNs) that may affect plant competitive outcomes and community composition through differential resource allocation. The impacts of CMN interactions on invasive plants are not well understood and could be crucial to the understanding of invasive plant establishment and success. We grew the invasive grass Brachypodium sylvaticum in intra- and interspecific pairings with native grass Bromus vulgaris in a greenhouse and controlled for the effects of CMN and root interactions by manipulating the belowground separation between competitors. Comparison of plant growth in pots that allowed CMN interactions and excluded root competition and vice versa, or both, allowed us to delineate the effects of network formation and root competition on invasive plant establishment and performance. Brachypodium sylvaticum grown in pots allowing for only hyphal interactions, but no root competition, displayed superior growth compared with conspecifics in other treatments. Invasive performance was poorest when pairs were not separated by a barrier. Shoot nitrogen content in B. sylvaticum was higher in mycorrhizal plants only when connections were allowed between competitors. Our results indicate that the presence of CMN networks can have positive effects on B. sylvaticum establishment and nutrient status, which may affect plant competition and invasion success. © 2016 Botanical Society of America.
-
Competitive breeder power plants
International Nuclear Information System (INIS)
Winkleblack, R.K.
1984-01-01
To utilize the fissile material that is accumulating in the utilities' spent fuel pools, breeder plants must be less expensive than current LWR costs (or utilities will not buy nuclear plants in the near future) and also be highly reliable. The fundamental differences between LWRs and LMFBRs are discussed and recommendations are made for making the most of these differences to design a superior breeder plant that can sell in the future, opening the way to U.S. utilities becoming self-sufficient for fuel supply for centuries
-
Lessons from plant management for achieving economic competitiveness for evolutionary reactors
International Nuclear Information System (INIS)
Andognini, G.
1999-01-01
Ontario Hydro, Canada's largest utility, has 20 nuclear power units of the CANDU design with a total design power of 15, 020 Electrical MW or about half of the total generating capacity. The performance of these plants, which were installed between the 1970s and early 1990s, was initially very good but worsened in recent years and the regulator expressed concerns about declining safety standards. In early 1997, an external Nuclear Performance Advisory Group led by Mr G. Carl Andognini was established and conducted an intensive assessment of the nuclear operation. That assessment ranked the operation of Ontario Hydro's plants as m inimally acceptable , noting a number of causes such as: lack of management leadership and accountability; poor safety culture; inadequate training; lack of configuration management; and, deficient organization. A recovery program is now underway, involving the laying-up of eight units to free resources to upgrade the remaining twelve. A number of lessons that can be drawn from the Ontario Hydro experience are presented. The key lessons include: the importance of having the light people, with the right qualifications in the right place, at the right time; the need for all staff to have a questioning attitude and to be committed to a s afety culture ; configuration management is essential - knowledge of the status of the plant must be maintained and all documentation kept up to date; maintenance must be given high priority and be provided adequate resources: defined standards are needed for the conduct of all work; the Directors (or equivalent) and senior management must understand the plant and appreciate the consequences of their decisions and actions. The paper concludes that good new designs are not sufficient by themselves to achieve economically competitive and safe nuclear plants - a high standard of operation and maintenance is also necessary throughout the life of the plants. (author)
-
Directory of Open Access Journals (Sweden)
Ana Novoa
Full Text Available Does Carpobrotus edulis have an impact on native plants? How do C. edulis' soil residual effects affect the maintenance of native populations? What is the extent of interspecific competition in its invasion process? In order to answer those questions, we established pure and mixed cultures of native species and C. edulis on soil collected from invaded and native areas of Mediterranean coastal dunes in the Iberian Peninsula. We examined the impact of the invader on the germination, growth and survival of seeds and adult plants of two native plant species (Malcolmia littorea (L. R.Br, and Scabiosa atropurpurea L. growing with ramets or seeds of C. edulis. Residual effects of C. edulis on soils affected the germination process and early growth of native plants in different ways, depending on plant species and density. Interspecific competition significantly reduced the germination and early growth of native plants but this result was soil, density, timing and plant species dependent. Also, at any density of adult individuals of C. edulis, established native adult plants were not competitive. Moreover, ramets of C. edulis had a lethal effect on native plants, which died in a short period of time. Even the presence of C. edulis seedlings prevents the recruitment of native species. In conclusion, C. edulis have strong negative impacts on the germination, growth and survival of the native species M. littorea and S. atropurpurea. These impacts were highly depended on the development stages of native and invasive plants. Our findings are crucial for new strategies of biodiversity conservation in coastal habitats.
-
Novoa, Ana; González, Luís
2014-01-01
Does Carpobrotus edulis have an impact on native plants? How do C. edulis’ soil residual effects affect the maintenance of native populations? What is the extent of interspecific competition in its invasion process? In order to answer those questions, we established pure and mixed cultures of native species and C. edulis on soil collected from invaded and native areas of Mediterranean coastal dunes in the Iberian Peninsula. We examined the impact of the invader on the germination, growth and survival of seeds and adult plants of two native plant species (Malcolmia littorea (L.) R.Br, and Scabiosa atropurpurea L.) growing with ramets or seeds of C. edulis. Residual effects of C. edulis on soils affected the germination process and early growth of native plants in different ways, depending on plant species and density. Interspecific competition significantly reduced the germination and early growth of native plants but this result was soil, density, timing and plant species dependent. Also, at any density of adult individuals of C. edulis, established native adult plants were not competitive. Moreover, ramets of C. edulis had a lethal effect on native plants, which died in a short period of time. Even the presence of C. edulis seedlings prevents the recruitment of native species. In conclusion, C. edulis have strong negative impacts on the germination, growth and survival of the native species M. littorea and S. atropurpurea. These impacts were highly depended on the development stages of native and invasive plants. Our findings are crucial for new strategies of biodiversity conservation in coastal habitats. PMID:25210924
-
Novoa, Ana; González, Luís
2014-01-01
Does Carpobrotus edulis have an impact on native plants? How do C. edulis' soil residual effects affect the maintenance of native populations? What is the extent of interspecific competition in its invasion process? In order to answer those questions, we established pure and mixed cultures of native species and C. edulis on soil collected from invaded and native areas of Mediterranean coastal dunes in the Iberian Peninsula. We examined the impact of the invader on the germination, growth and survival of seeds and adult plants of two native plant species (Malcolmia littorea (L.) R.Br, and Scabiosa atropurpurea L.) growing with ramets or seeds of C. edulis. Residual effects of C. edulis on soils affected the germination process and early growth of native plants in different ways, depending on plant species and density. Interspecific competition significantly reduced the germination and early growth of native plants but this result was soil, density, timing and plant species dependent. Also, at any density of adult individuals of C. edulis, established native adult plants were not competitive. Moreover, ramets of C. edulis had a lethal effect on native plants, which died in a short period of time. Even the presence of C. edulis seedlings prevents the recruitment of native species. In conclusion, C. edulis have strong negative impacts on the germination, growth and survival of the native species M. littorea and S. atropurpurea. These impacts were highly depended on the development stages of native and invasive plants. Our findings are crucial for new strategies of biodiversity conservation in coastal habitats.
-
The competitiveness of biofuels in heat and power production
International Nuclear Information System (INIS)
Kosunen, P.; Leino, P.
1995-01-01
The paper showed that natural gas is the most competitive fuel in all the energy production alternatives under review, ie both in separate heat production and electricity generation and in combined heat and power production. Even though the heavy fuel oil taxes have grown more rapidly than taxes on domestic fuels, oil continues to be cheaper than solid fuels in heating and steam plants. According to the feasibility calculations made, combined heat and power production is the least-cost production form of electricity, and the larger the plant unit, the lower the cost. Looking to the future, in respect of merely the development in fuel taxes the competitiveness of domestic fuels will improve markedly if the taxation structure remains unchanged. It seems that at smaller points of consumption, such as heating and steam plants and small-scale power plants, fuel chips would be the most competitive fuel. In larger units, such as heat and power production plants and condensing power plants, fuel peat, primarily milled peat, would be the most competitive. The competitiveness of fuel chips at larger plants will probably be limited by the supply of sufficient volumes from such an area where the delivery costs would not raise the price of fuel chips too high. Coal would remain competitive only if the real import price of coal rose clearly more slowly than the real prices of domestic fuels. It seems that heavy fuel oil will be used only as a start-up, support and back-up fuel. Evaluating the future competitiveness of natural gas is difficult, since the impact of new pipeline investments on the price of natural gas is not known
-
Temperature-dependent performance of competitive native and alien invasive plant species
Song, Uhram
2017-10-01
To assess the likely impacts of environmental change, the responses of two well-known invasive plant species, native Pueraria lobata and alien Humulus japonicus, to differences in growth temperature were studied in South Korea. Habitat preferences, physiological responses such as photosynthetic rates and chlorophyll contents, growth rates, and nutrient contents were quantified for each species. A competition experiment was conducted to evaluate the temperature preferences of the two species. All results indicated that the alien species H. japonicus can take advantage of elevated temperatures (35 °C) to enhance its competitive advantage against the native species P. lobata. While H. japonicus took advantage of elevated temperatures and preferred high-temperature areas, P. lobata showed reduced performance and dominance in high-temperature areas. Therefore, in future, due to global warming and urbanization, there are possibilities that H. japonicus takes advantage of elevated temperature against P. lobata that could lead to increased H. japonicus coverage over time. Therefore, consistent monitoring of both species especially where P. lobata is dominated are required because both species are found in every continents in the world. Controlling P. lobata requires thorough inspection of H. japonicus presence of the habitat in advance to prevent post P. lobata management invasion of H. japonicus.
-
Time-lagged intraspecific competition in temporally separated cohorts of a generalist insect.
Barnes, Elizabeth E; Murphy, Shannon M
2018-03-01
Competition can have far-reaching consequences for insect fitness and dispersion. Time-lagged interspecific competition is known to negatively affect fitness, yet time-lagged intraspecific competition is rarely studied outside of outbreak conditions. We tested the impact of competition between larval cohorts of the western tent caterpillar (Malacosoma californicum) feeding on chokecherry (Prunus virginiana). We reared larvae on host plants that either had or did not have feeding damage from tent caterpillars the previous season to test the bottom-up fitness effects of intraspecific competition. We measured host-plant quality to test potential mechanisms for bottom-up effects and conducted field oviposition surveys to determine if female adult tent caterpillars avoided host plants with evidence of prior tent caterpillar presence. We found that time-lagged intraspecific competition impacted tent caterpillar fitness by reducing female pupal mass, which is a predictor of lifetime fitness. We found that plants that had been fed upon by tent caterpillars the previous season had leaves that were significantly tougher than plants that had not been fed upon by tent caterpillars, which may explain why female tent caterpillars suffered reduced fitness on these plants. Finally, we found that there were fewer tent caterpillar egg masses on plants that had tent caterpillars earlier in the season than plants without tent caterpillars, which suggests that adult females avoid these plants for oviposition. Our results confirm that intraspecific competition occurs among tent caterpillars and suggests that time-lagged intraspecific competition has been overlooked as an important component of insect fitness.
-
Costs and competitiveness of nuclear electricity
International Nuclear Information System (INIS)
Bennett, L.L.; Woite, G.
1995-01-01
The experienced and projected future construction costs and electricity generation costs of nuclear and fossil fired power plants are reviewed and compared. On the basis of actual operating experience, nuclear power has been demonstrated to be economically competitive with other base load generation options, and international studies project that this economic competitiveness will be largely maintained in the future, over a range of conditions and in a number of countries. However, retaining and improving this competitiveness position requires concerted efforts to ensure that nuclear plants are constructed within schedule and budget, and are operated reliably and efficiently. Relevant cost impacting factors are identified, and conclusions for successful nuclear power plant construction and operation are drawn. The desire to attain sustainable development with balanced resource use and control of the environmental and climatic impacts of energy systems could lead to renewed interest in nuclear power as an energy source that does not emit greenhouse gases, thus contributing to a revival of the nuclear option. In this regard also, mitigation of emissions from fossil fuelled power plants could lead to restrictions of fossil fuel use and/or result in higher costs of fossil based generation, thus improving the economic competitiveness of nuclear power. (author). 19 refs, 7 figs, 2 tabs
-
The renewal of hydroelectric concessions in competitive call
International Nuclear Information System (INIS)
2013-01-01
This document discusses various issues associated with the planned competitive call on the French hydraulic power plants. The principles of this competitive call for hydroelectric concessions are first addressed: administrative regime of concessions, competitive call process, criteria of selection of the concession holder, case of 'concession of valleys', potential competitors. It outlines and discusses the difficulties of this competitive call: France is the single country to implement this procedure; it concerns a national asset; it questions the guarantee of a future use of equipment at best for the energy benefits of French consumers; the competitive call is a nice idea indeed but extremely complex. A note discusses the profitability aspects of Plants for Transfer of Energy by Pumping
-
Huang, Fangfang; Lankau, Richard; Peng, Shaolin
2018-04-01
Coevolution can promote long-term coexistence of two competing species if selection acts to reduce the fitness inequality between competitors and/or strengthen negative frequency dependence within each population. However, clear coevolution between plant competitors has been rarely documented. Plant invasions offer opportunities to capture the process of coevolution. Here we investigated how the developing relationship between an invasive forb, Alliaria petiolata, and a native competitor, Pilea pumila, may affect their long-term coexistence, by testing the competitive effects of populations of varying lengths of co-occurrence on each other across a chronosequence of invasion history. Alliaria petiolata and P. pumila tended to develop greater tolerance to competition over invasion history. Their coexistence was promoted more by increases in stabilizing relative to equalizing processes. These changes likely stem in part from reductions in allelopathic traits in the invader and evolution of tolerance in the native. These results suggested that some native species can evolve tolerance against the competitive effects of strong invaders, which likely promoted their persistence in invaded communities. However, the potential for coevolutionary rescue of competing populations is likely to vary across native species, and evolutionary processes should not be expected to compensate for the ecological consequences of exotic invasions. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.
-
Rosconi, Federico; Trovero, María F; de Souza, Emanuel M; Fabiano, Elena
2016-09-01
Herbaspirillum seropedicae Z67 is a diazotrophic endophyte able to colonize the interior of many economically relevant crops such as rice, wheat, corn and sorghum. Under iron-deficient conditions, this organism secretes serobactins, a suite of lipopetide siderophores. The role of siderophores in the interaction between endophytes and their plant hosts are not well understood. In this work, we aimed to determine the importance of serobactins-mediated iron acquisition systems in the interaction of H. seropedicae with rice plants. First we provide evidence, by using a combination of genome analysis, proteomic and genetic studies, that the Hsero_2345 gene encodes a TonB-dependent receptor involved in iron-serobactin complex internalization when iron bioavailability is low. Our results show that survival of the Hsero_2345 mutant inside rice plants was not significantly different from that of the wild-type strain. However, when plants were co-inoculated at equal ratios with the wild-type strain and with a double mutant defective in serobactins synthesis and internalization, recovery of mutant was significantly impaired after 8 days post-inoculation. These results demonstrate that serobactins-mediated iron acquisition contributes to competitive fitness of H. seropedicae inside host plants. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.
-
International Nuclear Information System (INIS)
Taylor, D.; Flaman, L.; Beigie, C.
1992-01-01
Energy efficiency-related programs in two Canadian provinces are reviewed. The Ontario Ministry of Energy has implemented programs to improve industrial energy efficiency in order to contribute to future economic growth. Since 1987, the Industrial Energy Services Program provides energy audits, feasibility analysis grants, and project engineering grants for energy efficiency improvements. Results show that an industrial plant can cut its energy costs by an average of 10% with the proper help. To minimize electricity costs, Ontario Hydro has a demand management program that offers a combination of financial assistance for energy conservation measures, rate incentives, standards and regulation, and fuel substitution. Results in 1992 show 250 MW in saved and shifted load. In Alberta, a TransAlta Utilities program in supply side management has the objective of maximizing the production potential of existing plants. The resulting benefit is improved electric power production efficiency that leads to increased competitiveness. Side benefits include delay of new plant construction, reduced coal consumption, and reduction in greenhouse gas emissions. Finally, Canada's economic competitiveness is reviewed historically and measures to improve this competitiveness are suggested. A new national policy strategy would include gradual elimination of all import tariffs, optimization of natural resources, securing energy availability at prices at or below world levels, and becoming a leader in transportation and communications. 1 fig., 1 tab
-
Zhang, Xiufeng; Liu, Zhengwen
2011-01-01
The competition between submersed plants has been recognized as an important factor influencing the structure of plant communities in shallow lakes. The ability of different species to take up and store nutrients from the surrounding ambience varies, and hence plant community structure might be expected to affect the cycling of nutrients in lake ecosystems. In this study, the uptake of phosphorus by Hydrilla verticillata and Vallisneria natans was studied and compared in monoculture and competitive mixed-culture plantings. Results showed that for both studied species the phosphorus concentrations of different tissues and of whole plants was unaffected by competition. However, the quantity of phosphorus accumulated by whole plants of H. verticillata was significantly higher in mixture culture than in monoculture, while that of V. natans was lower in the mixed culture. The results indicated that H. verticillata has a competitive advantage over V. natans, when the two species are grown in competition, and is able to accumulate a greater quantity of phosphorus.
-
Relative competitiveness of soybean cultivars with barnyardgrass
Directory of Open Access Journals (Sweden)
Marlon Ouriques Bastiani
Full Text Available ABSTRACT The aim of this work was to evaluate the competitiveness between soybean cultivars and barnyardgrass, based on morphological and physiological characteristics of species. The experiments were conducted in completely randomized experimental design, with 4 replications. In the first study, for both soybean and barnyardgrass, it was determined the population of plants in which shoot dry matter became constant and independent of the population (16 plants∙pot−1 or 400 plants∙m−2. In the second study, 2 experiments were conducted to evaluate the competitiveness of BMX Apolo RR and BMX Potência RR soybean cultivars with barnyardgrass plants, both carried out in replacement series under different proportions of plants∙pot−1 (100:0; 75:25; 50:50; 25:75 and 0:100 between the crop and the weed. The analysis of the species competitiveness was determined through diagrams applied to replacement series experiments and use of relative competitiveness indexes. At 44 days after the emergence of species, the physiological and morphological parameters of the crop and the weed were evaluated. The BMX Apolo RR and BMX Potência RR soybean cultivars show similar competitiveness when competing with the barnyardgrass; therefore, the ability of one species to interfere on another is equivalent. For plant height, barnyardgrass displays higher competitiveness compared to BMX Apolo RR, with early cycle and short height. The intraspecific competition is more important to barnyardgrass than interspecific competition with soybean cultivars, resulting in negative effects on the morphological and physiological characteristics of species.
-
Poon, Gary T; Maherali, Hafiz
2015-01-01
The widespread invasion of the nonmycorrhizal biennial plant, Alliaria petiolata in North America is hypothesized to be facilitated by the production of novel biochemical weapons that suppress the growth of mycorrhizal fungi. As a result, A. petiolata is expected to be a strong competitor against plant species that rely on mycorrhizal fungi for nutrient uptake services. If A. petiolata is also a strong competitor for soil resources, it should deplete nutrients to levels lower than can be tolerated by weaker competitors. Because the negative effect of losing the fungal symbiont for mycorrhizal plants is greatest when nutrients are low, the ability of A. petiolata to simultaneously suppress fungi and efficiently take up soil nutrients should further strengthen its competitive ability against mycorrhizal plants. To test this hypothesis, we grew 27 mycorrhizal tree, forb and grass species that are representative of invaded habitats in the absence or presence of competition with A. petiolata in soils that had previously been experimentally planted with the invader or left as a control. A history of A. petiolata in soil reduced plant available forms of nitrogen by >50% and phosphorus by 17% relative to control soil. Average mycorrhizal colonization of competitor species was reduced by >50% in A. petiolata history versus control soil. Contrary to expectations, competition between A. petiolata and other species was stronger in control than history soil. The invader suppressed the biomass of 70% of competitor species in control soil but only 26% of species in history soil. In addition, A. petiolata biomass was reduced by 56% in history versus control soil, whereas the average biomass of competitor species was reduced by 15%. Thus, our results suggest that the negative effect of nutrient depletion on A. petiolata was stronger than the negative effect of suppressing mycorrhizal colonization on competitor species. These findings indicate that the inhibitory potential of A
-
The role of nuclear power in the new competitive era
International Nuclear Information System (INIS)
Pryor, C.W.
1998-01-01
As power generators around the world grapple with the challenges of deregulation and competition, there are those who suggest that ownership of an operating nuclear power plant may prove to be a liability. This is not the case for most plants. On the contrary, nuclear facilities that perform well will be important assets in competitive markets, whether as sources of competitively priced electricity, or as strategic factors in mergers and acquisitions. And, as the world focuses renewed attention on global climate change and the reduction of greenhouse gas emissions, nuclear power's significant environmental benefits further enhances its continued viability. The emergence of competitive markets will create a period of tremendous opportunity and enhanced value for nuclear plants. Nuclear plants, large coal plants, and hydro are the only types that can produce power at the bus bar with production costs close to one cent per kilowatt-hour. The challenge for all nuclear plants is to reduce costs and improve performance in order to improve their net earnings stream. Prospects for dramatic reductions are very high. In recent years, average nuclear plant performance figures worldwide have improved rapidly and substantially, and average costs are dropping. How will nuclear plants compare with alternative energy sources in an era of heightened competition? To evaluate nuclear plants in a competitive environment, this paper will look at three key areas: capital costs; operation and maintenance costs; and fuel costs, including spent fuel issues. The paper will examine innovative strategies to deal with capital or 'sunk costs' such as write-downs through securitization and regional operating companies, and will also focus on best practices in O and M and fuel where all nuclear plants have the potential to move to 'best in class'. The lessons that every nuclear plant can learn from other plants can contribute significantly to the performance improvement process. What has been
-
W.J. Mattson; R. Julkunen-Tiitto; D.A. Herms
2005-01-01
Rising levels of atmospheric CO2 can alter plant growth and partitioning to secondary metabolites. The protein competition model (PCM) and the extended growth/differentiation balance model (GDBe) are similar but alternative models that address ontogenetic and environmental effects on whole-plant carbon partitioning to the...
-
2012-01-01
Background Induced defense responses to herbivores are generally believed to have evolved as cost-saving strategies that defer the fitness costs of defense metabolism until these defenses are needed. The fitness costs of jasmonate (JA)-mediated defenses have been well documented. Those of the early signaling units mediating induced resistance to herbivores have yet to be examined. Early signaling components that mediate herbivore-induced defense responses in Nicotiana attenuata, have been well characterized and here we examine their growth and fitness costs during competition with conspecifics. Two mitogen-activated protein kinases (MAPKs), salicylic acid (SA)-induced protein kinase (SIPK) and wound-induced protein kinase (WIPK) are rapidly activated after perception of herbivory and both kinases regulate herbivory-induced JA levels and JA-mediated defense metabolite accumulations. Since JA-induced defenses result in resource-based trade-offs that compromise plant productivity, we evaluated if silencing SIPK (irSIPK) and WIPK (irWIPK) benefits the growth and fitness of plants competiting with wild type (WT) plants, as has been shown for plants silenced in JA-signaling by the reduction of Lipoxygenase 3 (LOX3) levels. Results As expected, irWIPK and LOX3-silenced plants out-performed their competing WT plants. Surprisingly, irSIPK plants, which have the largest reductions in JA signaling, did not. Phytohormone profiling of leaves revealed that irSIPK plants accumulated higher levels of SA compared to WT. To test the hypothesis that these high levels of SA, and their presumed associated fitness costs of pathogen associated defenses in irSIPK plants had nullified the JA-deficiency-mediated growth benefits in these plants, we genetically reduced SA levels in irSIPK plants. Reducing SA levels partially recovered the biomass and fitness deficits of irSIPK plants. We also evaluated whether the increased fitness of plants with reduced SA or JA levels resulted from
-
Weed-biocontrol insects reduce native-plant recruitment through second-order apparent competition.
Pearson, Dean E; Callaway, Ragan M
2008-09-01
Small-mammal seed predation is an important force structuring native-plant communities that may also influence exotic-plant invasions. In the intermountain West, deer mice (Peromyscus maniculatus) are prominent predators of native-plant seeds, but they avoid consuming seeds of certain widespread invasives like spotted knapweed (Centaurea maculosa). These mice also consume the biological-control insects Urophora spp. introduced to control C. maculosa, and this food resource substantially increases deer mouse populations. Thus, mice may play an important role in the invasion and management of C. maculosa through food-web interactions. We examined deer mouse seed predation and its effects on seedling emergence and establishment of a dominant native grass, Pseudoroegneria spicata, and forb, Balsamorhiza sagittata, in C. maculosa-invaded grasslands that were treated with herbicide to suppress C. maculosa or left untreated as controls. Deer mice readily took seeds of both native plants but removed 2-20 times more of the larger B. sagittata seeds than the smaller P. spicata seeds. Seed predation reduced emergence and establishment of both species but had greater impacts on B. sagittata. The intensity of seed predation corresponded with annual and seasonal changes in deer mouse abundance, suggesting that abundance largely determined mouse impacts on native-plant seeds. Accordingly, herbicide treatments that reduced mouse abundance by suppressing C. maculosa and its associated biocontrol food subsidies to mice also reduced seed predation and decreased the impact of deer mice on B. sagittata establishment. These results provide evidence that Urophora biocontrol agents may exacerbate the negative effects of C. maculosa on native plants through a form of second-order apparent competition-a biocontrol indirect effect that has not been previously documented. Herbicide suppressed C. maculosa and Urophora, reducing mouse populations and moderating seed predation on native plants
-
Germination phenology determines the propensity for facilitation and competition.
Leverett, Lindsay D
2017-09-01
A single plant can interact both positively and negatively with its neighbors through the processes of facilitation and competition, respectively. Much of the variation in the balance of facilitation and competition that individuals experience can be explained by the degree of physical stress and the sizes or ages of plants during the interaction. Germination phenology partly controls both of these factors, but its role in defining the facilitation-competition balance has not been explicitly considered. I performed an experiment in a population of the winter annual Arabidopsis thaliana (Brassicaceae) to test whether germinating during physically stressful periods leads to facilitation while germinating during periods that promote growth and reproduction leads to competition. I manipulated germination and neighbor presence across two years in order to quantify the effects of the local plant community on survival, fecundity, and total fitness as a function of germination phenology. Neighbors increased survival when germination occurred under conditions that were unsuitable for survival, but they reduced fecundity in germinants that were otherwise the most fecund. Later germination was associated with facilitation in the first year but competition in the second year. These episodes of facilitation and competition opposed each other, leading to no net effect of neighbors when averaged over all cohorts. These results indicate that variation in germination timing can explain some of the variation in the facilitation-competition balance in plant communities. © 2017 by the Ecological Society of America.
-
Morphological response to competition for light in the clonal Trifolium repens (Fabaceae).
Bittebiere, Anne-Kristel; Renaud, Nolwenn; Clément, Bernard; Mony, Cendrine
2012-04-01
Plant communities in temperate zones are dominated by clonal plants that can plastically modify their growth characteristics in response to competition. Given that plants compete with one another, and the implications this has for species coexistence, we conducted a study to assess how clonal species morphologically respond to competition for light depending on its intensity and heterogeneity, which are determined by the competitor species. We assessed the morphological response to competition for light of the clonal species Trifolium repens L. by measuring its growth performance, and vertical and horizontal growth traits. We used five competitive environments, i.e., one without competitor and four differing by their competitor species creating different conditions of competition intensity and heterogeneity. The morphological response of Trifolium repens to competition for light depended on the competitor identity. Competition intensity and heterogeneity, determined by competitor identity, had an interactive effect on most traits. The increase in petiole elongation and specific leaf area due to increased competition intensity was observed only at low to intermediate competition heterogeneity. Competition heterogeneity promoted the elongation of clone connections allowing space exploration. Our results demonstrated that the intensity and heterogeneity of competition, which depended on competitor identity, are of primary importance in determining the plastic response of Trifolium repens. This emphasizes that it is important to consider the fine-scale spatial distribution of individuals when studying their interactions within plant communities.
-
Competition for pollinators and intra-communal spectral dissimilarity of flowers
van der Kooi, C. J.; Pen, I.; Staal, M.; Stavenga, D. G.; Elzenga, J. T. M.
Competition for pollinators occurs when, in a community of flowering plants, several simultaneously flowering plant species depend on the same pollinator. Competition for pollinators increases interspecific pollen transfer rates, thereby reducing the number of viable offspring. In order to decrease
-
International Nuclear Information System (INIS)
1992-06-01
This report presents an updated analysis of the projected cost of electricity from new baseload power plants beginning operation around the year 2000. Included in the study are: (1) advanced-design, standardized nuclear power plants; (2) low emissions coal-fired power plants; (3) gasified coal-fired power plants; and (4) natural gas-fired power plants. This analysis shows that electricity from advanced-design, standardized nuclear power plants will be economically competitive with all other baseload electric generating system alternatives. This does not mean that any one source of electric power is always preferable to another. Rather, what this analysis indicates is that, as utilities and others begin planning for future baseload power plants, advanced-design nuclear plants should be considered an economically viable option to be included in their detailed studies of alternatives. Even with aggressive and successful conservation, efficiency and demand-side management programs, some new baseload electric supply will be needed during the 1990s and into the future. The baseload generating plants required in the 1990s are currently being designed and constructed. For those required shortly after 2000, the planning and alternatives assessment process must start now. It takes up to ten years to plan, design, license and construct a new coal-fired or nuclear fueled baseload electric generating plant and about six years for a natural gas-fired plant. This study indicates that for 600-megawatt blocks of capacity, advanced-design nuclear plants could supply electricity at an average of 4.5 cents per kilowatt-hour versus 4.8 cents per kilowatt-hour for an advanced pulverized-coal plant, 5.0 cents per kilowatt-hour for a gasified-coal combined cycle plant, and 4.3 cents per kilowatt-hour for a gas-fired combined cycle combustion turbine plant
-
Varga, S.; Vega-Frutis, R.; Kytöviita, M.-M.; Franken, P.
2017-01-01
Plants usually interact with other plants, and the outcome of such interaction ranges from facilitation to competition depending on the identity of the plants, including their sexual expression. Arbuscular mycorrhizal (AM) fungi have been shown to modify competitive interactions in plants. However, few studies have evaluated how AM fungi influence plant intraspecific and interspecific interactions in dioecious species. The competitive abilities of female and male plants of Antennaria dioic...
-
Crosby, K.C.; Pietraszewska-Bogiel, A.; Gadella (jr.), T.W.J.; Winkel, B.S.J.
2011-01-01
We have used Förster resonance energy transfer detected by fluorescence lifetime imaging microscopy (FLIM-FRET) to provide the first evidence from living plants cells for the existence of a flavonoid metabolon. The distribution of flux within this system may be regulated by the direct competition of
-
Competitive intransitivity promotes species coexistence.
Laird, Robert A; Schamp, Brandon S
2006-08-01
Using a spatially explicit cellular automaton model with local competition, we investigate the potential for varied levels of competitive intransitivity (i.e., nonhierarchical competition) to promote species coexistence. As predicted, on average, increased levels of intransitivity result in more sustained coexistence within simulated communities, although the outcome of competition also becomes increasingly unpredictable. Interestingly, even a moderate degree of intransitivity within a community can promote coexistence, in terms of both the length of time until the first competitive exclusion and the number of species remaining in the community after 500 simulated generations. These results suggest that modest levels of intransitivity in nature, such as those that are thought to be characteristic of plant communities, can contribute to coexistence and, therefore, community-scale biodiversity. We explore a potential connection between competitive intransitivity and neutral theory, whereby competitive intransitivity may represent an important mechanism for "ecological equivalence."
-
Interspecific competition between alien and native congeneric species
Garcia-Serrano, H.; Sans, F. X.; Escarré, J.
2007-01-01
A good way to check hypotheses explaining the invasion of ecosystems by exotic plants is to compare alien and native congeneric species. To test the hypothesis that invasive alien plants are more competitive than natives, we designed a replacement series experiment to evaluate interspecific competition between three Senecio species representing the same bushy life form: two alien species ( S. inaequidens and S. pterophorus, both from South Africa) and a native species from the south-east of the Iberian Peninsula and Maghreb ( S. malacitanus). While S. inaequidens is widespread throughout western Europe and is expanding towards the south of Spanish-French border, the geographical distribution of the recently introduced S. pterophorus is still limited to north-eastern Spain. Plants from each species were grown in pure and in mixed cultures with one of their congeners, and water availability was manipulated to evaluate the effects of water stress on competitive abilities. Our results show that the alien S. inaequidens is the most competitive species for all water conditions. The native S. malacitanus is more competitive that the alien S. pterophorus in water stress conditions, but this situation is reversed when water availability is not limiting.
-
Economic requirements for competitive laser fusion power production
International Nuclear Information System (INIS)
Hogan, W.J.; Meier, W.R.
1986-01-01
An economic model of a laser fusion commercial power plant is used to identify the design and operating regimes of the driver, target and reaction chamber that will result in economic competitiveness with future fission and coal plants. The authors find that, for a plant with a net power of 1 GW/sub e/, the cost of the driver must be less than $0.4 to 0.6 B, and the recirculating power fraction must be less than 25%. Target gain improvements at low driver energy are the most beneficial but also the most difficult to achieve. The optimal driver energy decreases with increasing target technology. The sensitivity of the cost of electricity to variations in cost and performance parameters decreases with increasing target technology. If chamber pulse rates of a few Hz can be achieved, then gains of 80-100 are sufficient, and higher pulse rates do not help much. Economic competitiveness becomes more difficult with decreasing plant size. Finally, decreasing the cost of the balance of plant has the greatest beneficial effect on economic competitiveness
-
Interference competition between sunbirds and carpenter bees for ...
African Journals Online (AJOL)
Interference competition between sunbirds and carpenter bees for the nectar of ... the nectar plant Hypoestes aristata against carpenter bees (Xylocopa caffra and ... co-evolution, nectar, interspecific competition, pollination biology, pollinators, ...
-
Competition Between Different Sources of Electricity
International Nuclear Information System (INIS)
Cintra do Prado, L.
1966-01-01
To persons interested in nuclear energy questions, and especially administrators in the private or public sector, one of the most important questions is the competitive status of nuclear electricity in relation to electricity supplied from other sources. In this connection ''to compete'' means to produce at an equivalent or lower cost. Nuclear plants will be particularly attractive, and even preferable, when they can supply power at costs lower than conventional sources, e.g. water and fossil fuels. In many European countries and in the United States, the competitiveness of nuclear power is generally considered purely in comparison with thermal plants operating on coal or mineral oil, since such plants are predominant in those countries. This is not the case in Brazil and other countries where the bulk of the electricity produced comes from hydroelectric plants
-
Leicht-Young, Stacey A.; Pavlovic, Noel B.; Adams, Jean V.
2012-01-01
Competitive interactions between native plants and nonnative, invasive plant species have been extensively studied; however, within degraded landscapes, the effect of interspecific interactions among invasive plants is less explored. We investigated a competitive interaction between two sympatric, invasive mustard species that have similar life history strategies and growth forms: garlic mustard and damesrocket. Greenhouse experiments using a full range of reciprocal density ratios were conducted to investigate interspecific competition. Garlic mustard had a negative effect on the final biomass, number of leaves, and relative growth rate in height of damesrocket. Survival of damesrocket was not negatively affected by interspecific competition with garlic mustard; however, garlic mustard showed higher mortality because of intraspecific competition. These results indicated that although garlic mustard has been observed to be the dominant species in this landscape, it may not completely outcompete damesrocket in all situations. Studies of invasive species in competition are important in degraded landscapes because this is the common situation in many natural areas.
-
Competitive exclusion among fig wasps achieved via entrainment of host plant flowering phenology.
Directory of Open Access Journals (Sweden)
Min Liu
Full Text Available Molecular techniques are revealing increasing numbers of morphologically similar but co-existing cryptic species, challenging the niche theory. To understand the co-existence mechanism, we studied phenologies of morphologically similar species of fig wasps that pollinate the creeping fig (F. pumila in eastern China. We compared phenologies of fig wasp emergence and host flowering at sites where one or both pollinators were present. At the site where both pollinators were present, we used sticky traps to capture the emerged fig wasps and identified species identity using mitochondrial DNA COI gene. We also genotyped F. pumila individuals of the three sites using polymorphic microsatellites to detect whether the host populations were differentiated. Male F. pumila produced two major crops annually, with figs receptive in spring and summer. A small partial third crop of receptive figs occurred in the autumn, but few of the second crop figs matured at that time. Hence, few pollinators were available to enter third crop figs and they mostly aborted, resulting in two generations of pollinating wasps each year, plus a partial third generation. Receptive figs were produced on male plants in spring and summer, timed to coincide with the release of short-lived adult pollinators from the same individual plants. Most plants were pollinated by a single species. Plants pollinated by Wiebesia sp. 1 released wasps earlier than those pollinated by Wiebesia sp. 3, with little overlap. Plants occupied by different pollinators were not spatially separated, nor genetically distinct. Our findings show that these differences created mismatches with the flight periods of the other Wiebesia species, largely 'reserving' individual plants for the resident pollinator species. This pre-emptive competitive displacement may prevent long term co-existence of the two pollinators.
-
Interspecific competition influences the organization of a diverse sessile insect community
Cornelissen, Tatiana; de Carvalho Guimarães, Carla Daniele; Rodrigues Viana, João Paulo; Silva, Bárbara
2013-10-01
Interspecific competition has played a major role in determining the effects of species interactions in terrestrial communities and the perception of its role on shaping population dynamics and community structure has changed throughout the years. In this study, we evaluated the existence of interspecific competition in the herbivore community of the dioecious plant Baccharis pseudomyriocephala (Asteraceae), which holds a diverse community of gall-forming insects. Sixty plants were studied and gall richness and abundance among plants were evaluated. To address whether a plant already occupied by a gall species is preferred or avoided by another gall species, null models were used for all 60 plants combined and for male and female plants separately. Our results have shown that the 11 species of gall-formers found on B. pseudomyriocephala co-occur less than expected by chance alone, indicating that interspecific competition might be an important force structuring the insect community in this tropical host plant, regardless of plant gender.
-
Does competition influence safety?
International Nuclear Information System (INIS)
Pamme, H.
2000-01-01
Competition in the deregulated electricity market does not leave nuclear power plants unaffected. Operators seek to run their plants at maximum availability and with optimized cost structures so that specific generating costs are minimized. The 'costs of safety', with their fixed-cost character, are elements of this cost structure. Hence the question whether safety is going to suffer under the cost pressure on the market. The study shows that the process of economic optimization does not permit cost minimization for its own sake in the area of operating costs which can be influenced by management or are 'avoidable'. The basis of assessment rather must be potential risks which could entail losses of availability. Prophylactic investments made in order to avoid losses of availability to a large extent also imply unchanged or even higher levels of safety. Economic viability and safety thus are closely correlated. Competition in a deregulated marekt so far has not done any direct harm to plant safety. An even more efficient use of scarce funds and, hopefully, a tolerable political environment should allow the safety level of nuclear power plants to be upheld, and safety culture to be maintained, also in the future. (orig.) [de
-
Stable isotope signatures reflect competitiveness between trees under changed CO2/O3 regimes
International Nuclear Information System (INIS)
Grams, T.E.E.; Matyssek, R.
2010-01-01
Here we synthesize key findings from a series of experiments to gain new insight on inter-plant competition between juvenile beech (Fagus sylvatica) and spruce (Picea abies) under the influence of increased O 3 and CO 2 concentrations. Competitiveness of plants was quantified and mechanistically interpreted as space-related resource investments and gains. Stable isotopes were addressed as temporal integrators of plant performance, such as photosynthesis and its relation to water use and nitrogen uptake. In the weaker competitor, beech, efficiency in space-related aboveground resource investment was decreased in competition with spruce and positively related to Δ 13 C, as well as stomatal conductance, but negatively related to δ 18 O. Likewise, our synthesis revealed that strong belowground competition for water in spruce was paralleled in this species by high N assimilation capacity. We suggest combining the time-integrative potential of stable isotopes with space-related investigations of competitiveness to accomplish mechanistic understanding of plant competition for resources. - Combination of space-related concepts of competitiveness with stable isotopes has potential to clarify mechanisms of competition.
-
Root-shoot growth responses during interspecific competition quantified using allometric modelling.
Robinson, David; Davidson, Hazel; Trinder, Clare; Brooker, Rob
2010-12-01
Plant competition studies are restricted by the difficulty of quantifying root systems of competitors. Analyses are usually limited to above-ground traits. Here, a new approach to address this issue is reported. Root system weights of competing plants can be estimated from: shoot weights of competitors; combined root weights of competitors; and slopes (scaling exponents, α) and intercepts (allometric coefficients, β) of ln-regressions of root weight on shoot weight of isolated plants. If competition induces no change in root : shoot growth, α and β values of competing and isolated plants will be equal. Measured combined root weight of competitors will equal that estimated allometrically from measured shoot weights of each competing plant. Combined root weights can be partitioned directly among competitors. If, as will be more usual, competition changes relative root and shoot growth, the competitors' combined root weight will not equal that estimated allometrically and cannot be partitioned directly. However, if the isolated-plant α and β values are adjusted until the estimated combined root weight of competitors matches the measured combined root weight, the latter can be partitioned among competitors using their new α and β values. The approach is illustrated using two herbaceous species, Dactylis glomerata and Plantago lanceolata. Allometric modelling revealed a large and continuous increase in the root : shoot ratio by Dactylis, but not Plantago, during competition. This was associated with a superior whole-plant dry weight increase in Dactylis, which was ultimately 2·5-fold greater than that of Plantago. Whole-plant growth dominance of Dactylis over Plantago, as deduced from allometric modelling, occurred 14-24 d earlier than suggested by shoot data alone. Given reasonable assumptions, allometric modelling can analyse competitive interactions in any species mixture, and overcomes a long-standing problem in studies of competition.
-
Increased competition does not lead to increased phylogenetic overdispersion in a native grassland.
Bennett, Jonathan A; Lamb, Eric G; Hall, Jocelyn C; Cardinal-McTeague, Warren M; Cahill, James F
2013-09-01
That competition is stronger among closely related species and leads to phylogenetic overdispersion is a common assumption in community ecology. However, tests of this assumption are rare and field-based experiments lacking. We tested the relationship between competition, the degree of relatedness, and overdispersion among plants experimentally and using a field survey in a native grassland. Relatedness did not affect competition, nor was competition associated with phylogenetic overdispersion. Further, there was only weak evidence for increased overdispersion at spatial scales where plants are likely to compete. These results challenge traditional theory, but are consistent with recent theories regarding the mechanisms of plant competition and its potential effect on phylogenetic structure. We suggest that specific conditions related to the form of competition and trait conservatism must be met for competition to cause phylogenetic overdispersion. Consequently, overdispersion as a result of competition is likely to be rare in natural communities. © 2013 John Wiley & Sons Ltd/CNRS.
-
International Nuclear Information System (INIS)
Bianchi, M.A.; Fleck, N.G.; Dillenburg, L.R.
2006-01-01
Plants compete for environmental resources located below and over soil surface. Physical separation of competition allows understanding the relative importance of each fraction, as well as identifying possible differences among species. The aim of this research was to separate the individual effects resulting from competition for soil or solar radiation resources, between soybean and concurrent plants. Thus, experiments using pots were carried out at UFRGS, in Porto Alegre-RS, in 2001 and 2002. The treatments tested resulted from the combinations of two concurrent genotypes (crop and competitor) and four competition conditions (absence of competition, competition for soil and solar radiation, competition for soil resources, and competition for solar radiation). Soybean cultivars IAS 5 and FEPAGRO RS 10 represented the crop, whereas radish forage and the soybean cultivar FUNDACEP 33 were the competitors tested. Morpho-physiological variables were evaluated in the soybean plants and radish forage. Growth of the soybean plants was most affected by soil resources competition, with RS 10 cultivar being more competitive than IAS 5.Radish forage did not interfere in the growth of soybean cultivars but it benefited from soybean presence. (author) 6
-
Schimmel, Bernardus C J; Ataide, Livia M S; Chafi, Rachid; Villarroel, Carlos A; Alba, Juan M; Schuurink, Robert C; Kant, Merijn R
2017-06-01
Spider mites are destructive arthropod pests on many crops. The generalist herbivorous mite Tetranychus urticae induces defenses in tomato (Solanum lycopersicum) and this constrains its fitness. By contrast, the Solanaceae-specialist Tetranychus evansi maintains a high reproductive performance by suppressing tomato defenses. Tetranychus evansi outcompetes T. urticae when infesting the same plant, but it is unknown whether this is facilitated by the defenses of the plant. We assessed the extent to which a secondary infestation by a competitor affects local plant defense responses (phytohormones and defense genes), mite gene expression and mite performance. We observed that T. evansi switches to hyper-suppression of defenses after its tomato host is also invaded by its natural competitor T. urticae. Jasmonate (JA) and salicylate (SA) defenses were suppressed more strongly, albeit only locally at the feeding site of T. evansi, upon introduction of T. urticae to the infested leaflet. The hyper-suppression of defenses coincided with increased expression of T. evansi genes coding for salivary defense-suppressing effector proteins and was paralleled by an increased reproductive performance. Together, these observations suggest that T. evansi overcompensates its reproduction through hyper-suppression of plant defenses in response to nearby competitors. We hypothesize that the competitor-induced overcompensation promotes competitive population growth of T. evansi on tomato. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.
-
Competitive energy markets and nuclear power. Can we have both, do we want either?
International Nuclear Information System (INIS)
Thomas, Steve
2010-01-01
In 1987, the UK Conservative Party was re-elected promising to transform the electricity industry into a privatised competitive industry and to promote an expansion of nuclear power. Fulfilling both objectives was not possible. The nuclear plants were withdrawn from the sale and plans to build new plants were abandoned, but privatisation proceeded. In 2007, the Labour government began a new attempt to build nuclear plants to operate in the competitive electricity market, promising that no subsidies would be offered to them. By 2010, the utilities that were planning to build nuclear plants were beginning to suggest that 'support' in some form would be needed if they were to build new plants. More surprisingly, the energy regulator, Ofgem, cast doubt on whether a competitive wholesale electricity market would provide security of supply. In 1990, the UK government opted for a competitive electricity market over expanding nuclear power. Now, the option of opting for a competitive electricity market may not exist. However, this might not leave the way open for new nuclear plants. The expected cost of power from new nuclear plants is now so high that no more than one or two heavily subsidised plants will be built. (author)
-
Competitive impacts of an invasive nectar thief on plant-pollinator mutualisms
Hanna, Cause; Foote, David; Kremen, Claire
2014-01-01
Plant–pollinator mutualisms are disrupted by a variety of competitive interactions between introduced and native floral visitors. The invasive western yellowjacket wasp, Vespula pensylvanica, is an aggressive nectar thief of the dominant endemic Hawaiian tree species, Metrosideros polymorpha. We conducted a large-scale, multiyear manipulative experiment to investigate the impacts of V. pensylvanica on the structure and behavior of the M. polymorpha pollinator community, including competitive mechanisms related to resource availability. Our results demonstrate that V. pensylvanica, through both superior exploitative and interference competition, influences resource partitioning and displaces native and nonnative M. polymorpha pollinators. Furthermore, the restructuring of the pollinator community due to V. pensylvanica competition and predation results in a significant decrease in the overall pollinator effectiveness and fruit set of M. polymorpha. This research highlights both the competitive mechanisms and contrasting effects of social insect invaders on plant–pollinator mutualisms and the role of competition in pollinator community structure.
-
Biological conditions for oscillations and chaos generated by multispecies competition
Huisman, J; Weissing, FJ
2001-01-01
We investigate biological mechanisms that generate oscillations and chaos in multispecies competition models. For this purpose, we use a competition model concerned with competition for abiotic essential resources. Because phytoplankton and plants consume quite a number of abiotic essential
-
Economic competitiveness of nuclear power in China
International Nuclear Information System (INIS)
Hu Chuanwen
2005-01-01
Development of nuclear power in China has made a good progress. Currently, economic competitiveness of nuclear power compared to fossil-fuelled power plants is one of the major problems which hamper its development. This article presents the economic competitiveness of nuclear power in China with two-level analyses. First, levelized lifetime cost method is adopted for electricity generation cost comparisons. Important factors influencing economic competitiveness of nuclear power are described. Furthermore, a broad economic evaluation of the full fuel chain of nuclear power and fossil-fuelled plants is discussed concerning macro social-economic issues, environmental and health impacts. The comprehensive comparative assessment would be carried out for decision making to implement nuclear power programme. In consideration of external costs and carbon value, the economic competitiveness of nuclear power would be further improved. Facing swift economic growth, huge energy demand and heavy environmental burden, nuclear power could play a significant role in sustainable development in China. (authors)
-
Directory of Open Access Journals (Sweden)
A. Bahari
2016-05-01
Full Text Available In order to study the competition ability of amaranth and mungbean in fodder intercropping system under different crop residue management, a field experiment was conducted at two seasons (first planting of wheat and then intercropping management in Agricultural Faculty of Shahid Chamran University of Ahvaz during growing season of 2010-2011. The experimental design was split plot based on randomized complete block design with three replications. Three crop residue managements were in main plot and five planting ratios were in sub-plot. Eight indices of the competition abilities were measured. The results showed that the highest intercropping fodder yield (1347.6 g.m-2 and LER (1.27 were obtained in residue incorporated and 50% planting ratio of each crop. Residue burning increased variation of CR, reduced RLO and RCI and also, had the highest RYL. In higher planting ratio, the aggrissivity of amaranth was more than mung bean. In treatments with highest forage yield, amaranth and mungbean were dominant and non-dominant crops, respectively. In conclusion, amaranth was more influenced by residue management methods and planting ratios than mung bean and also, its competition ability had more variation in compared by mung bean.
-
Mycorrhizal association in soybean and weeds in competition
Directory of Open Access Journals (Sweden)
Cíntia Maria Teixeira Fialho
2016-04-01
Full Text Available The purpose of this study was to evaluate the effects of mycorrhizal association on the interference of Bidens pilosa, Urochloa decumbens and Eleusine indica on soybean culture in two conditions: a plants competing without contact with roots of another species; b with contact between roots. At 60 days after planting, growth, nutrient accumulation and mycorrhizal colonization of soybean and weeds were evaluated. The contact between roots of soybean plant and weed species increased the negative interference effects for both species, with less growth and nutrient accumulation. With the individualization of roots, higher competition occurred for soil resources up to 60 days of coexistence between species. In competition with soybean, Bidens pilosa and Urochloa decumbens stood out in accumulation of most nutrients without differing from when cultivated in monocultivation. The increase of the soybean mycorrhizal colonization was 53, 40 and 33% when in competition with Urochloa decumbens, Eleusine indica and Bidens pilosa species, respectively. A positive interaction occurred for soybean mycorrhizal colonization and competing plants irrespective of weed species or root contact.
-
Advancing the competitive future of nuclear power through partnerships
International Nuclear Information System (INIS)
Pryor, Charles W.
2002-01-01
Full text: The emergence of competitive markets, coupled with significant environmental benefits, will create a period of tremendous opportunity and enhanced value for commercial nuclear power plants, both existing plants and those on the immediate horizon. The challenge for nuclear plant owners and operators is to reduce costs and improve performance in order to improve the plants net earnings stream and remain competitive with other forms of generation. In his remarks, Dr. Pryor will examine the excellent performance of nuclear plants worldwide and look at the significant value yet to be captured from existing plants. Continued capacity factor improvement driven primarily by shorter outages will help, but new business practices will be needed in the future to achieve competitive production costs of around 1cent/kwh at the bus bar. Dr. Pryor will explore innovative approaches to resource sharing and integration that already are paying dividends worldwide. Beyond this immediate need for greater cooperative efforts is the necessity of longer-range strategies implementing advanced technologies in new plant designs. Although energy demand and environmental benefits are driving renewed interest in nuclear power, the cost challenge for new plants remains significant. Dr. Pryor will discuss the cost challenge, new designs that are available to meet market demand, and the role of utility/supplier partnerships in current and future new plant projects. (author)
-
Competição entre plantas com ênfase no recurso luz Competition among plants for the light recourse
Directory of Open Access Journals (Sweden)
Carlos Renato Tavares de Castro
1996-04-01
Full Text Available A competição entre plantas pelos diferentes fatores da produção vem recebendo, a bastante tempo, a atenção do homem. As diversas espécies vegetais reagem a cada tipo de competição de maneira diferente, mas apesar do seu importante papel na organização dos indivíduos num dado habitat, a competição inter e intra especifica é responsável pela redução da produtividade de muitas culturas, restringindo a diversificação dos consorciamentos e exigindo cuidados intensivos no controle da infestação por plantas daninhas. Nos consorciamentos, a modificação da qualidade e intensidade da radiação solar imposta pela cultura de porte mais elevado é um fator de seleção das espécies botânicas capazes de se desenvolverem sob esta condição; a melhor utilização e aproveitamento da energia solar e dos espaços vertical e horizontal aliada ao favorecimento da ciclagem de nutrientes e melhoria da estrutura do solo são vantagens explícitas do consorciamento. Muitos pesquisadores consideram a competição por luz, devido à interferência da parte aérea, mais importante e complexa do que a competição pelo substrato. Algumas espécies reagem à competição por luz ativando mecanismos complexos e se adaptando ao novo "status" de radiação, o que lhes confere uma grande capacidade adaptativa. Atualmente, um dos grandes desafios que se impõem aos pesquisadores é o desenvolvimento de técnicas de consorciamento em que se obtenha aumento da interação positiva entre as culturas, minimizando a competição. Para tal é primordial a compreensão dos processos competitivos envolvidos e este artigo apresenta uma breve revisão sobre eles.The intercropping for the various production factors by the plants has being receiving attention for a long time. The different plant species have a diverse way of reacting to each kind of competition. However, besides its important role on the individual organization in an habitat, the inter and intra
-
Kaplan, Ian; Denno, Robert F
2007-10-01
The importance of interspecific competition is a highly controversial and unresolved issue for community ecology in general, and for phytophagous insects in particular. Recent advancements, however, in our understanding of indirect (plant- and enemy-mediated) interactions challenge the historical paradigms of competition. Thus, in the context of this rapidly developing field, we re-evaluate the evidence for interspecific competition in phytophagous insects using a meta-analysis of published studies. Our analysis is specifically designed to test the assumptions underlying traditional competition theory, namely that competitive interactions are symmetrical, necessitate spatial and temporal co-occurrence, and increase in intensity as the density, phylogenetic similarity, and niche overlap of competing species increase. Despite finding frequent evidence for competition, we found very little evidence that plant-feeding insects conform to theoretical predictions for interspecific competition. Interactions were highly asymmetrical, similar in magnitude within vs. between feeding guilds (chewers vs. sap-feeders), and were unaffected by the quantity of resources removed (% defoliation). There was mixed support for the effects of phylogeny, spatial/temporal separation, and the relative strength of intra- vs. interspecific competition. Clearly, a new paradigm that accounts for indirect interactions and facilitation is required to describe how interspecific competition contributes to the organization of phytophagous insect communities, and perhaps to other plant and animal communities as well.
-
Herbivory and competition slow down invasion of a tall grass along a productivity gradient
Kuijper, DPJ; Nijhoff, DJ; Bakker, JP
2004-01-01
Competition models including competition for light predict that small plant species preferred by herbivores will be outshaded by taller unpreferred plant species with increasing productivity. When the tall plant species is little grazed by the herbivores, it can easily invade and dominate short
-
Competitive energy markets and nuclear power. Can we have both, do we want either?
Energy Technology Data Exchange (ETDEWEB)
Thomas, Steve [Public Services International Research Unit (PSIRU), Business School, University of Greenwich, 30 Park Row, London SE10 9LS (United Kingdom)
2010-09-15
In 1987, the UK Conservative Party was re-elected promising to transform the electricity industry into a privatised competitive industry and to promote an expansion of nuclear power. Fulfilling both objectives was not possible. The nuclear plants were withdrawn from the sale and plans to build new plants were abandoned, but privatisation proceeded. In 2007, the Labour government began a new attempt to build nuclear plants to operate in the competitive electricity market, promising that no subsidies would be offered to them. By 2010, the utilities that were planning to build nuclear plants were beginning to suggest that 'support' in some form would be needed if they were to build new plants. More surprisingly, the energy regulator, Ofgem, cast doubt on whether a competitive wholesale electricity market would provide security of supply. In 1990, the UK government opted for a competitive electricity market over expanding nuclear power. Now, the option of opting for a competitive electricity market may not exist. However, this might not leave the way open for new nuclear plants. The expected cost of power from new nuclear plants is now so high that no more than one or two heavily subsidised plants will be built. (author)
-
Competitive energy markets and nuclear power: Can we have both, do we want either?
Energy Technology Data Exchange (ETDEWEB)
Thomas, Steve, E-mail: Stephen.thomas@gre.ac.u [Public Services International Research Unit (PSIRU), Business School, University of Greenwich, 30 Park Row, London SE10 9LS (United Kingdom)
2010-09-15
In 1987, the UK Conservative Party was re-elected promising to transform the electricity industry into a privatised competitive industry and to promote an expansion of nuclear power. Fulfilling both objectives was not possible. The nuclear plants were withdrawn from the sale and plans to build new plants were abandoned, but privatisation proceeded. In 2007, the Labour government began a new attempt to build nuclear plants to operate in the competitive electricity market, promising that no subsidies would be offered to them. By 2010, the utilities that were planning to build nuclear plants were beginning to suggest that 'support' in some form would be needed if they were to build new plants. More surprisingly, the energy regulator, Ofgem, cast doubt on whether a competitive wholesale electricity market would provide security of supply. In 1990, the UK government opted for a competitive electricity market over expanding nuclear power. Now, the option of opting for a competitive electricity market may not exist. However, this might not leave the way open for new nuclear plants. The expected cost of power from new nuclear plants is now so high that no more than one or two heavily subsidised plants will be built.
-
Rhizosphere hydrophobicity: A positive trait in the competition for water.
Zeppenfeld, Thorsten; Balkenhol, Niko; Kóvacs, Kristóf; Carminati, Andrea
2017-01-01
The ability to acquire water from the soil is a major driver in interspecific plant competition and it depends on several root functional traits. One of these traits is the excretion of gel-like compounds (mucilage) that modify physical soil properties. Mucilage secreted by roots becomes hydrophobic upon drying, impedes the rewetting of the soil close to the root, the so called rhizosphere, and reduces water availability to plants. The function of rhizosphere hydrophobicity is not easily understandable when looking at a single plant, but it may constitute a competitive advantage at the ecosystem level. We hypothesize that by making the top soil hydrophobic, deep-rooted plants avoid competititon with shallow-rooted plants. To test this hypothesis we used an individual-based model to simulate water uptake and growth of two virtual plant species, one deep-rooted plant capable of making the soil hydrophobic and a shallow-rooted plant. We ran scenarios with different precipitation regimes ranging from dry to wet (350, 700, and 1400 mm total annual precipitation) and from high to low precipitation frequencies (1, 7, and 14 days). Plant species abundance and biomass were chosen as indicators for competitiveness of plant species. At constant precipitation frequency mucilage hydrophobicity lead to a benefit in biomass and abundance of the tap-rooted population. Under wet conditions this effect diminished and tap-rooted plants were less productive. Without this trait both species coexisted. The effect of root exudation trait remained constant under different precipitation frequencies. This study shows that mucilage secretion is a competitive trait for the acquisition of water. This advantage is achieved by the modification of the soil hydraulic properties and specifically by inducing water repellency in soil regions which are shared with other species.
-
Rhizosphere hydrophobicity: A positive trait in the competition for water.
Directory of Open Access Journals (Sweden)
Thorsten Zeppenfeld
Full Text Available The ability to acquire water from the soil is a major driver in interspecific plant competition and it depends on several root functional traits. One of these traits is the excretion of gel-like compounds (mucilage that modify physical soil properties. Mucilage secreted by roots becomes hydrophobic upon drying, impedes the rewetting of the soil close to the root, the so called rhizosphere, and reduces water availability to plants. The function of rhizosphere hydrophobicity is not easily understandable when looking at a single plant, but it may constitute a competitive advantage at the ecosystem level. We hypothesize that by making the top soil hydrophobic, deep-rooted plants avoid competititon with shallow-rooted plants. To test this hypothesis we used an individual-based model to simulate water uptake and growth of two virtual plant species, one deep-rooted plant capable of making the soil hydrophobic and a shallow-rooted plant. We ran scenarios with different precipitation regimes ranging from dry to wet (350, 700, and 1400 mm total annual precipitation and from high to low precipitation frequencies (1, 7, and 14 days. Plant species abundance and biomass were chosen as indicators for competitiveness of plant species. At constant precipitation frequency mucilage hydrophobicity lead to a benefit in biomass and abundance of the tap-rooted population. Under wet conditions this effect diminished and tap-rooted plants were less productive. Without this trait both species coexisted. The effect of root exudation trait remained constant under different precipitation frequencies. This study shows that mucilage secretion is a competitive trait for the acquisition of water. This advantage is achieved by the modification of the soil hydraulic properties and specifically by inducing water repellency in soil regions which are shared with other species.
-
Lin, Tiantian
2015-01-01
Although the introduction of invasive plant species in a given area causes economic and ecological problems, it still provides an ideal opportunity for ecologists to study evolutionary changes. According to the Evolution of Increased Competitive Ability hypothesis and Shifting Defense Hypothesis,
-
Competition for pollinators and intra-communal spectral dissimilarity of flowers.
van der Kooi, C J; Pen, I; Staal, M; Stavenga, D G; Elzenga, J T M
2016-01-01
Competition for pollinators occurs when, in a community of flowering plants, several simultaneously flowering plant species depend on the same pollinator. Competition for pollinators increases interspecific pollen transfer rates, thereby reducing the number of viable offspring. In order to decrease interspecific pollen transfer, plant species can distinguish themselves from competitors by having a divergent phenotype. Floral colour is an important signalling cue to attract potential pollinators and thus a major aspect of the flower phenotype. In this study, we analysed the amount of spectral dissimilarity of flowers among pollinator-competing plants in a Dutch nature reserve. We expected pollinator-competing plants to exhibit more spectral dissimilarity than non-competing plants. Using flower visitation data of 2 years, we determined the amount of competition for pollinators by different plant species. Plant species that were visited by the same pollinator were considered specialist and competing for that pollinator, whereas plant species visited by a broad array of pollinators were considered non-competing generalists. We used principal components analysis to quantify floral reflectance, and found evidence for enhanced spectral dissimilarity among plant species within specialist pollinator guilds (i.e. groups of plant species competing for the same pollinator). This is the first study that examined intra-communal dissimilarity in floral reflectance with a focus on the pollination system. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.
-
Mahdavi-Arab, Nafiseh; Meyer, Sebastian T; Mehrparvar, Mohsen; Weisser, Wolfgang W
2014-01-01
Plant-herbivore interactions are influenced by host plant quality which in turn is affected by plant growth conditions. Competition is the major biotic and nutrient availability a major abiotic component of a plant's growth environment. Yet, surprisingly few studies have investigated impacts of competition and nutrient availability on herbivore performance and reciprocal herbivore effects on plants. We studied growth of the specialist aphid, Macrosiphoniella tanacetaria, and its host plant tansy, Tanacetum vulgare, under experimental addition of inorganic and organic fertilizer crossed with competition by goldenrod, Solidago canadensis. Because of evidence that competition by goldenrod is mediated by allelopathic compounds, we also added a treatment with activated carbon. Results showed that fertilization increased, and competition with goldenrod decreased, plant biomass, but this was likely mediated by resource competition. There was no evidence from the activated carbon treatment that allelopathy played a role which instead had a fertilizing effect. Aphid performance increased with higher plant biomass and depended on plant growth conditions, with fertilization and AC increasing, and plant competition decreasing aphid numbers. Feedbacks of aphids on plant performance interacted with plant growth conditions in complex ways depending on the relative magnitude of the effects on plant biomass and aphid numbers. In the basic fertilization treatment, tansy plants profited from increased nutrient availability by accumulating more biomass than they lost due to an increased number of aphids under fertilization. When adding additional fertilizer, aphid numbers increased so high that tansy plants suffered and showed reduced biomass compared with controls without aphids. Thus, the ecological cost of an infestation with aphids depends on the balance of effects of growth conditions on plant and herbivore performance. These results emphasize the importance to investigate both
-
Directory of Open Access Journals (Sweden)
Nafiseh Mahdavi-Arab
Full Text Available Plant-herbivore interactions are influenced by host plant quality which in turn is affected by plant growth conditions. Competition is the major biotic and nutrient availability a major abiotic component of a plant's growth environment. Yet, surprisingly few studies have investigated impacts of competition and nutrient availability on herbivore performance and reciprocal herbivore effects on plants. We studied growth of the specialist aphid, Macrosiphoniella tanacetaria, and its host plant tansy, Tanacetum vulgare, under experimental addition of inorganic and organic fertilizer crossed with competition by goldenrod, Solidago canadensis. Because of evidence that competition by goldenrod is mediated by allelopathic compounds, we also added a treatment with activated carbon. Results showed that fertilization increased, and competition with goldenrod decreased, plant biomass, but this was likely mediated by resource competition. There was no evidence from the activated carbon treatment that allelopathy played a role which instead had a fertilizing effect. Aphid performance increased with higher plant biomass and depended on plant growth conditions, with fertilization and AC increasing, and plant competition decreasing aphid numbers. Feedbacks of aphids on plant performance interacted with plant growth conditions in complex ways depending on the relative magnitude of the effects on plant biomass and aphid numbers. In the basic fertilization treatment, tansy plants profited from increased nutrient availability by accumulating more biomass than they lost due to an increased number of aphids under fertilization. When adding additional fertilizer, aphid numbers increased so high that tansy plants suffered and showed reduced biomass compared with controls without aphids. Thus, the ecological cost of an infestation with aphids depends on the balance of effects of growth conditions on plant and herbivore performance. These results emphasize the importance
-
Intra- and interspecific competition between western flower thrips and sweetpotato whitefly.
Wu, Qing-Jun; Hou, Wen-Jie; Li, Fei; Xu, Bao-Yun; Xie, Wen; Wang, Shao-Li; Zhang, You-Jun
2014-01-01
The western flower thrips, Frankliniella occidentalis (Pergande), and the sweetpotato whitefly, Bemisia tabaci (Gennadius), are both invasive insect pests and are present in most of the same agricultural crops without a clear dominance of either species. Here, intra- and interspecific competition in B. tabaci and F. occidentalis was determined under controlled experiments. The results showed that intraspecific competition was distinct in F. occidentalis and that the co-occurrence of B. tabaci had a strong effect on F. occidentalis, resulting in a decrease in oviposition. Significant intraspecific competition was found in B. tabaci, and the coexistence of F. occidentalis had limited effect on the oviposition of B. tabaci. In a selective host plant preference experiment, both F. occidentalis and B. tabaci preferred eggplants most, followed by cucumbers and tomatoes. On cucumber plants, B. tabaci was predominant, whereas on eggplant and tomato plants, F. occidentalis and B. tabaci exhibited comparative competitive abilities during the initial stage. However, over time, higher numbers of B. tabaci than that of F. occidentalis were found on the two host plants. Our in vitro and potted plant experiments indicate that B. tabaci is competitively superior to F. occidentalis, which might help to explain their differential distribution patterns in China. © The Author 2014. Published by Oxford University Press on behalf of the Entomological Society of America.
-
Biomass of tree species as a response to planting density and interspecific competition
Directory of Open Access Journals (Sweden)
Paulo Sérgio Lima e Silva
2014-04-01
Full Text Available Planting trees is an important way to promote the recovery of degraded areas in the Caatinga region. Experiments (E1, E2, and E3 were conducted in a randomized blocks design, with three, three, and five replicates, respectively. The objectives were to evaluate biomass of the shoots of: a gliricidia (G and sabiá (S, as a response to planting density; b G, S, and neem (N in competition; c G, and S in agroforestry. E1 was conducted in split-plots, and planting densities (400, 600, 800, 1000, and 1200 plants ha-1 as subplots. E2 consisted of a factorial comprising the following plots: GGG, NGN, SGS, NNN, GNG, SNS, SSS, GSG, NSN (each letter represents a row of plants. E3 was conducted with G and S in agroforestry experiment. The trees were harvested after 54, 42, and 27 months old, in E1, E2 and E3, respectively. In E1, G presented higher green biomass of the stems and leaf at smaller densities than S, but lower green biomass of branches at most densities. The species did not differ for mean stem dry biomass and leaf dry biomass, but G showed higher branch dry biomass at most densities. Higher planting densities increased green and dry biomass of stems, branches, and leaves in S, but decreased those characteristics in G, with the exception of leaf dry mass, which was not influenced by density. In E2, the behavior of each species was identical in plots containing the same or different species. Griricidia showed the highest green biomass of stems and branches, and the highest values for geren biomass of the leaf were observed for gliricidia and neem. The highest stem, branch, and leaf dry biomass values were obtained for G, S, and N, respectively. In E3, G was superior for stem and leaf green biomass, and for stem and branch dry biomass. There were no differences between species for the other biomass values.
-
Competitivity of biofuels in heating
International Nuclear Information System (INIS)
Flyktman, M.
1996-01-01
The competitivity of indigenous fuels in heating of residential houses in comparison with imported fuels, and both electricity and district heating, has been studied in this research, ordered by the Finnish Ministry of Trade and Industry. Heating plants of residential house scale (20-1000 kW) have been investigated in the research. Only the new heating plants are included in the investigation. The heat generation calculations concerning the residential heating plants have been made for following indigenous fuels: sod peat, fuel-chips, peat and wood pellets, firewood and straw. In addition to these, the calculations have been made for light fuel-oil, electric heating, district heating and natural gas. The local energy tariffs have to be taken into account in electric heating, district heating and natural gas heating. A calculation model, based on flowsheet calculation, forms the main result of the project. By using the model it is possible to update the competitivity data rapidly. Of all the indigenous fuels, sod peat and fuel-chips appeared to be competitive with electric and district heating costs in nearly all scales investigated. The construction of the heat generation costs of solid indigenous fuels differs remarkably from those of electric and district heating. The main part of the heating costs of wood chips and sod peat is formed of fixed costs; i.e. of investment costs and of the costs of heating and control work. The energy costs are the highest costs items in electric an district heating, as well as in the oil heating. It is possible to improve the competitivity of biofuels by developing cheaper boilers and fuel processing and storage devices
-
Evolutionary responses of native plant species to invasive plants: a review.
Oduor, Ayub M O
2013-12-01
Strong competition from invasive plant species often leads to declines in abundances and may, in certain cases, cause localized extinctions of native plant species. Nevertheless, studies have shown that certain populations of native plant species can co-exist with invasive plant species,suggesting the possibility of adaptive evolutionary responses of those populations to the invasive plants. Empirical inference of evolutionary responses of the native plant species to invasive plants has involved experiments comparing two conspecific groups of native plants for differences in expression of growth/reproductive traits: populations that have experienced competition from the invasive plant species (i.e. experienced natives) versus populations with no known history of interactions with the invasive plant species (i.e. naıve natives). Here, I employ a meta-analysis to obtain a general pattern of inferred evolutionary responses of native plant species from 53 such studies. In general, the experienced natives had significantly higher growth/reproductive performances than naıve natives, when grown with or without competition from invasive plants.While the current results indicate that certain populations of native plant species could potentially adapt evolutionarily to invasive plant species, the ecological and evolutionary mechanisms that probably underlie such evolutionary responses remain unexplored and should be the focus of future studies.
-
Directory of Open Access Journals (Sweden)
S. F. Kotov
2005-09-01
Full Text Available Dynamics of competitive interactions in populations of annual euhalophyte S. europaea was investigated. For S. europaea the hypothesis of Newman and Tilman is confirmed, concerning presence of intensive competition between plants on unproductive habitats for soil resources. Vital state of plants in populations of S. europaea is determined by intensity of competitive interactions, level of humidity and degree of salinity of ecotype. On an example of S. europaea, productive activity of plants on salted habitats was analyzed and the role of interspecific competition in this process was determined.
-
The effect of counter-trading on competition in electricity markets
Dijk, J.J.; Willems, B.
2011-01-01
In a competitive electricity market, nodal pricing is the most efficient way to manage congestion. Counter-trading is inefficient as it gives the wrong long term signals for entry and exit of power plants. However, in a non-competitive market, additional entry will improve the competitiveness of the
-
The reciprocal relationship between competition and intraspecific trait variation
DEFF Research Database (Denmark)
A Bennett, Jonathan; Riibak, Kersti; Tamme, Riin
2016-01-01
competitive dynamics from trait patterns within communities. However, plant traits are frequently plastic in response to competition. This variation is poorly accounted for in trait based studies of competition and community assembly. 2.To explore the relationship between trait responses and competitive...... with larger leaves and lower specific leaf area than their neighbours. Switching to more stress tolerant strategies by increasing root diameter and leaf tissue density also reduced competition. However, dissimilarity in root tissue density also minimized competition, consistent with limiting similarity...... suggest that considering the effect of competition on trait expression is critical to understanding the relationship between traits and community assembly....
-
International Nuclear Information System (INIS)
Brandfon, W.W.
1984-01-01
In view of the current high cost of coal and nuclear plants and the unfavorable regulatory and financial conditions under which they've been built in the last decade, the Atomic Industrial Forum assembled a Study Group, with extensive experience in economic analysis to examine future cost possibilities. This paper summarizes the first phase of a two-phase study to address the competitiveness of electricity from new coal and nuclear plants with oil and natural gas in common markets
-
COMPETITIVE ABILITY OF BEAN CULTIVARS WITH HAIRY BEGGARTICKS
Directory of Open Access Journals (Sweden)
LEANDRO GALON
2017-01-01
Full Text Available Weed interference is a factor that limits the productivity of beans and, among these, hairy beggarticks is one of the main species competing with the crop for environmental resources. Thus, the aim of this study is to evaluate the competitive ability of black bean cultivars (BRS Campeiro, IPR Uirapuru, SCS204 Predileto and BRS Supremo in the presence of a biotype of hairy beggarticks. The experimental design is a completely randomized block with four replications. Treatments were arranged in a replacement series, consisting of a proportion of the crop and the hairy beggarticks: 100:0; 75:25; 50:50: 24:75, and 0:100, which corresponds to 40:0, 30:10, 20:20, 10:30, and 0:40 plant pots1. We accomplished competitive analysis through diagrams applied to the replacement series, as well as using relative competitive indices. The leaf area and shoot dry mass were evaluated at 40 days after emergence of the species. There was competition between bean cultivars and hairy beggarticks for the same environmental resources, causing negative interference in the growth of the species, independent of the proportion of plants. Bean cultivars had a lower relative loss by reducing the morphological variables of the hairy beggarticks, thereby demonstrating superiority in its competitive ability in relation to the weed. Interspecific competition is less damaging than intraspecific competition for both species.
-
Comparative study of economic competitive for nuclear seawater desalination
International Nuclear Information System (INIS)
Tian Li; Wang Yongqing
2001-01-01
The method of levelized discounted production water cost and the new desalination economic evaluation program (DEEP1.1) are used. Many cases of seawater desalination by nuclear energy or fossil energy combined with reverse osmosis (RO), Multi-effect distillation (MED) or multi-stage flash (MSF) technology in south-east Asia is performed and their economic competitive is analyzed. Their results indicate, the nuclear desalination plants have stronger economic competitive comparing to the fossil in the RO, MED and MSF technology. The desalination water cost is very changeable depending on the difference of desalination technology and water plant size. Its range is 0.56 dollar · m -3 - 1.89 dollar · m -3 , the lowest desalination water cost is product by RO and the highest is by MSF. The sensitive factors of the economic competitive are orderly the discounted rate, desalination plant size, seawater temperature and total dissolved solids (TDS), fossil fuel price and specific power plant investment. The highest rate of water cost is about 19.3% comparing to base case
-
A canopy architectural model to study the competitive ability of chickpea with sowthistle.
Cici, S-Zahra-Hosseini; Adkins, Steve; Hanan, Jim
2008-06-01
Improving the competitive ability of crops is a sustainable method of weed management. This paper shows how a virtual plant model of competition between chickpea (Cicer arietinum) and sowthistle (Sonchus oleraceus) can be used as a framework for discovering and/or developing more competitive chickpea cultivars. The virtual plant models were developed using the L-systems formalism, parameterized according to measurements taken on plants at intervals during their development. A quasi-Monte Carlo light-environment model was used to model the effect of chickpea canopy on the development of sowthistle. The chickpea-light environment-sowthistle model (CLES model) captured the hypothesis that the architecture of chickpea plants modifies the light environment inside the canopy and determines sowthistle growth and development pattern. The resulting CLES model was parameterized for different chickpea cultivars (viz. 'Macarena', 'Bumper', 'Jimbour' and '99071-1001') to compare their competitive ability with sowthistle. To validate the CLES model, an experiment was conducted using the same four chickpea cultivars as different treatments with a sowthistle growing under their canopy. The growth of sowthistle, both in silico and in glasshouse experiments, was reduced most by '99071-1001', a cultivar with a short phyllochron. The second rank of competitive ability belonged to 'Macarena' and 'Bumper', while 'Jimbour' was the least competitive cultivar. The architecture of virtual chickpea plants modified the light inside the canopy, which influenced the growth and development of the sowthistle plants in response to different cultivars. This is the first time that a virtual plant model of a crop-weed interaction has been developed. This virtual plant model can serve as a platform for a broad range of applications in the study of chickpea-weed interactions and their environment.
-
Native fruit traits may mediate dispersal competition between native and non-native plants
Directory of Open Access Journals (Sweden)
Clare Aslan
2012-02-01
Full Text Available Seed disperser preferences may mediate the impact of invasive, non-native plant species on their new ecological communities. Significant seed disperser preference for invasives over native species could facilitate the spread of the invasives while impeding native plant dispersal. Such competition for dispersers could negatively impact the fitness of some native plants. Here, we review published literature to identify circumstances under which preference for non-native fruits occurs. The importance of fruit attraction is underscored by several studies demonstrating that invasive, fleshy-fruited plant species are particularly attractive to regional frugivores. A small set of studies directly compare frugivore preference for native vs. invasive species, and we find that different designs and goals within such studies frequently yield contrasting results. When similar native and non-native plant species have been compared, frugivores have tended to show preference for the non-natives. This preference appears to stem from enhanced feeding efficiency or accessibility associated with the non-native fruits. On the other hand, studies examining preference within existing suites of co-occurring species, with no attempt to maximize fruit similarity, show mixed results, with frugivores in most cases acting opportunistically or preferring native species. A simple, exploratory meta-analysis finds significant preference for native species when these studies are examined as a group. We illustrate the contrasting findings typical of these two approaches with results from two small-scale aviary experiments we conducted to determine preference by frugivorous bird species in northern California. In these case studies, native birds preferred the native fruit species as long as it was dissimilar from non-native fruits, while non-native European starlings preferred non-native fruit. However, native birds showed slight, non-significant preference for non-native fruit
-
Pollinator Competition as a Driver of Floral Divergence: An Experimental Test.
Directory of Open Access Journals (Sweden)
Ethan J Temeles
Full Text Available Optimal foraging models of floral divergence predict that competition between two different types of pollinators will result in partitioning, increased assortative mating, and divergence of two floral phenotypes. We tested these predictions in a tropical plant-pollinator system using sexes of purple-throated carib hummingbirds (Anthracothorax jugularis as the pollinators, red and yellow inflorescence morphs of Heliconia caribaea as the plants, and fluorescent dyes as pollen analogs in an enclosed outdoor garden. When foraging alone, males exhibited a significant preference for the yellow morph of H. caribaea, whereas females exhibited no preference. In competition, males maintained their preference for the yellow morph and through aggression caused females to over-visit the red morph, resulting in resource partitioning. Competition significantly increased within-morph dye transfer (assortative mating relative to non-competitive environments. Competition and partitioning of color morphs by sexes of purple-throated caribs also resulted in selection for floral divergence as measured by dye deposition on stigmas. Red and yellow morphs did not differ significantly in dye deposition in the competition trials, but differences in dye deposition and preferences for morphs when sexes of purple-throated caribs foraged alone implied fixation of one or the other color morph in the absence of competition. Competition also resulted in selection for divergence in corolla length, with the red morph experiencing directional selection for longer corollas and the yellow morph experiencing stabilizing selection on corolla length. Our results thus support predictions of foraging models of floral divergence and indicate that pollinator competition is a viable mechanism for divergence in floral traits of plants.
-
International Nuclear Information System (INIS)
Brandfon, W.W.
1984-01-01
The first phase of a two-phase study of the competitiveness of electricity from new coal and nuclear plants with oil and natural gas in common markets concludes that, with few exceptions throughout the country, overall levelized nuclear generating cost could be lower than coal generating costs by more than 40%. The study shows a wider margin of economic superiority for nuclear than has been seen in other recent studies. Capital and fuel costs are the major determinants of relative nuclear and coal economics. The only substantial difference in the input assumptions has related to a shorter lead time for both coal and nuclear units, which reduces capital costs. The study gives substance to the charge that delaying tactics by intervenors and an unstable licensing environment drove up lifetime costs of both coal and nuclear plants. This caused an increase in electric rates and affected the entire economy. The study shows that nuclear power is competitive when large baseload capacity is required. 14 figures
-
Linking root traits and competitive success in grassland species
Ravenek, Janneke M.; Mommer, Liesje; Visser, Eric J.W.; Ruijven, van Jasper; Paauw, van der Jan Willem; Smit-Tiekstra, Annemiek; Caluwe, de Hannie; Kroon, de Hans
2016-01-01
Background and aims: Competition is an important force shaping plant communities. Here we test the hypothesis that high overall root length density and selective root placement in nutrient patches, as two alternative strategies, confer competitive advantage in species mixtures. Methods: We
-
Effects of plant density and proportion on the interaction between wheat with alexandergrass plants
Directory of Open Access Journals (Sweden)
Leonardo Bianco de Carvalho
2011-01-01
Full Text Available Determination of competitive relationships among plant species requires appropriate experimental designs and method of analysis. The hypothesis of this research was that two species growing in coexistence show different growth and development due to their relative competitiveness. This research aims to measure the relative competitiveness of wheat crop compared to Alexandergrass by the interpretation of plant density and proportional effects using replacement series experiments. Monocultures were cultivated in densities of 1, 3, 5, 10 and 15 plants per pot and analyzed by regression of dry mass data. Mixture experiment was cultivated in wheat:Alexandergrass proportions of 0:6, 1:5, 2:4, 3:3, 4:2, 5:1 and 6:0 plants per pot and analyzed by graphical interpretation of growth and production characteristics. Both experiments were carried out in randomized complete block design with four replicates. Alexandergrass was more sensitive to intraspecific competition than wheat. Alexandergrass was lightly more competitive than wheat. Number and weight of spikes and number of tillers were the wheat characteristics more affected by Alexandergrass interference.
-
Coevolution between invasive and native plants driven by chemical competition and soil biota.
Lankau, Richard A
2012-07-10
Although reciprocal evolutionary responses between interacting species are a driving force behind the diversity of life, pairwise coevolution between plant competitors has received less attention than other species interactions and has been considered relatively less important in explaining ecological patterns. However, the success of species transported across biogeographic boundaries suggests a stronger role for evolutionary relationships in shaping plant interactions. Alliaria petiolata is a Eurasian species that has invaded North American forest understories, where it competes with native understory species in part by producing compounds that directly and indirectly slow the growth of competing species. Here I show that populations of A. petiolata from areas with a greater density of interspecific competitors invest more in a toxic allelochemical under common conditions. Furthermore, populations of a native competitor from areas with highly toxic invaders are more tolerant to competition from the invader, suggesting coevolutionary dynamics between the species. Field reciprocal transplants confirmed that native populations more tolerant to the invader had higher fitness when the invader was common, but these traits came at a cost when the invader was rare. Exotic species are often detrimentally dominant in their new range due to their evolutionary novelty; however, the development of new coevolutionary relationships may act to integrate exotic species into native communities.
-
Will nuclear power be a competitive energy source in the future?
International Nuclear Information System (INIS)
Peter, U.; Staender, K.
1995-01-01
In order to safeguard the competitiveness of European manufacturers in the world market, a Franco-German project for the development of a PWR, the European Pressurized Water Reactor (EPR), has been established in 1992, including activities for harmonization of reactor safety strategies and criteria on a European level, and standardization of existing nuclear engineering guides and codes. The project task to be achieved in the two years ahead is to prove that the new reactor design will meet the licensing requirements of both countries, and will be a successful, competitive system. The two project partners agreed to define the economic efficiency of the new reactor design to be proven as soon as evidence is given that operation of the EPR plant in the medium load range is competitive with the operation of a new, imported coal-fired conventional power plant. A basic, design-based economic efficiency analysis is given showing that the required competitiveness is achieved beyond 5.500 operating hours at full load. Sensitivity analyses of the power generation costs reveal that the system's competitiveness may be jeopardized by conceivably least favourable, specific costs of plant operation, fuel, or maintenance in particular. (orig./HP) [de
-
Competition for tracer 15N in tussock tundra ecosystems
International Nuclear Information System (INIS)
Marion, G.M.; Miller, P.C.; Black, C.H.
1987-01-01
The objectives of this study were to assess the roles of plant species, time, and site on competition for tracer 15 N (without carrier) in tussock tundra ecosystems. Six experimental sites were located in northern Alaska. After one year across the experimental sites, the recovery of 15 N by litter (11.3-16.3%) and mosses (5.4-16.4%) was significantly greater than for aboveground vascular plants (2.6-5.0%). 15 N recoveries by tundra vascular plants (2.6-5.0%) were low when compared to forest trees (9-25%) which suggst that competition for nitrogen is particularly severe in these colddominated tundra ecosystems. There were no significant differences among sites in 15 N recoveries by vascular plants, by mosses, or by litter. There was a statistically significant decline in 15 N recovery with time for Vaccinium vitis-idaea and Eriophoum vaginatum between the second and third year. The shallow rooted Vaccinium vitis-ideae was more highly labeled than the deep rooted Eriophorum vaginatum. Nearness to the source of the applied 15 N played a critical role in competition for surface applied nitrogen. (author)
-
Directory of Open Access Journals (Sweden)
Wei-Ming He
Full Text Available Climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. However, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. We conducted a common garden experiment with an invasive plant Centaurea maculosa and a native plant Poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competitive effects, and competitive responses of C. maculosa populations from Europe (home range and North America (introduced range under two different temperatures. The warming-induced inhibitory effects on the growth of C. maculosa alone were stronger in Europe than in North America. The competitive ability of C. maculosa plants from North America was greater than that of plants from Europe under the ambient condition whereas this competitive ability followed the opposite direction under the warming condition, suggesting that warming may enable European C. maculosa to be more invasive. Across two continents, warming treatment increased the competitive advantage instead of the growth advantage of C. maculosa, suggesting that climate warming may facilitate C. maculosa invasions through altering competitive outcomes between C. maculosa and its neighbors. Additionally, the growth response of C. maculosa to warming could predict its ability to avoid being suppressed by its neighbors.
-
He, Wei-Ming; Li, Jing-Ji; Peng, Pei-Hao
2012-01-01
Climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. However, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. We conducted a common garden experiment with an invasive plant Centaurea maculosa and a native plant Poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competitive effects, and competitive responses of C. maculosa populations from Europe (home range) and North America (introduced range) under two different temperatures. The warming-induced inhibitory effects on the growth of C. maculosa alone were stronger in Europe than in North America. The competitive ability of C. maculosa plants from North America was greater than that of plants from Europe under the ambient condition whereas this competitive ability followed the opposite direction under the warming condition, suggesting that warming may enable European C. maculosa to be more invasive. Across two continents, warming treatment increased the competitive advantage instead of the growth advantage of C. maculosa, suggesting that climate warming may facilitate C. maculosa invasions through altering competitive outcomes between C. maculosa and its neighbors. Additionally, the growth response of C. maculosa to warming could predict its ability to avoid being suppressed by its neighbors.
-
Bacterial endophytes enhance competition by invasive plants.
Rout, Marnie E; Chrzanowski, Thomas H; Westlie, Tara K; DeLuca, Thomas H; Callaway, Ragan M; Holben, William E
2013-09-01
Invasive plants can alter soil microbial communities and profoundly alter ecosystem processes. In the invasive grass Sorghum halepense, these disruptions are consequences of rhizome-associated bacterial endophytes. We describe the effects of N2-fixing bacterial strains from S. halepense (Rout and Chrzanowski, 2009) on plant growth and show that bacteria interact with the plant to alter soil nutrient cycles, enabling persistence of the invasive. • We assessed fluxes in soil nutrients for ∼4 yr across a site invaded by S. halepense. We assayed the N2-fixing bacteria in vitro for phosphate solubilization, iron chelation, and production of the plant-growth hormone indole-3-acetic acid (IAA). We assessed the plant's ability to recruit bacterial partners from substrates and vertically transmit endophytes to seeds and used an antibiotic approach to inhibit bacterial activity in planta and assess microbial contributions to plant growth. • We found persistent alterations to eight biogeochemical cycles (including nitrogen, phosphorus, and iron) in soils invaded by S. halepense. In this context, three bacterial isolates solubilized phosphate, and all produced iron siderophores and IAA in vitro. In growth chamber experiments, bacteria were transmitted vertically, and molecular analysis of bacterial community fingerprints from rhizomes indicated that endophytes are also horizontally recruited. Inhibiting bacterial activity with antibiotics resulted in significant declines in plant growth rate and biomass, with pronounced rhizome reductions. • This work suggests a major role of endophytes on growth and resource allocation of an invasive plant. Indeed, bacterial isolate physiology is correlated with invader effects on biogeochemical cycles of nitrogen, phosphate, and iron.
-
Predators induce interspecific herbivore competition for food in refuge space
Pallini, A.; Janssen, A.; Sabelis, M.W.
1998-01-01
Resource competition among herbivorous arthropods has long been viewed as unimportant because herbivore populations are controlled by predators. Although recently resurrected as an organizing force in arthropod communities on plants, there is still general agreement that resource competition among
-
Competitive economics of nuclear power
International Nuclear Information System (INIS)
Hellman, R.
1981-01-01
Some 12 components of a valid study of the competitive economics of a newly ordered nuclear power plant are identified and explicated. These are then used to adjust the original cost projections of four authoritative studies of nuclear and coal power economics
-
Photomorphogenic effects of UV-B radiation on plants: consequences for light competition
International Nuclear Information System (INIS)
Barnes, P.W.; Ballaré, C.L.; Caldwell, M.M.
1996-01-01
A combination of field and labotatory studies were conducted to explore the nature of photomorphogenic effects of ultraviolet-B radiation (UV-B; 280–320 nm) on plant morphology and to evaluate the ecological consequences of these alterations in morphology for interspecific competition. Under laboratory conditions, seedlings of cucumber (Cucumis sativus L.) and tomato (Lycopersicon esculentum Mill.) exhibited appreciable (ca. 50%) and rapid (< 3h) inhibition in hypocotyl elongation in response to UV-B exposure. In cucumber, this inhibition was reversible, occurred without any associated changes in dry matter production and was caused by UV-B incident on the cotyledons and not the stem or growing tip. Inhibition of stem elongation in etiolated tomato seedlings occurred at least 3 h prior to the onset of accumulation of UV-absorbing pigments and monochromatic UV supplied against a background of visible radiation revealed maximum effectiveness in inhibition around 300 nm. Collectively, these findings suggest that a specific, but yet unidentified, UV-B photoreceptor is involved in mediating certain morphological responses to UV-B. For mixtures of wheat (Triticum aestivum L.) and wild oat (Avena fatua L.), a common weedy competitor, supplemental UV-B irradiation in the field differentially altered shoot morphology which resulted in changes in canopy structure, light interception and calculated stand photosynthesis. It is argued that, because of its asymmetrical nature, competition for light can potentially amplify the effects of UV-B on shoot morphology and may, therefore, be an important mechanism by which changes in the solar UV-B spectrum associated with stratospheric ozone reduction could alter the composition and character of terrestrial vegetation
-
[Nodulation competitiveness of nodule bacteria: Genetic control and adaptive significance].
Onishchuk, O P; Vorobyov, N I; Provorov, N A
2017-01-01
The most recent data on the system of cmp (competitiveness) genes that determine the nodulation competitiveness of rhizobial strains, i.e., the ability to compete for nodule formation in leguminous plants, is analyzed. Three genetic approaches for the construction of economically valuable strains of rhizobia are proposed: the amplification of positive regulators of competitiveness, the inactivation of the negative regulators of this trait, and the introduction of efficient competitiveness factors into strains capable of active nitrogen fixation.
-
Oram, N.J.; Van de Voorde, T.F.J.; Ouwehand, G.J.; Bezemer, T.M.; Mommer, Liesje; Jeffery, S.; van Groeningen, J.W.
2014-01-01
Soil amendment with biochar is currently proposed as a management strategy to improve soil quality and enhance plant productivity. Relatively little is known about how biochar affects plant competition, although it has been suggested that it can increase the competitive ability of legumes. This
-
Inter-species competition-facilitation in stochastic riparian vegetation dynamics.
Tealdi, Stefano; Camporeale, Carlo; Ridolfi, Luca
2013-02-07
Riparian vegetation is a highly dynamic community that lives on river banks and which depends to a great extent on the fluvial hydrology. The stochasticity of the discharge and erosion/deposition processes in fact play a key role in determining the distribution of vegetation along a riparian transect. These abiotic processes interact with biotic competition/facilitation mechanisms, such as plant competition for light, water, and nutrients. In this work, we focus on the dynamics of plants characterized by three components: (1) stochastic forcing due to river discharges, (2) competition for resources, and (3) inter-species facilitation due to the interplay between vegetation and fluid dynamics processes. A minimalist stochastic bio-hydrological model is proposed for the dynamics of the biomass of two vegetation species: one species is assumed dominant and slow-growing, the other is subdominant, but fast-growing. The stochastic model is solved analytically and the probability density function of the plant biomasses is obtained as a function of both the hydrologic and biologic parameters. The impact of the competition/facilitation processes on the distribution of vegetation species along the riparian transect is investigated and remarkable effects are observed. Finally, a good qualitative agreement is found between the model results and field data. Copyright © 2012 Elsevier Ltd. All rights reserved.
-
Nuclear regulatory challenges arising from competition in electricity markets
International Nuclear Information System (INIS)
2001-01-01
In recent years a world-wide trend has been developing to introduce competition in electricity markets. As market competition unfolds, it produces a wide range of safety challenges for nuclear power plant operators and regulators. Nuclear regulators must be aware of the potential safety challenges produced and consider whether new regulatory response strategies are warranted. This report describes many of these challenges, their implications and possible regulatory response strategies. The intended audience is primarily nuclear safety regulators, although government authorities, nuclear power plant operators and the general public may also be interested. (author)
-
Competition along productivity gradients: news from heathlands.
Delerue, Florian; Gonzalez, Maya; Achat, David L; Puzos, Luc; Augusto, Laurent
2018-05-01
The importance of competition in low productive habitats is still debated. Studies which simultaneously evaluate preemption of resources and consequences for population dynamics are needed for a comprehensive view of competitive outcomes. We cultivated two emblematic species of European heathlands (Calluna vulgaris and Molinia caerulea) in a nursery for 2 years at two fertility levels, reproducing the productivity gradient found in phosphorus (P)-depleted heathlands in southwest France. The second year, we planted Ulex europaeus seedlings, a ubiquitous heathland species, under the cover of the two species to evaluate its ability to regenerate. Half of the seedlings were placed in tubes for exclusion of competitor roots. We measured the development of the competitors aboveground and belowground and their interception of resources (light, water, inorganic P). Ulex seedlings' growth and survival were also measured. Our results on resources interception were consistent with species distribution in heathlands. Molinia, which dominates rich heathlands, was the strongest competitor for light and water in the rich soil. Calluna, which dominates poor heathlands, increased its root allocation in the poor soil, decreasing water and inorganic P availability. However, the impact of total competition and root competition on Ulex seedlings decreased in the poor soil. Other mechanisms, especially decrease of water stress under neighbouring plant cover, appeared to have more influence on the seedlings' response. We found no formal contradiction between Tilman and Grime's theories. Root competition has a primary role in acquisition of soil resources in poor habitats. However, the importance of competition decreases with decreasing fertility.
-
Directory of Open Access Journals (Sweden)
Susanne Schwinning
Full Text Available Invasive plant species often dominate native species in competition, augmenting other potential advantages such as release from natural enemies. Resource pre-emption may be a particularly important mechanism for establishing dominance over competitors of the same functional type. We hypothesized that competitive success of an exotic grass against native grasses is mediated by establishing an early size advantage. We tested this prediction among four perennial C4 warm-season grasses: the exotic weed Johnsongrass (Sorghum halepense, big bluestem (Andropogon gerardii, little bluestem (Schizachyrium scoparius and switchgrass (Panicum virgatum. We predicted that a the competitive effect of Johnsongrass on target species would be proportional to their initial biomass difference, b competitive effect and response would be negatively correlated and c soil fertility would have little effect on competitive relationships. In a greenhouse, plants of the four species were grown from seed either alone or with one Johnsongrass neighbor at two fertilizer levels and periodically harvested. The first two hypotheses were supported: The seedling biomass of single plants at first harvest (50 days after seeding ranked the same way as the competitive effect of Johnsongrass on target species: Johnsongrass < big bluestem < little bluestem/switchgrass, while Johnsongrass responded more strongly to competition from Johnsongrass than from native species. At final harvest, native plants growing with Johnsongrass attained between 2-5% of their single-plant non-root biomass, while Johnsongrass growing with native species attained 89% of single-plant non-root biomass. Fertilization enhanced Johnsongrass' competitive effects on native species, but added little to the already severe competitive suppression. Accelerated early growth of Johnsongrass seedlings relative to native seedlings appeared to enable subsequent resource pre-emption. Size-asymmetric competition and resource
-
Lv, Qiming; Schneider, Manuel K; Pitchford, Jonathan W
2008-08-01
We study individual plant growth and size hierarchy formation in an experimental population of Arabidopsis thaliana, within an integrated analysis that explicitly accounts for size-dependent growth, size- and space-dependent competition, and environmental stochasticity. It is shown that a Gompertz-type stochastic differential equation (SDE) model, involving asymmetric competition kernels and a stochastic term which decreases with the logarithm of plant weight, efficiently describes individual plant growth, competition, and variability in the studied population. The model is evaluated within a Bayesian framework and compared to its deterministic counterpart, and to several simplified stochastic models, using distributional validation. We show that stochasticity is an important determinant of size hierarchy and that SDE models outperform the deterministic model if and only if structural components of competition (asymmetry; size- and space-dependence) are accounted for. Implications of these results are discussed in the context of plant ecology and in more general modelling situations.
-
International Nuclear Information System (INIS)
Fuqua, G.L.; Pratt, J.H.; Elliot, J.
1995-01-01
The change-over from regulated monopolies to a non-regulated competitive market in the electric utility industry was discussed in terms of marketing and survival strategies for utilities it the newly competitive marketplace. The impact of low natural gas prices was prominently discussed as a danger to hydroelectricity generators because high efficiency turbine generators that are now available. Surplus power capacity in both the Canadian and US markets were discussed. The effects of independent power producers selling electricity wholesale to private utilities was also debated on account of its potential to change the role of the electric utility. The situation of the Bonneville Power Association (BPA), a self-financed government agency, as owner of 15 000 miles of transmission grid that is not allowed to own generation plants, was described. Strategies developed by BPA in an effort to adapt to the competitive market were described and were successful
-
Burson, A.; Stomp, M.; Greenwell, E.; Grosse, J.; Huisman, J.
2018-01-01
A key challenge in ecology is to understand how nutrients and light affect the biodiversity and community structure of phytoplankton and plant communities. According to resource competition models, ratios of limiting nutrients are major determinants of species composition. At high nutrient levels,
-
Disturbance-mediated competition between perennial plants along a resource supply gradient
J. Stephen. Brewer
2011-01-01
Traditional views of ecological disturbance emphasize the role that physical disturbances play in reducing competition between populations and maintaining species coexistence. I present an alternative view that employs a simple LotkaâVolterra model to demonstrate how disturbance resistance, disturbance resilience and resource storage can increase competition between...
-
Predators induce interspecific herbivore competition for food in refuge space
Pallini, A.; Janssen, A.; Sabelis, M.W.
1998-01-01
Resource competition among herbivorous arthropods has long been viewed as unimportant because herbivore populations are controlled by predators. Although recently resurrected as an organizing force in arthropod communities on plants, there is still general agreement that resource competition among herbivores is reduced by predators. Here we show the reverse: predators induce interspecific resource competi-tion among herbivores. We found that thrips larvae (Frankliniella occidentalis) use the ...
-
The prospects for cost competitive solar PV power
International Nuclear Information System (INIS)
Reichelstein, Stefan; Yorston, Michael
2013-01-01
New solar Photovoltaic (PV) installations have grown globally at a rapid pace in recent years. We provide a comprehensive assessment of the cost competitiveness of this electric power source. Based on data available for the second half of 2011, we conclude that utility-scale PV installations are not yet cost competitive with fossil fuel power plants. In contrast, commercial-scale installations have already attained cost parity in the sense that the generating cost of power from solar PV is comparable to the retail electricity prices that commercial users pay, at least in certain parts of the U.S. This conclusion is shown to depend crucially on both the current federal tax subsidies for solar power and an ideal geographic location for the solar installation. Projecting recent industry trends into the future, we estimate that utility-scale solar PV facilities are on track to become cost competitive by the end of this decade. Furthermore, commercial-scale installations could reach “grid parity” in about ten years, if the current federal tax incentives for solar power were to expire at that point. - Highlights: ► Assessment of the cost competitiveness of new solar Photovoltaic (PV) installations. ► Utility-scale PV installations are not yet cost competitive with fossil fuel power plants. ► Commercial-scale installations have already attained cost parity in certain parts of the U.S. ► Utility-scale solar PV facilities are on track to become cost competitive by the end of this decade
-
Gehring, Catherine A; Mueller, Rebecca C; Haskins, Kristin E; Rubow, Tine K; Whitham, Thomas G
2014-01-01
Plants and mycorrhizal fungi influence each other's abundance, diversity, and distribution. How other biotic interactions affect the mycorrhizal symbiosis is less well understood. Likewise, we know little about the effects of climate change on the fungal component of the symbiosis or its function. We synthesized our long-term studies on the influence of plant parasites, insect herbivores, competing trees, and drought on the ectomycorrhizal fungal communities associated with a foundation tree species of the southwestern United States, pinyon pine (Pinus edulis), and described how these changes feed back to affect host plant performance. We found that drought and all three of the biotic interactions studied resulted in similar shifts in ectomycorrhizal fungal community composition, demonstrating a convergence of the community towards dominance by a few closely related fungal taxa. Ectomycorrhizal fungi responded similarly to each of these stressors resulting in a predictable trajectory of community disassembly, consistent with ecological theory. Although we predicted that the fungal communities associated with trees stressed by drought, herbivory, competition, and parasitism would be poor mutualists, we found the opposite pattern in field studies. Our results suggest that climate change and the increased importance of herbivores, competitors, and parasites that can be associated with it, may ultimately lead to reductions in ectomycorrhizal fungal diversity, but that the remaining fungal community may be beneficial to host trees under the current climate and the warmer, drier climate predicted for the future.
-
Modern plant management in the competitive market
Energy Technology Data Exchange (ETDEWEB)
Fischer, B.; Franke, U.; Freitag, J.U. [E.ON Kraftwerke GmbH, Hannover (Germany)
2002-07-01
Forced by the deregulation of the energy market and the big drop of electricity prices E.ON Kraftwerke was completely reorganised. Small, flexible units that are focussed on their key tasks were formed. Costs for electricity generation in our plants were reduced. Power plants that are currently not economically efficient are temporarily shut down. Power plants that are permanently not economically efficient are totally shut down. We have now reached a point at which energy prices slowly start to rise again. With our new plant management organization we have a lasting effect on further successfully operating power plants and a positive development of our company. Looking into the future does not create fear about what to do but positive believe that we will soon start new projects. This is the fundament for a stable, successful power plant company. (orig.) [German] Unter dem erheblichen Kostendruck, dem alle Energieversorger derzeit ausgesetzt sind, wurde die Aufbauorganisation von E.ON Energie grundlegend veraendert. Bei E.ON Kraftwerke wurden durch die Schaffung kleiner, flexibler Einheiten und eine klare Konzentration auf das Kerngeschaeft die Kosten fuer die Stromerzeugung in den eigenen Anlagen deutlich gesenkt. Die Auslastung vorhandener wirtschaftlicher Bloecke ist durch die Konservierung von derzeit nicht wirtschaftlichen bzw. durch die Stillegung langfristig nicht wirtschaftlicher Anlagen erheblich verbessert worden. Nachhaltig wurde damit eine Betriebsfuehrungsstrategie entwickelt, die den Bestand und eine positive Entwicklung der Kraftwerksgesellschaft sichert. (orig.)
-
Lang, Julien; Vigouroux, Armelle; Planamente, Sara; El Sahili, Abbas; Blin, Pauline; Aumont-Nicaise, Magali; Dessaux, Yves; Moréra, Solange; Faure, Denis
2014-10-01
By modifying the nuclear genome of its host, the plant pathogen Agrobacterium tumefaciens induces the development of plant tumours in which it proliferates. The transformed plant tissues accumulate uncommon low molecular weight compounds called opines that are growth substrates for A. tumefaciens. In the pathogen-induced niche (the plant tumour), a selective advantage conferred by opine assimilation has been hypothesized, but not experimentally demonstrated. Here, using genetics and structural biology, we deciphered how the pathogen is able to bind opines and use them to efficiently compete in the plant tumour. We report high resolution X-ray structures of the periplasmic binding protein (PBP) NocT unliganded and liganded with the opine nopaline (a condensation product of arginine and α-ketoglurate) and its lactam derivative pyronopaline. NocT exhibited an affinity for pyronopaline (K(D) of 0.6 µM) greater than that for nopaline (KD of 3.7 µM). Although the binding-mode of the arginine part of nopaline/pyronopaline in NocT resembled that of arginine in other PBPs, affinity measurement by two different techniques showed that NocT did not bind arginine. In contrast, NocT presented specific residues such as M117 to stabilize the bound opines. NocT relatives that exhibit the nopaline/pyronopaline-binding mode were only found in genomes of the genus Agrobacterium. Transcriptomics and reverse genetics revealed that A. tumefaciens uses the same pathway for assimilating nopaline and pyronopaline. Fitness measurements showed that NocT is required for a competitive colonization of the plant tumour by A. tumefaciens. Moreover, even though the Ti-plasmid conjugal transfer was not regulated by nopaline, the competitive advantage gained by the nopaline-assimilating Ti-plasmid donors led to a preferential horizontal propagation of this Ti-plasmid amongst the agrobacteria colonizing the plant-tumour niche. This work provided structural and genetic evidences to support the niche
-
Directory of Open Access Journals (Sweden)
Julien Lang
2014-10-01
Full Text Available By modifying the nuclear genome of its host, the plant pathogen Agrobacterium tumefaciens induces the development of plant tumours in which it proliferates. The transformed plant tissues accumulate uncommon low molecular weight compounds called opines that are growth substrates for A. tumefaciens. In the pathogen-induced niche (the plant tumour, a selective advantage conferred by opine assimilation has been hypothesized, but not experimentally demonstrated. Here, using genetics and structural biology, we deciphered how the pathogen is able to bind opines and use them to efficiently compete in the plant tumour. We report high resolution X-ray structures of the periplasmic binding protein (PBP NocT unliganded and liganded with the opine nopaline (a condensation product of arginine and α-ketoglurate and its lactam derivative pyronopaline. NocT exhibited an affinity for pyronopaline (K(D of 0.6 µM greater than that for nopaline (KD of 3.7 µM. Although the binding-mode of the arginine part of nopaline/pyronopaline in NocT resembled that of arginine in other PBPs, affinity measurement by two different techniques showed that NocT did not bind arginine. In contrast, NocT presented specific residues such as M117 to stabilize the bound opines. NocT relatives that exhibit the nopaline/pyronopaline-binding mode were only found in genomes of the genus Agrobacterium. Transcriptomics and reverse genetics revealed that A. tumefaciens uses the same pathway for assimilating nopaline and pyronopaline. Fitness measurements showed that NocT is required for a competitive colonization of the plant tumour by A. tumefaciens. Moreover, even though the Ti-plasmid conjugal transfer was not regulated by nopaline, the competitive advantage gained by the nopaline-assimilating Ti-plasmid donors led to a preferential horizontal propagation of this Ti-plasmid amongst the agrobacteria colonizing the plant-tumour niche. This work provided structural and genetic evidences to
-
Crowley, Philip H; Hopper, Kevin R; Krupa, James J
2013-12-01
Carnivorous plants and spiders, along with their prey, are main players in an insect-feeding guild found on acidic, poorly drained soils in disturbed habitat. Darwin's notion that these plants must actively attract the insects they capture raises the possibility that spiders could benefit from proximity to prey hotspots created by the plants. Alternatively, carnivorous plants and spiders may deplete prey locally or (through insect redistribution) more widely, reducing each other's gain rates from predation. Here, we formulate and analyze a model of this guild, parameterized for carnivorous sundews and lycosid spiders, under assumptions of random movement by insects and optimal foraging by predators. Optimal foraging here involves gain maximization via trap investment (optimal web sizes and sundew trichome densities) and an ideal free distribution of spiders between areas with and without sundews. We find no facilitation: spiders and sundews engage in intense exploitation competition. Insect attraction by plants modestly increases sundew gain rates but slightly decreases spider gain rates. In the absence of population size structure, optimal spider redistribution between areas with and without sundews yields web sizes that are identical for all spiders, regardless of proximity to sundews. Web-building spiders have higher gain rates than wandering spiders in this system at high insect densities, but wandering spiders have the advantage at low insect densities. Results are complex, indicating that predictions to be tested empirically must be based on careful quantitative assessment.
-
The competition of Linum with Camelina for minerals. 3
International Nuclear Information System (INIS)
Kranz, E.; Jacob, F.
1978-01-01
The competitive condition in the sulphate uptake of flax (Linum usitatissimum L.) and Camelina sativa (L.) Crantz was influenced by the herbicides MCPA, fenuron, alachlor and chloropham. Those herbicides (10 -4 M in each case) inhibited the uptake of sulphate of the plants. 12 h after exposing the plants in a solution deficient in sulphate flax plants in mixed culture took up less sulphate under the influence of MCPA, fenuron and chlorpropham. Camelina plants, however, also in mixed culture, with the exception of the MCPA variant, took up more of those ions than in monoculture. Under these conditions no essential change of the competitive conditions was found. In mixed culture, however, the sulphate uptake of Camelina plants - in percent of the untreated variant - was lower than in monoculture. In contrast to the untreated variants the sulphate uptake of Camelina plants decreased under the influence of alachlor in mixture, whereas there was no decrease found with Linum plants, both compared with the monoculture controls. Under influence of chlorpropham (10 -4 M) with an increased level of sulphate no essential decrease of sulphate uptake of Linum plants in mixture was found. With Camelina plants, however, a decrease of uptake in mixed culture was examined, both compared again with uptake in monoculture. (author)
-
Tonneijck, A.E.G.; Franzaring, J.; Brouwer, G.; Metselaar, K.; Dueck, T.A.
2004-01-01
Chronic effects of ozone on wet grassland species early in the growing season might be altered by interspecific competition. Individual plants of Holcus lanatus, Lychnis flos-cuculi, Molinia caerulea and Plantago lanceolata were grown in monocultures and in mixed cultures with Agrostis capillaris.
-
The objective is to achieve safe and competitive nuclear power
International Nuclear Information System (INIS)
Mattila, L.
1996-01-01
The 440 nuclear power plants in operation in the world today produce nearly one fifth of the world's electricity. Few new nuclear power plants are currently under construction in the West. Among the major factors slowing down the increase of nuclear power are the negative public opinion and the poor competitiveness of large plant units. In contrast, some of the countries in the Far East are busy building new nuclear power plant units. New advanced nuclear power plant types have been under development; the objective is to continue to improve safety and to raise the competitiveness. Increasing attention is also paid to measures extending the service life of the present power plants. Gas-cooled high-temperature reactors and liquid-metal-cooled breeder reactors appear to be promising alternatives. Practical experience of both plant types is available on the prototype level. Considerable sums of public research funds are spent towards the development of fusion technology. It is, however, unrealistic to expect fusion to become an important commercial source of energy before the middle of next century. (orig.) (4 figs.)
-
CONCEPTUAL APPROACH OF COMPETITIVENESS AND INTERDEPENDENCE BETWEEN COMPETITION AND COMPETITIVENESS
Directory of Open Access Journals (Sweden)
Tatiana GUTIUM
2017-11-01
Full Text Available This article is devoted to analysis of interdependence and correlation between competition and competitiveness, and competition’s consequences. The author analysed some authors’ visions on competitiveness, and common features between theories of competition and competitiveness. Using the synthetic indicator elaborated by author has been evaluated the competitiveness of domestic goods on the internal and external market. At the end of this article, the author has developed proposals to increase competitiveness.
-
Economic competitiveness requirements for evolutionary water cooled reactors
International Nuclear Information System (INIS)
Hudson, C.R.; Bertel, E.; Paik, K.H.; Roh, J.H.; Tort, V.
1999-01-01
This paper analyses the necessary economic conditions for evolutionary water cooled reactors to be competitive. Utilising recent national cost data for fossil-fired base load plants expected to be commissioned by 2005 -2010, target costs for nuclear power plants are discussed. Factors that could contribute to the achievement of those targets by evolutionary water cooled reactors are addressed. The feed-back from experience acquired in implementing nuclear programmes is illustrated by some examples from France and the Republic of Korea. The paper discusses the impacts on nuclear power competitiveness of globalisation and deregulation of the electricity market and privatisation of the electricity sector. In addition, issues related to external cost internalisation are considered. (author)
-
Directory of Open Access Journals (Sweden)
A.J Yanegh
2013-08-01
Full Text Available This study carried out in a factorial layout on completely randomaized block design with three replications, to evaluate the above- and below- ground competition between sesame (Sesamum indicum and pigweed (Amaranthus retroflexus, and their impacts on sesame yield and yield component. The experimental treatments were all combination of crop-weed competition (shoot competition, root competition and root-shoot competition and sesame plant densitys (1, 2 and 4 plant per pot. Plants were sown in plastic pots (24 cm diameter and 28 cm height in year 2010, at feild of Ferdowsi University of Mashhad. For study the shoot competition of sesame-pigweed, the roots were separated by plastic when the pots were filled with soil before sowing the seeds. Three weeks after emerging, shoots of plants were separated vertical barrier (30 x 70 cm for studing root competition. Results showed that competition treatments had a significant effect on seed weight per plant and yield components except 1000 seed weight. Among competition produced higher yield and yield components compared to othere treatments. However, sesame and pigweed biological weight in root-shoot competition was 2.6 and 13.7 respectively, that was higher than other competition treatments and was significant. Capsule number in main and sub branches, capsule number in plant, seed number in capsule and seed number in plant in complete competition treatment was 15, 2.58, 17.5, 43.7 and 693.89 respectively, that was higher than other treatments and differences among them was significant. Sesame density also had a significant effect on seed weight per plant and yield components. When low density were used (one plant, yield and yield components was more, therefore in one plant per pot density biological weight of sesame was 3.82 gr, and in higher densities the mentioned traits decreased significantly.
-
Directory of Open Access Journals (Sweden)
A. Koocheki
2014-12-01
Full Text Available Response surface models predict crop yield based on crop density and this is an important tool for evaluation competition at different density and hence selection of optimum density based on yield. In order to study intra and inter specific competition in intercropping bean (Phaseolus vulgaris and sesame (Sesamum indicum, an experiment was conducted at the Agricultural Research Station, Ferdowsi University of Mashhad during the growing season of 2010. For this purpose a complete randomized block design with 3 replications and 16 treatments based on different densities of sesame and bean intercropping was used. The model predicted the maximum yield of an isolated plant of bean and sesame approximately 33 and 17g per plant respectively. The area associated with the maximum yield per plant in bean and sesame were 0.6 and 0.1 m2, respectively. Bean was the dominant competitor with respect to both grain and biomass, and competition coefficient was 0.35 and 0.3 for bean grain yield and bean biomass respectively. Intra-specific competition was more important than inter-specific competition for bean. Competition coefficient was 2.6 and 2.9 for sesame grain yield and biomass respectively. Intra-specific competition was much less important than Interspecific competition in sesame. The highest grain yield in bean (300 g m-2 was obtained of sole crop with density of 20 plants, and the highest sesame grain yield (195 g m-2 was obtained of sole crop with density of 40 plants, the highest land equivalent ratio (1.14 was obtained in intercropping of 20 plants of bean and 10 plants of sesame.
-
Duan, Jian J; Larson, Kristi; Watt, Tim; Gould, Juli; Lelito, Jonathan P
2013-12-01
Competition for food, mates, and space among different individuals of the same insect species can affect density-dependent regulation of insect abundance or population dynamics. The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a serious invasive pest of North American ash (Fraxinus spp.) trees, with its larvae feeding in serpentine galleries between the interface of sapwood and phloem tissues of ash trees. Using artificial infestation of freshly cut logs of green ash (Fraxinus pennsylvanica Marshall) and tropical ash (Fraxinus uhdei [Wenzig] Lingelsh) with a series of egg densities, we evaluated the mechanism and outcome of intraspecific competition in larvae of A. planipennis in relation to larval density and host plant species. Results from our study showed that as the egg densities on each log (1.5-6.5 cm in diameter and 22-25 cm in length) increased from 200 to 1,600 eggs per square meter of surface area, larval survivorship declined from ≍68 to 10% for the green ash logs, and 86 to 55% for tropical ash logs. Accordingly, larval mortality resulting from cannibalism, starvation, or both, significantly increased as egg density increased, and the biomass of surviving larvae significantly decreased on both ash species. When larval density was adjusted to the same level, however, larval mortality from intraspecific competition was significantly higher and mean biomasses of surviving larvae was significantly lower in green ash than in tropical ash. The role of intraspecific competition of A. planipennis larvae in density-dependent regulation of its natural population dynamics is discussed.
-
Directory of Open Access Journals (Sweden)
Jeremiah R. Pinto
2018-04-01
Full Text Available Douglas fir (Pseudotsuga menziesii var. glauca (Mayr Franco, and western larch (Larix occidentalis Nutt. are species of ecological and commercial importance that occur throughout the Western United States. Effective reforestation of these species relies on successful seedling establishment, which is affected by planting stock quality, stocktype size, and site preparation techniques. This study examined the effects of container volume (80, 130, 200, and 250 cm3 and vegetative competition on seedling survival and physiological and morphological responses for two years, post-outplanting. Glyphosate application (GS and grass planting (HC were used to achieve low and high levels of competition. For all measured attributes, the container volume × vegetative competition was not significant. Mortality was strongly influenced by competition, with higher mortality observed for Douglas fir and western larch planted in HC plots one (28% and 98% and two (61% and 99% years following outplanting. When competition was controlled, seedlings of both species exhibited greater net photosynthesis (>9 μmol m−2 s−1, greater predawn water potential (>−0.35 MPa, and lower mortality (2–3% following one year in the field, indicating establishment success. The 80 cm3 stocktype remained significantly smaller and exhibited lower growth rates for the duration of the study, while all other stocktypes were statistically similar. Our results demonstrate the importance of controlling vegetative competition regardless of stocktype, especially for western larch, and suggest that benefits to post-planting seedling physiology and growth in relation to container size plateau beyond 130 cm3 among the investigated stocktypes.
-
Unique competitive effects of lianas and trees in a tropical forest understory.
Wright, Alexandra; Tobin, Mike; Mangan, Scott; Schnitzer, Stefan A
2015-02-01
Lianas are an important component of tropical forests, contributing up to 25% of the woody stems and 35% of woody species diversity. Lianas invest less in structural support but more in leaves compared to trees of similar biomass. These physiological and morphological differences suggest that lianas may interact with neighboring plants in ways that are different from similarly sized trees. However, the vast majority of past liana competition studies have failed to identify the unique competitive effects of lianas by controlling for the amount of biomass removed. We assessed liana competition in the forest understory over the course of 3 years by removing liana biomass and an equal amount of tree biomass in 40 plots at 10 sites in a secondary tropical moist forest in central Panama. We found that growth of understory trees and lianas, as well as planted seedlings, was limited due to competitive effects from both lianas and trees, though the competitive impacts varied by species, season, and size of neighbors. The removal of trees resulted in greater survival of planted seedlings compared to the removal of lianas, apparently related to a greater release from competition for light. In contrast, lianas had a species-specific negative effect on drought-tolerant Dipteryx oleifera seedlings during the dry season, potentially due to competition for water. We conclude that, at local scales, lianas and trees have unique and differential effects on understory dynamics, with lianas potentially competing more strongly during the dry season, and trees competing more strongly for light.
-
Puertollano IGCC plant. Present position and future competitiveness
Energy Technology Data Exchange (ETDEWEB)
Pedro Casero; Francisco Garcia-Pena
2006-07-01
This paper discusses the current status of the Puertollano 350 MW IGCC demonstration power plant in Spain. The experience provided by the operation of this plant during the last years is described, focussing on the core systems of the plant (gasifier, gas cleaning and gas turbines). Bottlenecks and weak points related to these systems are identified, along with the improvements. The production of hydrogen from coal at an IGCC plant is also discussed. 9 figs., 2 tabs.
-
Birhane, E.; Sterck, F.J.; Bongers, F.; Kuyper, T.W.
2014-01-01
Aims Arbuscular mycorrhizal fungi can have a substantial effect on the water and nutrient uptake by plants and the competition between plants in harsh environments where resource availability comes in pulses. In this study we focus on interspecific competition between Acaia etbaica and Boswellia
-
Nitrogen acquisition by plants and microorganisms in a temperate grassland.
Liu, Qianyuan; Qiao, Na; Xu, Xingliang; Xin, Xiaoping; Han, Jessie Yc; Tian, Yuqiang; Ouyang, Hua; Kuzyakov, Yakov
2016-03-10
Nitrogen (N) limitation is common in most terrestrial ecosystems, often leading to strong competition between microorganisms and plants. The mechanisms of niche differentiation to reduce this competition remain unclear. Short-term (15)N experiments with NH4(+), NO3(-), and glycine were conducted in July, August and September in a temperate grassland to evaluate the chemical, spatial and temporal niche differentiation by competition between plants and microorganisms for N. Microorganisms preferred NH4(+) and NO3(-), while plants preferred NO3(-). Both plants and microorganisms acquired more N in August and September than in July. The soil depth had no significant effects on microbial uptake, but significantly affected plant N uptake. Plants acquired 67% of their N from the 0-5 cm soil layer and 33% from the 5-15 cm layer. The amount of N taken up by microorganisms was at least seven times than plants. Although microorganisms efficiently compete for N with plants, the competition is alleviated through chemical partitioning mainly in deeper soil layer. In the upper soil layer, neither chemical nor temporal niche separation is realized leading to strong competition between plants and microorganisms that modifies N dynamics in grasslands.
-
Effects of competition on induction of crassulacean acid metabolism in a facultative CAM plant.
Yu, Kailiang; D'Odorico, Paolo; Li, Wei; He, Yongli
2017-06-01
Abiotic drivers of environmental stress have been found to induce CAM expression (nocturnal carboxylation) in facultative CAM species such as Mesembryanthemum crystallinum. The role played by biotic factors such as competition with non-CAM species in affecting CAM expression, however, remains largely understudied. This research investigated the effects of salt and water conditions on the competition between M. crystallinum and the C 3 grass Bromus mollis with which it is found to coexist in California's coastal grasslands. We also investigated the extent to which CAM expression in M. crystallinum was affected by the intensity of the competition with B. mollis. We found that M. crystallinum had a competitive advantage over B. mollis in drought and saline conditions, while B. mollis exerted strong competitive effects on M. crystallinum in access to light and soil nutrients in high water conditions. This strong competitive effect even outweighed the favorable effects of salt or water additions in increasing the biomass and productivity of M. crystallinum in mixture. Regardless of salt conditions, M. crystallinum did not switch to CAM photosynthesis in response to this strong competitive effect from B. mollis. Disturbance (i.e., grass cutting) reduced the competitive pressure by B. mollis and allowed for CAM expression in M. crystallinum when it was grown mixed with B. mollis. We suggest that moderate competition with other functional groups can enhance CAM expression in M. crystallinum, thereby affecting its plasticity and ability to cope with biological stress.
-
Competitive analysis of small hydroelectric power plants
International Nuclear Information System (INIS)
Assad, L.S.; Placido, R.
1990-01-01
The agreement between CPFL/UNICAMP/EFEI for developing energetic planning of Small Hydroelectric Power Plants construction is described. Some notions for showing the more economic alternative between decide by Small Hydroelectric Power Plants construction and continue supply the market by inter ligated system generation are shown in this stage of the agreement. (author)
-
International Nuclear Information System (INIS)
Tchapga, F.
2003-01-01
Nuclear power plant decommissioning is a mandatory operation for which financial arrangements have been defined. Current European decommissioning reserve find management models were designed in a context of operator monopolies and public property regime. Because of electricity sector restructuring; businesses are no longer protected from market sanctions and stock market volatility (affecting firm's financial viability). These potential sanctions create uncertainty on the decommission in financing mechanism. Thus, the form of decommissioning funds management (internal or external) appears as the main compatibility determinant with the electricity competition regimes. In a market risks environment, external management solutions improve credibility of operator's decommissioning commitment. (authors)
-
Rise and fall of competitiveness in individualistic and collectivistic societies.
Leibbrandt, Andreas; Gneezy, Uri; List, John A
2013-06-04
Competitiveness pervades life: plants compete for sunlight and water, animals for territory and food, and humans for mates and income. Herein we investigate human competitiveness with a natural experiment and a set of behavioral experiments. We compare competitiveness in traditional fishing societies where local natural forces determine whether fishermen work in isolation or in collectives. We find sharp evidence that fishermen from individualistic societies are far more competitive than fishermen from collectivistic societies, and that this difference emerges with work experience. These findings suggest that humans can evolve traits to specific needs, support the idea that socio-ecological factors play a decisive role for individual competitiveness, and provide evidence how individualistic and collectivistic societies shape economic behavior.
-
Host plant quality mediates competition between arbuscular mycorrhizal fungi
Czech Academy of Sciences Publication Activity Database
Knegt, B.; Jansa, Jan; Franken, O.; Engelmoer, D.J.P.; Werner, G.D.A.; Bucking, H.; Kiers, E. T.
2016-01-01
Roč. 20, April (2016), s. 233-240 ISSN 1754-5048 R&D Projects: GA MŠk(CZ) LK11224 Institutional support: RVO:61388971 Keywords : Biological market * Competitive exclusion * Cooperation Mutualism Subject RIV: EE - Microbiology, Virology Impact factor: 3.219, year: 2016
-
Competition between roots and microorganisms for nitrogen: mechanisms and ecological relevance
Kuzyakov, Yakov; Xu, Xingliang
2014-05-01
Demand of all living organisms on the same nutrients forms the basis for interspecific competition between plants and microorganisms in soils. This competition is especially strong in the rhizosphere. To evaluate competitive and mutualistic interactions between plants and microorganisms and to analyse ecological consequences of these interactions, we analysed 424 data pairs from 41 15N-labelling studies that investigated 15N redistribution between roots and microorganisms. Calculated Michaelis-Menten kinetics based on Km (Michaelis constant) and Vmax (maximum uptake capacity) values from 77 studies on the uptake of nitrate, ammonia, and amino acids by roots and microorganisms clearly showed that, shortly after nitrogen (N) mobilization from soil organic matter and litter, microorganisms take up most N. Lower Km values of microorganisms suggest that they are especially efficient at low N concentrations, but can also acquire more N at higher N concentrations (Vmax) compared with roots. Because of the unidirectional flow of nutrients from soil to roots, plants are the winners for N acquisition in the long run. Therefore, despite strong competition between roots and microorganisms for N, a temporal niche differentiation reflecting their generation times leads to mutualistic relationships in the rhizosphere. This temporal niche differentiation is highly relevant ecologically because it: protects ecosystems from N losses by leaching during periods of slow or no root uptake; continuously provides roots with available N according to plant demand; and contributes to the evolutionary development of mutualistic interactions between roots and microorganisms.
-
Early root overproduction not triggered by nutrients decisive for competitive success belowground
Padilla, F.M.; Mommer, L.; Caluwe, de H.; Smit-Tiekstra, A.E.; Wagemaker, C.A.M.; Ouborg, N.J.; Kroon, de H.
2013-01-01
Background - Theory predicts that plant species win competition for a shared resource by more quickly preempting the resource in hotspots and by depleting resource levels to lower concentrations than its competitors. Competition in natural grasslands largely occurs belowground, but information
-
Evolutionary responses of native plant species to invasive plants : a review
Oduor, Ayub M. O.
2013-01-01
Strong competition from invasive plant species often leads to declines in abundances and may,in certain cases, cause localized extinctions of native plant species. Nevertheless, studies have shown that certain populations of native plant species can co-exist with invasive plant species, suggesting the possibility of adaptive evolutionary responses of those populations to the invasive plants. Empirical inference of evolutionary responses of the native plant species to invasive plants has invol...
-
The competition of Linum with Camelia for minerals. 1
International Nuclear Information System (INIS)
Kranz, E.; Jacob, F.
1977-01-01
Both in monoculture and mixed culture, the uptake of 35 S sulphate into 20-day-old plants of Linum usitatissimum L. and Camelina sativa (L.) Crantz as well as 35 S transport from the root into the shoot of these plants were examined. In equal periods the Camelina plants took up essentially more sulphate of the nutrient solution than the Linum plants did. From among the two species, when standing in mixed culture, the Linum plants took up less sulphate ions than those in monoculture, whilst Camelina plants in mixed culture absorbed more sulphate ions than they did in monoculture. The differences of absorbed sulphate between monocultures and mixed cultures can be interpreted as the result of an inter-species competition for these ions. These findings support the opinion that the diminution of the dry weight of Linum under the influence of Camelina is caused decisively by competition and not by allelopathic factors. A participation of such factors, however, cannot be excluded. A diminished absorption of sulphate also took place in Linum plants having grown in a nutrient solution, in which Camelina plants already had been cultivated, but which mineral substances a new had been given to. The transportation of 35 S off the roots into shoot occured in either species under mixed culture conditions to a higher extent than in the respective monocultures. (author)
-
Competitive performance of transgenic wheat resistant to powdery mildew.
Directory of Open Access Journals (Sweden)
Olena Kalinina
Full Text Available Genetically modified (GM plants offer an ideal model system to study the influence of single genes that confer constitutive resistance to pathogens on the ecological behaviour of plants. We used phytometers to study competitive interactions between GM lines of spring wheat Triticum aestivum carrying such genes and control lines. We hypothesized that competitive performance of GM lines would be reduced due to enhanced transgene expression under pathogen levels typically encountered in the field. The transgenes pm3b from wheat (resistance against powdery mildew Blumeria graminis or chitinase and glucanase genes from barley (resistance against fungi in general were introduced with the ubiquitin promoter from maize (pm3b and chitinase genes or the actin promoter from rice (glucanase gene. Phytometers of 15 transgenic and non-transgenic wheat lines were transplanted as seedlings into plots sown with the same 15 lines as competitive environments and subject to two soil nutrient levels. Pm3b lines had reduced mildew incidence compared with control lines. Chitinase and chitinase/glucanase lines showed the same high resistance to mildew as their control in low-nutrient treatment and slightly lower mildew rates than the control in high-nutrient environment. Pm3b lines were weaker competitors than control lines. This resulted in reduced yield and seed number. The Pm3b line with the highest transgene expression had 53.2% lower yield than the control whereas the Pm3b line which segregated in resistance and had higher mildew rates showed only minor costs under competition. The line expressing both chitinase and glucanase genes also showed reduced yield and seed number under competition compared with its control. Our results suggest that single transgenes conferring constitutive resistance to pathogens can have ecological costs and can weaken plant competitiveness even in the presence of the pathogen. The magnitude of these costs appears related to the degree
-
Analysis of Traits Related to Weed Competitiveness in Sweet Corn (Zea mays L.
Directory of Open Access Journals (Sweden)
Natalia de Leon
2012-03-01
Full Text Available Weed management in sweet corn can be costly; genetic improvements in sweet corn competitiveness may reduce this expense. Competitive ability can exist as weed suppressive ability (WSA, or crop tolerance (CT. Previous studies in corn have found year of hybrid release, maturity, plant height, leaf angle and leafiness may affect WSA, while hybrid era, maturity, and plant height may affect CT. However, many of these studies were limited to very few genotypes. The objective of this study was to assess the effects of phenomorphological traits on sweet corn competitiveness and the inheritance of these traits. An incomplete half-diallel from seven historic sweet corn inbred lines of varying morphologies was evaluated in a split-block randomized complete block design in three environments. Forage sorghum was interplanted in half of the blocks to act as a model weed. Significant differences among hybrids were generally found for both phenomorphological traits and traits measuring WSA and CT, such as sorghum biomass and yield stability, respectively. Crop plant height was most predictive of WSA and CT. In this set of genotypes, competitive ability may be passed with reasonable fidelity from parent to offspring, suggesting that sweet corn could be bred for competitive ability.
-
Increasing the competitiveness of wind energy. New technologies for advanced wind predictability
International Nuclear Information System (INIS)
Bertolotti, Fabio
2013-01-01
The performance of thermal and nuclear power plants is assessed routinely and precisely, whereas the performance assessment of wind turbines is lagging far behind. This increases operational costs, reduces energy capture, and makes wind energy less competitive. The paper presents a technology and system with improved 24-h power forecasting, as well as condition monitoring of the rotor blades. The system can be employed by any wind power plant and offers potentials to increase the competitiveness of the power industry. (orig.)
-
Directory of Open Access Journals (Sweden)
mohammad javad babaie zarch
2017-09-01
Full Text Available Introduction Using crop species and cultivars with high competitive ability against weeds is one of the effective strategies for sustainable weed management. Emergence rate, rapid root growth, seed vigor, development rate of leaves, rapid root and shoot biomass accumulation, rapid canopy closure and plant height are important traits in relation to the competitiveness between different cultivars of crops. Competitive ability is measured using two indices including the weed growth prevention ability or weed biomass reduction index and crop tolerance to weed or yield reduction preventing index. The purpose of this study is to evaluate the competitive ability of six oilseed sunflower (Helianthus annuus L. cultivars and also introducing the most important morpho-physiological attributes affecting their competitive ability with tumble pigweed (Amaranthus albus L. in Birjand. Materials and methods This experiment was carried out as factorial layout based on randomized complete block design with three replications at the Agricultural Research Station, University of Birjand in 2012. Treatments were included six sunflower oilseed cultivars (Azargol, Jame esfehan, Farrokh, Syrna, Progress, Euroflor and tumble pigweed densities in four levels (zero (control, 5, 10 and 15 plants per square meter. The number of days and cumulative degree days were recorded from sowing to emergence. Plant height, leaf area and dry matter were recorded at four stages from emergence to 75 days after it. Sunflower seeds were harvested after physiological maturity. Preventing indices were used to evaluate the competitive ability of cultivars, competitive tolerance (Watson et al., 2002 and weed biomass. Data were analyzed with the SAS software and cluster analysis was performed using SPSS software. FLSD test was employed for comparison of the means at the 5% significance level. The graphs were prepared by Excel. Results and Discussion Analysis of variance showed that there was a
-
Burson, Amanda; Stomp, Maayke; Greenwell, Emma; Grosse, Julia; Huisman, Jef
2018-05-01
A key challenge in ecology is to understand how nutrients and light affect the biodiversity and community structure of phytoplankton and plant communities. According to resource competition models, ratios of limiting nutrients are major determinants of species composition. At high nutrient levels, however, species interactions may shift to competition for light, which might make nutrient ratios less relevant. The "nutrient-load hypothesis" merges these two perspectives, by extending the classic model of competition for two nutrients to include competition for light. Here, we test five key predictions of the nutrient-load hypothesis using multispecies competition experiments. A marine phytoplankton community sampled from the North Sea was inoculated in laboratory chemostats provided with different nitrogen (N) and phosphorus (P) loads to induce either single resource limitation or co-limitation of N, P, and light. Four of the five predictions were validated by the experiments. In particular, different resource limitations favored the dominance of different species. Increasing nutrient loads caused changes in phytoplankton species composition, even if the N:P ratio of the nutrient loads remained constant, by shifting the species interactions from competition for nutrients to competition for light. In all treatments, small species became dominant whereas larger species were competitively excluded, supporting the common view that small cell size provides a competitive advantage under resource-limited conditions. Contrary to expectation, all treatments led to coexistence of diatoms, cyanobacteria and green algae, resulting in a higher diversity of species than predicted by theory. Because the coexisting species comprised three phyla with different photosynthetic pigments, we speculate that niche differentiation in the light spectrum might play a role. Our results show that mechanistic resource competition models that integrate nutrient-based and light-based approaches
-
Qin, Rui-Min; Zheng, Yu-Long; Valiente-Banuet, Alfonso; Callaway, Ragan M; Barclay, Gregor F; Pereyra, Carlos Silva; Feng, Yu-Long
2013-02-01
There are many non-mutually exclusive mechanisms for exotic invasions but few studies have concurrently tested more than one hypothesis for the same species. Here, we tested the evolution of increased competitive ability (EICA) hypothesis in two common garden experiments in which Chromolaena odorata plants originating from native and nonnative ranges were grown in competition with natives from each range, and the novel weapons hypothesis in laboratory experiments with leachates from C. odorata. Compared with conspecifics originating from the native range, C. odorata plants from the nonnative range were stronger competitors at high nutrient concentrations in the nonnative range in China and experienced far more herbivore damage in the native range in Mexico. In both China and Mexico, C. odorata was more suppressed by species native to Mexico than by species native to China. Species native to China were much more inhibited by leaf extracts from C. odorata than species from Mexico, and this difference in allelopathic effects may provide a possible explanation for the biogeographic differences in competitive ability. Our results indicate that EICA, innate competitive advantages, and novel biochemical weapons may act in concert to promote invasion by C. odorata, and emphasize the importance of exploring multiple, non-mutually exclusive mechanisms for invasions. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.
-
Sediment type affects competition between a native and an exotic species in coastal China.
Li, Hong-Li; Wang, Yong-Yang; An, Shu-Qing; Zhi, Ying-Biao; Lei, Guang-Chun; Zhang, Ming-Xiang
2014-10-23
Different types of sediments in salt marsh have different physical and chemical characters. Thus sediment type plays a role in plant competition and growth in salt marsh ecosystems. Spartina anglica populations have been increasingly confined to upper elevation gradients of clay, and the niche sediment has changed. Because the niches of S. anglica and the native species Scirpus triqueter overlap, we conducted a greenhouse experiment to test the hypothesis that plant competition has changed under different types of sediments. Biomass and asexual reproduction were analyzed, and inter- and intraspecific competition was measured by log response ratio for the two species in both monoculture and combination under three sediment types (sand, clay and mixture of sand and clay). For S. anglica, biomass, ramet number and rhizome length in combination declined significantly compared with those in monoculture, and the intensity of interspecific competition was significantly higher than that of intraspecific competition under all sediments. For S. triqueter, the intensities of intra- and interspecific competition were not significantly different. This indicates that S. triqueter exerts an asymmetric competitive advantage over S. anglica across all sediments, but especially clay. Thus the sediment type changes competition between S. anglica and S. triqueter.
-
Interspecific Competition Underlying Mutualistic Networks
Maeng, Seong Eun; Lee, Jae Woo; Lee, Deok-Sun
2012-03-01
Multiple classes of interactions may exist affecting one another in a given system. For the mutualistic networks of plants and pollinating animals, it has been known that the degree distribution is broad but often deviates from power-law form more significantly for plants than animals. To illuminate the origin of such asymmetry, we study a model network in which links are assigned under generalized preferential-selection rules between two groups of nodes and find the sensitive dependence of the resulting connectivity pattern on the model parameters. The nonlinearity of preferential selection can come from interspecific interactions among animals and among plants. The model-based analysis of real-world mutualistic networks suggests that a new animal determines its partners not only by their abundance but also under the competition with existing animal species, which leads to the stretched-exponential degree distributions of plants.
-
Effects of combination of leaf resources on competition in container mosquito larvae.
Reiskind, M H; Zarrabi, A A; Lounibos, L P
2012-08-01
Resource diversity is critical to fitness in many insect species, and may determine the coexistence of competitive species and the function of ecosystems. Plant material provides the nutritional base for numerous aquatic systems, yet the consequences of diversity of plant material have not been studied in aquatic container systems important for the production of mosquitoes. To address how diversity in leaf detritus affects container-inhabiting mosquitoes, we examined how leaf species affect competition between two container inhabiting mosquito larvae, Aedes aegypti and Aedes albopictus, that co-occur in many parts of the world. We tested the hypotheses that leaf species changes the outcome of intra- and interspecific competition between these mosquito species, and that combinations of leaf species affect competition in a manner not predictable based upon the response to each leaf species alone (i.e. the response to leaf combinations is non-additive). We find support for our first hypothesis that leaf species can affect competition, evidence that, in general, leaf combination alters competitive interactions, and no support that leaf combination impacts interspecific competition differently than intraspecific competition. We conclude that combinations of leaves increase mosquito production non-additively such that combinations of leaves act synergistically, in general, and result in higher total yield of adult mosquitoes in most cases, although certain leaf combinations for A. albopictus are antagonistic. We also conclude that leaf diversity does not have a different effect on interspecific competition between A. aegypti and A. albopictus, relative to intraspecific competition for each mosquito.
-
Mercer, Kristin L; Emry, D Jason; Snow, Allison A; Kost, Matthew A; Pace, Brian A; Alexander, Helen M
2014-01-01
Understanding the likelihood and extent of introgression of novel alleles in hybrid zones requires comparison of lifetime fitness of parents and hybrid progeny. However, fitness differences among cross types can vary depending on biotic conditions, thereby influencing introgression patterns. Based on past work, we predicted that increased competition would enhance introgression between cultivated and wild sunflower (Helianthus annuus) by reducing fitness advantages of wild plants. To test this prediction, we established a factorial field experiment in Kansas, USA where we monitored the fitness of four cross types (Wild, F1, F2, and BCw hybrids) under different levels of interspecific and intraspecific competition. Intraspecific manipulations consisted both of density of competitors and of frequency of crop-wild hybrids. We recorded emergence of overwintered seeds, survival to reproduction, and numbers of seeds produced per reproductive plant. We also calculated two compound fitness measures: seeds produced per emerged seedling and seeds produced per planted seed. Cross type and intraspecific competition affected emergence and survival to reproduction, respectively. Further, cross type interacted with competitive treatments to influence all other fitness traits. More intense competition treatments, especially related to density of intraspecific competitors, repeatedly reduced the fitness advantage of wild plants when considering seeds produced per reproductive plant and per emerged seedling, and F2 plants often became indistinguishable from the wilds. Wild fitness remained superior when seedling emergence was also considered as part of fitness, but the fitness of F2 hybrids relative to wild plants more than quadrupled with the addition of interspecific competitors and high densities of intraspecific competitors. Meanwhile, contrary to prediction, lower hybrid frequency reduced wild fitness advantage. These results emphasize the importance of taking a full life cycle
-
Directory of Open Access Journals (Sweden)
Kristin L Mercer
Full Text Available Understanding the likelihood and extent of introgression of novel alleles in hybrid zones requires comparison of lifetime fitness of parents and hybrid progeny. However, fitness differences among cross types can vary depending on biotic conditions, thereby influencing introgression patterns. Based on past work, we predicted that increased competition would enhance introgression between cultivated and wild sunflower (Helianthus annuus by reducing fitness advantages of wild plants. To test this prediction, we established a factorial field experiment in Kansas, USA where we monitored the fitness of four cross types (Wild, F1, F2, and BCw hybrids under different levels of interspecific and intraspecific competition. Intraspecific manipulations consisted both of density of competitors and of frequency of crop-wild hybrids. We recorded emergence of overwintered seeds, survival to reproduction, and numbers of seeds produced per reproductive plant. We also calculated two compound fitness measures: seeds produced per emerged seedling and seeds produced per planted seed. Cross type and intraspecific competition affected emergence and survival to reproduction, respectively. Further, cross type interacted with competitive treatments to influence all other fitness traits. More intense competition treatments, especially related to density of intraspecific competitors, repeatedly reduced the fitness advantage of wild plants when considering seeds produced per reproductive plant and per emerged seedling, and F2 plants often became indistinguishable from the wilds. Wild fitness remained superior when seedling emergence was also considered as part of fitness, but the fitness of F2 hybrids relative to wild plants more than quadrupled with the addition of interspecific competitors and high densities of intraspecific competitors. Meanwhile, contrary to prediction, lower hybrid frequency reduced wild fitness advantage. These results emphasize the importance of taking
-
Mercer, Kristin L.; Emry, D. Jason; Snow, Allison A.; Kost, Matthew A.; Pace, Brian A.; Alexander, Helen M.
2014-01-01
Understanding the likelihood and extent of introgression of novel alleles in hybrid zones requires comparison of lifetime fitness of parents and hybrid progeny. However, fitness differences among cross types can vary depending on biotic conditions, thereby influencing introgression patterns. Based on past work, we predicted that increased competition would enhance introgression between cultivated and wild sunflower (Helianthus annuus) by reducing fitness advantages of wild plants. To test this prediction, we established a factorial field experiment in Kansas, USA where we monitored the fitness of four cross types (Wild, F1, F2, and BCw hybrids) under different levels of interspecific and intraspecific competition. Intraspecific manipulations consisted both of density of competitors and of frequency of crop-wild hybrids. We recorded emergence of overwintered seeds, survival to reproduction, and numbers of seeds produced per reproductive plant. We also calculated two compound fitness measures: seeds produced per emerged seedling and seeds produced per planted seed. Cross type and intraspecific competition affected emergence and survival to reproduction, respectively. Further, cross type interacted with competitive treatments to influence all other fitness traits. More intense competition treatments, especially related to density of intraspecific competitors, repeatedly reduced the fitness advantage of wild plants when considering seeds produced per reproductive plant and per emerged seedling, and F2 plants often became indistinguishable from the wilds. Wild fitness remained superior when seedling emergence was also considered as part of fitness, but the fitness of F2 hybrids relative to wild plants more than quadrupled with the addition of interspecific competitors and high densities of intraspecific competitors. Meanwhile, contrary to prediction, lower hybrid frequency reduced wild fitness advantage. These results emphasize the importance of taking a full life cycle
-
Crested wheatgrass-cheatgrass seedling competition in a mixed-density design
Francis, Mark G.; Pyke, David A.
1996-01-01
Plant competition experiments have historically used designs that are difficult to interpret due to confounding problems. Recently, designs based on a 'response function' approach have been proposed and tested in various plant mixture settings. For this study, 3 species were used that are important in current revegetation practices in the Intermountain West. 'Nordan' (Agropyron desertorum [Fish. ex Link] Shult.) and 'Hycrest' (A. cristatum [L.] Gaertn. x desertorum) crested wheatgrass are commonly-used revegetation species on rangelands susceptible to cheatgrass (Bromus tectorum L.) invasion, although little quantitative data exist that compare their competitive abilities. We evaluated the competitive ability of Hycrest and Nordan seedlings in 2-species mixtures with cheatgrass in a greenhouse study. Linear and nonlinear models were developed for a range of densities (130- 520 seeds m-2) for each species to predict median above-ground biomass and tiller numbers and to further test the usefulness of this design for evaluating species to rehabilitate rangelands. In both experiments, increasing Hycrest and Nordan densities reduced their own biomass and tiller production while increasing Hycrest densities reduced cheatgrass biomass and tiller production. Nordan did not affect cheatgrass biomass and tiller production. However, increasing cheatgrass densities reduced Hycrest and Nordan biomass and tiller production, and its own biomass and tiller production. The competition index i.e. substitution rate, indicated that Hycrest seedlings were better competitors with cheatgrass than Nordan, although in all mixtures, cheatgrass plants were the superior competitors. Further field research using this design, where environmental inputs are less optimal and diverse, is needed to validate these results and to further evaluate the use of this approach in examining effects of intra- and interspecific competition.
-
Friede, Martina; Unger, Stephan; Hellmann, Christine; Beyschlag, Wolfram
2016-01-01
Interactions of plants with arbuscular mycorrhizal fungi (AMF) may range along a broad continuum from strong mutualism to parasitism, with mycorrhizal benefits received by the plant being determined by climatic and edaphic conditions affecting the balance between carbon costs vs. nutritional benefits. Thus, environmental conditions promoting either parasitism or mutualism can influence the mycorrhizal growth dependency (MGD) of a plant and in consequence may play an important role in plant-plant interactions. In a multifactorial field experiment we aimed at disentangling the effects of environmental and edaphic conditions, namely the availability of light, phosphorus and nitrogen, and the implications for competitive interactions between Hieracium pilosella and Corynephorus canescens for the outcome of the AMF symbiosis. Both species were planted in single, intraspecific and interspecific combinations using a target-neighbor approach with six treatments distributed along a gradient simulating conditions for the interaction between plants and AMF ranking from mutualistic to parasitic. Across all treatments we found mycorrhizal association of H. pilosella being consistently mutualistic, while pronounced parasitism was observed in C. canescens, indicating that environmental and edaphic conditions did not markedly affect the cost:benefit ratio of the mycorrhizal symbiosis in both species. Competitive interactions between both species were strongly affected by AMF, with the impact of AMF on competition being modulated by colonization. Biomass in both species was lowest when grown in interspecific competition, with colonization being increased in the less mycotrophic C. canescens, while decreased in the obligate mycotrophic H. pilosella. Although parasitism-promoting conditions negatively affected MGD in C. canescens, these effects were small as compared to growth decreases related to increased colonization levels in this species. Thus, the lack of plant control over
-
Directory of Open Access Journals (Sweden)
Martina Friede
2016-09-01
Full Text Available Interactions of plants with arbuscular mycorrhizal fungi (AMF may range along a broad continuum from strong mutualism to parasitism, with mycorrhizal benefits received by the plant being determined by climatic and edaphic conditions affecting the balance between carbon costs vs. nutritional benefits. Thus, environmental conditions promoting either parasitism or mutualism can influence the mycorrhizal growth dependency (MGD of a plant and in consequence may play an important role in plant-plant interactions.In a multifactorial field experiment we aimed at disentangling the effects of environmental and edaphic conditions, namely the availability of light, phosphorus and nitrogen, and the implications for competitive interactions between Hieracium pilosella and Corynephorus canescens for the outcome of the AMF symbiosis. Both species were planted in single, intraspecific and interspecific combinations using a target-neighbor approach with six treatments distributed along a gradient simulating conditions for the interaction between plants and AMF ranking from mutualistic to parasitic.Across all treatments we found mycorrhizal association of H. pilosella being consistently mutualistic, while pronounced parasitism was observed in C. canescens, indicating that environmental and edaphic conditions did not markedly affect the cost:benefit ratio of the mycorrhizal symbiosis in both species. Competitive interactions between both species were strongly affected by AMF, with the impact of AMF on competition being modulated by colonization. Biomass in both species was lowest when grown in interspecific competition, with colonization being increased in the less mycotrophic C. canescens, while decreased in the obligate mycotrophic H. pilosella. Although parasitism-promoting conditions negatively affected MGD in C. canescens, these effects were small as compared to growth decreases related to increased colonization levels in this species. Thus, the lack of plant
-
Competition between roots and microorganisms for nitrogen: mechanisms and ecological relevance.
Kuzyakov, Yakov; Xu, Xingliang
2013-05-01
Demand of all living organisms on the same nutrients forms the basis for interspecific competition between plants and microorganisms in soils. This competition is especially strong in the rhizosphere. To evaluate competitive and mutualistic interactions between plants and microorganisms and to analyse ecological consequences of these interactions, we analysed 424 data pairs from 41 (15)N-labelling studies that investigated (15)N redistribution between roots and microorganisms. Calculated Michaelis-Menten kinetics based on K(m) (Michaelis constant) and V(max) (maximum uptake capacity) values from 77 studies on the uptake of nitrate, ammonia, and amino acids by roots and microorganisms clearly showed that, shortly after nitrogen (N) mobilization from soil organic matter and litter, microorganisms take up most N. Lower K(m) values of microorganisms suggest that they are especially efficient at low N concentrations, but can also acquire more N at higher N concentrations (V(max)) compared with roots. Because of the unidirectional flow of nutrients from soil to roots, plants are the winners for N acquisition in the long run. Therefore, despite strong competition between roots and microorganisms for N, a temporal niche differentiation reflecting their generation times leads to mutualistic relationships in the rhizosphere. This temporal niche differentiation is highly relevant ecologically because it: protects ecosystems from N losses by leaching during periods of slow or no root uptake; continuously provides roots with available N according to plant demand; and contributes to the evolutionary development of mutualistic interactions between roots and microorganisms. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.
-
The influence of sward competition on shoot growth and ...
African Journals Online (AJOL)
In each of two seasons the growth form of Senecio retrorsus plants in Natal Tall Grassveld differed in accordance with the degree of utilization of the grasses and thus the degree of competition offered. In rested veld the main stems of seedlings and mature plants were long and spindly while those in frequently clipped veld ...
-
Tokuda, Nanako; Hattori, Mitsuru; Abe, Kota; Shinohara, Yoshinori; Nagano, Yusuke; Itino, Takao
2015-01-01
Plant?plant interspecific competition via pollinators occurs when the flowering seasons of two or more plant species overlap and the pollinator fauna is shared. Negative sexual interactions between species (reproductive interference) through improper heterospecific pollen transfer have recently been reported between native and invasive species demonstrating pollination-driven competition. We focused on two native Impatiens species (I.?noli-tangere and I.?textori) found in Japan and examined w...
-
Approaches to Assess Competitiveness of Small and Medium Sized Reactors
International Nuclear Information System (INIS)
Kuznetsov, V.; Barkatullah, N.
2011-01-01
There is continuing interest in Member States concerning the development and application of small and medium sized reactors (SMRs), i.e., reactors with the equivalent electric power of less than 700 MW. Currently, developed SMRs are in most cases intended for markets different than those in which large nuclear power plants operate. Such markets have essentially different investment requirements, siting flexibility, grid connections and infrastructure restrictions. Therefore, economic factors affecting the competitiveness or competition of SMRs in such markets would also be different from those observed in established markets for electricity production. For example, investment capability may be limited, which would favour capacity addition in smaller increments; grids may be small or weak, which would favour capacities exactly matching the demand; infrastructure and human resource may be insufficient, which would favour less complex operation and maintenance requirements; and non-electrical energy products, such as potable water, may be in demand, which would favour reasonably close plant location to the customer. In practice it is futile to compare a single SMR needs to a single larger capacity plant on an economy of scale basis because SMRs are suitable for those locations that might not be appropriate for larger plants. However, a series of SMRs could be considered comparable to fewer larger plants to achieve the same overall power station capacity. In this case, SMRs have a potential to be competitive by employing alternative design strategies, taking advantage of smaller reactor size, offering a less complex design and operation and maintenance, relying on deployment-in-series approaches, taking an advantage of the accelerated learning, multiple unit factors and shorter construction duration. Reflecting on developments in member states, the International Atomic Energy Agency (IAEA) is finalizing the preparation of a report highlighting the economics and
-
Competition as a mechanism structuring mutualisms
Robert J. Warren; Itamar Giladi; Mark A. Bradford
2014-01-01
Summary 1. Hutchinsonian niche theory posits that organisms have fundamental abiotic resource requirements from which they are limited by competition. Organisms also have fundamental biotic requirements, such as mutualists, for which they also might compete. 2. We test this idea with a widespread antâplant mutualism. Ant-mediated seed dispersal (myrmecochory) in...
-
Radtke, A; Mosner, E; Leyer, I
2012-03-01
While several studies on regeneration in Salicaceae have focused on seedling recruitment, little is known about factors controlling their vegetative reproduction. In two greenhouse experiments, we studied the response of floodplain willows (Salix fragilis, S. viminalis, S. triandra) to competition with Poa trivialis, and to shoot and root removal when planted as vegetative cuttings. In the first experiment, growth performance variables were analysed in relation to full competition, shoot competition, root competition and control, taking into account two different water levels. After 9 weeks, shoots were removed and the resprouting capacity of the bare cuttings was recorded. In the second experiment, the cutting performance of the three floodplain and an additional two fen willow species (S. cinerea, S. aurita) was compared when grown in three different soil compositions and with two different water levels. After 9 weeks, shoot and root biomass was removed and the bare cuttings were replanted to test their ability to resprout. Cutting performance and secondary resprouting were negatively affected by full and shoot competition while root competition had no or weak effects. The floodplain species performed better than the fen species in all soil types and water levels. Secondary resprouting capacity was also higher in the floodplain species, which showed an additional strong positive response to the previous waterlogging treatment. The results contribute to understanding of the vegetative regeneration ecology of floodplain willows, and suggest that the use of vegetative plantings in restoration plantings could be an effective strategy for recovering floodplain forests. © 2011 German Botanical Society and The Royal Botanical Society of the Netherlands.
-
Directory of Open Access Journals (Sweden)
Catherine A. Gehring
2014-06-01
Full Text Available Plants and mycorrhizal fungi influence each other’s abundance, diversity and distribution. How other biotic interactions affect the mycorrhizal symbiosis is less well understood. Likewise, we know little about the effects of climate change on the fungal component of the symbiosis or its function. We synthesized our long-term studies on the influence of mistletoe parasites, insect herbivores, competing trees, and drought on the ectomycorrhizal fungal communities associated with a foundation tree species of the southwestern United States, pinyon pine (Pinus edulis, and described how these changes feed back to affect host plant performance. We found that drought and all three of the biotic interactions studied resulted in similar shifts in ectomycorrhizal fungal community composition, demonstrating a convergence of the community towards dominance by a few closely related fungal taxa. Ectomycorrhizal fungi responded similarly to each of these stressors resulting in a predictable trajectory of community disassembly, consistent with ecological theory. Although we predicted that the fungal communities associated with trees stressed by drought, herbivory, competition, and parasitism would be poor mutualists, we found the opposite pattern in field studies. Our results suggest that climate change and the increased importance of herbivores, competitors and parasites that can be associated with it, may ultimately lead to reductions in ectomycorrhizal fungal diversity, but that the remaining fungal community may be beneficial to host trees under the current climate and the warmer, drier climate predicted for the future.
-
Three Studies in Industrial Economics: Competition and Industry Structure
Keil, Jan
Chapter 1 reviews alternative theories of competition - the standard Neoclassical view, the contribution of the Chicago School as well as the two dynamic lines of thought which are part of Austrian economics and Classical Political Economy. The latter is presented as a consistent alternative to the other existing theories. Of special interest is the question if and how industry structure matters in these approaches, how profitability differentials are explained and what role market share concentration and mobility barriers play. Their predictions and implications for empirical research are compared. Ways to test and evaluate these different approaches are described. Chapter 2 investigates econometrically how industry and micro level variables determine persistent differentials in the rate of return on assets in the U.S. The analysis is the first to use business segment data to explain long term profitability differentials. It presents new market concentration indicators that are superior to concentration ratios and allow to analyze an unpreceded amount of concentration and other data back to 1977. Critical concentration levels, non-linearities, interaction effects and previously ignored important control variables like industrial unionization are being considered. Concentration is found to have significant negative effects on profitability differentials. Barrier indicators are insignificant while market shares are positively correlated with long-run profitability. Concentration thus increases, not diminishes the degree of industrial competition. This is interpreted as evidence in support of Classical Political Economic competition theory. Chapter 3 presents a costs of production based industry analytical study that aims at consistency with Classical Political Economic thought. It investigates how growth of renewable electricity in Germany forces conventional power plants to shift towards more flexible operating regimes. The simulation of individual power plant load
-
Adachi, Paul J C; Willoughby, Teena
2013-07-01
The majority of research on the link between video games and aggression has focused on the violent content in games. In contrast, recent experimental research suggests that it is video game competition, not violence, that has the greatest effect on aggression in the short-term. However, no researchers have examined the long-term relationship between video game competition and aggression. In addition, if competition in video games is a significant reason for the link between video game play and aggression, then other competitive activities, such as competitive gambling, also may predict aggression over time. In the current study, we directly assessed the socialization (competitive video game play and competitive gambling predicts aggression over time) versus selection hypotheses (aggression predicts competitive video game play and competitive gambling over time). Adolescents (N = 1,492, 50.8 % female) were surveyed annually from Grade 9 to Grade 12 about their video game play, gambling, and aggressive behaviors. Greater competitive video game play and competitive gambling predicted higher levels of aggression over time, after controlling for previous levels of aggression, supporting the socialization hypothesis. The selection hypothesis also was supported, as aggression predicted greater competitive video game play and competitive gambling over time, after controlling for previous competitive video game play and competitive gambling. Our findings, taken together with the fact that millions of adolescents play competitive video games every day and that competitive gambling may increase as adolescents transition into adulthood, highlight the need for a greater understanding of the relationship between competition and aggression.
-
Directory of Open Access Journals (Sweden)
Telma Passini
2003-01-01
Full Text Available Methodologies of competitive interaction quantification between weeds and crops are not widely elucidated and compared in the literature. The competitive ability of common-bean (Phaseolus vulgaris relative to alexandergrass (Brachiaria plantaginea was assessed and two approaches of replacement series experiment analysis were compared. The response of the species to the presence of each other at different densities and proportion was evaluated. Replacement series at total densities of 625, 816 and 1,111 plants m-2 were performed at the proportions of common-bean:alexandergrass of 100:0 (pure stand of common-bean, 75:25, 50:50, 25:75 and 0:100% (pure stand of alexandergrass, at four replicates in a randomized block design. Data analyses were performed by the qualitative compared to the quantitative approach. The quantitative approach provided larger number of information than did the qualitative approach, and indicated that there was intraspecific competition among common-bean plants, and a minimum of interspecific competition from alexandergrass. There was no intraspecific competition among alexandergrass plants, being the crop effect on the weed larger than the effect among alexandergrass plants. The ecological niche differentiation was partial, since the crop intraspecific competition was larger than the interspecific, and the last one was negligible, at the same time that the weed interspecific competition was larger than the intraspecific. Common-bean, as a competitor species, is superior to alexandergrass.As metodologias de quantificação das interações competitivas entre plantas cultivadas e daninhas não estão amplamente elucidadas e comparadas na literatura. A competitividade da cultura de feijão-comum (Phaseolus vulgaris em relação ao capim-marmelada (Brachiaria plantaginea foi avaliada pela comparação entre o método qualitativo e um método quantitativo de análise de resultados. A resposta de cada espécie à presença da
-
The effect of counter-trading on competition in electricity markets
International Nuclear Information System (INIS)
Dijk, Justin; Willems, Bert
2011-01-01
In a competitive electricity market, nodal pricing is the most efficient way to manage congestion. Counter-trading is inefficient as it gives the wrong long term signals for entry and exit of power plants. However, in a non-competitive market, additional entry will improve the competitiveness of the market, and will increase social benefit by reducing price-cost margins. This paper studies whether the potential pro-competitive entry effects could make counter-trading more efficient than nodal pricing. We find that this is unlikely to be the case, and expect counter-trading to have a negative effect on overall welfare. The potential benefits of additional competition (more competitive prices and lower production cost) do not outweigh the distortions (additional investment cost for the entrant, and socialization of the congestion cost to final consumers). - Research highlights: → 'Counter-trading' and 'nodal pricing' manage congestion in electric grids. → Nodal pricing gives superior locational prices. → Counter-trading induces extra investments in regions with a production surplus. → Extra investments improve competition, but are expected to be socially inefficient.
-
Gas and coal competition in the EU Power Sector
International Nuclear Information System (INIS)
Cornot-Gandolphe, Sylvie
2014-06-01
Despite its many assets, a confluence of factors - including flat electricity demand, rising use of renewable energy sources, falling wholesale electricity market prices, high gas prices relative to coal and low CO 2 prices - has eroded the competitiveness of natural gas in the EU power sector. The share of natural gas in the EU electricity mix has decreased from 23% in 2010 to 20.5% in 2012. By contrast, coal-fired power stations have been operating at high loads, increasing coal demand by the sector. This thorough analysis by CEDIGAZ of gas, coal and CO 2 dynamics in the context of rising renewables is indispensable to understand what is at stake in the EU power sector and how it will affect future European gas demand. Main findings of the report: - Coal is likely to retain its cost advantage into the coming decade: The relationship between coal, gas and CO 2 prices is a key determinant of the competition between gas and coal in the power sector and will remain the main driver of fuel switching. A supply glut on the international coal market (partly because of an inflow of US coal displaced by shale gas) has led to a sharp decline in coal prices while gas prices, still linked to oil prices to a significant degree, have increased by 42% since 2010. At the same time, CO 2 prices have collapsed, reinforcing coal competitiveness. Our analysis of future trends in coal, gas and CO 2 prices suggests that coal competitive advantage may well persist into the coming decade. - But coal renaissance may still be short-lived: Regulations on emissions of local pollutants, i.e. the Large Plant Combustion Directive (LCPD) and the Industrial Emissions Directive (IED) that will succeed it in 2016, will lead to the retirement of old, inefficient coal-fired power plants. Moreover, the rapid development of renewables, which so far had only impacted gas-fired power plants is starting to take its toll on hard coal plants' profitability. This trend is reinforced by regulation at EU or
-
Intransitive competition is widespread in plant communities and maintains their species richness.
Soliveres, Santiago; Maestre, Fernando T; Ulrich, Werner; Manning, Peter; Boch, Steffen; Bowker, Matthew A; Prati, Daniel; Delgado-Baquerizo, Manuel; Quero, José L; Schöning, Ingo; Gallardo, Antonio; Weisser, Wolfgang; Müller, Jörg; Socher, Stephanie A; García-Gómez, Miguel; Ochoa, Victoria; Schulze, Ernst-Detlef; Fischer, Markus; Allan, Eric
2015-08-01
Intransitive competition networks, those in which there is no single best competitor, may ensure species coexistence. However, their frequency and importance in maintaining diversity in real-world ecosystems remain unclear. We used two large data sets from drylands and agricultural grasslands to assess: (1) the generality of intransitive competition, (2) intransitivity-richness relationships and (3) effects of two major drivers of biodiversity loss (aridity and land-use intensification) on intransitivity and species richness. Intransitive competition occurred in > 65% of sites and was associated with higher species richness. Intransitivity increased with aridity, partly buffering its negative effects on diversity, but was decreased by intensive land use, enhancing its negative effects on diversity. These contrasting responses likely arise because intransitivity is promoted by temporal heterogeneity, which is enhanced by aridity but may decline with land-use intensity. We show that intransitivity is widespread in nature and increases diversity, but it can be lost with environmental homogenisation. © 2015 John Wiley & Sons Ltd/CNRS.
-
Energy Technology Data Exchange (ETDEWEB)
Roesgen, Peter
2013-08-01
Due to dynamic price adjustment clauses 'virtual power plant sections' enable long-term contracts although the future costs of electricity production at the time of the conclusion of the contract are not predictable. Nevertheless, power plant sections gain of considerable importance due to the increasing spread in the energy industry practice. At first, the author of the book under consideration describes the different types of virtual power plant sections as well as the necessary complex economic and technical backgrounds. The competitive analysis of virtual power plant sections is the focus of this book. An orientation guide will be developed in the first part of this competitive analysis. With this it can be determined whether a virtual power plant section is qualified as a noticeable restriction of competition. The second part of this competitive analysis examines the extent to which virtual power plant sections may violate the prohibition of abuse of a market dominant position with respect to Article 102 AEUV (Treaty on the Functioning of the European Union) and ate paragraph paragraph 19 et seq. GWB (Law against the Restriction of Competition).
-
Tuelher, Edmar S; Silva, Éder H; Hirose, Edson; Guedes, Raul Narciso C; Oliveira, Eugênio E
2016-10-01
The abundance and contribution of the neotropical brown stink bug, Euschistus heros (F.), and the redbanded stink bug, Piezodorus guildinii (West.), to the composition of insect pests of soybean, Glycine max (L.), fields have changed both spatially and temporally in neotropical soybean production areas. Therefore, we assessed the competitiveness of each species in direct competition experiments following an additive series. We performed mixed (adult) insect infestations in soybean plants and evaluated the fitness of each species and the soybean yield. While the competitive ability of E. heros was significantly compromised by increments in conspecifics and heterospecifics (i.e. P. guildinii), the competitive ability of P. guildinii was compromised by the presence of heterospecifics (i.e. E. heros). The reproductive output of P. guildinii remained unaffected by increments in E. heros or of P. guildinii. Intriguingly, despite the fact that P. guildinii apparently lost the competition with E. heros, almost no pod production was observed in any plant colonised by the former. The higher abundance of E. heros in neotropical soybean fields seems to result from higher competitive ability than its heterospecific competitor P. guildinii, which may prevent the higher losses caused by P. guildinii. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.
-
Carbon dioxide recovery from gas-fired power plants
Energy Technology Data Exchange (ETDEWEB)
Martins, Ricardo Salgado; Barbosa, Joao Roberto [Centro Tecnico Aeroespacial, Sao Jose dos Campos, SP (Brazil). Inst. Tecnologico de Aeronautica. Dept. de Energia]. E-mails: martinsr@epenergy.com; barbosa@mec.ita.br; Prado, Eduardo Lanari [Rice Univ., Houston, TX (United States). Jones Graduate School of Business]. E-mail: pradoe@epenergy.com; Vieira, Adriana de Moura [Instituto Brasileiro de Mercado de Capitais (IBMEC), Rio de Janeiro, RJ (Brazil). Dept. de Financas]. E-mail: vieiraa@epenergy.com
2000-07-01
Since 1996 the Brazilian electric sector has undergone a major restructuring. The aim of such change is to reduce the State's participation in the sector, and to induce the growth of private investments. In particular, this event created several opportunities for thermal power plant projects, leading to competition at the generation level. In this scenario of increased competition, the power plant efficiency becomes a key element for determining the feasibility and profitability of the project. Moreover, the utilization of the plant's own effluents as feedstock or as a source of additional revenue will impact positively in its economics. As an example, long term additional revenues could be created by the sale of CO{sub 2} extracted from the combustion products of thermal power plants. The production of CO{sub 2} also contributes to mitigate the environmental impacts of the power plant project by significantly reducing its airborne emissions. This paper shows how a gas-fired power plant can extract and utilize CO{sub 2} to generate additional revenue, contributing to a more competitive power plant. (author)
-
Schwinning, Susanne; Meckel, Heather; Reichmann, Lara G; Polley, H Wayne; Fay, Philip A
2017-01-01
Invasive plant species often dominate native species in competition, augmenting other potential advantages such as release from natural enemies. Resource pre-emption may be a particularly important mechanism for establishing dominance over competitors of the same functional type. We hypothesized that competitive success of an exotic grass against native grasses is mediated by establishing an early size advantage. We tested this prediction among four perennial C4 warm-season grasses: the exotic weed Johnsongrass (Sorghum halepense), big bluestem (Andropogon gerardii), little bluestem (Schizachyrium scoparius) and switchgrass (Panicum virgatum). We predicted that a) the competitive effect of Johnsongrass on target species would be proportional to their initial biomass difference, b) competitive effect and response would be negatively correlated and c) soil fertility would have little effect on competitive relationships. In a greenhouse, plants of the four species were grown from seed either alone or with one Johnsongrass neighbor at two fertilizer levels and periodically harvested. The first two hypotheses were supported: The seedling biomass of single plants at first harvest (50 days after seeding) ranked the same way as the competitive effect of Johnsongrass on target species: Johnsongrass critical mechanism by which exotic invasive species displace functionally similar native species and alter the functional dynamics of native communities.
-
Song, Mengya; Yu, Lei; Jiang, Yonglei; Lei, Yanbao; Korpelainen, Helena; Niinemets, Ülo; Li, Chunyang
2017-06-01
In this study, intra- and interspecific competition were investigated in early successional Salix rehderiana Schneider and later-appearing Populus purdomii Rehder under non-fertilized (control) and nitrogen (N)-fertilized conditions in the Hailuogou glacier retreat area. Our aim was to discover whether N is a key factor in plant-plant competition and whether N drives the primary succession process in a glacier retreat area. We analyzed differences in responses to intra- and interspecific competition and N fertilization between P. purdomii and S. rehderiana, including parameters such as biomass accumulation, nutrient absorption, non-structural carbohydrates, photosynthetic capacity, hydrolysable amino acids and leaf ultrastructure. In the control treatments, S. rehderiana individuals subjected to interspecific competition benefited from the presence of P. purdomii plants, as indicated by higher levels of biomass accumulation, photosynthetic capacity, N absorption, amino acid contents and photosynthetic N-use efficiency. However, in the N-fertilized treatments, P. purdomii individuals exposed to interspecific competition benefited from the presence of S. rehderiana plants, as shown by a higher growth rate, enhanced carbon gain capacity, greater amino acid contents, and elevated water-use efficiency, whereas the growth of S. rehderiana was significantly reduced. Our results demonstrate that N plays a pivotal role in determining the asymmetric competition pattern among Salicaceae species during primary succession. We argue that the interactive effects of plant-plant competition and N availability are key mechanisms that drive primary succession in the Gongga Mountain glacier retreat area. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
-
Benchmarking Nuclear Power Plants
International Nuclear Information System (INIS)
Jakic, I.
2016-01-01
One of the main tasks an owner have is to keep its business competitive on the market while delivering its product. Being owner of nuclear power plant bear the same (or even more complex and stern) responsibility due to safety risks and costs. In the past, nuclear power plant managements could (partly) ignore profit or it was simply expected and to some degree assured through the various regulatory processes governing electricity rate design. It is obvious now that, with the deregulation, utility privatization and competitive electricity market, key measure of success used at nuclear power plants must include traditional metrics of successful business (return on investment, earnings and revenue generation) as well as those of plant performance, safety and reliability. In order to analyze business performance of (specific) nuclear power plant, benchmarking, as one of the well-established concept and usual method was used. Domain was conservatively designed, with well-adjusted framework, but results have still limited application due to many differences, gaps and uncertainties. (author).
-
Will competition crush America's NPPs?
International Nuclear Information System (INIS)
Anon.
1997-01-01
Economic issues affecting continued nuclear power plant operation are discussed. A list of 20 units believed to be at risk of shutdown is presented, with pertinent data and commentary for each plant. Estimates of early closures due to competitive issues are made; 10-15 units in the next few years is stated as the best estimate, while up to 27 unit shutdowns are expected to be a worst case number. High operating costs are identified as the most significant risk factor in early closure. The effects of size, age, single unit status, capacity factor, repair risk, low licensee performance scores, decontamination and decommissioning costs, future electricity prices, and uranium market trends are discussed with respect to early closure
-
Morawo, Tolulope; Fadamiro, Henry
2014-12-01
Volatile organic compounds (VOCs) released by herbivore-damaged plants can guide parasitoids to their hosts. The quantity and quality of VOC blends emitted by plants may be affected by the duration of plant damage by herbivores, which could have potential ramifications on the recruitment of competing parasitoids. We used two parasitoid species, Microplitis croceipes and Cotesia marginiventris (Hymenoptera: Braconidae), to address the question of whether duration of plant damage affects parasitoid use of plant VOCs for host location. Both wasp species are larval endoparasitoids of Heliothis virescens (Lepidoptera: Noctuidae), an important pest of cotton. Attraction of the two parasitoid species to odors emitted by undamaged (UD), fresh (6 h infestation) damage (FD), and old (24 h infestation) damage (OD) cotton plants infested by H. virescens larvae was investigated using a headspace volatile collection system coupled with four-choice olfactometer bioassay. Both sexes of M. croceipes showed a preference for FD- and OD-plant odors over UD-plants. On the other hand, more C. marginiventris females were attracted to UD- and FD-plants than to OD-plants. GC/MS analyses showed qualitative and quantitative differences in the VOC profiles of UD, FD, and OD-plants, which may explain the observed preferences of the parasitoids. These results suggest a temporal partitioning in the recruitment of M. croceipes and C. marginiventris to H. virescens-damaged cotton, and may have potential implications for interspecific competition between the two parasitoid species.
-
Weed Competition and its Effects on Pwani Hybrid 1 Maize Grain Yields in Coastal Kenya
International Nuclear Information System (INIS)
Kamau, G.M.; Saha, H.M.
1999-01-01
Weed competition is a serious constraint to maize production in coastal Kenya. A trial to asses the effects of weed competition on performance of maize was planted at Regional Research Centre-Mtwapa and Msabaha Research Sub-centre-Malindi in 1992. Pwani hybrid 1 maize was used in the trials. Weeding was done at weekly intervals from germination up to the sixth week in an additive weed removal system and plots maintained weed free afterwards. A weedy and a weed free plot were used as checks. Data on plant counts plant heights, weed biomass, weed identification and maize grain yield at 15 % MC were all recorded. There was a significant difference between weed and weedy free plots for grain yield, plant height and weed biomass for both sites. A 53% maize grain yield reduction due to weed competition was recorded. A 3% grain yield reduction equivalent to 1.03 bags for every week's delay in weeding after the first to weeks was realised for both sites. There was a corresponding grain yield loss as delay in weeding increased
-
Competitiveness of nuclear energy - Key findings from an OECD study
International Nuclear Information System (INIS)
Bertel, Evelyne
2006-01-01
Economic competitiveness always has been a cornerstone in decision making for electricity generation options but the liberalization of energy markets has enhanced its importance. For private investors in de-regulated markets the economic attractiveness of a project is often 'the' driving factor. For plant owners and operators reducing costs is a key objective. The relative competitiveness of nuclear energy as compared with alternatives has been investigated in a recent OECD study which noted some evolution in the ranking of different options as compared with results published seven years ago. In particular the volatility of fossil fuel prices, notably natural gas for electricity generation, along with technical progress enhancing the reliability and availability factor of nuclear power plants have had a significant influence on comparative economic performance of base-load options. Furthermore, as governments implement progressively policies to address global climate change threat, the moves to internalize the costs of carbon emissions is increasing the competitiveness of low-carbon options such as renewable energy sources and nuclear power versus coal and to a lesser extent gas. (authors)
-
Gibson, A K; Hood, M E; Giraud, T
2012-06-01
Closely related species coexisting in sympatry provide critical insight into the mechanisms underlying speciation and the maintenance of genetic divergence. Selfing may promote reproductive isolation by facilitating local adaptation, causing reduced hybrid fitness in parental environments. Here, we propose a novel mechanism by which selfing can further impair interspecific gene flow: selfing may act to ensure that nonhybrid progeny systematically co-occur whenever hybrid genotypes are produced. Under a competition arena, the fitness differentials between nonhybrid and hybrid progeny are then magnified, preventing development of interspecific hybrids. We investigate whether this "sibling competition arena" can explain the coexistence in sympatry of closely related species of the plant fungal pathogens (Microbotryum) causing anther-smut disease. The probabilities of intrapromycelial mating (automixis), outcrossing, and sibling competition were manipulated in artificial inoculations to evaluate their contribution to reproductive isolation. We report that both intrapromycelial selfing and sibling competition significantly reduced rates of hybrid infection beyond that expected based solely upon selfing rates and noncompetitive fitness differentials between hybrid and nonhybrid progeny. Our results thus suggest that selfing and a sibling competition arena can combine to constitute a barrier to gene flow and diminish selection for additional barriers to gene flow in sympatry. © 2012 The Author(s). Evolution © 2012 The Society for the Study of Evolution.
-
Optimization of NPP performance and service life in a competitive electricity market
International Nuclear Information System (INIS)
Gueorguiev, B.; Spielgelberg - Planner, R.
2000-01-01
This paper discusses how the competitive electricity market has influenced nuclear power plant operations, with a focus on optimisation of NPP performance and plant service life, and how the IAEA programme has addressed some of this issues. The definitions of Plant Life, Operational Life, Design Life and Periodical Safety Reviews are developed in the paper in order to differentiate between the terms and to show the significance in terms of Plant Life Management
-
He, Wei-Ming; Feng, Yulong; Ridenour, Wendy M; Thelen, Giles C; Pollock, Jarrod L; Diaconu, Alecu; Callaway, Ragan M
2009-04-01
Recent studies suggest that the invasive success of Centaurea maculosa may be related to its stronger allelopathic effects on native North American species than on related European species, one component of the "novel weapons" hypothesis. Other research indicates that C. maculosa plants from the invasive range in North America have evolved to be larger and better competitors than conspecifics from the native range in Europe, a component of the "evolution of increased competitive ability" hypothesis. These hypotheses are not mutually exclusive, but this evidence sets the stage for comparing the relative importance of evolved competitive ability to inherent competitive traits. In a competition experiment with a large number of C. maculosa populations, we found no difference in the competitive effects of C. maculosa plants from North America and Europe on other species. However, both North American and European C. maculosa were much better competitors against plants native to North America than congeners native to Romania, collected in areas where C. maculosa is also native. These results are consistent with the novel weapons hypothesis. But, in a second experiment using just one population from North America and Europe, and where North American and European species were collected from a broader range of sites, competitive interactions were weaker overall, and the competitive effects of C. maculosa were slightly stronger against European species than against North American species. Also consistent with the novel weapons hypothesis, (+/-)-catechin had stronger effects on native North American species than on native European species in two experiments. Our results suggest that the regional composition of the plant communities being invaded by C. maculosa may be more important for invasive success than the evolution of increased size and competitive ability.
-
Atmospheric CO2 and O3 alter competition for soil nitrogen in developing forests
Donald R. Zak; Mark E. Kubiske; Kurt S. Pregitzer; Andrew J. Burton
2012-01-01
Plant growth responses to rising atmospheric CO2 and O3 vary among genotypes and between species, which could plausibly influence the strength of competitive interactions for soil N. Ascribable to the size-symmetric nature of belowground competition, we reasoned that differential growth responses to CO2...
-
Coal: Cornerstone of America`s competitive advantage in world markets
Energy Technology Data Exchange (ETDEWEB)
Mills, M.P. [Mills-McCarthy and Associates Inc., Chevy Chase, MD (United States)
1997-12-31
The United States` competitive position in world markets will be determined by many forces. Two of the fundamental factors are the increased use of new technologies, and the availability of low-cost electricity to operate those technologies. The US currently has an will likely continue to have market dominance in both these critical areas. Both of these factors are intimately related since the primary source of new technologies is electric in nature. And, because low-cost coal now dominates and will continue to dominate the electric supply system, and because the US has both an abundance of coal and the world`s largest fleet of coal-fired power plants, the US will have an expanding base of low-cost electricity that will secure its current competitive advantage for years to come. Electric technologies and, increasingly, computer-based technologies integrated with electric technologies are the primary sources of innovative advancement and economic growth. As a consequence, the growth in electricity, which has historically tracked GNP growth, is expected to continue. And, with the restructuring of the electric utility industry and the emergence of vigorous competition, prices are expected to decline as competition increases. The net effect of these forces will be to dramatically increase the use of electric technologies -- and those sources of electricity that can provide low-cost electricity. The data show that coal, the primary source of new los-cost electricity, will supply between one-half and three-fourths of all new electric supply through 2010, at prices of about 3{cents}/kWh, and can do so without new power plant construction. Since the use of coal is expected to rise by at least 200 to 250 million tons/year over the current consumption of 850 million tons, and could increase as much as 400 million tons/yr, some have raised concerns about the emissions impact from the power plants. This report also shows that the net effect of increased electric use, assuming
-
Tonneijck, A E G; Franzaring, J; Brouwer, G; Metselaar, K; Dueck, Th A
2004-09-01
Chronic effects of ozone on wet grassland species early in the growing season might be altered by interspecific competition. Individual plants of Holcus lanatus, Lychnis flos-cuculi, Molinia caerulea and Plantago lanceolata were grown in monocultures and in mixed cultures with Agrostis capillaris. Mesocosms were exposed to charcoal-filtered air plus 25 nl l(-1) ozone (CF+25), non-filtered air (NF), non-filtered air plus 25 nl l(-1) ozone (NF+25) and non-filtered air plus 50 nl l(-1) ozone (NF+50) early in the growing seasons of 2000 through 2002. Ozone-enhanced senescence and visible foliar injury were recorded on some of the target plants in the first year only. Ozone effects on biomass production were minimal and plant response to ozone did not differ between monocultures and mixed cultures. After three years, above-ground biomass of the plants in mixed culture compared to monocultures was three times greater for H. lanatus and two to four times smaller for the other species.
-
International Nuclear Information System (INIS)
Tonneijck, A.E.G.; Franzaring, J.; Brouwer, G.; Metselaar, K.; Dueck, Th.A.
2004-01-01
Chronic effects of ozone on wet grassland species early in the growing season might be altered by interspecific competition. Individual plants of Holcus lanatus, Lychnis flos-cuculi, Molinia caerulea and Plantago lanceolata were grown in monocultures and in mixed cultures with Agrostis capillaris. Mesocosms were exposed to charcoal-filtered air plus 25 nl l -1 ozone (CF + 25), non-filtered air (NF), non-filtered air plus 25 nl l -1 ozone (NF + 25) and non-filtered air plus 50 nl l -1 ozone (NF + 50) early in the growing seasons of 2000 through 2002. Ozone-enhanced senescence and visible foliar injury were recorded on some of the target plants in the first year only. Ozone effects on biomass production were minimal and plant response to ozone did not differ between monocultures and mixed cultures. After three years, above-ground biomass of the plants in mixed culture compared to monocultures was three times greater for H. lanatus and two to four times smaller for the other species
-
Floral advertisement and the competition for pollination services.
Fishman, Michael A; Hadany, Lilach
2015-06-01
Flowering plants are a major component of terrestrial ecosystems, and most of them depend on animal pollinators for reproduction. Thus, the mutualism between flowering plants and their pollinators is a keystone ecological relationship in both natural and agricultural ecosystems. Though plant-pollinator interactions have received considerable amount of attention, there are still many unanswered questions. In this paper, we use methods of evolutionary game theory to investigate the co-evolution of floral advertisement and pollinator preferences Our results indicate that competition for pollination services among plant species can in some cases lead to specialization of the pollinator population to a single plant species (oligolecty). However, collecting pollen from multiple plants - at least at the population level - is evolutionarily stable under a wider parameter range. Finally, we show that, in the presence of pollinators, plants that optimize their investment in attracting vs. rewarding visiting pollinators outcompete plants that do not. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
-
Cotin-Galvan, Laetitia; Pozzi, Adrien C; Schwob, Guillaume; Fournier, Pascale; Fernandez, Maria P; Herrera-Belaroussi, Aude
2016-01-01
Frankia Sp+ strains maintain their ability to sporulate in symbiosis with actinorhizal plants, producing abundant sporangia inside host plant cells, in contrast to Sp- strains, which are unable to perform in-planta sporulation. We herein examined the role of in-planta sporulation in Frankia infectivity and competitiveness for root infection. Fifteen strains belonging to different Sp+ and Sp- phylogenetic lineages were inoculated on seedlings of Alnus glutinosa (Ag) and A. incana (Ai). Strain competitiveness was investigated by performing Sp-/Sp+ co-inoculations. Plant inoculations were standardized using crushed nodules obtained under laboratory-controlled conditions (same plant species, age, and environmental factors). Specific oligonucleotide primers were developed to identify Frankia Sp+ and/or Sp- strains in the resulting nodules. Single inoculation experiments showed that (i) infectivity by Sp+ strains was significantly greater than that by Sp- strains, (ii) genetically divergent Sp+ strains exhibited different infective abilities, and (iii) Sp+ and Sp- strains showed different host preferences according to the origin (host species) of the inocula. Co-inoculations of Sp+ and Sp- strains revealed the greater competitiveness of Sp+ strains (98.3 to 100% of Sp+ nodules, with up to 15.6% nodules containing both Sp+ and Sp- strains). The results of the present study highlight differences in Sp+/Sp- strain ecological behaviors and provide new insights to strengthen the obligate symbiont hypothesis for Sp+ strains.
-
Plant life management optimized utilization of existing nuclear power plants
International Nuclear Information System (INIS)
Watzinger, H.; Erve, M.
1999-01-01
For safe, reliable and economical nuclear power generation it is of central importance to understand, analyze and manage aging-related phenomena and to apply this information in the systematic utilization and as-necessary extension of the service life of components and systems. An operator's overall approach to aging and plant life management which also improves performance characteristics can help to optimize plant operating economy. In view of the deregulation of the power generation industry with its increased competition, nuclear power plants must today also increasingly provide for or maintain a high level of plant availability and low power generating costs. This is a difficult challenge even for the newest, most modern plants, and as plants age they can only remain competitive if a plant operator adopts a strategic approach which takes into account the various aging-related effects on a plant-wide basis. The significance of aging and plant life management for nuclear power plants becomes apparent when looking at their age: By the year 2000 roughly fifty of the world's 434 commercial nuclear power plants will have been in operation for thirty years or more. According to the International Atomic Energy Agency, as many as 110 plants will have reached the thirty-year service mark by the year 2005. In many countries human society does not push the construction of new nuclear power plants and presumably will not change mind within the next ten years. New construction licenses cannot be expected so that for economical and ecological reasons existing plants have to be operated unchallengeably. On the other hand the deregulation of the power production market is asking just now for analysis of plant life time to operate the plants at a high technical and economical level until new nuclear power plants can be licensed and constructed. (author)
-
Gaya Shivega, W; Aldrich-Wolfe, Laura
2017-01-24
While the soil environment is generally acknowledged as playing a role in plant competition, the relative importance of soil resources and soil microbes in determining outcomes of competition between native and exotic plants has rarely been tested. Resilience of plant communities to invasion by exotic species may depend on the extent to which native and exotic plant performance are mediated by abiotic and biotic components of the soil. We used a greenhouse experiment to compare performance of two native prairie plant species and one exotic species, when grown in intraspecific competition and when each native was grown in interspecific competition with the exotic species, in the presence and absence of a native prairie soil community, and when nitrogen availability was elevated or was maintained at native prairie levels. We found that elevated nitrogen availability was beneficial to the exotic species and had no effect on or was detrimental to the native plant species, that the native microbial community was beneficial to the native plant species and either had no effect or was detrimental to the exotic species, and that intraspecific competition was stronger than interspecific competition for the exotic plant species and vice-versa for the natives. Our results demonstrate that soil nitrogen availability and the soil microbial community can mediate the strength of competition between native and exotic plant species. We found no evidence for native microbes enhancing the performance of the exotic plant species. Instead, loss of the native soil microbial community appears to reinforce the negative effects of elevated N on native plant communities and its benefits to exotic invasive species. Resilience of plant communities to invasion by exotic plant species is facilitated by the presence of an intact native soil microbial community and weakened by anthropogenic inputs of nitrogen. Published by Oxford University Press on behalf of the Annals of Botany Company.
-
Plant-plant interactions in the restoration of Mediterranean drylands
Valdecantos, Alejandro; Fuentes, David; Smanis, Athanasios
2014-05-01
Plant-plant interactions are complex and dependent of both local abiotic features of the ecosystem and biotic relationships with other plants and animals. The net result of these interactions may be positive, negative or neutral resulting in facilitation, competition or neutralism, respectively (role of phylogeny). It has been proposed that competition is stronger between those individuals that share functional traits than between unrelated ones. The relative interaction effect of one plant on a neighbour may change in relation to resource availability - especially water in drylands. In addition, plants develop above and belowground biomass with time increasing the level and, eventually, changing the intensity and/or the direction of the interaction. In the framework of the restoration of degraded drylands, many studies have focused on the positive (nurse) effects of adult trees, shrubs and even grasses on artificially planted seedlings by improving the microclimate or providing protection against herbivores, but little is known about the interactions between seedlings of different life traits planted together under natural field conditions. In 2010 we established planting plots in two contrasted sites under semiarid Mediterranean climate and introduced one year old seedlings in different combinations of three species, two shrubs (Olea europaea and Pistacia lentiscus) and one grass (Stipa tenacissima). Half of the planting holes in each site were implemented with low-cost ecotechnological inputs to increase water availability by forcing runoff production and promoting deep infiltration (small plastic fabric + dry well). This resulted in four levels of abiotic stress. Biotic interactions were assessed by monitoring seedling survival and growth for three years after planting. The Relative Interaction Index (RII) of S. tenacissima on O. europaea was almost flat and close to 0 along the stress gradient since the beginning of the study suggesting limited interaction
-
Modelling asymmetric growth in crowded plant communities
DEFF Research Database (Denmark)
Damgaard, Christian
2010-01-01
A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size......-asymmetric growth part, where growth is assumed to be proportional to a power function of the size of the individual, and a term that reduces the relative growth rate as a decreasing function of the individual plant size and the competitive interactions from other plants in the neighbourhood....
-
Experimental evolution of protozoan traits in response to interspecific competition.
terHorst, C P
2011-01-01
Decades of experiments have demonstrated the ecological effect of competition, but experimental evidence for competitive effects on trait evolution is rare. I measured the evolution of six protozoan traits in response to competitors from the inquiline community of pitcher plants. Replicate populations of Colpoda, a ciliated protozoan, were allowed to evolve in response to intra- and interspecific competition for 20 days (approximately 100 generations), before traits were measured in two common garden environments. Populations that evolved with interspecific competition had smaller cell sizes, produced fewer cysts and had higher population growth rates relative to populations grown in monoculture. The presence of interspecific competitors led to differential lineage sorting, most likely by increasing the strength of selection. These results are the first to demonstrate protozoan evolution in response to competition and may have implications for species coexistence in this system. © 2010 The Author. Journal of Evolutionary Biology © 2010 European Society For Evolutionary Biology.
-
Energy Technology Data Exchange (ETDEWEB)
T.B. Harrington; C.M. Dagley; M.B. Edwards.
2003-10-01
Although overstory trees limit the abundance and species richness of herbaceous vegetation in longleaf pine (Pinus palustris Mill.) plantations, the responsible mechanisms are poorly understood because of confounding among limiting factors. In fall 1998, research was initiated to determine the separate effects of above- and belowground competition and needlefall from overstory pines on understory plant performance. Three 13- to 15-yr-old plantations near Aiken, SC, were thinned to 0, 25, 50, or 100% of nonthinned basal area (19.5 m2 ha-1). Combinations of trenching (to eliminate root competition) and needlefall were applied to areas within each plot, and containerized seedlings of 14 perennial herbaceous species and longleaf pine were planted within each. Overstory crown closure ranged from 0 to 81%, and soil water and available nitrogen varied consistently with pine stocking, trenching, or their combination. Cover of planted species decreased an average of 16.5 and 14.1% as a result of above- and below-ground competition, respectively. Depending on species, needlefall effects were positive, negative, or negligible. Results indicate that understory restoration will be most successful when herbaceous species are established within canopy openings (0.1-0.2 ha) managed to minimize negative effects from above- and belowground competition and needlefall.
-
Insect herbivores drive real-time ecological and evolutionary change in plant populations.
Agrawal, Anurag A; Hastings, Amy P; Johnson, Marc T J; Maron, John L; Salminen, Juha-Pekka
2012-10-05
Insect herbivores are hypothesized to be major factors affecting the ecology and evolution of plants. We tested this prediction by suppressing insects in replicated field populations of a native plant, Oenothera biennis, which reduced seed predation, altered interspecific competitive dynamics, and resulted in rapid evolutionary divergence. Comparative genotyping and phenotyping of nearly 12,000 O. biennis individuals revealed that in plots protected from insects, resistance to herbivores declined through time owing to changes in flowering time and lower defensive ellagitannins in fruits, whereas plant competitive ability increased. This independent real-time evolution of plant resistance and competitive ability in the field resulted from the relaxation of direct selective effects of insects on plant defense and through indirect effects due to reduced herbivory on plant competitors.
-
The breakup of OPG : a suggestion for accelerating competition in generation in Ontario
International Nuclear Information System (INIS)
2003-01-01
Although wholesale and retail electricity markets in Ontario were opened to competition on May 1, 2002, the market cannot be said to be truly competitive because Ontario Power Generation (OPG) is still the dominant market participant controlling more than 25,000 MW of capacity, which gives it market power. The Association of Major Power Consumers in Ontario (AMPCO) has made specific proposals to the Macdonald Committee on how OPG could be restructured into several commercial generating companies, but it does not appear that OPG activities will be decontrolled in the next 2 or 3 years for the following 4 reasons: (1) the general state of the market for generation resource is poor following the collapse of Enron, (2) the government cannot afford to decontrol large quantities of OPG plants, (3) uncertainty over public policy regarding environmental regulations makes it difficult to decontrol fossil-fuelled plants, and (4) uncertainty over the return to service of Pickering A and Bruce A nuclear plants. Total OPG capacity is 25,855 MW including Pickering A. OPG's fossil-fuelled plants are mostly coal-fuelled and are under pressure from environmental groups to convert to gas. However, none of the plants are suitable for conversion. AMPCO strongly recommends that these plants should be operated in a commercial manner without unduly intrusive environmental regulation. Options for restructuring nuclear, fossil and large hydro plants were also presented along with a proposal to restructure OPG into multiple operating companies. It was concluded that the decontrol of OPG generation through the Market Power Mitigation Arrangement would result in a viable and liquid market, where prices are controlled by competitive forces. 2 refs., 2 tabs
-
Entry into the electricity market: Uncertainty, competition, and mothballing options
Energy Technology Data Exchange (ETDEWEB)
Takashima, Ryuta [Department of Nuclear Engineering and Management, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)], E-mail: takashima@n.t.u-tokyo.ac.jp; Goto, Makoto [Department of Industrial and Management Systems Engineering, Waseda University, 3-4-1 Okubo, Shinjyuku-ku, Tokyo 169-8555 (Japan); Kimura, Hiroshi; Madarame, Haruki [Nuclear Professional School, University of Tokyo, 2-22 Shirane, Shirakata, Tokai-mura, Naka-Gun, Ibaraki-ken 319-1188 (Japan)
2008-07-15
The present paper analyzes the entry strategies into the electricity market of two firms that have power plants under price uncertainty and competition. We consider the symmetric and asymmetric two firms, which have either a thermal power plant or a nuclear power plant. The differences between the thermal power plant and the nuclear power plant, such as the cost structure and operational flexibility are modeled. The threshold values of market entry are calculated for each firm with either the thermal power plant or the nuclear power plant as the leader or the follower. We show the dependence of cost structures on entry thresholds of the leader and the follower into the electricity market. For various market and cost conditions, the diagrams of the leader are also shown.
-
Entry into the electricity market: Uncertainty, competition, and mothballing options
International Nuclear Information System (INIS)
Takashima, Ryuta; Goto, Makoto; Kimura, Hiroshi; Madarame, Haruki
2008-01-01
The present paper analyzes the entry strategies into the electricity market of two firms that have power plants under price uncertainty and competition. We consider the symmetric and asymmetric two firms, which have either a thermal power plant or a nuclear power plant. The differences between the thermal power plant and the nuclear power plant, such as the cost structure and operational flexibility are modeled. The threshold values of market entry are calculated for each firm with either the thermal power plant or the nuclear power plant as the leader or the follower. We show the dependence of cost structures on entry thresholds of the leader and the follower into the electricity market. For various market and cost conditions, the diagrams of the leader are also shown
-
A review of the potential for competitive cereal cultivars as a tool in integrated weed management.
Andrew, I K S; Storkey, J; Sparkes, D L
2015-06-01
Competitive crop cultivars offer a potentially cheap option to include in integrated weed management strategies (IWM). Although cultivars with high competitive potential have been identified amongst cereal crops, competitiveness has not traditionally been considered a priority for breeding or farmer cultivar choice. The challenge of managing herbicide-resistant weed populations has, however, renewed interest in cultural weed control options, including competitive cultivars. We evaluated the current understanding of the traits that explain variability in competitive ability between cultivars, the relationship between suppression of weed neighbours and tolerance of their presence and the existence of trade-offs between competitive ability and yield in weed-free scenarios. A large number of relationships between competitive ability and plant traits have been reported in the literature, including plant height, speed of development, canopy architecture and partitioning of resources. There is uncertainty over the relationship between suppressive ability and tolerance, although tolerance is a less stable trait over seasons and locations. To realise the potential of competitive crop cultivars as a tool in IWM, a quick and simple-to-use protocol for assessing the competitive potential of new cultivars is required; it is likely that this will not be based on a single trait, but will need to capture the combined effect of multiple traits. A way needs to be found to make this information accessible to farmers, so that competitive cultivars can be better integrated into their weed control programmes.
-
[Effect of habitat and interspecific competition on Apis cerana cerana colony distribution].
Yu, Linsheng; Han, Shengming
2003-04-01
Habitat change and interspecific competition were the main factors affecting, Apis cerana cerana colony distribution among Wannan and Wanxi Dabie mountainous areas, Jianghuai area and Huaibei plain. Wannan and Wanxi Dabie mountainous areas were the ideal places for Apis cerana cerana' habitation and propogation, in which, there were integrated natural vegetation, fine ecological condition, abundant nectariferous plants, and Apis cerana cerana had large colony size, wide distribution, high density, no disturbances of natural mating, and was dominant interspecific competition. In Jianghuai area and Huaibei plain, there were small covering of natural vegetation, different degree of degradation of ecological balance, few kinds of nectariferous plants with almost the same blooming periods, natural mating perturbed by Apis mellifera ligustica for Apis cerana cerana, and which was inferior in interspecific competition, colony size sharply decreased, distribution area reduced, and density cut down to a great extent. In Huaibei plain, the negative factors were more conspicuous.
-
Campitelli, Brandon E; Des Marais, David L; Juenger, Thomas E
2016-04-01
The presence of substantial genetic variation for water-use efficiency (WUE) suggests that natural selection plays a role in maintaining alleles that affect WUE. Soil water deficit can reduce plant survival, and is likely to impose selection to increase WUE, whereas competition for resources may select for decreased WUE to ensure water acquisition. We tested the fitness consequences of natural allelic variation in a single gene (MPK12) that influences WUE in Arabidopsis, using transgenic lines contrasting in MPK12 alleles, under four treatments; drought/competition, drought/no competition, well-watered/competition, well-watered/no competition. Results revealed an allele × environment interaction: Low WUE plants performed better in competition, resulting from increased resource consumption. Contrastingly, high WUE individuals performed better in no competition, irrespective of water availability, presumably from enhanced water conservation and nitrogen acquisition. Our findings suggest that selection can influence MPK12 evolution, and represents the first assessment of plant fitness resulting from natural allelic variation at a single locus affecting WUE. © 2016 John Wiley & Sons Ltd/CNRS.
-
Directory of Open Access Journals (Sweden)
M Fuladvand
2015-09-01
Full Text Available In order to evaluation of plant density, rate and method of nitrogen fertilizer split application on quality characteristics and nitrogen use efficiency of safflower (Sofeh variety under weed competition a field experiment was carried out in field research Yasouj University in 2013. This experiment was a factorial based on randomized complete block design with three replications. First factor was a two levels plant density (20 and 40 plants m-2 and second factor was nitrogen rate application on nine levels. That included; non nitrogen application and 75 and 150 kgN ha-1 nitrogen application that both used with four split method. Split methods were included; S1 (%50 in pre planting stage - %50 in stem elongation stage, S2 (%25 in pre planting stage - %75 in stem elongation stage, S3 (%25 in pre planting stage - %50 in stem elongation stage -%25 in flowering stage and S4 (%25 in pre planting stage - %25 in stem elongation stage - %25 in flowering stage. Also in this experiment, weed did not control. Results showed that whit increasing crop density, oil yield and protein grain yield increased by 20 percent and nitrogen utilization efficiency increased by 10 percent. The highest oil yield (50.25 g m-2 was obtained from 75 kg ha-1 nitrogen with three-stage split application (S4. Finally, results showed that increasing nitrogen fertilizer application decreased nitrogen utilization efficiency but three-stage split method application increased this trait.
-
Papaya Development Model As A Competitive Local Superior Commodity
Directory of Open Access Journals (Sweden)
Reny Sukmawani
2014-12-01
Full Text Available The aim of this research is to study the comparative advantage and papaya competitive and to design its development model by using the approach of local base agriculture development. This research uses survey method. The resulting research shows that papaya is a base commodity that has comparative advantage and competitive. The development papaya in the district of Sukabumi is quite good bases on eight superior creations. But in order to be the main sector in economic development and has a competition, the development of papaya must concern to its influence factors. In supporting papaya development as a competitive local superior commodity, it needs to be done some efforts are as follows: (1 increase a skillful worker; (2 improve business management; (3 increase papaya productivity by using technology and study papaya planted technology in specific local superior commodity; (4 develop the involvement of the business relation; (5 provide market information and information technology network; and (6 improve infrastructures.
-
EDITORIAL: Physics competitions Physics competitions
Jordens, H.; Mathelitsch, L.
2009-11-01
1. Physics competitions: aims and realizations One aim of physics competitions is to increase the interest of young students, primarily at upper secondary level, to physics and natural sciences in general. A competition has motivational aspects known usually from sports events or games—comparing one's own ability with others, of course with the desire to be better and to win. If competitions reach nationwide and even international levels, additional stimulation is created. Competitions provide greatest attraction to possible winners, to the group of gifted people in a particular field. This implies that science contests are excellent tools for the promotion of talented students. Traditional teaching has been shown to have problems in supporting this group of students. Very often teachers are overstretched with the demands of teaching both low- and high-level students. Extracurricular activities are therefore a good chance to relieve the teacher, and to give talented students the opportunity for appropriate training and challenge. The competitions, however, have a broader impact and address more young people than one might guess from the statements above. Training courses and selection at school level give a larger group of students extra and, to some extent, complimentary education in physics. The degree of complexity of the tasks corresponds very often to the standards of the next level of education in the school system. Interestingly, many physics competitions have their origin in countries beyond the former Iron Curtain. They started as regional and national tournaments, were joined by neighbouring countries and have grown, in some cases, to events with participants from more than 80 countries. Although the features mentioned above are common to the different competitions, there are distinct differences between them [1]. The International Physics Olympiad (IPhO) is the oldest international physics competition for students at upper secondary level [2]. It dates
-
Competition between two grass species with and without grazing over a productivity gradient
Kuijper, D.P.J.; Dubbeld, J.; Bakker, J.P.
2005-01-01
Soil nutrient-level and herbivory are predicted to have opposing effects on the allocation pattern of the competitive dominant plant species. Lower stem and higher leaf allocation are favoured when plants are grazed, whereas a higher stem allocation is favoured at high nutrient levels. Grazing by
-
COMPETITIVENESS AND COMPETITIVE ORIENTATIONS: EVALUATION OF STUDENTS
Directory of Open Access Journals (Sweden)
G. Z. Efimova
2017-01-01
Full Text Available Introduction. Education of a competitive student is a strategically significant problem of the system of higher education in modern social and economic conditions. Personal competitiveness and competitive orientations – priority quality of future expert for successful future professional experience.The aim of the present research is to study factors of competitive orientations formation and criteria for evaluation of competitiveness of student’s youth in the Russian society.Methodology and research methods. Results of theoretical researches of Russian and foreign researchers are generalized; secondary analysis of data based on results of sociological researches and analysis of official statistical data are carried out. The results of the sociological survey undertaken in 2017 on the basis of statistical methods were processed and studied by the instrumentality of IBM SPSS Statistics 23 program; 1196 students of institutions of higher and secondary vocational education of the Tyumen region took part.Results and scientific novelty. It is stated that senior students feel themselves more competitive. It is revealed that a quarter of students who took part in the survey, generally men, count themselves competitive. A continuous distance of goal-setting is recorded among these respondents; in every third case they have plans of professional growth for five and more years that allows them to build attractive competitive strategy.The level of the competitiveness is directly connected with such indicators as “social stratum”, “overall life satisfaction”, “self-esteem of health”, “tendency to lead a healthy lifestyle” and “the level of trust in the surrounding people”. Mostly the students oriented on competition look into the future with confidence and optimism.Respondents focused on the competitiveness were more tend to demonstrate their abilities and cause admiration, have a creative approach towards work, be ready for surprises
-
Economic efficency and competitive position of nuclear energy today
International Nuclear Information System (INIS)
Schmitt, D.
1988-01-01
In spite of the relaxation making itself felt at the moment on the world energy markets, the competitive position of nuclear power from either existing or shortly to be connected power plants remains safe. Any attempt at doing without this extraordinarily convenient vehicle of power generation would mean to severely force up costs and expenses. The competitive position of existing nuclear power plants is assumed to remain untouched through the coming decade. In spite of the presently very low world market prices imported coal is especially affected by, even abstract economic analyses show nuclear energy to come out superior to all other alternatives providing for the electric power supply of the Federal Republic of Germany. Once the over-capacity is reduced and under control, a longer-term superior competitive position of nuclear power, however, presupposes a rise in prices full level with those of the neighbor countries. At any rate and for the time being, the divergence of electric power from imported coal prices which was even obvious in the mean load range has diminished. The superior position of nuclear power in the base load range can be maintained through avoiding further rises in operating costs by gradual rationalization and standardization. (orig./HP) [de
-
Blanchard, Megan L; Barney, Jacob N; Averill, Kristine M; Mohler, Charles L; Ditommaso, Antonio
2010-02-01
Determining which traits may allow some introduced plant species to become invasive in their new environment continues to be a key question in invasion biology. Vincetoxicum rossicum is an invasive, perennial vine colonizing natural and seminatural habitats primarily in the northeastern United States and southeastern Canada. More than half its seeds exhibit polyembryony, a relatively uncommon condition in which a single seed produces multiple seedlings. For evaluating the potential consequences of polyembryony on invasiveness, V. rossicum plants derived from seeds of three embryonic classes-singlets, doublets, and triplets (one, two, and three seedlings per seed, respectively)-were paired in all combinations intraspecifically and with the co-occurring native herbs Solidago canadensis and Asclepias syriaca in a greenhouse study. Vincetoxicum rossicum biomass was 25-55% greater and follicle production 55-100% greater under intraspecific competition compared with interspecific competition. However, within a competitive environment, follicle production varied little. Regardless of competitive environment, V. rossicum originating from seeds with a greater number of embryos typically performed no better than plants arising from seed with fewer embryos (singlets = doublets = triplets)-except intraspecifically where doublets outperformed singlets, and with S. canadensis where triplets outperformed singlets. Our findings suggest that overall performance and fitness of V. rossicum is higher in monocultures than in mixed stands and that its ability to invade new habitats may not be attributable to the production of polyembryonic seeds.
-
Energy Technology Data Exchange (ETDEWEB)
NONE
2011-07-01
The proceedings on the VGB conference ''power plants in competition 2011'' includes the following contributions: status of European energy policy; market and climate protection; setting up new conventional capacity in Europe and EU regulation; perspectives of power generation in Germany and Europe; market for power generation - challenges and chances for suppliers; development of a European ''network code'' for integration of power plants; impact of ''EU network code'' for design and operation of power plants; outcome of investigation of grid/generation; impact of intermitting generation on power system stability; consequences of low-load operation for coal fired power plants; pro quality - an approach for project management; Sumitomos R and D activities for advanced USC boilers; V and M innovative contribution to the challenges of present and future conventional power plants; steam side oxidation at austenitic boiler tubes; OL3 project - a multicultural challenge; knowledge management - preservation and maintenance of implicit knowledge within a company; competition about green investments - the European targets for renewables; retrofitting of CEZ power plants (coal and gas); power sector skill - addressing the challenges; requirements on structural maintenance in power plants; usage of corrugated tubes in heat exchangers; technical plant documentation; technologies for off-shore wind turbines; solar thermal plants; renewable energy from biomass and integration into the grid; environmentally friendly future power generation with fossil fuels; storage technologies; large-scale underground energy storage; assessment of risk - an insurance company view; human resources as multiplier for a company's value; post-combustion capture pilot plant experiences; CCS strategy of Vattenfall; optimizing plant process management; Enel activities on carbon capture and sequestration; bachelor studies on power plant
-
Plant neighbour identity matters to belowground interactions under controlled conditions.
Armas, Cristina; Pugnaire, Francisco Ignacio
2011-01-01
Root competition is an almost ubiquitous feature of plant communities with profound effects on their structure and composition. Far beyond the traditional view that plants interact mainly through resource depletion (exploitation competition), roots are known to be able to interact with their environment using a large variety of mechanisms that may inhibit or enhance access of other roots to the resource or affect plant growth (contest interactions). However, an extensive analysis on how these contest root interactions may affect species interaction abilities is almost lacking. In a common garden experiment with ten perennial plant species we forced pairs of plants of the same or different species to overlap their roots and analyzed how belowground contest interactions affected plant performance, biomass allocation patterns, and competitive abilities under abundant resource supply. Our results showed that net interaction outcome ranged from negative to positive, affecting total plant mass and allocation patterns. A species could be a strong competitor against one species, weaker against another one, and even facilitator to a third species. This leads to sets of species where competitive hierarchies may be clear but also to groups where such rankings are not, suggesting that intransitive root interactions may be crucial for species coexistence. The outcome of belowground contest interactions is strongly dependent on neighbours' identity. In natural plant communities this conditional outcome may hypothetically help species to interact in non-hierarchical and intransitive networks, which in turn might promote coexistence.
-
Energy Technology Data Exchange (ETDEWEB)
Tonneijck, A.E.G.; Franzaring, J.; Brouwer, G.; Metselaar, K.; Dueck, Th.A
2004-09-01
Chronic effects of ozone on wet grassland species early in the growing season might be altered by interspecific competition. Individual plants of Holcus lanatus, Lychnis flos-cuculi, Molinia caerulea and Plantago lanceolata were grown in monocultures and in mixed cultures with Agrostis capillaris. Mesocosms were exposed to charcoal-filtered air plus 25 nl l{sup -1} ozone (CF + 25), non-filtered air (NF), non-filtered air plus 25 nl l{sup -1} ozone (NF + 25) and non-filtered air plus 50 nl l{sup -1} ozone (NF + 50) early in the growing seasons of 2000 through 2002. Ozone-enhanced senescence and visible foliar injury were recorded on some of the target plants in the first year only. Ozone effects on biomass production were minimal and plant response to ozone did not differ between monocultures and mixed cultures. After three years, above-ground biomass of the plants in mixed culture compared to monocultures was three times greater for H. lanatus and two to four times smaller for the other species.
-
The foundations of plant intelligence.
Trewavas, Anthony
2017-06-06
Intelligence is defined for wild plants and its role in fitness identified. Intelligent behaviour exhibited by single cells and systems similarity between the interactome and connectome indicates neural systems are not necessary for intelligent capabilities. Plants sense and respond to many environmental signals that are assessed to competitively optimize acquisition of patchily distributed resources. Situations of choice engender motivational states in goal-directed plant behaviour; consequent intelligent decisions enable efficient gain of energy over expenditure. Comparison of swarm intelligence and plant behaviour indicates the origins of plant intelligence lie in complex communication and is exemplified by cambial control of branch function. Error correction in behaviours indicates both awareness and intention as does the ability to count to five. Volatile organic compounds are used as signals in numerous plant interactions. Being complex in composition and often species and individual specific, they may represent the plant language and account for self and alien recognition between individual plants. Game theory has been used to understand competitive and cooperative interactions between plants and microbes. Some unexpected cooperative behaviour between individuals and potential aliens has emerged. Behaviour profiting from experience, another simple definition of intelligence, requires both learning and memory and is indicated in the priming of herbivory, disease and abiotic stresses.
-
Competition or coordination in hospital markets with unionised labour.
Brekke, Kurt R
2004-03-01
This paper study labour market responses to hospital mergers. The market consists of two hospitals providing horizontally and vertically differentiated services. Hospitals compete either in price and quality or just in quality (non-price competition). To provide medical care, hospitals employ health care workers (e.g., physicians, nurses). The workers collectively bargain wages either at a central level, firm level or plant level. Anticipating wage responses, hospitals decide whether or not to merge. The main finding is that the bargaining structure, the nature of competition and the patient copayment rate have a crucial impact on the profitability of hospital mergers.
-
Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage.
Dodd, Antony N; Salathia, Neeraj; Hall, Anthony; Kévei, Eva; Tóth, Réka; Nagy, Ferenc; Hibberd, Julian M; Millar, Andrew J; Webb, Alex A R
2005-07-22
Circadian clocks are believed to confer an advantage to plants, but the nature of that advantage has been unknown. We show that a substantial photosynthetic advantage is conferred by correct matching of the circadian clock period with that of the external light-dark cycle. In wild type and in long- and short-circadian period mutants of Arabidopsis thaliana, plants with a clock period matched to the environment contain more chlorophyll, fix more carbon, grow faster, and survive better than plants with circadian periods differing from their environment. This explains why plants gain advantage from circadian control.
-
Competition within the energy sector and State regulation
International Nuclear Information System (INIS)
Larsen, A.; Jess Olsen, O.
1995-10-01
It is presumed that energy markets will be liberalized. Questions discussed are how the Danish electricity and gas sectors are to be re-regulated in order to ensure that this goal is reached in the most satisfactory manner (cheaper energy supply under competitive conditions) and whether there will be a conflict between the goal of liberalization and the environmental goals of clean technology and energy conservation. It is suggested that a compulsory splitting up of the two regional power associations in Denmark should not be necessary. Transmission and distribution must continue to be regulated as these are natural monopolies not compatible with competition. District heating will still be a monopoly and its prices must be closely regulated to prevent soaring. The opening up of the European gas market to competition will threaten Danish energy utilities. The increasing compulsory use of natural gas in cogeneration plants to politically determined high prices is not sustainable under competitive conditions. Energy saving activities should not be affected. Energy surcharges are attractive measures on a liberalized market. The regulation of competition ought to be incorporated explicitly as a restriction in the Ministry of Energy's energy policy regulation. Energy utilities could be excluded from participation in price setting. International regulation of competition will demand a clarification of the separation of regulatory competence between the member states and the European Commission. It will also be necessary to adjust the Danish regulation of the electricity sector to the future Scandinavian system. (AB) 77 refs
-
Competitive balance in national European soccer competitions
Haan, M.A.; Koning, R.H.; van Witteloostuijn, A.; Albert, Jim; Koning, Ruud H.
2007-01-01
According to popular belief, competitive balance in national soccer competitions in Europe has decreased due to the Bosman ruling and the introduction of the Champions League. We test this hypothesis using data from 7 national competitions, for a host of indicators. We find some evidence for
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Cattenom comprises 4 production units of 1300 MW each (5200 MW as a whole). The facility generated 34 billion kWh in 2009, i.e. 8% of the French national power generation. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Chinon comprises 4 production units of 900 MW each (3600 MW as a whole). The facility generated 19.03 billion kWh in 2009, i.e. 4.8% of the French national power generation. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Fessenheim comprises two production units of 900 MW each (1800 MW as a whole). The facility generated 8.7 billion kWh in 2009, i.e. 70% of the energy consumed in the Alsace region. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
Directory of Open Access Journals (Sweden)
alireza barkhi
2009-06-01
Full Text Available An experiment was conducted in 2002-2003 using split-split plot arrangement based on Rondomised Compelete Block Design with three replications at Feiz Abad Agricultural Research Station of Qazvin, in order to study of planting patterns and corn densitis effect in competition with redroot pigweed. Main plots inclouded two planting pattern of corn (P1: single row and P2: double row, sub plots inclouded two corn densities (D1:7 and D2:10 plant/m2 and sub sub plots inclouded 4 weed densities (C1:0, C2:2, C3:6, C4:12 plant/m2. Sampling conducted in 2-weekly intervals and growth indices evaluated. Results indicated that with increasing of weed density CGR, TDW, LAI, number of seeds in row, grain and ear yield decreased but plant height increased. Also LAI, CGR, TDW, number of weed seed and seed,s weight of weed increased. By increasing in corn density LAI, CGR, TDW, ear and grain yield increased, but length and diameter of ear and number of seeds in row decreased. Also LAI and CGR of weed increased, but TDW was decreased. In double row planting pattern just CGR, LAI, TDW of corn were higher significantly than single row planting pattern. But single row planting of weed caused higher LAI, NAR, RGR, CGR and TDW of weed in comparison with double row planting pattern. In 2-way interaction, double row planting pattern and zero densities and 2 weeds/m2 had highest grain yield respectively. There were no significant differences for 3-way interactions but double row planting pattern 10 plant density of corn/m2 zero weed/ m2 had highest grain yield.
-
Ren, Haiyan; Gao, Tao; Hu, Jian; Yang, Gaowen
2017-01-01
Understanding the factors that alter competitive interactions and coexistence between plants is a key issue in ecological research. A pot experiment was conducted to test the effects of root interaction and arbuscular mycorrhizal fungi (AMF) inoculation on the interspecies competition between Trifolium repens and Lolium perenne under different proportions of mixed sowing by the combination treatment of two levels of AMF inoculation (inoculation and non-inoculation) and two levels of root interaction (root interaction and non-root interaction). Overall, the aboveground and belowground biomass of T. repens and L. perenne were not altered by AMF inoculation across planting ratios, probably because the fertile soil reduced the positive effect of AMF on plant growth. Both inter- and intraspecies root interaction significantly decreased the aboveground biomass of T. repens , but tended to increase the aboveground biomass of L. perenne across planting ratios, and thus peaked at the 4:4 polyculture. These results showed that T. repens competed poorly with L. perenne because of inter and intraspecies root interaction. Our results indicate that interspecies root interaction regulates the competitive ability of grass L. perenne and legume T. repens in mixtures and further makes great contribution for overyielding. Furthermore, AMF may not be involved in plant-plant interaction in fertile condition.
-
Water management can reinforce plant competition in salt-affected semi-arid wetlands
Coletti, Janaine Z.; Vogwill, Ryan; Hipsey, Matthew R.
2017-09-01
The diversity of vegetation in semi-arid, ephemeral wetlands is determined by niche availability and species competition, both of which are influenced by changes in water availability and salinity. Here, we hypothesise that ignoring physiological differences and competition between species when managing wetland hydrologic regimes can lead to a decrease in vegetation diversity, even when the overall wetland carrying capacity is improved. Using an ecohydrological model capable of resolving water-vegetation-salt feedbacks, we investigate why water surface and groundwater management interventions to combat vegetation decline have been more beneficial to Casuarina obesa than to Melaleuca strobophylla, the co-dominant tree species in Lake Toolibin, a salt-affected wetland in Western Australia. The simulations reveal that in trying to reduce the negative effect of salinity, the management interventions have created an environment favouring C. obesa by intensifying the climate-induced trend that the wetland has been experiencing of lower water availability and higher root-zone salinity. By testing alternative scenarios, we show that interventions that improve M. strobophylla biomass are possible by promoting hydrologic conditions that are less specific to the niche requirements of C. obesa. Modelling uncertainties were explored via a Markov Chain Monte Carlo (MCMC) algorithm. Overall, the study demonstrates the importance of including species differentiation and competition in ecohydrological models that form the basis for wetland management.
-
Extension plant pathology: strengthening resources to continue serving the public interest.
Everts, K L; Osborne, L; Gevens, A J; Vasquez, S J; Gugino, B K; Ivors, K; Harmon, C
2012-07-01
Extension plant pathologists deliver science-based information that protects the economic value of agricultural and horticultural crops in the United States by educating growers and the general public about plant diseases. Extension plant pathologists diagnose plant diseases and disorders, provide advice, and conduct applied research on local and regional plant disease problems. During the last century, extension plant pathology programs have adjusted to demographic shifts in the U.S. population and to changes in program funding. Extension programs are now more collaborative and more specialized in response to a highly educated clientele. Changes in federal and state budgets and policies have also reduced funding and shifted the source of funding of extension plant pathologists from formula funds towards specialized competitive grants. These competitive grants often favor national over local and regional plant disease issues and typically require a long lead time to secure funding. These changes coupled with a reduction in personnel pose a threat to extension plant pathology programs. Increasing demand for high-quality, unbiased information and the continued reduction in local, state, and federal funds is unsustainable and, if not abated, will lead to a delay in response to emerging diseases, reduce crop yields, increase economic losses, and place U.S. agriculture at a global competitive disadvantage. In this letter, we outline four recommendations to strengthen the role and resources of extension plant pathologists as they guide our nation's food, feed, fuel, fiber, and ornamental producers into an era of increasing technological complexity and global competitiveness.
-
Competitiveness basis of integrated PWR technology
International Nuclear Information System (INIS)
Florido, Pablo C.; Bergallo, Juan E.
1999-01-01
The present nuclear power market is dominated by LWR, with a minor fraction of CANDU contribution due to its advantages in small and medium electric grid. Nowadays the demand for nuclear reactors is concentrated in Asia and this situation will probably not change in the short and medium term, even under the financial crisis. The Asian market needs large plants, and feedback regarding demand and products has been done (AP 600 and Sbwr) in studies of passive systems to higher power range. Present active nuclear power programs take place in countries with high GNP growth and related electricity energy demand far from expectancies in the '80. Four of these countries were in the list of the top 10 most dynamical nations. Traditionally, nuclear countries have large economies and electric grids or strong national nuclear commitment. However, in the near future the demand of nuclear reactors seems to move towards faster growing economies and countries, with new electrical grids. From the point of view of the competitiveness, higher power nuclear plants are seriously questioned in this new market. The International Atomic Energy Agency has promoted studies in the field of small nuclear power plants (around 300 M We) for a long time. These designs have never reached commercial level in industrialized countries. One reason has been that the reactor technology naturally moves towards the best economy, i.e. the greater power. The second reason has been that the nuclear designers were always in countries with large electric systems. Consequently the utilities never have been attracted by prototypes of small reactors. The only option to develop a competitive medium nuclear reactors is to develop a design with different scale economy, like the scale economy of CCGT. If LWR technology is used, the design could be the best alternative for the utilities, because the availability of present LWR is one of the main advantages as a proved power source. The most promising type of LWR with
-
Reflections on Competition, Competition Regulation and the Current Crises
DEFF Research Database (Denmark)
Buch-Hansen, Hubert; Wigger, Angela
2013-01-01
competition came to enjoy such an exalted status in Europe and then challenges conventional wisdom by bringing into focus the downsides of competition. It argues that excessive competition and neoliberal competition regulation have contributed to intensify the economic, political, social and environmental...
-
Competition between two wetland macrophytes under different levels of sediment saturation
Directory of Open Access Journals (Sweden)
Feng Li
2015-02-01
Full Text Available Plant-plant interactions have been widely studied under various environmental conditions. However, in wetland ecosystems how plant interactions change in response to variation in sediment saturation remains largely unclear, even though different levels of sediment saturation play important roles in determining plant growth performance in wetland ecosystems. To this end, a competition experiment with two typical wetland species, Carex brevicuspis (neighbor plant and Polygonum hydropiper (target plant, was conducted in a target-neighbor design. Two water levels (0 cm and -40 cm water levels representing waterlogged and drained sediments, respectively and three neighbor plant densities (0 plants m-2, 400 plants m-2, and 1600 plants m-2 were tested in a factorial design. Biomass accumulation of P. hydropiper decreased along with enhanced C. brevicuspis density in the waterlogged treatment. However, in the drained treatment, biomass accumulation did not change under two C. brevicuspis densities. Above-ground relative neighbor effect index (ARNE and relative neighbor effect index (RNE of C. brevicuspis on P. hydropiper increased along with enhanced C. brevicuspis density only under waterlogged conditions. The below-ground relative neighbor effect index (BRNE was not affected at the different water level and density treatments. The below-ground mass fraction of P. hydropiper was much higher in the waterlogged treatment than it was in the drained one, especially with no C. brevicuspis treatment. However, the leaf mass fraction displayed the opposite pattern. The longest root length of P. hydropiper was much shorter under waterlogged treatment than under the drained treatment. These results suggest that the competition intensity of C. brevicuspis to P. hydropiper increased along with increasing C. brevicuspis density only under waterlogged conditions. Moreover, this study also confirms that P. hydropiper can acclimate to water stress mainly through
-
Competition and power pooling in the electricity industry
International Nuclear Information System (INIS)
Jasinski, P.; Yarrow, G.; Fusaro, P.
1995-01-01
Two contributions to the debate on power pooling and competition in the electricity supply industry are presented. In the first, the situation in England and Wales where power pooling was introduced shortly before privatization is analysed. Pooling has existed for many years in the USA but as an inter-generator arrangement designed to optimize production and costs. The British system sought in addition to establish a spot market in which bulk buyers as well as bulk suppliers could participate. There are however obvious weaknesses in the pool as a competitive market and it is argued that a combination of pooling arrangements and longer-term bilateral supply contracts are more likely to offer the prospect of workably competitive and efficient outcomes. The second contribution discusses how competitive markets will evolve in the USA under the new regime of less onerous regulation heralded by the Energy Policy Act if 1992 and the emergence of electricity trading markets which followed. In particular, the proposal by the California Public Utility commission favouring a mandatory Poolco is examined. Poolco would operate the transmission grid and dispatch generating plants while the utilities would retain ownership of transmission facilities and be required to supply the pool. This is seen as representing only partial deregulation and not to be consistent with moves to further competition and encourage free markets. (U.K.)
-
Martinez-Garcia, Ricardo; Calabrese, Justin M.; Hernandez-Garcia, Emilio; Lopez, Cristobal
2014-05-01
Regular patterns and spatial organization of vegetation have been observed in many arid and semiarid ecosystems worldwide, covering a diverse range of plant taxa and soil types. A key common ingredient in these systems is that plant growth is severely limited by water availability, and thus plants likely compete strongly for water. The study of such patterns is especially interesting because their features may reveal much about the underlying physical and biological processes that generated them in addition to giving information on the characteristics of the ecosystem. It is possible, for instance, to infer their resilience against anthropogenic disturbances or climatic changes that could cause abrupt shifts in the system and lead it to a desert state. Therefore much research has focused on identifying the underlying mechanisms that can produce spatial patterning in water-limited systems (Klausmeier, 1999). They are believed to arise from the interplay between long-range competition and facilitation processes acting at smaller distances (Borgogno et al., 2009). This combination of mechanisms is justified by arguing that water percolates more readily through the soil in vegetated areas (short range), and that plants compete for water resources over greater distances via long lateral roots (long range). However, recent studies have shown that even in the limit of local facilitation patterns may still appear (Martinez-Garcia et al., 2013). In this work (Martinez-Garcia et al., 2013b), we show that, under rather general conditions, long-range competition alone is the minimal ingredient to shape gapped and stripped vegetation patterns typical of models that also account for facilitation in addition to competition. To this end we propose a simple, general model for the dynamics of vegetation, which includes only long-range competition between plants. Competition is introduced through a nonlocal term, where the kernel function quantifies the intensity of the interaction
-
Jankju-Borzelabad, Mohammad; Griffiths, Howard
2006-07-01
In arid environments, episodically-pulsed resources are important components of annual water and nutrient supply for plants. This study set out to test whether seedlings have an increased capacity for using pulsed resources, which might then improve establishment when in competition with older individuals. A second aim was to determine whether there is a trade-off in competitive strategies when resources are supplied continuously at low concentrations, or as pulses with pronounced inter-pulse periods. A glasshouse experiment used a target-neighbour design of size-asymmetric competition, with juveniles of Panicum antidotale (blue panicgrass) introduced into contrasting densities of adult plants. Stable isotopes of nitrogen were used for measuring plant resource uptake from pulses, and tolerance to inter-pulse conditions was assessed as the mean residence time (MRT) of nitrogen. A higher root/shoot ratio and finer root system enhanced the capacity of juveniles to use resources when pulsed, rather than when continuously supplied. Higher resource uptake during pulses improved the establishment of juvenile Panicum in mixed cultures with older individuals. However, a trade-off was observed in plant strategies, with juveniles showing a lower MRT for nitrogen, which suggested reduced tolerance to resource deficit during inter-pulse periods. Under field conditions, higher utilization of pulsed resources would lead to the improved seedling establishment of Panicum adjacent to "nurse" plants, whereas mature plants with well-developed roots, exploiting a greater soil volume, maintain more constant resource uptake and retention during inter-pulse periods.
-
Environmental structure and competitive scoring advantages in team competitions
Merritt, Sears; Clauset, Aaron
2013-10-01
In most professional sports, playing field structure is kept neutral so that scoring imbalances may be attributed to differences in team skill. It thus remains unknown what impact environmental heterogeneities can have on scoring dynamics or competitive advantages. Applying a novel generative model of scoring dynamics to roughly 10 million team competitions drawn from an online game, we quantify the relationship between the structure within a competition and its scoring dynamics, while controlling the impact of chance. Despite wide structural variations, we observe a common three-phase pattern in the tempo of events. Tempo and balance are highly predictable from a competition's structural features alone and teams exploit environmental heterogeneities for sustained competitive advantage. Surprisingly, the most balanced competitions are associated with specific environmental heterogeneities, not from equally skilled teams. These results shed new light on the design principles of balanced competition, and illustrate the potential of online game data for investigating social dynamics and competition.
-
CO2 emission costs and Gas/Coal competition for power production
International Nuclear Information System (INIS)
Santi, Federico
2005-01-01
This paper demonstrates how a CO 2 emission reduction programme can change the competition between the two power production technologies which will probably dominate the future of the Italian power industry: the coal fired USC steam power plant and the natural gas fired CCGT power plant. An economic value of the CO 2 emission is calculated, in order to make the short-run-marginal-cost (or the long-run-marginal-cost). equal for both technologies, under a CO 2 emission trading scheme and following a single-plant specific CO 2 emission homogenizing approach [it
-
International Nuclear Information System (INIS)
Wang, M.; Li, Y.Y.; Niu, P.X.
2015-01-01
Using conventional nearest neighbour analysis and Ripley's L-function, the goal of this study was to analyze spatial patterns of Anabasis aphylla plants in order to investigate underlying competitive processes that shape the population spatial structure from diluvial fan in Junggar Basin, NW China. We found that the spatial patterns of all growth stages were aggregated in the three study plots, and seedling and juvenile plants were more aggregated than expected by chance. Positive associations among growth stages of A. aphylla population were found at a small scale while negative associations of seedling and juvenile relative to adult plants were shown at a larger scale. The processes such as dispersal, seedling establishment, environmental heterogeneity, plant interactions and disturbance may have acted individually or in concert with other processes to produce the aggregated patterns and competitive relationship. Moreover, these findings suggested that the aggregated distribution and the competitive interaction between A. aphylla plants in the diluvial fan reflected not only in mortality, but also in decreased performance (smaller canopy) that was an important characteristic of drought-enduring plant, thus preventing a regular distribution pattern. (author)
-
The modular high-temperature gas-cooled reactor: A cost/risk competitive nuclear option
International Nuclear Information System (INIS)
Gotschall, H.L.
1994-01-01
The business risks of nuclear plant ownership are identified as a constraint on the expanded use of nuclear power. Such risks stem from the exacting demands placed on owner/operator organizations of current plants to demonstrate ongoing compliance with safety regulations and the resulting high costs for operation and maintenance. This paper describes the Modular High-Temperature Gas-Cooled Reactor (MHTGR) design, competitive economics, and approach to reducing the business risks of nuclear plant ownership
-
Plant fertilization: maximizing reproductive success.
Dresselhaus, Thomas; Sprunck, Stefanie
2012-06-19
Sperm competition does not occur in flowering plants as typically only a single pair of sperm cells is delivered for double fertilization. Two recent reports show that plants are capable of avoiding reproductive failure when defective sperm cells are released. Copyright © 2012 Elsevier Ltd. All rights reserved.
-
Loblolly pine seedling response to competition from exotic vs. native plants
Pedram Daneshgar; Shibu Jose; Craig Ramsey; Robin Collins
2006-01-01
A field study was conducted in Santa Rosa County, FL to test the hypothesis that an exotic understory would exert a higher degree of competition on tree seedling establishment and growth than native vegetation. The study site was a 60 ha cutover area infested with the invasive exotic cogongrass [Imperata cylindrica (L.) Raeusch.]. A completely...
-
U.S. Wind Energy Manufacturing and Supply Chain: A Competitiveness Analysis
Energy Technology Data Exchange (ETDEWEB)
Fullenkamp, Patrick H; Holody, Diane S
2014-06-15
customer order at the manufacturing plant; to the orders being forwarded by the manufacturing plant to the material suppliers; to the material being received at the manufacturing plant and processed through the system; to the final product being shipped to the Customer. 3. Competitiveness Scorecard: GLWN developed a Wind Industry Supply Chain Scorecard that reflects U.S. component manufacturers’ readiness to supply the next generation wind turbines, 3MW and 5MW, for land-based and offshore applications. 4. Wind Supply Chain Database & Map: Expand the current GLWN GIS Wind Supply Chain Map to include offshore elements. This is an on-line, free access, wind supply chain map that provides a platform for identifying active and emerging suppliers for the land-based and offshore wind industry, including turbine component manufacturers and wind farm construction service suppliers.
-
Stand competition determines how different tree species will cope with a warming climate.
Directory of Open Access Journals (Sweden)
Laura Fernández-de-Uña
Full Text Available Plant-plant interactions influence how forests cope with climate and contribute to modulate species response to future climate scenarios. We analysed the functional relationships between growth, climate and competition for Pinus sylvestris, Quercus pyrenaica and Quercus faginea to investigate how stand competition modifies forest sensitivity to climate and simulated how annual growth rates of these species with different drought tolerance would change throughout the 21st century. Dendroecological data from stands subjected to thinning were modelled using a novel multiplicative nonlinear approach to overcome biases related to the general assumption of a linear relationship between covariates and to better mimic the biological relationships involved. Growth always decreased exponentially with increasing competition, which explained more growth variability than climate in Q. faginea and P. sylvestris. The effect of precipitation was asymptotic in all cases, while the relationship between growth and temperature reached an optimum after which growth declined with warmer temperatures. Our growth projections indicate that the less drought-tolerant P. sylvestris would be more negatively affected by climate change than the studied sub-Mediterranean oaks. Q. faginea and P. sylvestris mean growth would decrease under all the climate change scenarios assessed. However, P. sylvestris growth would decline regardless of the competition level, whereas this decrease would be offset by reduced competition in Q. faginea. Conversely, Q. pyrenaica growth would remain similar to current rates, except for the warmest scenario. Our models shed light on the nature of the species-specific interaction between climate and competition and yield important implications for management. Assuming that individual growth is directly related to tree performance, trees under low competition would better withstand the warmer conditions predicted under climate change scenarios but in
-
Directory of Open Access Journals (Sweden)
I. Aspiazú
2010-01-01
Full Text Available The objective of this work was to evaluate characteristics associated with the photosynthetic activity of cassava plants under weed competition. The trial was carried out under field conditions, and experimental units consisted of 150 dm³ fiberglass boxes containing red yellow Latosol, previously corrected and fertilized. Treatments consisted in the cultivation of cassava plants which were free of weed competition and associated with three weed species: Bidens pilosa, Commelina benghalensis or Brachiaria plantaginea. After manioc sprouting started, 15 days after being planted, weeds that had been sown when manioc was planted were thinned, there were then eight plants left per experimental unit in accordance with specified treatments: cassava free of competition, cassava competing with B. pilosa, cassava competing with C. benghalensis and cassava competing with B. plantaginea. Sixty days after crop emergence leaf internal CO2 concentration (Ci, leaf temperature at the time of evaluation (Tleaf and photosynthetic rate (A were evaluated, also the CO2 consumption rate (ΔC of cassava plants was calculated. A correlation matrix between variables was also obtained. All characteristics associated with photosynthesis in cassava plants were influenced by weed species. Cassava was more affected by B. pilosa and B. plantaginea in which concerns its exposition to solar radiation and water, while C. benghalensis seems to mostly affect the composition of incident light on the culture, allowing cassava to anticipate imposition when competing, even before it reaches harmful levels.Objetivou-se com este trabalho avaliar características associadas à atividade fotossintética de plantas de mandioca sob competição ou não com plantas daninhas. O experimento foi realizado em condições de ambiente aberto, sendo as unidades experimentais compostas por vasos de fibra de vidro de 150 dm³ preenchidos com Latossolo Vermelho Amarelo, previamente adubado. Os
-
Xue, W.; Bezemer, T.M.; Berendse, Frank
2018-01-01
Backgrounds and aims Negative plant-soil feedbacks (PSFs) are thought to promote species coexistence, but most evidence is derived from theoretical models and data from plant monoculture experiments. Methods We grew Anthoxanthum odoratum and Centaurea jacea in field plots in monocultures and in
-
Directory of Open Access Journals (Sweden)
Anna G Aguilera
Full Text Available Soil communities associated with specific plant species affect individual plants' growth and competitive ability. Limited evidence suggests that unique soil communities can also differentially influence growth and competition at the ecotype level. Previous work with Arabidopsis thaliana has shown that accessions produce distinct and reproducible rhizosphere bacterial communities, with significant differences in both species composition and relative abundance. We tested the hypothesis that soil communities uniquely affect the growth and reproduction of the plant accessions with which they are associated. Specifically, we examined the growth of four accessions when exposed to their own soil communities and the communities generated by each of the other three accessions. To do this we planted focal accessions inside a ring of six plants that created a "background" soil community. We grew focal plants in this design in three separate soil treatments: non-sterile soil, sterilized soil, and "preconditioned" soil. We preconditioned soil by growing accessions in non-sterile soil for six weeks before the start of the experiment. The main experiment was harvested after seven weeks of growth and we recorded height, silique number, and dry weight of each focal plant. Plants grown in the preconditioned soil treatment showed less growth relative to the non-sterile and sterile soil treatments. In addition, plants in the sterile soil grew larger than those in non-sterile soil. However, we saw no interaction between soil treatment and background accession. We conclude that the soil communities have a negative net impact on Arabidopsis thaliana growth, and that the unique soil communities associated with each accession do not differentially affect growth and competition of study species.
-
On nuclear power plant uprating
International Nuclear Information System (INIS)
Ho, S. Allen; Bailey, James V.; Maginnis, Stephen T.
2004-01-01
Power uprating for commercial nuclear power plants has become increasingly attractive because of pragmatic reasons. It provides quick return on investment and competitive financial benefits, while involving low risks regarding plant safety and public objection. This paper briefly discussed nuclear plant uprating guidelines, scope for design basis analysis and engineering evaluation, and presented the Salem nuclear power plant uprating study for illustration purposes. A cost and benefit evaluation of the Salem power uprating was also included. (author)
-
Early root overproduction not triggered by nutrients decisive for competitive success belowground.
Directory of Open Access Journals (Sweden)
Francisco M Padilla
Full Text Available Theory predicts that plant species win competition for a shared resource by more quickly preempting the resource in hotspots and by depleting resource levels to lower concentrations than its competitors. Competition in natural grasslands largely occurs belowground, but information regarding root interactions is limited, as molecular methods quantifying species abundance belowground have only recently become available.In monoculture, the grass Festuca rubra had higher root densities and a faster rate of soil nitrate depletion than Plantago lanceolata, projecting the first as a better competitor for nutrients. However, Festuca lost in competition with Plantago. Plantago not only replaced the lower root mass of its competitor, but strongly overproduced roots: with only half of the plants in mixture than in monoculture, Plantago root densities in mixture were similar or higher than those in its monocultures. These responses occurred equally in a nutrient-rich and nutrient-poor soil layer, and commenced immediately at the start of the experiment when root densities were still low and soil nutrient concentrations high.Our results suggest that species may achieve competitive superiority for nutrients by root growth stimulation prior to nutrient depletion, induced by the presence of a competitor species, rather than by a better ability to compete for nutrients per se. The root overproduction by which interspecific neighbors are suppressed independent of nutrient acquisition is consistent with predictions from game theory. Our results emphasize that root competition may be driven by other mechanisms than is currently assumed. The long-term consequences of these mechanisms for community dynamics are discussed.
-
Control of volunteer soybean plants in sunflower crop
Directory of Open Access Journals (Sweden)
Alexandre Magno Brighenti
2015-09-01
Full Text Available Sunflower (Helianthus annuus sown offseason, after soybean crop (Glycine max, is affected by the competition imposed by volunteer plants. Two experiments were carried out to evaluate the control of volunteer soybean plants in sunflower crops. The sulfentrazone herbicide (75 g ha-1, 100 g ha-1 and 250 g ha-1 causes phytotoxicity to sunflower immediately after application, however, plants recover, with no yield losses. These doses do not cause the total death of volunteer soybean plants, but temporarily paralyzes their growth, avoiding the competition with the sunflower crop. The glufosinate ammonium and ametryn herbicides are effective in controlling volunteer soybean plants, however, symptoms of phytotoxicity in the sunflower crop are high, reflecting in losses of dry weight biomass and crop yield. The other treatments do not provide satisfactory control of volunteer soybean plants and even reduce the sunflower dry weight biomass and yield.
-
International Nuclear Information System (INIS)
1998-01-01
Retail competition as the cornerstone of a competitive electricity marketplace was the subject of the seventh in the series of policy discussion papers developed at the Market Design Conference. Concern was expressed that because of the complexities involved in market design and technical implementation, the retail competition may lag behind other elements of the implementation of the new market design. A variety of key issues were debated, including the role of physical versus financial contracts, the form of retail competition and financial settlement systems in the short term, the requirement to separate 'competitive' (metering, billing, maintenance, consumer education) from non-competitive' (the transmission wires) services and the role of municipal electric utilities. It was agreed that the IMO should play an important role in defining and enforcing the separation of services, and that as a general rule, the development of policy in this area should be guided by the principle of maximizing the potential for competition
-
Competitive intelligence as an enabler for firm competitiveness: An overview
Directory of Open Access Journals (Sweden)
Alexander Maune
2014-06-01
Full Text Available The purpose of this article is to provide an overview, from literature, about how competitive intelligence can be an enabler towards a firm’s competitiveness. This overview is done under the background of intense global competition that firms are currently experiencing. This paper used a qualitative content analysis as a data collection methodology on all identified journal articles on competitive intelligence and firm competitiveness. To identify relevant literature, academic databases and search engines were used. Moreover, a review of references in related studies led to more relevant sources, the references of which were further reviewed and analysed. To ensure reliability and trustworthiness, peer-reviewed journal articles and triangulation were used. The paper found that competitive intelligence is an important enabler of firm competitiveness. The findings from this paper will assist business managers to understand and improve their outlook of competitive intelligence as an enabler of firm competitiveness and will be of great academic value.
-
Market competition in the nuclear industry
International Nuclear Information System (INIS)
Taylor, M.
2008-01-01
The nuclear industry provides a wide variety of specialized equipment and services to support the construction and operation of nuclear power plants (NPPs). This includes the supply of NPPs themselves, the range of materials and services required in the nuclear fuel cycle, and the services and equipment needed for maintenance and upgrading. The markets to provide these have changed substantially as they have evolved from the government-led early stages of the nuclear industry to predominantly competitive, commercial markets today. (author)
-
Unification of the methodology of competitiveness evaluation
Directory of Open Access Journals (Sweden)
Ivanova Marina
2016-05-01
Full Text Available The purpose of the study is the comparison of the modern methods of competitiveness evaluation and testing the results in practice at a production plant in order to unify the methodology. Analysis of the publications shows that the existing diversity in methods of the competitiveness evaluation complicates the choice of a method and interpretation of the results, which confirms the need to classify and unify the methods available today. The authors suggest that the standardized method of competitiveness evaluation should combine matrix and graphical methods. In our study, we have shown that SWOT-analysis should be carried out in two stages: firstly, it is necessary to determine the strengths and weaknesses of the company, taking into account the following factors: marketing, production, economic and financial situation, technology, the administration and personnel; secondly, it is essential to assess the opportunities and threats with the allowance for the political, legal, and economic situation, the impact of market as well as social, cultural and natural environmental factors. The proposed methodology of competitiveness evaluation has been tested at the industrial enterprise "Olvita ltd", which is dynamically developing and successfully operates on the food market of Ukraine; it specializes in processing, logistics and distribution of fresh and frozen vegetables, fruits and berries, as well as ready-to cook meat products. The results have shown that the competitiveness evaluation remains a pressing issue that requires simple and fairly demonstrative methods, one of which is a method that combines both graphical and matrix approaches. The advantage of the proposed method is its sufficiently high visualizations and record of personal approaches in evaluating the scores for strengths and weaknesses as well as opportunities and threats. In the future, the authors are planning to examine and systemize the indicators used in the competitiveness
-
DEFF Research Database (Denmark)
Edelfeldt, Stina; Lundkvist, Anneli; Forkman, Johannes
2016-01-01
To evaluate the effects of weed competition and nitrogen fertilization on the early growth performance of willow, cuttings of the clone Tora (Salix schwerinii x S. viminalis) were planted in buckets together with model weeds (spring barley or white mustard) sown 15, 26, and 30Â days after willow...... gave higher willow biomass production in willow with weeds sown after 26 or 30Â days. Type of model weed had no effect on willow performance. Weed biomass and maximum shoot height were higher in weeds planted without willows compared to the willow-weed mixtures. A high nitrogen level gave more weed...... biomass when planted without willows and in the willow-weed mixture with weeds sown after 15Â days. We conclude that for the given high density of willow, competition from weeds emerging soon after willow planting had strong effect on early production. Furthermore, if there is a risk of weed infestation...
-
Diode-pumped solid-state-laser drivers and the competitiveness of inertial fusion energy
International Nuclear Information System (INIS)
Orth, C.D.
1993-12-01
Based on five technical advances at LLNL and a new systems-analysis code that we have written, we present conceptual designs for diode-pumped solid-state laser (DPSSL) drivers for Inertial Fusion Energy (IFE) power plants. Such designs are based on detailed physics calculations for the drive, and on generic scaling relationships for the reactor and balance of plant (BOP). We describe the performance and economics of such power plants, show how sensitive these results are to changes in the major parameters, and indicate how technological improvements can make DPSSL-driven IFE plants more competitive
-
Directory of Open Access Journals (Sweden)
M Goldani
2015-04-01
Full Text Available In order to study the competition effects of Solanum nigrum on Vigna radiate yield, an additive experiment was conducts at Ferdowsi University of Mashhad experimental Greenhouse. The type of design was completely randomized block. Treatments included three density of Solanum nigrum (2, 4, and 6 plants m-2 and three types of competition (root, shoot and both of them planted at constant density of Vigna radiate plus weed free check in each block. The results indicated that competitions had significant effects (P
-
Coexistence induced by pollen limitation in flowering-plant species.
Ishii, R; Higashi, M
2001-01-01
We report a novel mechanism for species coexistence that does not invoke a trade-off relationship in the case of outbreeding flowering plants. Competition for pollination services may lead to interspecific segregation of the timing of flowering among plants. This, in turn, sets limits on the pollination services, which restrain the population growth of a competitively superior species, thereby allowing an inferior species to sustain its population in the habitat. This explains the often-obser...
-
Directory of Open Access Journals (Sweden)
Haiyan Ren
2017-12-01
Full Text Available Understanding the factors that alter competitive interactions and coexistence between plants is a key issue in ecological research. A pot experiment was conducted to test the effects of root interaction and arbuscular mycorrhizal fungi (AMF inoculation on the interspecies competition between Trifolium repens and Lolium perenne under different proportions of mixed sowing by the combination treatment of two levels of AMF inoculation (inoculation and non-inoculation and two levels of root interaction (root interaction and non-root interaction. Overall, the aboveground and belowground biomass of T. repens and L. perenne were not altered by AMF inoculation across planting ratios, probably because the fertile soil reduced the positive effect of AMF on plant growth. Both inter- and intraspecies root interaction significantly decreased the aboveground biomass of T. repens, but tended to increase the aboveground biomass of L. perenne across planting ratios, and thus peaked at the 4:4 polyculture. These results showed that T. repens competed poorly with L. perenne because of inter and intraspecies root interaction. Our results indicate that interspecies root interaction regulates the competitive ability of grass L. perenne and legume T. repens in mixtures and further makes great contribution for overyielding. Furthermore, AMF may not be involved in plant–plant interaction in fertile condition.
-
Reduction of capital costs of nuclear power plants. NEA-report
International Nuclear Information System (INIS)
2000-01-01
Since the the mid-1980s, the declining real prices of fossil fuels and the significant improvements in thermal efficiencies of combined cycle power plants have eroded the economic competitiveness of nuclear power plants in most OECD countries. In order for nuclear power to remain a viable option for the next millennium, the cost of electricity from nuclear power plant must be greatly reduced to be competitive with alternative sources. Of the three major components of nuclear generation cost - capital, O and M and fuel - the capital cost component makes up approximately 60 per cent of the total. Therefore, identification of the means to reduce the capital costs of nuclear power plants is a high priority activity toward keeping nuclear power competitive. Among a number of capital cost reduction measures, the principal ones were agreed by the expert group as follows: Increased plant size, improved construction methods, reduced construction schedule, design improvement, improved procurement, organisation and contractual aspects, standardisation and construction in series, multiple unit construction, regulatory and policy reform. (orig.)
-
Strategies for a competitive nuclear fuel
International Nuclear Information System (INIS)
Alvarez, J. M.; Rebollo, L.
2001-01-01
In the new framework of electricity generation, Nuclear Power Plants are operated by the electric utilities based on the competition required by an increasingly deregulated and liberalized market so that there is frequently a competition between the strategies of innovation and standardisation. On one had, innovation promotes the use of new technologies, products and/or processes locking for a reduction of costs based on the increase of the operating margins, while, on the other hand, standardisation promotes the use of well known and consolidated technologies, products and/or processes looking for getting the maximum benefit from the accumulated previous operating experience. In order to evaluate the standardisation versus the innovation an analysis of risks and opportunities of each of these strategies applied to the industry of the nuclear fuel has been suggested. As a results of it, a combined strategy innovation + standardisation based on the integration of both basic strategies in a complementary mode, has been suggested, the disadvantages of each of these strategies being compensated with the advantages of the other one. in this way, the total risk is minimized, the global opportunities are maximized and the main overall objective of getting the maximum benefit of the combination of both strategies looking for a competitive nuclear fuel is guaranteed. (Author)
-
Physiological measurements of coffee young plants coexisting with sourgrass
Directory of Open Access Journals (Sweden)
Pedro Luis da Costa Aguiar Alves
2012-03-01
Full Text Available Coffee is an important crop planted in Brazil and commonly infested by sourgrass plants. Crescent densities of sourgrass growing with coffee young plants were maintained up to weed full flowering when physiological measurements were performed in the crop to evaluate photosynthetic coffee plant responses to increasing of weed competition. Experiments were arranged in a completely randomized design with seven replicates. The concentration of CO2 within the leaf, the leaf transpiration, the stomatal conductance, the CO2 assimilation rate, and the ratio Fv/Fm of coffee plants were not affected by increasing of sourgrass density. On the other hand, relative content of total chlorophyll was reduced by 13.9% in the density of 8 sourgrass plants. Gas exchange and fluorescence of chlorophyll of young coffee plants were not dependent on increasing of the intensity of competition while an opposite response occurred for chlorophyll content.
-
African indigenous plants with chemotherapeutic potentials and ...
African Journals Online (AJOL)
Herbal-based and plant-derived products can be exploited with sustainable comparative and competitive advantage. This review presents some indigenous African plants with chemotherapeutic properties and possible ways of developing them into potent pharmacological agents using biotechnological approaches.
-
Directory of Open Access Journals (Sweden)
D.D. Hernandez
2002-08-01
Full Text Available O presente trabalho foi realizado com o objetivo de quantificar as interações competitivas e os índices de competitividade entre plantas de tomate industrial (Lycopersicon esculentum cv. Heinz 9553 e maria-pretinha (Solanum americanum. Usou-se como método um experimento substitutivo, com densidade total de 40 plantas m-2 e 11 proporções, além das monoculturas em densidades, que variaram de 20 a 100 plantas m-2, em intervalos de 20 plantas, conduzidos no delineamento de blocos casualizados com três repetições. Os resultados obtidos foram analisados pelo método convencional de análise de experimentos substitutivos e pela produção recíproca total. A maria-pretinha mostrou ser um competidor mais agressivo que o tomate, sendo mais importante a competição interespecífica para a planta cultivada. Para a biomassa seca total, as duas espécies não competiram pelos mesmos fatores de crescimento. Já para a área foliar, as duas espécies se mostraram competidoras pelos mesmos fatores de crescimento, mostrando ser essa a característica mais sensível à interferência.This work aimed to quantify the competitive interactions and the competitiveness indexes among plants of industrial tomato (Lycopersicon esculentum cv. Heinz 9553 and nightshade (Solanum americanum. The methodology used was a replacement series experiment with a total density of 40 plants m-2 and 11 proportions, besides the monocultures in densities varying from 20 to 100 plants m-2, in intervals of 20 plants, conducted in a randomized complete block design with three replications. The results were analyzed by the conventional method of analysis of replacement series experiment and for total reciprocal production. The nightshade plant was shown to be a more aggressive competitor than the tomato, with inter-specific competition being more important for the cultivated plant. For the dry aboveground biomasses, the two species did not compete for the same natural resources
-
CO{sub 2} mitigation costs of large-scale bioenergy technologies in competitive electricity markets
Energy Technology Data Exchange (ETDEWEB)
Gustavsson, L [Mid-Sweden University, Ostersund (Sweden). Dept. of Natural and Environmental Sciences, Ecotechnology; Madlener, R [Swiss Federal Institute of Technology, Zurich (Switzerland). CEPE
2003-11-01
In this study, we compare and contrast the impact of recent technological developments in large biomass-fired and natural-gas-fired cogeneration and condensing plants in terms of CO{sub 2} mitigation costs and under the conditions of a competitive electricity market. The CO{sub 2} mitigation cost indicates the minimum economic incentive required (e.g. in the form of a carbon tax) to equal the cost of a less carbon extensive system with the cost of a reference system. The results show that CO{sub 2} mitigation costs are lower for biomass systems than for natural gas systems with decarbonization. However, in liberalized energy markets and given the sociopolitical will to implement carbon extensive energy systems, market-based policy measures are still required to make biomass and decarbonization options competitive and thus help them to penetrate the market. This cost of cogeneration plants, however, depends on the evaluation method used. If we account for the limitation of heat sinks by expanding the reference entity to include both heat and power, as is typically recommended in life-cycle analysis, then the biomass-based gasification combined cycle (BIG/CC) technology turns out to be less expensive and to exhibit lower CO{sub 2} mitigation costs than biomass-fired steam turbine plants. However, a heat credit granted to cogeneration systems that is based on avoided cost of separate heat production, puts the steam turbine technology despite its lower system efficiency at an advantage. In contrast, when a crediting method based on avoided electricity production in natural gas fired condensing plants is employed, the BIG/CC technology turns out to be more cost competitive than the steam turbine technology for carbon tax levels beyond about $150/t C. Furthermore, steam turbine plants are able to compete with natural gas fired cogeneration plants at carbon tax levels higher than about $90/tC. (author)
-
International Nuclear Information System (INIS)
Borth, F.C. III; Thompson, J.W.; Mishaga, J.M.
1996-01-01
Through ComEd Fossil (Generating) Division's Competitive Action Plan (CAP) evaluation changes have been identified which are necessary to improve generating station performance. These changes are intended to improve both station reliability and financial margins, and are essential for stations to be successful in a competitive marketplace. Plant upgrades, advanced equipment stewardship, and personnel reductions have been identified as necessary steps in achieving industry leadership and competitive advantage. To deal effectively with plant systems and contend in the competitive marketplace Information Technology (IT) solutions to business problems are being developed. Data acquisition, storage, and retrieval are being automated through use of state-of-the-art Data Historians. Total plant, high resolution, long term process information will be accessed through Local/Wide Area Networks (LAN/WAN) connections from desktop PC's. Generating unit Thermal Performance Monitors accessing the Data Historian will analyze plant and system performance enabling reductions in operating costs, and improvements in process control. As inputs to proactive maintenance toolsets this data allows anticipation of equipment service needs, advanced service scheduling, and cost/benefit analysis. The ultimate goal is to optimize repair needs with revenue generation. Advanced applications building upon these foundations will bring knowledge of the costs associated with all the products a generating station offers its customer(s). An overall design philosophy along with preliminary results is presented; these results include shortfalls, lessons learned, and future options
-
Expansion of plants with Crassulacean Acid Metabolism under global environment change
Yu, K.; D'Odorico, P.; Collins, S. L.; Carr, D.
2016-12-01
The abundance of plants with Crassulacean Acid Metabolism (CAM) has increased in many drylands worldwide. This is hypothesized to occur because CAM plants store water, take up CO2 at night, exhibit photosynthetic plasticity, and have high water use efficiency. The increased dominance of CAM plants, however, also depends on their competitive relationship with other functional groups, an aspect of CAM plant sensitivity to global environmental change that has remained largely understudied. Here, we investigated the response of CAM plants and their competitive relationships with C3 and C4 plants under global environmental change. We focused on two pairs of CAM and non-CAM species, namely Cylindropuntia imbricata (a constitutive CAM species) and Bouteloua eriopoda (C4 grass), which co-occur in desert grasslands in northern Mexico, and invasive Mesembryanthemum crystallinum (a facultative CAM species) and Bromus mollis (a C3 invasive grass), which coexist in California's coastal grasslands. A set of growth chamber experiments under altered CO2 and water conditions show that C. imbricata outcompeted B. eriopoda under drought conditions, while in well-watered conditions B. eriopoda was a stronger competitor for soil water than C. imbricata. Under drought conditions a more positive response to CO2 enrichment by C. imbricata indirectly disfavored B. eriopoda, which suggests that interspecific competition can outweigh the favorable direct effect of CO2 enrichment on plant growth. A set of greenhouse experiments under water, N, and soil salinity manipulations showed that drought, N deposition, and/or increased soil salinity served as important drivers for success of M. crystallinum invasion, while B. mollis exerted strong competitive effects on M. crystallinum for light and soil nutrients in well-watered conditions. M. crystallinum switched from C3 photosynthesis to CAM photosynthesis as an adaptive strategy in response to moderate intensity of competition from B. mollis, in
-
Improving Genomic Prediction in Cassava Field Experiments by Accounting for Interplot Competition.
Elias, Ani A; Rabbi, Ismail; Kulakow, Peter; Jannink, Jean-Luc
2018-03-02
Plants competing for available resources is an unavoidable phenomenon in a field. We conducted studies in cassava ( Manihot esculenta Crantz) in order to understand the pattern of this competition. Taking into account the competitive ability of genotypes while selecting parents for breeding advancement or commercialization can be very useful. We assumed that competition could occur at two levels: (i) the genotypic level, which we call interclonal, and (ii) the plot level irrespective of the type of genotype, which we call interplot competition or competition error. Modification in incidence matrices was applied in order to relate neighboring genotype/plot to the performance of a target genotype/plot with respect to its competitive ability. This was added into a genomic selection (GS) model to simultaneously predict the direct and competitive ability of a genotype. Predictability of the models was tested through a 10-fold cross-validation method repeated five times. The best model was chosen as the one with the lowest prediction root mean squared error (pRMSE) compared to that of the base model having no competitive component. Results from our real data studies indicated that value reached up to 25% with a GS-competition error model. We also found that the competitive influence of a cassava clone is not just limited to the adjacent neighbors but spreads beyond them. Through simulations, we found that a 26% increase of accuracy in estimating trait genotypic effect can be achieved even in the presence of high competitive variance. Copyright © 2018 Elias et al.
-
Improving the economics and competitiveness of nuclear power in China
International Nuclear Information System (INIS)
Jing Chunning; Tian Jiashu
2005-01-01
A cost structure of nuclear power plant is introduced in this paper. Various factors that influence the nuclear power economics are discussed in detail. A preliminary study is carried out for the short-term new nuclear power plants in China. Focusing on the Chinese nuclear power development strategy, the short term and mid-long term economics of nuclear power in China is analyzed. Based on analysis and comparison, suggestions and proposals for improving the economics and competitiveness of nuclear power in China are provided. (authors)
-
Bergeron, Pierrette; Hiller, Christine A.
2002-01-01
Reviews the evolution of competitive intelligence since 1994, including terminology and definitions and analytical techniques. Addresses the issue of ethics; explores how information technology supports the competitive intelligence process; and discusses education and training opportunities for competitive intelligence, including core competencies…
-
Designing powerplants for today's competitive environment
International Nuclear Information System (INIS)
Makansi, J.
1994-01-01
Deregulation continues to unfold. Certainty about what the impact will be is as scarce as new US powerplant development opportunities. But one thing industry observers seem clear on is that the priorities for powerplant design will shift as competitive forces are rolled out. Powerplants will have to be developed, designed, and operated as a bottom-line business, not as part of a regulated industry. Thus, the design must enable the facility to accomplish this goal. In the emerging fully competitive environment, that bottom line applies to both the kilowatt and the kilowatt-hour. The entrepreneurial and business skills and talents of the independent power producer (IPP) have mostly been brought to bear on capital costs and project development thus far, with electricity sold under long-term power-purchase agreements. If retail wheeling takes hold, future plants must also be designed to merchandise power to a variety of customers scattered around the grid. This article provides insight into how powerplant design will accommodate new priorities
-
Healthy Competition and Unsound Comparison: Reforming Educational Competition in Singapore
Christensen, Søren
2015-01-01
It is frequently claimed that the "competition state" responds to external competition by making competition increasingly central to its internal processes as well. This article discusses education reform in Singapore as departing from the opposite position. In Singapore "excessive" competition in education is now targeted by…
-
Game theory and plant ecology.
McNickle, Gordon G; Dybzinski, Ray
2013-04-01
The fixed and plastic traits possessed by a plant, which may be collectively thought of as its strategy, are commonly modelled as density-independent adaptations to its environment. However, plant strategies may also represent density- or frequency-dependent adaptations to the strategies used by neighbours. Game theory provides the tools to characterise such density- and frequency-dependent interactions. Here, we review the contributions of game theory to plant ecology. After briefly reviewing game theory from the perspective of plant ecology, we divide our review into three sections. First, game theoretical models of allocation to shoots and roots often predict investment in those organs beyond what would be optimal in the absence of competition. Second, game theoretical models of enemy defence suggest that an individual's investment in defence is not only a means of reducing its own tissue damage but also a means of deflecting enemies onto competitors. Finally, game theoretical models of trade with mutualistic partners suggest that the optimal trade may reflect competition for access to mutualistic partners among plants. In short, our review provides an accessible entrance to game theory that will help plant ecologists enrich their research with its worldview and existing predictions. © 2013 Blackwell Publishing Ltd/CNRS.
-
Ma, Y T; Wubs, A M; Mathieu, A; Heuvelink, E; Zhu, J Y; Hu, B G; Cournède, P H; de Reffye, P
2011-04-01
and vegetative sink strength on fruit-set and fruit weight. When the source-sink ratio at fruit-set decreased, the number of fruit retained on the plant increased competition for assimilates with vegetative organs. Therefore, total plant and vegetative dry weights decreased, especially for large-fruited cultivars. Optimization study showed that temporal heterogeneity of fruit-set and ripening was predicted to be reduced when fruits were harvested earlier. Furthermore, there was a 20 % increase in the number of extra fruit set.
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Blayais comprises 4 production units of 900 MW each (3600 MW as a whole). The facility generated 21.3 billion kWh in 2009, i.e. 5.5% of the French national power generation and 1.2 times the energy consumed in the Aquitaine region. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
Bleaching herbicide norflurazon inhibits phytoene desaturase by competition with the cofactors.
Breitenbach, J; Zhu, C; Sandmann, G
2001-11-01
Cofactor requirement was determined for the heterologous expressed phytoene desaturases from the cyanobacterium Synechococcus and the higher plant Gentiana lutea. The cyanobacterial enzyme is dependent on either NAD(P) or plastoquinone, whereas only quinones such as plastoquinone can function as a cofactor for the phytoene desaturase from G. lutea. Enzyme kinetic studies were carried out to determine a possible competition between the cofactors and the bleaching herbicide norflurazon. For the Synechococcus enzyme, competition between norflurazon and NADP, as well as plastoquinone, could be demonstrated. The K(m) values for these cofactors were 6.6 mM and 0.23 microM, respectively. Inhibition of the phytoene desaturase from G. lutea by norflurazon was also competitive with respect to plastoquinone. The K(m) values of both enzymes for plastoquinone were very close.
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Paluel comprises 4 production units of 1300 MW each (5200 MW as a whole). The facility generated 29.5 billion kWh in 2009, i.e. about 7% of the French national power generation and 35% of the energy produced in the Normandie region. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Bugey comprises 4 production units of 900 MW each (3600 MW as a whole). The facility generated 20.87 billion kWh in 2009, i.e. 5% of the French national power generation and 40% of the energy consumed in the Rhone-Alpes region. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
EDITORIAL: Physics competitions Physics competitions
Jordens, H.; Mathelitsch, L.
2010-07-01
This editorial opens the second special section on physics competitions in European Journal of Physics. In the first section last year, we asked for feedback on the idea of such a section and on the content of the articles. We received no answer whatsoever, which can be interpreted in two ways: the section is not interesting enough to raise motivation for feedback, or the reader is satisfied. Having no indication which scenario is the correct one, we are optimistic and favour the second. The section at hand contains three articles. Again, as last year, the organizer of the annual Olympiad reports on tasks and outcomes of this competition. The Olympiad took place in Merida, Mexico, and was by far the largest event with 316 contestants from 68 countries. Again, the predominance of Asian/Chinese students was manifest, showing how serious the training is taken by both their authorities and students. Unfortunately, the winners of the last International Young Physicists' Tournament (IYPT), the team from Korea, did not accept the offer to report on their prize-winning contribution. We are thankful that two students from Austria, who achieved second place with their team, took over and reported on the task which they presented in the finals of the competition. It connects the fields of sport and physics and explains a special move in skateboarding. The third contribution introduces a different competition, 'International Conference of Young Scientists'. On one hand, as in the Olympiad, it addresses individuals, not teams. On the other, as in the IYPT, students have several months to prepare and also the quality of the presentation is an important element of the judgment. In fact, this competition comes closer to real scientific research compared to the other events. Finally and again, we hope that this section will serve several purposes: To show the competitions as a very important tool in the support of gifted students. To raise awareness amongst university teachers, and
-
International Nuclear Information System (INIS)
Hattori, Toru
2010-01-01
Since the electricity retail market in Japan was partially opened to competition in 2000, many government entities have sought to solicit competing bids for the electricity supply to their office buildings or facilities, encouraging competition between the incumbents and new entrants. However, in many cases, only the incumbent utility bids for the contract and the competitive effects are limited. This paper presents a statistical analysis of bidders' participation in competitive procurement. We employ several count data regression models to explain the number of bidders other than the local electric utility. Our results suggest that the number of bidders would decrease in response to an increase in the load factor, perhaps because the new entrants are less competitive in serving customers with high load factors as they do not operate low-cost base-load power plants such as nuclear power plants; It would increase along with the voltage level and contract demand. The results also indicate that new entrants are more likely to participate in the bidding process in large city areas. (author)
-
Directory of Open Access Journals (Sweden)
Irena Januskaitiene
2018-03-01
Full Text Available This work focuses on the investigation of competition interaction between C3 crop barley (Hordeum vulgare L. and C4 weed barnyard grass (Echinochloa crus-galli L. at 2 times higher than ambient [CO2] and +4 0C higher ambient temperature climate conditions. It was hypothesized that interspecific competition will change the response of the investigated plants to increased [CO2] and temperature. The obtained results showed that in the current climate conditions, a higher biomass and photosynthetic rate and a lower antioxidant activity were detected for barley grown under interspecific competition effect. While in the warmed climate and under competition conditions opposite results were detected: a higher water use efficiency, a higher photosynthetic performance, a lower dissipated energy flux and a lower antioxidant enzymes activity were detected for barnyard grass plants. This study highlights that in the future climate conditions, barnyard grass will become more efficient in performance of the photosynthetic apparatus and it will suffer from lower oxidative stress caused by interspecific competition as compared to barley.
-
Malmer, Nils; Albinsson, C; Svensson, B M; Wallén, Bo
2003-01-01
The interference between vascular plants and peat mosses with respect to nitrogen and phosphorus was studied in a fertilization experiment and with respect to competition for light in a removal experiment in poor fens with either soligenous or topogenous hydrology using Narthecium ossifragum (L.) Huds. and three species of Sphagnum sect. Sphagnum as targets. Adding fertilizer either on the moss surface or below it confirmed the hypotheses of an asymmetric competition for nutrients, viz. that ...
-
International Nuclear Information System (INIS)
Kelly, J.
1998-01-01
In the Unites States the prospect of greater competition in wholesale power market was immediately eclipsed by talk of retail competition. Attempts to move to retail competition have been costly and complex. Prudent public policy and economic analyses suggest that retail competition not be implemented until it can first be demonstrated that effective competition exists in wholesale power markets [it
-
Mueller, Rob; Murphy, Gloria
2010-01-01
This slide presentation describes a competition to design a lunar robot (lunabot) that can be controlled either remotely or autonomously, isolated from the operator, and is designed to mine a lunar aggregate simulant. The competition is part of a systems engineering curriculum. The 2010 competition winners in five areas of the competition were acknowledged, and the 2011 competition was announced.
-
Competition in the electric industry
International Nuclear Information System (INIS)
Jones, Mel
1998-01-01
Deregulation of the electric power industry is changing the 'personality' of utilities and the way they operate in order to survive in a more competitive marketplace. This paper will identify and discuss key issues NAC International believes will arise as the nuclear industry responds to deregulation. The regulatory treatment of such issues as retail wheeling, recovery of stranded costs, divestiture of assets and securitization will have a significant impact on how utilities, particularly those with nuclear assets, proceed into the new marketplace. While some will survive as a result of innovative thinking, cost control, and entrance into new niche markets, others will be forced to reassess their viability altogether. Increased mergers and acquisitions and early plant closures are potential consequences of these struggles. Meanwhile, innovative companies will develop and enter into new nuclear markets including most notably the acquisition of generating assets. Other key drivers that will significantly impact the competitiveness of nuclear versus other fuels will be the resolution of the nuclear waste issue, the reduction of O and M and decisions regarding whether to make expensive capital additions. Additionally, this paper will present an overview of key regulatory and legislative initiatives impacting electricity. Finally, this paper will examine the roles of regulating bodies such as the Nuclear Regulatory Commission, Federal Energy Regulatory Commission, and state utility commissions, and will provide an outlook for further legislative and regulatory actions in this competitive environment. (author)
-
Izaguirre, Miriam M; Mazza, Carlos A; Astigueta, María S; Ciarla, Ana M; Ballaré, Carlos L
2013-09-01
Plant fitness is often defined by the combined effects of herbivory and competition, and plants must strike a delicate balance between their ability to capture limiting resources and defend against herbivore attack. Many plants use indirect defenses, such as volatile compounds and extra floral nectaries (EFN), to attract canopy arthropods that are natural enemies of herbivorous organisms. While recent evidence suggests that upon perception of low red to far-red (R:FR) ratios, which signal the proximity of competitors, plants down-regulate resource allocation to direct chemical defenses, it is unknown if a similar phytochrome-mediated response occurs for indirect defenses. We evaluated the interactive effects of R:FR ratio and simulated herbivory on nectar production by EFNs of passion fruit (Passiflora edulis f. flavicarpa). The activity of petiolar EFNs dramatically increased in response to simulated herbivory and hormonal treatment with methyl jasmonate (MeJA). Low R:FR ratios, which induced a classic "shade-avoidance" repertoire of increased stem elongation in P. edulis, strongly suppressed the EFN response triggered by simulated herbivory or MeJA application. Strikingly, the EFN response to wounding and light quality was localized to the branches that received the treatments. In vines like P. edulis, a local response would allow the plants to precisely adjust their light harvesting and defense phenotypes to the local conditions encountered by individual branches when foraging for resources in patchy canopies. Consistent with the emerging paradigm that phytochrome regulation of jasmonate signaling is a central modulator of adaptive phenotypic plasticity, our results demonstrate that light quality is a strong regulator of indirect defenses.
-
Plant toxicity, adaptive herbivory, and plant community dynamics
Feng, Z.; Liu, R.; DeAngelis, D.L.; Bryant, J.P.; Kielland, K.; Stuart, Chapin F.; Swihart, R.K.
2009-01-01
We model effects of interspecific plant competition, herbivory, and a plant's toxic defenses against herbivores on vegetation dynamics. The model predicts that, when a generalist herbivore feeds in the absence of plant toxins, adaptive foraging generally increases the probability of coexistence of plant species populations, because the herbivore switches more of its effort to whichever plant species is more common and accessible. In contrast, toxin-determined selective herbivory can drive plant succession toward dominance by the more toxic species, as previously documented in boreal forests and prairies. When the toxin concentrations in different plant species are similar, but species have different toxins with nonadditive effects, herbivores tend to diversify foraging efforts to avoid high intakes of any one toxin. This diversification leads the herbivore to focus more feeding on the less common plant species. Thus, uncommon plants may experience depensatory mortality from herbivory, reducing local species diversity. The depensatory effect of herbivory may inhibit the invasion of other plant species that are more palatable or have different toxins. These predictions were tested and confirmed in the Alaskan boreal forest. ?? 2009 Springer Science+Business Media, LLC.
-
Directory of Open Access Journals (Sweden)
sara parande
2018-02-01
Full Text Available Introduction: Light is a vital component for photosynthesis and plays a significant role in the competitive ability of plants. The nitrogen response of competing plants may be affected by radiation availability and maximum potential growth rate, which determine N requirements. Shading reduces the light intensity, which leads to changes in the morphology, physiology, biomass, grain yield and quality of crops. Finally, shading stress delays flowering and decreases biomass and grain yield. Because photosynthesis is associated with dry matter accumulation, and light is known to limit carbon accumulation and nitrogen content, understanding these processes in weeds may provide insight as to their effects on crop production, help to predict their occurrence, and ultimately provide the needed information for their management. Materials and Methods: In order to evaluate foxtail millet competition with pigweed at different levels of radiation and nitrogen, two separate experiments in split plot arranged in randomized complete block design with three replications were conducted in 2015 at the Research Farm of Birjand University. Texturally, the soil was loam, with 8.16 pH, 0.03% total N, 12 ppm available P and 250 ppm available K. The experiment was laid out in a split-plot design with three replications having three shade levels (0, 41 and 75% shade in main plot and three pigweed density (0, 12 and 24 plant per meter square in subplots in two separate experiments, one under nitrogen application and the other without it. In 0% shade treatment, sunlight was allowed to fall over the millet and pigweed without any barrier. In 41% and 75% treatments, the light levels in the form of PAR were reduced using sheds nets. At the end of growth stage millet traits including plant height, spike length, peduncle length, stem diameter, number of leaf, lodging, grain yield and biomass and pigweed traits such as plant height, number of Lateral branches, number of seed per
-
Does stronger pollen competition improve offspring fitness when pollen load does not vary?
Pélabon, Christophe; Hennet, Lauriane; Bolstad, Geir H; Albertsen, Elena; Opedal, Øystein H; Ekrem, Runa K; Armbruster, W Scott
2016-03-01
Competition among pollen grains from a single donor is expected to increase the quality of the offspring produced because of the recessive deleterious alleles expressed during pollen-tube growth. However, evidence for such an effect is inconclusive; a large number of studies suffer from confounding variation in pollen competition with variation in pollen load. In this study, we tested the effect of pollen competition on offspring performance independently of pollen-load variation. We compared seed mass and early seedling performance in Dalechampia scandens (Euphorbiaceae) between crosses in which variation in pollen competition was achieved, without variation in pollen load, by manipulating the dispersion of pollen grains on the stigmas. Despite a large sample size (211 crosses on 20 maternal plants), we failed to find an effect of pollen competition on seed characteristics or early seedling performance. Paternal effects were always limited, and pollen competition never reduced the within-father (residual) variance. These results suggest that limited within-donor variation in genetic quality of pollen grains reduces the potential benefits of pollen competition in the study population. The lack of paternal effects on early sporophyte performance further suggests that benefits of pollen competition among pollen from multiple donors should be limited as well, and it raises questions about the significance of pollen competition as a mechanism of sexual selection. © 2016 Botanical Society of America.
-
The economics of new nuclear power plants in liberalized electricity markets
International Nuclear Information System (INIS)
Linares, Pedro; Conchado, Adela
2013-01-01
Even after Fukushima, the nuclear debate is strong in many countries, with the discussion of its economics being a significant part of it. However, most of the estimates are based on a levelized-cost methodology, which presents several shortcomings, particularly when applied to liberalized electricity markets. Our paper provides results based on a different methodology, by which we determine the break-even investment cost for nuclear power plants to be competitive with other electricity generation technologies. Our results show that the cost competitiveness of nuclear power plants is questionable, and that public support of some sort would be needed if new nuclear power plants are to be built in liberalized markets. - Highlights: • We propose an alternative more realistic than LEC for the evaluation of the economics of nuclear electricity. • Our results show that the cost competitiveness of nuclear power plants is questionable. • Building nuclear power plants will require public support, particularly regarding risk management. • These results are less optimistic than previous, LEC-based, estimates
-
Competition between coal and gas for large scale power generation
International Nuclear Information System (INIS)
Howieson, B.
1997-01-01
The relative competitiveness of coal- and gas-fired generation will be affected by distinctive country and market factors as well as site specific considerations, regarding such factors as environment, market structure and economics (such as fuel and plant costs). National and international politics have an impact on all three factors and any decision on the development of generation plant must take into account both current and future political climates. An analysis suggests that, at the present time, upgrading existing coal stations is attractive compared with new combined cycle gas turbines (CCGTs). However, this conclusion is highly dependent on the site specific nature of existing plant and the anticipated future environmental regime. Increased environmental pressure, particularly in the area of CO 2 emissions, would result in CCGTs being the first choice plant option. (R.P.)
-
Use of passive systems to improve plant operation and maintenance
International Nuclear Information System (INIS)
Shah, D.
2000-01-01
In a deregulated future, a utility's strength will depend on its ability to be cost competitive in the marketplace. However, the competitive advantage of nuclear power will depend on each owner's ability to reduce Operating and Maintenance (O and M) costs without sacrificing nuclear safety. The use of passive systems (i.e., systems without any moving parts) can reduce plant O and M costs while increasing safety in nuclear power plants. (author)
-
Directory of Open Access Journals (Sweden)
B. Saadatian
2012-04-01
Full Text Available To evaluate the role of effective factors on competition of two wheat cultivars against two species of narrow leaf and broad leaf weeds this study was conducted as two separated experiments based on a randomized complete block design with 3 replications at Agricultural Faculty of Bu-Ali Sina University, in 2008-2009. In both Experiments, Alvand and Sayson cultivars were planted with densities of 450 plants m-2. In the 1st experiment, rye with densities of 0, 20, 40, 60 and 80 plants m-2 were planted in inter-rows of wheat. In the 2nd experiment, wild mustard densities were 0, 8, 16, 24 and 32 plants m-2. The results showed that characters such as vertical distribution of leaf area index and dry matter, height and its increase rate in interference, emergence rate, rate of canopy development and precocity led to increasing competitive ability of Alvand than Sayson in competition with two weed species. These factors were effective in reduction seed production of weeds and economic threshold in Alvand. Despite of lower height of wild mustard than rye, distribution of leaf area and canopy structure of wild mustard increased light competition ability and shadow on crop, so that harmful effects of individual plant of wild mustard in different densities was more than rye. Increasing rate of wild mustard seed bank was more than ray.
-
Moving targets. Economic competitiveness of nuclear power
International Nuclear Information System (INIS)
Rogner, H.H.; Langlois, L.
2000-01-01
Most world electricity markets are now moving towards greater competition, driven in part by technology, low fuel prices, and experience that competitive markets are more self-sustaining. Electric power is being sold in a number of markets in member countries of the Organization for Economic Cooperation and Development (OECD) for around US $0.02 per kilowatt-hour (kWh). Can nuclear generation match such prices? If not, can it be made to do so? Electricity companies are now in the business of selling a commodity (kWh) and commercial services instead of a strategic good. Excess capacity, low demand growth and lower product prices in major industrialized countries have forced power generators and their suppliers to be more concerned with the costs of their operations and profitability of their investments. These companies increasingly need a commercial, profit-oriented approach if they are to survive and prosper. Even more, they will need to make substantial cost reductions over the next few years. The nuclear industry is no exception. How does nuclear power stack up in this environment? The IAEA Planning and Economic Studies Section is doing a series of studies on precisely these questions, divided into issues affecting the near, medium and long-term future of nuclear power. This corresponds roughly to matters affecting existing plants, upgrades and life extensions, or new plants. In general, the studies find that nuclear power has the potential to be competitive in all three markets. But realizing that potential will require significant changes on the part of the industry and its regulators. This article focuses on the prevailing market situation in many industrialized countries. Several lessons also are applicable to developing countries, particularly in cases where the financing of electric power projects is expected to come from international capital markets. The overall situation is distinctly different for developing countries. Typically the capacity there for
-
Zheng, Yucong; Wang, Xiaochang; Dzakpasu, Mawuli; Zhao, Yaqian; Ngo, Huu Hao; Guo, Wenshan; Ge, Yuan; Xiong, Jiaqing
2016-05-01
The outcome of competition between adjoining interspecific colonies of Phragmites and Typha in two large field pilot-scale free water surface (FWS) and subsurface flow (SSF) CWs is evaluated. According to findings, the effect of interspecific competition was notable for Phragmites australis, whereby it showed the highest growth performance in both FWS and SSF wetland. In a mixed-culture, P. australis demonstrates superiority in terms of competitive interactions for space between plants. Furthermore, the interspecific competition among planted species seemed to cause different ecological responses of plant species in the two CWs. For example, while relatively high density and shoot height determined the high aboveground dry weight of P. australis in the FWS wetland, this association was not evident in the SSF. Additionally, while plants nutrients uptake accounts for a higher proportion of the nitrogen removal in FWS, that in the SSF accounts for a higher proportion of the phosphorous removal. Copyright © 2016 Elsevier Ltd. All rights reserved.
-
Bridoux, F.; Vodosek, M.; Den Hartog, D.N.; McNett, J.M.
2014-01-01
Competition traditionally refers to the actions that firms take in a product market to outperform rivals in attracting customers and generating revenues. Yet, competition extends beyond product markets to other arenas such as factor markets, where firms compete for resources, and the political
-
Zheng, Yu-Long; Feng, Yu-Long; Zhang, Li-Kun; Callaway, Ragan M; Valiente-Banuet, Alfonso; Luo, Du-Qiang; Liao, Zhi-Yong; Lei, Yan-Bao; Barclay, Gregor F; Silva-Pereyra, Carlos
2015-02-01
The evolution of increased competitive ability (EICA) hypothesis and the novel weapons hypothesis (NWH) are two non-mutually exclusive mechanisms for exotic plant invasions, but few studies have simultaneously tested these hypotheses. Here we aimed to integrate them in the context of Chromolaena odorata invasion. We conducted two common garden experiments in order to test the EICA hypothesis, and two laboratory experiments in order to test the NWH. In common conditions, C. odorata plants from the nonnative range were better competitors but not larger than plants from the native range, either with or without the experimental manipulation of consumers. Chromolaena odorata plants from the nonnative range were more poorly defended against aboveground herbivores but better defended against soil-borne enemies. Chromolaena odorata plants from the nonnative range produced more odoratin (Eupatorium) (a unique compound of C. odorata with both allelopathic and defensive activities) and elicited stronger allelopathic effects on species native to China, the nonnative range of the invader, than on natives of Mexico, the native range of the invader. Our results suggest that invasive plants may evolve increased competitive ability after being introduced by increasing the production of novel allelochemicals, potentially in response to naïve competitors and new enemy regimes. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.
-
Michael E. Porter; Mariko Sakakibara
2004-01-01
This article examines competition in Japan and its link to postwar economic prosperity. While Japan's industrial structure and competition policy seem to indicate that competition in Japan has been less intense, the empirical evidence does not support this conclusion. The sectors in which competition was restricted prove to be those where Japan was not internationally successful. In the internationally successful sectors, internal competition in Japan was invariably fierce. While the level of...
-
Competitive bidding in Medicare: who benefits from competition?
Song, Zirui; Landrum, Mary Beth; Chernew, Michael E
2012-09-01
To conduct the first empirical study of competitive bidding in Medicare. We analyzed 2006-2010 Medicare Advantage data from the Centers for Medicare and Medicaid Services using longitudinal models adjusted for market and plan characteristics. A $1 increase in Medicare's payment to health maintenance organization (HMO) plans led to a $0.49 (P service plans included, higher Medicare payments increased bids less ($0.33 per dollar), suggesting more competition among these latter plans. As a market-based alternative to cost control through administrative pricing, competitive bidding relies on private insurance plans proposing prices they are willing to accept for insuring a beneficiary. However, competition is imperfect in the Medicare bidding market. As much as half of every dollar in increased plan payment went to higher bids rather than to beneficiaries. While having more insurers in a market lowered bids, the design of any bidding system for Medicare should recognize this shortcoming of competition.
-
Competitive Priorities and Competitive Advantage in Jordanian Manufacturing
Awwad, Abdulkareem S.; Al Khattab, Adel A.; Anchor, J.R
2013-01-01
The purpose of this research was to explore and predict the relationship between the competitive priorities (quality, cost, flexibility and delivery) and the competitive advantage of firms in the Jordanian Industrial Sector. A population of 88 Jordanian manufacturing firms, registered on the Amman Stock Exchange, was targeted using a cross-sectional survey employing a questionnaire method of data collection. The results of the data analysis indicate a significant relationship between competit...
-
Fort, Hugo
2017-01-01
We derive an analytical approximation for making quantitative predictions for ecological communities as a function of the mean intensity of the inter-specific competition and the species richness. This method, with only a fraction of the model parameters (carrying capacities and competition coefficients), is able to predict accurately empirical measurements covering a wide variety of taxa (algae, plants, protozoa).
-
Nuclear power plants and their position in the competitive generation industry of the USA
International Nuclear Information System (INIS)
Petroll, M.R.
2000-01-01
One effect to be observed in the USA is that power trading in the deregulated electricity sector initiates a 'comeback' of the nuclear power stations, reputed to be dead by anti-nuclear power policy followers. Quite to the contrary, growing competition in the generation industry and the resulting upward pressure on costs increasingly induce power generation companies to enter into competitive buying of nuclear power stations, which offer better availability and prolonged service life. The article gives the technical details and explains the economic reasons for this trend in an analysis comparing nuclear power generation with conventional or new non-nuclear generation technologies. (orig./CB) [de
-
AP1000: Meeting economic goals in a competitive world. Annex 7
International Nuclear Information System (INIS)
Davis, G.; Cummins, E.; Winters, J.
2002-01-01
In the U.S., conditions are becoming more favorable for considering the nuclear option again for new baseload generation. While oil and natural gas prices have risen, the cost of operating the existing fleet of nuclear plants has decreased. Furthermore, an advanced 1000 MWe nuclear plant that will be even more cost-competitive with fossil fuels and natural gas will be available by 2005. Westinghouse, in an effort to further improve on the AP600's cost competitiveness, has developed the AP1000, a two-loop, 1000 MWe, advanced pressurized water reactor (PWR) with passive safety features and extensive plant simplifications to enhance the construction, operation, and maintenance. Like the AP600, the AP1000 uses proven technology that builds on over 30 years of operating PWR experience. Westinghouse has completed design studies that demonstrate that it is feasible to increase the power output of the AP600 to at least 1000 MWe, maintaining its current design configuration and licensing basis. To maximize the cost savings, the AP1000 has been designed within the space constraints of the AP600, while retaining the credibility of proven components and substantial safety margins. The affect on the plant's overnight cost of the increased major components that is required to uprate the AP600 to 1000 MWe is small. This overall cost addition is on the order of 11 percent, while the overall power increase is almost 80 percent. This paper describes the changes made to uprate the AP600 and gives an overview of the plant design. (author)
-
The Literature Review of a New Form of Competitiveness Called City Competitiveness
Directory of Open Access Journals (Sweden)
Osman EROĞLU
2014-06-01
Full Text Available With globalization, the rapid development of information technologies and the rapid changes in the economic structure, the country’s borders at a time increasingly depreciate and the importance of city competitiveness reveals. Although it is an ongoing debate around the world whether cities compete with each other, city competitiveness is a new form of competitiveness. Cities compete with each other to increase their competitiveness. City competitiveness is defined as having better values compared to other cities. In this study, a new form of competitiveness called city competitiveness is examined.
-
Growth and nutritive quality of Poa pratensis as influenced by ozone and competition
International Nuclear Information System (INIS)
Bender, J.; Muntifering, R.B.; Lin, J.C.; Weigel, H.J.
2006-01-01
Interspecific plant competition has been hypothesized to alter effects of early-season ozone (O 3 ) stress. A phytometer-based approach was utilized to investigate O 3 effects on growth and nutritive quality of Poa pratensis grown in monoculture and in mixed cultures with four competitor-plant species (Anthoxanthum odoratum, Achillea millefolium, Rumex acetosa and Veronica chamaedrys). Mesocosms were exposed during April/May 2000-2002 to charcoal-filtered air + 25 ppb O 3 (control) or non-filtered air + 50 ppb O 3 (elevated O 3 ). Biomass production was not affected by O 3 , but foliar injury symptoms were observed in May 2002. Early-season O 3 exposure decreased relative food value of P. pratensis by an average of 8%, which is sufficient to have nutritional implications for its utilization by herbivores. However, forage quality response to O 3 was not changed by interspecific competition. Lack of injury and nutritive quality response in P. pratensis harvested in September may reflect recovery from early-season O 3 exposure. - Early-season O 3 exposure decreased nutritive quality of Poa pratensis, and nutritive quality response to O 3 was not altered by interspecific competition
-
Nuclear power plants maintenance
International Nuclear Information System (INIS)
Anon.
1988-01-01
Nuclear power plants maintenance now appears as an important factor contributing to the competitivity of nuclea energy. The articles published in this issue describe the way maintenance has been organized in France and how it led to an actual industrial activity developing and providing products and services. An information note about Georges Besse uranium enrichment plant (Eurodif) recalls that maintenance has become a main data not only for power plants but for all nuclear industry installations. (The second part of this dossier will be published in the next issue: vol. 1 January-February 1989) [fr
-
International Nuclear Information System (INIS)
Bogen, J.; Stoelzl, D.
1987-01-01
Growth of world population increases energy demand until the year 2000 and afterwards. Electricity growth rates in industrialized nations are lower after the oil price escalation in 1973 and 1979, and in developing countries grid sizes are often too small for the operation of large LWR plants. This indicates a potential for small and medium-sized power reactors such as the HTR-100 and the HTR-500. These plants can compete with coal fired plants of comparable size. An HTR-500 is even competitive, considering the electricity generating cost of large LWR plants. The special advantages of HTR plants in the small and medium-capacity range are discussed. (orig.)
-
International Nuclear Information System (INIS)
Bogen, J.; Stoelzl, D.
1988-01-01
Growth of world population increases energy demand until the year 2000 and afterwards. Electricity growth rates in industrialized nations are lower after the oil price escalation in 1973 and 1979, and in developing countries grid sizes are often too small for the operation of large LWR plants. This indicates a potential for small and medium-sized power reactors such as the HTR-100 and the HTR-500. These plants can compete with coal fired plants of comparable size. An HTR-500 is even competitive, considering the electricity generating cost of large LWR plants. The special advantages of HTR plants in the small and medium-capacity range are discussed. (orig.)
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Penly comprises 2 production units of 1300 MW each (2600 MW as a whole). The facility generated 18.5 billion kWh in 2009, i.e. 3.57% of the French national power generation and 80% of the energy consumed in the Haute-Normandie region. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Golfech comprises two production units of 1300 MW each (2600 MW as a whole). The facility generated 19.7 billion kWh in 2009, i.e. more than 5% of the French national power generation and 100% of the energy consumed in the Midi-Pyrenees region. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
Do invasive plant species alter soil health?
Invasive species may alter soil characteristics or interact with the soil microbial community to yield a competitive advantage. Our objectives were to determine: if invasive plant species alter soil properties important to soil health; and the long-term effects of invasive plant species on soil pro...
-
Thermal and nuclear power plants: Competitiveness in the new economic conditions
Aminov, R. Z.; Shkret, A. F.; Garievskii, M. V.
2017-05-01
In recent years, the conditions of development and functionality of power generating assets have notably changed. Considering the decline in the price of hydrocarbon fuel on the global market, the efficiency of combined-cycle gas-turbine plants in the European part of Russia is growing in comparison with nuclear power plants. Capital investments in the construction of nuclear power plants have also increased as a result of stiffening the safety requirements. In view of this, there has been an increasing interest in exploration of effective lines of development of generating assets in the European part of Russia, taking consideration of the conditions that may arise in the nearest long-term perspective. In particular, the assessment of comparative efficiency of developing combined-cycle gas-turbine plants (operating on natural gas) in the European part of Russia and nuclear power plants is of academic and practical interest. In this article, we analyze the trends of changes in the regional price of hydrocarbon fuel. Using the prognosis of net-weighted import prices of natural gas in Western European countries—prepared by the International Energy Agency (IEA) and the Energy Research Institute of the Russian Academy of Sciences (ERIRAS)—the prices of natural gas in the European part of Russia equilibrated with import prices of this heat carrier in Western Europe were determined. The methodology of determining the comparative efficiency of combined-cycle gas turbine plants (CCGT) and nuclear power plants (NPP) were described; based on this, the possible development of basic CCGTs and NPPs with regard to the European part of Russia for various scenarios in the prognosis of prices of gaseous fuel in a broad range of change of specific investments in the given generating sources were assessed, and the extents of their comparative efficiency were shown. It was proven that, at specific investments in the construction of new NPPs in the amount of 5000 dollars/kW, nuclear
-
Managers air thoughts on the top competitive issues
International Nuclear Information System (INIS)
Makansi, J.; Swanekamp, R.
1996-01-01
Over 100 powerplant managers and representatives from other industry segments exchanged ideas and opinions at Power magazine's Fifth Powerplant O and M Symposium, ''Managing the Powerplant in a Competitive Environment,'' held June 12--14 in Richmond, VA. Attendees may have represented both utility and independent power facilities, but it was clear from the dialogue that, regardless of ownership, most felt that their plants would have to operate as independent businesses, implicitly if not directly
-
Modelling the effect of environmental factors on resource allocation in mixed plants systems
Gayler, Sebastian; Priesack, Eckart
2010-05-01
In most cases, growth of plants is determined by competition against neighbours for the local resources light, water and nutrients and by defending against herbivores and pathogens. Consequently, it is important for a plant to grow fast without neglecting defence. However, plant internal substrates and energy required to support maintenance, growth and defence are limited and the total demand for these processes cannot be met in most cases. Therefore, allocation of carbohydrates to growth related primary metabolism or to defence related secondary metabolism can be seen as a trade-off between the demand of plants for being competitive against neighbours and for being more resistant against pathogens. A modelling approach is presented which can be used to simulate competition for light, water and nutrients between plant individuals in mixed canopies. The balance of resource allocation between growth processes and synthesis of secondary compounds is modelled by a concept originating from different plant defence hypothesis. The model is used to analyse the impact of environmental factors such as soil water and nitrogen availability, planting density and atmospheric concentration of CO2 on growth of plant individuals within mixed canopies and variations in concentration of carbon-based secondary metabolites in plant tissues.
-
EPR, a GEN 3 Reactor providing a competitive electricity cost
International Nuclear Information System (INIS)
Salhi, Othman
2006-01-01
Since the very beginning of the development of what was to become the EPR, several European entities were involved. The French and German safety authorities expressed that reinforced safety was compulsory. Additional measures were then included to prevent the occurrence of events likely to damage the core, and reduce the possibility of exposure of operating and maintenance personnel. However, not with standing these safety related features resulting from the requirements of the safety authorities, we will focus today on another group of entities that were key players in EPR development: the Utilities. The Utilities voiced their need for a competitive electricity produced and a competitive nuclear reactor. The tradeoff was then to reach both targets in a unique product: a safer and more competitive NPP. Today, the EPR presents features that enable our clients to compete with the cheapest fossil-based electricity production plants. Increased thermal efficiency is obtained both through a higher steam pressure and through careful optimization of the secondary system thermal cycle
-
Natural gas industry competitiveness study
International Nuclear Information System (INIS)
1999-09-01
A national study on the competitiveness of the natural gas industry was undertaken by the BC Oil and Gas Commission in cooperation with, and with the encouragement of the Canadian Association of Petroleum Producers (CAPP). The objective of the study was to compare the cost competitiveness of natural gas exploration , production, gathering and processing in British Columbia to the costs of the same processes in Alberta. The study was carried out by building an 'expected case' for each gas producing area in British Columbia and Alberta by averaging past events in such specific areas as pool sizes, production profiles, loads, drilling success rates, gas compositions, land, drilling, exploration and production/gathering costs, third party production/gathering and processing fees and abandonment costs; by constructing a cash flow model for each case, calculating unit cost, and ranking cases. The report provides the details of the methodology, displays the results of the investigation in graphical form, comments on the results factoring in also labour costs and cost differences due to resource characteristics, identifies some trends such as an increase in the proportion of connections to smaller plants, and provides suggestions for improvements
-
Productive and Unproductive Competition
DEFF Research Database (Denmark)
Guerra, Alice; Luppi, Barbara; Parisi, Francesco
Conventional theories of competition classify contests as being either “productive,” when the competitive efforts generate a surplus for society, or “unproductive,” when competition generates no social surplus and merely distributes already existing resources. These two discrete categories of com...... and socially optimal levels of competition in the full range of intermediate cases, as well as in the extremum cases of destructive and super-productive competition.......Conventional theories of competition classify contests as being either “productive,” when the competitive efforts generate a surplus for society, or “unproductive,” when competition generates no social surplus and merely distributes already existing resources. These two discrete categories...... of competition create a division of real-world situations into analytical categories that fails to recognize the entire spectrum of competitive activities. Taking the existing models of productive and unproductive competition as benchmark idealizations, this paper explores the relationship between the privately...
-
Mixing, entropy and competition
International Nuclear Information System (INIS)
Klimenko, A Y
2012-01-01
Non-traditional thermodynamics, applied to random behaviour associated with turbulence, mixing and competition, is reviewed and analysed. Competitive mixing represents a general framework for the study of generic properties of competitive systems and can be used to model a wide class of non-equilibrium phenomena ranging from turbulent premixed flames and invasion waves to complex competitive systems. We demonstrate consistency of the general principles of competition with thermodynamic description, review and analyse the related entropy concepts and introduce the corresponding competitive H-theorem. A competitive system can be characterized by a thermodynamic quantity—competitive potential—which determines the likely direction of evolution of the system. Contested resources tend to move between systems from lower to higher values of the competitive potential. There is, however, an important difference between conventional thermodynamics and competitive thermodynamics. While conventional thermodynamics is constrained by its zeroth law and is fundamentally transitive, the transitivity of competitive thermodynamics depends on the transitivity of the competition rules. Intransitivities are common in the real world and are responsible for complex behaviour in competitive systems. This work follows ideas and methods that have originated from the analysis of turbulent combustion, but reviews a much broader scope of issues linked to mixing and competition, including thermodynamic characterization of complex competitive systems with self-organization. The approach presented here is interdisciplinary and is addressed to the general educated readers, whereas the mathematical details can be found in the appendices. (comment)
-
Bockstette, S.; Landhäusser, S.; Pinno, B.; Dyck, M. F.
2014-12-01
Reclaimed soils are typically characterized by increased bulk densities, penetration resistances and poor soil structure as well as associated problems with hydrology and aeration. As a result, available rooting space for planted tree seedlings is often restricted to a shallow layer of topsoil, which is usually of higher quality and is cultivated prior to planting. This may hinder the development of healthy root systems, thus drastically increasing the risk for plant stress by limiting access to soil resources such as water, nutrients and oxygen. These problems are exacerbated when herbaceous plants compete for the same resources within this limited root-zone. To understand how limited rooting space affects the physiology of young trees, we experimentally manipulated soil conditions and levels of competition at a reclaimed mine site in central Alberta, Canada. The site was characterized by heavily compacted, fine textured subsoil (~2.0 Mg ha-1), capped with 15 cm of topsoil (~1.5 Mg ha-1). In a replicated study (n=6) half the plots were treated with a subsoil plow to a depth of about 60 cm to increase available rooting spece. Subsequently, trembling aspen (Populus tremuloides Michx.) and smooth brome (Bromus inermis L.) were planted to create four vegetation covers: aspen (a), brome (b), aspen + brome (ab) and control (c) (no vegetation). Various soil properties, including texture, bulk density, penetration resistance and water availability, in conjunction with plant parameters such as root and shoot growth, leaf area development, sap flow, and stomatal conductance have since been monitored, both in-situ and through destructive sampling. Our results indicate that the soil treatment was effective in lowering bulk densities and penetration resistance, while improving moisture retention characteristics. Tree seedling growth and leaf area development were significantly greater without competition, but did not differ between soil treatments. The soil treatment generally
-
Dancing in the Dark: Competition over the "Meaning of Competition"
Metcalfe John Stanley
2009-01-01
Competing concepts of competition provide a sharp divide between theories of economic order and theories of economic transformation. The shift from competition as a state of affairs and competition as a creative process provides the divergence of perspective that is the topic of this paper. We link the Smith Marshall approach of rivalry and open competition to the more modern evolutionary view based on variation cum selection perspectives on innovation and the adaptive role of market processe...
-
Competitive intelligence: An instrument to enhance South Africa’s competitiveness
Directory of Open Access Journals (Sweden)
Wilma Viviers
2014-10-01
Full Text Available The case for Competitive Intelligence (CI as an instrument that can enhance the competitiveness of South African companies and South Africa as a country is strong. Various global competitive rankings measurements have indicated over a number of years the areas in which competitiveness is lacking. Moreover, these rankings have indicated that South Africa has failed to improve its position year on year. The fact that the world is becoming increasingly competitive for South African entities is undisputed. Coupled with a fluctuating exchange rate and the country’s geographical proximity, this poses unique challenges facing South African managers who have to deal with various regulations and legislative matters. In order to create and sustain an effective knowledge economy and to enhance global competitiveness, South Africa however has to put appropriate strategies/measures in place to stimulate, encourage and grow knowledge practices. Competitive Intelligence (CI as a means of making more sense of the competitive business environment and to identify opportunities and risks in time to act upon can be effectively used as a means to enhance competitiveness. Valuable lessons from successful CI practices in the business sector and government can be learnt from elsewhere in the world. CI should be investigated and adapted for South Africa’s business environment. It is therefore the aim of this article to first attempt to describe the role of CI in enhancing competitiveness, specifically in South Africa and secondly, to stimulate thought on how to secure momentum in enhancing CI as an academic field by developing relevant CI courses as well as demonstrating the value of CI to companies in South Africa through research and collaboration between academics and the private and public sectors.
-
Competition law and environmental protection : the Dutch agreement on coal-fired power plants
Kloosterhuis, Erik; Mulder, Machiel
2015-01-01
Agreements between firms to jointly reduce production capacity generally violate competition law, unless specific conditions are met. These conditions imply that the agreements need to realize benefits for consumers that could not otherwise be realised. Together, we call them “efficiency defence.”
-
COMPETITIVENESS THROUGH INFORMATION
Directory of Open Access Journals (Sweden)
Raluca Daniela RIZEA
2013-10-01
Full Text Available Intelligence competitiveness has already started to build its road in the company’s long term strategies. Nonetheless, business executives continue to look for ways to apply information technology strategically to their businesses. Using information managers manage to communicate, to convey their knowledge about markets, competitors, products, services and operations. Even if data and information are all over there are few amounts of managers that realize the importance of them to the success of the business. This article will review competitive forces and competitive information systems strategies for gaining competitive advantages, explain concepts of value chain, value co-opetition (competition and cooperation, and discuss innovation strategy. Co-opetition is a strategy whereby companies cooperate and compete at the same time with their competitors, complementors (i.e. hardware and software businesses, customers, suppliers. The article discuss an important dimension of information system, identifies competitive advantages and enhancing competitive strategies thought information systems.
-
He, Wei-Ming; Li, Jing-Ji; Peng, Pei-Hao
2012-01-01
Climate warming may drive invasions by exotic plants, thereby raising concerns over the risks of invasive plants. However, little is known about how climate warming influences the growth and competitive ability of exotic plants from their home and introduced ranges. We conducted a common garden experiment with an invasive plant Centaurea maculosa and a native plant Poa pratensis, in which a mixture of sand and vermiculite was used as a neutral medium, and contrasted the total biomass, competi...
-
Competition in artifical plant growth media by Trichoderma spp
DEFF Research Database (Denmark)
Sarocco, Sabrina; Lübeck, Mette; Vannacci, Giovanni
of the reason why more biocontrol agents are reaching the market place. A comparative evaluation of life strategies of both the pathogen and its antagonists is required to predict the fate of a biopesticide in agricultural systems.The objectives of this work have been: 1) to screen a collection of Trichoderma......The key to achieve successful, reproducible biological control is the gradual appreciation that knowledge of the ecological interactions taking place in soil and root environments is required to predict the condition under which biological control can be achieved and, indeed, it may be part...... inoculation procedures were employed. Four potential biocontrol agents, all identified as T. harzianum according to the ITS sequences, were selected according to their ability of reducing radish damping off, and were employed in a Competitive Saprophytic Ability (CSA) test, in order to investigate the role...
-
Putting competition into perspective
International Nuclear Information System (INIS)
Jones, L. III.
1993-01-01
This paper examines the current level of competition in the electric industry in the context of the history of the industry and the development of electric markets in other counties. The topics of the paper include competition in the history of the American electric industry, the current state of competition, the competitive situation in Texas, competition in other electric markets, and competitive changes in the US market
-
Risk management: A tool for improving nuclear power plant performance
International Nuclear Information System (INIS)
2001-04-01
This technical document on risk management as a tool for improving nuclear power plant (NPP) operations is part of an ongoing project on management of NPP operations in a competitive environment. The overall objective of this project is to assist the management of operating organizations and NPPs in identifying and implementing appropriate measures to remain competitive in a rapidly changing business environment. Other reports developed through this project have identified overall strategies and techniques that NPP operating organization managers can use to succeed in more competitive energy markets. For example, in IAEA-TECDOC-1123, Strategies for Competitive Nuclear Power Plants, one of the most important strategies identified was integrated risk management. This publication provides a recommended structure for risk management along with examples of how NPP operating organizations are using this tool to help them integrate safety, operational and economic related risks in a changing business environment
-
Weed biocontrol insects reduce native plant recruitment through second-order apparent competition
Dean E. Pearson; Ragan M. Callaway
2008-01-01
Small-mammal seed predation is an important force structuring native-plant communities that may also influence exotic-plant invasions. In the intermountain West, deer mice (Peromyscus maniculatus) are prominent predators of native-plant seeds, but they avoid consuming seeds of certain widespread invasives like spotted knapweed (Centaurea...
-
Dhondt, André A
2010-01-01
1. In studies on the effect of competition in plant communities two terms are used to describe its effects: the absolute reduction in growth of an individual as a consequence of the presence of another one is called intensity, while the relative impact of competition on an individual as a proportion of the impact of the whole environment is called importance. One school of thought is that the role of competition remains constant across productivity gradients, while the other is that it decreases with increasing severity. J.B. Grace (1991. A clarification of the debate between grime and tilman. Functional Ecology, 5, 583-587.) suggested that the apparent contradiction might be solved if we acknowledge that the two schools are discussing different aspects of competition: the intensity of competition might remain constant while its importance declines with increasing severity. 2. There are no studies that compare intensity and importance of competition in bird populations between areas that differ in quality or productivity and hence it is not possible to make predictions how intensity or importance of competition would vary between them. 3. I compared variation in intensity and importance of competition of three demographic variables between five plots that differ strongly in quality for great Parus major L. and blue tit Cyanistes caeruleus (L.). 4. Both intensity and importance of competition are larger in great than in blue tit populations meaning that the effect of competition on demographic variables is stronger in great than in blue tits and that the contribution of competition to variation in these variables is relatively higher in great than in blue tits. 5. Intensity of competition is higher in low quality than in high quality plots for both species, a result not expected from studies in plant communities. 6. Importance of competition varies strongly between plots. It is larger in oak-dominated plots than in mixed deciduous plots. 7. In birds breeding density
-
How light competition between plants affects their response to climate change
Loon, van M.P.; Schieving, F.; Rietkerk, M.; Dekker, S.C.; Sterck, F.J.; Anten, N.P.R.
2014-01-01
How plants respond to climate change is of major concern, as plants will strongly impact future ecosystem functioning, food production and climate. Here, we investigated how vegetation structure and functioning may be influenced by predicted increases in annual temperatures and atmospheric CO2
-
Rusdy, M
2012-01-01
The objectives of this experiment were to determine dry matter yield and competitiveness of alang-alang (Imperata cylindrica) and Guinea grass (Panicum maximum) in intercropping. The experiment was arranged in factorial combinations of four planting proportions, two levels of nitrogen fertilization and three harvesting intervals with three replications. Planting proportions were 0, 33.3, 66.7, and 100% of alang-alang (planting densities of 0, 1, 2 and 3 plants/pot) combined with 100, 66.7, 33...
-
Multinationals and Institutional Competitiveness
DEFF Research Database (Denmark)
Hull Kristensen, Peer; Morgan, Glenn
This article discusses how institutional competitiveness and multinationals are mutually enriching concepts. Seen from the perspective of Multinationals, institutional competitiveness becomes expressed at two levels. At the level of corporate HQs institutional competitiveness proves itself...... competitiveness of Liberal Market Economies and Coordinated Markets Economies under the current competitive regime....
-
Hafezalkotob, Ashkan; Mahmoudi, Reza
2017-09-01
Currently, many socially responsible governments adopt economic incentives and deterrents to manage environmental impacts of electricity suppliers. Considering the Stackelberg leadership of the government, the government's role in the competition of power plants in an electricity market is investigated. A one-population evolutionary game model of power plants is developed to study how their production strategy depends on tariffs levied by the government. We establish that a unique evolutionary stable strategy (ESS) for the population exists. Numerical examples demonstrate that revenue maximization and environment protection policies of the government significantly affect the production ESS of competitive power plants. The results reveal that the government can introduce a green energy source as an ESS of the competitive power plants by imposing appropriate tariffs.
-
Evers, Jochem B; Bastiaans, Lammert
2016-05-01
Suppression of weed growth in a crop canopy can be enhanced by improving crop competitiveness. One way to achieve this is by modifying the crop planting pattern. In this study, we addressed the question to what extent a uniform planting pattern increases the ability of a crop to compete with weed plants for light compared to a random and a row planting pattern, and how this ability relates to crop and weed plant density as well as the relative time of emergence of the weed. To this end, we adopted the functional-structural plant modelling approach which allowed us to explicitly include the 3D spatial configuration of the crop-weed canopy and to simulate intra- and interspecific competition between individual plants for light. Based on results of simulated leaf area development, canopy photosynthesis and biomass growth of the crop, we conclude that differences between planting pattern were small, particularly if compared to the effects of relative time of emergence of the weed, weed density and crop density. Nevertheless, analysis of simulated weed biomass demonstrated that a uniform planting of the crop improved the weed-suppression ability of the crop canopy. Differences in weed suppressiveness between planting patterns were largest with weed emergence before crop emergence, when the suppressive effect of the crop was only marginal. With simultaneous emergence a uniform planting pattern was 8 and 15 % more competitive than a row and a random planting pattern, respectively. When weed emergence occurred after crop emergence, differences between crop planting patterns further decreased as crop canopy closure was reached early on regardless of planting pattern. We furthermore conclude that our modelling approach provides promising avenues to further explore crop-weed interactions and aid in the design of crop management strategies that aim at improving crop competitiveness with weeds.
-
Poelman, E.H.; Broekgaarden, C.; Loon, van J.J.A.; Dicke, M.
2008-01-01
Induction of plant defences by early season herbivores can mediate interspecific herbivore competition. We have investigated plant-mediated competition between three herbivorous insects through studies at different levels of biological integration. We have addressed (i) gene expression; (ii) insect
-
Carus, Jana; Heuner, Maike; Paul, Maike; Schröder, Boris
2017-09-01
Due to increasing pressure on estuarine marshes from sea level rise and river training, there is a growing need to understand how species-environment relationships influence the zonation and growth of tidal marsh vegetation. In the present study, we investigated the distribution and stand characteristics of the two key brackish marsh species Bolboschoenus maritimus and Phragmites australis in the Elbe estuary together with several abiotic habitat factors. We then tested the effect of these habitat factors on plant growth and zonation with generalised linear models (GLMs). Our study provides detailed information on the importance of single habitat factors and their interactions for controlling the distribution patterns and stand characteristics of two key marsh species. Our results suggest that flow velocity is the main factor influencing species distribution and stand characteristics and together with soil-water salinity even affects the inundation tolerance of the two specie investigated here. Additionally, inundation height and duration as well as interspecific competition helped explain the distribution patterns and stand characteristics. By identifying the drivers of marsh zonation and stand characteristics and quantifying their effects, this study provides useful information for evaluating a future contribution of tidal marsh vegetation to ecosystem-based shore protection.
-
Kardol, P.; Bezemer, T.M.; Putten, van der W.H.
2006-01-01
Soil microbes and soil fauna have been assumed to play a key role in interspecific plant competition and successional community development. It has been suggested that plants can influence their performance by changing the composition of their associated soil communities. Such feedback effects may
-
International Nuclear Information System (INIS)
2010-01-01
In less than 20 years, Electricite de France (EDF) has built up a competitive park of 58 nuclear power plants, with no equivalent elsewhere, which represents an installed power of 63.1 GW (85% of EDF's power generation). Inside this nuclear park, the national power generation centre of Cruas-Meysse comprises 4 production units of 900 MW each (3600 MW as a whole). The facility generated 23.587 billion kWh in 2009, i.e. 5% of the French national power generation and 40% of the energy consumed in the Rhone-Alpes region. This brochure presents the life of the power plant under various aspects: power generation, safety priority and culture, maintenance investments, respect of the environment, long-term fuel and wastes management, local economical involvement, transparency and public information, key figures and dates. (J.S.)
-
Energy Technology Data Exchange (ETDEWEB)
Garcia Lopez, A.
2012-07-01
This article aims to outline the logistics chain in the automotive sector and analyze the current situation of the different modes of transport for finished vehicles. Nowadays the Spanish production plants depend on the export, wage levels are very close to the European average and transport costs are winning importance. With the integration of new EU countries with cheaper labor costs and more favorable geographical situation, the distribution logistics become a key variable for the competitiveness of Spanish automotive industry. All data used come from official sources and are as updated as possible. (Author)
-
Wang, Peng; Shu, Meng; Mou, Pu; Weiner, Jacob
2018-03-01
There is little direct evidence for effects of soil heterogeneity and root plasticity on the competitive interactions among plants. In this study, we experimentally examined the impacts of temporal nutrient heterogeneity on root growth and interactions between two plant species with very different rooting strategies: Liquidambar styraciflua (sweet gum), which shows high root plasticity in response to soil nutrient heterogeneity, and Pinus taeda (loblolly pine), a species with less plastic roots. Seedlings of the two species were grown in sandboxes in inter- and intraspecific combinations. Nutrients were applied in a patch either in a stable (slow-release) or in a variable (pulse) manner. Plant aboveground biomass, fine root mass, root allocation between nutrient patch and outside the patch, and root vertical distribution were measured. L. styraciflua grew more aboveground (40% and 27% in stable and variable nutrient treatment, respectively) and fine roots (41% and 8% in stable and variable nutrient treatment, respectively) when competing with P. taeda than when competing with a conspecific individual, but the growth of P. taeda was not changed by competition from L. styraciflua . Temporal variation in patch nutrient level had little effect on the species' competitive interactions. The more flexible L. styraciflua changed its vertical distribution of fine roots in response to competition from P. taeda , growing more roots in deeper soil layers compared to its roots in conspecific competition, leading to niche differentiation between the species, while the fine root distribution of P. taeda remained unchanged across all treatments. Synthesis . L. styraciflua showed greater flexibility in root growth by changing its root vertical distribution and occupying space of not occupied by P. taeda . This flexibility gave L. styraciflua an advantage in interspecific competition.
-
Spatial decoupling of facilitation and competition at the origin of gapped vegetation patterns.
Barbier, Nicolas; Couteron, Pierre; Lefever, René; Deblauwe, Vincent; Lejeune, Olivier
2008-06-01
Spatially periodic vegetation patterns, forming gaps, bands, labyrinths, or spots, are characteristic of arid and semiarid landscapes. Self-organization models can explain this variety of structures within a unified conceptual framework. All these models are based on the interplay of positive and negative effects of plants on soil water, but they can be divided according to whether they assume the interactions to be mediated by water redistribution through runoff/diffusion or by plants' organs. We carried out a multi-proxy approach of the processes operating in a gapped pattern in southwest Niger dominated by a shrub species. Soil moisture within the root layer was monitored in time and space over one month of the rainy season. Soil water recharge displayed no spatial variation with respect to vegetation cover, but the stock half-life under cover was twice that of bare areas. A kernel of facilitation by the aboveground parts of shrubs was parameterized, and soil water half-life was significantly correlated to the cumulated facilitative effects of shrubs. The kernel range was found to be smaller than the canopy radius (81%). This effect of plants on soil water dynamics, probably through a reduction of evaporation by shading, is shown to be a better explanatory variable than potentially relevant soil and topography parameters. The root systems of five individuals of Combretum micranthum G. Don were excavated. Root density data were used as a proxy to parameterize a kernel function of interplant competition. The range of this kernel was larger than the canopy radius (125%). The facilitation-to-competition range ratio, reflecting the above-to-belowground ratio of plant lateral extent, was smaller than 1 (0.64), a result supporting models assuming that patterning may emerge from an adaptation of plant morphology to aridity and shallow soils by means of an extended lateral root system. Moreover, observed soil water gradients had directions opposite to those assumed by
-
Effect of competition on height growth and survival of planted Japanese larch
E. F. McNamara; Irvin C. Reigner
1960-01-01
On the Dilldown Unit of the Delaware-Lehigh Experimental Forest in Pennsylvania, several planting studies have been made with the aim of finding the most economical and practical methods of converting scrub oak areas to productive high-forest types. These studies have already shown the need for site preparation prior to planting. Seedlings planted on prepared areas...
-
International Nuclear Information System (INIS)
Scebba, Francesca; Canaccini, Francesca; Castagna, Antonella; Bender, Juergen; Weigel, Hans-Joachim; Ranieri, Annamaria
2006-01-01
The effects of two-year early season ozone exposure on physiological and biochemical stress response were investigated in model plant communities. Achillea millefolium and Veronica chamaedrys target plants were grown in monocultures and in mixed cultures with Poa pratensis (phytometer) and exposed in open-top chambers over two years for five weeks to charcoal-filtered (CF) air plus 25 nl l -1 O 3 (control) and non-filtered (NF) air plus 50 nl l -1 O 3 . Significant O 3 effects were detected in different physiological and biochemical parameters, evidencing interspecific differences in metabolic stress responses and a strong influence of the competition factor. O 3 induced strong oxidative effects in Achillea irrespective to the different growth modality. Veronica showed less O 3 -induced effects in monoculture than when grown in competition with the phytometer. Poa exhibited a different behaviour against O 3 depending on the species in competition, showing an overall higher sensitivity to O 3 when in mixture with Achillea. - The competition between species modulates the ozone effect in a short-term
-
Energy Technology Data Exchange (ETDEWEB)
Scebba, Francesca [Department of Agricultural Chemistry and Biotechnology, University of Pisa, Via del Borghetto 80, 56124 Pisa (Italy); Canaccini, Francesca [Department of Agricultural Chemistry and Biotechnology, University of Pisa, Via del Borghetto 80, 56124 Pisa (Italy); Castagna, Antonella [Department of Agricultural Chemistry and Biotechnology, University of Pisa, Via del Borghetto 80, 56124 Pisa (Italy); Bender, Juergen [Institute of Agroecology, FAL, Bundesallee 50, 38116 Braunschweig (Germany); Weigel, Hans-Joachim [Institute of Agroecology, FAL, Bundesallee 50, 38116 Braunschweig (Germany); Ranieri, Annamaria [Department of Agricultural Chemistry and Biotechnology, University of Pisa, Via del Borghetto 80, 56124 Pisa (Italy)]. E-mail: aranieri@agr.unipi.it
2006-08-15
The effects of two-year early season ozone exposure on physiological and biochemical stress response were investigated in model plant communities. Achillea millefolium and Veronica chamaedrys target plants were grown in monocultures and in mixed cultures with Poa pratensis (phytometer) and exposed in open-top chambers over two years for five weeks to charcoal-filtered (CF) air plus 25 nl l{sup -1} O{sub 3} (control) and non-filtered (NF) air plus 50 nl l{sup -1} O{sub 3}. Significant O{sub 3} effects were detected in different physiological and biochemical parameters, evidencing interspecific differences in metabolic stress responses and a strong influence of the competition factor. O{sub 3} induced strong oxidative effects in Achillea irrespective to the different growth modality. Veronica showed less O{sub 3}-induced effects in monoculture than when grown in competition with the phytometer. Poa exhibited a different behaviour against O{sub 3} depending on the species in competition, showing an overall higher sensitivity to O{sub 3} when in mixture with Achillea. - The competition between species modulates the ozone effect in a short-term.
-
Bistability of mangrove forests and competition with freshwater plants
Jiang, Jiang; Fuller, Douglas O; Teh, Su Yean; Zhai, Lu; Koh, Hock Lye; DeAngelis, Donald L.; Sternberg, L.D.S.L.
2015-01-01
Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.
-
Directory of Open Access Journals (Sweden)
F Golestani Far
2017-10-01
Full Text Available Introduction Deficiency of water during the plant growth is one of the main factors which reduce the crops production around the world. Drought stress is one of the most important tensions that may occur around the low rainfall, high temperature and wind blowing environments. Plant response to this stress depends on the stage of plant growth and drought intensity. Weeds are unwanted and harmful plants with disturbance in agricultural practices which make increase the cost of crop production and reduce the crop yields. Rye (Secale cereal L. is one of the most important weeds at wheat fields in Iran (Baghestani and Atri, 2003. Low expectations, allelopathic effects and similarity of life cycle and morphology, caused increasing of rye density in winter wheat fields. Water use efficiency (WUE as an important physiological characteristic indicates the ability of plants to water stress. WUE may be affected by climatic and soil or plant factors. In plant communities, competition is one of most important physiological topics (Evans et al, 2003. At Inter-specific competition, weeds interfere to absorbing of light, water and nutrients through the adjacency with crop and so affect the growth and yield of crops. Weeds often compete with crops for soil water and reduce the accessibility of water. Competition between weeds and crops decrease the soil moisture and cause water stress which might decrease the weeds and crops growth. When the supply of water is limited, water drainage overlap areas in soil profile could be occurred relatively fast at early of in the crop life cycle. Materials and Methods In order to study the effects of drought stress on water use efficiency and root dry weight of wheat (Triticum aesativum L. and rye (Secale cereale L. in competition conditions, a pot experiment was conducted in the greenhouse of Agriculture Faculty , University of Birjand in 2012. The experiment was arranged as factorial based on completely randomized design
-
Inter- and intra-specific competition of duckweed under multiple heavy metal contaminated water.
Zhao, Zhao; Shi, Huijuan; Kang, Xianjiang; Liu, Cunqi; Chen, Lingci; Liang, Xiaofei; Jin, Lei
2017-11-01
The influences of intra- and inter-species competition on ecosystems are poorly understood. Lemna aequinoctialis and Spirodela polyrhiza were used to assess the effects of exposure to different concentrations of multiple heavy metals (copper-cadmium-zinc), when the plants were grown in mixed- or mono-culture. Parameters assessed included relative growth rate (RGR), content of chlorophyll, glutathione (GSH), malondialdehyde (MDA), as well as the activity of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD). Inter-specific competition was affected by metal concentration, with results indicating that inter-specific competition significantly affected duckweed growth and metal uptake in different heavy metal exposure conditions. Inter-specific competition increased growth rate of duckweed under high metal concentrations, although when compared with intra-specific competition, it caused no obvious differences under low metal concentrations. The growth of L. aequinoctialis was further increased in mixed culture when exposed to high metal concentrations, with inter-specific competition increasing the content of cadmium and zinc, while decreasing copper content of L. aequinoctialis compared with under intra-specific conditions. Conversely, inter-specific competition increased the content of copper and cadmium of S. polyrhiza, without causing obvious differences in zinc accumulation under high ambient concentrations. Under high metal conditions, inter-specific competition increased antioxidant enzyme activities in duckweed species, increasing resistance to heavy metals. Results show that inter-specific competition makes duckweed develop mechanisms to increase fitness and survival, such as enhancement of antioxidant enzyme activities, rather than limiting metal uptake when exposed to high concentrations of multiple metals. Copyright © 2017 Elsevier B.V. All rights reserved.
-
Martin , J; Chabalier , M; Letourmy , P; Chopart , J.-L; Arhiman , E; Marion , D
2013-01-01
International audience; Differential intra-and inter-row weed management can be a mean to reduce herbicide use in sugarcane. In 2011, a field experiment was conducted in La Reunion Island to assess inter-row weed competition. Four inter-row weed competition treatments for a duration of one (T1), two (T2), three (T3) and four (T4) months after planting were compared in a randomized complete block design with 5 replicates; treatment plots were paired with non-weeded inter-row control plots. All...
-
Breugel, van M.; Breugel, van P.; Jansen, P.A.; Martinez-Ramos, M.; Bongers, F.
2012-01-01
Competition between neighboring plants plays a major role in the population dynamics of tree species in the early phases of humid tropical forest succession. We evaluated the relative importance of above- versus below-ground competition during the first years of old-field succession on soil with low