Civil conflict sensitivity to growing-season drought

OpenAIRE

von Uexkull, Nina; Croicu, Mihai; Fjelde, Hanne; Buhaug, Halvard

2016-01-01

Understanding the conflict potential of drought is critical for dealing effectively with the societal implications of climate change. Using new georeferenced ethnicity and conflict data for Asia and Africa since 1989, we present an actor-oriented analysis of growing-season drought and conflict involvement among ethnic groups. Results from naive models common in previous research suggest that drought generally has little impact. However, context-sensitive models accounting for the groups’ leve...

Reduced early growing season freezing resistance in alpine treeline plants under elevated atmospheric CO2.

NARCIS (Netherlands)

Martin, M.; Gavazov, K.S.; Körner, S.; Rixen, C.

2010-01-01

The frequency of freezing events during the early growing season and the vulnerability to freezing of plants in European high-altitude environments could increase under future atmospheric and climate change. We tested early growing season freezing sensitivity in 10 species, from four plant

Plasticity of maritime pine (Pinus pinaster) wood-forming tissues during a growing season.

Science.gov (United States)

Paiva, J A P; Garnier-Géré, P H; Rodrigues, J C; Alves, A; Santos, S; Graça, J; Le Provost, G; Chaumeil, G; Da Silva-Perez, D; Bosc, A; Fevereiro, P; Plomion, C

2008-01-01

The seasonal effect is the most significant external source of variation affecting vascular cambial activity and the development of newly divided cells, and hence wood properties. Here, the effect of edapho-climatic conditions on the phenotypic and molecular plasticity of differentiating secondary xylem during a growing season was investigated. Wood-forming tissues of maritime pine (Pinus pinaster) were collected from the beginning to the end of the growing season in 2003. Data from examination of fibre morphology, Fourier-transform infrared spectroscopy (FTIR), analytical pyrolysis, and gas chromatography/mass spectrometry (GC/MS) were combined to characterize the samples. Strong variation was observed in response to changes in edapho-climatic conditions. A genomic approach was used to identify genes differentially expressed during this growing season. Out of 3512 studied genes, 19% showed a significant seasonal effect. These genes were clustered into five distinct groups, the largest two representing genes over-expressed in the early- or late-wood-forming tissues, respectively. The other three clusters were characterized by responses to specific edapho-climatic conditions. This work provides new insights into the plasticity of the molecular machinery involved in wood formation, and reveals candidate genes potentially responsible for the phenotypic differences found between early- and late-wood.

Climate change in winter versus the growing-season leads to different effects on soil microbial activity in northern hardwood forests

Science.gov (United States)

Sorensen, P. O.; Templer, P. H.; Finzi, A.

2014-12-01

Mean winter air temperatures have risen by approximately 2.5˚ C per decade over the last fifty years in the northeastern U.S., reducing the maximum depth of winter snowpack by approximately 26 cm over this period and the duration of winter snow cover by 3.6 to 4.2 days per decade. Forest soils in this region are projected to experience a greater number of freeze-thaw cycles and lower minimum winter soil temperatures as the depth and duration of winter snow cover declines in the next century. Climate change is likely to result not only in lower soil temperatures during winter, but also higher soil temperatures during the growing-season. We conducted two complementary experiments to determine how colder soils in winter and warmer soils in the growing-season affect microbial activity in hardwood forests at Harvard Forest, MA and Hubbard Brook Experimental Forest, NH. A combination of removing snow via shoveling and buried heating cables were used to induce freeze-thaw events during winter and to warm soils 5˚C above ambient temperatures during the growing-season. Increasing the depth and duration of soil frost via snow-removal resulted in short-term reductions in soil nitrogen (N) production via microbial proteolytic enzyme activity and net N mineralization following snowmelt, prior to tree leaf-out. Declining mass specific rates of carbon (C) and N mineralization associated with five years of snow removal at Hubbard Brook Experimental Forest may be an indication of microbial physiological adaptation to winter climate change. Freeze-thaw cycles during winter reduced microbial extracellular enzyme activity and the temperature sensitivity of microbial C and N mineralization during the growing-season, potentially offsetting nutrient and soil C losses due to soil warming in the growing-season. Our multiple experimental approaches show that winter climate change is likely to contribute to reduced microbial activity in northern hardwood forests.

Change in Length of Growing Season by State, 1895-2015

Data.gov (United States)

U.S. Environmental Protection Agency — This map shows the total change in length of the growing season, time of first fall frost and time of last spring frost from 1895 to 2015 for each of the contiguous...

Climate change and prolongation of growing season: changes in regional potential for field crop production in Finland

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P. PELTONEN-SAINIO

2008-12-01

Full Text Available Climate change offers new opportunities for Finnish field crop production, which is currently limited by the short growing season. A warmer climate will extend the thermal growing season and the physiologically effective part of it. Winters will also become milder, enabling introduction of winter-sown crops to a greater extent than is possible today. With this study we aim to characterise the likely regional differences in capacity to grow different seed producing crops. Prolongation of the Finnish growing season was estimated using a 0.5º latitude × 0.5º longitude gridded dataset from the Finnish Meteorological Institute. The dataset comprised an average estimate from 19 global climate models of the response of Finnish climate to low (B1 and high (A2 scenarios of greenhouse gas and aerosol emissions for 30-year periods centred on 2025, 2055 and 2085 (Intergovernmental Panel on Climate Change. Growing season temperature sums that suit crop growth and are agronomically feasible in Finland are anticipated to increase by some 140 °Cd by 2025, 300 °Cd by 2055 and 470 °Cd by 2085 in scenario A2, when averaged over regions, and earlier sowing is expected to take place, but not later harvests. Accordingly, the extent of cultivable areas for the commonly grown major and minor crops will increase considerably. Due to the higher base temperature requirement for maize (Zea mays L. growth than for temperate crops, we estimate that silage maize could become a Finnish field crop for the most favourable growing regions only at the end of this century. Winters are getting milder, but it will take almost the whole century until winters such as those that are typical for southern Sweden and Denmark are experienced on a wide scale in Finland. It is possible that introduction of winter-sown crops (cereals and rapeseed will represent major risks due to fluctuating winter conditions, and this could delay their adaptation for many decades. Such risks need to be

Variability of thermal and precipitation conditions in the growing season in Poland in the years 1966-2015

Science.gov (United States)

Tomczyk, Arkadiusz M.; Szyga-Pluta, Katarzyna

2018-03-01

The aim of the study was to identify the thermal and precipitation conditions and their changes in the growing season in Poland in the years 1966-2015. Data on average daily air temperature and daily precipitation totals for 30 stations from the period of 1966-2015 were used. The data were obtained from the collections of the Institute of Meteorology and Water Management—National Research Institute. The growing season was defined as the period of average daily air temperature ≥ 5 °C. The mathematical formulas proposed by Gumiński (1948) were used to determine its start and end dates. In the growing season in Poland in the years 1966-2015, there were more significant changes in the thermal conditions than there were in the precipitation conditions. In terms of long-term trends over the study period, thermal conditions during the growing season are characterised by an increase in mean air temperature, an increase in the sum of air temperatures and an increasing occurrence of seasons classified as above-normal seasons. Precipitation conditions of the growing season show large temporal and spatial variations in precipitation and a predominance of normal conditions. The changes in precipitation were not statistically significant, except for Świnoujście.

Growing up with short stature : Psychosocial consequences of hormone treatment

NARCIS (Netherlands)

Visser-van Balen, J.

2007-01-01

Growing up with short stature. Psychosocial consequences of hormone treatment To enhance height in children with short stature, growth hormone (GH) can be used. In short children without a detectable pathology underlying their short stature, there is no medical rationale for growth hormone

Timing and duration of European larch growing season along altitudinal gradients in the Swiss Alps.

Science.gov (United States)

Moser, Lea; Fonti, Patrick; Büntgen, Ulf; Esper, Jan; Luterbacher, Jürg; Franzen, Julia; Frank, David

2010-02-01

The 2007 European larch (Larix decidua Mill.) growing season was monitored along two elevational transects in the Lötschental valley in the Swiss Alps. Phenological observations and weekly microcore sampling of 28 larch trees were conducted between April and October 2007 at seven study sites regularly spaced from 1350 to 2150 m a.s.l. on northwest- and southeast-facing slopes. The developmental stages of nearly 75,000 individual cells assessed on 1200 thin sections were used to investigate the links between the trees' thermal regimes and growth phases including the beginning and ending of cell enlargement, wall thickening and maturation of the stem wood. Needles appeared approximately 3-4 weeks earlier than stem growth. The duration of ring formation lasted from mid-May to the end of October, with the length of the growing season decreasing along elevation from 137 to 101 days. The onset of the different growing seasons changed by 3-4 days per 100 m elevation; the ending of the growing season, however, appeared minimally related to altitude. If associated with the monitored altitudinal lapse rate of -0.5 degrees C per 100 m, these results translate into a lengthening of the growing season by approximately 7 days per degree Celsius. This study provides new data on the timing and duration of basic growth processes and contributes to quantification of the impacts of global warming on tree growth and productivity.

Estimating the Sensitivity of CLM-Crop to Plant Date and Growing Season Length

Science.gov (United States)

Drewniak, B. A.; Kotamarthi, V. R.

2012-12-01

The Community Land Model (CLM), the land component of the Community Earth System Model (CESM), is designed to estimate the land surface response to climate through simulated vegetation phenology and soil carbon and nitrogen dynamics. Since human influences play a significant role shaping the land surface, the vegetation has been expanded to include agriculture (CLM-Crop) for three crop types: corn, soybean, and spring wheat. CLM-Crop parameters, which define crop phenology, are optimized against AmeriFlux observations of gross primary productivity, net ecosystem exchange, and stored biomass and carbon, for two sites in the U.S. growing corn and soybean. However, there is uncertainty in the measurements and using a small subset of data to determine model parameters makes validation difficult. In order to account for the differences in plant behavior across climate zones, an input dataset is used to define the planting dates and the length of the growing season. In order to improve model performance, and to understand the impacts of uncertainty from the input data, we evaluate the sensitivity of crop productivity and production against planting date and the length of the growing season. First, CLM-Crop is modified to establish plant date based on temperature trends for the previous 10-day period, constrained against the range of observed planting dates. This new climate-based model is compared with the standard fixed plant dates to determine how sensitive the model is to when seeding occurs, and how comparable the climate calculated plant dates are to the fixed dates. Next, the length of the growing season will be revised to account for an alternative climate. Finally, both the climate-based planting and new growth season will be simulated together. Results of the different model runs will be compared to the standard model and to observations to determine the importance of planting date and growing season length on crop productivity and yield.

New England observed and predicted growing season maximum stream/river temperature points

Data.gov (United States)

U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted growing season maximum stream/river temperatures in New England based on a spatial statistical...

Freezing tolerance of wheat cultivars at the early growing season ...

African Journals Online (AJOL)

Cold stress is a worldwide abiotic stress in temperate regions that affects plant development and yield of winter wheat (Triticum aestivum L.) cultivars and other winter crops. This study was conducted to evaluate the effect of freezing stress at the early growing season on survival and also the relationship between resistances ...

Breeding value of the second generation of soybean populations for «growing season» trait

Directory of Open Access Journals (Sweden)

О. З. Щербина

2016-02-01

Full Text Available Purpose. Studying the inheritance of such trait of soybean (Glucine max (L. Merrill as growing season length in F2 and assessing hybrid combinations to identify more quick-ripening phenotypes as compared to parents. Methods. Laboratory test, mathematico-statistical evaluation. Results. In most crossbreeding combinations, when parents differed by growing season length, late ripeness was dominated in F2, in one combination – early ripeness, in two combinations, when parents scarcely differed by growing season length, complementary effect was observed for this index. It was found that ‘Anzhelika’/‘Mageva’ combination generated the highest number of more quick-ripening forms than any of the parents (13.1%, a smaller number was identified in ‘Legenda’/‘Vizhion’ (6.4% and ‘Anzhelika’/‘Gentleman’ (4.0%, and barely noticeable number was observed in ‘Legenda’/‘Yelena’ combination (1.3%. Conclusions. In the following crossbreeding combinations as ‘Legenda’/‘Vizhion’, Legenda’/‘Korado’, ‘Legenda’/‘Ustia’, ‘Legenda’/‘Yelena’, ‘Yug-30’/‘Gentleman’, ‘No. 894’/‘Vizhion’, ‘Anzhelika’/‘Annushka’, ‘No. 894’/‘Annushka’, ‘Legenda’/‘Annushka’, ‘No. 441’/‘Gentleman’, ‘No. 441’/‘Vizhion’, ‘No. 441’/‘Annushka’, ‘Anzheli­ka’/‘Gentleman’ and ‘Anzhelika’/‘Prypiat’ when parents considerably and insignificantly differ by growing season length, late ripeness was dominated in F2. ‘Ustia’/‘Vizhion’ and ‘Yug-30’/‘ Vizhion’ crossbreeding combinations in which parents hardly differ by growing season, complementary effect was observed in F2 for this index.

Analysis of Seasonal Signal in GPS Short-Baseline Time Series

Science.gov (United States)

Wang, Kaihua; Jiang, Weiping; Chen, Hua; An, Xiangdong; Zhou, Xiaohui; Yuan, Peng; Chen, Qusen

2018-04-01

Proper modeling of seasonal signals and their quantitative analysis are of interest in geoscience applications, which are based on position time series of permanent GPS stations. Seasonal signals in GPS short-baseline (paper, to better understand the seasonal signal in GPS short-baseline time series, we adopted and processed six different short-baselines with data span that varies from 2 to 14 years and baseline length that varies from 6 to 1100 m. To avoid seasonal signals that are overwhelmed by noise, each of the station pairs is chosen with significant differences in their height (> 5 m) or type of the monument. For comparison, we also processed an approximately zero baseline with a distance of pass-filtered (BP) noise is valid for approximately 40% of the baseline components, and another 20% of the components can be best modeled by a combination of the first-order Gauss-Markov (FOGM) process plus white noise (WN). The TEM displacements are then modeled by considering the monument height of the building structure beneath the GPS antenna. The median contributions of TEM to the annual amplitude in the vertical direction are 84% and 46% with and without additional parts of the monument, respectively. Obvious annual signals with amplitude > 0.4 mm in the horizontal direction are observed in five short-baselines, and the amplitudes exceed 1 mm in four of them. These horizontal seasonal signals are likely related to the propagation of daily/sub-daily TEM displacement or other signals related to the site environment. Mismodeling of the tropospheric delay may also introduce spurious seasonal signals with annual amplitudes of 5 and 2 mm, respectively, for two short-baselines with elevation differences greater than 100 m. The results suggest that the monument height of the additional part of a typical GPS station should be considered when estimating the TEM displacement and that the tropospheric delay should be modeled cautiously, especially with station pairs with

Tundra shrub effects on growing season energy and carbon dioxide exchange

Science.gov (United States)

Lafleur, Peter M.; Humphreys, Elyn R.

2018-05-01

Increased shrub cover on the Arctic tundra is expected to impact ecosystem-atmosphere exchanges of carbon and energy resulting in feedbacks to the climate system, yet few direct measurements of shrub tundra-atmosphere exchanges are available to corroborate expectations. Here we present energy and carbon dioxide (CO2) fluxes measured using the eddy covariance technique over six growing seasons at three closely located tundra sites in Canada’s Low Arctic. The sites are dominated by the tundra shrub Betula glandulosa, but percent cover varies from 17%–60% and average shrub height ranges from 18–59 cm among sites. The site with greatest percent cover and height had greater snow accumulation, but contrary to some expectations, it had similar late-winter albedo and snow melt dates compared to the other two sites. Immediately after snowmelt latent heat fluxes increased more slowly at this site compared to the others. Yet by the end of the growing season there was little difference in cumulative latent heat flux among the sites, suggesting evapotranspiration was not increased with greater shrub cover. In contrast, lower albedo and less soil thaw contributed to greater summer sensible heat flux at the site with greatest shrub cover, resulting in greater total atmospheric heating. Net ecosystem exchange of CO2 revealed the potential for enhanced carbon cycling rates under greater shrub cover. Spring CO2 emissions were greatest at the site with greatest percent cover of shrubs, as was summer net uptake of CO2. The seasonal net sink for CO2 was ~2 times larger at the site with the greatest shrub cover compared to the site with the least shrub cover. These results largely agree with expectations that the growing season feedback to the atmosphere arising from shrub expansion in the Arctic has the potential to be negative for CO2 fluxes but positive for turbulent energy fluxes.

Environmental Influences on the Growing Season Duration and Ripening of Diverse Miscanthus Germplasm Grown in Six Countries

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Christopher Nunn

2017-05-01

Full Text Available The development of models to predict yield potential and quality of a Miscanthus crop must consider climatic limitations and the duration of growing season. As a biomass crop, yield and quality are impacted by the timing of plant developmental transitions such as flowering and senescence. Growth models are available for the commercially grown clone Miscanthus x giganteus (Mxg, but breeding programs have been working to expand the germplasm available, including development of interspecies hybrids. The aim of this study was to assess the performance of diverse germplasm beyond the range of environments considered suitable for a Miscanthus crop to be grown. To achieve this, six field sites were planted as part of the EU OPTIMISC project in 2012 in a longitudinal gradient from West to East: Wales—Aberystwyth, Netherlands—Wageningen, Stuttgart—Germany, Ukraine—Potash, Turkey—Adana, and Russia—Moscow. Each field trial contained three replicated plots of the same 15 Miscanthus germplasm types. Through the 2014 growing season, phenotypic traits were measured to determine the timing of developmental stages key to ripening; the tradeoff between growth (yield and quality (biomass ash and moisture content. The hottest site (Adana showed an accelerated growing season, with emergence, flowering and senescence occurring before the other sites. However, the highest yields were produced at Potash, where emergence was delayed by frost and the growing season was shortest. Flowering triggers varied with species and only in Mxg was strongly linked to accumulated thermal time. Our results show that a prolonged growing season is not essential to achieve high yields if climatic conditions are favorable and in regions where the growing season is bordered by frost, delaying harvest can improve quality of the harvested biomass.

Growing season carries stronger contributions to albedo dynamics on the Tibetan plateau.

Science.gov (United States)

Tian, Li; Chen, Jiquan; Zhang, Yangjian

2017-01-01

The Tibetan Plateau has experienced higher-than-global-average climate warming in recent decades, resulting in many significant changes in ecosystem structure and function. Among them is albedo, which bridges the causes and consequences of land surface processes and climate. The plateau is covered by snow/ice and vegetation in the non-growing season (nGS) and growing season (GS), respectively. Based on the MODIS products, we investigated snow/ice cover and vegetation greenness in relation to the spatiotemporal changes of albedo on the Tibetan Plateau from 2000 through 2013. A synchronous relationship was found between the change in GSNDVI and GSalbedo over time and across the Tibetan landscapes. We found that the annual average albedo had a decreasing trend, but that the albedo had slightly increased during the nGS and decreased during the GS. Across the landscapes, the nGSalbedo fluctuated in a synchronous pattern with snow/ice cover. Temporally, monthly snow/ice coverage also had a high correspondence with albedo, except in April and October. We detected clear dependencies of albedo on elevation. With the rise in altitude, the nGSalbedo decreased below 4000 m, but increased for elevations of 4500-5500 m. Above 5500 m, the nGSalbedo decreased, which was in accordance with the decreased amount of snow/ice coverage and the increased soil moisture on the plateau. More importantly, the decreasing albedo in the most recent decade appeared to be caused primarily by lowered growing season albedo.

Growing season carries stronger contributions to albedo dynamics on the Tibetan plateau.

Directory of Open Access Journals (Sweden)

Li Tian

Full Text Available The Tibetan Plateau has experienced higher-than-global-average climate warming in recent decades, resulting in many significant changes in ecosystem structure and function. Among them is albedo, which bridges the causes and consequences of land surface processes and climate. The plateau is covered by snow/ice and vegetation in the non-growing season (nGS and growing season (GS, respectively. Based on the MODIS products, we investigated snow/ice cover and vegetation greenness in relation to the spatiotemporal changes of albedo on the Tibetan Plateau from 2000 through 2013. A synchronous relationship was found between the change in GSNDVI and GSalbedo over time and across the Tibetan landscapes. We found that the annual average albedo had a decreasing trend, but that the albedo had slightly increased during the nGS and decreased during the GS. Across the landscapes, the nGSalbedo fluctuated in a synchronous pattern with snow/ice cover. Temporally, monthly snow/ice coverage also had a high correspondence with albedo, except in April and October. We detected clear dependencies of albedo on elevation. With the rise in altitude, the nGSalbedo decreased below 4000 m, but increased for elevations of 4500-5500 m. Above 5500 m, the nGSalbedo decreased, which was in accordance with the decreased amount of snow/ice coverage and the increased soil moisture on the plateau. More importantly, the decreasing albedo in the most recent decade appeared to be caused primarily by lowered growing season albedo.

Complex interaction between genotypes and growing seasons of carioca common bean in Goiás/Distrito Federal

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Helton Santos Pereira

2011-01-01

Full Text Available The objectives of this study were to assess the importance of the complex interaction between common beangenotypes and growing seasons in the state of Goiás and the Distrito Federal and verify the need for evaluation and indication ofcultivars for each season. Yield data of 16 genotypes in 16 trials conducted in two growing seasons (winter and rainy were used. Thecoefficient of determination was estimated in the analyses of variance with decomposition of the genotype x environment interaction.The complex percentage of the interaction was estimated and the Spearman correlation between seasons. Differences were detectedbetween seasons and presence of genotype - season (GS interaction, with greater significance than the other double interactionswith genotypes. The correlations indicated a predominantly complex GS interaction. This predominantly complex nature of the GSinteraction calls for an assessment of the genotypes in both seasons, which may however identify cultivars with general adaptation.

Trend Analysis of Droughts during Crop Growing Seasons of Nigeria

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Mohammed Sanusi Shiru

2018-03-01

Full Text Available This study assesses the impacts of recent climate changes on drought-affected areas and the occurrence of droughts during different cropping seasons of Nigeria using the standardized precipitation evapotranspiration index (SPEI. The crop growing seasons are considered because the droughts for those periods are more destructive to national agricultural production. The Mann–Kendall test and binary logistic regression were used to quantify the trends in drought-affected areas and the occurrence of crop droughts with different areal extents, respectively. Gauge-based gridded rainfall and temperature data for the period 1961–2010 with spatial resolutions of 0.5° were used. Results showed an increase in the areal extent of droughts during some of the cropping seasons. The occurrences of droughts, particularly moderate droughts with smaller areal extents, were found to increase for all of the seasons. The SPEI values calculated decreased mostly in the regions where rainfall was decreasing. That is, the recent changes in climate were responsible for the increase in the occurrences of droughts with smaller areal extents. These trends in climate indicate that the occurrence of larger areal extent droughts may happen more frequently in Nigeria in the future.

Variations of Mercury Concentrations in American Beech Foliage over a Growing Season

Science.gov (United States)

Stinson, I.; Tsui, M. T. K.; Chow, A. T.

2017-12-01

Accumulation of atmospheric gaseous mercury (Hg) in foliage is well known, however, a small fraction of Hg always exists as highly bioavailable methylmercury (MeHg) in foliage but the source of MeHg in foliage is unknown. Recent studies suggested in-vivo Hg methylation in foliage while others suggested external inputs (e.g., precipitation) as sources of MeHg in foliage. This study assesses the accumulation of total Hg and MeHg within the foliage of a small sample set of American Beech trees, one of the common tree species in the east coast and the study site is located within the campus of University of North Carolina - Greensboro, over the growing season in 2017 (spring, summer, and fall). In addition, this study evaluates the Hg concentrations in foliage as related to other physiological parameters (e.g., stomatal density, leaf area, chlorophyll, and carbon/nitrogen content) and the changes in environmental characteristics (e.g., sunlight) over the growing season. For this investigation, five American Beech trees with varying characteristics (height, age, and location) were selected. On a biweekly basis, starting late April 2017, foliage samples were collected and composited from different positions on each tree. For the samples processed to date, our results indicate that total Hg accumulation is occurring for all five trees with an initial mean value of 5.79 ng/g, increasing to a mean value of 13.9 ng/g over a ten-week period. Coincidentally, there has been a similar increase in chlorophyll (a+b) concentrations for the foliage, and there is a strong, positive relationship between chlorophyll and total-Hg concentrations. However, we found no relationships between total Hg concentrations and stomatal density of foliage or carbon/nitrogen content. This study is still ongoing and will continue through the end of the growing season in 2017. Additionally, from the same sample sets, besides total Hg analysis and other ancillary parameters in foliage, MeHg analysis

Changes in the thermal growing season in Nordic countries during the past century and prospects for the future

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Timothy R. Carter

1998-01-01

Full Text Available The start, end, duration and intensity of the thermal growing season (the period with mean daily temperatures exceeding 5°C during the past century (1890-1995 was analysed at nine sites in the Nordic region. Statistical comparisons were made between three adjacent 35-year periods. The results indicate that the growing season lengthened considerably at all sites between 1891-1925 and 1926-1960. Lengthening has continued at a slower rate up to the present at the eight Fennoscandian sites but not at the Icelandic site. In contrast, the intensity of the growing season, expressed by effective temperature sum above 5°C, which increased at all sites between the first two periods, has decreased slightly at all locations except Turku in recent decades. Under three scenarios, representing the range of estimated greenhouse gas-induced warming by the 2050s, the growing season is expected to lengthen at all sites. For a “Central” scenario, the greatest lengthening is computed for southern and western Scandinavia (7-8 weeks with smaller changes in Finland (4 weeks and Iceland (3 weeks. With a lengthening growing season during the past century in Fennoscandia, there are likely to have been impacts on natural and managed ecosystems. Some evidence of recent biotic and abiotic effects already exists, but other indicators of long-term change remain to be analysed.

Changes in the thermal growing season in Nordic countries during the past century and prospects for the future

Directory of Open Access Journals (Sweden)

T.R. CARTER

2008-12-01

Full Text Available The start, end, duration and intensity of the thermal growing season (the period with mean daily temperatures exceeding 5°C during the past century (1890-1995 was analysed at nine sites in the Nordic region. Statistical comparisons were made between three adjacent 35-year periods. The results indicate that the growing season lengthened considerably at all sites between 1891-1925 and 1926-1960. Lengthening has continued at a slower rate up to the present at the eight Fennoscandian sites but not at the Icelandic site. In contrast, the intensity of the growing season, expressed by effective temperature sum above 5°C, which increased at all sites between the first two periods, has decreased slightly at all locations except Turku in recent decades. Under three scenarios, representing the range of estimated greenhouse gas-induced warming by the 2050s, the growing season is expected to lengthen at all sites. For a "Central" scenario, the greatest lengthening is computed for southern and western Scandinavia (7-8 weeks with smaller changes in Finland (4 weeks and Iceland (3 weeks. With a lengthening growing season during the past century in Fennoscandia, there are likely to have been impacts on natural and managed ecosystems. Some evidence of recent biotic and abiotic effects already exists, but other indicators of long-term change remain to be analysed. ;

Effects of plant cover on soil N mineralization during the growing season in a sandy soil

Science.gov (United States)

Yao, Y.; Shao, M.; Wei, X.; Fu, X.

2017-12-01

Soil nitrogen (N) mineralization and its availability plays a vital role in regulating ecosystem productivity and C cycling, particularly in semiarid and desertified ecosystems. To determine the effect of plant cover on N turnover in a sandy soil ecosystem, we measured soil N mineralization and inorganic N pools in soil solution during growing season in a sandy soil covered with various plant species (Artemisia desertorum, Salix psammophila, and Caragana korshinskii). A bare sandy soil without any plant was selected as control. Inorganic N pools and N mineralization rates decreased overtime during the growing season, and were not affected by soil depth in bare land soils, but were significantly higher at the 0-10 cm layer than those at the 10-20 cm soil layer under any plant species. Soil inorganic N pool was dominated by ammonium, and N mineralization was dominated by nitrification regardless of soil depth and plant cover. Soils under C. korshinskii have significant higher inorganic N pools and N mineralization rate than soils under bare land and A. desertorum and S. psammophila, and the effects of plant cover were greater at the 0-10 cm soil layer than at the 10-20 cm layer. The effects of C. korshinskii on soil inorganic N pools and mineralization rate varied with the stage of growing season, with greater effects on N pools in the middle growing season, and greater effects on mineralization rate at the last half of the growing season. The results from this study indicate that introduction of C. korshinskii has the potential to increase soil N turnover and availability in sandy soils, and thus to decrease N limitation. Caragana korshinskii is therefore recommend for the remediation of the desertified land.

Underestimated effects of low temperature during early growing season on carbon sequestration of a subtropical coniferous plantation

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W.-J. Zhang

2011-06-01

Full Text Available The impact of air temperature in early growing season on the carbon sequestration of a subtropical coniferous plantation was discussed through analyzing the eddy flux observations at Qianyanzhou (QYZ site in southern China from 2003 to 2008. This site experienced two cold early growing seasons (with temperature anomalies of 2–5 °C in 2005 and 2008, and a severe summer drought in 2003.
Results indicated that the low air temperature from January to March was the major factor controlling the inter-annual variations in net carbon uptake at this site, rather than the previously thought summer drought. The accumulative air temperature from January to February showed high correlation (R²=0.970, p<0.001 with the annual net ecosystem production (NEP. This was due to the controls of early-month temperature on the plant phenology developing and the growing season length at this subtropical site. The cold spring greatly shortened the growing season length and therefore reduced the carbon uptake period. The eddy flux observations showed a carbon loss of 4.04 g C m⁻² per growing-season day at this coniferous forest site. On the other hand, the summer drought also reduced the net carbon uptake strength because the photosynthesis was more sensitive to water deficit stress than the ecosystem respiration. However, the impact of summer drought occurred within a relatively shorter period and the carbon sequestration went back to the normal level once the drought was relieved.

317/319 Phytoremediation site monitoring report - 2009 growing season : final report.

Energy Technology Data Exchange (ETDEWEB)

Negri, C .N.; Benda, P. L.; Gopalakrishnan, G.; Energy Systems

2010-02-10

In 1999, Argonne National Laboratory (Argonne) designed and installed a series of engineered plantings consisting of a vegetative cover system and approximately 800 hybrid poplars and willows rooting at various predetermined depths. The plants were installed using various methods including Applied Natural Science's TreeWell{reg_sign} system. The goal of the installation was to protect downgradient surface and groundwater by intercepting the contaminated groundwater with the tree roots, removing moisture from the upgradient soil area, reducing water infiltration, preventing soil erosion, degrading and/or transpiring the residual volatile organic compounds (VOCs), and removing tritium from the subsoil and groundwater. This report presents the results of the monitoring activities conducted by Argonne's Energy Systems (ES) Division in the growing season of 2009. Monitoring of the planted trees began soon after the trees were installed in 1999 and has been conducted every summer since then. As the trees grew and consolidated their growth into the contaminated soil and groundwater, their exposure to the contaminants was progressively shown through tissue sampling. During the 2009 sampling campaign, VOC concentrations found in the French Drain area were in general consistent with or slightly lower than the 2008 results. Additionally, closely repeated, stand wide analyses showed contaminant fluctuations that may indicate short-term contaminant depletion in the area of interest of roots. This data will be useful to determine short-term removal rate by the trees. As in previous years, levels in the Hydraulic Control Area were close to background levels except for a few exceptions.

Spatial and seasonal patterns of European short-snouted seahorse ...

African Journals Online (AJOL)

North-East Atlantic), determining the spatial and seasonal abundance, population structure and physical appearance of European short-snouted seahorse Hippocampus hippocampus. Animals were surveyed off Gran Canaria Island in two ...

THE INFLUENCE OF WEATHER CONDITIONS OF EASTERN POLAND ON SWEET CORN YIELDS AND LENGTH OF GROWING SEASON

Directory of Open Access Journals (Sweden)

Robert Rosa

2016-09-01

Full Text Available The aim of the study was to determine the effect of weather components (air temperature, precipitation on the growth, yield and the length of the growing season of sweet corn cultivated in eastern Poland. The results come from a field experiment conducted in 2006–2011. Weather conditions in the successive years of the study significantly modified the yield of ears, weight and number of formatted ears, high of plants and the length of the growing season of sweet corn. Good yielding of sweet corn favoured years with moderate air temperatures in July and uniform distribution of precipitation during the growing season. The highest yield of ears was found in 2011, the lowest in the very difficult in terms of weather 2006. The shortest growing season was characterized corn grown in the years 2006 and 2010 with the high air temperatures in July and August, the longest in the years 2009 and 2011, in which the temperatures in the period June-August were the lowest of all the years of research. Irrespective of the year of study, cv ‘Sheba F1’ was formatted eras with higher weight than cv ‘Sweet Nugget F1’.

USDA Cranberry Entomology Laboratory (CEL) research priorities in the 2016 growing season

Science.gov (United States)

Research priorities during the 2016 growing season will be focused on 1) discovery and screening of native WI nematodes as bio-control agents, and 2) continued refinement of the drone-deployed mating disruption system. Extramural funding will be needed for both, and the degree of funding will dictat...

Changing water availability during the African maize-growing season, 1979–2010

International Nuclear Information System (INIS)

Estes, Lyndon D; Chaney, Nathaniel W; Herrera-Estrada, Julio; Sheffield, Justin; Caylor, Kelly K; Wood, Eric F

2014-01-01

Understanding how global change is impacting African agriculture requires a full physical accounting of water supply and demand, but accurate, gridded data on key drivers (e.g., humidity) are generally unavailable. We used a new bias-corrected meteorological dataset to analyze changes in precipitation (supply), potential evapotranspiration (E p , demand), and water availability (expressed as the ratio P/E p ) in 20 countries (focusing on their maize-growing regions and seasons), between 1979 and 2010, and the factors driving changes in E p . Maize-growing areas in Southern Africa, particularly South Africa, benefitted from increased water availability due in large part to demand declines driven primarily by declining net radiation, increasing vapor pressure, and falling temperatures (with no effect from changing windspeed), with smaller increases in supply. Sahelian zone countries in West Africa, as well as Ethiopia in East Africa, had strong increases in availability driven primarily by rainfall rebounding from the long-term Sahelian droughts, with little change or small reductions in demand. However, intra-seasonal supply variability generally increased in West and East Africa. Across all three regions, declining net radiation contributed downwards pressure on demand, generally over-riding upwards pressure caused by increasing temperatures, the regional effects of which were largest in East Africa. A small number of countries, mostly in or near East Africa (Tanzania and Malawi) experienced declines in water availability primarily due to decreased rainfall, but exacerbated by increasing demand. Much of the reduced water availability in East Africa occurred during the more sensitive middle part of the maize-growing season, suggesting negative consequences for maize production. (paper)

Long-term enhanced winter soil frost alters growing season CO2 fluxes through its impact on vegetation development in a boreal peatland.

Science.gov (United States)

Zhao, Junbin; Peichl, Matthias; Nilsson, Mats B

2017-08-01

At high latitudes, winter climate change alters snow cover and, consequently, may cause a sustained change in soil frost dynamics. Altered winter soil conditions could influence the ecosystem exchange of carbon dioxide (CO 2 ) and, in turn, provide feedbacks to ongoing climate change. To investigate the mechanisms that modify the peatland CO 2 exchange in response to altered winter soil frost, we conducted a snow exclusion experiment to enhance winter soil frost and to evaluate its short-term (1-3 years) and long-term (11 years) effects on CO 2 fluxes during subsequent growing seasons in a boreal peatland. In the first 3 years after initiating the treatment, no significant effects were observed on either gross primary production (GPP) or ecosystem respiration (ER). However, after 11 years, the temperature sensitivity of ER was reduced in the treatment plots relative to the control, resulting in an overall lower ER in the former. Furthermore, early growing season GPP was also lower in the treatment plots than in the controls during periods with photosynthetic photon flux density (PPFD) ≥800 μmol m -2  s -1 , corresponding to lower sedge leaf biomass in the treatment plots during the same period. During the peak growing season, a higher GPP was observed in the treatment plots under the low light condition (i.e. PPFD 400 μmol m -2  s -1 ) compared to the control. As Sphagnum moss maximizes photosynthesis at low light levels, this GPP difference between the plots may have been due to greater moss photosynthesis, as indicated by greater moss biomass production, in the treatment plots relative to the controls. Our study highlights the different responses to enhanced winter soil frost among plant functional types which regulate CO 2 fluxes, suggesting that winter climate change could considerably alter the growing season CO 2 exchange in boreal peatlands through its effect on vegetation development. © 2017 John Wiley & Sons Ltd.

Contribution of black spruce (Picea mariana) transpiration to growing season evapotranspiration in a subarctic discontinuous permafrost peatland complex

Science.gov (United States)

Helbig, M.; Warren, R. K.; Pappas, C.; Sonnentag, O.; Berg, A. A.; Chasmer, L.; Baltzer, J. L.; Quinton, W. L.; Patankar, R.

2016-12-01

Partitioning the components of evapotranspiration (ET), evaporation and transpiration, has been increasingly important for the better understanding and modeling of carbon, water, and energy dynamics, and for reliable water resources quantification and management. However, disentangling its individual processes remains highly uncertain. Here, we quantify the contribution of black spruce transpiration, the dominant overstory, to ET of a boreal forest-wetland landscape in the southern Taiga Plains. In these ecosystems, thawing permafrost induces rapid landscape change, whereby permafrost-supported forested plateaus are transformed into bogs or fens (wetlands), resulting in tree mortality. Using historical and projected rates of forest-wetland changes, we assess how the contribution of black spruce transpiration to landscape ET might be altered with continued permafrost loss, and quantify the resulting water balance changes. We use two nested eddy covariance flux towers and a footprint model to quantify ET over the entire landscape. Sap flux density of black spruce is measured using the heat ratio method during the 2013 (n=22) and 2014 (n=3) growing seasons, and is used to estimate tree-level transpiration. Allometric relations between tree height, diameter at breast height and sapwood area are derived to upscale tree-level transpiration to overstory transpiration within the eddy covariance footprint. Black spruce transpiration accounts for <10% of total landscape ET. The largest daily contribution of overstory transpiration to landscape ET is observed shortly after the landscape becomes snow-free, continually decreasing throughout the progression of the growing season. Total transpiration is notably lower in 2014 (2.34 mm) than 2013 (2.83 mm) over the same 40-day period, corresponding to 3% of cumulative landscape ET in both years. This difference is likely due to the antecedent moisture conditions, where the 2014 growing season was proceeded by lower than average

Growing Season Definition and Use in Wetland Delineation: A Literature Review

Science.gov (United States)

2010-08-01

obvious bud set) unreliable indicators of the end of the growing season. For example, drought can induce premature leaf abscission, and woody plant...as well as privet (Ligustrum japonicum), loblolly pine ( Pinus taeda), and yellow poplar (Liriodendron tulipifera). The lack of water uptake was...the effects of four flooding/drying regimes on shortleaf pine ( Pinus echinata), loblolly pine, and pond pine ( Pinus serotina). The expected result

Nitrogen fertilization and yield formation of potato during a short growing period

Directory of Open Access Journals (Sweden)

L. MUSTONEN

2008-12-01

Full Text Available The effects various rates of nitrogen application on accumulation of dry matter and nitrogen in potato (Solanum tuberosum L. were studied during a short growing period of 140–180 days, at MTT Agrifood Research Finland in 2000–2001. The treatments were 0, 60 and 120 kg N ha-1 and the potato cultivars tested were Van Gogh and Nicola. Four successive harvests were made during the course of the experiment to monitor changes in the accumulation of dry matter and nitrogen over the season. Applications of nitrogen substantially increased haulm dry matter accumulation and to an even greater extent their nitrogen contents. The highest dry matter values were generally registered at 120 kg N ha-1. Dry matter and nitrogen content of haulms started to decline during the later part of season and most nitrogen was relocated to tubers. The results suggest that an application of only 60 kg N ha-1 was sufficient to promote rapid canopy development and there were only small reductions in dry matter and nitrogen accumulation until late in the season when the canopy started to senesce as nitrogen supply diminished. Tuber yield, plant dry matter and nitrogen accumulation at maturity were related to crop nitrogen supply. Although application of the high rate, 120 N kg ha-1, resulted in a significant increase in dry matter accumulation, this was not reflected in the profit because the higher nitrogen application reduced dry matter content of tubers by 2.6% in 2000 and by 1.1% in 2001 relative to the use of 60 kg N ha-1. Apparent fertilizer nitrogen recovery values on a whole plant basis ranged from 53 to 75%. The proportion of fertilizer recovered in tubers clearly declined with increase in nitrogen supply.;

Crop water stress maps for an entire growing season from visible and thermal UAV imagery

DEFF Research Database (Denmark)

Hoffmann, Helene; Jensen, Rasmus; Thomsen, Anton

2016-01-01

This study investigates whether a water deficit index (WDI) based on imagery from unmanned aerial vehicles (UAVs) can provide accurate crop water stress maps at different growth stages of barley and in differing weather situations. Data from both the early and late growing season are included...... to investigate whether the WDI has the unique potential to be applicable both when the land surface is partly composed of bare soil and when crops on the land surface are senescing. The WDI differs from the more commonly applied crop water stress index (CWSI) in that it uses both a spectral vegetation index (VI...... season because at this stage the remote sensing data represent crop water availability to a greater extent than they do in the early growing season, and because the WDI accounts for areas of ripe crops that no longer have the same need for irrigation. WDI maps can potentially serve as water stress maps...

Growing Degree Vegetation Production Index (GDVPI): A Novel and Data-Driven Approach to Delimit Season Cycles

Science.gov (United States)

Graham, W. D.; Spruce, J.; Ross, K. W.; Gasser, J.; Grulke, N.

2014-12-01

Growing Degree Vegetation Production Index (GDVPI) is a parametric approach to delimiting vegetation seasonal growth and decline cycles using incremental growing degree days (GDD), and NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) 8-day composite cumulative integral data. We obtain a specific location's daily minimum and maximum temperatures from the nearest National Oceanic and Atmospheric Administration (NOAA) weather stations posted on the National Climate Data Center (NCDC) Climate Data Online (CDO) archive and compute GDD. The date range for this study is January 1, 2000 through December 31, 2012. We employ a novel process, a repeating logistic product (RLP), to compensate for short-term weather variability and data drops from the recording stations and fit a curve to the median daily GDD values, adjusting for asymmetry, amplitude, and phase shift that minimize the sum of squared errors when comparing the observed and predicted GDD. The resulting curve, here referred to as the surrogate GDD, is the time-temperature phasing parameter used to convert Cartesian NDVI values into polar coordinate pairs, multiplying the NDVI values as the radial by the cosine and sine of the surrogate GDD as the angular. Depending on the vegetation type and the original NDVI curve, the polar NDVI curve may be nearly circular, kidney-shaped, or pear-shaped in the case of conifers, deciduous, or agriculture, respectively. We examine the points of tangency about the polar coordinate NDVI curve, identifying values of 1, 0, -1, or infinity, as each of these represent natural inflection points. Lines connecting the origin to each tangent point illustrate and quantify the parametrically segmentation of the growing season based on the GDD and NDVI ostensible dependency. Furthermore, the area contained by each segment represents the apparent vegetation production. A particular benefit is that the inflection points are determined

Growing season temperature and precipitation variability and extremes in the U.S. Corn Belt from 1981 to 2012

Science.gov (United States)

Dai, S.; Shulski, M.

2013-12-01

Climate warming and changes in rainfall patterns and increases in extreme events are resulting in higher risks of crop failures. A greater sense of urgency has been induced to understand the impacts of past climate on crop production in the U.S. As one of the most predominant sources of feed grains, corn is also the main source of U.S. ethanol. In the U.S. Corn Belt, region-scale evaluation on temperature and precipitation variability and extremes during the growing season is not well-documented yet. This study is part of the USDA-funded project 'Useful to Usable: Transforming climate variability and change information for cereal crop producers'. The overall goal of our work is to study the characteristics of average growing season conditions and changes in growing season temperature- and precipitation-based indices that are closely correlated with corn grain yield in the U.S. Corn Belt. The research area is the twelve major Corn Belt states, including IL, IN, IA, KS, MI, MN, MO, NE, OH, SD, ND, and WI. Climate data during 1981-2010 from 132 meteorological stations (elevation ranges from 122 m to 1,202 m) are used in this study, including daily minimum, maximum, and mean temperature, and daily precipitation. From 1981 to 2012, beginning date (BD), ending date (ED), and growing season length (GSL) in the climatological corn growing season are studied. Especially, during the agronomic corn growing season, from Apr to Oct, temperature- and precipitation-based indices are analyzed. The temperature-based indices include: number of days with daily mean temperature below 10°C, number of days with daily mean temperature above 30°C, the sum of growing degree days (GDD) between 10°C to 30°C (GDD10,30, growth range for corn), the sum of growing degree days above 30°C (GDD30+, exposure to harmful warming for corn), the sum of growing degree days between 0°C and 44°C (GDD0,44, survival range limits for corn), the sum of growing degree days between 5°C and 35°C (GDD5

New England observed and predicted Julian day of maximum growing season stream/river temperature points

Data.gov (United States)

U.S. Environmental Protection Agency — The shapefile contains points with associated observed and predicted Julian day of maximum growing season stream/river temperatures in New England based on a spatial...

Phenology Shifts at Start vs. End of Growing Season in Temperate Vegetation Over the Northern Hemisphere for the Period 1982-2008

Science.gov (United States)

Jeong, Su-Jong; Ho, Chang-Hoi; Gim, Hyeon-Ju; Brown, Molley E.

2011-01-01

Changes in vegetative growing seasons are dominant indicators of the dynamic response of ecosystems to climate change. Therefore, knowledge of growing seasons over the past decades is essential to predict ecosystem changes. In this study, the long-term changes in the growing seasons of temperate vegetation over the Northern Hemisphere were examined by analyzing satellite-measured normalized difference vegetation index and reanalysis temperature during 1982 2008. Results showed that the length of the growing season (LOS) increased over the analysis period; however, the role of changes at the start of the growing season (SOS) and at the end of the growing season (EOS) differed depending on the time period. On a hemispheric scale, SOS advanced by 5.2 days in the early period (1982-1999) but advanced by only 0.2 days in the later period (2000-2008). EOS was delayed by 4.3 days in the early period, and it was further delayed by another 2.3 days in the later period. The difference between SOS and EOS in the later period was due to less warming during the preseason (January-April) before SOS compared with the magnitude of warming in the preseason (June September) before EOS. At a regional scale, delayed EOS in later periods was shown. In North America, EOS was delayed by 8.1 days in the early period and delayed by another 1.3 days in the later period. In Europe, the delayed EOS by 8.2 days was more significant than the advanced SOS by 3.2 days in the later period. However, in East Asia, the overall increase in LOS during the early period was weakened in the later period. Admitting regional heterogeneity, changes in hemispheric features suggest that the longer-lasting vegetation growth in recent decades can be attributed to extended leaf senescence in autumn rather than earlier spring leaf-out. Keywords: climate change, growing season, NDVI (normalized difference vegetation index), Northern Hemisphere, phenology,

Early and late seasonal carbon sequestration and allocation in larch trees growing on permafrost in Central Siberia

Science.gov (United States)

Masyagina, Oxana; Prokushkin, Anatoly; Kirdyanov, Alexander; Artyukhov, Aleksey; Udalova, Tatiana; Senchenkov, Sergey; Rublev, Aleksey

2014-05-01

Despite large geographic extent of deciduous conifer species Larix gmelinii, its seasonal photosynthetic activity and translocation of photoassimilated carbon within a tree remain poorly studied. To get better insight into productivity of larch trees growing on permafrost soils in Siberian larch biome we aimed to analyze dynamics of foliage parameters (i.e. leaf area, biomass, %N, %P etc.), seasonal dynamics of photosynthetic activity and apply whole tree labeling by 13CO2, which is powerful and effective tool for tracing newly developed assimilates translocation to tissues and organs of a tree (Kagawa et al., 2006; Keel et al., 2012). Experimental plot has been established in mature 105 year-old larch stand located within the continuous permafrost area near Tura settlement (Central Siberia, 64o17'13" N, 100o11'55" E, 148 m a.s.l.). Trees selected for experiments represented mean tree of the stand. Measurements of seasonal photosynthetic activity and foliar biomass sampling were arranged from early growing season (June 8, 2013) until yellowing and senescence of needles on September 17, 2013. Labeling by 13C in whole tree chamber was conducted by three pulses ([CO2]max ≤ 2,500 ppmv, 13CO2 (30% v/v)) at the early (June) and late (August) phase of growing season for different trees in 3 replicates each time. Both early season and late season labeling experiments demonstrated high rate of 13CO2 assimilation and respective enrichment of needle tissues by 13C: δ13C increased from -28.7 up to +670‰ just after labeling. However, there was distinct post-labeling dynamics of needle δ13C among two seasonal experiments. At the early season 13C depletion in labeled needles was slower, and δ13C approached after 40 days ca. +110 ‰ and remained constant till senescence. In the late season (August) needles were losing labeled C with much faster rate and approached only +1.5 ‰ upon senescence (28 days exposition). These findings suggest that in early season ca. 20% of

Effects of urban green infrastructure (UGI) on local outdoor microclimate during the growing season

NARCIS (Netherlands)

Wang, Yafei; Bakker, Frank; Groot, de Rudolf; Wörtche, Heinrich; Leemans, Rik

2015-01-01

This study analyzed how the variations of plant area index (PAI) and weather conditions alter the influence of urban green infrastructure (UGI) on microclimate. To observe how diverse UGIs affect the ambient microclimate through the seasons, microclimatic data were measured during the growing

Snowmelt timing, phenology, and growing season length in conifer forests of Crater Lake National Park, USA

Science.gov (United States)

O'Leary, Donal S.; Kellermann, Jherime L.; Wayne, Chris

2018-02-01

Anthropogenic climate change is having significant impacts on montane and high-elevation areas globally. Warmer winter temperatures are driving reduced snowpack in the western USA with broad potential impacts on ecosystem dynamics of particular concern for protected areas. Vegetation phenology is a sensitive indicator of ecological response to climate change and is associated with snowmelt timing. Human monitoring of climate impacts can be resource prohibitive for land management agencies, whereas remotely sensed phenology observations are freely available at a range of spatiotemporal scales. Little work has been done in regions dominated by evergreen conifer cover, which represents many mountain regions at temperate latitudes. We used moderate resolution imaging spectroradiometer (MODIS) data to assess the influence of snowmelt timing and elevation on five phenology metrics (green up, maximum greenness, senescence, dormancy, and growing season length) within Crater Lake National Park, Oregon, USA from 2001 to 2012. Earlier annual mean snowmelt timing was significantly correlated with earlier onset of green up at the landscape scale. Snowmelt timing and elevation have significant explanatory power for phenology, though with high variability. Elevation has a moderate control on early season indicators such as snowmelt timing and green up and less on late-season variables such as senescence and growing season length. PCA results show that early season indicators and late season indicators vary independently. These results have important implications for ecosystem dynamics, management, and conservation, particularly of species such as whitebark pine ( Pinus albicaulis) in alpine and subalpine areas.

Growing Season Conditions Mediate the Dependence of Aspen on Redistributed Snow Under Climate Change.

Science.gov (United States)

Soderquist, B.; Kavanagh, K.; Link, T. E.; Seyfried, M. S.; Strand, E. K.

2016-12-01

Precipitation regimes in many semiarid ecosystems are becoming increasingly dominated by winter rainfall as a result of climate change. Across these regions, snowpack plays a vital role in the distribution and timing of soil moisture availability. Rising temperatures will result in a more uniform distribution of soil moisture, advanced spring phenology, and prolonged growing seasons. Productive and wide ranging tree species like aspen, Populus tremuloides, may experience increased vulnerability to drought and mortality resulting from both reduced snowpack and increased evaporative demand during the growing season. We simulated the net primary production (NPP) of aspen stands spanning the rain:snow transition zone in the Reynolds Creek Critical Zone Observatory (RCCZO) in southwest Idaho, USA. Within the RCCZO, the total amount of precipitation has remained unchanged over the past 50 years, however the percentage of the precipitation falling as snow has declined by approximately 4% per decade at mid-elevation sites. The biogeochemical process model Biome-BGC was used to simulate aspen NPP at three stands located directly below snowdrifts that provide melt water late into the spring. After adjusting precipitation inputs to account for the redistribution of snow, we assessed climate change impacts on future aspen productivity. Mid-century (2046-2065) aspen NPP was simulated using temperature projections from a multi-model average under high emission conditions using the Multivariate Adaptive Constructed Analogs (MACA) data set. While climate change simulations indicated over a 20% decrease in annual NPP for some years, NPP rates for other mid-century years remained relatively unchanged due to variations in growing season conditions. Mid-century years with the largest decreases in NPP typically showed increased spring transpiration rates resulting from earlier leaf flush combined with warmer spring conditions. During these years, the onset of drought stress occurred

Long-term temporal changes in central European tree phenology (1946-2010) confirm the recent extension of growing seasons

Science.gov (United States)

Kolářová, Eva; Nekovář, Jiří; Adamík, Peter

2014-10-01

One of the ways to assess the impacts of climate change on plants is analysing their long-term phenological data. We studied phenological records of 18 common tree species and their 8 phenological phases, spanning 65 years (1946-2010) and covering the area of the Czech Republic. For each species and phenophase, we assessed the changes in its annual means (for detecting shifts in the timing of the event) and standard deviations (for detecting changes in duration of the phenophases). The prevailing pattern across tree species was that since around the year 1976, there has been a consistent advancement of the onset of spring phenophases (leaf unfolding and flowering) and subsequent acceleration of fruit ripening, and a delay of autumn phenophases (leaf colouring and leaf falling). The most considerable shifts in the timing of spring phenophases were displayed by early-successional short-lived tree species. The most pronounced temporal shifts were found for the beginning of seed ripening in conifers with an advancement in this phenophase of up to 2.2 days year-1 in Scots Pine ( Pinus sylvestris). With regards to the change in duration of the phenophases, no consistent patterns were revealed. The growing season has extended on average by 23.8 days during the last 35 years. The most considerable prolongation was found in Pedunculate Oak ( Quercus robur): 31.6 days (1976-2010). Extended growing season lengths do have the potential to increase growth and seed productivity, but unequal shifts among species might alter competitive relationships within ecosystems.

Ecohydrology in Mediterranean areas: a numerical model to describe growing seasons out of phase with precipitations

Directory of Open Access Journals (Sweden)

D. Pumo

2008-02-01

Full Text Available The probabilistic description of soil moisture dynamics is a relatively new topic in hydrology. The most common ecohydrological models start from a stochastic differential equation describing the soil water balance, where the unknown quantity, the soil moisture, depends both on spaces and time. Most of the solutions existing in literature are obtained in a probabilistic framework and under steady-state condition; even if this last condition allows the analytical handling of the problem, it has considerably simplified the same problem by subtracting generalities from it.

The steady-state hypothesis, appears perfectly applicable in arid and semiarid climatic areas like those of African's or middle American's savannas, but it seems to be no more valid in areas with Mediterranean climate, where, notoriously, the wet season foregoes the growing season, recharging water into the soil. This moisture stored at the beginning of the growing season (known as soil moisture initial condition has a great importance, especially for deep-rooted vegetation, by enabling survival in absence of rainfalls during the growing season and, however, keeping the water stress low during the first period of the same season.

The aim of this paper is to analyze the soil moisture dynamics using a simple non-steady numerical ecohydrological model. The numerical model here proposed is able to reproduce soil moisture probability density function, obtained analytically in previous studies for different climates and soils in steady-state conditions; consequently it can be used to compute both the soil moisture time-profile and the vegetation static water stress time-profile in non-steady conditions.

Here the differences between the steady-analytical and the non-steady numerical probability density functions are analyzed, showing how the proposed numerical model is able to capture the effects of winter recharge on the soil moisture. The dynamic

Growth, allocation and tissue chemistry of Picea abies seedlings affected by nutrient supply during the second growing season.

Science.gov (United States)

Kaakinen, Seija; Jolkkonen, Annika; Iivonen, Sari; Vapaavuori, Elina

2004-06-01

One-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were grown hydroponically in a growth chamber to investigate the effects of low and high nutrient availability (LN; 0.25 mM N and HN; 2.50 mM N) on growth, biomass allocation and chemical composition of needles, stem and roots during the second growing season. Climatic conditions in the growth chamber simulated the mean growing season from May to early October in Flakaliden, northern Sweden. In the latter half of the growing season, biomass allocation changed in response to nutrient availability: increased root growth and decreased shoot growth led to higher root/shoot ratios in LN seedlings than in HN seedlings. At high nutrient availability, total biomass, especially stem biomass, increased, as did total nonstructural carbohydrate and nitrogen contents per seedling. Responses of stem chemistry to nutrient addition differed from those of adult trees of the same provenance. In HN seedlings, concentrations of alpha-cellulose, hemicellulose and lignin decreased in the secondary xylem. Our results illustrate the significance of retranslocation of stored nutrients to support new growth early in the season when root growth and nutrient uptake are still low. We conclude that nutrient availability alters allocation patterns, thereby influencing the success of 2-year-old Norway spruce seedlings at forest planting sites.

Comparison of phenology models for predicting the onset of growing season over the Northern Hemisphere.

Directory of Open Access Journals (Sweden)

Yang Fu

Full Text Available Vegetation phenology models are important for examining the impact of climate change on the length of the growing season and carbon cycles in terrestrial ecosystems. However, large uncertainties in present phenology models make accurate assessment of the beginning of the growing season (BGS a challenge. In this study, based on the satellite-based phenology product (i.e. the V005 MODIS Land Cover Dynamics (MCD12Q2 product, we calibrated four phenology models, compared their relative strength to predict vegetation phenology; and assessed the spatial pattern and interannual variability of BGS in the Northern Hemisphere. The results indicated that parameter calibration significantly influences the models' accuracy. All models showed good performance in cool regions but poor performance in warm regions. On average, they explained about 67% (the Growing Degree Day model, 79% (the Biome-BGC phenology model, 73% (the Number of Growing Days model and 68% (the Number of Chilling Days-Growing Degree Day model of the BGS variations over the Northern Hemisphere. There were substantial differences in BGS simulations among the four phenology models. Overall, the Biome-BGC phenology model performed best in predicting the BGS, and showed low biases in most boreal and cool regions. Compared with the other three models, the two-phase phenology model (NCD-GDD showed the lowest correlation and largest biases with the MODIS phenology product, although it could catch the interannual variations well for some vegetation types. Our study highlights the need for further improvements by integrating the effects of water availability, especially for plants growing in low latitudes, and the physiological adaptation of plants into phenology models.

Comparison of phenology models for predicting the onset of growing season over the Northern Hemisphere.

Science.gov (United States)

Fu, Yang; Zhang, Haicheng; Dong, Wenjie; Yuan, Wenping

2014-01-01

Vegetation phenology models are important for examining the impact of climate change on the length of the growing season and carbon cycles in terrestrial ecosystems. However, large uncertainties in present phenology models make accurate assessment of the beginning of the growing season (BGS) a challenge. In this study, based on the satellite-based phenology product (i.e. the V005 MODIS Land Cover Dynamics (MCD12Q2) product), we calibrated four phenology models, compared their relative strength to predict vegetation phenology; and assessed the spatial pattern and interannual variability of BGS in the Northern Hemisphere. The results indicated that parameter calibration significantly influences the models' accuracy. All models showed good performance in cool regions but poor performance in warm regions. On average, they explained about 67% (the Growing Degree Day model), 79% (the Biome-BGC phenology model), 73% (the Number of Growing Days model) and 68% (the Number of Chilling Days-Growing Degree Day model) of the BGS variations over the Northern Hemisphere. There were substantial differences in BGS simulations among the four phenology models. Overall, the Biome-BGC phenology model performed best in predicting the BGS, and showed low biases in most boreal and cool regions. Compared with the other three models, the two-phase phenology model (NCD-GDD) showed the lowest correlation and largest biases with the MODIS phenology product, although it could catch the interannual variations well for some vegetation types. Our study highlights the need for further improvements by integrating the effects of water availability, especially for plants growing in low latitudes, and the physiological adaptation of plants into phenology models.

Transmittance of young Norway spruce stand canopy for photosynthetically active radiation during the growing season

International Nuclear Information System (INIS)

Markova, I.; Kubasek, J.

2013-01-01

Analysis of transmittance of young Norway spruce stand canopy for photosynthetically active radiation (PAR) was made at the study site of Bily Kriz (the Moravian-Silesian Beskids Mts., the Czech Republic) at different sky conditions during the growing season in 2010. For the description of PAR transmittance different phenological phases of the spruce stand development in clear and overcast days were chosen. The mean daily PAR transmittance of the spruce canopy was significantly higher in overcast days compared with clear ones. Diffuse PAR thus penetrated into lower parts of the canopy more efficiently than direct one. PAR transmittance of young Norway spruce stand canopy was different in individual phenological phases of the spruce stand canopy which was caused by changes in the stand structure during the growing season. Thus monitoring of transmittance of young Norway spruce stand canopy for PAR can help to describe the development of spruce stand canopy

Effects of dormant and growing season burning on surface fuels and potential fire behavior in northern Florida longleaf pine (Pinus palustris) flatwoods

Science.gov (United States)

James B. Cronan; Clinton S. Wright; Maria Petrova

2015-01-01

Prescribed fire is widely used to manage fuels in high-frequency, low-severity fire regimes including pine flatwoods of the southeastern USA where prescribed burning during the growing season (the frost-free period during the calendar year) has become more common in recent decades. Growing season prescribed fires address ecological management objectives that focus on...

Environmental and Physiographic Controls on Inter-Growing Season Variability of Carbon Dioxide and Water Vapour Fluxes in a Minerotrophic Fen

Science.gov (United States)

van der Kamp, G.; Sonnentag, O.; Chen, J. M.; Barr, A.; Hedstrom, N.; Granger, R.

2008-12-01

The interaction of fens with groundwater is spatially and temporally highly variable in response to meteorological conditions, resulting in frequent changes of groundwater fluxes in both vertical and lateral directions (flow reversals) across the mineral soil-peat boundary. However, despite the importance of the topographic and hydrogeological setting of fens, no study has been reported in the literature that explores a fen's atmospheric CO2 and energy flux densities under contrasting meteorological conditions in response to its physiographic setting. In our contribution we report four years of growing season eddy covariance and supporting measurements from the Canada Fluxnet-BERMS fen (formerly BOREAS southern peatland) in Saskatchewan, Canada. We first analyze hydrological data along two piezometer transects across the mineral soil-peat boundary with the objective of assessing changes in water table configuration and thus hydraulic gradients, indicating flow reversals, in response to dry and wet meteorological conditions. Next we quantify and compare growing season totals and diurnal and daily variations in evapotranspiration (ET) and net ecosystem exchange (NEE) and its component fluxes gross ecosystem productivity (GPP) and terrestrial ecosystem respiration (TER) to identify their controls with a major focus on water table depth. While ET growing season totals were similar (~ 310 mm) under dry and wet meteorological conditions, the CO2 sink- source strength of Sandhill fen varied substantially from carbon neutral (NEE = -2 [+-7] g C m-2 per growing season) under dry meteorological condition (2003) to a moderate CO2- sink with NEE ranging between 157 [+- 10] and 190 [+- 11] g C m-2 per growing season under wet meteorological conditions (2004, 2005, and 2006). Using a process-oriented ecosystem model, BEPS-TerrainLab, we investigate how different canopy components at Sandhill contribute to total ET and GPP, and thus water use efficiency, under dry and wet

Seasonal variation in the behaviour of a short-lived rodent.

Science.gov (United States)

Eccard, Jana A; Herde, Antje

2013-11-15

Short lived, iteroparous animals in seasonal environments experience variable social and environmental conditions over their lifetime. Animals can be divided into those with a "young-of-the-year" life history (YY, reproducing and dying in the summer of birth) and an "overwinter" life history (OW, overwintering in a subadult state before reproducing next spring).We investigated how behavioural patterns across the population were affected by season and sex, and whether variation in behaviour reflects the variation in life history patterns of each season. Applications of pace-of-life (POL) theory would suggest that long-lived OW animals are shyer in order to increase survival, and YY are bolder in order to increase reproduction. Therefore, we expected that in winter and spring samples, when only OW can be sampled, the animals should be shyer than in summer and autumn, when both OW and YY animals can be sampled.We studied common vole (Microtus arvalis) populations, which express typical, intra-annual density fluctuation. We captured a total of 492 voles at different months over 3 years and examined boldness and activity level with two standardised behavioural experiments. Behavioural variables of the two tests were correlated with each other. Boldness, measured as short latencies in both tests, was extremely high in spring compared to other seasons. Activity level was highest in spring and summer, and higher in males than in females. Being bold in laboratory tests may translate into higher risk-taking in nature by being more mobile while seeking out partners or valuable territories. Possible explanations include asset-protection, with OW animals being rather old with low residual reproductive value in spring. Therefore, OW may take higher risks during this season. Offspring born in spring encounter a lower population density and may have higher reproductive value than offspring of later cohorts. A constant connection between life history and animal personality, as

Variation in damage from growing-season frosts among open-pollinated families of red alder.

Science.gov (United States)

Kevin C. Peeler; Dean S. DeBell

1987-01-01

Repeated growing-season frosts during late April and early May 1985 caused extensive damage to red alder (Alnus rubra Bong.) seedlings in a newly planted research trial in western Washington. About two-thirds of the seedlings were severely damaged (entire stem damaged or necrotic). Such damage varied by family, from 50 percent of seedlings in the...

Observed and Projected Changes in Thermal Growing Degree-Days and Growing Season and Their Divergent Responses to Warming over China

Science.gov (United States)

Deng, H.

2017-12-01

Vegetation growth and phenology are largely regulated by the growing degree-days (GDD) and growing season (GS). By choosing 0°C, 5°C and 10°C, three key based temperatures (Tb) for vegetation growth, the GDD and GS in China during the observed period (1960-2011) were developed using homogenized daily mean temperatures (Td) in 536 meteorological stations. In addition, the GDD10 and GS10 in China were projected under the representative concentration pathway scenarios (RCPs) during 1961-2099, using the Td (0.5°×0.5°) derived from five general circulation models (GCMs), after model evaluation. Advance in the start of the growing season (SOS; 4.86-6.71 days; SOS0 > SOS5 > SOS10) and delay in the end of the growing season (EOS; 4.32-6.19 days; EOS0 GDD5 > GDD10), in China as a whole. Each observed variation has a substantial acceleration mostly in 1987 or 1996, and a speed reduction or a trend reversal in the early 2000s. Increases in the GDD10 and GS10 would continue in the 21st century, causing northward shifts in the temperature zones. Finally in the long-term (2071-2099), the nationally average GDD10 and GS10 would be 279.1°C·d higher and 16.5 d longer for RCP 2.6, and 964.4°C·d higher and 50.3 d longer for RCP 8.5, relative to 1981-2010. Regionally, the GDD enhancement were stronger in the tropics, east, northeast and northwest China during the observed period, and tend to be in southern China in the future. The largest GS extensions are consistently in the eastern and southern parts of the Tibetan Alpine zone, particularly in the future. During the observed period, advance in SOS and delay in EOS drove the GS extensions in the eastern monsoon zone and northwest arid/semi-arid zone respectively. In the future, an advanced SOS drives the GS extension in the northern (> ca. 33°N) Tibetan Alpine zone, the mountainous areas in northeast China, and south of the Tropic of Cancer. The GDD and GS showed positive sensitivity to the temperature (GDD0 > GDD5 > GDD10

How well do growing season dynamics of photosynthetic capacity correlate with leaf biochemistry and climate fluctuations?

Science.gov (United States)

Way, Danielle A; Stinziano, Joseph R; Berghoff, Henry; Oren, Ram

2017-07-01

Accurate values of photosynthetic capacity are needed in Earth System Models to predict gross primary productivity. Seasonal changes in photosynthetic capacity in these models are primarily driven by temperature, but recent work has suggested that photoperiod may be a better predictor of seasonal photosynthetic capacity. Using field-grown kudzu (Pueraria lobata (Willd.) Ohwi), a nitrogen-fixing vine species, we took weekly measurements of photosynthetic capacity, leaf nitrogen, and pigment and photosynthetic protein concentrations and correlated these with temperature, irradiance and photoperiod over the growing season. Photosynthetic capacity was more strongly correlated with photoperiod than with temperature or daily irradiance, while the growing season pattern in photosynthetic capacity was uncoupled from changes in leaf nitrogen, chlorophyll and Rubisco. Daily estimates of the maximum carboxylation rate of Rubisco (Vcmax) based on either photoperiod or temperature were correlated in a non-linear manner, but Vcmax estimates from both approaches that also accounted for diurnal temperature fluctuations were similar, indicating that differences between these models depend on the relevant time step. We advocate for considering photoperiod, and not just temperature, when estimating photosynthetic capacity across the year, particularly as climate change alters temperatures but not photoperiod. We also caution that the use of leaf biochemical traits as proxies for estimating photosynthetic capacity may be unreliable when the underlying relationships between proxy leaf traits and photosynthetic capacity are established outside of a seasonal framework. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Topoclimate effects on growing season length and montane conifer growth in complex terrain

Science.gov (United States)

Barnard, D. M.; Barnard, H. R.; Molotch, N. P.

2017-05-01

Spatial variability in the topoclimate-driven linkage between forest phenology and tree growth in complex terrain is poorly understood, limiting our understanding of how ecosystems function as a whole. To characterize the influence of topoclimate on phenology and growth, we determined the start, end, and length of the growing season (GSstart, GSend, and GSL, respectively) using the correlation between transpiration and evaporative demand, measured with sapflow. We then compared these metrics with stem relative basal area increment (relative BAI) at seven sites among elevation and aspects in a Colorado montane forest. As elevation increased, we found shorter GSL (-50 d km-1) due to later GSstart (40 d km-1) and earlier GSend (-10 d km-1). North-facing sites had a 21 d shorter GSL than south-facing sites at similar elevations (i.e. equal to 200 m elevation difference on a given aspect). Growing season length was positively correlated with relative BAI, explaining 83% of the variance. This study shows that topography exerts strong environmental controls on GSL and thus forest growth. Given the climate-related dependencies of these controls, the results presented here have important implications for ecosystem responses to changes in climate and highlight the need for improved phenology representation in complex terrain.

Grazing exclusion increases soil CO2 emission during the growing season in alpine meadows on the Tibetan Plateau

Science.gov (United States)

Guo, Na; Wang, Aidong; Allan Degen, A.; Deng, Bin; Shang, Zhanhuan; Ding, Luming; Long, Ruijun

2018-02-01

Soil CO2 emission is a key part of the terrestrial carbon cycle. Grazing exclusion by fencing is often considered a beneficial grassland management option to restore degraded grassland, but its effect on soil CO2 emission on the northeastern Tibetan Plateau is equivocal and is the subject of this study. Using a closed static chamber, we measured diurnal soil CO2 flux weekly from July, 2008, to April, 2009, in response to grazing and grazing exclusion in the alpine meadow and alpine shrub meadow. Concomitantly, soil temperature was measured at depths of 5 cm, 10 cm, 15 cm and 20 cm with digital temperature sensors. It emerged that: 1) non-grazed grasslands emitted more soil CO2 than grazed grasslands over the growing season; 2) the alpine shrub meadow emitted more soil CO2 than the alpine meadow; the annual cumulative soil CO2 emissions of alpine meadow and alpine shrub meadow were 241.5-326.5 g C/m2 and 429.0-512.5 g C/m2, respectively; 3) seasonal patterns were evident with more soil CO2 flux in the growing than in the non-growing season; and 4) the diurnal soil CO2 flux exhibited a single peak across all sampling sites. In addition, soil CO2 flux was correlated positively with soil temperature at 5 cm, but not at the other depths. We concluded that grazing exclusion enhanced soil CO2 emission over the growing season, and decreased carbon sequestration of alpine meadow and alpine shrub meadow on the northeastern Tibetan Plateau. Since an increase in soil temperature increased soil CO2 flux, global warming could have an effect on soil CO2 emission in the future.

Seasonal variation in short-term mortality after surgery for colorectal cancer?

DEFF Research Database (Denmark)

Iversen, L H; Nielsen, H; Pedersen, L

2010-01-01

Comorbidity has a major impact on short-term and long-term survival of colorectal cancer (CRC) and many CRC patients suffer from comorbidities. Mortality rates for comorbidities like cardio-respiratory diseases exhibit distinct seasonal variations with highest rates in the winter. Therefore, we...

Leaf ontogeny dominates the seasonal exchange of volatile organic compounds (VOC) in a SRC-poplar plantation during an entire growing season

Science.gov (United States)

Brilli, Federico; Gioli, Beniamino; Fares, Silvano; Zenone, Terenzio; Zona, Donatella; Gielen, Bert; Loreto, Francesco; Janssens, Ivan; Ceulemans, Reinhart

2015-04-01

The declining cost of many renewable energy technologies and changes in the prices of fossil fuels have recently encouraged governments policies to subsidize the use of biomass as a sustainable source of energy. Deciduous poplars (Populus spp.) trees are often selected for biomass production in short rotation coppiced (SRC) for their high CO2 photosynthetic assimilation rates and their capacity to develop dense canopies with high values of leaf area index (LAI). So far, observations and projections of seasonal variations of many VOC fluxes has been limited to strong isoprenoids emitting evergreen ecosystems such tropical and Mediterranean forests as well as Citrus and oil palm plantation, all having constant values of LAI. We run a long-term field campaign where the exchange of VOC, together with CO2 and water vapor was monitored during an entire growing season (June - November, 2012) above a SRC-based poplar plantation. Our results confirmed that isoprene and methanol were the most abundant fluxes emitted, accounting for more than 90% of the total carbon released in form of VOC. However, Northern climates characterized by fresh summertime temperatures and recurring precipitations favored poplar growth while inhibiting the development of isoprene emission that resulted in only 0.7% of the net ecosystem carbon exchange (NEE). Besides, measurements of a multitude of VOC fluxes by PTR-TOF-MS showed bi-directional exchange of oxygenated-VOC (OVOC) such as: formaldehyde, acetaldehyde, acetone, isoprene oxidation products (iox, namely MVK, MAC and MEK) as well as ethanol and formic acid. The application of Self Organizing Maps to visualize the relationship between the full time-series of many VOC fluxes and the observed seasonal variations of environmental, physiological and structural parameters proved the most abundant isoprene ad methanol fluxes to occur mainly on the hottest days under mid-high light intensities when also NEE and evapotraspiration reached the highest

[Temporal and spatial change of climate resources and meteorological disasters under climate change during winter crop growing season in Guangdong Province, China.

Science.gov (United States)

Wang, Hua; Chen, Hui Hua; Tang, Li Sheng; Wang, Juan Huai; Tang, Hai Yan

2018-01-01

Trend analysis method was applied to analyze the general variation characteristics of the climate resources and meteorological disasters of growing season of the winter planting in Guangdong before (1961-1996) and after climate warming (1997-2015). Percentile method was employed to determine thresholds for extreme cold and drought in major planting regions, and the characteristics of extreme disasters since climate warming were analyzed. The results showed that, by comparing 1997-2015 with 1961-1996, the heat value in winter growing season increased significantly. The belt with a higher heat value, where the average temperature was ≥15 ℃ and accumulated temperature was ≥2200 ℃·d, covered the main winter production regions as Shaoguan, Zhanjiang, Maoming, Huizhou, Meizhou and Guangzhou. Meanwhile, the precipitation witnessed a slight increase. The regions with precipitations of 250-350 mm included Zhanjiang, Maoming, Huizhou, Guangzhou and Meizhou. Chilling injury in the winter planting season in the regions decreased, the belt with an accumulated chilling of climate resources and the occurrence law of meteorological disasters in growing season.

The flux of ozone to a maize crop and the underlying soil during a growing season

NARCIS (Netherlands)

Pul, van W.A.J.

1992-01-01

To observe the flux or deposition of ozone above a maize crop, experiments were carried out during the growing season of maize in 1988. The flux of ozone was determined using meteorological techniques. The measurements used in the present study were carried out under atmospheric conditions

How does climate influence xylem morphogenesis over the growing season? Insights from long-term intra-ring anatomy in Picea abies.

Science.gov (United States)

Castagneri, Daniele; Fonti, Patrick; von Arx, Georg; Carrer, Marco

2017-04-01

During the growing season, the cambium of conifer trees produces successive rows of xylem cells, the tracheids, that sequentially pass through the phases of enlargement and secondary wall thickening before dying and becoming functional. Climate variability can strongly influence the kinetics of morphogenetic processes, eventually affecting tracheid shape and size. This study investigates xylem anatomical structure in the stem of Picea abies to retrospectively infer how, in the long term, climate affects the processes of cell enlargement and wall thickening. Tracheid anatomical traits related to the phases of enlargement (diameter) and wall thickening (wall thickness) were innovatively inspected at the intra-ring level on 87-year-long tree-ring series in Picea abies trees along a 900 m elevation gradient in the Italian Alps. Anatomical traits in ten successive tree-ring sectors were related to daily temperature and precipitation data using running correlations. Close to the altitudinal tree limit, low early-summer temperature negatively affected cell enlargement. At lower elevation, water availability in early summer was positively related to cell diameter. The timing of these relationships shifted forward by about 20 (high elevation) to 40 (low elevation) d from the first to the last tracheids in the ring. Cell wall thickening was affected by climate in a different period in the season. In particular, wall thickness of late-formed tracheids was strongly positively related to August-September temperature at high elevation. Morphogenesis of tracheids sequentially formed in the growing season is influenced by climate conditions in successive periods. The distinct climate impacts on cell enlargement and wall thickening indicate that different morphogenetic mechanisms are responsible for different tracheid traits. Our approach of long-term and high-resolution analysis of xylem anatomy can support and extend short-term xylogenesis observations, and increase our

Non-growing season soil CO2 efflux patterns in five land-use types in northern China

Science.gov (United States)

Overgrazing and unsuitable farming practices have led to grassland degradation in northern China. This studhy examined soil CO2 efflux (Fc) from five land-use types during the non-growing season on the southeastern edge of the Mongolian Plateau in China. The land-use types included three native v...

Identification of proteins from cambium tissues of the chinese white poplar (populus tomentosa) sampled during the growing season

International Nuclear Information System (INIS)

Xie, J.; Liu, S.; Qi, Q.; Hou, Y.

2014-01-01

Various protein extraction methods have been used to investigate Chinese white poplar (Populus tomentosa) proteomics. However, extracting and characterizing proteins from woody plants remains a challenge. Two-dimensional gel electrophoresis is a powerful, widely used method for the analysis of complex protein mixtures extracted from biological samples. The technique separates mixtures of proteins along two dimensions, by isoelectric point and molecular weight, and can resolve thousands of different proteins. Here, we report a new application of two-dimensional gel electrophoresis to investigate the proteomics of P. tomentosa cambium tissues over the course of a growing season. Of three protein extraction methods that we compared (the Tris-phenol method, trichloroacetic acid-acetone method, and trichloroacetic acid-acetone-phenol method), trichloroacetic acid-acetone was the most efficient approach for protein extraction from cambium tissues of P. tomentosa. After extraction, the proteins were separated using two-dimensional gel electrophoresis. The protein quantities of six spots changed over the course of the growing season from February to July. Five spots were identified using matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry, and the sixth spot was identified by liquid chromatography-mass spectrometry. The proteins included enolase, class Ia chitinase, and four unnamed proteins. Our results show the best approach to proteomics in P. tomentosa and reveal trends in protein activities during a growing season in this tree species. (author)

The variation of methane flux rates from boreal tree species at the beginning of the growing season

Science.gov (United States)

Haikarainen, Iikka; Halmeenmäki, Elisa; Machacova, Katerina; Pihlatie, Mari

2016-04-01

Boreal forests are considered as net sink for atmospheric methane (CH4) because of the CH4 oxidizing bacteria in the aerobic soil layer. However, within the last decades it has become more evident that trees play an important role in the global CH4 budget by offering pathways for anaerobically produced CH4 from deeper soil layers to the atmosphere. Furthermore, trees may also act as independent sources of CH4. To confirm magnitude, variability and the origin of the tree mediated CH4 emissions more research is needed, especially in boreal forests which have been in a minority in such investigation. We measured tree stem and shoot CH4 exchange of three boreal tree species at the beginning of the growing season (13.4.-13.6.2015) at SMEAR II station in Hyytiälä, located in southern Finland (61° 51'N, 24° 17'E, 181 asl). The fluxes were measured from silver birch (Betula pendula), downy birch (B. pubescens) and Norway spruce (Picea abies) on two sites with differing soil type and characteristics (paludified and mineral soil), vegetation and forest structure by using the static chamber technique. Scaffold towers were used for measurements at multiple stem heights and shoots. The aim was to study the vertical profile of CH4 fluxes at stem and shoot level and compare these fluxes among the studied species, and to observe temporal changes in CH4 flux over the beginning of the growing season. We found that all the trees emitted CH4 from their stems and shoots. Overall, the birches showed higher emissions compared to the spruces. The emission rates were considerably larger in the lower parts of the birch stems than upper parts, and these emissions increased during the growing season. The spruces had more variation in the stem CH4 flux, but the emission rates of the upper parts of the stem exceeded the birch emissions at the same height. The shoot fluxes of all the studied trees indicated variable CH4 emissions without a clear pattern regarding the vertical profile and

Spatio-Temporal Changes in Vegetation Activity and Its Driving Factors during the Growing Season in China from 1982 to 2011

Directory of Open Access Journals (Sweden)

Bo Qu

2015-10-01

Full Text Available Using National Oceanographic and Atmospheric Administration/Advanced Very High Resolution Radiometer (NOAA/AVHRR and Climatic Research Unit (CRU climate datasets, we analyzed interannual trends in the growing-season Normalized Difference Vegetation Index (NDVI in China from 1982 to 2011, as well as the effects of climatic variables and human activities on vegetation variation. Growing-season (period between the onset and end of plant growth NDVI significantly increased (p < 0.01 on a national scale and showed positive trends in 52.76% of the study area. A multiple regression model was used to investigate the response of vegetation to climatic factors during recent and previous time intervals. The interactions between growing-season NDVI and climatic variables were more complex than expected, and a lag existed between climatic factors and their effects on NDVI. The regression residuals were used to show that over 6% of the study area experienced significantly human-induced vegetation variations (p < 0.05. These regions were mostly located in densely populated, reclaimed agriculture, afforestation, and conservation areas. Similar conclusions were drawn based on land-use change over the study period.

Intraseasonal carbon sequestration and allocation in larch trees growing on permafrost in Siberia after 13C labeling (two seasons of 2013-2014 observation).

Science.gov (United States)

Masyagina, Oxana; Prokushkin, Anatoly; Kirdyanov, Alexander; Artyukhov, Aleksey; Udalova, Tatiana; Senchenkov, Sergey; Rublev, Aleksey

2016-12-01

This research is an attempt to study seasonal translocation patterns of photoassimilated carbon within trees of one of the high latitudes widespread deciduous conifer species Larix gmelinii (Rupr. Rupr). For this purpose, we applied whole-tree labeling by 13 CO 2 , which is a powerful and effective tool for tracing newly developed assimilates translocation to tissues and organs of a tree. Experimental plot has been established in a mature 105-year-old larch stand located within the continuous permafrost area near Tura settlement (Central Siberia, 64°17'13″N, 100°11'55″E, 148 m a.s.l.). Measurements of seasonal photosynthetic activity and foliage parameters (i.e., leaf length, area, biomass, etc.), and sampling were arranged from early growing season (June 8, 2013; May 14, 2014) until yellowing and senescence of needles (September 17, 2013; September 14, 2014). Labeling by 13 C of the tree branch (June 2013, for 3 branch replicates in 3 different trees) and the whole tree was conducted at early (June 2014), middle (July 2014), and late (August 2013) phase of growing season (for different trees in 3 replicates each time) by three pulses [(CO 2 )max = 3000-4000 ppmv, 13 CO 2 (30 % v/v)]. We found at least two different patterns of carbon translocation associated with larch CO 2 assimilation depending on needle phenology. In early period of growing season (June), 13 C appearing in newly developed needles is a result of remobilized storage material use for growth purposes. Then approximately at the end of June, growth processes is switching to storage processes lasting to the end of growing season.

Landscape controls on the timing of spring, autumn, and growing season length in mid-Atlantic forests

Science.gov (United States)

Elmore, A.J.; Guinn, S.M.; Minsley, B.J.; Richardson, A.D.

2012-01-01

The timing of spring leaf development, trajectories of summer leaf area, and the timing of autumn senescence have profound impacts to the water, carbon, and energy balance of ecosystems, and are likely influenced by global climate change. Limited field-based and remote-sensing observations have suggested complex spatial patterns related to geographic features that influence climate. However, much of this variability occurs at spatial scales that inhibit a detailed understanding of even the dominant drivers. Recognizing these limitations, we used nonlinear inverse modeling of medium-resolution remote sensing data, organized by day of year, to explore the influence of climate-related landscape factors on the timing of spring and autumn leaf-area trajectories in mid-Atlantic, USA forests. We also examined the extent to which declining summer greenness (greendown) degrades the precision and accuracy of observations of autumn offset of greenness. Of the dominant drivers of landscape phenology, elevation was the strongest, explaining up to 70% of the spatial variation in the onset of greenness. Urban land cover was second in importance, influencing spring onset and autumn offset to a distance of 32 km from large cities. Distance to tidal water also influenced phenological timing, but only within ~5 km of shorelines. Additionally, we observed that (i) growing season length unexpectedly increases with increasing elevation at elevations below 275 m; (ii) along gradients in urban land cover, timing of autumn offset has a stronger effect on growing season length than does timing of spring onset; and (iii) summer greendown introduces bias and uncertainty into observations of the autumn offset of greenness. These results demonstrate the power of medium grain analyses of landscape-scale phenology for understanding environmental controls on growing season length, and predicting how these might be affected by climate change.

Effects of fire disturbance on soil respiration in the non-growing season in a Larix gmelinii forest in the Daxing'an Mountains, China.

Science.gov (United States)

Hu, Tongxin; Sun, Long; Hu, Haiqing; Guo, Futao

2017-01-01

In boreal forests, fire is an important part of the ecosystem that greatly influences soil respiration, which in turn affects the carbon balance. Wildfire can have a significant effect on soil respiration and it depends on the fire severity and environmental factors (soil temperature and snow water equivalent) after fire disturbance. In this study, we quantified post-fire soil respiration during the non-growing season (from November to April) in a Larix gmelinii forest in Daxing'an Mountains of China. Soil respiration was measured in the snow-covered and snow-free conditions with varying degrees of natural burn severity forests. We found that soil respiration decreases as burn severity increases. The estimated annual C efflux also decreased with increased burn severity. Soil respiration during the non-growing season approximately accounted for 4%-5% of the annual C efflux in all site types. Soil temperature (at 5 cm depth) was the predominant determinant of non-growing season soil respiration change in this area. Soil temperature and snow water equivalent could explain 73%-79% of the soil respiration variability in winter snow-covering period (November to March). Mean spring freeze-thaw cycle (FTC) period (April) soil respiration contributed 63% of the non-growing season C efflux. Our finding is key for understanding and predicting the potential change in the response of boreal forest ecosystems to fire disturbance under future climate change.

Response of needle dark respiration of Pinus koraiensis and Pinus sylvestriformis to elevated CO2 concentra-tions for four growing seasons’ exposure

Institute of Scientific and Technical Information of China (English)

2007-01-01

The long-term effect of elevated CO2 concentrations on needle dark respiration of two coniferous spe- cies—Pinus koraiensis and Pinus sylvestriformis on the Changbai Mountain was investigated using open-top chambers. P. koraiensis and P. sylvestriformis were exposed to 700, 500 μmol·mol-1 CO2 and ambient CO2 (approx. 350 μmol·mol-1) for four growing seasons. Needle dark respiration was meas- ured during the second, third and fourth growing seasons’ exposure to elevated CO2. The results showed that needle dark respiration rate increased for P. koraiensis and P. sylvestriformis grown at elevated CO2 concentrations during the second growing season, could be attributed to the change of carbohydrate and/or nitrogen content of needles. Needle dark respiration of P. koraiensis was stimu- lated and that of P. sylvestriformis was inhibited by elevated CO2 concentrations during the third growing season. Different response of the two tree species to elevated CO2 mainly resulted from the difference in the growth rate. Elevated CO2 concentrations inhibited needle dark respiration of both P. koraiensis and P. sylvestriformis during the fourth growing season. There was consistent trend be- tween the short-term effect and the long-term effect of elevated CO2 on needle dark respiration in P. sylvestriformis during the third growing season by changing measurement CO2 concentrations. How- ever, the short-term effect was different from the long-term effect for P. koraiensis. Response of dark respiration of P. koraiensis and P. sylvestriformis to elevated CO2 concentrations was related to the treatment time of CO2 and the stage of growth and development of plant. The change of dark respiration for the two tree species was determined by the direct effect of CO2 and long-term acclimation. The prediction of the long-term response of needle dark respiration to elevated CO2 concentration based on the short-term response is in dispute.

Growing season length as a key factor of cumulative net ecosystem exchange over the pine forest ecosystems in Europe

Czech Academy of Sciences Publication Activity Database

Danielewska, A.; Urbaniak, M.; Olejnik, Janusz

2015-01-01

Roč. 29, č. 2 (2015), s. 129-135 ISSN 0236-8722 Institutional support: RVO:67179843 Keywords : forest * carbon dioxide * eddy covariance * growing season length Subject RIV: EH - Ecology, Behaviour Impact factor: 1.067, year: 2015

Effects of fire disturbance on soil respiration in the non-growing season in a Larix gmelinii forest in the Daxing'an Mountains, China.

Directory of Open Access Journals (Sweden)

Tongxin Hu

Full Text Available In boreal forests, fire is an important part of the ecosystem that greatly influences soil respiration, which in turn affects the carbon balance. Wildfire can have a significant effect on soil respiration and it depends on the fire severity and environmental factors (soil temperature and snow water equivalent after fire disturbance. In this study, we quantified post-fire soil respiration during the non-growing season (from November to April in a Larix gmelinii forest in Daxing'an Mountains of China. Soil respiration was measured in the snow-covered and snow-free conditions with varying degrees of natural burn severity forests. We found that soil respiration decreases as burn severity increases. The estimated annual C efflux also decreased with increased burn severity. Soil respiration during the non-growing season approximately accounted for 4%-5% of the annual C efflux in all site types. Soil temperature (at 5 cm depth was the predominant determinant of non-growing season soil respiration change in this area. Soil temperature and snow water equivalent could explain 73%-79% of the soil respiration variability in winter snow-covering period (November to March. Mean spring freeze-thaw cycle (FTC period (April soil respiration contributed 63% of the non-growing season C efflux. Our finding is key for understanding and predicting the potential change in the response of boreal forest ecosystems to fire disturbance under future climate change.

Short Term Prediction of PM10 Concentrations Using Seasonal Time Series Analysis

Directory of Open Access Journals (Sweden)

Hamid Hazrul Abdul

2016-01-01

Full Text Available Air pollution modelling is one of an important tool that usually used to make short term and long term prediction. Since air pollution gives a big impact especially to human health, prediction of air pollutants concentration is needed to help the local authorities to give an early warning to people who are in risk of acute and chronic health effects from air pollution. Finding the best time series model would allow prediction to be made accurately. This research was carried out to find the best time series model to predict the PM10 concentrations in Nilai, Negeri Sembilan, Malaysia. By considering two seasons which is wet season (north east monsoon and dry season (south west monsoon, seasonal autoregressive integrated moving average model were used to find the most suitable model to predict the PM10 concentrations in Nilai, Negeri Sembilan by using three error measures. Based on AIC statistics, results show that ARIMA (1, 1, 1 × (1, 0, 012 is the most suitable model to predict PM10 concentrations in Nilai, Negeri Sembilan.

Efficiency of nitrogen fertilizer applied at corn sowing in contrasting growing seasons in Paraguay

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Telmo Jorge Carneiro Amado

2013-12-01

Full Text Available In order to select soil management practices that increase the nitrogen-use efficiency (NUE in agro-ecosystems, the different indices of agronomic fertilizer efficiency must be evaluated under varied weather conditions. This study assessed the NUE indices in no-till corn in southern Paraguay. Nitrogen fertilizer rates from 0 to 180 kg ha-1 were applied in a single application at corn sowing and the crop response investigated in two growing seasons (2010 and 2011. The experimental design was a randomized block with three replications. Based on the data of grain yield, dry matter, and N uptake, the following fertilizer indices were assessed: agronomic N-use efficiency (ANE, apparent N recovery efficiency (NRE, N physiological efficiency (NPE, partial factor productivity (PFP, and partial nutrient balance (PNB. The weather conditions varied largely during the experimental period; the rainfall distribution was favorable for crop growth in the first season and unfavorable in the second. The PFP and ANE indices, as expected, decreased with increasing N fertilizer rates. A general analysis of the N fertilizer indices in the first season showed that the maximum rate (180 kg ha-1 obtained the highest corn yield and also optimized the efficiency of NPE, NRE and ANE. In the second season, under water stress, the most efficient N fertilizer rate (60 kg ha-1 was three times lower than in the first season, indicating a strong influence of weather conditions on NUE. Considering that weather instability is typical for southern Paraguay, anticipated full N fertilization at corn sowing is not recommended due the temporal variability of the optimum N fertilizer rate needed to achieve high ANE.

Positive feedback of greenhouse gas balances to warming is determined by non-growing season emissions in an alpine meadow

Science.gov (United States)

Niu, S.; Wang, J.; Quan, Q.; Chen, W.; Wen, X.; Yu, G.

2017-12-01

Large uncertainties exist in the sources and sinks of greenhouse gases (CO2, CH4, N2O) in response to climate warming and human activity. So far, numerous previous studies have evaluated the CO2 budget, but little attention has paid to CH4 and N2O budgets and the concurrent balance of these three gases in combination, especially in the non-growing season. Here, we synthesized eddy covariance measurement with the automatic chamber measurements of CO2, CH4, and N2O exposed to three levels of temperature treatments (ambient, +1.5 °C, +2.5 °C) and two disturbance treatments (ummowing, mowing) in an alpine meadow on the Tibetan Plateau. We have found that warming caused increase in CH4 uptake and decrease in N2O emission offset little of the enhancement in CO2 emission, triggering a positive feedback to climate warming. Warming switches the ecosystem from a net sink (-17 ± 14 g CO2-eq m-2 yr-1) in the control to a net source of greenhouse gases of 94 ± 36 gCO2-eq m-2 yr-1 in the plots with +1.5 °C warming treatment, and 177 ± 6 gCO2-eq m-2 yr-1 in the plots with +2.5 °C warming treatment. The changes in the non-growing season balance, rather than those in the growing season, dominate the warming responses of annual greehouse gas balance. And this is not changed by mowing. The dominant role of responses of winter greenhouse gas balance in the positive feedback of ecosystem to climate warming highlights that greenhouse gas balance in cold season has to be considered when assessing climate-carbon cycle feedback.

Comparison of infiltration capacity of permanent grassland and arable land during the 2011 growing season

OpenAIRE

Tomáš Mašíček; F. Toman; M. Vičanová

2012-01-01

The aim of this paper was to compare the rate of infiltration and cumulative infiltration in permanent grassland (PG) and in arable land over the course of the 2011 growing season. The measurement of water infiltration into soil was conducted via ponded infiltration method based on the use of two concentric cylinders in field conditions. Kostiakov equations were applied to evaluate the ponded infiltration. Based on field measurements, the dependence of infiltration rate (v) on time (t) was de...

317/319 phytoremediation site monitoring report - 2003 growing season.

Energy Technology Data Exchange (ETDEWEB)

Negri, M. C.; Gopalakrishnan, G.; Hamilton, C.; Energy Systems

2004-02-20

In 1999, Argonne National Laboratory-East (ANL-E) designed and installed a series of engineered plantings consisting of a vegetative cover system and approximately 800 hybrid poplars and willows rooting at various predetermined depths. The plants were installed using various methods including Applied Natural Science's TreeWell{reg_sign} system. The goal of the installation was to protect downgradient surface and groundwater by hydraulic control of the contaminated plume by intercepting the contaminated groundwater with the tree roots, removing moisture from the upgradient soil area, reducing water infiltration, preventing soil erosion, degrading and/or transpiring the residual volatile organic compounds (VOCs), and removing tritium from the subsoil and groundwater. This report presents the results of the monitoring activities conducted by Argonne's Energy Systems Division (ES) in the growing season of 2003. ES was tasked with the biomonitoring of the plantation to determine contaminant uptake and groundwater contact. VOCs were found in plant tissue both at the French Drain and the Hydraulic Control locations in varying concentrations, and tritium levels in transpirate was found to continue a trend of higher concentrations compared to the background in the ANL-E area.

Effects of Repeated Growing Season Prescribed Fire on the Structure and Composition of Pine–Hardwood Forests in the Southeastern Piedmont, USA

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Matthew J. Reilly

2016-12-01

Full Text Available We examined the effects of repeated growing season prescribed fire on the structure and composition of mixed pine–hardwood forests in the southeastern Piedmont region, Georgia, USA. Plots were burned two to four times over an eight-year period with low intensity surface fires during one of four six-week long periods from early April to mid-September. Density of saplings (0.25–11.6 cm diameter at breast height was significantly reduced after one or two fires during the first four-year period. Sapling density declined with additional burning over the next four years, but density of mesic hardwoods including sweetgum (Liquidambar styraciflua and red maple (Acer rubrum remained relatively high (~865 stems ha−1. Repeated burning had little effect on density or basal area of trees (≥11.7 cm dbh and changes in overstory structure were limited to small increases in the quadratic mean diameter of all trees and pines. We found little evidence to suggest differential effects on structure or composition due to timing of burn within the growing season. Although repeated growing season burning alters midstory structure and composition, burning alone is unlikely to result in immediate shifts in overstory composition or structure in mixed pine–hardwood forests of the southeastern Piedmont region.

The Effects of Climate Change on Variability of the Growing Seasons in the Elbe River Lowland, Czech Republic

Czech Academy of Sciences Publication Activity Database

Potopová, V.; Zahradníček, Pavel; Türkot, L.; Štěpánek, Petr; Soukup, J.

2015-01-01

Roč. 2015, č. 546920 (2015), s. 546920 ISSN 1687-9309 R&D Projects: GA MŠk(CZ) EE2.3.20.0248 Institutional support: RVO:67179843 Keywords : Central Europe * extremes * climate change * growing seasons * Elbe River Lowland Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.107, year: 2015

Video data of flowers, fruitlets, and fruit in apple trees during the 2017 growing season at USDA-ARS-AFRS

Science.gov (United States)

This record contains videos of apple trees acquired from a ground vehicle throughout the growing season at the USDA-ARS, Appalachian Fruit Research Station. Research in precision management methods in orchard crops revolve around locating objects of interest, namely flowers, fruitlets, and fruit, a...

Effect of average growing season temperature on seedling germination, survival and growth in jack pine (Pinus banksiana Lamb.)

Science.gov (United States)

A. David; E. Humenberger

2017-01-01

Because jack pine (Pinus banksiana Lamb.) is serotinous, it retains multiple years of cones until environmental conditions are favorable for releasing seed. These cones, which contain seed cohorts that developed under a variety of growing seasons, can be accurately aged using bud scale scars on twigs and branches. By calculating the average daily...

Short-term progestagen treatment in ewes during the breeding season

OpenAIRE

Almeida, José Carlos; Simões, João; Valentim, Ramiro; Mascarenhas, R.; Fontes, Paulo; Azevedo, Jorge

2006-01-01

To characterize the efficiency of oestrus synchronization with short-term progestagen treatment (stFGA), 20 Ile de France (IF) and 19 Churra da Terra Quente (CTQ) ewes were used during the mid-breeding season. At day 0 (D0), a 40 mg FGA sponge was inserted in all animals and 120 µg cloprostenol was injected. Five days later (D5), all sponges were removed and ewes were divided into two groups: group A (10 IF and 10 CTQ), treated with eCG (250 UI) at sponge withdrawal and group II (10 IF and 9 ...

Spatio-Temporal Variations of Soil Water Use in the Growing Season in Northeast China Using Modis Data

Science.gov (United States)

Chang, s.; Huang, F.; Li, B.; Qi, H.; Zhai, H.

2018-04-01

Water use efficiency is known as an important indicator of carbon and water cycle and reflects the transformation capacity of vegetation water and nutrients into biomass. In this study, we presented a new indicator of water use efficiency, soil water use level (SWUL), derived from satellite remote sensing based gross primary production and the Visible and Shortwave Infrared Drought Index (VSDI). SWUL based on MODIS data was calculated for the growing season of 2014 in Northeast China, and the spatial pattern and the variation trend were analyzed. Results showed that the highest SWUL was observed in forestland with the value of 36.65. In cropland and grassland, the average SWUL were 26.18 and 29.29, respectively. SWUL showed an increased trend in the first half period of the growing season and peaked around the 200th day. After the 220th day, SWUL presented a decreasing trend. Compared to the soil water use efficiency (SWUE), SWUL might depict the water use status at finer spatial resolution. The new indicator SWUL can help promote understanding the water use efficiency for regions of higher spatial heterogeneity.

Land–Atmosphere Exchange of Water and Heat in the Arid Mountainous Grasslands of Central Asia during the Growing Season

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Xiaotao Huang

2017-09-01

Full Text Available Arid grassland ecosystems are widely distributed across Central Asia. However, there is a lack of research and observations of the land–atmosphere exchange of water and heat in the arid grasslands in this region, particularly over complex surfaces. In this study, systematic observations were conducted from 2013 to 2015 using an HL20 Bowen ratio and TDR300 and WatchDog1400 systems to determine the characteristics of these processes during the growing season (April–October of the arid mountainous grasslands of this region. (1 The latent heat flux (Le was lower than the sensible heat flux (He overall, and a small transient decrease in Le was observed before its daytime maximum; daily comparative variations in both fluxes were closely related to vegetation growth. (2 Evapotranspiration (ET showed substantial variation across different years, seasons and months, and monthly variations in ET were closely related to vegetation growth. Water condensation (Q was low and relatively stable. Relatively high levels of soil water were measured in spring followed by a decreasing trend. The land–atmosphere exchange of water and heat during the growing season in this region was closely associated with phenology, available precipitation and terrain. This study provides data support for the scientific management of arid mountainous grasslands.

Energy productivity and efficiency of maize accounting for the choice of growing season and environmental factors: An empirical analysis from Bangladesh

International Nuclear Information System (INIS)

Rahman, Sanzidur; Rahman, Md. Sayedur

2013-01-01

The paper evaluates sustainability of maize cultivation in Bangladesh in terms of energy use while taking into account factors affecting choice of the growing season and farmers' production environment using a sample selection framework applied to stochastic frontier models. Results reveal that the probability of growing winter maize is influenced positively by gross return, irrigation, subsistence pressure, soil suitability and temperature variability whereas extension contact influences choice negatively. Significant differences exist between winter and summer maize regarding yield, specific energy, net energy balance, energy use efficiency and technical energy efficiency although both systems are highly sustainable and efficient. The energy output from winter maize is 199,585 MJ/ha which is 53.9% higher than the summer maize output of 129,701 MJ/ha. Also, energy input use of winter maize is 110.6% higher than the summer maize. Energy inputs from mechanical power, seeds, fertilizers and organic manures significantly increase energy productivity of winter maize whereas only mechanical power influences summer maize productivity. However, temperature variation and rainfall significantly reduce energy productivity of summer maize. Policy implications include investments in soil conservation and irrigation, development of weather resistant varieties and raising maize price will boost maize cultivation in Bangladesh, a highly sustainable production technology. -- Highlights: ► Maize energy productivity is evaluated subject to season and environmental factors. ► Maize farming for both seasons is highly sustainable in terms of energy use. ► Socio-economic and environmental factors influence choice of growing winter maize. ► Mechanical power, rainfall and temperature influence summer maize productivity. ► Maize farmers of both seasons are highly technically efficient.

Changes in ultraviolet-B and visible optical properties and absorbing pigment concentrations in pecan leaves during a growing season

Science.gov (United States)

Yadong Qi; Shuju Bai; Gordon M. Heisler

2003-01-01

UV-B (280-320 nm) and visible (400-760 nm) spectral reflectance, transmittance, and absorptance; chlorophyll content; UV-B absorbing compound concentration; and leaf thickness were measured for pecan (Carya illinoensis) leaves over a growing season (April-October). Leaf samples were collected monthly from a pecan plantation located on the Southern...

Assessment of short- and long-term memory in trends of major climatic variables over Iran: 1966-2015

Science.gov (United States)

Mianabadi, Ameneh; Shirazi, Pooya; Ghahraman, Bijan; Coenders-Gerrits, A. M. J.; Alizadeh, Amin; Davary, Kamran

2018-02-01

In arid and semi-arid regions, water scarcity is the crucial issue for crop production. Identifying the spatial and temporal trends in aridity, especially during the crop-growing season, is important for farmers to manage their agricultural practices. This will become especially relevant when considering climate change projections. To reliably determine the actual trends, the influence of short- and long-term memory should be removed from the trend analysis. The objective of this study is to investigate the effect of short- and long-term memory on estimates of trends in two aridity indicators—the inverted De Martonne (ϕ IDM ) and Budyko (ϕ B ) indices. The analysis is done using precipitation and temperature data over Iran for a 50-year period (1966-2015) at three temporal scales: annual, wheat-growing season (October-June), and maize-growing season (May-November). For this purpose, the original and the modified Mann-Kendall tests (i.e., modified by three methods of trend free pre-whitening (TFPT), effective sample size (ESS), and long-term persistence (LTP)) are used to investigate the temporal trends in aridity indices, precipitation, and temperature by taking into account the effect of short- and long-term memory. Precipitation and temperature data were provided by the Islamic Republic of Iran Meteorological Organization (IRIMO). The temporal trend analysis showed that aridity increased from 1966 to 2015 at the annual and wheat-growing season scales, which is due to a decreasing trend in precipitation and an increasing trend in mean temperature at these two timescales. The trend in aridity indices was decreasing in the maize-growing season, since precipitation has an increasing trend for most parts of Iran in that season. The increasing trend in aridity indices is significant in Western Iran, which can be related to the significantly more negative trend in precipitation in the West. This increasing trend in aridity could result in an increasing crop water

Short dry spells in the wet season increase mortality of tropical pioneer seedlings.

Science.gov (United States)

Engelbrecht, Bettina M J; Dalling, James W; Pearson, Timothy R H; Wolf, Robert L; Gálvez, David A; Koehler, Tobias; Tyree, Melvin T; Kursar, Thomas A

2006-06-01

Variation in plant species performance in response to water availability offers a potential axis for temporal and spatial habitat partitioning and may therefore affect community composition in tropical forests. We hypothesized that short dry spells during the wet season are a significant source of mortality for the newly emerging seedlings of pioneer species that recruit in treefall gaps in tropical forests. An analysis of a 49-year rainfall record for three forests across a rainfall gradient in central Panama confirmed that dry spells of > or = 10 days during the wet season occur on average once a year in a deciduous forest, and once every other year in a semi-deciduous moist and an evergreen wet forest. The effect of wet season dry spells on the recruitment of pioneers was investigated by comparing seedling survival in rain-protected dry plots and irrigated control plots in four large artificially created treefall gaps in a semi-deciduous tropical forest. In rain-protected plots surface soil layers dried rapidly, leading to a strong gradient in water potential within the upper 10 cm of soil. Seedling survival for six pioneer species was significantly lower in rain-protected than in irrigated control plots after only 4 days. The strength of the irrigation effect differed among species, and first became apparent 3-10 days after treatments started. Root allocation patterns were significantly, or marginally significantly, different between species and between two groups of larger and smaller seeded species. However, they were not correlated with seedling drought sensitivity, suggesting allocation is not a key trait for drought sensitivity in pioneer seedlings. Our data provide strong evidence that short dry spells in the wet season differentially affect seedling survivorship of pioneer species, and may therefore have important implications to seedling demography and community dynamics.

Environmental and societal consequences of a possible CO/sub 2/-induced climate change. Volume II, Part 8. Impacts of rising atmospheric carbon dioxide levels on agricultural growing seasons and crop water use efficiencies

Energy Technology Data Exchange (ETDEWEB)

Newman, J. E.

1982-09-01

The researchable areas addressed relate to the possible impacts of climate change on agricultural growing seasons and crop adaptation responses on a global basis. The research activities proposed are divided into the following two main areas of investigation: anticipated climate change impacts on the physical environmental characteristics of the agricultural growing seasons and, the most probable food crop responses to the possible changes in atmospheric CO/sub 2/ levels in plant environments. The main physical environmental impacts considered are the changes in temperature, or more directly, thermal energy levels and the growing season evapotranspiration-precipitation balances. The resulting food crop, commercial forest and rangeland species response impacts addressed relate to potential geographical shifts in agricultural growing seasons as determined by the length in days of the frost free period, thermal energy changes and water balance changes. In addition, the interaction of possible changes in plant water use efficiencies during the growing season in relationship to changing atmospheric CO/sub 2/ concentrations, is also considered under the scenario of global warming due to increases in atmospheric CO/sub 2/ concentration. These proposed research investigations are followed by adaptive response evaluations.

Financial results achieved in short-day strawberry production

Directory of Open Access Journals (Sweden)

Galić Dragan

2014-01-01

Full Text Available In South-western Ontario's continental climate (short days, hot summers and very cold winters the matted-row system was the dominant production system to grow short-day strawberries. Varieties-staggered production (planting a combination of early, mid and late-season varieties provides strawberry harvest from five to seven weeks. Short-day strawberries are vegetative grown in the first year, and harvested for two consecutive years. The total cost of short-day strawberry production was 54,370 $CAD/ha. The production and harvest costs in the first and second years were 20,812 $CAD/ha and 16,930 $CAD/ ha, respectively, and accounted for 69.42% of the total. Pre-plans operations were the least expensive procedures costing 8.13%, while planting and care of young plants made up 22.45% of the total costs. The total income of growing short-day strawberries under a matted-row system was 76,671 $CAD/ha (the first and second production years 41,330 $CAD/ha and 35,341 $CAD/ha, respectively. The short-day strawberries in matted-row system, with average yield of 15,722 kg/ha, generated a net revenue of 22,300 $CAD/ha.

Restoring fire as an ecological process in shortgrass prairie ecosystems: initial effects of prescribed burning during the dormant and growing seasons.

Science.gov (United States)

Brockway, Dale G; Gatewood, Richard G; Paris, Randi B

2002-06-01

Prior to Anglo-European settlement, fire was a major ecological process influencing the structure, composition and productivity of shortgrass prairie ecosystems on the Great Plains. However during the past 125 years, the frequency and extent of grassland fire has dramatically declined as a result of the systematic heavy grazing by large herds of domestic cattle and sheep which reduced the available levels of fine fuel and organized fire suppression efforts that succeeded in altering the natural fire regime. The greatly diminished role of recurrent fire in these ecosystems is thought to be responsible for ecologically adverse shifts in the composition, structure and diversity of these grasslands, leading specifically to the rise of ruderal species and invasion by less fire-tolerant species. The purpose of this study was to evaluate the ecological effects of fire season and frequency on the shortgrass prairie and to determine the means by which prescribed fire can best be restored in this ecosystem to provide the greatest benefit for numerous resource values. Plant cover, diversity, biomass and nutrient status, litter cover and soil chemistry were measured prior to and following fire treatments on a buffalograss-blue grama shortgrass prairie in northeastern New Mexico. Dormant-season fire was followed by increases in grass cover, forb cover, species richness and concentrations of foliar P, K, Ca, Mg and Mn. Growing-season fire produced declines in the cover of buffalograss, graminoids and forbs and increases in litter cover and levels of foliar P, K, Ca and Mn. Although no changes in soil chemistry were observed, both fire treatments caused decreases in herbaceous production, with standing biomass resulting from growing-season fire approximately 600 kg/ha and dormant-season fire approximately 1200 kg/ha, compared with controls approximately 1800 kg/ha. The initial findings of this long-term experiment suggest that dormant-season burning may be the preferable method

Effects of Foliar Application of Nitrogen, Zinc and Manganese on Yield, Yield Components and Grain Quality of Chickpea in Two Growing Seasons

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B. Shirani

2015-09-01

Full Text Available To study the effects of foliar application of zinc, manganese and nitrogen on yield, yield components and grain quality of chickpea (Cicer arientinum L. two experiments, one in autumn and the other in spring were conducted at Research Farm, Shahrekord University in 2009-2010 growing season each as a randomized complete block design with three replications. The treatments were foliar application of zinc sulfate, manganese sulfate zinc sulfate and manganese sulfate mixture, nitrogen and distilled water (as control. The results showed that planting season had a significant effect on plant height, 100-seed weight and seed yield. All measured traits, except plant height, increased in winter compared to spring growing season. This increase was more than 12% for grain yield. Foliar application of nutrients significantly affected seed yield and seed yield components. Foliar application of nitrogen, presumably, through significant increase in number of pods per plant, number of seeds per plant and 100-seed weight, increased the grain yield by 6.2% compared to control. Foliar application × planting season interactions were significant for plant height and number of pods per plant. Foliar application of nitrogen caused a significant increase in grain yield and protein content. Foliar application of zinc sulphate significantly increased Zn content of grains however it did not affect seed yield. In conclusion, foliar application of nitrogen could be suggested for increasing protein and grain yield in chickpea under similar conditions to that of the present study.

Comparative study of holt-winters triples exponential smoothing and seasonal Arima: Forecasting short term seasonal car sales in South Africa

Directory of Open Access Journals (Sweden)

Katleho Daniel Makatjane

2016-02-01

Full Text Available In this paper, both Seasonal ARIMA and Holt-Winters models are developed to predict the monthly car sales in South Africa using data for the period of January 1994 to December 2013. The purpose of this study is to choose an optimal model suited for the sector. The three error metrics; mean absolute error, mean absolute percentage error and root mean square error were used in making such a choice. Upon realizing that the three forecast errors could not provide concrete basis to make conclusion, the power test was calculated for each model proving Holt-Winters to having about 0.3% more predictive power. Empirical results also indicate that Holt-Winters model produced more precise short-term seasonal forecasts. The findings also revealed a structural break in April 2009, implying that the car industry was significantly affected by the 2008 and 2009 US financial crisis

Production physiology and morphology of Populus species and their hybrids grown under short rotation. III. Seasonal carbon allocation patterns from branches

Energy Technology Data Exchange (ETDEWEB)

Scarascia-Mugnozza, G.E.; Hinckley, T.M.; Stettler, R.F. [Washington Univ., College of Forest Resources, Seattle, WA (United States)

1999-09-01

A study was carried out to compare highly productive cones, in the Pacific Northwest, in terms of contrasting growth and morphology. The objective of the study was to determine seasonal differences in carbon allocation patterns among 1- and 2-year old trees of Populus deltoides Bartr, and 2 of their interspecific hybrids. The study examined if there are different patterns of carbon allocation associated with the more productive poplar clones, how these patterns vary over the course of the growing season and from the first and the second year, if sylleptic branches vary from proleptic branches in their carbon allocation patterns, if there are the translocation patterns within branches and the degree of branch autonomy that exists with sylleptic and proleptic branches and if these patterns vary during the growing season. Previous findings on general patterns of carbon allocation in poplar clones were confirmed, and new dimensions were introduced regarding differences among branch types and clones. In the first year, carbon export from sylleptic branches increased over the growing season, and they export primarily toward the lower stem and roots. In the second year, important differences in translocation efficiency occurred among branch types with the sylleptic branches contributing more than proleptic branches, on a per unit mass basis, to the growth of the tree. Transport patterns, within branches and among branches of different order, were similar to those in the main stem, with phenology playing an important role in controlling the sink activity of the apical portion of the growing axis. Exchange of photosynthates between adjacent branches of the same order or between branches and main stem leaves are minimal, supporting an hypothesis of branch autonomy. 29 refs., 5 tabs., 4 figs.

Ozone induced leaf loss and decreased leaf production of European Holly (Ilex aquifolium L.) over multiple seasons

International Nuclear Information System (INIS)

Ranford, Jonathan; Reiling, Kevin

2007-01-01

European Holly (Ilex aquifolium L.) was used to study the impact of one short (28 day) ozone fumigation episode on leaf production, leaf loss and stomatal conductance (g s ), in order to explore potential longer term effects over 3 growing seasons. Young I. aquifolium plants received an episode of either charcoal-filtered air or charcoal-filtered air with 70 nl l -1 O 3 added for 7 h d -1 over a 28 day period from June 15th 1996, then placed into ambient environment, Stoke-on-Trent, U.K. Data were collected per leaf cohort over the next three growing seasons. Ozone exposure significantly increased leaf loss and stomatal conductance and reduced leaf production over all subsequent seasons. Impact of the initial ozone stress was still detected in leaves that had no direct experimental ozone exposure. This study has shown the potential of ozone to introduce long-term phenological perturbations into ecosystems by influencing productivity over a number of seasons. - Ozone significantly alters Ilex aquifolium leaf production and loss over multiple seasons

Short-term community dynamics in seasonal and hyperseasonal cerrados

Directory of Open Access Journals (Sweden)

MV. Cianciaruso

Full Text Available In South America, the largest seasonal savanna region is the Brazilian cerrado. Our aim was to study temporal changes in some community descriptors, such as floristic composition, richness, species density, plant density, and cylindrical volume, in a seasonal cerrado, comparing it to a nearby hyperseasonal cerrado. In four different seasons, we placed randomly ten 1 m² quadrats in each vegetation form and sampled all the vascular plants. Seasonal changes in floristic composition, species density, and plant density were less pronounced in the seasonal than in the hyperseasonal cerrado. Floristic similarity between the vegetation forms was lower when the hyperseasonal cerrado was waterlogged. Richness and species density were higher in the seasonal cerrado, which reached its biomass peak at mid rainy season. The hyperseasonal cerrado, in turn, reached its biomass peak at early rainy season and, despite the waterlogging, maintained it until late rainy season. In the hyperseasonal cerrado, waterlogging acts as an environmental filter restricting the number of cerrado species able to withstand it. The seasonal cerrado community was more stable than the hyperseasonal one. Our results corroborated the idea that changes in the environmental filters will affect floristic composition and community structure in savannas.

Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya - Coping with the Impacts of Climate Variability.

Science.gov (United States)

Sennhenn, Anne; Njarui, Donald M G; Maass, Brigitte L; Whitbread, Anthony M

2017-01-01

Climate variability is the major risk to agricultural production in semi-arid agroecosystems and the key challenge to sustain farm livelihoods for the 500 million people who inhabit these areas worldwide. Short-season grain legumes have great potential to address this challenge and help to design more resilient and productive farming systems. However, grain legumes display a great diversity and differ widely in growth, development, and resource use efficiency. Three contrasting short season grain legumes common bean ( Phaseolus vulgaris L.), cowpea ( Vigna unguiculata (L.) Walp.] and lablab [ Lablab purpureus (L.) Sweet] were selected to assess their agricultural potential with respect to climate variability and change along the Machakos-Makueni transect in semi-arid Eastern Kenya. This was undertaken using measured data [a water response trial conducted during 2012/13 and 2013/14 in Machakos, Kenya] and simulated data using the Agricultural Production System sIMulator (APSIM). The APSIM crop model was calibrated and validated to simulate growth and development of short-season grain legumes in semi-arid environments. Water use efficiency (WUE) was used as indicator to quantify the production potential. The major traits of adaptation include early flowering and pod and seed set before the onset of terminal drought. Early phenology together with adapted canopy architecture allowed more optimal water use and greater partitioning of dry matter into seed (higher harvest index). While common bean followed a comparatively conservative strategy of minimizing water loss through crop transpiration, the very short development time and compact growth habit limited grain yield to rarely exceed 1,000 kg ha -1 . An advantage of this strategy was relatively stable yields independent of in-crop rainfall or season length across the Machakos-Makueni transect. The growth habit of cowpea in contrast minimized water loss through soil evaporation with rapid ground cover and dry matter

A GIS TOOL TO EVALUATE THE SPATIAL EVOLUTION OF HYDRO-THERMIC FEATURES DURING GROWING SEASON OF VEGETABLE CROPS IN ELBE RIVER LOWLAND (POLABI

Directory of Open Access Journals (Sweden)

VERA POTOP

2012-11-01

Full Text Available A GIS tool to evaluate the spatial evolution of hydro-thermic features during growing season of vegetable crops in Elbe River lowland (Polabi. This article presents the results of the first study on combined mezoclimatological, microclimatological and topographical tools for evaluating precision farming in the growth of vegetable crops in the Elbe River lowland (Polabi region from the Czech Republic. We assess the variability of basically climatological characteristics in relation to topographic characteristics at the regional (Polabi and local (agricultural farm scales. At regional scale, interpolation approach is based on local linear regression and universal kriging interpolation. At local scale, two conventional interpolation methods, spline and local ordinary kriging with a Gaussian model variance across the fields, were applied. The local spline interpolators have been used in developing digital elevation models (DEMs and to determine the slope angle inclination of vegetable fields. The DEMs of the vegetable crops fields was developed at a 10 m x 10 m resolution based on elevation data collected in the field by a hand-held RTK- Global Positioning System receiver. This tool allowed the distinction of microclimatic conditions that produce altitude-slope-related patterns of the spatial-temporal distribution of the basic meteorological elements during growing season of vegetable crops. The effect of slope on diurnal extreme temperatures in the vegetable cropped field conditions was more pronounced than that of elevation. Accordingly to developed maps, the warmest and longest duration of sunshine, and the least precipitation totals during growing season occurred in the middle part of Polabi.

Projections for the changes in growing season length of tree-ring formation on the Tibetan Plateau based on CMIP5 model simulations.

Science.gov (United States)

He, Minhui; Yang, Bao; Shishov, Vladimir; Rossi, Sergio; Bräuning, Achim; Ljungqvist, Fredrik Charpentier; Grießinger, Jussi

2018-04-01

The response of the growing season to the ongoing global warming has gained considerable attention. In particular, how and to which extent the growing season will change during this century is essential information for the Tibetan Plateau, where the observed warming trend has exceeded the global mean. In this study, the 1960-2014 mean length of the tree-ring growing season (LOS) on the Tibetan Plateau was derived from results of the Vaganov-Shashkin oscilloscope tree growth model, based on 20 composite study sites and more than 3000 trees. Bootstrap and partial correlations were used to evaluate the most significant climate factors determining the LOS in the study region. Based on this relationship, we predicted the future variability of the LOS under three emission scenarios (Representative Concentration Pathways (RCP) 2.6, 6.0, and 8.5, representing different concentrations of greenhouse gasses) derived from 17 Earth system models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). The averaged LOS on the Tibetan Plateau is 103 days during the period 1960-2014, and April-September minimum temperature is the strongest factor controlling the LOS. We detected a general increase in the LOS over the twenty-first century under all the three selected scenarios. By the middle of this century, LOS will extend by about 3 to 4 weeks under the RCPs 2.6 and 6.0, and by more than 1 month (37 days) under the RCP 8.5, relative to the baseline period 1960-2014. From the middle to the end of the twenty-first century, LOS will further extend by about 3 to 4 weeks under the RCPs 6.0 and 8.5, respectively. Under the RCP 2.6 scenario, however, the extension reaches a plateau at around 2050 and about 2 weeks LOS extension. In total, we found an average rate of 2.1, 3.6, and 5.0 days decade -1 for the LOS extension from 2015 to 2100 under the RCPs 2.6, 6.0, and 8.5, respectively. However, such estimated LOS extensions may be offset by other ecological

Free-air CO2 enrichment (FACE) enhances biomass production in a short-rotation poplar plantation

International Nuclear Information System (INIS)

Calfapietra, C.; De Angelis, P.; Scarascia-Mungozza, G.; Gielen, B.; Ceulemans, R.; Galema, A. N. J.; Lukac, M.; Moscatelli, M. C.

2003-01-01

The possible contribution of short rotation cultures (SRC) to carbon sequestration in both current and elevated carbon dioxide concentrations was investigated using the free-air carbon dioxide enrichment (FACE) technique. Three poplar species were grown in an SRC plantation for three growing seasons. Above-ground and below-ground biomass increased by 15 to 27 per cent and by 22 to 38 per cent, respectively; light-efficiency also increased as a result. Depletion of inorganic nitrogen from the soil increased after three growing seasons at elevated carbon dioxide levels, but carbon dioxide showed no effect on stem wood density. Stem wood density also differed significantly from species to species. These results confirmed inter-specific differences in biomass production in poplar, and demonstrated that elevated carbon dioxide enhanced biomass productivity and light-use efficiency of a poplar short rotation cultivation ecosystem without changing biomass allocation. The reduction in soil nitrogen raises the possibility of reduced long-term biomass productivity. 60 refs., 4 tabs., 4 figs

Assessment of drought during corn growing season in Northeast China

Science.gov (United States)

Zhang, Qi; Hu, Zhenghua

2018-04-01

Northeast China has experienced extensive climate change during the past decades. Corn is the primary production crop in China and is sensitive to meteorological disasters, especially drought. Drought has thus greatly endangered crop production and the country's food security. The majority of previous studies has not highlighted farming adaptation activities undertaken within the changed climate, which should not be neglected. In this study, we assessed drought hazard in the corn vegetation growing period, the reproductive growing period, and the whole growing period based on data for yearly corn phenology, daily precipitation, and temperature gathered at 26 agro-meteorological stations across Northeast China from 1981 to 2009. The M-K trend test was used to detect trends in sowing date and drought. The standardized precipitation evapotranspiration index (SPEI) was used to describe drought. Drought frequency and intensity were used to assess the drought hazard in the region. We found that the sowing date was delayed in the southern part of the study area, coupled with a trend towards a shorter and more humid vegetation growing period. In the northern part of the study area, an earlier sowing date increased the length of the vegetation growing period and the reproductive growing period, while drying trends occurred within the two corn growing periods. We assessed the drought hazard during each growing period: the reproductive growing period faced a more severe drought hazard and was also the period where corn was most sensitive to water stress. Drought hazard during the total growing period was closely related to corn yield.

Effects of repeated growing season prescribed fire on the structure and composition of pine-hardwood forests in the southeastern Piedmont, USA

Science.gov (United States)

Matthew Reilly; Kenneth Outcalt; Joseph O’Brien; Dale Wade

2016-01-01

We examined the effects of repeated growing season prescribed fire on the structure and composition of mixed pine–hardwood forests in the southeastern Piedmont region, Georgia, USA. Plots were burned two to four times over an eight-year period with low intensity surface fires during one of four six-week long periods from early April to mid-September. Density...

Growing container seedlings: Three considerations

Science.gov (United States)

Kas Dumroese; Thomas D. Landis

2015-01-01

The science of growing reforestation and conservation plants in containers has continually evolved, and three simple observations may greatly improve seedling quality. First, retaining stock in its original container for more than one growing season should be avoided. Second, strongly taprooted species now being grown as bareroot stock may be good candidates...

Short-term forecasting of non-OPEC supply: a test of seasonality and seasonal decomposition

International Nuclear Information System (INIS)

Jazayeri, S.M.R.T.; Yahyai, A.

2002-01-01

The purpose of this study is, first to find out, based on historical data, whether quarterly averages of non-OPEC supply follow a seasonal pattern. If that is mathematically established, then, secondly, it is attempted to estimate the best seasonal factors to decompose the estimated yearly average into seasonal averages. This study applies the Fourier analysis to quarterly supply series to test for seasonality, and provides estimates of seasonal factors for the year 2001 by applying the so-called X-11 decomposition method to the annual estimate. A set of historical data, consisting of quarterly supply averages of individual countries, regional subtotals and aggregate non-OPEC for the period 1971-2000, forms the basis of the analysis. Through the application of the Fourier analysis and X-11 decomposition method, it is demonstrated that quarterly non-OPEC supply, be it by an individual major producer or regional sub-totals, clearly follows a seasonal pattern. This is a very useful conclusion for the market analyst involved with forecasting the quarterly supply. (author)

Contrasting seasonal overlaps between primary and secondary growth are linked to wood anatomy in Mediterranean sub-shrubs.

Science.gov (United States)

Camarero, J J; Palacio, S; Montserrat-Martí, G

2013-09-01

Whole-plant approaches allow quantification of the temporal overlap between primary and secondary growth. If the amount of time available to grow is short, there may be a high temporal overlap between shoot growth and wood formation. We hypothesise that such overlap depends on the duration of the growing season and relates to wood anatomy. We evaluated wood anatomy, shoot longitudinal and radial growth rates, fine root production and the concentrations of non-structural carbohydrates (NSC) in the wood of six sub-shrub species growing in sites with contrasting climatic conditions (Lepidium subulatum, Linum suffruticosum, Salvia lavandulifolia, Satureja montana, Ononis fruticosa, Echinospartum horridum). Sub-shrub species living in sites with a short growing season displayed a high overlap between aboveground primary and secondary growth and formed wide vessels, whereas species from the warmest and driest sites presented the reverse characteristics. The highest overlap was linked to a rapid shoot extension and thickening through the enhanced hydraulic conductivity provided by wide vessels. The reductions in NSC concentrations when growth peaked were low or moderate, indicating that sub-shrubs accumulate NSC in excess, as do trees. The temporal overlap among primary and secondary growth in woody plants may be connected to the duration and rates of shoot and wood growth, which in turn depend on the vessel lumen area. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya — Coping with the Impacts of Climate Variability

Directory of Open Access Journals (Sweden)

Anne Sennhenn

2017-05-01

Full Text Available Climate variability is the major risk to agricultural production in semi-arid agroecosystems and the key challenge to sustain farm livelihoods for the 500 million people who inhabit these areas worldwide. Short-season grain legumes have great potential to address this challenge and help to design more resilient and productive farming systems. However, grain legumes display a great diversity and differ widely in growth, development, and resource use efficiency. Three contrasting short season grain legumes common bean (Phaseolus vulgaris L., cowpea (Vigna unguiculata (L. Walp.] and lablab [Lablab purpureus (L. Sweet] were selected to assess their agricultural potential with respect to climate variability and change along the Machakos-Makueni transect in semi-arid Eastern Kenya. This was undertaken using measured data [a water response trial conducted during 2012/13 and 2013/14 in Machakos, Kenya] and simulated data using the Agricultural Production System sIMulator (APSIM. The APSIM crop model was calibrated and validated to simulate growth and development of short-season grain legumes in semi-arid environments. Water use efficiency (WUE was used as indicator to quantify the production potential. The major traits of adaptation include early flowering and pod and seed set before the onset of terminal drought. Early phenology together with adapted canopy architecture allowed more optimal water use and greater partitioning of dry matter into seed (higher harvest index. While common bean followed a comparatively conservative strategy of minimizing water loss through crop transpiration, the very short development time and compact growth habit limited grain yield to rarely exceed 1,000 kg ha−1. An advantage of this strategy was relatively stable yields independent of in-crop rainfall or season length across the Machakos-Makueni transect. The growth habit of cowpea in contrast minimized water loss through soil evaporation with rapid ground cover and

Exploring Niches for Short-Season Grain Legumes in Semi-Arid Eastern Kenya — Coping with the Impacts of Climate Variability

Science.gov (United States)

Sennhenn, Anne; Njarui, Donald M. G.; Maass, Brigitte L.; Whitbread, Anthony M.

2017-01-01

Climate variability is the major risk to agricultural production in semi-arid agroecosystems and the key challenge to sustain farm livelihoods for the 500 million people who inhabit these areas worldwide. Short-season grain legumes have great potential to address this challenge and help to design more resilient and productive farming systems. However, grain legumes display a great diversity and differ widely in growth, development, and resource use efficiency. Three contrasting short season grain legumes common bean (Phaseolus vulgaris L.), cowpea (Vigna unguiculata (L.) Walp.] and lablab [Lablab purpureus (L.) Sweet] were selected to assess their agricultural potential with respect to climate variability and change along the Machakos-Makueni transect in semi-arid Eastern Kenya. This was undertaken using measured data [a water response trial conducted during 2012/13 and 2013/14 in Machakos, Kenya] and simulated data using the Agricultural Production System sIMulator (APSIM). The APSIM crop model was calibrated and validated to simulate growth and development of short-season grain legumes in semi-arid environments. Water use efficiency (WUE) was used as indicator to quantify the production potential. The major traits of adaptation include early flowering and pod and seed set before the onset of terminal drought. Early phenology together with adapted canopy architecture allowed more optimal water use and greater partitioning of dry matter into seed (higher harvest index). While common bean followed a comparatively conservative strategy of minimizing water loss through crop transpiration, the very short development time and compact growth habit limited grain yield to rarely exceed 1,000 kg ha−1. An advantage of this strategy was relatively stable yields independent of in-crop rainfall or season length across the Machakos-Makueni transect. The growth habit of cowpea in contrast minimized water loss through soil evaporation with rapid ground cover and dry matter

Changes in growth rate and macroelement and trace element accumulation in Hydrocharis morsus-ranae L. during the growing season in relation to environmental contamination.

Science.gov (United States)

Polechońska, Ludmiła; Samecka-Cymerman, Aleksandra; Dambiec, Małgorzata

2017-02-01

The temporal variations in plant chemistry connected with its life cycle may affect the cycling of elements in an ecosystem as well as determine the usefulness of the species in phytoremediation and bioindication. In this context, there is a gap in knowledge on the role of floating plants for elements cycling in aquatic reservoirs. The aim of the study was to determine if there are variations in Hydrocharis morsus-ranae (European frog-bit) bioaccumulation capacity and the growth rate of its population during the growing season and to test the impact of environmental pollution on these features. The content of macroelements (Ca, K, Mg, N, Na, P, S) and trace metals (Cd, Co, Cu, Cr, Hg, Fe, Mn, Ni, Pb, Zn) was determined in H. morsus-ranae collected monthly from June to October from habitats differing in environmental contamination. The results showed that the highest content of most trace metals (Co, Cr, Cu, Hg, Mn, Ni, Zn) and some nutrients (N, P) in plants as well as the greatest bioaccumulation efficiency occurred simultaneously in the beginning of the growing season. In the following months, a dilution effect (manifested by a decrease in content) related to the rapid growth was observed. Co, Mn, and Ni content in plant tissues reflected the level of environmental contamination throughout the growing season which makes H. morsus-ranae a potential biomonitor of pollution for these metals. Considering the great bioaccumulation ability, high sensitivity to contamination, and low biomass of European frog-bit in polluted systems, further investigation is required to assess the real phytoremediation capability of the species.

Sphagnum-dwelling testate amoebae in subarctic bogs are more sensitive to soil warming in the growing season than in winter: the results of eight-year field climate manipulations.

Science.gov (United States)

Tsyganov, Andrey N; Aerts, Rien; Nijs, Ivan; Cornelissen, Johannes H C; Beyens, Louis

2012-05-01

Sphagnum-dwelling testate amoebae are widely used in paleoclimate reconstructions as a proxy for climate-induced changes in bogs. However, the sensitivity of proxies to seasonal climate components is an important issue when interpreting proxy records. Here, we studied the effects of summer warming, winter snow addition solely and winter snow addition together with spring warming on testate amoeba assemblages after eight years of experimental field climate manipulations. All manipulations were accomplished using open top chambers in a dry blanket bog located in the sub-Arctic (Abisko, Sweden). We estimated sensitivity of abundance, diversity and assemblage structure of living and empty shell assemblages of testate amoebae in the living and decaying layers of Sphagnum. Our results show that, in a sub-arctic climate, testate amoebae are more sensitive to climate changes in the growing season than in winter. Summer warming reduced species richness and shifted assemblage composition towards predominance of xerophilous species for the living and empty shell assemblages in both layers. The higher soil temperatures during the growing season also decreased abundance of empty shells in both layers hinting at a possible increase in their decomposition rates. Thus, although possible effects of climate changes on preservation of empty shells should always be taken into account, species diversity and structure of testate amoeba assemblages in dry subarctic bogs are sensitive proxies for climatic changes during the growing season. Copyright © 2011 Elsevier GmbH. All rights reserved.

Seasonal prolactin secretion and its role in seasonal reproduction: a review.

Science.gov (United States)

Curlewis, J D

1992-01-01

The majority of seasonally breeding mammals show a seasonal pattern of prolactin secretion with peak concentrations in spring or summer and a nadir in autumn or winter. Photoperiod influences prolactin secretion via its effects on the secretion of the pineal hormone melatonin. Preliminary evidence suggests that the effects of melatonin on both prolactin and gonadotrophin secretion are via a common target area, possibly within the anterior hypothalamus, and that differences in response to photoperiod may be due to differences in the processing and/or interpretation of the melatonin signal. In contrast to seasonal gonadotrophin secretion, the seasonal changes in prolactin are not due to changes in the sensitivity of a feedback loop and so must be due to direct effects on the hypothalamic pathways that control prolactin secretion. Little else can be said with confidence about the neuroendocrine mechanisms that lead to the seasonal changes in prolactin secretion. Dopamine and noradrenaline turnover in the arcuate nucleus and median eminence decrease under short daylength. If catecholamine turnover in these structures is positively correlated with catecholamine concentrations in the long or short hypophysial portal vessels, it is unlikely that the decrease in prolactin concentration in winter is due to the effects of increased concentrations of dopamine or noradrenaline in the portal vessels. There is, however, evidence for increased pituitary sensitivity to dopamine under short daylength, so increased dopamine concentrations may not be required for suppression of prolactin secretion at this time. In addition to the diminished secretion of prolactin under short daylength, rate of prolactin synthesis and pituitary content of prolactin also decline although the mechanisms that regulate these changes are poorly understood. Although all seasonal breeders show a seasonal change in prolactin secretion, there are continuously breeding species in which prolactin secretion is

Performance of machinery in potato production in one growing season

Directory of Open Access Journals (Sweden)

Kun Zhou

2015-12-01

Full Text Available Statistics on the machinery performance are essential for farm managers to make better decisions. In this paper, the performance of all machineries in five sequential operations, namely bed forming, stone separation, planting, spraying and harvesting in the potato production system, were investigated during one growing season. In order to analyse and decompose the recorded GPS data into various time and distance elements for estimation of the machinery performance, an automatic GPS analysis tool was developed. The field efficiency and field capacity were estimated for each operation. Specifically, the measured average field efficiency was 71.3% for bed forming, 68.5% for stone separation, 40.3% for planting, 69.7% for spraying, and 67.4% for harvesting. The measured average field capacities were 1.46 ha/h, 0.53 ha/h, 0.47 ha/h, 10.21 ha/h, 0.51 ha/h, for the bed forming, stone separation, planting, spraying, and harvesting operations, respectively. These results deviate from the corresponding estimations calculated based on norm data from the American Society of Agricultural and Biological Engineers (ASABE. The deviations indicate that norms provided by ASABE cannot be used directly for the prediction of performance of the machinery used in this work. Moreover, the measured data of bed forming and stone separation could be used as supplementary data for the ASABE which does not provide performance norms for these two operations. The gained results can help farm managers to make better management and operational decisions that result in potential improvement in productivity and profitability as well as in potential environmental benefits.

Performance of machinery in potato production in one growing season

Energy Technology Data Exchange (ETDEWEB)

Zhou, K.; Jensen, A.L.; Bochtis, D.D.; Sørensen, C.G.

2015-07-01

Statistics on the machinery performance are essential for farm managers to make better decisions. In this paper, the performance of all machineries in five sequential operations, namely bed forming, stone separation, planting, spraying and harvesting in the potato production system, were investigated during one growing season. In order to analyse and decompose the recorded GPS data into various time and distance elements for estimation of the machinery performance, an automatic GPS analysis tool was developed. The field efficiency and field capacity were estimated for each operation. Specifically, the measured average field efficiency was 71.3% for bed forming, 68.5% for stone separation, 40.3% for planting, 69.7% for spraying, and 67.4% for harvesting. The measured average field capacities were 1.46 ha/h, 0.53 ha/h, 0.47 ha/h, 10.21 ha/h, 0.51 ha/h, for the bed forming, stone separation, planting, spraying, and harvesting operations, respectively. These results deviate from the corresponding estimations calculated based on norm data from the American Society of Agricultural and Biological Engineers (ASABE). The deviations indicate that norms provided by ASABE cannot be used directly for the prediction of performance of the machinery used in this work. Moreover, the measured data of bed forming and stone separation could be used as supplementary data for the ASABE which does not provide performance norms for these two operations. The gained results can help farm managers to make better management and operational decisions that result in potential improvement in productivity and profitability as well as in potential environmental benefits. (Author)

Effects of urban green infrastructure (UGI) on local outdoor microclimate during the growing season.

Science.gov (United States)

Wang, Yafei; Bakker, Frank; de Groot, Rudolf; Wörtche, Heinrich; Leemans, Rik

2015-12-01

This study analyzed how the variations of plant area index (PAI) and weather conditions alter the influence of urban green infrastructure (UGI) on microclimate. To observe how diverse UGIs affect the ambient microclimate through the seasons, microclimatic data were measured during the growing season at five sites in a local urban area in The Netherlands. Site A was located in an open space; sites B, C, and D were covered by different types and configurations of green infrastructure (grove, a single deciduous tree, and street trees, respectively); and site E was adjacent to buildings to study the effects of their façades on microclimate. Hemispherical photography and globe thermometers were used to quantify PAI and thermal comfort at both shaded and unshaded locations. The results showed that groves with high tree density (site B) have the strongest effect on microclimate conditions. Monthly variations in the differences of mean radiant temperature (∆Tmrt) between shaded and unshaded areas followed the same pattern as the PAI. Linear regression showed a significant positive correlation between PAI and ∆Tmrt. The difference of daily average air temperature (∆T a ) between shaded and unshaded areas was also positively correlated to PAI, but with a slope coefficient below the measurement accuracy (±0.5 °C). This study showed that weather conditions can significantly impact the effectiveness of UGI in regulating microclimate. The results of this study can support the development of appropriate UGI measures to enhance thermal comfort in urban areas.

Impact of mulches and growing season on indicator bacteria survival during lettuce cultivation.

Science.gov (United States)

Xu, Aixia; Buchanan, Robert L; Micallef, Shirley A

2016-05-02

In fresh produce production, the use of mulches as ground cover to retain moisture and control weeds is a common agricultural practice, but the influence that various mulches have on enteric pathogen survival and dispersal is unknown. The goal of this study was to assess the impact of different mulching methods on the survival of soil and epiphytic fecal indicator bacteria on organically grown lettuce during different growing seasons. Organically managed lettuce, cultivated with various ground covers--polyethylene plastic, corn-based biodegradable plastic, paper and straw mulch--and bare ground as a no-mulch control, was overhead inoculated with manure-contaminated water containing known levels of generic Escherichia coli and Enterococcus spp. Leaves and soil samples were collected at intervals over a two week period on days 0, 1, 3, 5, 7, 10 and 14, and quantitatively assessed for E. coli, fecal coliforms and Enterococcus spp. Data were analyzed using mixed models with repeated measures and an exponential decline with asymptote survival model. Indicator bacterial concentrations in the lettuce phyllosphere decreased over time under all treatments, with more rapid E. coli declines in the fall than in the spring (plettuce compared to mulches. In fall 2014, the E. coli decline rate on paper mulch-grown lettuce was higher (plettuce phyllosphere, and mulch type was a factor for fecal coliform levels (plettuce production may impact the fate of enteric bacteria in soil or on lettuce, most likely in relation to soil moisture retention, and other weather-related factors, such as temperature and rainfall. The data suggest that the time between exposure to a source of enteric bacteria and harvesting of the crop is season dependent, which has implications for determining best harvest times. Copyright © 2016 Elsevier B.V. All rights reserved.

Regional and seasonal analyses of weights in growing Angus cattle.

Science.gov (United States)

Bradford, H L; Fragomeni, B O; Bertrand, J K; Lourenco, D A L; Misztal, I

2016-10-01

This study evaluated the impact of region and season on growth in Angus seed stock. To assess geographic differences, the United States was partitioned into 9 regions based on similar climate and topography related to cow-calf production. Seasonal effects were associated with the month that animals were weighed. The American Angus Association provided growth data, and records were assigned to regions based on the owner's zip code. Most Angus cattle were in the Cornbelt, Lower Plains, Rocky Mountain, Upper Plains, and Upper South regions, with proportionally fewer Angus in Texas compared with the national cow herd. Most calves were born in the spring, especially February and March. Weaning weights (WW; = 49,886) and yearling weights (YW; = 45,168) were modeled with fixed effects of age-of-dam class (WW only), weigh month, region, month-region interaction, and linear covariate of age. Random effects included contemporary group nested within month-region combination and residual. The significant month-region interaction ( Angus seed stock producers have used calving seasons to adapt to the specific environmental conditions in their regions and to optimize growth in young animals.

Growth form and seasonal variation in leaf gas exchange of Colophospermum mopane savanna trees in northwest Botswana.

Science.gov (United States)

Veenendaal, Elmar M; Mantlana, Khanyisa B; Pammenter, Norman W; Weber, Piet; Huntsman-Mapila, Phillipa; Lloyd, Jon

2008-03-01

We investigated differences in physiological and morphological traits between the tall and short forms of mopane (Colophospermum mopane (Kirk ex Benth.) Kirk ex J. Léonard) trees growing near Maun, Botswana on a Kalahari sandveld overlying an impermeable calcrete duricrust. We sought to determine if differences between the two physiognomic types are attributable to the way they exploit available soil water. The tall form, which was located on deeper soil than the short form (5.5 versus 1.6 m), had a lower leaf:fine root biomass ratio (1:20 versus 1:6), but a similar leaf area index (0.9-1.0). Leaf nitrogen concentrations varied between 18 and 27 mg g(-1) and were about 20% higher in the tall form than in the short form. Maximum net assimilation rates (A sat) occurred during the rainy seasons (March-April 2000 and January-February 2001) and were similar in the tall and short forms (15-22 micromol m(-2) s(-1)) before declining to less than 10 micromol m(-2) s(-1) at the end of the rainy season in late April. As the dry season progressed, A sat, soil water content, predawn leaf water potential (Psi pd) and leaf nitrogen concentration declined rapidly. Before leaf abscission, Psi pd was more negative in the short form (-3.4 MPa) than in the tall form (-2.7 MPa) despite the greater availability of soil water beneath the short form trees. This difference appeared attributable to differences in root depth and density between the physiognomic types. Stomatal regulation of water use and carbon assimilation differed between years, with the tall form having a consistently more conservative water-use strategy as the dry season progressed than the short form.

Drivers of seasonality in Arctic carbon dioxide fluxes

DEFF Research Database (Denmark)

Mbufong, Herbert Njuabe

, while there were no discernable drivers of CO2 fluxes in Stordalen, growing season length showed significant controls on net ecosystem exchange (NEE) in Zackenberg and with gross primary production (GPP) and ecosystem respiration (Re) in Daring Lake. This is important considering the recent observations...... compensates for the shorter growing season due to increase snow cover and duration. Other drivers of growing season CO2 fluxes were mainly air temperature, growing degree days and photosynthetic active radiation in a high and a low Arctic tundra ecosystem. Upscaling Arctic tundra NEE based on an acquired...... understanding of the drivers of NEE during this research venture, shows an estimation of reasonable fluxes at three independent sites in low Arctic Alaska. However, this later project is still ongoing and its findings are only preliminary....

Seasonal trends of biogenic terpene emissions.

Science.gov (United States)

Helmig, Detlev; Daly, Ryan Woodfin; Milford, Jana; Guenther, Alex

2013-09-01

Biogenic volatile organic compound (BVOC) emissions from six coniferous tree species, i.e. Pinus ponderosa (Ponderosa Pine), Picea pungens (Blue Spruce), Pseudotsuga menziesii (Rocky Mountain Douglas Fir) and Pinus longaeva (Bristlecone Pine), as well as from two deciduous species, Quercus gambelii (Gamble Oak) and Betula occidentalis (Western River Birch) were studied over a full annual growing cycle. Monoterpene (MT) and sesquiterpene (SQT) emissions rates were quantified in a total of 1236 individual branch enclosure samples. MT dominated coniferous emissions, producing greater than 95% of BVOC emissions. MT and SQT demonstrated short-term emission dependence with temperature. Two oxygenated MT, 1,8-cineol and piperitone, were both light and temperature dependent. Basal emission rates (BER, normalized to 1000μmolm(-2)s(-1) and 30°C) were generally higher in spring and summer than in winter; MT seasonal BER from the coniferous trees maximized between 1.5 and 6.0μgg(-1)h(-1), while seasonal lows were near 0.1μgg(-1)h(-1). The fractional contribution of individual MT to total emissions was found to fluctuate with season. SQT BER measured from the coniferous trees ranged from emissions modeling, was not found to exhibit discernible growth season trends. A seasonal correction factor proposed by others in previous work to account for a sinusoidal shaped emission pattern was applied to the data. Varying levels of agreement were found between the data and model results for the different plant species seasonal data sets using this correction. Consequently, the analyses on this extensive data set suggest that it is not feasible to apply a universal seasonal correction factor across different vegetation species. A modeling exercise comparing two case scenarios, (1) without and (2) with consideration of the seasonal changes in emission factors illustrated large deviations when emission factors are applied for other seasons than those in which they were experimentally

Short-term to seasonal variability in factors driving primary productivity in a shallow estuary: Implications for modeling production

Science.gov (United States)

Canion, Andy; MacIntyre, Hugh L.; Phipps, Scott

2013-10-01

The inputs of primary productivity models may be highly variable on short timescales (hourly to daily) in turbid estuaries, but modeling of productivity in these environments is often implemented with data collected over longer timescales. Daily, seasonal, and spatial variability in primary productivity model parameters: chlorophyll a concentration (Chla), the downwelling light attenuation coefficient (kd), and photosynthesis-irradiance response parameters (Pmchl, αChl) were characterized in Weeks Bay, a nitrogen-impacted shallow estuary in the northern Gulf of Mexico. Variability in primary productivity model parameters in response to environmental forcing, nutrients, and microalgal taxonomic marker pigments were analysed in monthly and short-term datasets. Microalgal biomass (as Chla) was strongly related to total phosphorus concentration on seasonal scales. Hourly data support wind-driven resuspension as a major source of short-term variability in Chla and light attenuation (kd). The empirical relationship between areal primary productivity and a combined variable of biomass and light attenuation showed that variability in the photosynthesis-irradiance response contributed little to the overall variability in primary productivity, and Chla alone could account for 53-86% of the variability in primary productivity. Efforts to model productivity in similar shallow systems with highly variable microalgal biomass may benefit the most by investing resources in improving spatial and temporal resolution of chlorophyll a measurements before increasing the complexity of models used in productivity modeling.

Nonvascular contribution to ecosystem NPP in a subarctic heath during early and late growing season

DEFF Research Database (Denmark)

Campioli, Matteo; Samson, Roeland; Michelsen, Anders

2009-01-01

significant when vascular plants are less active and ecosystems act as a source of carbon (C). To clarify these dynamics, nonvascular and vascular aboveground NPP was compared for a subarctic heath during two contrasting periods of the growing season, viz. early-mid summer and late summer-early autumn...... measurements of shoot length increase. Vascular NPP was determined by harvesting shrub and herb apical growth and considering production due to stem secondary growth of shrubs. Hylocomium splendens and Pleurozium schreberi showed highest biomass growth in late summer, whereas for D. elongatum this occurred...... weight m-2 d-1, in early and late summer, respectively, whereas in the same periods vascular NPP was 3.6 and 1.1 g dry weight m-2 d-1. The contribution of nonvascular NPP to total aboveground NPP was therefore minor in early summer but substantial in late summer, when 25% of the C accumulated...

Monitoring of a fast-growing speleothem site from the Han-sur-Lesse cave, Belgium, indicates equilibrium deposition of the seasonal δ18O and δ13C signals in the calcite

Science.gov (United States)

Van Rampelbergh, M.; Verheyden, S.; Allan, M.; Quinif, Y.; Keppens, E.; Claeys, P.

2014-10-01

Speleothems provide paleoclimate information on multimillennial to decadal scales in the Holocene. However, seasonal or even monthly resolved records remain scarce. Such records require fast-growing stalagmites and a good understanding of the proxy system on very short timescales. The Proserpine stalagmite from the Han-sur-Less cave (Belgium) displays well-defined/clearly visible darker and lighter seasonal layers of 0.5 to 2 mm thickness per single layer, which allows a measuring resolution at a monthly scale. Through a regular cave monitoring, we acquired a good understanding of how δ18O and δ13C signals in modern calcite reflect climate variations on the seasonal scale. From December to June, outside temperatures are cold, inducing low cave air and water temperature, and bio-productivity in the soil is limited, leading to lower pCO2 and higher δ13C values of the CO2 in the cave air. From June to December, the measured factors display an opposite behavior. The absence of epikarst water recharge between May and October increases prior calcite precipitation (PCP) in the vadose zone, causing drip water to display increasing pH and δ13C values over the summer months. Water recharge of the epikarst in winter diminishes the effect of PCP and as a result the pH and δ13C of the drip water gradually decrease. The δ18O and δ13C signals of fresh calcite precipitated on glass slabs also vary seasonally and are both reflecting equilibrium conditions. Lowest δ18O values occur during the summer, when the δ13C values are high. The δ18O values of the calcite display seasonal variations due to changes in the cave air and water temperature. The δ13C values reflect the seasonal variation of the δ13CDIC of the drip water, which is affected by the intensity of PCP. This same anticorrelation of the δ18O versus the δ13C signals is seen in the monthly resolved speleothem record that covers the period between 1976 and 1985 AD. Dark layers display lower δ18O and higher δ13C

Phenology and carbon dioxide source/sink strength of a subalpine grassland in response to an exceptionally short snow season

International Nuclear Information System (INIS)

Galvagno, M; Cremonese, E; Filippa, G; Morra di Cella, U; Wohlfahrt, G; Rossini, M; Colombo, R; Julitta, T; Manca, G; Siniscalco, C; Migliavacca, M

2013-01-01

Changes in snow cover depth and duration predicted by climate change scenarios are expected to strongly affect high-altitude ecosystem processes. This study investigates the effect of an exceptionally short snow season on the phenology and carbon dioxide source/sink strength of a subalpine grassland. An earlier snowmelt of more than one month caused a considerable advancement (40 days) of the beginning of the carbon uptake period (CUP) and, together with a delayed establishment of the snow season in autumn, contributed to a two-month longer CUP. The combined effect of the shorter snow season and the extended CUP led to an increase of about 100% in annual carbon net uptake. Nevertheless, the unusual environmental conditions imposed by the early snowmelt led to changes in canopy structure and functioning, with a reduction of the carbon sequestration rate during the snow-free period. (letter)

Prediction of digestible and metabolizable energy content and standardized ileal amino Acid digestibility in wheat shorts and red dog for growing pigs.

Science.gov (United States)

Huang, Q; Piao, X S; Ren, P; Li, D F

2012-12-01

Two experiments were conducted to evaluate the effects of chemical composition of wheat shorts and red dog on energy and amino acid digestibility in growing pigs and to establish prediction models to estimate their digestible (DE) and metabolizable (ME) energy content and as well as their standardized ileal digestible (SID) amino acid content. For Exp. 1, sixteen diets were fed to thirty-two growing pigs according to a completely randomized design during three successive periods. The basal diet was based on corn and soybean meal while the other fifteen diets contained 28.8% wheat shorts (N = 7) or red dog (N = 8), added at the expense of corn and soybean meal. Over the three periods, each diet was fed to six pigs with each diet being fed to two pigs during each period. The apparent total tract digestibility (ATTD) of energy in wheat shorts and red dog averaged 75.1 and 87.9%. The DE values of wheat shorts and red dog averaged 13.8 MJ/kg (range 13.1 to 15.0 MJ/kg) and 15.1 MJ/kg (range 13.3 to 16.6 MJ/kg) of dry matter, respectively. For Exp. 2, twelve growing pigs were allotted to two 6×6 Latin Square Designs with six periods. Ten of the diets were formulated based on 60% wheat shorts or red dog and the remaining two diets were nitrogen-free diets based on cornstarch and sucrose. Chromic oxide (0.3%) was used as an indigestible marker in all diets. There were no differences (p>0.05) in SID values for the amino acids in wheat shorts and red dog except for lysine and methionine. Apparent ileal digestibility (AID) and SID values for lysine in different sources of wheat shorts or red dog, which averaged 78.1 and 87.8%, showed more variation than either methionine or tryptophan. A stepwise regression was performed to establish DE, ME and amino acid digestibility prediction models. Data indicated that fiber content and amino acid concentrations were good indicators to predict energy values and amino acid digestibility, respectively. The present study confirms the large

Downscaling 250-m MODIS growing season NDVI based on multiple-date landsat images and data mining approaches

Science.gov (United States)

Gu, Yingxin; Wylie, Bruce K.

2015-01-01

The satellite-derived growing season time-integrated Normalized Difference Vegetation Index (GSN) has been used as a proxy for vegetation biomass productivity. The 250-m GSN data estimated from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors have been used for terrestrial ecosystem modeling and monitoring. High temporal resolution with a wide range of wavelengths make the MODIS land surface products robust and reliable. The long-term 30-m Landsat data provide spatial detailed information for characterizing human-scale processes and have been used for land cover and land change studies. The main goal of this study is to combine 250-m MODIS GSN and 30-m Landsat observations to generate a quality-improved high spatial resolution (30-m) GSN database. A rule-based piecewise regression GSN model based on MODIS and Landsat data was developed. Results show a strong correlation between predicted GSN and actual GSN (r = 0.97, average error = 0.026). The most important Landsat variables in the GSN model are Normalized Difference Vegetation Indices (NDVIs) in May and August. The derived MODIS-Landsat-based 30-m GSN map provides biophysical information for moderate-scale ecological features. This multiple sensor study retains the detailed seasonal dynamic information captured by MODIS and leverages the high-resolution information from Landsat, which will be useful for regional ecosystem studies.

Growing short rotation coppice on agricultural land in Germany: A Real Options Approach

International Nuclear Information System (INIS)

Musshoff, Oliver

2012-01-01

In many cases decision-makers apparently do not adapt as fast as expected to changing economic conditions. This is also the case for the conversion of farm land to short rotation coppice. From an economic point of view, short rotation coppice has become more interesting in the last few years. Nevertheless, farm land still is rarely used to grow this quite unknown crop. Several explanatory approaches (e.g., traditionalistic behavior and risk aversion) are currently discussed in order to explain this behavior. A relatively new explanatory approach is the Real Options Approach. The Real Options Approach uses a comprehensive dynamic-stochastic model that combines the uncertainty of investment returns, the sunk costs, and the temporal flexibility of the investment implementation. The quintessence of the Real Options Approach is that—compared to the Classical Investment Theory—the investment triggers will be shifted upwards if investments involve intertemporal opportunity costs. This paper develops a real options model which allows the determination of triggers on the basis of realistic assumptions. We examined when farmers, who only dispose of sandy soils with little water-storing capacity, should convert set-aside land to short rotation coppice. The results show that farmers should not convert until the present value of the investment returns exceeds the investment costs considerably. Thus, they confirm the empirically observed reluctance in conversion. Furthermore, it turned out that the magnitude of the difference between the Classical Investment Theory and the Real Options Approach depends heavily on the type of stochastic process that underlies the investment returns. -- Highlights: ► Frequently observed reluctance of farmers to convert to short rotation coppice. ► Risk neutral farmers should convert if the investment multiple exceeds 1.57. ► The Real Options Approach is an explanatory approach for this observation. ► Results depend very much on the

Seasonal phenology of interactions involving short-lived annual plants, a multivoltine herbivore and its endoparasitoid wasp.

Science.gov (United States)

Fei, Minghui; Gols, Rieta; Harvey, Jeffrey A

2014-01-01

Spatial-temporal realism is often missing in many studies of multitrophic interactions, which are conducted at a single time frame and/or involving interactions between insects with a single species of plant. In this scenario, an underlying assumption is that the host-plant species is ubiquitous throughout the season and that the insects always interact with it. We studied interactions involving three naturally occurring wild species of cruciferous plants, Brassica rapa, Sinapis arvensis and Brassica nigra, that exhibit different seasonal phenologies, and a multivoltine herbivore, the large cabbage white butterfly, Pieris brassicae, and its gregarious endoparasitoid wasp, Cotesia glomerata. The three plants have very short life cycles. In central Europe, B. rapa grows in early spring, S. arvensis in late spring and early summer, and B. nigra in mid to late summer. P. brassicae generally has three generations per year, and C. glomerata at least two. This means that different generations of the insects must find and exploit different plant species that may differ in quality and which may be found some distance from one another. Insects were either reared on each of the three plant species for three successive generations or shifted between generations from B. rapa to S. arvensis to B. nigra. Development time from neonate to pupation and pupal fresh mass were determined in P. brassicae and egg-to-adult development time and body mass in C. glomerata. Overall, herbivores performed marginally better on S. arvensis and B. nigra plants than on B. rapa plants. Parasitoids performance was closely tailored with that of the host. Irrespective as to whether the insects were shifted to a new plant in successive generations or not, development time of P. brassicae and C. glomerata decreased dramatically over time. Our results show that there were some differences in insect development on different plant species and when transferred from one species to another. However, all three

Seasonal changes in the assembly mechanisms structuring tropical fish communities.

Science.gov (United States)

Fitzgerald, Daniel B; Winemiller, Kirk O; Sabaj Pérez, Mark H; Sousa, Leandro M

2017-01-01

Despite growing interest in trait-based approaches to community assembly, little attention has been given to seasonal variation in trait distribution patterns. Mobile animals can rapidly mediate influences of environmental factors and species interactions through dispersal, suggesting that the relative importance of different assembly mechanisms can vary over short time scales. This study analyzes seasonal changes in functional trait distributions of tropical fishes in the Xingu River, a major tributary of the Amazon with large predictable temporal variation in hydrologic conditions and species density. Comparison of observed functional diversity revealed that species within wet-season assemblages were more functionally similar than those in dry-season assemblages. Further, species within wet-season assemblages were more similar than random expectations based on null model predictions. Higher functional richness within dry season communities is consistent with increased niche complementarity during the period when fish densities are highest and biotic interactions should be stronger; however, null model tests suggest that stochastic factors or a combination of assembly mechanisms influence dry-season assemblages. These results demonstrate that the relative influence of community assembly mechanisms can vary seasonally in response to changing abiotic conditions, and suggest that studies attempting to infer a single dominant mechanism from functional patterns may overlook important aspects of the assembly process. During the prolonged flood pulse of the wet season, expanded habitat and lower densities of aquatic organisms likely reduce the influence of competition and predation. This temporal shift in the influence of different assembly mechanisms, rather than any single mechanism, may play a large role in maintaining the structure and diversity of tropical rivers and perhaps other dynamic and biodiverse systems. © 2016 by the Ecological Society of America.

Changes in composition, cellulose degradability and biochemical methane potential of Miscanthus species during the growing season.

Science.gov (United States)

Peng, Xiaowei; Li, Chao; Liu, Jing; Yi, Zili; Han, Yejun

2017-07-01

The composition, cellulose degradability and biochemical methane potential (BMP) of M. sinensis, M. floridulus, Miscanthus×giganteus and M. lutarioriparius were investigated concomitantly at different growth/harvest times during their growing season. For all the four species, there was only a slight change in the compositional content. Meanwhile there was a huge change in the BMP values. At the growth time of 60days the BMPs ranged from 247.1 to 266.5mlg -1 VS. As growth time was prolonged, the BMPs decreased by 11-35%. For each species, the BMP was positively correlated to the cellulose degradability with the correlation coefficients (R 2 ) ranging from 0.8055 to 0.9925. This suggests that besides the biomass yield, it is justifiable to consider cellulose degradability when selecting the suitable harvest time for biofuels production from Miscanthus, especially in tropical and subtropical regions where Miscanthus can be harvested twice or more within a year. Copyright © 2017 Elsevier Ltd. All rights reserved.

Seasonal analysis of the short-term effects of air pollution on daily mortality in Northeast Asia.

Science.gov (United States)

Kim, Satbyul Estella; Honda, Yasushi; Hashizume, Masahiro; Kan, Haidong; Lim, Youn-Hee; Lee, Hyewon; Kim, Clara Tammy; Yi, Seung-Muk; Kim, Ho

2017-01-15

The constituents and concentrations of pollutants, individual exposures, and biologic responses to air pollution may vary by season and meteorological conditions. However, evidence regarding seasonality of the acute effects of air pollution on mortality is limited and inconsistent. Herein, we examined seasonal patterns in the short-term associations of particulate matter (PM) smaller than 10μm (PM 10 ) with daily mortality in 29 cities of three northeast Asian countries. Stratified time-series models were used to determine whether season altered the effect of PM 10 on mortality. This effect was first quantified within each season and at each location using a time-series model, after which city-specific estimates were pooled using a hierarchical Bayesian model. In all data sets, 3,675,348 non-accidental deaths were registered from 1993 to 2009. In Japan, a 10μg/m 3 increase in PM 10 was significantly associated with increases in non-accidental mortality of 0.44% (95% confidence interval [CI]: 0.03%, 0.8%) in spring and 0.42% (0.02%, 0.82%) in fall. In South Korea, a 10μg/m 3 increase in PM 10 was significantly associated with increases in non-accidental mortality of 0.51% (0.01%, 1.01%) in summer and 0.45% (0.03%, 0.87%) in fall, in cardiovascular disease mortality of 0.96% (0.29%, 1.63%) in fall, and in respiratory disease mortality of 1.57% (0.40%, 2.75%) in fall. In China, a 10μg/m 3 increase in PM 10 was associated with increases in non-accidental mortality of 0.33% (0.01%, 0.66%) in summer and 0.41% (0.09%, 0.73%) in winter, in cardiovascular disease mortality of 0.41% (0.08%, 0.74%) in spring and 0.33% (0.02%, 0.64%) in winter, and in respiratory diseases mortality of 0.78% (0.27%, 1.30%) in winter. Our analyses suggest that the acute effect of particulate air pollution could vary seasonally and geographically. Copyright © 2016 Elsevier B.V. All rights reserved.

Global biogeography of seed dormancy is determined by seasonality and seed size: a case study in the legumes.

Science.gov (United States)

Rubio de Casas, Rafael; Willis, Charles G; Pearse, William D; Baskin, Carol C; Baskin, Jerry M; Cavender-Bares, Jeannine

2017-06-01

Seed dormancy is expected to provide ecological advantages by adjusting germination to the favorable growth period. However, many species produce nondormant seeds, particularly in wet tropical forests, a biogeographic pattern that is not well accounted for in current models. We hypothesized that the global distribution of dormant seeds derives from their adaptive value in predictably fluctuating (i.e. seasonal) environments. However, the advantage conferred by dormancy might ultimately depend on other seed attributes, particularly size. This general model was tested within a phylogenetically informed framework using a data set comprising > 216 000 world-wide observations of Fabaceae, spanning three orders of magnitude in seed size and including both dormant and nondormant seeds. Our results confirmed our hypothesis: nondormant seeds can only evolve in climates with long growing seasons and/or in lineages that produce larger seeds. Conversely, dormancy should be evolutionarily stable in temperate lineages with small seeds. When the favorable season is fleeting, seed dormancy is the only adaptive strategy. Based on these results, we predict that, within a given lineage, taxa producing larger, nondormant seeds will necessarily predominate in aseasonal environments, while plants bearing small, dormant seeds will be dominant under short growing seasons. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Impacts of the seasonal distribution of rainfall on vegetation productivity across the Sahel

Science.gov (United States)

Zhang, Wenmin; Brandt, Martin; Tong, Xiaoye; Tian, Qingjiu; Fensholt, Rasmus

2018-01-01

Climate change in drylands has caused alterations in the seasonal distribution of rainfall including increased heavy-rainfall events, longer dry spells, and a shifted timing of the wet season. Yet the aboveground net primary productivity (ANPP) in drylands is usually explained by annual-rainfall sums, disregarding the influence of the seasonal distribution of rainfall. This study tested the importance of rainfall metrics in the wet season (onset and cessation of the wet season, number of rainy days, rainfall intensity, number of consecutive dry days, and heavy-rainfall events) for growing season ANPP. We focused on the Sahel and northern Sudanian region (100-800 mm yr-1) and applied daily satellite-based rainfall estimates (CHIRPS v2.0) and growing-season-integrated normalized difference vegetation index (NDVI; MODIS) as a proxy for ANPP over the study period: 2001-2015. Growing season ANPP in the arid zone (100-300 mm yr-1) was found to be rather insensitive to variations in the seasonal-rainfall metrics, whereas vegetation in the semi-arid zone (300-700 mm yr-1) was significantly impacted by most metrics, especially by the number of rainy days and timing (onset and cessation) of the wet season. We analysed critical breakpoints for all metrics to test if vegetation response to changes in a given rainfall metric surpasses a threshold beyond which vegetation functioning is significantly altered. It was shown that growing season ANPP was particularly negatively impacted after > 14 consecutive dry days and that a rainfall intensity of ˜ 13 mm day-1 was detected for optimum growing season ANPP. We conclude that the number of rainy days and the timing of the wet season are seasonal-rainfall metrics that are decisive for favourable vegetation growth in the semi-arid Sahel and need to be considered when modelling primary productivity from rainfall in the drylands of the Sahel and elsewhere.

Maize response to time of nitrogen application and planting seasons

Directory of Open Access Journals (Sweden)

Parbati Adhikari

2016-12-01

Full Text Available Nitrogen (N response by maize differs due to growing seasons, growth stages, duration and growing domain as N losses is higher due to leaching as well as volatilization. Objective of this study was to know the response of split applications of N and growing seasons on maize under Chitwan environments. Field experiments were conducted for two consecutive years at the research field of NMRP Rampur during the winter, spring, and summer seasons of 2012/013 and 2013/014. Experiments were laid out in factorial randomized complete block design with four replications for all the seasons. Early maturing maize genotype Arun-1 EV was used for the experiments. Five splits of recommended dose of N were tested. Grain yield, days to flowering, plant height, ear height, kernel rows per ear, no. of kernels per row, ear length and thousand grain weight significantly differed due to growing seasons and split applications of N. Significantly higher grain yield (3911 kg ha-1 was obtained with the application of 30 kg N ha-1 each at 30, 45, 60, and 75 days after sowing as compared to control (2801 kg ha-1. Regarding the growing seasons, highest grain yield was obtained in winter (4393 kg ha-1 followed by spring (3791 kg ha-1 and summer (2468 kg ha-1 season, respectively. Results of these studies revealed that four splits of N viz. application of 30 kg N each at 30, 45, 60, and 75 days after sowing respectively, would be more economical to minimize N losses from the soil and efficient use of N at critical growth and development stages of maize.

The growing season greenhouse gas balance of a continental tundra site in the Indigirka lowlands, NE Siberia

Directory of Open Access Journals (Sweden)

M. K. van der Molen

2007-11-01

Full Text Available Carbon dioxide and methane fluxes were measured at a tundra site near Chokurdakh, in the lowlands of the Indigirka river in north-east Siberia. This site is one of the few stations on Russian tundra and it is different from most other tundra flux stations in its continentality. A suite of methods was applied to determine the fluxes of NEE, GPP, R_eco and methane, including eddy covariance, chambers and leaf cuvettes. Net carbon dioxide fluxes were high compared with other tundra sites, with NEE=−92 g C m⁻² yr⁻¹, which is composed of an R_eco=+141 g C m⁻² yr⁻¹ and GPP=−232 g C m⁻² yr⁻¹. This large carbon dioxide sink may be explained by the continental climate, that is reflected in low winter soil temperatures (−14°C, reducing the respiration rates, and short, relatively warm summers, stimulating high photosynthesis rates. Interannual variability in GPP was dominated by the frequency of light limitation (R_g<200 W m⁻², whereas R_eco depends most directly on soil temperature and time in the growing season, which serves as a proxy of the combined effects of active layer depth, leaf area index, soil moisture and substrate availability. The methane flux, in units of global warming potential, was +28 g C-CO₂e m⁻² yr⁻¹, so that the greenhouse gas balance was −64 g C-CO₂e m⁻² yr⁻¹. Methane fluxes depended only slightly on soil temperature and were highly sensitive to hydrological conditions and vegetation composition.

Seasonal transfer of oxygen isotopes from precipitation and soil to the tree ring: source water versus needle water enrichment.

Science.gov (United States)

Treydte, Kerstin; Boda, Sonja; Graf Pannatier, Elisabeth; Fonti, Patrick; Frank, David; Ullrich, Bastian; Saurer, Matthias; Siegwolf, Rolf; Battipaglia, Giovanna; Werner, Willy; Gessler, Arthur

2014-05-01

For accurate interpretation of oxygen isotopes in tree rings (δ(18) O), it is necessary to disentangle the mechanisms underlying the variations in the tree's internal water cycle and to understand the transfer of source versus leaf water δ(18) O to phloem sugars and stem wood. We studied the seasonal transfer of oxygen isotopes from precipitation and soil water through the xylem, needles and phloem to the tree rings of Larix decidua at two alpine sites in the Lötschental (Switzerland). Weekly resolved δ(18) O records of precipitation, soil water, xylem and needle water, phloem organic matter and tree rings were developed. Week-to-week variations in needle-water (18) O enrichment were strongly controlled by weather conditions during the growing season. These short-term variations were, however, not significantly fingerprinted in tree-ring δ(18) O. Instead, seasonal trends in tree-ring δ(18) O predominantly mirrored trends in the source water, including recent precipitation and soil water pools. Modelling results support these findings: seasonal tree-ring δ(18) O variations are captured best when the week-to-week variations of the leaf water signal are suppressed. Our results suggest that climate signals in tree-ring δ(18) O variations should be strongest at temperate sites with humid conditions and precipitation maxima during the growing season. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Early Season Large-Area Winter Crop Mapping Using MODIS NDVI Data, Growing Degree Days Information and a Gaussian Mixture Model

Science.gov (United States)

Skakun, Sergii; Franch, Belen; Vermote, Eric; Roger, Jean-Claude; Becker-Reshef, Inbal; Justice, Christopher; Kussul, Nataliia

2017-01-01

Knowledge on geographical location and distribution of crops at global, national and regional scales is an extremely valuable source of information applications. Traditional approaches to crop mapping using remote sensing data rely heavily on reference or ground truth data in order to train/calibrate classification models. As a rule, such models are only applicable to a single vegetation season and should be recalibrated to be applicable for other seasons. This paper addresses the problem of early season large-area winter crop mapping using Moderate Resolution Imaging Spectroradiometer (MODIS) derived Normalized Difference Vegetation Index (NDVI) time-series and growing degree days (GDD) information derived from the Modern-Era Retrospective analysis for Research and Applications (MERRA-2) product. The model is based on the assumption that winter crops have developed biomass during early spring while other crops (spring and summer) have no biomass. As winter crop development is temporally and spatially non-uniform due to the presence of different agro-climatic zones, we use GDD to account for such discrepancies. A Gaussian mixture model (GMM) is applied to discriminate winter crops from other crops (spring and summer). The proposed method has the following advantages: low input data requirements, robustness, applicability to global scale application and can provide winter crop maps 1.5-2 months before harvest. The model is applied to two study regions, the State of Kansas in the US and Ukraine, and for multiple seasons (2001-2014). Validation using the US Department of Agriculture (USDA) Crop Data Layer (CDL) for Kansas and ground measurements for Ukraine shows that accuracies of greater than 90% can be achieved in mapping winter crops 1.5-2 months before harvest. Results also show good correspondence to official statistics with average coefficients of determination R(exp. 2) greater than 0.85.

Infiltration and Soil Loss Changes during the Growing Season under Ploughing and Conservation Tillage

Directory of Open Access Journals (Sweden)

Gergely Jakab

2017-09-01

Full Text Available Decreased water retention and increased runoff and soil loss are of special importance concerning soil degradation of hilly crop fields. In this study, plots under ploughing (conventional tillage (PT and conservation tillage (CT; 15 years were compared. Rainfall simulation on 6 m2 plots was applied to determine infiltration and soil loss during the growing season. Results were compared with those measured from 1200 m2 plots exposed to natural rainfalls in 2016. Infiltration was always higher under CT than PT, whereas the highest infiltration was measured under the cover crop condition. Infiltration under seedbed and stubble resulted in uncertainties, which suggests that natural pore formation can be more effective at improving soil drainage potential than can temporary improvements created by soil tillage operations. Soil erodibility was higher under PT for each soil status; however, the seedbed condition triggered the highest values. For CT, soil loss volume was only a function of runoff volume at both scales. Contrarily, on PT plots, some extreme precipitation events triggered extremely high soil loss owing to linear erosion, which meant no direct connection existed between the scales. Improved soil conditions due to conservation practice are more important for decreasing soil loss than the better surface conditions.

Effects of a long-term disturbance on arthropods and vegetation in subalpine wetlands: manifestations of pack stock grazing in early versus mid-season.

Directory of Open Access Journals (Sweden)

Jeffrey G Holmquist

Full Text Available Conclusions regarding disturbance effects in high elevation or high latitude ecosystems based solely on infrequent, long-term sampling may be misleading, because the long winters may erase severe, short-term impacts at the height of the abbreviated growing season. We separated a long-term effects of pack stock grazing, manifested in early season prior to stock arrival, from b additional pack stock grazing effects that might become apparent during annual stock grazing, by use of paired grazed and control wet meadows that we sampled at the beginning and end of subalpine growing seasons. Control meadows had been closed to grazing for at least two decades, and meadow pairs were distributed across Sequoia National Park, California, USA. The study was thus effectively a landscape-scale, long-term manipulation of wetland grazing. We sampled arthropods at these remote sites and collected data on associated vegetation structure. Litter cover and depth, percent bare ground, and soil strength had negative responses to grazing. In contrast, fauna showed little response to grazing, and there were overall negative effects for only three arthropod families. Mid-season and long-term results were generally congruent, and the only indications of lower faunal diversity on mid-season grazed wetlands were trends of lower abundance across morphospecies and lower diversity for canopy fauna across assemblage metrics. Treatment x Season interactions almost absent. Thus impacts on vegetation structure only minimally cascaded into the arthropod assemblage and were not greatly intensified during the annual growing season. Differences between years, which were likely a response to divergent snowfall patterns, were more important than differences between early and mid-season. Reliance on either vegetation or faunal metrics exclusively would have yielded different conclusions; using both flora and fauna served to provide a more integrative view of ecosystem response.

Effects of a long-term disturbance on arthropods and vegetation in subalpine wetlands: manifestations of pack stock grazing in early versus mid-season.

Science.gov (United States)

Holmquist, Jeffrey G; Schmidt-Gengenbach, Jutta; Haultain, Sylvia A

2013-01-01

Conclusions regarding disturbance effects in high elevation or high latitude ecosystems based solely on infrequent, long-term sampling may be misleading, because the long winters may erase severe, short-term impacts at the height of the abbreviated growing season. We separated a) long-term effects of pack stock grazing, manifested in early season prior to stock arrival, from b) additional pack stock grazing effects that might become apparent during annual stock grazing, by use of paired grazed and control wet meadows that we sampled at the beginning and end of subalpine growing seasons. Control meadows had been closed to grazing for at least two decades, and meadow pairs were distributed across Sequoia National Park, California, USA. The study was thus effectively a landscape-scale, long-term manipulation of wetland grazing. We sampled arthropods at these remote sites and collected data on associated vegetation structure. Litter cover and depth, percent bare ground, and soil strength had negative responses to grazing. In contrast, fauna showed little response to grazing, and there were overall negative effects for only three arthropod families. Mid-season and long-term results were generally congruent, and the only indications of lower faunal diversity on mid-season grazed wetlands were trends of lower abundance across morphospecies and lower diversity for canopy fauna across assemblage metrics. Treatment x Season interactions almost absent. Thus impacts on vegetation structure only minimally cascaded into the arthropod assemblage and were not greatly intensified during the annual growing season. Differences between years, which were likely a response to divergent snowfall patterns, were more important than differences between early and mid-season. Reliance on either vegetation or faunal metrics exclusively would have yielded different conclusions; using both flora and fauna served to provide a more integrative view of ecosystem response.

Short-term effects of salinity reduction and drainage on salt-marsh biogeochemical cycling and Spartina (Cordgrass) production

Science.gov (United States)

Portnoy, J.W.; Valiela, I.

1997-01-01

To assess the biogeochemical effects of tidal restrictions on salt-marsh sulfur cycling and plant growth, cores of short-form Spartina alterniflora peat were desalinated and kept either waterlogged or drained in greenhouse microcosms. Changes in net Spartina production, and porewater and solid phase chemistry of treated cores were compared to natural conditions in the field collection site over a 21-mo period. Net production among treatments increased significantly in drained and waterlogged peat compared to field conditions during the first growing season. Constantly high sulfide in waterlogged cores accompanied reduced plant growth. Aeration invigorated growth in drained cores but led to oxidization of sulfide minerals and to lowered pH. During the second growing season, growth declined in the drained treatment, probably because of acidification and decreased dissolved inorganic nitrogen. Results are pertinent to the success of current wetland protection and restoration activities in the coastal zone.

Statistical properties of the seasonal fractionally integrated ...

African Journals Online (AJOL)

We investigate the properties of this new model providing stationary conditions, some explicit form of the autocovariance function and the spectral density. We also establish the asymptotic behaviour of the spectral density function near the seasonal frequencies. Keywords: Seasonality; Spatial short memory; Seasonal long ...

Seasonal differences in leaf-level physiology give lianas a competitive advantage over trees in a tropical seasonal forest

NARCIS (Netherlands)

Cai, Z.Q.; Schnitzer, S.A.; Bongers, F.

2009-01-01

Lianas are an important component of most tropical forests, where they vary in abundance from high in seasonal forests to low in aseasonal forests. We tested the hypothesis that the physiological ability of lianas to fix carbon (and thus grow) during seasonal drought may confer a distinct advantage

The European Market for Seasonal Gas Storage

International Nuclear Information System (INIS)

Mahan, A.

2006-02-01

European demand for gas will grow in the years to come. Simultaneously, gas production in Europe will decrease and imported gas will be needed to replace indigenous production. Gas demand is not constant during the year. There are variations in demand on different timescales ranging from seasonal to hourly. Variations in demand are characterised by two main parameters: working volume and deliverability. Working volume - the amount of gas that can be supplied above the baseload production volume during a long (cold) period- is primarily needed to cope with the summer-winter pattern of gas consumption. Most of the summer-winter pattern comes from the temperature sensitive gas consumption by households and service industries. Gas usage by industry and the power sector are more evenly spread throughout the year and need less working volume. Deliverability - the amount of gas per hour that can be generated on a (very) cold day above the baseload capacity - is the ability to produce large volumes during short periods, e.g. for extremely cold days, or during peak periods during a day. In this paper we argue that a large amount of additional working volume will be required over the coming years. First, flexible European production will be replaced by long-distance import gas, and second, the gas market is expected to grow further. Todays market appears focus mainly on cavems for storage volume. Cavems have little working volume but are ideal for trading purposes. Consequently, Europe may be facing a deficit in working volume, i.e. the ability to cope with seasonal changes in demand. This paper aims to widen the discussion of this matter and give rise to this concern by setting out a broad analysis, exploring the market drivers for seasonal storage and identifying the public interest issues for this market. Chapter 2 gives an overview of demand for and supply characteristics of gas flexibility. Chapter 3 describes the role of gas storage facilities in the gas market

Energy balance and evaporation of a short-rotation willow forest. Variation with season and stand development

Energy Technology Data Exchange (ETDEWEB)

Iritz, Z.

1996-10-01

Energy balance and evaporation of a short-rotation willow (Salix viminalis L.) forest was studied in relation to season and stand development. The developmental stage of the forest stand considerably influenced how the energy, received as net radiation, was partitioned between the connective fluxes and the storage components. The main part of the available energy was utilised for evaporation during most of the season. Only at the beginning of the season did the willow forest supply heat to the atmosphere. Later in the season, energy was taken from air and utilised for evaporation, which resulted in negative sensible heat fluxes. Soil heat storage was also a significant term in the energy balance and also strongly depended on canopy development. Changes in energy partitioning relative to leaf area indices indicated the existence of a threshold value for leaf area index of the developing canopy. The analysis suggested that the canopy of the willow forest could be considered as closed at a leaf area index of 2. It was further found that evaporation from well-irrigated willow forest occurred also during night-time, particularly in windy and dry weather conditions. The sources of nocturnal evaporation were both the canopy, i.e. indicating non-closed stomata, and the soil surface. Partitioning of the total evaporation into components was investigated using a physically-based model with a two-layer aboveground representation and a two-layer soil module. The model estimates evaporation with respect to developmental stage of the willow stand and also takes into account the interaction between the fluxes from the canopy and the soil surface. Good performance of the model indicated that, after further testing in drier conditions, it could be used as a tool for analysing the prerequisites for energy-forest establishment, and practical management of energy forest stands. 37 refs, 9 figs

The impact of growing-season length variability on carbon assimilation and evapotranspiration over 88 years in the eastern US deciduous forest

Science.gov (United States)

White; Running; Thornton

1999-02-01

Recent research suggests that increases in growing-season length (GSL) in mid-northern latitudes may be partially responsible for increased forest growth and carbon sequestration. We used the BIOME-BGC ecosystem model to investigate the impacts of including a dynamically regulated GSL on simulated carbon and water balance over a historical 88-year record (1900-1987) for 12 sites in the eastern USA deciduous broadleaf forest. For individual sites, the predicted GSL regularly varied by more than 15 days. When grouped into three climatic zones, GSL variability was still large and rapid. There is a recent trend in colder, northern sites toward a longer GSL, but not in moderate and warm climates. The results show that, for all sites, prediction of a long GSL versus using the mean GSL increased net ecosystem production (NEP), gross primary production (GPP), and evapotranspiration (ET); conversely a short GSL is predicted to decrease these parameters. On an absolute basis, differences in GPP between the dynamic and mean GSL simulations were larger than the differences in NEP. As a percentage difference, though, NEP was much more sensitive to changes in GSL than were either GPP or ET. On average, a 1-day change in GSL changed NEP by 1.6%, GPP by 0.5%, and ET by 0.2%. Predictions of NEP and GPP in cold climates were more sensitive to changes in GSL than were predictions in warm climates. ET was not similarly sensitive. First, our results strongly agree with field measurements showing a high correlation between NEP and dates of spring growth, and second they suggest that persistent increases in GSL may lead to long-term increases in carbon storage.

PRODUCTIVITY OF GROWING PONDS WHEN APPLYING THE BACTERIAL FERTILIZER «PHOSPHOBAKTERIN»

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Т. Hryhorenko

2017-09-01

Full Text Available Purpose. To investigate the effect of the bacterial fertilizer "Phosphobacterin" on the formation of the hydrochemical regime, development of the natural food supply and fish productivity in the growing ponds. Methodology. The work was conducted according to generally accepted hydrochemical,, microbiological, hydrobiological and fish farming methods. Findings The article presents the results of a study of the productivity of growing ponds with different methods of the application of the bacterial fertilizer "Phosphobacterin". It was found that the hydrochemical regime of the experimental ponds was formed under the effect of the source of water supply and measures aimed at intensifying the development of the natural food supply and was favorable for the development of feed organisms and the cultivation of fish seeds. Application of the bacterial fertilizer at the beginning of the growing season along the water pond surface proved to be little effective for increasing the productivity of the pond ecosystem as a whole. A more effective method of increasing biological productivity, including fish productivity of growing ponds, was the application of "Phosphobacterin" during the growing season both on the bed and on the water surface in combination with the organic fertilizer - cattle humus. In the experimental pond under complex fertilization, the average phytoplankton biomass during the growing season was 1.5 times, bacterioplankton 1.1 times, zoobenthos 2.6 times higher, and the obtained total fish productivity was 1.2 times higher than in the control pond (when applying only cattle humus. Originality. The peculiarities of formation of hydrochemical and hydrobiological (phyto-, bacterio-, zooplankton, zoobenthos regimes of growing ponds and the fishery indices are studied, both for bacterial fertilizer "Phosphobacterin" independently and together with the traditional organic fertilizer - cattle humus. Practical value. Based on the obtained results

Relating groundwater to seasonal wetlands in southeastern Wisconsin, USA

Science.gov (United States)

Skalbeck, J.D.; Reed, D.M.; Hunt, R.J.; Lambert, J.D.

2009-01-01

Historically, drier types of wetlands have been difficult to characterize and are not well researched. Nonetheless, they are considered to reflect the precipitation history with little, if any, regard for possible relation to groundwater. Two seasonal coastal wetland types (wet prairie, sedge meadow) were investigated during three growing seasons at three sites in the Lake Michigan Basin, Wisconsin, USA. The six seasonal wetlands were characterized using standard soil and vegetation techniques and groundwater measurements from the shallow and deep systems. They all met wetland hydrology criteria (e.g., water within 30 cm of land surface for 5% of the growing season) during the early portion of the growing season despite the lack of appreciable regional groundwater discharge into the wetland root zones. Although root-zone duration analyses did not fit a lognormal distribution previously noted in groundwater-dominated wetlands, they were able to discriminate between the plant communities and showed that wet prairie communities had shorter durations of continuous soil saturation than sedge meadow communities. These results demonstrate that the relative rates of groundwater outflows can be important for wetland hydrology and resulting wetland type. Thus, regional stresses to the shallow groundwater system such as pumping or low Great Lake levels can be expected to affect even drier wetland types. ?? Springer-Verlag 2008.

Effects of a short-term feed restriction on growth performance, blood metabolites and hepatic IGF-1 levels in growing rabbits

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J. Lu

2017-09-01

Full Text Available A total of 144 weaned hybrid HYLA rabbits (40-day-old were randomly divided into 4 groups, to investigate the effects of the intensity of one week’s feed restriction on short- and medium-term growth performance, blood metabolites and hepatic IGF-1 in growing rabbits. Restricted groups were fed with 30% (Group L30, 50% (Group L50 70% (Group L70 of ad libitum feeding for 1 wk and then fed ad libitum until the end of the experiment (75 d of age. The control group (Group AL was fed ad libitum throughout the experiment. Total feed intake (–15.8% and feed conversion ratio (–13.2% were lower in the L50 than in the AL group (P0.05 for these parameters. Total weight gain did not significantly differ among the 4 experimental groups (38.5 g/d; P>0.05. At the end of the feed restriction period, the total serum protein level (P=0.01 was higher in restricted rabbits than AL rabbits (P0.05 throughout the experiment. In conclusion, a short-term feed restriction improves feed conversion ratio in a lasting way, transiently alters serum protein and IFG-1 levels and leads to compensatory growth in growing rabbits.

High methane emissions from restored Norway spruce swamps in southern Finland over one growing season

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M. Koskinen

2016-02-01

Full Text Available Forestry-drained peatlands in the boreal region are currently undergoing restoration in order to bring these ecosystems closer to their natural (undrained state. Drainage affects the methane (CH4 dynamics of a peatland, often changing sites from CH4 sources to sinks. Successful restoration of a peatland would include restoration of not only the surface vegetation and hydrology, but also the microbial populations and thus CH4 dynamics. As a pilot study, CH4 emissions were measured on two pristine, two drained and three restored boreal spruce swamps in southern Finland for one growing season. Restoration was successful in the sense that the water table level in the restored sites was significantly higher than in the drained sites, but it was also slightly higher than in the pristine sites. The restored sites were surprisingly large sources of CH4 (mean emissions of 52.84 mg CH4 m-2 d-1, contrasting with both the pristine (1.51 mg CH4 m-2 d-1 and the drained sites (2.09 mg CH4 m-2 d-1. More research is needed to assess whether the high CH4 emissions observed in this study are representative of restored spruce mires in general.

Algorithms for in-season nutrient management in cereals

Science.gov (United States)

The demand for improved decision making products for cereal production systems has placed added emphasis on using plant sensors in-season, and that incorporate real-time, site specific, growing environments. The objective of this work was to describe validated in-season sensor based algorithms prese...

Daily and seasonal variation of short-lived radon decay product concentrations in ground-level air at Munich-Neuherberg - a long-term study

International Nuclear Information System (INIS)

Winkler, R.

2001-09-01

Daily and seasonal variation of the equilibrium equivalent radon concentration (EEC Rn-222 ) and of the concentration of the short-lived radon decay product 214 Pb in ground-level air was investigated at Munich-Neuherberg from 1982 to 2000, and from 1989 to 2000, respectively. For this, the EEC was measured continuously with an alpha/beta aerosol monitor at 2.5 m above ground, and 214 Pb was determined by online gamma spectrometry at about 12 m above ground. The resulting time series were analysed statistically. For the respective periods, the measurements yielded a long-term average concentration of 7.8 Bq m -3 (geometric mean: 6.1 Bq m -3 ) for the EEC, and 6.0 Bq m -3 (geom. mean: 5.0 Bq m -3 ) for 214 Pb. In these periods, daily averages ranged from 0.6 to 49 Bq m -3 (EEC), and from 0.6 to 43 Bq m -3 ( 214 Pb). Monthly mean concentrations varied between 3.0 Bq m -3 in March 1988 and 20 Bq m -3 in October 1985 (EEC), and from 3.4 Bq m -3 in April 1992 to 11 Bq m -3 in October 1995 ( 214 Pb), respectively. The annual average concentrations were from 5.9 Bq m -3 in 1999 to 10.6 Bq m -3 in 1985 (EEC), and from 5.3 Bq m -3 in 1999 to 6.8 Bq m -3 in 1991 ( 214 Pb). From the long-term average equilibrium equivalent radon concentration (EEC), an average annual effective dose of 0.13 mSv due to the short-lived radon progeny outdoors was estimated. The time series showed distinct daily and seasonal variations. The variations from day to day are mainly caused by the actual weather conditions (wind, rain, etc.), i.e. the short-term turbulent conditions. The seasonal pattern is characterised by an autumn to winter maximum and an early summer minimum, and reflects the prevailing turbulent conditions at the respective seasons. As known, at Munich-Neuherberg during autumn and winter months (October/November to February) inversion weather conditions frequently occur, while the other months are characterised by more turbulent conditions. (orig.)

Green manuring with Calotropis procera for the production of coriander in two growing seasons

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Ênio Gomes Flôr Souza

Full Text Available ABSTRACT The use of spontaneous species of the Caatinga biome can contribute significantly to the nutritional demand of vegetable crops, thereby providing an agroecological and sustainable form of production. The objective of this research was to determine the effects of different biomasses of Calotropis procera (rooster tree and times of incorporation into the soil of green manure during two growing seasons on the agronomic performance of coriander cv. Verdão produced in Serra Talhada, a semi-arid region of Pernambuco, Brazil. The experimental design was randomized blocks with three replications. The treatments were arranged in a 4 x 4 factorial scheme, with the first factor consisting of biomass amounts of C. procera (5.4, 8.8, 12.2 and 15.6 t ha-1 on a dry basis and the second by the incorporation times into the soil (0, 10, 20 and 30 days before coriander planting. The evaluated characteristics were plant height, number of stems per plant, yield of green mass and dry mass of shoot. The best productive performance of coriander was observed in amounts of 12.2 (spring and 8.8 (autumn-winter t ha-1 C. procera added to the soil, with an ideal incorporation time of 13 (spring and 23 (autumn-winter days before sowing of the crop and with larger accumulations of green and dry mass of the shoot being obtained in autumn-winter.

Monitoring start of season in Alaska with GLOBE, AVHRR, and MODIS data

Science.gov (United States)

Robin, Jessica; Dubayah, Ralph; Sparrow, Elena; Levine, Elissa

2008-03-01

This work evaluates whether continuity between Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) is achievable for monitoring phenological changes in Alaska. This work also evaluates whether NDVI can detect changes in start of the growing season (SOS) in this region. Six quadratic regression models with NDVI as a function of accumulated growing degree days (AGDD) were developed from 2001 through 2004 AVHRR and MODIS NDVI data sets for urban, mixed, and forested land covers. Model parameters determined NDVI values for start of the observational period as well as peak and length of the growing season. NDVI values for start of the growing season were determined from the model equations and field observations of SOS made by GLOBE students and researchers at University of Alaska Fairbanks. AGDD was computed from daily air temperature. AVHRR and MODIS models were significantly different from one another with differences in the start of the observational season as well as start, peak, and length of the growing season. Furthermore, AGDD for SOS was significantly lower during the 1990s than the 1980s. NDVI values at SOS did not detect this change. There are limitations with using NDVI to monitor phenological changes in these regions because of snow, the large extent of conifers, and clouds, which restrict the composite period. In addition, differing processing and spectral characteristics restrict continuity between AVHRR and MODIS NDVI data sets.

The effective mitigation of greenhouse gas emissions from rice paddies without compromising yield by early-season drainage

DEFF Research Database (Denmark)

Islam, Syed Faiz-Ul; van Groenigen, Jan Willem; Jensen, Lars Stoumann

2018-01-01

Global rice production systems face two opposing challenges: the need to increase production to accommodate the world's growing population while simultaneously reducing greenhouse gas (GHG) emissions. Adaptations to drainage regimes are one of the most promising options for methane mitigation...... only. A combination of (short or long) ED drainage and one MD drainage episode was found to be the most effective in mitigating CH4 emissions without negatively affecting yield. In particular, compared with CF, the long early-season drainage treatments LE+SM and LE+LM significantly (p

Reptile and amphibian response to season of burn in an upland hardwood forest

Science.gov (United States)

Cathryn H. Greenberg; Tyler Seiboldt; Tara L. Keyser; W. Henry McNab; Patrick Scott; Janis Bush; Christopher E. Moorman

2018-01-01

Growing-season burns are increasingly used in upland hardwood forest for multiple forest management goals. Many species of reptiles and amphibians are ground-dwelling, potentially increasing their vulnerability to prescribed fire, especially during the growing-season when they are most active. We used drift fences with pitfall traps to experimentally assess how...

Seasonal response of biomass growth and allocation of a boreal bioenergy crop (Phalaris arundinacea L.) to climate change

Energy Technology Data Exchange (ETDEWEB)

Chang Zhang

2013-06-01

The aim of this work was to analyse how the seasonal biomass growth and allocation in a boreal bioenergy crop (Phalaris arundinacea L., hereafter RCG) were affected by elevated temperature and CO{sub 2} under different levels of groundwater. For this purpose, plants in peat monoliths representing young and old cultivations were grown in auto-controlled environmental chambers over two growing seasons (April-September, 2009 and 2010) under elevated temperature (ambient + 3.5 deg C) and CO{sub 2} (700 {mu}mol mol{sup -1}). (CON: ambient conditions, EC: elevated CO{sub 2}, ET: elevated temperature, ETC: elevated temperature and CO{sub 2}). Three levels of groundwater, ranging from high (HW, 0 cm below the soil surface), to normal (NW, 20 cm below the soil surface) and low (LW, 40 cm below the soil surface), were used. Compared to growth under CON, ET enhanced leaf development and photosynthesis in the RCG plant. Consequently, ET enhanced biomass growth during early growing periods. It also reduced photosynthesis and caused earlier leaf senescence during later growing periods. ET therefore reduced total biomass growth across the entire growing season. EC significantly increased biomass growth throughout the growing period primarily because of increased leaf area and photosynthesis. LW decreased the growth of RCG, mainly because of lower leaf area and photosynthesis. Furthermore, LW accelerated the cessation of growth, thus making the growing season shorter compared with the effects of higher groundwater levels. The LW- induced reductions in biomass growth were exacerbated by ET and partially mitigated by EC. The ETC slightly increased final plant growth. The age of cultivation did not affect the biomass growth among the three major organs (leaf, stem and root) and thus did not affect total biomass growth. Biomass growth was mainly allocated to leaves (LMF) and stems (SMF) in the early growing season, to stems in the middle of the growing season and to roots (RMF) later

Qualidade ambiental em solo com diferentes ciclos de cultivo do meloeiro irrigado Environmental quality in soil with different growing season cultivated w ith muskmelon irrigated

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Celsemy Eleutério Maia

2013-04-01

Full Text Available O solo é um importante componente do ecossistema terrestre, porque preserva reservas de nutrientes e dá suporte a processos biológicos. Para a preservação desse recurso, é necessário em primeiro lugar saber as condições e os processos que acontecem no solo, obtidos por meio de índices que determinam a sua qualidade. O objetivo deste trabalho foi avaliar a qualidade ambiental em Latossolo Vermelho cultivado com diferentes ciclos da cultura do melão. Foram coletadas amostras de solos de nove áreas com diferentes ciclos de cultivo e comparados com as da mata nativa. Concluiu-se que a qualidade ambiental diminuiu com os ciclos de cultivo, quando comparada com a área de referência de mata nativa.Soil is an important component of terrestrial ecosystems because it preserves nutrient reserves, supports many biological. To preserve this resource and its functions, it is necessary first of all to know the conditions and the processes occurring in it, for example, through the determination of soil quality. The aim of this study was to evaluate the environmental quality in Oxisol cultivated with different growing season of muskmelon. Were collected soil samples from nine areas with different growing season and compared with the native forest. It was concluded that environmental quality decreased with crop cycles when compared with the reference area of native forest.

Factors influencing the seasonal patterns of infectious diseases

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Auda Fares

2013-01-01

Full Text Available The recognition of seasonal patterns in infectious disease occurrence dates back at least as far as the hippocratic era, but the mechanisms underlying these fluctuations remain poorly understood. Many classes of mechanistic hypotheses have been proposed to explain seasonality of various directly transmitted diseases, including at least the following; human activity, seasonal variability in human immune system function, seasonal variations in vitamin D levels, seasonality of melatonin, and pathogen infectivity. In this short paper will briefly discuss the role of these factors in the seasonal patterns of infectious diseases.

Differences in Cd and Zn bioaccumulation for the flood-tolerant Salix cinerea rooting in seasonally flooded contaminated sediments.

Science.gov (United States)

Vandecasteele, Bart; Laing, Gijs Du; Quataert, Paul; Tack, Filip M G

2005-04-01

Several authors suggest that a hydrological regime aiming at wetland creation is a potential management option that favours reducing bioavailability for metal-contaminated sites. The hydrological conditions on a site constitute one of the many factors that may affect the availability of potentially toxic trace metals for uptake by plants. Bioavailability of Cd, Mn and Zn on a contaminated dredged sediment landfill (DSL) with variable duration of submersion was evaluated by measuring metal concentrations in the wetland plant species Salix cinerea in field conditions. Longer submersion periods in the field caused lower Cd and Zn concentrations in the leaves in the first weeks of the growing season. Foliar Cd and Zn concentrations at the end of the growing season were highest on the initially flooded plot that emerged early in the growing season. Foliar Zn concentrations were also high at a sandy-textured oxic plot with low soil metal concentrations. Zn uptake in the leaves was markedly slower than Cd uptake for trees growing on soils with prolonged waterlogging during the growing season, pointing at a different availability. Zn availability was lowest when soil was submerged, but metal transfer from stems and twigs to leaves may mask the lower availability of Cd in submerged soils. Especially for Cd, a transfer effect from one growing season to the next season was observed: oxic conditions at the end of the previous growing season seem to determine at least partly the foliar concentrations for S. cinerea through this metal transfer mechanism. Duration of the submersion period is a key factor for bioavailability inasmuch as initially submerged soils emerging only in the second half of the growing season resulted in elevated Cd and Zn foliar concentrations at that time.

Simulation of water management for fodder beet to reduce yield losses under late season drought

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T. Noreldin

2016-12-01

Full Text Available The objectives of this study were to calibrate CropSyst model for fodder beet grown under full and late season drought and to use the simulation results to analyze the relationship between irrigation amount and yield, as well as in water management to reduce yield losses under full and late season drought. For this reason, two field experiments were implemented at El-Serw Agricultural Research Station in Demiatte governorate, during 2011/12 and 2012/13 growing seasons. Two irrigation treatments were studied: full irrigation and late season drought. The model was calibrated using the data obtained from the two seasons. Results indicated that the reduction in fodder beet yield under late season drought was 11 and 12% in 2011/12 and 2012/13 growing seasons, respectively. Calibration of CropSyst revealed that the percentage of difference between measured and predicted values were low in both growing seasons. The results also indicated that changing irrigation schedule after examining water stress index under full and late season drought led to increase in fodder beet yield, as well as water and land productivity. Thus, CropSyst model can give insight into when to apply irrigation water to minimize yield losses under late season drought.

Impacts of Land Cover and Seasonal Variation on Maximum Air Temperature Estimation Using MODIS Imagery

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Yulin Cai

2017-03-01

Full Text Available Daily maximum surface air temperature (Tamax is a crucial factor for understanding complex land surface processes under rapid climate change. Remote detection of Tamax has widely relied on the empirical relationship between air temperature and land surface temperature (LST, a product derived from remote sensing. However, little is known about how such a relationship is affected by the high heterogeneity in landscapes and dynamics in seasonality. This study aims to advance our understanding of the roles of land cover and seasonal variation in the estimation of Tamax using the MODIS (Moderate Resolution Imaging Spectroradiometer LST product. We developed statistical models to link Tamax and LST in the middle and lower reaches of the Yangtze River in China for five major land-cover types (i.e., forest, shrub, water, impervious surface, cropland, and grassland and two seasons (i.e., growing season and non-growing season. Results show that the performance of modeling the Tamax-LST relationship was highly dependent on land cover and seasonal variation. Estimating Tamax over grasslands and water bodies achieved superior performance; while uncertainties were high over forested lands that contained extensive heterogeneity in species types, plant structure, and topography. We further found that all the land-cover specific models developed for the plant non-growing season outperformed the corresponding models developed for the growing season. Discrepancies in model performance mainly occurred in the vegetated areas (forest, cropland, and shrub, suggesting an important role of plant phenology in defining the statistical relationship between Tamax and LST. For impervious surfaces, the challenge of capturing the high spatial heterogeneity in urban settings using the low-resolution MODIS data made Tamax estimation a difficult task, which was especially true in the growing season.

Effect of corn dry distiller grains plus solubles supplementation level on performance and digestion characteristics of steers grazing native range during forage growing season.

Science.gov (United States)

Martínez-Pérez, M F; Calderón-Mendoza, D; Islas, A; Encinias, A M; Loya-Olguín, F; Soto-Navarro, S A

2013-03-01

Two experiments were conducted to evaluate effects of corn dry distiller grains plus condensed solubles (DDGS) supplementation level on performance digestion characteristics of steers grazing native range during the forage growing season. In the performance study, 72 (206 ± 23.6 kg; 2008) and 60 (230 ± 11.3 kg; 2009) English crossbred steer calves were used in a randomized complete block design replicated over 2 yr. The grazing periods lasted 56 and 58 d and started on August 11 and 18 for 2008 and 2009, respectively. Each year, steers were blocked by BW (light, medium, and heavy), stratified by BW within blocks, and randomly assigned to 1 of 4 grazing groups. Each grazing group (6 steers in 2008 and 5 in 2009) was assigned to a DDGS supplementation levels (0, 0.2, 0.4, and 0.6% BW). Grazing group served as the experimental unit with 12 groups per year receiving 1 of 4 treatments for 2 yr (n = 6). In the metabolism study, 16 English crossbred steers (360 ± 28.9 kg) fitted with ruminal cannulas grazing native range during the summer growing season were used in a completely randomized design to evaluate treatment effects on forage intake and digestion. The experiment was conducted during the first and second weeks of October 2008. Steers were randomly assigned to supplement level (0, 0.2, 0.4, and 0.6% BW; n = 4) and grazed a single native range pasture with supplements offered individually once daily at 0700 h. In the performance study, ADG (0.64, 0.75, 0.80, and 0.86 ± 0.03 kg/d for 0, 0.2, 0.4, and 0.6% BW, respectively) increased linearly (P = 0.01) with increasing DDGS supplementation level. In the metabolism study, forage OM, NDF, CP, and ether extract (EE) intake decreased (P ≤ 0.05) linearly with increasing DDGS supplementation level. Total CP and EE intake increased (P ≤ 0.002) with increasing DDGS supplementation level. Digestibility of OM, NDF, and EE increased (linear; P ≤ 0.008) whereas the soluble CP fraction of forage masticate sample

Seasonality of cavitation and frost fatigue in Acer mono Maxim.

Science.gov (United States)

Zhang, Wen; Feng, Feng; Tyree, Melvin T

2017-12-08

Although cavitation is common in plants, it is unknown whether the cavitation resistance of xylem is seasonally constant or variable. We tested the changes in cavitation resistance of Acer mono before and after a controlled cavitation-refilling and freeze-thaw cycles for a whole year. Cavitation resistance was determined from 'vulnerability curves' showing the percent loss of conductivity versus xylem tension. Cavitation fatigue was defined as a reduction of cavitation resistance following a cavitation-refilling cycle, whereas frost fatigue was caused by a freeze-thaw cycle. A. mono developed seasonal changes in native embolisms; values were relatively high during winter but relatively low and constant throughout the growing season. Cavitation fatigue occurred and changed seasonally during the 12-month cycle; the greatest fatigue response occurred during summer and the weakest during winter, and the transitions occurred during spring and autumn. A. mono was highly resistant to frost damage during the relatively mild winter months; however, a quite different situation occurred during the growing season, as the seasonal trend of frost fatigue was strikingly similar to that of cavitation fatigue. Seasonality changes in cavitation resistance may be caused by seasonal changes in the mechanical properties of the pit membranes. © 2017 John Wiley & Sons Ltd.

Seasonal and Interannual Variation in Energy Balance in the Semiarid Grassland Area of China

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Qun’ou Jiang

2015-01-01

Full Text Available Near surface energy budget changes have been proved to be induced by the land cover conversion through changing the surface physical properties, which can further impact the regional climate change. This study applies the DLS model to simulate the land cover under the business as usual (BAU scenario and then analyses the seasonal and interannual variation of energy balance in the semiarid grassland area of China based on the simulated land cover with the Weather Research and Forecasting (WRF model. The results indicate that the grassland will show a growing trend under the BAU scenario. Downward long wave radiation and downward short wave radiation will all have small-scale increase with time going by, while the surface net radiation will decrease from 2030 to 2050. However, there is obvious seasonal variation. Summer has the highest downward long wave radiation and downward short wave radiation, followed by spring and autumn. The lowest are in winter. As for the net surface radiation, there is obvious decrease in southeast of study area due to returning cropland to grassland. Those research conclusions can offer valuable information for the land use planning and relieving the effects of land cover change on climate change at the semiarid grassland area.

A trend fixed on firstly and seasonal adjustment model combined with the ε-SVR for short-term forecasting of electricity demand

International Nuclear Information System (INIS)

Wang Jianzhou; Zhu Wenjin; Zhang Wenyu; Sun Donghuai

2009-01-01

Short-term electricity demand forecasting has always been an essential instrument in power system planning and operation by which an electric utility plans and dispatches loading so as to meet system demand. The accuracy of the dispatching system, derived from the accuracy of demand forecasting and the forecasting algorithm used, will determines the economic of the power system operation as well as the stability of the whole society. This paper presents a combined ε-SVR model considering seasonal proportions based on development tendencies from history data. We use one-order moving averages to produce a comparatively smooth data series, taking the averaging period as the interval that can effectively eliminate the seasonal variation. We used the smoothed data series as the training set input for the ε-SVR model and obtained the corresponding forecasting value. Afterward, we accounted for the previously removed seasonal variation. As a case, we forecast northeast electricity demand of China using the new method. We demonstrated that this simple procedure has very satisfactory overall performance by an analysis of variance with relative verification and validation. Significant reductions in forecast errors were achieved.

A trend fixed on firstly and seasonal adjustment model combined with the epsilon-SVR for short-term forecasting of electricity demand

Energy Technology Data Exchange (ETDEWEB)

Wang Jianzhou [School of Mathematics and Statistics, Lanzhou University, Lanzhou 730000 (China); Zhu Wenjin, E-mail: crying.1@hotmail.co [School of Mathematics and Statistics, Lanzhou University, Lanzhou 730000 (China); Zhang Wenyu [College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000 (China); Sun Donghuai [Key Laboratory of Western Chinas Environmental Systems (Ministry of Education) College of Earth and Environment Sciences, Lanzhou University, Lanzhou 730000 (China)

2009-11-15

Short-term electricity demand forecasting has always been an essential instrument in power system planning and operation by which an electric utility plans and dispatches loading so as to meet system demand. The accuracy of the dispatching system, derived from the accuracy of demand forecasting and the forecasting algorithm used, will determines the economic of the power system operation as well as the stability of the whole society. This paper presents a combined epsilon-SVR model considering seasonal proportions based on development tendencies from history data. We use one-order moving averages to produce a comparatively smooth data series, taking the averaging period as the interval that can effectively eliminate the seasonal variation. We used the smoothed data series as the training set input for the epsilon-SVR model and obtained the corresponding forecasting value. Afterward, we accounted for the previously removed seasonal variation. As a case, we forecast northeast electricity demand of China using the new method. We demonstrated that this simple procedure has very satisfactory overall performance by an analysis of variance with relative verification and validation. Significant reductions in forecast errors were achieved.

A trend fixed on firstly and seasonal adjustment model combined with the {epsilon}-SVR for short-term forecasting of electricity demand

Energy Technology Data Exchange (ETDEWEB)

Wang, Jianzhou; Zhu, Wenjin [School of Mathematics and Statistics, Lanzhou University, Lanzhou 730000 (China); Zhang, Wenyu [College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000 (China); Sun, Donghuai [Key Laboratory of Western Chinas Environmental Systems (Ministry of Education) College of Earth and Environment Sciences, Lanzhou University, Lanzhou 730000 (China)

2009-11-15

Short-term electricity demand forecasting has always been an essential instrument in power system planning and operation by which an electric utility plans and dispatches loading so as to meet system demand. The accuracy of the dispatching system, derived from the accuracy of demand forecasting and the forecasting algorithm used, will determines the economic of the power system operation as well as the stability of the whole society. This paper presents a combined {epsilon}-SVR model considering seasonal proportions based on development tendencies from history data. We use one-order moving averages to produce a comparatively smooth data series, taking the averaging period as the interval that can effectively eliminate the seasonal variation. We used the smoothed data series as the training set input for the {epsilon}-SVR model and obtained the corresponding forecasting value. Afterward, we accounted for the previously removed seasonal variation. As a case, we forecast northeast electricity demand of China using the new method. We demonstrated that this simple procedure has very satisfactory overall performance by an analysis of variance with relative verification and validation. Significant reductions in forecast errors were achieved. (author)

Estabilidade fenotípica de linhagens de feijoeiro em três épocas de plantio no Estado de São Paulo Phenotypical stability of common bean lines in three growing seasons in São Paulo State, Brazil

Directory of Open Access Journals (Sweden)

SÉRGIO AUGUSTO MORAIS CARBONELL

2000-02-01

Full Text Available Com o objetivo de conhecer o comportamento de linhagens de feijoeiro nas três épocas tradicionais de plantio do Estado de São Paulo, com base em dados de estabilidade fenotípica, dois grupos de experimentos foram instalados nas épocas das águas (setembro-outubro, da seca (janeiro-fevereiro e de inverno (maio-junho. O grupo 1 (G1, com 47 experimentos, foi formado por 16 linhagens e o controle, cultivar Carioca 80SH, e o grupo 2 (G2, com 44 experimentos, formado por 11 linhagens e pelos controles, cultivares Carioca 80SH e Rosinha G2. O delineamento experimental foi o de blocos ao acaso, com cinco repetições e parcelas constituídas de uma linha de 5 m de comprimento. As análises de variância das produções de grãos foram realizadas por experimento dentro de cada grupo (G1/G2 e conjunta (geral e por época de plantio. Os parâmetros de estabilidade foram estimados pelo método proposto por Cruz et al. (1989. Foram observadas várias linhagens adaptadas em ambientes desfavoráveis em pelo menos uma época de plantio. Diversos genótipos comportaram-se como responsivos ou estáveis nos dois conjuntos de experimentos. Os resultados sugerem a possibilidade de direcionar a recomendação de cultivares, com a escolha das linhagens mais adaptadas e responsivas, específicas para as épocas de cultivo.Aiming at knowing the yield potential behavior of selected common bean lines based on data of phenotypical stability, two experimental sets were carried out in the three traditional growing seasons: rainy (September-October, dry (January-February and winter (May-June. The first set, with 47 trials, was made up of 16 experimental lines and the check Carioca 80SH cultivar; the second, with 44 trials, was made up of 11 lines and the checks Carioca 80SH and Rosinha G2 cultivars, allocated to the three growing seasons above cited. The experimental design was a randomized complete block with five replications and plots constituted of a line of 5 m of

Stem characteristics of two forage maize (Zea mays L.) cultivars varying in whole plant digestibility. IV. Changes during the growing season in anatomy and chemical composition in relation to fermentation characteristics of a lower internode

NARCIS (Netherlands)

Boon, E.J.M.C.; Struik, P.C.; Engels, F.M.; Cone, J.W.

2012-01-01

Improving digestibility of forage maize (Zea mays L.) through breeding is important to optimize the efficiency of ruminant's rations. It can partly be achieved by improving the digestibility of stem tissue, a genetically complex and diverse trait changing drastically during the growing season. We

Seasonal response of Eragrostis curvula to nitrogen | R | African ...

African Journals Online (AJOL)

On the basis of the seasonal response of Eragrostis curvula to nitrogen applied as single dressings to separate plots at the beginning of each of the six months of the growing season, it is deduced that nitrogen can profitably be applied in the Ukulinga environment from early spring though to early January. Late summer and ...

Seasonal Patterns of Soil Respiration and Related Soil Biochemical Properties under Nitrogen Addition in Winter Wheat Field.

Science.gov (United States)

Liang, Guopeng; Houssou, Albert A; Wu, Huijun; Cai, Dianxiong; Wu, Xueping; Gao, Lili; Li, Jing; Wang, Bisheng; Li, Shengping

2015-01-01

Understanding the changes of soil respiration under increasing N fertilizer in cropland ecosystems is crucial to accurately predicting global warming. This study explored seasonal variations of soil respiration and its controlling biochemical properties under a gradient of Nitrogen addition during two consecutive winter wheat growing seasons (2013-2015). N was applied at four different levels: 0, 120, 180 and 240 kg N ha(-1) year(-1) (denoted as N0, N12, N18 and N24, respectively). Soil respiration exhibited significant seasonal variation and was significantly affected by soil temperature with Q10 ranging from 2.04 to 2.46 and from 1.49 to 1.53 during 2013-2014 and 2014-2015 winter wheat growing season, respectively. Soil moisture had no significant effect on soil respiration during 2013-2014 winter wheat growing season but showed a significant and negative correlation with soil respiration during 2014-2015 winter wheat growing season. Soil respiration under N24 treatment was significantly higher than N0 treatment. Averaged over the two growing seasons, N12, N18 and N24 significantly increased soil respiration by 13.4, 16.4 and 25.4% compared with N0, respectively. N addition also significantly increased easily extractable glomalin-related soil protein (EEG), soil organic carbon (SOC), total N, ammonium N and nitrate N contents. In addition, soil respiration was significantly and positively correlated with β-glucosidase activity, EEG, SOC, total N, ammonium N and nitrate N contents. The results indicated that high N fertilization improved soil chemical properties, but significantly increased soil respiration.

Estimating Water Footprints of Vegetable Crops: Influence of Growing Season, Solar Radiation Data and Functional Unit

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Betsie le Roux

2016-10-01

Full Text Available Water footprint (WF accounting as proposed by the Water Footprint Network (WFN can potentially provide important information for water resource management, especially in water scarce countries relying on irrigation to help meet their food requirements. However, calculating accurate WFs of short-season vegetable crops such as carrots, cabbage, beetroot, broccoli and lettuce presented some challenges. Planting dates and inter-annual weather conditions impact WF results. Joining weather datasets of just rainfall, minimum and maximum temperature with ones that include solar radiation and wind-speed affected crop model estimates and WF results. The functional unit selected can also have a major impact on results. For example, WFs according to the WFN approach do not account for crop residues used for other purposes, like composting and animal feed. Using yields in dry matter rather than fresh mass also impacts WF metrics, making comparisons difficult. To overcome this, using the nutritional value of crops as a functional unit can connect water use more directly to potential benefits derived from different crops and allow more straightforward comparisons. Grey WFs based on nitrogen only disregards water pollution caused by phosphates, pesticides and salinization. Poor understanding of the fate of nitrogen complicates estimation of nitrogen loads into the aquifer.

Silvicultural options in ageing holm oak (Quercus ilex L. coppices in Gargano: results after 14 growing seasons

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Scopigno D

2008-12-01

Full Text Available In the frame of a long-term research program concerning management of ageing holm oak coppices, results available after 14 growing seasons are reported in present paper. Experimental treatments include: A 50 standards per hectare, all of the same age; B 250 standards per hectare, all of the same age; C 140 standards per hectare, with two different ages; D conversion to high forest; E natural evolution (control. A total of 15 permanent plots were established (5 treatments x 3 replicates per treatment and the experimental design used is that of randomised blocks. Based on observations concerning seedlings and shoots development and standards growth and competitive effects, the following preliminary results may be highlighted: i recovering the traditional coppicing system with few standards per hectare represents a valid option from both ecological and shoots growth point of view; the stools, with few standards per hectare, showed a larger number of sprouts, provided with a higher average height and larger diameters; ii uneven-aged standards represent a good alternative form the points of view of both landscape impact immediately after felling operations and stand resistance to climatic damages; iii a good alternative is to apply conversion treatments to high forest, whenever their site quality allows these operations.

Meteorological Influences on the Seasonality of Lyme Disease in the United States

Science.gov (United States)

Moore, Sean M.; Eisen, Rebecca J.; Monaghan, Andrew; Mead, Paul

2014-01-01

Lyme disease (Borrelia burgdorferi infection) is the most common vector-transmitted disease in the United States. The majority of human Lyme disease (LD) cases occur in the summer months, but the timing of the peak occurrence varies geographically and from year to year. We calculated the beginning, peak, end, and duration of the main LD season in 12 highly endemic states from 1992 to 2007 and then examined the association between the timing of these seasonal variables and several meteorological variables. An earlier beginning to the LD season was positively associated with higher cumulative growing degree days through Week 20, lower cumulative precipitation, a lower saturation deficit, and proximity to the Atlantic coast. The timing of the peak and duration of the LD season were also associated with cumulative growing degree days, saturation deficit, and cumulative precipitation, but no meteorological predictors adequately explained the timing of the end of the LD season. PMID:24470565

The U2U Corn Growing Degree Day tool: Tracking corn growth across the US Corn Belt

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James R. Angel

2017-01-01

Full Text Available The Corn Growing Degree Day (Corn GDD tool is a web-based product that can provide decision support on a variety of issues throughout the entire growing season by integrating current conditions, historical climate data, and projections of Corn GDD through the end of the growing season based on both National Weather Service computer model forecasts and climatology. The Corn GDD tool can help agricultural producers make a variety of important decisions before and during the growing season. This support can include: assessing the risk of early and late frosts and freezes that can cause crop damage; comparing corn hybrid maturity requirements and Corn GDD projections to select seed varieties and plan activities such as spraying; guiding marketing decisions based on historical and projected Corn GDDs when considering forward crop pricing (i.e., futures market. The Corn GDD tool provides decision support for corn producers in the central U.S. corn-producing states. Survey results, web statistics, and user feedback indicate that this tool is being actively used by decision makers.

Responses of inulin content and inulin yield of Jerusalem artichoke genotypes to seasonal environments

Science.gov (United States)

Seasonal variation (e.g. temperature and photoperiod) between growing seasons might affect inulin content and inulin yield of Jerusalem artichoke. However, there is limited information on genotypic response to seasons for inulin content and inulin yield. The objective of this study was to investig...

Seasonal patterns in soil N availability in the arctic tundra in response to accelerated snowmelt and warming

Science.gov (United States)

Darrouzet-Nardi, A.; Wallenstein, M. D.; Steltzer, H.; Sullivan, P.; Melle, C.; Segal, A.; Weintraub, M. N.

2010-12-01

Arctic soils contain large stocks of carbon (C) and may act as a significant CO2 source in response to climate warming. However, nitrogen (N) availability limits both plant growth and decomposition in many Arctic sites, and may thus be a key constraint on climate-carbon feedbacks. While current models of tundra ecosystems and their responses to climate change assume that N limits plant growth and C limits decomposition, there is strong evidence to the contrary showing that N can also limit decomposition. For example, the production of both new microbial biomass and enzymes that degrade organic matter appear to be limited by N during the summer. N availability is strongly seasonal: we have previously observed relatively high availability early in the growing season followed by a pronounced crash in tussock tundra soils. To investigate the drivers of N availability throughout the season, we used a field manipulation of tussock tundra growing season length (~4 days acceleration of snowmelt) and air temperature (open top chambers) and a laboratory soil N addition in both early and late season. Nutrient availability throughout the field season was measured at high temporal resolution (25 measurements from soil thaw through early plant senescence). Results from a laboratory experiment in which N was added to early season and late season soils suggests that soil respiration is in fact N limited at both times of the season, though this limitation is temperature dependent with effects most pronounced at 10°C. High-resolution measurements of nutrients in the soil solution and extractable N throughout the season showed that although a nutrient crash in N can be observed mid-season, N availability can still fluctuate later in the season. Finally, effects of the extended growing season and increased air temperature have so far had few effects on soil nutrient N dynamics throughout the summer growing season, suggesting either an insensitivity of N availability to these

Seasonal estimates of riparian evapotranspiration using remote and in situ measurements

Science.gov (United States)

Goodrich, D.C.; Scott, R.; Qi, J.; Goff, B.; Unkrich, C.L.; Moran, M.S.; Williams, D.; Schaeffer, S.; Snyder, K.; MacNish, R.; Maddock, T.; Pool, D.; Chehbouni, A.; Cooper, D.I.; Eichinger, W.E.; Shuttleworth, W.J.; Kerr, Y.; Marsett, R.; Ni, W.

2000-01-01

In many semi-arid basins during extended periods when surface snowmelt or storm runoff is absent, groundwater constitutes the primary water source for human habitation, agriculture and riparian ecosystems. Utilizing regional groundwater models in the management of these water resources requires accurate estimates of basin boundary conditions. A critical groundwater boundary condition that is closely coupled to atmospheric processes and is typically known with little certainty is seasonal riparian evapotranspiration ET). This quantity can often be a significant factor in the basin water balance in semi-arid regions yet is very difficult to estimate over a large area. Better understanding and quantification of seasonal, large-area riparian ET is a primary objective of the Semi-Arid Land-Surface-Atmosphere (SALSA) Program. To address this objective, a series of interdisciplinary experimental Campaigns were conducted in 1997 in the San Pedro Basin in southeastern Arizona. The riparian system in this basin is primarily made up of three vegetation communities: mesquite (Prosopis velutina), sacaton grasses (Sporobolus wrightii), and a cottonwood (Populus fremontii)/willow (Salix goodingii) forest gallery. Micrometeorological measurement techniques were used to estimate ET from the mesquite and grasses. These techniques could not be utilized to estimate fluxes from the cottonwood/willow (C/W) forest gallery due to the height (20-30 m) and non-uniform linear nature of the forest gallery. Short-term (2-4 days) sap flux measurements were made to estimate canopy transpiration over several periods of the riparian growing season. Simultaneous remote sensing measurements were used to spatially extrapolate tree and stand measurements. Scaled C/W stand level sap flux estimates were utilized to calibrate a Penman-Monteith model to enable temporal extrapolation between Synoptic measurement periods. With this model and set of measurements, seasonal riparian vegetation water use

Seasonal Patterns of Soil Respiration and Related Soil Biochemical Properties under Nitrogen Addition in Winter Wheat Field

Science.gov (United States)

Liang, Guopeng; Houssou, Albert A.; Wu, Huijun; Cai, Dianxiong; Wu, Xueping; Gao, Lili; Li, Jing; Wang, Bisheng; Li, Shengping

2015-01-01

Understanding the changes of soil respiration under increasing N fertilizer in cropland ecosystems is crucial to accurately predicting global warming. This study explored seasonal variations of soil respiration and its controlling biochemical properties under a gradient of Nitrogen addition during two consecutive winter wheat growing seasons (2013–2015). N was applied at four different levels: 0, 120, 180 and 240 kg N ha-1 year-1 (denoted as N0, N12, N18 and N24, respectively). Soil respiration exhibited significant seasonal variation and was significantly affected by soil temperature with Q10 ranging from 2.04 to 2.46 and from 1.49 to 1.53 during 2013–2014 and 2014–2015 winter wheat growing season, respectively. Soil moisture had no significant effect on soil respiration during 2013–2014 winter wheat growing season but showed a significant and negative correlation with soil respiration during 2014–2015 winter wheat growing season. Soil respiration under N24 treatment was significantly higher than N0 treatment. Averaged over the two growing seasons, N12, N18 and N24 significantly increased soil respiration by 13.4, 16.4 and 25.4% compared with N0, respectively. N addition also significantly increased easily extractable glomalin-related soil protein (EEG), soil organic carbon (SOC), total N, ammonium N and nitrate N contents. In addition, soil respiration was significantly and positively correlated with β-glucosidase activity, EEG, SOC, total N, ammonium N and nitrate N contents. The results indicated that high N fertilization improved soil chemical properties, but significantly increased soil respiration. PMID:26629695

Short-term Effect of Nitrogen Addition on Microbial and Root Respiration in an Alpine Spruce Ecosystem

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Jian Wang1

2017-03-01

Full Text Available Soil respiration plays an important role in the carbon (C flux of the global C cycle and is greatly affected by nitrogen (N additions in the form of deposition or fertilization. The aim of this study was to investigate the response of total soil respiration (Rs, microbial respiration (Rm, and root respiration (Rr to short-term N addition and the potential mechanisms of short-term N deposition influencing soil respiration in an alpine spruce ecosystem. Four N treatment levels (0, 50, 100, 150 kg N ha-1 year-1 were applied monthly in a Picea balfouriana (commonly known as "alpine spruce" plantation beginning in November 2013 and Rs, Rm, and Rr were measured from May to November 2014. The results show that simulated N depositions stimulate Rs, Rm, and Rr and the beneficial effects decreased along N gradients from hourly to seasonal scales. The seasonal temperature coefficients (Q10 of Rs, Rm, and Rr ranged from 2.50 to 3.8, 2.99 to 4.63, and 1.86 to 2.96, while the diurnal Q10 ranged from 1.71 to 2.04, 1.89 to 2.32, 1.42 to 1.75, and there was a similar trend with soil respiration along N gradients. In addition, Rr showed significant positive correlation with fine root biomass, and Rm was likely driven by soil enzyme related to the microbial C cycle in the growing season. Our results indicate that short-term N addition stimulated fine root biomass and soil enzymatic activity to bring about a potential increase in soil respiration rates under low-N addition, while the opposite occurred under high-N addition.

REPRODUCTIVE SEASONALITY OF SHEEP IN MEXICO

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Jaime Arroyo

2011-07-01

Full Text Available In order to discuss and analyze the available information concerning the seasonal breeding behavior of sheep in Mexico, this review was conducted. We analyzed the neuroendocrine basis that modulate the annual reproductive cycle in sheep and then discussed the degree of reproductive seasonality in Creole sheep wool, breeds originating in high latitudes and hair sheep, mainly in Pelibuey ewes. The Creole sheep wool show continuous annual reproductive activity and short seasonal anestrous. The females of northern origin, express seasonal reproductive activity, similar to that observed in individuals geographically located at latitudes above 35º. Pelibuey sheep show variable annual reproductive behavior with reduced anestrus or lack thereof.  It is suggested that the neuroendocrine mechanisms regulating seasonal anestrus in ewes, are active in the sheep of northern origin that live in Mexico, in a manner contrary is not activated in Creole and hair sheep.

Seasonal Occurrence of Key Arthropod Pests and Beneficial Insects in Michigan High Tunnel and Field Grown Raspberries.

Science.gov (United States)

Leach, Heather; Isaacs, Rufus

2018-06-06

Berry crops are increasingly produced in high tunnels, which provide growers with the opportunity to extend their production season. This is particularly beneficial for the northern region of the United States with short and unpredictable growing seasons and where rainfall limits fruit quality. However, little is known about the effect of high tunnels on the community of pests, natural enemies, or pollinators, especially in berry crops, and there are few reports of the insect community in raspberries in this region. We compared the abundance of these insects during two growing seasons in field-grown and tunnel-grown floricane and primocane producing raspberries through direct observation and trapping at five sites in southwestern and central Michigan. We found eight key pests, including spotted wing Drosophila, leafhoppers, and thrips, and seven key natural enemies including parasitoid wasps, spiders, and lacewings, that were common across all sites. Pest populations were up to 6.6 times higher in tunnels, and pests typical of greenhouse systems became more dominant in this environment. Natural enemies observed on plants under tunnels were also more abundant than in the field, but this trend was reversed for natural enemies trapped on yellow sticky cards. There was also a reduction of both honey bees and wild bees under the high tunnels, which was balanced by use of commercial bumble bees. These data not only provide much-needed information on the phenology of the insect community on raspberry plantings, they also highlight the entomological implications of protected raspberry culture.

GENETIC DIVERGENCE AMONG COTTON GENOTYPES GROWN IN THE MAIN SEASON AND OFF SEASON

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THIAGO ALEXANDRE SANTANA GILIO

2017-01-01

Full Text Available The objective of this work was to evaluate the agronomic performance and estimate the genetic divergence of 18 cotton genotypes grown in the main season (sowed in December, 2012 and off season (sowed in January, 2013, considering their agronomic characteristics and resistance to Ramularia leaf spot. A randomized block experimental design was used, with five replications. The characteristics evaluated were plant height, first branch height, position of first fruiting branch, height of first fruiting branch, length between nodes, number of nodes, average number of bolls per plant, average boll weight, area under the disease progress curve (AUDPC related to the Ramularia leaf spot severity, weight of 100 - seed from the plant middle third, fiber percentage, average production per plant, yield and cotton fiber quality. The results were subjected to individual and joint analysis of variance and the genetic divergence was estimated according to multivariate procedures (Mahalanobis' generalized distance and Tocher's optimization method. The dissimilarity matrices were summed to estimate the genetic divergence, considering both growing periods. Genetic variability was found among the genotypes evaluated, in both the main season and off season. The characteristic that most contributed to the genetic divergence in the main season was the production per plant and, in the off season, was the fiber percentage. According to the results of the present work, the crosses between the genotypes BRS - 335 and FMT - 707; FM - 910 and FMT - 707; and IMA - 08 - 12427 and FMT - 707 are recommended.

Volatile Transport in Pluto's Super Seasons

Science.gov (United States)

Earle, Alissa M.; Binzel, Richard; Young, Leslie; Stern, S. Alan; Olkin, Catherine B.; Ennico, Kimberly; Moore, Jeffrey M.; Weaver, Harold A.; NASA New Horizons Composition Team, The NASA New Horizons GGI Team

2016-10-01

The data returned from NASA's New Horizons' reconnaissance of the Pluto system shows striking albedo variations from polar to equatorial latitudes as well as sharp boundaries for longitudinal variations. Pluto has a high obliquity (currently around 119 degrees) which varies by more than 23 degrees (between roughly 103 and 127 degrees) over a period of less than 3 million years. These obliquity properties, combined with Pluto's orbital regression in longitude of perihelion (360 degrees over 3.7 million years), create epochs of "Super Seasons" on Pluto. A "Super Season" occurs, for example, when Pluto happens to be pole-on towards the Sun at the same time as perihelion. In such a case, one pole experiences a short, intense summer (relative to its long-term average) followed by a longer than average period of winter darkness. By complement, the other pole experiences a much longer, but less intense summer and short winter season. We explore the relationship between albedo variations and volatile transport for the current epoch as well as historical epochs during which Pluto experienced these "Super Seasons". Our investigation suggests Pluto's orbit creates the potential for runaway albedo variations, particularly in the equatorial region, which would create and support stark longitudinal contrasts like the ones we see between the informally named Tombaugh and Cthulhu Regios.This work was supported by the NASA New Horizons mission.

Trends in land surface phenology and atmospheric CO2 seasonality in the Northern Hemisphere terrestrial ecosystems

Science.gov (United States)

Gonsamo, A.; Chen, J. M.

2017-12-01

Northern terrestrial ecosystems have shown global warming-induced advances in start, delays in end, and thus increased lengths of growing season and gross photosynthesis in recent decades. The tradeoffs between seasonal dynamics of two opposing fluxes, CO2 uptake through photosynthesis and release through respiration, determine the influence of the terrestrial ecosystems on the atmospheric CO2 concentration and 13C/12C isotope ratio seasonality. Atmospheric CO2 and 13C/12C seasonality is controlled by vegetation phenology, but is not identical because growth will typically commence some time before and terminate some time after the net carbon exchange changes sign in spring and autumn, respectively. Here, we use 34-year satellite normalized difference vegetation index (NDVI) observations to determine how changes in vegetation productivity and phenology affect both the atmospheric CO2 and 13C/12C seasonality. Differences and similarities in recent trends of CO2 and 13C/12C seasonality and vegetation phenology will be discussed. Furthermore, we use the NDVI observations, and atmospheric CO2 and 13C/12C data to show the trends and variability of the timing of peak season plant activity. Preliminary results show that the peak season plant activity of the Northern Hemisphere extra-tropical terrestrial ecosystems is shifting towards spring, largely in response to the warming-induced advance of the start of growing season. Besides, the spring-ward shift of the peak plant activity is contributing the most to the increasing peak season productivity. In other words, earlier start of growing season is highly linked to earlier arrival of peak of season and higher NDVI. Changes in the timing of peak season plant activity are expected to disrupt the synchrony of biotic interaction and exert strong biophysical feedbacks on climate by modifying the surface albedo and energy budget.

Seasonal phenology and species composition of the aphid fauna in a northern crop production area.

Directory of Open Access Journals (Sweden)

Sascha M Kirchner

Full Text Available BACKGROUND: The species diversity of aphids and seasonal timing of their flight activity can have significant impacts on crop production, as aphid species differ in their ability to transmit plant viruses and flight timing affects virus epidemiology. The aim of the study was to characterise the species composition and phenology of aphid fauna in Finland in one of the northernmost intensive crop production areas of the world (latitude 64°. METHODOLOGY/PRINCIPAL FINDINGS: Flight activity was monitored in four growing seasons (2007-010 using yellow pan traps (YPTs placed in 4-8 seed potato fields and a Rothamsted suction trap. A total of 58,528 winged aphids were obtained, identified to 83 taxa based on morphology, and 34 species were additionally characterised by DNA barcoding. Seasonal flight activity patterns analysed based on YPT catch fell into three main phenology clusters. Monoecious taxa showed early or middle-season flight activity and belonged to species living on shrubs/trees or herbaceous plants, respectively. Heteroecious taxa occurred over the entire potato growing season (ca. 90 days. Abundance of aphids followed a clear 3-year cycle based on suction trap data covering a decade. Rhopalosiphum padi occurring at the end of the potato growing season was the most abundant species. The flight activity of Aphis fabae, the main vector of Potato virus Y in the region, and Aphis gossypii peaked in the beginning of potato growing season. CONCLUSIONS/SIGNIFICANCE: Detailed information was obtained on phenology of a large number aphid species, of which many are agriculturally important pests acting as vectors of plant viruses. Aphis gossypii is known as a pest in greenhouses, but our study shows that it occurs also in the field, even far in the north. The novel information on aphid phenology and ecology has wide implications for prospective pest management, particularly in light of climate change.

Seasonal and scale-dependent variability in nutrient- and allelopathy-mediated macrophyte–phytoplankton interactions

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Lombardo P.

2013-08-01

Full Text Available macrophyte–phytoplankton interactions were investigated using a dual laboratory and field approach during a growing season, with responses quantified as changes in biomass. Short-term, close-range interactions in laboratory microcosms always led to mutual exclusion of macrophytes (Elodea canadensis or Ceratophyllum demersum and algae (Raphidocelis subcapitata, Fistulifera pelliculosa or cyanobacteria (Synechococcus leopoliensis, suggesting regulation by positive feedback mechanisms, progressively establishing and reinforcing a “stable state”. Laboratory results suggest that close-range regulation of R. subcapitata and F. pelliculosa by macrophytes was primarily via nutrient (N, P mediation. Sprig-produced allelochemicals may have contributed to inhibition of S. leopoliensis in C. demersum presence, while S. leopoliensis was apparently enhanced by nutrients leaked by subhealthy (discolored leaves; biomass loss E. canadensis. Seasonal changes in algal growth suppression were correlated with sprig growth. Marginal differences in in situ phytoplankton patterns inside and outside monospecific macrophyte stands suggest that the nutrient- and/or allelopathy-mediated close-range mechanisms observed in the laboratory did not propagate at the macrophyte-stand scale. Factors operating at a larger scale (e.g., lake trophic state, extent of submerged vegetation coverage appear to override in situ macrophyte–phytoplankton close-range interactions.

Reconstructing the δ(18) O of atmospheric water vapour via the CAM epiphyte Tillandsia usneoides: seasonal controls on δ(18) O in the field and large-scale reconstruction of δ(18) Oa.

Science.gov (United States)

Helliker, Brent R

2014-03-01

Using both oxygen isotope ratios of leaf water (δ(18) OL ) and cellulose (δ(18) OC ) of Tillandsia usneoides in situ, this paper examined how short- and long-term responses to environmental variation and model parameterization affected the reconstruction of the atmospheric water vapour (δ(18) Oa ). During sample-intensive field campaigns, predictions of δ(18) OL matched observations well using a non-steady-state model, but the model required data-rich parameterization. Predictions from the more easily parameterized maximum enrichment model (δ(18) OL-M ) matched observed δ(18) OL and observed δ(18) Oa when leaf water turnover was less than 3.5 d. Using the δ(18) OL-M model and weekly samples of δ(18) OL across two growing seasons in Florida, USA, reconstructed δ(18) Oa was -12.6 ± 0.3‰. This is compared with δ(18) Oa of -12.4 ± 0.2‰ resolved from the growing-season-weighted δ(18) OC . Both of these values were similar to δ(18) Oa in equilibrium with precipitation, -12.9‰. δ(18) Oa was also reconstructed through a large-scale transect with δ(18) OL and the growing-season-integrated δ(18) OC across the southeastern United States. There was considerable large-scale variation, but there was regional, weather-induced coherence in δ(18) Oa when using δ(18) OL . The reconstruction of δ(18) Oa with δ(18) OC generally supported the assumption of δ(18) Oa being in equilibrium with precipitation δ(18) O (δ(18) Oppt ), but the pool of δ(18) Oppt with which δ(18) Oa was in equilibrium - growing season versus annual δ(18) Oppt - changed with latitude. © 2013 John Wiley & Sons Ltd.

RFRP neurons - the doorway to understanding seasonal reproduction in mammals

Directory of Open Access Journals (Sweden)

Jo Beldring Henningsen

2016-05-01

Full Text Available Seasonal control of reproduction is critical for the perpetuation of species living in temperate zones that display major changes in climatic environment and availability of food resources. In mammals, seasonal cues are mainly provided by the annual change in the 24h light/dark ratio (i.e. photoperiod, which is translated into the nocturnal production of the pineal hormone melatonin. The annual rhythm in this melatonin signal acts as a synchronizer ensuring that breeding occurs when environmental conditions favor survival of the offspring. Although specific mechanisms might vary among seasonal species, the hypothalamic RF (Arg-Phe amide-related peptides (RFRP-1 and -3 are believed to play a critical role in the central control of seasonal reproduction and in all seasonal species investigated, the RFRP system is persistently inhibited in short photoperiod. Central chronic administration of RFRP-3 in short day-adapted male Syrian hamsters fully reactivates the reproductive axis despite photoinhibitory conditions, which highlights the importance of the seasonal changes in RFRP expression for proper regulation of the reproductive axis. The acute effects of RFRP peptides, however, depend on species, photoperiod and recent studies point towards a different role of RFRP in regulating female reproductive activity. In this review we summarize the recent advances made to understand the role and underlying mechanisms of RFRP in the seasonal control of reproduction, primarily focusing on mammalian species.

California Hass Avocado: Profiling of Carotenoids, tocopherol, fatty acid, and fat content during maturation and from different growing areas

Science.gov (United States)

Lu, Qing-Yi; Zhang, Yanjun; Wang, Yue; Wang, David; Lee, Ru-po; Gao, Kun; Byrns, Russell; Heber, David

2009-01-01

The California Hass avocado (Persea Americana) is an example of a domesticated berry fruit that matures on the tree during its growing season but ripens only after being harvested. Avocados are typically harvested multiple times during the growing season in California. Previous research has demonstrated potential health benefits of avocados and extracts of avocado against inflammation and cancer cell growth, but seasonal variations in the phytochemical profile of the fruits being studied may affect the results obtained in future research. Therefore in the present study, avocados were harvested in January, April, July and September 2008 from four different growing locations in California (San Luis Obispo, Ventura, Riverside and San Diego), and analyzed fortotal fat content, fatty acid profile, carotenoids and vitamin E. A significant increase in total carotenoid and fat content of avocados from all regions was noted as the season progressed from January to September. Four carotenoids not previously described in the avocado were quantified. The total content of carotenoids was highly correlated with total fat content (r=0.99, pavocado.. Future clinical research on the health benefits of the avocado should specify the time of harvest, degree of ripening, growing area and the total phytochemical profile of the fruit or extract being studied. These steps will enable researchers to account for potential nutrient-nutrient interactions that might affect the research outcomes. PMID:19813713

Seasonal differences in leaf-level physiology give lianas a competitive advantage over trees in a tropical seasonal forest.

Science.gov (United States)

Cai, Zhi-Quan; Schnitzer, Stefan A; Bongers, Frans

2009-08-01

Lianas are an important component of most tropical forests, where they vary in abundance from high in seasonal forests to low in seasonal forests. We tested the hypothesis that the physiological ability of lianas to fix carbon (and thus grow) during seasonal drought may confer a distinct advantage in seasonal tropical forests, which may explain pan-tropical liana distributions. We compared a range of leaf-level physiological attributes of 18 co-occurring liana and 16 tree species during the wet and dry seasons in a tropical seasonal forest in Xishuangbanna, China. We found that, during the wet season, lianas had significantly higher CO(2) assimilation per unit mass (A(mass)), nitrogen concentration (N(mass)), and delta(13)C values, and lower leaf mass per unit area (LMA) than trees, indicating that lianas have higher assimilation rates per unit leaf mass and higher integrated water-use efficiency (WUE), but lower leaf structural investments. Seasonal variation in CO(2) assimilation per unit area (A(area)), phosphorus concentration per unit mass (P(mass)), and photosynthetic N-use efficiency (PNUE), however, was significantly lower in lianas than in trees. For instance, mean tree A(area) decreased by 30.1% from wet to dry season, compared with only 12.8% for lianas. In contrast, from the wet to dry season mean liana delta(13)C increased four times more than tree delta(13)C, with no reduction in PNUE, whereas trees had a significant reduction in PNUE. Lianas had higher A(mass) than trees throughout the year, regardless of season. Collectively, our findings indicate that lianas fix more carbon and use water and nitrogen more efficiently than trees, particularly during seasonal drought, which may confer a competitive advantage to lianas during the dry season, and thus may explain their high relative abundance in seasonal tropical forests.

Mapping Changes in Area and the Cropping Season of Irrigated Rice in Senegal and Mauritania between 2003 and 2014 Using the PhenoRice Algorithm and MODIS Imagery

Science.gov (United States)

Zwart, S.; Busetto, L.; Diagne, M.; Boschetti, M.; Nelson, A.

2017-12-01

between years, was captured with high accuracy. No significant changes in the onset of the growing season were detected. However, the length of the growing season was found to be steadily decreasing from 121 days in 2003 to 114 days in 2016 (r2 = 0.67). This is likely due to varietal improvement and preference of farmers for short duration varieties to allow double cropping.

Kisspeptin and the seasonal control of reproduction in hamsters

DEFF Research Database (Denmark)

Simonneaux, Valérie; Ansel, Laura; Revel, Florent G

2008-01-01

-expressing neurons, which were recently shown to be implicated in the regulation of GnRH release. Hamsters are seasonal rodents which are sexually active in long photoperiod and quiescent in short photoperiod. The photoperiodic information is transmitted to the reproductive system by melatonin, a pineal...... hormone whose secretion is adjusted to night length. The photoperiodic variation in circulating melatonin has been shown to synchronize reproductive activity with seasons, but the mechanisms involved in this effect of melatonin were so far unknown. Recently we have observed that Kiss1 mRNA level...... in the arcuate nucleus of the Syrian hamster is lower in short photoperiod, when animals are sexually quiescent. Notably, intracerebroventricular infusion of Kiss1 gene product, kisspeptin, in hamsters kept in short photoperiod is able to override the inhibitory photoperiod and to reactivate sexual activity...

Water policy reform in Australia: lessons from the Victorian seasonal water market

OpenAIRE

Brennan, Donna C.

2006-01-01

The nature of the seasonal water market is examined using a theoretical model and empirical evidence from the Victorian market. Drivers of the seasonal opportunity cost of water include the underlying nature of investment in the industry made in the context of risky entitlement yields; and the timing and nature of information regarding seasonal water availability and rainfall. Seasonal water markets facilitate the reallocation of water availability according to this short-run opportunity cost...

Boll weevil within season and off-season activity monitored using a pheromone-and-glue reusable tube trap

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Robério Carlos dos Santos Neves

Full Text Available ABSTRACT: The boll weevil colonizes cotton fields as early as cotton squaring, causing significant losses due to feeding and protected development inside fruiting structures throughout crop phenology. Successful control depends on control of adults and their accurate detection when they colonize the crops. The commercial trap and boll weevil attract-and-control tubes (BWACT are the only available tools to monitor and attract-and-kill boll weevil, despite limitation in efficacy, and insecticide in BWACT is not allowed in organic production. A grandlure-and-glue reusable and insecticide-free tube (GGT made with polyvinyl chloride tube, smeared with entomological glue, and lured with pheromone was tested to detect boll weevil activity across various seasons. Boll weevil showed activity during growing season and off-season from 2009 to 2012 in the Semiarid and with higher numbers captured in GGT in comparisons to commercial traps. GGT was able to detect early weevils in the field right after planting. Further, the overall averages resulted in 34-, 16.8-, and 7.5-times more weevils captured in GGTs compared to the traps during stalk destruction in the Semiarid 2011 and Cerrado season 2012/13 and during the harvesting period in the Cerrado season 2011/12, respectively. Therefore, boll weevils were captured actively during season and off-season and early captures obtained in GGT compared to traps showed a better correlation between captures and square damage.

Extended season for northern butterflies.

Science.gov (United States)

Karlsson, Bengt

2014-07-01

Butterflies are like all insects in that they are temperature sensitive and a changing climate with higher temperatures might effect their phenology. Several studies have found support for earlier flight dates among the investigated species. A comparative study with data from a citizen science project, including 66 species of butterflies in Sweden, was undertaken, and the result confirms that most butterfly species now fly earlier during the season. This is especially evident for butterflies overwintering as adults or as pupae. However, the advancement in phenology is correlated with flight date, and some late season species show no advancement or have even postponed their flight dates and are now flying later in the season. The results also showed that latitude had a strong effect on the adult flight date, and most of the investigated species showed significantly later flights towards the north. Only some late flying species showed an opposite trend, flying earlier in the north. A majority of the investigated species in this study showed a general response to temperature and advanced their flight dates with warmer temperatures (on average they advanced their flight dates by 3.8 days/°C), although not all species showed this response. In essence, a climate with earlier springs and longer growing seasons seems not to change the appearance patterns in a one-way direction. We now see butterflies on the wings both earlier and later in the season and some consequences of these patterns are discussed. So far, studies have concentrated mostly on early season butterfly-plant interactions but also late season studies are needed for a better understanding of long-term population consequences.

The role of seasonal, climatic and meteorological conditions in modifying nuclear accident consequences

International Nuclear Information System (INIS)

Mueller, H.; Proehl, G.

1989-01-01

One of the most important factors which influence the ingestion doses after an accidental release of radionuclides is the season of the year at which the release occurs. This is demonstrated with some examples for German conditions. This seasonal effect depends strongly on the growing periods of the different plants. Therefore it is influenced by the climatic conditions which vary to a large degree in the different countries causing very different growing periods. The influence of the meteorological conditions during and after the passing of a radioactive cloud on the initial contamination of the plants is discussed

Monitoring Start of Season in Alaska

Science.gov (United States)

Robin, J.; Dubayah, R.; Sparrow, E.; Levine, E.

2006-12-01

In biomes that have distinct winter seasons, start of spring phenological events, specifically timing of budburst and green-up of leaves, coincides with transpiration. Seasons leave annual signatures that reflect the dynamic nature of the hydrologic cycle and link the different spheres of the Earth system. This paper evaluates whether continuity between AVHRR and MODIS normalized difference vegetation index (NDVI) is achievable for monitoring land surface phenology, specifically start of season (SOS), in Alaska. Additionally, two thresholds, one based on NDVI and the other on accumulated growing degree-days (GDD), are compared to determine which most accurately predicts SOS for Fairbanks. Ratio of maximum greenness at SOS was computed from biweekly AVHRR and MODIS composites for 2001 through 2004 for Anchorage and Fairbanks regions. SOS dates were determined from annual green-up observations made by GLOBE students. Results showed that different processing as well as spectral characteristics of each sensor restrict continuity between the two datasets. MODIS values were consistently higher and had less inter-annual variability during the height of the growing season than corresponding AVHRR values. Furthermore, a threshold of 131-175 accumulated GDD was a better predictor of SOS for Fairbanks than a NDVI threshold applied to AVHRR and MODIS datasets. The NDVI threshold was developed from biweekly AVHRR composites from 1982 through 2004 and corresponding annual green-up observations at University of Alaska-Fairbanks (UAF). The GDD threshold was developed from 20+ years of historic daily mean air temperature data and the same green-up observations. SOS dates computed with the GDD threshold most closely resembled actual green-up dates observed by GLOBE students and UAF researchers. Overall, biweekly composites and effects of clouds, snow, and conifers limit the ability of NDVI to monitor phenological changes in Alaska.

Temporal changes affect plant chemistry and tritrophic interactions

NARCIS (Netherlands)

Gols, R.; Raaijmakers, C.E.; Van Dam, N.M.; Dicke, M.; Bukovinszky, T.; Harvey, J.A.

2007-01-01

In nature, individuals of short-lived plant species (e.g. annuals, biennials) may grow at different times during the growing season. These plants are therefore exposed to different season-related conditions such as light and temperature, which in turn may have consequences for primary and secondary

Interactive effects of UV radiation and reduced precipitation on the seasonal leaf phenolic content/composition and the antioxidant activity of naturally growing Arbutus unedo plants.

Science.gov (United States)

Nenadis, Nikolaos; Llorens, Laura; Koufogianni, Agathi; Díaz, Laura; Font, Joan; Gonzalez, Josep Abel; Verdaguer, Dolors

2015-12-01

The effects of UV radiation and rainfall reduction on the seasonal leaf phenolic content/composition and antioxidant activity of the Mediterranean shrub Arbutus unedo were studied. Naturally growing plants of A. unedo were submitted to 97% UV-B reduction (UVA), 95% UV-A+UV-B reduction (UV0) or near-ambient UV levels (UVBA) under two precipitation regimes (natural rainfall or 10-30% rainfall reduction). Total phenol, flavonol and flavanol contents, levels of eight phenols and antioxidant activity [DPPH(●) radical scavenging and Cu (II) reducing capacity] were measured in sun-exposed leaves at the end of four consecutive seasons. Results showed a significant seasonal variation in the leaf content of phenols of A. unedo, with the lowest values found in spring and the highest in autumn and/or winter. Leaf ontogenetic development and/or a possible effect of low temperatures in autumn/winter may account for such findings. Regardless of the watering regime and the sampling date, plant exposure to UV-B radiation decreased the total flavanol content of leaves, while it increased the leaf content in quercitrin (the most abundant quercetin derivative identified). By contrast, UV-A radiation increased the leaf content of theogallin, a gallic acid derivative. Other phenolic compounds (two quercetin derivatives, one of them being avicularin, and one kaempferol derivative, juglanin), as well as the antioxidant activity of the leaves, showed different responses to UV radiation depending on the precipitation regime. Surprisingly, reduced rainfall significantly decreased the total amount of quantified quercetin derivatives as well as the DPPH scavenging activity in A. unedo leaves. To conclude, present findings indicate that leaves of A. unedo can be a good source of antioxidants throughout the year, but especially in autumn and winter. Copyright © 2015 Elsevier B.V. All rights reserved.

Effects of short term and long term soil warming on ecosystem phenology of a sub-arctic grassland: an NDVI-based approach

Science.gov (United States)

Leblans, Niki; Sigurdsson, Bjarni D.; Janssens, Ivan A.

2014-05-01

Phenology has been defined as the study of the timing of recurring biological events and the causes of their timing with regard to abiotic and biotic factors. Ecosystem phenology, including the onset of the growing season and its senescence in autumn, plays an important role in the carbon, water and energy exchange between biosphere and atmosphere at higher latitudes. Factors that influence ecosystem phenology can therefore induce important climate-controlling feedback mechanisms. Global surface temperatures have been predicted to increase in the coming decades. Hence, a better understanding of the effect of temperature on ecosystem phenology is essential. Natural geothermal soil temperature gradients in Iceland offer a unique opportunity to study the soil temperature (Ts) dependence of ecosystem phenology and distinguish short-term (transient) warming effects (in recently established Ts gradients) from long-term (permanent) effects (in centuries-old Ts gradients). This research was performed in the framework of an international research project (ForHot; www.forhot.is). ForHot includes two natural grassland areas with gradients in Ts, dominated by Festuca sp., Agrostis sp.. The first warmed area was created in 2008, when an earthquake in S-Iceland caused geothermal systems to be shifted to previously cold soils. The second area is located about 3 km away from this newly warmed grassland. For this area, there are proofs that the natural soil warming has been continuous for at least 300 year. In the present study we focus on Ts elevation gradients of +0 to +10°C. The experiment consists of five transects with five temperature levels (+0,+1,+3,+5 and +10°C) in the two aforementioned grassland ecosystems (n=25 in each grassland). From April until November 2013, weekly measurements of the normalized difference vegetation index (NDVI) were taken. In the short-term warmed grassland, the greening of the vegetation was 36 days advanced at +10°C Ts and the date of 50

Beyond leaf color: Comparing camera-based phenological metrics with leaf biochemical, biophysical, and spectral properties throughout the growing season of a temperate deciduous forest

Science.gov (United States)

Yang, Xi; Tang, Jianwu; Mustard, John F.

2014-03-01

Plant phenology, a sensitive indicator of climate change, influences vegetation-atmosphere interactions by changing the carbon and water cycles from local to global scales. Camera-based phenological observations of the color changes of the vegetation canopy throughout the growing season have become popular in recent years. However, the linkages between camera phenological metrics and leaf biochemical, biophysical, and spectral properties are elusive. We measured key leaf properties including chlorophyll concentration and leaf reflectance on a weekly basis from June to November 2011 in a white oak forest on the island of Martha's Vineyard, Massachusetts, USA. Concurrently, we used a digital camera to automatically acquire daily pictures of the tree canopies. We found that there was a mismatch between the camera-based phenological metric for the canopy greenness (green chromatic coordinate, gcc) and the total chlorophyll and carotenoids concentration and leaf mass per area during late spring/early summer. The seasonal peak of gcc is approximately 20 days earlier than the peak of the total chlorophyll concentration. During the fall, both canopy and leaf redness were significantly correlated with the vegetation index for anthocyanin concentration, opening a new window to quantify vegetation senescence remotely. Satellite- and camera-based vegetation indices agreed well, suggesting that camera-based observations can be used as the ground validation for satellites. Using the high-temporal resolution dataset of leaf biochemical, biophysical, and spectral properties, our results show the strengths and potential uncertainties to use canopy color as the proxy of ecosystem functioning.

Cabernet Sauvignon grapevine grafted onto rootstocks during the autumn-winter season in southeastern Brazilian

Directory of Open Access Journals (Sweden)

Claudia Rita de Souza

2015-02-01

Full Text Available The change of grape (Vitis vinifera harvest from summer to winter through double pruning management has improved the fine wine quality in southern Brazil. High altitude, late cultivar and grafting combination all need to be investigated to optimize this new viticulture management. For this purpose, this study was carried out during the 2011 and 2012 growing seasons in a high altitude region of the state of Minas Gerais, Brazil, using eight grafting combinations for five year old Cabernet Sauvignon vines. The stem water potential, photosynthetic rate and stomatal conductance were not affected by rootstock type. The rootstocks IAC 766 and 101-14 induced, respectively, the highest and lowest vegetative vigor in Cabernet Sauvignon, as shown by leaf area and pruning weight. In the 2011 growing season, the leaf chlorophyll contents were increased in IAC 766, whereas vines grafted onto 101-14 accumulated more leaf starch, probably due to reduced vegetative and reproductive growth. In general, rootstocks K5BB, 1045P, SO4 and IAC 766 had the highest yield as compared to 1103P and 101-14. Berries from the grapevine with the highest yield did not differ in pH, total soluble solids and acidity. The rootstocks did not influence the anthocyanins and total phenols in both growing seasons. Quality parameters were better in the 2011 than in the 2012 growing season due to better climatic conditions, mainly less rainfall. The best performance of Cabernet Sauvignon was achieved when grafted onto K5BB, 1045P, SO4 and IAC 766 rootstocks.

Phenological mismatch in coastal western Alaska may increase summer season greenhouse gas uptake

Science.gov (United States)

Kelsey, Katharine C.; Leffler, A. Joshua; Beard, Karen H.; Choi, Ryan T.; Schmutz, Joel A.; Welker, Jeffery M.

2018-04-01

High latitude ecosystems are prone to phenological mismatches due to climate change- driven advances in the growing season and changing arrival times of migratory herbivores. These changes have the potential to alter biogeochemical cycling and contribute to feedbacks on climate change by altering greenhouse gas (GHG) emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) through large regions of the Arctic. Yet the effects of phenological mismatches on gas fluxes are currently unexplored. We used a three-year field experiment that altered the start of the growing season and timing of grazing to investigate how phenological mismatch affects GHG exchange. We found early grazing increased mean GHG emission to the atmosphere despite lower CH4 emissions due to grazing-induced changes in vegetation structure that increased uptake of CO2. In contrast, late grazing reduced GHG emissions because greater plant productivity led to an increase in CO2 uptake that overcame the increase in CH4 emission. Timing of grazing was an important control on both CO2 and CH4 emissions, and net GHG exchange was the result of opposing fluxes of CO2 and CH4. N2O played a negligible role in GHG flux. Advancing the growing season had a smaller effect on GHG emissions than changes to timing of grazing in this study. Our results suggest that a phenological mismatch that delays timing of grazing relative to the growing season, a change which is already developing along in western coastal Alaska, will reduce GHG emissions to the atmosphere through increased CO2 uptake despite greater CH4 emissions.

Phenological mismatch in coastal western Alaska may increase summer season greenhouse gas uptake

Science.gov (United States)

Kelsey, Katharine C.; Leffler, A. Joshua; Beard, Karen H.; Choi, Ryan T.; Schmutz, Joel A.; Welker, Jeffery M.

2018-01-01

High latitude ecosystems are prone to phenological mismatches due to climate change- driven advances in the growing season and changing arrival times of migratory herbivores. These changes have the potential to alter biogeochemical cycling and contribute to feedbacks on climate change by altering greenhouse gas (GHG) emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) through large regions of the Arctic. Yet the effects of phenological mismatches on gas fluxes are currently unexplored. We used a three-year field experiment that altered the start of the growing season and timing of grazing to investigate how phenological mismatch affects GHG exchange. We found early grazing increased mean GHG emission to the atmosphere despite lower CH4 emissions due to grazing-induced changes in vegetation structure that increased uptake of CO2. In contrast, late grazing reduced GHG emissions because greater plant productivity led to an increase in CO2 uptake that overcame the increase in CH4 emission. Timing of grazing was an important control on both CO2 and CH4 emissions, and net GHG exchange was the result of opposing fluxes of CO2 and CH4. N2O played a negligible role in GHG flux. Advancing the growing season had a smaller effect on GHG emissions than changes to timing of grazing in this study. Our results suggest that a phenological mismatch that delays timing of grazing relative to the growing season, a change which is already developing along in western coastal Alaska, will reduce GHG emissions to the atmosphere through increased CO2 uptake despite greater CH4 emissions.

Monitoring Grassland Tourist Season of Inner Mongolia, China Using Remote Sensing Data

Directory of Open Access Journals (Sweden)

Quansheng Ge

2014-01-01

Full Text Available Phenology-driven events, such as spring wildflower displays or fall tree colour, are generally appreciated by tourists for centuries around the world. Monitoring when tourist seasons occur using satellite data has been an area of growing research interest in recent decades. In this paper, a valid methodology for detecting the grassland tourist season using remote sensing data was presented. On average, the beginning, the best, and the end of grassland tourist season of Inner Mongolia, China, occur in late June (±30 days, early July (±30 days, and late July (±50 days, respectively. In south region, the grassland tourist season appeared relatively late. The length of the grassland tourist season is about 90 days with strong spatial trend. South areas exhibit longer tourist season.

[Effects of conservation tillage on soil CO2 and N2O emission during the following winter-wheat season].

Science.gov (United States)

Pan, Ying; Hu, Zheng-Hu; Wu, Yang-Zhou; Sun, Yin-Yin; Sheng, Lu; Chen, Shu-Tao; Xiao, Qi-Tao

2014-07-01

In order to study the effect of conservation tillage on soil CO2 and N2O emissions in the following crop-growing season, field experiments were conducted in the winter wheat-growing season. Four treatments were conventional tillage (T), no-tillage with no straw cover (NT), no-tillage with straw cover (NTS), and conventional tillage with straw incorporation (TS), respectively. The CO2 and N2O fluxes were measured using a static chamber-gas chromatograph technique. The results showed that in the following winter wheat-growing season, conservation tillage did not change the seasonal pattern of CO2 and N2O emission fluxes from soil, and had no significant effect on crop biomass. Conservation tillage significantly reduced the accumulative amount of CO2 and N2O. Compared with the T treatment, the accumulative amount of CO2 under TS, NT, and NTS treatments were reduced by 5.95% (P = 0.132), 12.94% (P = 0.007), and 13.91% (P = 0.004), respectively, and the accumulative amount of N2O were significantly reduced by 31.23% (P = 0.000), 61.29% (P = 0.000), and 33.08% (P = 0.000), respectively. Our findings suggest that conservation tillage significantly reduced CO2 and N2O emission from soil in the following winter wheat-growing season.

Photosynthetic properties of C4 plants growing in an African savanna/wetland mosaic

NARCIS (Netherlands)

Mantlana, K.B.; Arneth, A.; Veenendaal, E.M.; Wohland, P.; Wolski, P.; Kolle, O.; Wagner, M.; Lloyd, J.

2008-01-01

Photosynthesis rates and photosynthesis-leaf nutrient relationships were analysed in nine tropical grass and sedge species growing in three different ecosystems: a rain-fed grassland, a seasonal floodplain, and a permanent swamp, located along a hydrological gradient in the Okavango Delta, Botswana.

Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

Energy Technology Data Exchange (ETDEWEB)

Xu, L; Baldocchi, D

2004-05-01

well-accepted view that annual production of grass is linearly correlated to precipitation, the large difference in GPP between the two seasons were not caused by the annual precipitation. Instead, a shorter growing season, due to late start of the rainy season, was mainly responsible for the lower GPP in the second season. Furthermore, relatively higher R{sub eco} during the non-growing season occurred after a late spring rain. Thus, for this Mediterranean grassland, the timing of rain events had more impact than the total amount of precipitation on ecosystem GPP and NEE. This is because its growing season is in the cool and wet season when carbon uptake and respiration are usually limited by low temperature and sometimes frost, not by soil moisture.

Modeling phosphorus capture by plants growing in a multi-species riparian buffer

Science.gov (United States)

The NST 3.0 mechanistic nutrient uptake model was used to explore phosphorus (P) uptake to a depth of 120 cm over a 126-d growing season in simulated buffer communities composed of mixtures of cottonwood (Populus deltoids Bartr.), switchgrass (Panicum virgatum L.), and smooth brome (Bromis inermis L...

Effects of application of corn straw on soil microbial community structure during the maize growing season.

Science.gov (United States)

Lu, Ping; Lin, Yin-Hua; Yang, Zhong-Qi; Xu, Yan-Peng; Tan, Fei; Jia, Xu-Dong; Wang, Miao; Xu, De-Rong; Wang, Xi-Zhuo

2015-01-01

This study investigated the influence of corn straw application on soil microbial communities and the relationship between such communities and soil properties in black soil. The crop used in this study was maize (Zea mays L.). The five treatments consisted of applying a gradient (50, 100, 150, and 200%) of shattered corn straw residue to the soil. Soil samples were taken from May through September during the 2012 maize growing season. The microbial community structure was determined using phospholipid fatty acid (PLFA) analysis. Our results revealed that the application of corn straw influenced the soil properties and increased the soil organic carbon and total nitrogen. Applying corn straw to fields also influenced the variation in soil microbial biomass and community composition, which is consistent with the variations found in soil total nitrogen (TN) and soil respiration (SR). However, the soil carbon-to-nitrogen ratio had no effect on soil microbial communities. The abundance of PLFAs, TN, and SR was higher in C1.5 than those in other treatments, suggesting that the soil properties and soil microbial community composition were affected positively by the application of corn straw to black soil. A Principal Component Analysis indicated that soil microbial communities were different in the straw decomposition processes. Moreover, the soil microbial communities from C1.5 were significantly different from those of CK (p soil and significant variations in the ratio of monounsaturated-to-branched fatty acids with different straw treatments that correlated with SR (p soil properties and soil microbial communities and that these properties affect these communities. The individual PLFA signatures were sensitive indicators that reflected the changes in the soil environment condition. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Seasonally asymmetric enhancement of northern vegetation productivity

Science.gov (United States)

Park, T.; Myneni, R.

2017-12-01

Multiple evidences of widespread greening and increasing terrestrial carbon uptake have been documented. In particular, enhanced gross productivity of northern vegetation has been a critical role leading to observed carbon uptake trend. However, seasonal photosynthetic activity and its contribution to observed annual carbon uptake trend and interannual variability are not well understood. Here, we introduce a multiple-source of datasets including ground, atmospheric and satellite observations, and multiple process-based global vegetation models to understand how seasonal variation of land surface vegetation controls a large-scale carbon exchange. Our analysis clearly shows a seasonally asymmetric enhancement of northern vegetation productivity in growing season during last decades. Particularly, increasing gross productivity in late spring and early summer is obvious and dominant driver explaining observed trend and variability. We observe more asymmetric productivity enhancement in warmer region and this spatially varying asymmetricity in northern vegetation are likely explained by canopy development rate, thermal and light availability. These results imply that continued warming may facilitate amplifying asymmetric vegetation activity and cause these trends to become more pervasive, in turn warming induced regime shift in northern land.

Seasonal Shifts in Diet and Gut Microbiota of the American Bison (Bison bison.

Directory of Open Access Journals (Sweden)

Gaddy T Bergmann

Full Text Available North American bison (Bison bison are becoming increasingly important to both grassland management and commercial ranching. However, a lack of quantitative data on their diet constrains conservation efforts and the ability to predict bison effects on grasslands. In particular, we know little about the seasonality of the bison diet, the degree to which bison supplement their diet with eudicots, and how changes in diet influence gut microbial communities, all of which play important roles in ungulate performance. To address these knowledge gaps, we quantified seasonal patterns in bison diet and gut microbial community composition for a bison herd in Kansas using DNA sequencing-based analyses of both chloroplast and microbial DNA contained in fecal matter. Across the 11 sampling dates that spanned 166 days, we found that diet shifted continuously over the growing season, allowing bison to take advantage of the seasonal availability of high-protein plant species. Bison consumed more woody shrubs in spring and fall than in summer, when forb and grass intake predominated. In examining gut microbiota, the bacterial phylum Tenericutes shifted significantly in relative abundance over the growing season. This work suggests that North American bison can continuously adjust their diet with a high reliance on non-grasses throughout the year. In addition, we find evidence for seasonal patterns in gut community composition that are likely driven by the observed dietary changes.

Relationship between short and long term radon measurements

International Nuclear Information System (INIS)

Martinez, T.; Ramirez, D.; Navarrete, M.; Cabrera, L.; Ramirez, A.; Gonzalez, P.

2000-01-01

In this work the radon group of the Faculty of Chemistry at the National University of Mexico presents the results obtained in the establishment of a relation between the short and long term radon measures made with passive electret detectors E-PERM type LLT and HST. The measures were carried out inside single family dwellings (open house condition) located in the southeast of Mexico City (in Xochimilco) during the four seasons of the year 1997. A correlation was established between the short term measures (five days) and those of a long term for every season as well as an annual average, with an equation that relates them. The objective and advantage of this correlation are that with a short term measure it is possible to predict the annual mean radon concentration, that represents a saving of human and economic resources. (author)

High-Frequency Measurements of Methane Ebullition Over a Growing Season at a Temperate Peatland Site

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Goodrich, Jordan P.; Varner, Ruth K.; Frolking, Steve; Duncan, Bryan N.; Crill, Patrick M.

2011-01-01

Bubbles can contribute a significant fraction of methane emissions fr om wetlands; however the range of reported fractions is very large an d accurate characterization of this pathway has proven difficult. Her e we show that continuous automated flux chambers combined with an in tegrated cavity output spectroscopy (ICOS) instrument allow us to qua ntify both CH4 ebullition rate and magnitude. For a temperate poor f en in 2009, ebullition rate varied on hourly to seasonal time scales. A diel pattern in ebullition was identified with peak release occurr ing between 20:00 and 06:00 local time, though steady fluxes (i.e., t hose with a linear increase in chamber headspace CH4 concentration) d id not exhibit diel variability. Seasonal mean ebullition rates peake d at 843.5 +/- 384.2 events m(exp -2)/d during the summer, with a me an magnitude of 0.19 mg CH4 released in each event.

Wet and Dry Atmospheric Depositions of Inorganic Nitrogen during Plant Growing Season in the Coastal Zone of Yellow River Delta

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Junbao Yu

2014-01-01

Full Text Available The ecological problems caused by dry and wet deposition of atmospheric nitrogen have been widespread concern in the world. In this study, wet and dry atmospheric depositions were monitored in plant growing season in the coastal zone of the Yellow River Delta (YRD using automatic sampling equipment. The results showed that SO42- and Na+ were the predominant anion and cation, respectively, in both wet and dry atmospheric depositions. The total atmospheric nitrogen deposition was ~2264.24 mg m−2, in which dry atmospheric nitrogen deposition was about 32.02%. The highest values of dry and wet atmospheric nitrogen deposition appeared in May and August, respectively. In the studied area, NO3-–N was the main nitrogen form in dry deposition, while the predominant nitrogen in wet atmospheric deposition was NH4+–N with ~56.51% of total wet atmospheric nitrogen deposition. The average monthly attribution rate of atmospheric deposition of NO3-–N and NH4+–N was ~31.38% and ~20.50% for the contents of NO3-–N and NH4+–N in 0–10 cm soil layer, respectively, suggested that the atmospheric nitrogen was one of main sources for soil nitrogen in coastal zone of the YRD.

Wet and dry atmospheric depositions of inorganic nitrogen during plant growing season in the coastal zone of Yellow River Delta.

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Yu, Junbao; Ning, Kai; Li, Yunzhao; Du, Siyao; Han, Guangxuan; Xing, Qinghui; Wu, Huifeng; Wang, Guangmei; Gao, Yongjun

2014-01-01

The ecological problems caused by dry and wet deposition of atmospheric nitrogen have been widespread concern in the world. In this study, wet and dry atmospheric depositions were monitored in plant growing season in the coastal zone of the Yellow River Delta (YRD) using automatic sampling equipment. The results showed that SO4 (2-) and Na(+) were the predominant anion and cation, respectively, in both wet and dry atmospheric depositions. The total atmospheric nitrogen deposition was ~2264.24 mg m(-2), in which dry atmospheric nitrogen deposition was about 32.02%. The highest values of dry and wet atmospheric nitrogen deposition appeared in May and August, respectively. In the studied area, NO3 (-)-N was the main nitrogen form in dry deposition, while the predominant nitrogen in wet atmospheric deposition was NH4 (+)-N with ~56.51% of total wet atmospheric nitrogen deposition. The average monthly attribution rate of atmospheric deposition of NO3 (-)-N and NH4 (+)-N was ~31.38% and ~20.50% for the contents of NO3 (-)-N and NH4 (+)-N in 0-10 cm soil layer, respectively, suggested that the atmospheric nitrogen was one of main sources for soil nitrogen in coastal zone of the YRD.

Enhancing Seasonal Water Outlooks: Needs and Opportunities in the Critical Runoff Season

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Ray, A. J.; Barsugli, J. J.; Yocum, H.; Stokes, M.; Miskus, D.

2017-12-01

The runoff season is a critical period for the management of water supply in the western U.S., where in many places over 70% of the annual runoff occurs in the snowmelt period. Managing not only the volume, but the intra-seasonal timing of the runoff is important for optimizing storage, as well as achieving other goals such as mitigating flood risk, and providing peak flows for riparian habitat management, for example, for endangered species. Western river forecast centers produce volume forecasts for western reservoirs that are key input into many water supply decisions, and also short term river forecasts out to 10 days. The early volume forecasts each year typically begin in December, and are updated throughout the winter and into the runoff season (April-July for many areas, but varies). This presentation will discuss opportunities for enhancing this existing suite of RFC water outlooks, including the needs for and potential use for "intraseasonal" products beyond those provided by the Ensemble Streamflow Prediction system and the volume forecasts. While precipitation outlooks have little skill for many areas and seasons, and may not contribute significantly to the outlook, late winter and spring temperature forecasts have meaningful skill in certain areas and sub-seasonal to seasonal time scales. This current skill in CPC temperature outlooks is an opportunity to translate these products into information about the snowpack and potential runoff timing, even where the skill in precipitation is low. Temperature is important for whether precipitation falls as snow or rain, which is critical for streamflow forecasts, especially in the melt season in snowpack-dependent watersheds. There is a need for better outlooks of the evolution of snowpack, conditions influencing the April-July runoff, and the timing of spring peak or shape of the spring hydrograph. The presentation will also discuss a our work with stakeholders of the River Forecast Centers and the NIDIS

Different Apparent Gas Exchange Coefficients for CO2 and CH4: Comparing a Brown-Water and a Clear-Water Lake in the Boreal Zone during the Whole Growing Season.

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Rantakari, Miitta; Heiskanen, Jouni; Mammarella, Ivan; Tulonen, Tiina; Linnaluoma, Jessica; Kankaala, Paula; Ojala, Anne

2015-10-06

The air-water exchange of carbon dioxide (CO2) and methane (CH4) is a central process during attempts to establish carbon budgets for lakes and landscapes containing lakes. Lake-atmosphere diffusive gas exchange is dependent on the concentration gradient between air and surface water and also on the gas transfer velocity, often described with the gas transfer coefficient k. We used the floating-chamber method in connection with surface water gas concentration measurements to estimate the gas transfer velocity of CO2 (kCO2) and CH4 (kCH4) weekly throughout the entire growing season in two contrasting boreal lakes, a humic oligotrophic lake and a clear-water productive lake, in order to investigate the earlier observed differences between kCO2 and kCH4. We found that the seasonally averaged gas transfer velocity of CH4 was the same for both lakes. When the lakes were sources of CO2, the gas transfer velocity of CO2 was also similar between the two study lakes. The gas transfer velocity of CH4 was constantly higher than that of CO2 in both lakes, a result also found in other studies but for reasons not yet fully understood. We found no differences between the lakes, demonstrating that the difference between kCO2 and kCH4 is not dependent on season or the characteristics of the lake.

Season-to-Season Variations of Physiological Fitness Within a Squad of Professional Male Soccer Players

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Clark, Niall A.; Edwards, Andrew M.; Morton, R. Hugh; Butterly, Ronald J.

2008-01-01

The purpose of this study was to examine season-to-season variations in physiological fitness parameters among a 1st team squad of professional adult male soccer players for the confirmatory purposes of identifying normative responses (immediately prior to pre-season training (PPS), mid-season (MID), and end-of-season (EOS)). Test-retest data were collected from a student population on the primary dependent variables of anaerobic threshold (AT) and maximal aerobic power (VO2 max) to define meaningful measurement change in excess of test-retest technical error between test-to-test performances. Participants from a pool of 42 professional soccer players were tested over a set sequence of tests during the 3-year period: 1) basic anthropometry, 2) countermovement jump (CMJ) tests 3) a combined AT and VO2 max test. Over the 3-year period there were no test-to-test changes in mean VO2 max performance exceeding pre-defined limits of test agreement (mean of eight measures: 61.6 ± 0.6 ml·kg-1·min-1). In contrast, VO2 at AT was significantly higher at the MID test occasion in seasons 2 (+4.8%; p = 0.04, p elite cohort between test-to-test occasions, VO2 max values did not vary significantly over the study which supports previous short-term observations suggesting a general ‘elite’ threshold of 60 ml·kg-1 min. Interestingly, AT significantly varied where VO2 max was stable and these variations also coincided with on- and off-seasons suggesting that AT is a better indication of acute training state than VO2 max. Key points Maximal aerobic power remains fairly stable across inter- and intra-season measurements. Anaerobic threshold appears more sensitive of training state confirming our earlier observations. The professional players tended to attain optimal performances at the mid-season interval over the 3 seasons, presumably prior to the development of accumulative fatigue. PMID:24150149

Interannual and seasonal variability in short-term grazing impact of Euphausia superba in nearshore and offshore waters west of the Antarctic Peninsula

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Ross, R. M.; Quetin, L. B.; Haberman, K. L.

1998-11-01

Our focus in this paper is the interaction between macrozooplanktonic grazers and primary producers, and the interannual and seasonal variability in the Palmer Long-Term Ecological Research (Palmer LTER) study region from Anvers Island to Adelaide Island. Short-term grazing estimates are calculated by integrating (1) theoretical and experimental estimates of ingestion rates in response to the standing stock of phytoplankton, and (2) field measurements of phytoplankton standing stock and grazer biomass. Field data come from three austral summer cruises (January/February of 1993, 1994, and 1995) and one sequence of seasonal cruises (summer, fall and winter 1993). The relative and absolute abundance of the dominant macrozooplankton grazers, Euphausia superba and Salpa thompsoni, varied by at least an order of magnitude on the spatial and temporal scales observed. Mean grazing rates ranged from 0.4 to 9.0 μg chlorophyll m -2 h -1 for the Antarctic krill and salp populations over the three summer cruises. This leads to variability in the flow of carbon from the primary producers through the grazers on the same scales. Temporal and spatial variability in grazing impact and faecal pellet production are high.

Influence of seasonal variation in mood and behavior on cognitive test performance among young adults.

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Merikanto, Ilona; Lahti, Tuuli; Castaneda, Anu E; Tuulio-Henriksson, Annamari; Aalto-Setälä, Terhi; Suvisaari, Jaana; Partonen, Timo

2012-10-01

Seasonal variations in mood and behavior are common among the general population and may have a deteriorating effect on cognitive functions. In this study the effect of seasonal affective disorder (SAD-like symptoms) on cognitive test performance were evaluated in more detail. The data were derived from the study Mental Health in Early Adulthood in Finland. Participants (n = 481) filled in a modified Seasonal Pattern Assessment Questionnaire (SPAQ) and performed cognitive tests in verbal and visual skills, attention and general intelligence. SAD-like symptoms, especially regarding the seasonal variations in weight and appetite, had a significant effect on working memory (Digit Span Backward, P = 0.008) and auditory attention and short-term memory (Digit Span Forward, P = 0.004). The seasonal variations in sleep duration and mood had an effect on auditory attention and short-term memory (Digit Span Forward, P = 0.02 and P = 0.0002, respectively). The seasonal variations in social activity and energy level had no effect. Seasonal changes in mood, appetite and weight have an impairing effect on auditory attention and processing speed. If performance tests are not to repeated in different seasons, attention needs to be given to the most appropriate season in which to test.

Projected changes of thermal growing season over Northern Eurasia in a 1.5 °C and 2 °C warming world

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Zhou, Baiquan; Zhai, Panmao; Chen, Yang; Yu, Rong

2018-03-01

Projected changes of the thermal growing season (TGS) over Northern Eurasia at 1.5 °C and 2 °C global warming levels are investigated using 22 CMIP5 models under both RCP4.5 and RCP8.5 scenarios. The multi-model mean projections indicate Northern Eurasia will experience extended and intensified TGSs in a warmer world. The prolongation of TGSs under 1.5 °C and 2 °C warming is attributed to both earlier onset and later termination, with the latter factor playing a dominating role. Interestingly, earlier onset is of greater importance under RCP4.5 than under RCP8.5 in prolonging TGS as the world warms by an additional 0.5 °C. Under both RCPs, growing degree day sum (GDD) above 5 °C is anticipated to increase by 0 °C-450 °C days and 0 °C-650 °C days over Northern Eurasia at 1.5 °C and 2 °C warming, respectively. However, effective GDD (EGDD) which accumulates optimum temperature for the growth of wheat, exhibits a decline in the south of Central Asia under warmer climates. Therefore, for wheat production over Northern Eurasia, adverse effects incurred by scorching temperatures and resultant inadequacy in water availability may counteract benefits from lengthening and warming TGS. In response to a future 1.5 °C and 2 °C warmer world, proper management and scientifically-tailored adaptation are imperative to optimize local-regional agricultural production.

Forecasting infectious disease emergence subject to seasonal forcing.

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Miller, Paige B; O'Dea, Eamon B; Rohani, Pejman; Drake, John M

2017-09-06

Despite high vaccination coverage, many childhood infections pose a growing threat to human populations. Accurate disease forecasting would be of tremendous value to public health. Forecasting disease emergence using early warning signals (EWS) is possible in non-seasonal models of infectious diseases. Here, we assessed whether EWS also anticipate disease emergence in seasonal models. We simulated the dynamics of an immunizing infectious pathogen approaching the tipping point to disease endemicity. To explore the effect of seasonality on the reliability of early warning statistics, we varied the amplitude of fluctuations around the average transmission. We proposed and analyzed two new early warning signals based on the wavelet spectrum. We measured the reliability of the early warning signals depending on the strength of their trend preceding the tipping point and then calculated the Area Under the Curve (AUC) statistic. Early warning signals were reliable when disease transmission was subject to seasonal forcing. Wavelet-based early warning signals were as reliable as other conventional early warning signals. We found that removing seasonal trends, prior to analysis, did not improve early warning statistics uniformly. Early warning signals anticipate the onset of critical transitions for infectious diseases which are subject to seasonal forcing. Wavelet-based early warning statistics can also be used to forecast infectious disease.

Short term load forecasting technique based on the seasonal exponential adjustment method and the regression model

International Nuclear Information System (INIS)

Wu, Jie; Wang, Jianzhou; Lu, Haiyan; Dong, Yao; Lu, Xiaoxiao

2013-01-01

Highlights: ► The seasonal and trend items of the data series are forecasted separately. ► Seasonal item in the data series is verified by the Kendall τ correlation testing. ► Different regression models are applied to the trend item forecasting. ► We examine the superiority of the combined models by the quartile value comparison. ► Paired-sample T test is utilized to confirm the superiority of the combined models. - Abstract: For an energy-limited economy system, it is crucial to forecast load demand accurately. This paper devotes to 1-week-ahead daily load forecasting approach in which load demand series are predicted by employing the information of days before being similar to that of the forecast day. As well as in many nonlinear systems, seasonal item and trend item are coexisting in load demand datasets. In this paper, the existing of the seasonal item in the load demand data series is firstly verified according to the Kendall τ correlation testing method. Then in the belief of the separate forecasting to the seasonal item and the trend item would improve the forecasting accuracy, hybrid models by combining seasonal exponential adjustment method (SEAM) with the regression methods are proposed in this paper, where SEAM and the regression models are employed to seasonal and trend items forecasting respectively. Comparisons of the quartile values as well as the mean absolute percentage error values demonstrate this forecasting technique can significantly improve the accuracy though models applied to the trend item forecasting are eleven different ones. This superior performance of this separate forecasting technique is further confirmed by the paired-sample T tests

Do farmers rapidly adapt to past growing conditions by sowing different proportions of early and late maturing cereals and cultivars?

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Pirjo Peltonen-Sainio

2013-10-01

Full Text Available In the short growing season of the northernmost European growing conditions, farmers are increasingly interested in expanding cultivation of later maturing crops at the expense of early maturing ones with lower yields. In this study we aimed to assess how the switching between spring cereals that differ in earliness was associated with different external factors. This was tested using unique datasets for regional cropping areas and cultivar use for the last 15 years. Early maturing barley was favored at the expense of later maturing wheat when a high number of days to crop maturity was required in the preceding year. In contrast, farmers reduced the barley area when a high number of cumulated degree days was required for a crop to mature in the previous year. A shift was recorded from early to late maturing cultivars. This study indicated that despite limited opportunities for farmers to alter land use, they readily responded to past conditions and used the knowledge gained for decision-making to reduce risk. This is a valuable operative model for studying adaptation to opportunities and constraints induced by climate change.

Growing season changes in Fennoscandia and Kola peninsula during the period 1982 to 1999 - Implications for reindeer husbandry (In Norwegian with Summary in English

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Hans Tømmervik

2005-04-01

the length of the growing season in Fennoscandia and Kola Peninsula during the last two decades. We used phenological observation data for birch (Betula pubescens, and birch give a significant contribution to the reflectance from the ground in order to analyze the satellite data. A method using an individual threshold NDVI value for defining the onset of the growing season applied to each pixel for each year was chosen, and a high correlation was found between the NDVI data and in-situ phenological data on onset of leafing of birch. Determining the end of growing season based on a threshold NDVI value shows a lower correlation with surface data, but the timing by the set threshold is observed to measure somewhere in-between the onset of yellowing and all leaves fallen. In general, the results show a pattern according to vegetation zones and the altitude gradient, and partly according to vegetation sections. There are high regional differences in trends in the onset of spring. In the southern part of Fennoscandia, and on the oceanic west coast of Norway, the spring starts considerably earlier in the late nineties compared to the early eighties. The spring is stable or delayed in the northern boreal zone, which occupies large areas of northern Fennoscandia and Kola peninsula, and the same trend is also found in the alpine areas which occupies parts of both southern and northern Norway. The strongest delay occurred in the most continental section of the northern boreal zone. In the entire boreo-nemoral and nemoral zone, which occupy most of the southern part of Fennoscandia, the trend is opposite. In these areas the spring starts considerably earlier, in some parts several weeks. In the most oceanic section, the coastline of Western Norway, the spring also starts earlier. This earlier trend fits with the pattern from western and central Europe, and is likely to be related to increased spring temperature. At the same time the autumn is delayed in the whole area except in

Successional dynamics in the seasonally forced diamond food web.

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Klausmeier, Christopher A; Litchman, Elena

2012-07-01

Plankton seasonal succession is a classic example of nonequilibrium community dynamics. Despite the fact that it has been well studied empirically, it lacks a general quantitative theory. Here we investigate a food web model that includes a resource, two phytoplankton, and a shared grazer-the diamond food web-in a seasonal environment. The model produces a number of successional trajectories that have been widely discussed in the context of the verbal Plankton Ecology Group model of succession, such as a spring bloom of a good competitor followed by a grazer-induced clear-water phase, setting the stage for the late-season dominance of a grazer-resistant species. It also predicts a novel, counterintuitive trajectory where the grazer-resistant species has both early- and late-season blooms. The model often generates regular annual cycles but sometimes produces multiyear cycles or chaos, even with identical forcing each year. Parameterizing the model, we show how the successional trajectory depends on nutrient supply and the length of the growing season, two key parameters that vary among water bodies. This model extends nonequilibrium theory to food webs and is a first step toward a quantitative theory of plankton seasonal succession.

The stochastic seasonal behavior of energy commodity convenience yields

International Nuclear Information System (INIS)

Mirantes, Andrés García; Población, Javier; Serna, Gregorio

2013-01-01

This paper contributes to the commodity pricing literature by consistently modeling the convenience yield with its empirically observed properties. Specifically, in this paper, we show how a four-factor model for the stochastic behavior of commodity prices, with two long- and short-term factors and two additional seasonal factors, may accommodate some of the most important empirically observed characteristics of commodity convenience yields, such as the mean reversion and stochastic seasonality. Based on this evidence, a theoretical model is presented and estimated to characterize the commodity convenience yield dynamics that are consistent with previous findings. We also show that commodity price seasonality is better estimated through convenience yields than through futures prices. - Highlights: • Energy commodity convenience yields exhibit mean reversion and stochastic seasonality. • We present a model for convenience yields accounting for their observed characteristics. • Commodity price seasonality is better estimated through convenience yields

Effect of nitrogen on the seasonal course of growth and maintenance respiration in stems of Norway spruce trees.

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Stockfors, Jan; Linder, Sune

1998-03-01

To determine effects of stem nitrogen concentration ([N]) on the seasonal course of respiration, rates of stem respiration of ten control and ten irrigated-fertilized (IL), 30-year-old Norway spruce trees (Picea abies (L.) Karst.), growing in northern Sweden, were measured on seven occasions from June 1993 to April 1994. To explore sources of seasonal variation and mechanisms of fertilization effects on respiration, we separated total respiration into growth and maintenance respiration for both xylem and phloem bark. Stem respiration increased in response to the IL treatment and was positively correlated with growth rate, volume of living cells and stem nitrogen content. However, no significant effect of IL treatment or [N] in the living cells was found for respiration per unit volume of live cells. Total stem respiration during the growing season (June to September) was estimated to be 16.7 and 29.7 mol CO(2) m(-2) for control and IL-treated trees, respectively. Respiration during the growing season accounted for approximately 64% of total annual respiration. Depending on the method, estimated growth respiration varied between 40 and 60% of total respiration during the growing season. Between 75 and 80% of the live cell volume in the stems was in the phloem, and phloem maintenance accounted for about 70% of maintenance respiration. Because most of the living cells were found in the phloem, and the living xylem cells were concentrated in the outer growth rings, we concluded that the best base for expressing rates of stem growth and maintenance respiration in young Norway spruce trees is stem surface area.

Modeling Aspect Controlled Formation of Seasonally Frozen Ground on Montane Hillslopes: a Case Study from Gordon Gulch, Colorado

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Rush, M.; Rajaram, H.; Anderson, R. S.; Anderson, S. P.

2017-12-01

The Intergovernmental Panel on Climate Change (2013) warns that high-elevation ecosystems are extremely vulnerable to climate change due to short growing seasons, thin soils, sparse vegetation, melting glaciers, and thawing permafrost. Many permafrost-free regions experience seasonally frozen ground. The spatial distribution of frozen soil exerts a strong control on subsurface flow and transport processes by reducing soil permeability and impeding infiltration. Accordingly, evolution of the extent and duration of frozen ground may alter streamflow seasonality, groundwater flow paths, and subsurface storage, presenting a need for coupled thermal-hydrologic models to project hydrologic responses to climate warming in high-elevation regions. To be useful as predictive tools, such models should incorporate the heterogeneity of solar insolation, vegetation, and snowpack dynamics. We present a coupled thermal-hydrologic modeling study against the backdrop of field observations from Gordon Gulch, a seasonally snow-covered montane catchment in the Colorado Front Range in the Boulder Creek Critical Zone Observatory. The field site features two instrumented hillslopes with opposing aspects: the snowpack on the north-facing slope persists throughout much of the winter season, while the snowpack on the south-facing slope is highly ephemeral. We implemented a surface energy balance and snowpack accumulation and ablation model that is coupled to the subsurface flow and transport code PFLOTRAN-ICE to predict the hydrologic consequences of aspect-controlled frozen soil formation during water years 2013-2016. Preliminary model results demonstrate the occurrence of seasonally-frozen ground on the north-facing slope that directs snowmelt to the stream by way of shallow subsurface flow paths. The absence of persistently frozen ground on the south-facing slope allows deeper infiltration of snowmelt recharge. The differences in subsurface flow paths also suggest strong aspect

HARVEST LABOR QUALITY AND PRODUCTIVITY:CASE STUDY OF CHERRY GROWING IN CHILE

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ROBERTO JARA-ROJAS

2015-06-01

Full Text Available In Chile, the cherry tree has been one of the fastest growing and most profitable crops in the last ten years. However, increasing production costs, the scarcity of hired labor, and unfavorable exchange rates have reduced the productivity and competitiveness of the Chilean fruit sector. The aim of this article is to evaluate the harvest labor quality in cherry growing in Chile through the use of productivity indicators. A harvest labor evaluation system (HLES was designed and four indicators were measured: Average Weight of Harvested Box, Average Daily Production per Worker, Percent of Export Fruit, and Percent of Fruit Discarded. Significant differences werefound between the 2010/11 season (with the HLES implementation and the previous seasons without HLES. The average worker yield, average weight of a filled box, and fruit quality improved, while the amount of discarded fruit decreased. Hired labor management in agriculture is crucial for improving the productivity of the fresh fruit export producers. The use of HLES and the adoption of new technologies could help to solve the competitiveness problem in the Chilean fruit sector.

The potential influence of short-term environmental variability on the composition of testate amoeba communities in Sphagnum peatlands.

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Sullivan, Maura E; Booth, Robert K

2011-07-01

Testate amoebae are a group of moisture-sensitive, shell-producing protozoa that have been widely used as indicators of changes in mean water-table depth within oligotrophic peatlands. However, short-term environmental variability (i.e., sub-annual) also probably influences community composition. The objective of this study was to assess the potential influence of short-term environmental variability on the composition of testate amoeba communities in Sphagnum-dominated peatlands. Testate amoebae and environmental conditions, including hourly measurements of relative humidity within the upper centimeter of the peatland surface, were examined throughout the 2008 growing season at 72 microsites within 11 peatlands of Pennsylvania and Wisconsin, USA. Relationships among testate amoeba communities, vegetation, depth to water table, pH, and an index of short-term environmental variability (EVI), were examined using nonmetric multidimensional scaling and correlation analysis. Results suggest that EVI influences testate amoeba communities, with some taxa more abundant under highly variable conditions (e.g., Arcella discoides, Difflugia pulex, and Hyalosphenia subflava) and others more abundant when environmental conditions at the peatland surface were relatively stable (e.g., Archerella flavum and Bullinularia indica). The magnitude of environmental variability experienced at the peatland surface appears to be primarily controlled by vegetation composition and density. In particular, sites with dense Sphagnum cover had lower EVI values than sites with loose-growing Sphagnum or vegetation dominated by vascular plants and/or non-Sphagnum bryophytes. Our results suggest that more environmental information may be inferred from testate amoebae than previously recognized. Knowledge of relationships between testate amoebae and short-term environmental variability should lead to more detailed and refined environmental inferences.

An integrated, probabilistic model for improved seasonal forecasting of agricultural crop yield under environmental uncertainty

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Nathaniel K. Newlands

2014-06-01

Full Text Available We present a novel forecasting method for generating agricultural crop yield forecasts at the seasonal and regional-scale, integrating agroclimate variables and remotely-sensed indices. The method devises a multivariate statistical model to compute bias and uncertainty in forecasted yield at the Census of Agricultural Region (CAR scale across the Canadian Prairies. The method uses robust variable-selection to select the best predictors within spatial subregions. Markov-Chain Monte Carlo (MCMC simulation and random forest-tree machine learning techniques are then integrated to generate sequential forecasts through the growing season. Cross-validation of the model was performed by hindcasting/backcasting it and comparing its forecasts against available historical data (1987-2011 for spring wheat (Triticum aestivum L.. The model was also validated for the 2012 growing season by comparing its forecast skill at the CAR, provincial and Canadian Prairie region scales against available statistical survey data. Mean percent departures between wheat yield forecasted were under-estimated by 1-4 % in mid-season and over-estimated by 1 % at the end of the growing season. This integrated methodology offers a consistent, generalizable approach for sequentially forecasting crop yield at the regional-scale. It provides a statistically robust, yet flexible way to concurrently adjust to data-rich and data-sparse situations, adaptively select different predictors of yield to changing levels of environmental uncertainty, and to update forecasts sequentially so as to incorporate new data as it becomes available. This integrated method also provides additional statistical support for assessing the accuracy and reliability of model-based crop yield forecasts in time and space.

Growing hairs in shorn cattle

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Cecília José Veríssimo

2013-12-01

10, hair decreased from average 21.26 ± 5.72 mm to 4.50 ± 0.83 mm. On the sheared side a hair growth of 26 mm was observed during the first two weeks, increasing to 40 mm for the next two weeks and at the end of 28 days there was still a significant difference (Z= -3.195; P= 0.001 for the non sheared hair (19.42 ± 7.33 mm and sheared hair (11.15 ± 3.23 mm. Such procedure was done by the beginning of August, still winter time. Using the blade size 30, sheared hair had an average of 4.76 ± 1.1 mm. A 24 mm hair growth was observed for the first two weeks and 20 mm for the next two weeks, decreasing its growth speed to 9 mm and after 57 days no significant difference was observed between sheared side (11.47 ± 5.61 mm and non sheared side (14.78 ± 8.06 mm, Z= -1.915; P= 0.055. Second cut was performed by  the beginning of October, spring time, period where there is a change of hair in European cattle  from winter season (thin and long hair to summer season (thick and short hair, starting on spring time. In this work we could observe the fast growing of hair when cut was done in winter time and the closer to the skin the better the benefits to the animals, as heat tolerance and fewer tick infestations. If shearing is done in spring time, it must be every 45-50 days.

Seasonal variation of strongylosis in working donkeys of Ethiopia: a cross-sectional and longitudinal studies.

Science.gov (United States)

Dibaba, Motuma Debelo; Getachew, A M; Assefa, Zerihun; Fanta, Alemayehu; Etana, Manyahilishal; Firew, Seyoum; Goshu, Lemessa; Burden, F

2017-07-01

Helminths are one of the major health problems of working donkeys, often with heavy worm burden and contributing to their early demise and/or reduction in their work output. Cross-sectional and longitudinal studies were conducted to investigate the current infection prevalence and level of strongyles infection donkeys would acquire through different seasons in the mid-lowland agro-ecological zones of Ethiopia. For this purpose, faecal samples from 206 (cross-sectional study) and 102 (longitudinal study) randomly selected donkeys were directly collected from the rectum and analysed. For the longitudinal study, the 102 donkeys dewormed at the end of main rainy season, beginning of October, were monitored for the level of strongyle infection they would acquire during subsequent dry and short rainy seasons. The cross-sectional study of 206 donkey has revealed an overall infection prevalence of 89.3% (95% confidence interval (CI) = 84.4, 92.9). Donkeys in the lowland zone showed a significantly higher strongyle infection prevalence (P = 0.0126) and mean eggs per gramme of faces (EPG) (P = 0.001; 2775 EPG) compared to donkeys in the midland zone (980.8 EPG). Age, sex and body condition did not have any significant effect on either the infection prevalence or level of infection (P > 0.05). The longitudinal study has shown a significantly lower strongyle infection prevalence (P = 0.003) and level of infection donkeys acquired (P = 0.001) in the subsequent dry and short rainy seasons compared to the main rainy season following October deworming. However, these values were not significantly different between the two agro-ecological zones (P > 0.05). This study clearly showed that parasitic infections are primarily acquired during the main rainy season when pasture/herbage coverage is relatively better, and the environment is conducive for parasites survival and development. On the other hand, the finding of majority of donkeys shedding low or no eggs during the

Growth and yield of mixed polyclonal stands of Populus in short-rotation coppice

Energy Technology Data Exchange (ETDEWEB)

Benbrahim, Mohammed; Gavaland, Andre [INRA centre de Toulouse (France). Unite Agroforesterie et foret Paysanne; Gauvin, Jean [INRA centre d' Orleans (France). Unite d' Amelioration des arbres forestiers

2000-07-01

Eight clones of poplar were used to compare the growth and productivity of monoclonal and polyclonal mixed plantations in short-rotation coppice. At the end of the eight growing season, the diameter at breast height (DBH) and height of trees were measured and dry weight and yield were estimated. Polyclonal mixtures did not affect mortality. Few differences in growth were observed between clones in monoclonal plots. Polyclonal mixture slightly affected the growth and tree size of the clones compared with monoclonal plots. No increase in stand heterogeneity in relation to clone deployment was observed. A neighbourhood index was calculated for each tree and was significantly affected by polyclonal mixture. However, the relationship between the neighbourhood index and the DBH indicated that this effect did not cause a great change in DBH. Consequently, dry weight and yield productivity were not affected by clone deployment.

Seasonal isotope hydrology of a coffee agroforestry watershed in Costa Rica

Science.gov (United States)

Welsh Unwala, K.; Boll, J.; Roupsard, O.

2014-12-01

Improved information of seasonal variations in watershed hydrology in the tropics can strengthen models and understanding of hydrology of these areas. Seasonality in the tropics produces rainy seasons versus dry seasons, leading to different hydrologic and water quality processes throughout the year. We questioned whether stable isotopes in water can be used to trace the seasonality in this region, despite experiencing a "drier" season, such as in a Tropical Humid location. This study examines the fluctuations of stable isotope compositions (δ18O and δD) in water balance components in a small (deep groundwater system contributes significantly to baseflow, although a shallow, spring-driven system also contributes to stream water within the watershed. During storm events, precipitation contributes to stormflow in the short-term, confirming the role of superficial runoff. These results indicate that isotopes are helpful to partition the water balance even in a Tropical Humid situation where the rainfall seasonality is weak.

Short Linear Sequence Motif LxxPTPh Targets Diverse Proteins to Growing Microtubule Ends

NARCIS (Netherlands)

Kumar, Anil; Manatschal, Cristina; Rai, Ankit; Grigoriev, Ilya; Degen, Miriam Steiner; Jaussi, Rolf; Kretzschmar, Ines; Prota, Andrea E; Volkmer, Rudolf; Kammerer, Richard A.; Akhmanova, Anna; Steinmetz, Michel O.

2017-01-01

Microtubule plus-end tracking proteins (+TIPs) are involved in virtually all microtubule-based processes. End-binding (EB) proteins are considered master regulators of +TIP interaction networks, since they autonomously track growing microtubule ends and recruit a plethora of proteins to this

Decoupling Seasonal Changes in Water Content and Dry Matter to Predict Live Conifer Foliar Moisture Content.

OpenAIRE

Jolly, W. M.; Hadlow, A. M.; Huguet, K.

2014-01-01

Live foliar moisture content (LFMC) significantly influences wildland fire behaviour. However, characterising variations in LFMC is difficult because both foliar mass and dry mass can change throughout the season. Here we quantify the seasonal changes in both plant water status and dry matter partitioning. We collected new and old foliar samples fromPinus contorta for two growing seasons and quantified their LFMC, relative water content (RWC) and dry matter chemistry. LFMC quantifies the amou...

Capital versus income breeding in a seasonal environment

DEFF Research Database (Denmark)

Sainmont, Julie; Andersen, Ken Haste; Varpe, Oystein

2014-01-01

and thereby achieve a high annual growth rate, outcompeting capital breeders in long feeding seasons. Therefore, we expect to find a dominance of small income breeders in temperate waters, while large capital breeders should dominate high latitudes where the spring is short and intense. This pattern...

Impact of seasonal forcing on reactive ecological systems.

Science.gov (United States)

Vesipa, Riccardo; Ridolfi, Luca

2017-04-21

Our focus is on the short-term dynamics of reactive ecological systems which are stable in the long term. In these systems, perturbations can exhibit significant transient amplifications before asymptotically decaying. This peculiar behavior has attracted increasing attention. However, reactive systems have so far been investigated assuming that external environmental characteristics remain constant, although environmental conditions (e.g., temperature, moisture, water availability, etc.) can undergo substantial changes due to seasonal cycles. In order to fill this gap, we propose applying the adjoint non-modal analysis to study the impact of seasonal variations of environmental conditions on reactive systems. This tool allows the transient dynamics of a perturbation affecting non-autonomous ecological systems to be described. To show the potential of this approach, a seasonally forced prey-predator model with a Holling II type functional response is studied as an exemplifying case. We demonstrate that seasonalities can greatly affect the transient dynamics of the system. Copyright © 2017 Elsevier Ltd. All rights reserved.

Seasonality and Management Affect Land Surface Temperature Differences Between Loblolly Pine and Switchgrass Ecosystems in Central Virginia

Science.gov (United States)

Ahlswede, B.; Thomas, R. Q.; O'Halloran, T. L.; Rady, J.; LeMoine, J.

2017-12-01

Changes in land-use and land management can have biogeochemical and biophysical effects on local and global climate. While managed ecosystems provide known food and fiber benefits, their influence on climate is less well quantified. In the southeastern United States, there are numerous types of intensely managed ecosystems but pine plantations and switchgrass fields represent two biogeochemical and biophysical extremes; a tall, low albedo forest with trees harvested after multiple decades vs. a short, higher albedo C4 grass field that is harvested annually. Despite the wide spread use of these ecosystems for timber and bioenergy, a quantitative, empirical evaluation of the net influence of these ecosystems on climate is lacking because it requires measuring both the greenhouse gas and energy balance of the ecosystems while controlling for the background weather and soil environment. To address this need, we established a pair of eddy flux towers in these ecosystems that are co-located (1.5 km apart) in Central Virginia and measured the radiative energy, non-radiative energy and carbon fluxes, along with associated biometeorology variables; the paired site has run since April 2016. During the first 1.5 years (two growing seasons), we found strong seasonality in the difference in surface temperature between the two ecosystems. In the growing seasons, both sites had similar surface temperature despite higher net radiation in pine. Following harvest of the switchgrass in September, the switchgrass temperatures increased relative to pine. In the winter, the pine ecosystem was warmer. We evaluate the drivers of these intra-annual dynamics and compare the climate influence of these biophysical differences to the differences in carbon fluxes between the sites using a suite of established climate regulation services metrics. Overall, our results show tradeoffs exist between the biogeochemical and biophysical climate services in managed ecosystems in the southeastern United

The relationship of lightning activity and short-duration rainfall events during warm seasons over the Beijing metropolitan region

Science.gov (United States)

Wu, Fan; Cui, Xiaopeng; Zhang, Da-Lin; Qiao, Lin

2017-10-01

The relationship between lightning activity and rainfall associated with 2925 short-duration rainfall (SDR) events over the Beijing metropolitan region (BMR) is examined during the warm seasons of 2006-2007, using the cloud-to-ground (CG) and intracloud (IC) lightning data from Surveillance et Alerte Foudre par Interférometrie Radioélectrique (SAFIR)-3000 and 5-min rainfall data from automatic weather stations (AWSs). An optimal radius of 10 km around selected AWSs is used to determine the lightning-rainfall relationship. The lightning-rainfall correlations vary significantly, depending upon the intensity of SDR events. That is, correlation coefficient (R 0.7) for the short-duration heavy rainfall (SDHR, i.e., ≥ 20 mm h- 1) events is found higher than that (R 0.4) for the weak SDR (i.e., 5-10 mm h- 1) events, and lower percentage of the SDHR events (< 10%) than the weak SDR events (40-50%) are observed with few flashes. Significant time-lagged correlations between lightning and rainfall are also found. About 80% of the SDR events could reach their highest correlation coefficients when the associated lightning flashes shift at time lags of < 25 min before and after rainfall begins. Those events with lightning preceding rainfall account for 50-60% of the total SDR events. Better lightning-rainfall correlations can be attained when time lags are incorporated, with the use of total (CG and IC) lightning data. These results appear to have important implications for improving the nowcast of SDHR events.

Seasonal variability of microbial biomass phosphorus in urban soils.

Science.gov (United States)

Halecki, W; Gąsiorek, M

2015-01-01

Urban soils have been formed through human activities. Seasonal evaluation with time-control procedure are essential for plant, and activity of microorganisms. Therefore, these processes are crucial in the urban area due to geochemical changes in the past years. The purpose of this study was to investigate the changes of content of microbial biomass phosphorus (P) in the top layer of soils throughout the season. In this research, the concentration of microbial biomass P ranged from 0.01 to 6.29 mg·kg(-1). We used single-factor repeated-measure analysis of variance to test the effect of season on microbial biomass P content of selected urban soils. We found no statistically significant differences between the concentration of microbial biomass P in the investigated urban and sub-urban soils during the growing season. This analysis explicitly recognised that environmental urban conditions are steady. Specifically, we have studied how vegetation seasonality and ability of microbial biomass P are useful for detecting quality deviations, which affect the equilibrium of urban soil. In conclusion, seasonal variability of the stringency of assurance across the different compounds of soil reveals, as expected, the stable condition of the urban soils. Seasonal responses in microbial biomass P under urban soil use should establish a framework as a reference to the activity of the microorganisms. Copyright © 2014 Elsevier B.V. All rights reserved.

Grow your own REE deposits: Novel observations from the soils of Southern Portugal

Science.gov (United States)

Hardy, Liam; Smith, Martin; Boyce, Adrian; McDonald, Alison; Heller, Shaun; Bamberger, Axel; Blum, Astrid; Hood, Leo

2017-04-01

Industrialised eucalyptus farming in Serra de Monchique has been well documented for its regional impacts on water flow, for its destructive centralisation of local economics (Jenkins, 1979) and for its derogatory impacts on local ecology (Brito, 1999) (Matias & Lamberts, 2011), it is another story of cash cropping for short term gain in an area of sensitive environmental balance which had previously been suitably subsistence farmed for some 700 years with no outside influence until the early 1950s (Jenkins, 1979). The farming has irreversibly changed local customs, soil and water systems, but formed new and intricate relationships between the troposol, oxisol and latosol formations and plants which have not previously been studied in this region in terms of soil geochemistry. During research in the region (as part of the SoS Rare/NERC-UK program) into metal and clay interactions in the troposol formations of Monchique, it was noted that rare earth elements (REEs) and other soluble ions were being mobilised in the upper half of the profiles by some seasonal cycle other than the natural meteoric input/leaching expected during classical lateritisation (Tardy, 1997). It was observed that some 40% of Fe and some 30% of Y were leaving the profile during wet season and concentrating at specific depths during dry seasons to a grade of some 160ppm Y and were thus, potentially viable as an economic resource of Heavy REEs. This PICO presentation discusses the proposed anthropogenic/biogenic mechanism for this concentration and how you too could potentially grow an economically viable REE enriched garden. References: Brito, J. G. (1999). Management strategies for conservation of the lizard Lacerta schreiberi in Portugal. Biological conservation, 311-319. Jenkins, R. (1979). The Road to Alto: An account of peasants, capitalists and their soil in the mountains of Southern Portugal. London: Pluto, ISBN: 0861040767. Matias, M., & Lamberts, P. (2011, May 26). Parliamentary

Ecophysiological response to seasonal variations in water availability in the arborescent, endemic plant Vellozia gigantea.

Science.gov (United States)

Morales, Melanie; Garcia, Queila S; Munné-Bosch, Sergi

2015-03-01

The physiological response of plants growing in their natural habitat is strongly determined by seasonal variations in environmental conditions and the interaction of abiotic and biotic stresses. Here, leaf water and nutrient contents, changes in cellular redox state and endogenous levels of stress-related phytohormones (abscisic acid (ABA), salicylic acid and jasmonates) were examined during the rainy and dry season in Vellozia gigantea, an endemic species growing at high elevations in the rupestrian fields of the Espinhaço Range in Brazil. Enhanced stomatal closure and increased ABA levels during the dry season were associated with an efficient control of leaf water content. Moreover, reductions in 12-oxo-phytodienoic acid (OPDA) levels during the dry season were observed, while levels of other jasmonates, such as jasmonic acid and jasmonoyl-isoleucine, were not affected. Changes in ABA and OPDA levels correlated with endogenous concentrations of iron and silicon, hydrogen peroxide, and vitamin E, thus indicating complex interactions between water and nutrient contents, changes in cellular redox state and endogenous hormone concentrations. Results also suggested crosstalk between activation of mechanisms for drought stress tolerance (as mediated by ABA) and biotic stress resistance (mediated by jasmonates), in which vitamin E levels may serve as a control point. It is concluded that, aside from a tight ABA-associated regulation of stomatal closure during the dry season, crosstalk between activation of abiotic and biotic defences, and nutrient accumulation in leaves may be important modulators of plant stress responses in plants growing in their natural habitat. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Cold season emissions dominate the Arctic tundra methane budget

Science.gov (United States)

Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C.; Miller, Charles E.; Dinardo, Steven J.; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y.-W.; Henderson, John M.; Murphy, Patrick C.; Goodrich, Jordan P.; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D.; Kimball, John S.; Lipson, David A.; Oechel, Walter C.

2016-01-01

Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y-1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

Seasonal cultivated and fallow cropland mapping using MODIS-based automated cropland classification algorithm

Science.gov (United States)

Wu, Zhuoting; Thenkabail, Prasad S.; Mueller, Rick; Zakzeski, Audra; Melton, Forrest; Johnson, Lee; Rosevelt, Carolyn; Dwyer, John; Jones, Jeanine; Verdin, James P.

2014-01-01

Increasing drought occurrences and growing populations demand accurate, routine, and consistent cultivated and fallow cropland products to enable water and food security analysis. The overarching goal of this research was to develop and test automated cropland classification algorithm (ACCA) that provide accurate, consistent, and repeatable information on seasonal cultivated as well as seasonal fallow cropland extents and areas based on the Moderate Resolution Imaging Spectroradiometer remote sensing data. Seasonal ACCA development process involves writing series of iterative decision tree codes to separate cultivated and fallow croplands from noncroplands, aiming to accurately mirror reliable reference data sources. A pixel-by-pixel accuracy assessment when compared with the U.S. Department of Agriculture (USDA) cropland data showed, on average, a producer's accuracy of 93% and a user's accuracy of 85% across all months. Further, ACCA-derived cropland maps agreed well with the USDA Farm Service Agency crop acreage-reported data for both cultivated and fallow croplands with R-square values over 0.7 and field surveys with an accuracy of ≥95% for cultivated croplands and ≥76% for fallow croplands. Our results demonstrated the ability of ACCA to generate cropland products, such as cultivated and fallow cropland extents and areas, accurately, automatically, and repeatedly throughout the growing season.

Seasonal cultivated and fallow cropland mapping using MODIS-based automated cropland classification algorithm

Science.gov (United States)

Wu, Zhuoting; Thenkabail, Prasad S.; Mueller, Rick; Zakzeski, Audra; Melton, Forrest; Johnson, Lee; Rosevelt, Carolyn; Dwyer, John; Jones, Jeanine; Verdin, James P.

2014-01-01

Increasing drought occurrences and growing populations demand accurate, routine, and consistent cultivated and fallow cropland products to enable water and food security analysis. The overarching goal of this research was to develop and test automated cropland classification algorithm (ACCA) that provide accurate, consistent, and repeatable information on seasonal cultivated as well as seasonal fallow cropland extents and areas based on the Moderate Resolution Imaging Spectroradiometer remote sensing data. Seasonal ACCA development process involves writing series of iterative decision tree codes to separate cultivated and fallow croplands from noncroplands, aiming to accurately mirror reliable reference data sources. A pixel-by-pixel accuracy assessment when compared with the U.S. Department of Agriculture (USDA) cropland data showed, on average, a producer’s accuracy of 93% and a user’s accuracy of 85% across all months. Further, ACCA-derived cropland maps agreed well with the USDA Farm Service Agency crop acreage-reported data for both cultivated and fallow croplands with R-square values over 0.7 and field surveys with an accuracy of ≥95% for cultivated croplands and ≥76% for fallow croplands. Our results demonstrated the ability of ACCA to generate cropland products, such as cultivated and fallow cropland extents and areas, accurately, automatically, and repeatedly throughout the growing season.

Establishing native warm season grasses on Eastern Kentucky strip mines

Energy Technology Data Exchange (ETDEWEB)

Barnes, T.G.; Larkin, J.L.; Arnett, M.B. [Univ. of Kentucky, Lexington, KY (United States). Dept. of Forestry

1998-12-31

The authors evaluated various methods of establishing native warm season grasses on two reclaimed Eastern Kentucky mines from 1994--1997. Most current reclamation practices incorporate the use of tall fescue (Festuca arundinacea) and other cool-season grasses/legumes that provide little wildlife habitats. The use of native warm season grasses will likely improve wildlife habitat on reclaimed strip mines. Objectives of this study were to compare the feasibility of establishing these grasses during fall, winter, or spring using a native rangeland seeder or hydroseeding; a fertilizer application at planting; or cold-moist stratification prior to hydroseeding. Vegetative cover, bare ground, species richness, and biomass samples were collected at the end of each growing season. Native warm season grass plantings had higher plant species richness compared to cool-season reclamation mixtures. There was no difference in establishment of native warm season grasses as a result of fertilization or seeding technique. Winter native warm season grass plantings were failures and cold-moist stratification did not increase plant establishment during any season. As a result of a drought during 1997, both cool-season and warm season plantings were failures. Cool-season reclamation mixtures had significantly more vegetative cover and biomass compared to native warm season grass mixtures and the native warm season grass plantings did not meet vegetative cover requirements for bond release. Forbs and legumes that established well included pale purple coneflower (Echinacea pallida), lance-leaf coreopsis (Coreopsis lanceolata), round-headed lespedeza (Lespedeza capitata), partridge pea (Cassia fasiculata), black-eyed susan (Rudbeckia hirta), butterfly milkweed (Asclepias tuberosa), and bergamot (Monarda fistulosa). Results from two demonstration plots next to research plots indicate it is possible to establish native warm season grasses on Eastern Kentucky strip mines for wildlife habitat.

Establishing native warm season grasses on Eastern Kentucky strip mines

International Nuclear Information System (INIS)

Barnes, T.G.; Larkin, J.L.; Arnett, M.B.

1998-01-01

The authors evaluated various methods of establishing native warm season grasses on two reclaimed Eastern Kentucky mines from 1994--1997. Most current reclamation practices incorporate the use of tall fescue (Festuca arundinacea) and other cool-season grasses/legumes that provide little wildlife habitats. The use of native warm season grasses will likely improve wildlife habitat on reclaimed strip mines. Objectives of this study were to compare the feasibility of establishing these grasses during fall, winter, or spring using a native rangeland seeder or hydroseeding; a fertilizer application at planting; or cold-moist stratification prior to hydroseeding. Vegetative cover, bare ground, species richness, and biomass samples were collected at the end of each growing season. Native warm season grass plantings had higher plant species richness compared to cool-season reclamation mixtures. There was no difference in establishment of native warm season grasses as a result of fertilization or seeding technique. Winter native warm season grass plantings were failures and cold-moist stratification did not increase plant establishment during any season. As a result of a drought during 1997, both cool-season and warm season plantings were failures. Cool-season reclamation mixtures had significantly more vegetative cover and biomass compared to native warm season grass mixtures and the native warm season grass plantings did not meet vegetative cover requirements for bond release. Forbs and legumes that established well included pale purple coneflower (Echinacea pallida), lance-leaf coreopsis (Coreopsis lanceolata), round-headed lespedeza (Lespedeza capitata), partridge pea (Cassia fasiculata), black-eyed susan (Rudbeckia hirta), butterfly milkweed (Asclepias tuberosa), and bergamot (Monarda fistulosa). Results from two demonstration plots next to research plots indicate it is possible to establish native warm season grasses on Eastern Kentucky strip mines for wildlife habitat

Cambial activity in dry and rainy season on branches from woody species growing in Brazilian Cerrado

Science.gov (United States)

Carmen R. Marcati; Silvia R. Machado; Diego Sotto Podadera; Natalia O. Totti de Lara; Fabio Bosio; Alex C. Wiedenhoeft

2016-01-01

Seasonal cambial activity was investigated in one- to three-year-old branch modules (branch constructional units) of ten woody species from cerrado sensu stricto, a savanna-like ecosystem, of southernBrazil. Relationships between cambial activity and environmental factors (precipitation, temperature,day length) and leaf production were tested using...

Wet Season Spatial Occurrence Of Phytoplankton and Zooplankton

African Journals Online (AJOL)

Administrator

were due to high freshwater inflow from adjoining waterways and reduced tidal incursion from the sea. ... Information dealing with the plankton species of the Lagos lagoon and its environs is ... short season of dry, dusty North-East Trade winds are experienced sometimes between ...... In: Freshwater. Algae of North America.

Seasonal changes of fructans in dimorphic roots of Ichthyothere terminalis (Spreng.) Blake (Asteraceae) growing in Cerrado.

Science.gov (United States)

de Almeida, Lorrayne Veloso; Ferri, Pedro Henrique; Seraphin, José Carlos; de Moraes, Moemy Gomes

2017-11-15

Cerrado is a floristically rich savanna in Brazil, whose vegetation consists of a physiognomic mosaic, influenced by rainfall seasonality. In the dry season rainfall is substantially lower and reduces soil water supply, mainly for herbs and subshrubs. Climatic seasonal variations may well define phenological shifts and induce fluctuations of plant reserve pools. Some Cerrado native species have thickened underground organs that bear buds and store reserves, as adaptive features to enable plant survival following environmental stresses. Asteraceae species accumulate fructans in storage organs, which are not only reserve, but also protecting compounds against the effects of cold and drought. Ichthyothere terminalis is one Asteraceae species abundant in cerrado rupestre, with underground organs consisting of thickened orthogravitropic and diagravitropic roots. The objectives of this study were to analyze how abiotic environmental factors and plant phenology influence fructan dynamics in field grown plants, and verify if fructan metabolism differs in both root types for one year. I. terminalis accumulates inulin-type fructans in 10-40% of the dry mass in both root types. Fructan dynamics have similar patterns described for other Asteraceae species, exhibiting a proportional increase of polysaccharides with the senescence of the aerial organs. Multivariate analyzes showed that, as rainfall decreased, environmental factors had a stronger influence on metabolite levels than phenological shifts in both root types. Only slight differences were found in fructan dynamics between orthogravitropic and diagravitropic roots, suggesting they may have similar fructan metabolism regulation. However, these small differences may reflect distinct microclimatic conditions in both root types and also represent the influence of sink strength. Copyright © 2017 Elsevier B.V. All rights reserved.

An Updated Decision Support Interface: A Tool for Remote Monitoring of Crop Growing Conditions

Science.gov (United States)

Husak, G. J.; Budde, M. E.; Rowland, J.; Verdin, J. P.; Funk, C. C.; Landsfeld, M. F.

2014-12-01

Remote sensing of agroclimatological variables to monitor food production conditions is a critical component of the Famine Early Warning Systems Network portfolio of tools for assessing food security in the developing world. The Decision Support Interface (DSI) seeks to integrate a number of remotely sensed and modeled variables to create a single, simplified portal for analysis of crop growing conditions. The DSI has been reformulated to incorporate more variables and give the user more freedom in exploring the available data. This refinement seeks to transition the DSI from a "first glance" agroclimatic indicator to one better suited for the differentiation of drought events. The DSI performs analysis of variables over primary agricultural zones at the first sub-national administrative level. It uses the spatially averaged rainfall, normalized difference vegetation index (NDVI), water requirement satisfaction index (WRSI), and actual evapotranspiration (ETa) to identify potential hazards to food security. Presenting this information in a web-based client gives food security analysts and decision makers a lightweight portal for information on crop growing conditions in the region. The crop zones used for the aggregation contain timing information which is critical to the DSI presentation. Rainfall and ETa are accumulated from different points in the crop phenology to identify season-long deficits in rainfall or transpiration that adversely affect the crop-growing conditions. Furthermore, the NDVI and WRSI serve as their own seasonal accumulated measures of growing conditions by capturing vegetation vigor or actual evapotranspiration deficits. The DSI is currently active for major growing regions of sub-Saharan Africa, with intention of expanding to other areas over the coming years.

Effect of growing plants on denitrification at high soil nitrate concentrations

International Nuclear Information System (INIS)

Haider, K.; Mosier, A.; Heinemeyer, O.

1987-01-01

The availability of plant rhizosphere C deposits and its influence on microbial denitrification is not clearly defined. Conflicting reports as to the influence of plants and root exudation on denitrification continue to appear in the literature. The results of the authors earlier phytotron study indicated that denitrification was not stimulated in soils planted with corn or wheat compared to unplanted soils. Lower nitrate concentrations in the planted soils, however, may have led to misinterpretation of this data. A second study was conducted, to evaluate the effect of actively growing plants on denitrification where the NO 3 7 content of planted soils was maintained similar to unplanted soils. Simultaneously the C fixed by corn (Zea mays) and the fate of fertilizer N applied to the soil during the growing season were quantified. The corn was grown in a phytotron under a continuous supply of 14 CO 2 in 15 N fertilized soils to which 15 N-NO 3 - was added periodically during the growing season. The results of these studies showed that denitrification was not stimulated in soils planted with corn during active plant growth phase even when soil NO 3 - was relatively high. Denitrification was, however, greater in corn planted than unplanted soil when the recoverable root biomass began to decrease. Less N was immobilized and net 15 N immobilization was lower in planted soils than in unplanted soils. As denitrification was lower in planted soils during the time of active plant growth, the study suggests that root exudates did not stimulate either process

Spatiotemporal patterns of High Mountain Asia's snowmelt season identified with an automated snowmelt detection algorithm, 1987-2016

Science.gov (United States)

Smith, Taylor; Bookhagen, Bodo; Rheinwalt, Aljoscha

2017-10-01

than trends in snowmelt end. (2) Areas with long snowmelt periods, such as the Tibetan Plateau, show the strongest compression of the snowmelt season (negative trends). These trends are apparent regardless of the time period over which the regression is performed. (3) While trends averaged over 3 decades indicate generally earlier snowmelt seasons, data from the last 14 years (2002-2016) exhibit positive trends in many regions, such as parts of the Pamir and Kunlun Shan. Due to the short nature of the time series, it is not clear whether this change is a reversal of a long-term trend or simply interannual variability. (4) Some regions with stable or growing glaciers - such as the Karakoram and Kunlun Shan - see slightly later snowmelt seasons and longer snowmelt periods. It is likely that changes in the snowmelt regime of HMA account for some of the observed heterogeneity in glacier response to climate change. While the decadal increases in regional temperature have in general led to earlier and shortened melt seasons, changes in HMA's cryosphere have been spatially and temporally heterogeneous.

Indo-Pacific sea surface temperature influences on failed consecutive rainy seasons over eastern Africa

Science.gov (United States)

Hoell, Andrew; Funk, Christopher C.

2014-01-01

Rainfall over eastern Africa (10°S–10°N; 35°E–50°E) is bimodal, with seasonal maxima during the "long rains" of March–April–May (MAM) and the "short rains" of October–November–December (OND). Below average precipitation during consecutive long and short rains seasons over eastern Africa can have devastating long-term impacts on water availability and agriculture. Here, we examine the forcing of drought during consecutive long and short rains seasons over eastern Africa by Indo-Pacific sea surface temperatures (SSTs). The forcing of eastern Africa precipitation and circulation by SSTs is tested using ten ensemble simulations of a global weather forecast model forced by 1950–2010 observed global SSTs. Since the 1980s, Indo-Pacific SSTs have forced more frequent droughts spanning consecutive long and short rains seasons over eastern Africa. The increased frequency of dry conditions is linked to warming SSTs over the Indo-west Pacific and to a lesser degree to Pacific Decadal Variability. During MAM, long-term warming of tropical west Pacific SSTs from 1950–2010 has forced statistically significant precipitation reductions over eastern Africa. The warming west Pacific SSTs have forced changes in the regional lower tropospheric circulation by weakening the Somali Jet, which has reduced moisture and rainfall over the Horn of Africa. During OND, reductions in precipitation over recent decades are oftentimes overshadowed by strong year-to-year precipitation variability forced by the Indian Ocean Dipole and the El Niño–Southern Oscillation.

Sub-seasonal-to-seasonal Reservoir Inflow Forecast using Bayesian Hierarchical Hidden Markov Model

Science.gov (United States)

Mukhopadhyay, S.; Arumugam, S.

2017-12-01

Sub-seasonal-to-seasonal (S2S) (15-90 days) streamflow forecasting is an emerging area of research that provides seamless information for reservoir operation from weather time scales to seasonal time scales. From an operational perspective, sub-seasonal inflow forecasts are highly valuable as these enable water managers to decide short-term releases (15-30 days), while holding water for seasonal needs (e.g., irrigation and municipal supply) and to meet end-of-the-season target storage at a desired level. We propose a Bayesian Hierarchical Hidden Markov Model (BHHMM) to develop S2S inflow forecasts for the Tennessee Valley Area (TVA) reservoir system. Here, the hidden states are predicted by relevant indices that influence the inflows at S2S time scale. The hidden Markov model also captures the both spatial and temporal hierarchy in predictors that operate at S2S time scale with model parameters being estimated as a posterior distribution using a Bayesian framework. We present our work in two steps, namely single site model and multi-site model. For proof of concept, we consider inflows to Douglas Dam, Tennessee, in the single site model. For multisite model we consider reservoirs in the upper Tennessee valley. Streamflow forecasts are issued and updated continuously every day at S2S time scale. We considered precipitation forecasts obtained from NOAA Climate Forecast System (CFSv2) GCM as predictors for developing S2S streamflow forecasts along with relevant indices for predicting hidden states. Spatial dependence of the inflow series of reservoirs are also preserved in the multi-site model. To circumvent the non-normality of the data, we consider the HMM in a Generalized Linear Model setting. Skill of the proposed approach is tested using split sample validation against a traditional multi-site canonical correlation model developed using the same set of predictors. From the posterior distribution of the inflow forecasts, we also highlight different system behavior

Low interannual precipitation has a greater negative effect than seedling herbivory on the population dynamics of a short-lived shrub, Schiedea obovata.

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Bialic-Murphy, Lalasia; Gaoue, Orou G

2018-01-01

Climate projections forecast more extreme interannual climate variability over time, with an increase in the severity and duration of extreme drought and rainfall events. Based on bioclimatic envelope models, it is projected that changing precipitation patterns will drastically alter the spatial distributions and density of plants and be a primary driver of biodiversity loss. However, many other underlying mechanisms can impact plant vital rates (i.e., survival, growth, and reproduction) and population dynamics. In this study, we developed a size-dependent integral projection model (IPM) to evaluate how interannual precipitation and mollusk herbivory influence the dynamics of a Hawaii endemic short-lived shrub, Schiedea obovata (Caryophyllaceae). Assessing how wet season precipitation effects population dynamics it critical, as it is the timeframe when most of the foliar growth occurs, plants flower and fruit, and seedlings establish. Temporal variation in wet season precipitation had a greater effect than mollusk herbivory on S . obovata population growth rate λ, and the impact of interannual precipitation on vital rates shifted across plant ontogeny. Furthermore, wet season precipitation influenced multiple vital rates in contrasting ways and the effect of precipitation on the survival of larger vegetative and reproductively mature individuals contributed the most to variation in the population growth rate. Among all combination of wet season precipitation and herbivory intensities, the only scenario that led to a growing population was when high wet precipitation was associated with low herbivory. Our study highlights the importance of evaluating how abiotic factors and plant-consumer interactions influence an organism across its life cycle to fully understand the underpinning mechanisms that structure its spatial and temporal distribution and abundance. Our results also illustrate that for short-lived species, like S. obovata , seedling herbivory can have

Growing up with stress - carbon sequestration and allocation dynamics of a broadleaf evergreen forest

Science.gov (United States)

Griebel, Anne; Bennett, Lauren T.; Arndt, Stefan K.

2016-04-01

Evergreen forests have the potential to sequester carbon year-round due to the presence of leaves with a multi-year lifespan. Eucalypt forests occur in warmer climates where temperature and radiation are not imposing a strong seasonality. Thus, unlike deciduous or many coniferous trees, many eucalypts grow opportunistically as conditions allow. As such, many eucalypts do not produce distinct growth rings, which present challenges to the implementation of standard methods and data interpretation approaches for monitoring and explaining carbon allocation dynamics in response to climatic stress. As a consequence, there is a lack of detailed understanding of seasonal growth dynamics of evergreen forests as a whole, and, in particular, of the influence of climatic drivers on carbon allocation to the various biomass pools. We used a multi-instrument approach in a mixed species eucalypt forest to investigate the influence of climatic drivers on the seasonal growth dynamics of a predominantly temperate and moisture-regulated environment in south-eastern Australia. Ecosystem scale observations of net ecosystem exchange (NEE) from a flux tower in the Wombat forest near Melbourne indicated that the ecosystem is a year-round carbon sink, but that intra-annual variations in temperature and moisture along with prolonged heat waves and dry spells resulted in a wide range of annual sums over the past three years (NEE ranging from ~4 to 12 t C ha-1 yr-1). Dendrometers were used to monitor stem increments of the three dominant eucalypt species. Stem expansion was generally opportunistic with the greatest increments under warm but moist conditions (often in spring and autumn), and the strongest indicators of stem growth dynamics being radiation, vapour pressure deficit and a combined heat-moisture index. Differences in the seasonality of stem increments between species were largely due to differences in the canopy position of sampled individuals. The greatest stem increments were

Spatial Patterns in Biogeochemical Processes During Peak Growing Season in Oiled and Unoiled Louisiana Salt Marshes: A Multi-Year Analysis

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Chelsky, A.; Marton, J. M.; Bernhard, A. E.; Giblin, A. E.; Setta, S. P.; Hill, T. D.; Roberts, B. J.

2016-02-01

Louisiana salt marshes are important sites for carbon and nitrogen cycling because they can mitigate fluxes of nutrients and carbon to the Gulf of Mexico where a large hypoxic zone develops annually. The aim of this study was to investigate spatial and temporal patterns of biogeochemical processes in Louisiana coastal wetlands during peak growing season, and to investigate whether the Deepwater Horizon oil spill resulted in persistent changes to these rates. We measured nitrification potential and sediment characteristics at two pairs of oiled/unoiled marshes in three regions across the Louisiana coast (Terrebonne and east and west Barataria Bay) in July from 2012 to 2015, with plots along a gradient from the salt marsh edge to the interior. Rates of nitrification potential across the coast (overall mean of 901 ± 115 nmol gdw-1 d-1 from 2012-2014) were high compared to other published rates for salt marshes but displayed high variability at the plot level (4 orders of magnitude). Within each region interannual means varied by factors of 2-5. Nitrification potential did not differ with oiling history, but did display consistent spatial patterns within each region that corresponded to changes in relative elevation and inundation, which influence patterns of soil properties and microbial communities. In 2015, we also measured greenhouse gas (CO2, N2O and CH4) production and denitrification enzyme activity rates in addition to nitrification potential across the region to investigate spatial relationships between these processes.

[Responses of sap flow to natural rainfall and continuous drought of tree species growing on bedrock outcrops].

Science.gov (United States)

Zhang, Hui Ling; Ding, Ya Li; Chen, Hong Song; Wang, Ke Lin; Nie, Yun Peng

2018-04-01

This study focused on bedrock outcrops, a very common habitat in karst region of southwest China. To reveal the responses of plant transpiration to natural rainfall and continuous drought, two tree species typical to this habitat, Radermachera sinica and Triadica rotundifolia, were selected as test materials. A rainout shelter was used to simulate continuous drought. The sap flow dynamics were monitored using the method of Granier's thermal dissipation probe (TDP). Our results showed that sap flow density increased to different degrees after rain in different stages of the growing season. Sap flow density of the deciduous species T. rotundifolia was always higher than that of the semi-deciduous species R. sinica. After two months without rainfall input, both species exhibited no obvious decrease in sap flow density, indicating that rainfall was not the dominant source for their water uptake, at least in the short-term. Based on the regression relationships between sap flow density and meteorological factors before and after rainfall, as well as at different stages of continuous drought, we found that the dynamics of meteorological factors contributed little to plant transpiration. The basic transpiration characteristics of both species were not changed in the circumstance of natural rainfall and short-term continuous drought, which would be closely related to the special water storage environments of bedrock outcrops and the reliance on deep water sources by tree species.

Season and severity of prescribed burn in ponderosa pine forests: implications for understory native and exotic plants.

Science.gov (United States)

Becky K. Kerns; Walter G. Thies; Christine G. Niwa

2006-01-01

We investigated herbaceous richness and cover in relation to fire season and severity, and other variables, five growing seasons following prescribed fires. Data were collected from six stands consisting of three randomly applied treatments: no burn, spring burn, and fall burn. Fall burns had significantly more exotic/native annual/biennial (an/bi) species and greater...

A seasonal agricultural drought forecast system for food-insecure regions of East Africa

Science.gov (United States)

Shukla, Shraddhanand; McNally, Amy; Husak, Gregory; Funk, Christopher C.

2014-01-01

 The increasing food and water demands of East Africa's growing population are stressing the region's inconsistent water resources and rain-fed agriculture. More accurate seasonal agricultural drought forecasts for this region can inform better water and agricultural management decisions, support optimal allocation of the region's water resources, and mitigate socio-economic losses incurred by droughts and floods. Here we describe the development and implementation of a seasonal agricultural drought forecast system for East Africa (EA) that provides decision support for the Famine Early Warning Systems Network's science team. We evaluate this forecast system for a region of equatorial EA (2° S to 8° N, and 36° to 46° E) for the March-April-May growing season. This domain encompasses one of the most food insecure, climatically variable and socio-economically vulnerable regions in EA, and potentially the world: this region has experienced famine as recently as 2011. To assess the agricultural outlook for the upcoming season our forecast system simulates soil moisture (SM) scenarios using the Variable Infiltration Capacity (VIC) hydrologic model forced with climate scenarios for the upcoming season. First, to show that the VIC model is appropriate for this application we forced the model with high quality atmospheric observations and found that the resulting SM values were consistent with the Food and Agriculture Organization's (FAO's) Water Requirement Satisfaction Index (WRSI), an index used by FEWS NET to estimate crop yields. Next we tested our forecasting system with hindcast runs (1993–2012). We found that initializing SM forecasts with start-of-season (5 March) SM conditions resulted in useful SM forecast skill (> 0.5 correlation) at 1-month, and in some cases at 3 month lead times. Similarly, when the forecast was initialized with mid-season (i.e. 5 April) SM conditions the skill until the end-of-season improved. This shows that early-season rainfall

Seasonal changes in metal accumulation and distribution in the organs of Phragmites australis (common reed from Lake Skadar, Montenegro

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Kastratović Vlatko

2013-01-01

Full Text Available Due to its ability to accumulate metals, availability throughout the year and its large biomass, Phragmites australis (common reed is suitable for biomonitoring studies for the evaluation of load level of water ecosystem with trace metals. The heavy metals concentration in P.australis tissue can be several ten to several thousand times higher than those in the surrounding water. In this study we examined the content of heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn, Sr and V in sediment, water and different organs of Phragmites australis collected from Lake Skadar, Montenegro, during different seasons of the year 2011. The highest concentrations of Sr were found in the leaves, while the other studied metals showed their highest concentrations in the roots. Thus, P. australis is considered a root bioaccumulation species. For most metals the concentration in roots and stems increases over time until the end of the growing season, and then decreases, while the concentration in leaves increases even after the growing season of the plant. If P. australis is used for phytoremediation purposes, then it should be harvested after the growing season because then the concentration of metals in the aboveground parts is maximal.

Leaf dynamics of Festulolium and Dactylis glomerata L. at the end of the growing season

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Jiří Skládanka

2008-01-01

Full Text Available The paper is focused on the assessment of leaf extension rate (LER, leaf appearance rate (LAR and leaf senescence rate (LSR in the Festulolium (Festuca arundinacea Schreb. × Lolium multiflorum Lam. and in the Dactylis glomerata L. at the end of the growing season from the end of September to the beginning of December. In summer, the swards were used for a single cut (beginning of June or for a double cut (beginning of June and end of July. Measurements were made in three periods from 14 Sept. to 11 Oct., from 11 Oct. to 29 Oct., and from 29 Oct. to 6 Dec. In the first period, LER was higher in Dactylis glomerata L. (3.770 mm tiller−1 d−1 than in Festulolium (2.376 mm tiller−1 d−1. In the second and third period, LER was higher in Festulolium (0.859 resp. 0.271 mm tiller−1 d−1 than in Dactylis glomerata L. (0.694, resp. 0.199 mm tiller−1 d−1. LAR values measured in Festulolium in the studied pe­riods were 0.277 leaf tiller−1 d−1, 0.079 leaf tiller−1 d−1 and 0.038 leaf tiller−1 d−1 and LAR values of Dactylis glomerata L. were 0.225 leaf tiller−1 d−1, 0.054 leaf tiller−1 d−1 and 0.027 leaf tiller−1 d−1. In the course of the whole pe­riod of study, LSR showed the highest values in Dactylis glomerata L. (7.869 mm til­ler−1 d−1, 5.947 mm til­ler−1 d−1 and 4.757 mm tiller−1 d−1 while the LSR values of Festulolium were lower (2.904 mm tiller−1 d−1, 2.375 mm tiller−1 d−1 and 1.205 mm tiller−1 d−1. The influence of both the species and the period of measurement on the LER, LAR and LSR values was statistically highly significant (P < 0.01 to very highly significant (P < 0.001. The interaction between the species and the period of measurement was very highly significant (P < 0.001 in the LER characteristic. The influence of the intensity of sward use in summer on the LSR values was very highly significant (P < 0.001, too.

The Relationship between an Invasive Shrub and Soil Moisture: Seasonal Interactions and Spatially Covarying Relations

Directory of Open Access Journals (Sweden)

Yuhong He

2014-09-01

Full Text Available Recent studies indicate that positive relationships between invasive plants and soil can contribute to further plant invasions. However, it remains unclear whether these relations remain unchanged throughout the growing season. In this study, spatial sequences of field observations along a transect were used to reveal seasonal interactions and spatially covarying relations between one common invasive shrub (Tartarian Honeysuckle, Lonicera tatarica and soil moisture in a tall grassland habitat. Statistical analysis over the transect shows that the contrast between soil moisture in shrub and herbaceous patches vary with season and precipitation. Overall, a negatively covarying relationship between shrub and soil moisture (i.e., drier surface soils at shrub microsites exists during the very early growing period (e.g., May, while in summer a positively covarying phenomenon (i.e., wetter soils under shrubs is usually evident, but could be weakened or vanish during long precipitation-free periods. If there is sufficient rainfall, surface soil moisture and leaf area index (LAI often spatially covary with significant spatial oscillations at an invariant scale (which is governed by the shrub spatial pattern and is about 8 m, but their phase relation in space varies with season, consistent with the seasonal variability of the co-varying phenomena between shrub invasion and soil water content. The findings are important for establishing a more complete picture of how shrub invasion affects soil moisture.

Seasonal Variation of the Material Transport Processes in the Ariake Sea

OpenAIRE

Manda, Atsuyoshi; Kanehara, Hisao; Aoshima, Takashi; Kinoshita, Tsukasa; Uchida, Jun; Nakata, Hideaki; Yanagi, Tetsuo

2010-01-01

Seasonal variation of the salt fluxes in the middle part of the Ariake Sea have been investigated by modeling with hydrographic and meteorological data. The salt flux due to the seasonally averaged density-driven currents accounts for approximately 60% of the total salt flux during summer. The salt flux due to the other processes, that are not treated explicitly, such as the tidal pumping, tideinduced residual currents, and short-term variations of the density- and winddriven currents dominat...

Using Accretionary Hard Parts to Study Changes in Seasonality over Geologic Time

Science.gov (United States)

Ivany, L. C.; Judd, E. J.

2017-12-01

Seasonality has been an enigma for deep-time research. Proxies for mean annual temperature (MAT) are the mainstay of paleoclimate studies, and while these are tremendously informative, seasonal extremes are the variables that matter most for many paleoclimatic, paleoceanographic, and physiologic processes. Seasonality has been difficult to constrain in the rock record, however, because of the need for subannual resolution - very few such archives exist. One of the most promising comes in the form of the mineralized hard parts of organisms that grow by accretion, e.g., mollusks, corals, fish otoliths. Such materials carry a chemical signature of temperature at the time of precipitation, allowing for assessment of the seasonal temperature extremes experienced by the organism. Interpretation of these records in the context of climate, however, are complicated by the overprint of biology - organisms don't necessarily grow all year long, resulting in a truncation of the seasonal cycle regardless of sampling resolution. Furthermore, unrecognized differences in depositional environment or taxon ecology among samples can make comparisons over time even more tenuous. Even with internally consistent datasets, assessment of pattern is rarely based on more than visual inspection. An iterative computational procedure predicated on the assumption of sinusoidal variation in temperature and growth rate can circumvent these concerns. Deviations in the shape of oxygen isotope profiles from the predicted sinusoid allow recovery of the mean and amplitude of temperature variation as well as the timing and duration of growth within years. Estimates of such parameters from multiple specimens allow for meaningful comparisons over time, both for seasonality and the growth response of organisms. We apply this approach to datasets of seasonal variation through the Paleogene of the US Gulf Coastal Plain and the Eocene of Antarctica derived largely from marine bivalve mollusks. In the

Seasonal shift in climatic limiting factors on tree transpiration: evidence from sap flow observations at alpine treelines in southeast Tibet

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Liu Xinsheng

2016-07-01

Full Text Available Alpine and northern treelines are primarily controlled by low temperatures. However, little is known about the impact of low soil temperature on tree transpiration at treelines. We aim to test the hypothesis that in cold-limited forests, the main limiting factors for tree transpiration switch from low soil temperature before summer solstice to atmospheric evaporative demand after summer solstice, which generally results in low transpiration in the early growing season. Sap flow, meteorological factors and predawn needle water potential were continuously monitored throughout one growing season across Smith fir (Abies georgei var. smithii and juniper (Juniperus saltuaria treelines in southeast Tibet. Sap flow started in early May and corresponded to a threshold mean air-temperature of 0 oC. Across tree species, transpiration was mainly limited by low soil temperature prior to the summer solstice but by vapor pressure deficit and solar radiation post-summer solstice, which was further confirmed on a daily scale. As a result, tree transpiration for both tree species was significantly reduced in the pre-summer solstice period as compared to post-summer solstice, resulting in a lower predawn needle water potential for Smith fir trees in the early growing season. Our data supported the hypothesis, suggesting that tree transpiration mainly responds to soil temperature variations in the early growing season. The results are important for understanding the hydrological response of cold-limited forest ecosystems to climate change.

Seasonal measurements of organic acid fluxes over a ponderosa pine forest

Science.gov (United States)

Fulgham, S. R.; Brophy, P.; Link, M.; Ortega, J. V.; Farmer, D.

2016-12-01

The biosphere acts as both a source and a sink of oxidized organic compounds. Ignoring dry deposition leads to overestimation of secondary organic aerosols by aerosol models, while ignoring emission sources underestimates the budget of organic acids. Developing parameterizations for oxidized organic dry deposition and emission requires observational constraints. Although biosphere parameters are impacted by seasonal variability, most reactive, trace-gas exchange measurements are made for only short periods of time in the main growing season. Here we make fast (5 - 10 Hz) and sensitive (e.g. 0.73 ppt mean limit of detection for formic acid with 10 s averaging) eddy covariance measurements of gas-phase organic acids and other oxidized organic species with a high resolution Time-of-Flight Chemical Ionization Mass Spectrometer with acetate and iodide reagent ions. Measurements were made in 4 - 6 week campaigns over five seasons from summer 2015 to fall 2016 as part of the Seasonal Particles in Forests Flux studY (SPIFFY) at the Manitou Experimental Forest Observatory near Woodland Park, Colorado. Permeation tubes were used for online calibration of carboxylic acids including formic (C1), propionic (C3), butyric (C4), methacrylic (CH2C(CH3)COOH), valeric (C5), and heptanoic (C7) acids. Average daytime mixing ratios for formic acid were 100 ± 100 ppt in winter and 1500 ± 1000 ppt in summer 2016. Upward fluxes of formic acid were observed throughout the experiment, daytime averages and standard deviations ranging from 1900 ± 1000 ppt cm s-1 in winter to 170 ± 130 ppt cm s-1 in spring. Propionic (22 ± 22 ppt cm s-1), butyric (17 ± 16 ppt cm s-1), and methacrylic (3.5 ± 6.1 ppt cm s-1) acids exhibit a mix of upward, near-zero, and downward fluxes. Fluxes were exponentially correlated to temperature, suggesting an ecosystem-scale source of these acids. We also measure exchange velocities of a broad suite of other oxidized organic compounds (31.99 m/z to 311.523 m/z in

Leaf blade and petiole nutritional evolution and variability throughout the crop season for Vitis vinifera L. cv. Graciano

Energy Technology Data Exchange (ETDEWEB)

Dominguez, N.; García-Escudero, N.; Romero, I.; Benito, A.; Martín, I.

2015-07-01

An adequate nutritional state of a crop can be kept by means of a well-designed fertilization plan based on the assessment of the nutrient availability throughout the growing season. The objective of this study was to determine the reliability of leaf blade and petiole diagnosis and the period of validity of their references at both flowering and veraison by means of systematic monitoring throughout the complete growing season. The study was carried out in two plots planted with Vitis vinifera L. cv. Graciano within the AOC Rioja (Spain). Blades and petioles were collected throughout a growing season (2006) and total N, P, K, Ca, Mg, Fe, Mn, Zn, Cu and B concentrations were analyzed in both tissues. Results suggest, in general, that petioles have higher variability and lower analysis reproducibility than blades. Therefore, blade could be a more appropriate tissue to evaluate N, P, K, Ca, and Mg at both flowering and veraison in this variety. Micronutrients in blade and petiole showed different variability behaviour in each of the vineyards studied, therefore, based on our results, it was difficult to determine which one could be the best tissue for the nutritional diagnosis of the ‘Graciano’ variety. Seasonal changes of nutrient concentration in both tissues also confirmed the need for reference values for each tissue and each phenological stage. (Author)

Growth-related problems of aging and senescence in fast growing trees grown on short rotations

Energy Technology Data Exchange (ETDEWEB)

Blake, T J

1981-06-01

The paper is aimed at identifying some possible problem areas in the future management of coppice stands on short rotations. The paper considers the possible role of plant hormones, water, cultural and enviromental factors in regulating shoot production, growth and senescence in hardwoods grown on short rotations for biomass production. 77 references.

Responses of soil CO2 fluxes to short-term experimental warming in alpine steppe ecosystem, Northern Tibet.

Science.gov (United States)

Lu, Xuyang; Fan, Jihui; Yan, Yan; Wang, Xiaodan

2013-01-01

Soil carbon dioxide (CO2) emission is one of the largest fluxes in the global carbon cycle. Therefore small changes in the size of this flux can have a large effect on atmospheric CO2 concentrations and potentially constitute a powerful positive feedback to the climate system. Soil CO2 fluxes in the alpine steppe ecosystem of Northern Tibet and their responses to short-term experimental warming were investigated during the growing season in 2011. The results showed that the total soil CO2 emission fluxes during the entire growing season were 55.82 and 104.31 g C m(-2) for the control and warming plots, respectively. Thus, the soil CO2 emission fluxes increased 86.86% with the air temperature increasing 3.74°C. Moreover, the temperature sensitivity coefficient (Q 10) of the control and warming plots were 2.10 and 1.41, respectively. The soil temperature and soil moisture could partially explain the temporal variations of soil CO2 fluxes. The relationship between the temporal variation of soil CO2 fluxes and the soil temperature can be described by exponential equation. These results suggest that warming significantly promoted soil CO2 emission in the alpine steppe ecosystem of Northern Tibet and indicate that this alpine ecosystem is very vulnerable to climate change. In addition, soil temperature and soil moisture are the key factors that controls soil organic matter decomposition and soil CO2 emission, but temperature sensitivity significantly decreases due to the rise in temperature.

What is the current state of scientific knowledge with regard to seasonal and decadal forecasting?

International Nuclear Information System (INIS)

Smith, Doug M; Scaife, Adam A; Kirtman, Ben P

2012-01-01

Environmental factors, such as the frequency, intensity and duration of extreme weather events, are important drivers of migration and displacement of people. There is therefore a growing need for regional climate predictions for the coming seasons to decades. This paper reviews the current state of the art of seasonal to decadal climate prediction, focusing on the potential sources of skill, forecasting techniques, current capability and future prospects. (letter)

Effects of Nitrogen Rate and Regrowth Interval on Perennial Ryegrass Fatty Acid Content during the Growing Season

NARCIS (Netherlands)

Witkowska, I.M.; Wever, C.J.G.; Gort, G.; Elgersma, A.

2008-01-01

The content of fatty acids (FA) in herbage is important for forage quality and animal-source foods, but there is a lack of knowledge on effects of agronomic practices, and on environmental factors related to seasonal variation in FA concentrations and FA composition. This research investigated the

Inter-Seasonal Influenza is Characterized by Extended Virus Transmission and Persistence

Science.gov (United States)

Patterson Ross, Zoe; Komadina, Naomi; Deng, Yi-Mo; Spirason, Natalie; Kelly, Heath A.; Sullivan, Sheena G.; Barr, Ian G.; Holmes, Edward C.

2015-01-01

The factors that determine the characteristic seasonality of influenza remain enigmatic. Current models predict that occurrences of influenza outside the normal surveillance season within a temperate region largely reflect the importation of viruses from the alternate hemisphere or from equatorial regions in Asia. To help reveal the drivers of seasonality we investigated the origins and evolution of influenza viruses sampled during inter-seasonal periods in Australia. To this end we conducted an expansive phylogenetic analysis of 9912, 3804, and 3941 hemagglutinnin (HA) sequences from influenza A/H1N1pdm, A/H3N2, and B, respectively, collected globally during the period 2009-2014. Of the 1475 viruses sampled from Australia, 396 (26.8% of Australian, or 2.2% of global set) were sampled outside the monitored temperate influenza surveillance season (1 May – 31 October). Notably, rather than simply reflecting short-lived importations of virus from global localities with higher influenza prevalence, we documented a variety of more complex inter-seasonal transmission patterns including “stragglers” from the preceding season and “heralds” of the forthcoming season, and which included viruses sampled from clearly temperate regions within Australia. We also provide evidence for the persistence of influenza B virus between epidemic seasons, in which transmission of a viral lineage begins in one season and continues throughout the inter-seasonal period into the following season. Strikingly, a disproportionately high number of inter-seasonal influenza transmission events occurred in tropical and subtropical regions of Australia, providing further evidence that climate plays an important role in shaping patterns of influenza seasonality. PMID:26107631

Seasonal dynamics of mobile carbon supply in Quercus aquifolioides at the upper elevational limit.

Directory of Open Access Journals (Sweden)

Wan-Ze Zhu

Full Text Available Many studies have tried to explain the physiological mechanisms of the alpine treeline phenomenon, but the debate on the alpine treeline formation remains controversial due to opposite results from different studies. The present study explored the carbon-physiology of an alpine shrub species (Quercus aquifolioides grown at its upper elevational limit compared to lower elevations, to test whether the elevational limit of alpine shrubs (<3 m in height are determined by carbon limitation or growth limitation. We studied the seasonal variations in non-structural carbohydrate (NSC and its pool size in Q. aquifolioides grown at 3000 m, 3500 m, and at its elevational limit of 3950 m above sea level (a.s.l. on Zheduo Mt., SW China. The tissue NSC concentrations along the elevational gradient varied significantly with season, reflecting the season-dependent carbon balance. The NSC levels in tissues were lowest at the beginning of the growing season, indicating that plants used the winter reserve storage for re-growth in the early spring. During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations. The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit. This result is consistent with a recent hypothesis for the alpine treeline formation.

Ecophysiological and phenological strategies in seasonally-dry ecosystems: an ecohydrological approach

Science.gov (United States)

Vico, Giulia; Manzoni, Stefano; Thompson, Sally; Molini, Annalisa; Porporato, Amilcare

2015-04-01

Seasonally-dry climates are particularly challenging for vegetation, as they are characterized by prolonged dry periods and often marked inter-annual variability. During the dry season plants face predictable physiological stress due to lack of water, whereas the inter-annual variability in rainfall timing and amounts requires plants to develop flexible adaptation strategies. The variety of strategies observed across seasonally-dry (Mediterranean and tropical) ecosystems is indeed wide - ranging from near-isohydric species that adjust stomatal conductance to avoid drought, to anisohydric species that maintain gas exchange during the dry season. A suite of phenological strategies are hypothesized to be associated to ecophysiological strategies. Here we synthetize current knowledge on ecophysiological and phenological adaptations through a comprehensive ecohydrological model linking a soil water balance to a vegetation carbon balance. Climatic regimes are found to select for different phenological strategies that maximize the long-term plant carbon uptake. Inter-annual variability of the duration of the wet season allows coexistence of different drought-deciduous strategies. In contrast, short dry seasons or access to groundwater favour evergreen species. Climatic changes causing more intermittent rainfall and/or shorter wet seasons are predicted to favour drought-deciduous species with opportunistic water use.

Growing season boundary layer climate and surface exchanges in a subarctic lichen woodland

Science.gov (United States)

Fitzjarrald, David R.; Moore, Kathleen E.

1994-01-01

Between June and August 1990, observations were made at two surface micrometeorological towers near Schefferville Quebec (54 deg 52 min N, 66 deg 40.5 min W), one in a fen and one in the subarctic lichen woodland, and at four surface climatological stations. Data from these surface stations were supplemented by regular radiosonde launches. Supporting measurements of radiative components and soil temperatures allowed heat and moisture balances to be obtained at two sites. The overall surface meteorological experiment design and results of micrometeorological observations made on a 30-m tower in the lichen woodland are presented here. Seasonal variation in the heat and water vapor transport characteristics illustrate the marked effect of the late summer climatological shift in air mass type. During the first half of the summer, average valley sidewalls only 100 m high are sufficient to channel winds along the valley in the entire convective boundary layer. Channeling effects at the surface, known for some time at the long-term climate station in Schefferville, are observed both at ridge top and in the valley, possibly the response of the flow to the NW-SE orientation of valleys in the region. Diurnal surface temperature amplitude at ridge top (approximately equal to 10 C) was found to be half that observed in the valley. Relatively large differences in precipitation among these stations and the climatological station at Schefferville airport were observed and attributed to the local topography. Eddy correlation observations of the heat, moisture and momentum transports were obtained from a 30-m tower above a sparse (approximately equal to 616 stems/ha) black spruce lichen woodland. Properties of the turbulent surface boundary layer agree well with previous wind tunnel studies over idealized rough surfaces. Daytime Bowen ratios of 2.5-3 are larger than those reported in previous studies. Surface layer flux data quality was assessed by looking at the surface layer heat

NEW SEASON NEW HOPES: OFF-SEASON OPTIMISM

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Oguz Ersan

2017-12-01

Full Text Available While literature on the relation between on-field sports performance and stock returns is ample, there is very limited evidence on off-season stage. Constituting around 3 months, off-seasons do not only occupy a significant part of the year but also represent totally different characteristics than on-seasons. They lack the periodic, unambiguous news events in on-seasons (match results, instead they are associated with highly uncertain transfer news and rumors. We show that this distinction has several impacts on the stock market performances of soccer clubs. Most notably, off-seasons generate substantially higher (excess returns. After controlling for other variables, the estimated effect of off-season periods is as high as 38.75%, annually. In line with several seminal studies, we link this fact to increased optimism and betting behavior through uncertain periods; and periods prior to the start of a new calendar (in our case, new season. For all of the examined 7 clubs (3 from Italy and 4 from Turkey, mean excess returns over the market are positive (negative in off-seasons (on-seasons. On-seasons are associated with increased trading activity due to more frequent news. Stocks of Italian clubs are evidently more volatile through off-seasons while volatility results for the stocks of Turkish clubs are not consistent.

The effective mitigation of greenhouse gas emissions from rice paddies without compromising yield by early-season drainage.

Science.gov (United States)

Islam, Syed Faiz-Ul; van Groenigen, Jan Willem; Jensen, Lars Stoumann; Sander, Bjoern Ole; de Neergaard, Andreas

2018-01-15

Global rice production systems face two opposing challenges: the need to increase production to accommodate the world's growing population while simultaneously reducing greenhouse gas (GHG) emissions. Adaptations to drainage regimes are one of the most promising options for methane mitigation in rice production. Whereas several studies have focused on mid-season drainage (MD) to mitigate GHG emissions, early-season drainage (ED) varying in timing and duration has not been extensively studied. However, such ED periods could potentially be very effective since initial available C levels (and thereby the potential for methanogenesis) can be very high in paddy systems with rice straw incorporation. This study tested the effectiveness of seven drainage regimes varying in their timing and duration (combinations of ED and MD) to mitigate CH 4 and N 2 O emissions in a 101-day growth chamber experiment. Emissions were considerably reduced by early-season drainage compared to both conventional continuous flooding (CF) and the MD drainage regime. The results suggest that ED+MD drainage may have the potential to reduce CH 4 emissions and yield-scaled GWP by 85-90% compared to CF and by 75-77% compared to MD only. A combination of (short or long) ED drainage and one MD drainage episode was found to be the most effective in mitigating CH 4 emissions without negatively affecting yield. In particular, compared with CF, the long early-season drainage treatments LE+SM and LE+LM significantly (pemissions were small and not significantly affected by ED. It is concluded that ED+MD drainage might be an effective low-tech option for small-scale farmers to reduce GHG emissions and save water while maintaining yield. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Seasonally dynamic fungal communities in the Quercus macrocarpa phyllosphere differ between urban and nonurban environments.

Science.gov (United States)

Jumpponen, A; Jones, K L

2010-04-01

*The fungal richness, diversity and community composition in the Quercus macrocarpa phyllosphere were compared across a growing season in trees located in six stands within and outside a small urban center using 454-sequencing and DNA tagging. The approaches did not differentiate between endophytic and epiphytic fungal communities. *Fungi accumulated in the phyllosphere rapidly and communities were temporally dynamic, with more than a third of the analyzed operational taxonomic units (OTUs) and half of the BLAST-inferred genera showing distinct seasonal patterns. The seasonal patterns could be explained by fungal life cycles or environmental tolerances. *The communities were hyperdiverse and differed between the urban and nonurban stands, albeit not consistently across the growing season. Foliar macronutrients (nitrogen (N), potassium (K) and sulfur (S)), micronutrients (boron (B), manganese (Mn) and selenium (Se)) and trace elements (cadmium (Cd), lead (Pb) and zinc (Zn)) were enriched in the urban trees, probably as a result of anthropogenic activities. Because of correlations with the experimental layout, these chemical elements should not be considered as community drivers without further empirical studies. *We suggest that a combination of mechanisms leads to differences between urban and nonurban communities. Among those are stand isolation and size, nutrient and pollutant accumulation plus stand management, including fertilization and litter removal.

Influenza Seasonal Summary, 2014-2015 Season

Science.gov (United States)

2015-08-14

Influenza Seasonal Summarv 2014-2015 Season EpiData Center Department Communicable Disease Division NMCPHC-EDC-TR-394-2015 REPORT DOCUMENTATION... Influenza Seasonal Summary, 2014-2015 Season Sb. GRANT NUMBER $c. PROGRAM ELEMENT NUMBER 6. AUTHORjS) Sd. PROJECT NUMBER Ashleigh K McCabe, Kristen R...SUPPLEMENTARY NOTES 1<l. ABSTRACT This report summartzes influenza activity among Department of Navy (DON) and Depar1ment of Defense (DOD

Exposure to vibrations in wine growing

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Domenico Pessina

2013-09-01

Full Text Available Apart the winter period, the activity in specialized agricultural cultivations (i.e. wine- and fruit-growing is distributed for a long period of the year. Some tasks, such as pesticide distribution, are repeated several times during the growing season. On the other hand, mechanization is one of the pillars on which is based the modern agriculture management. As a consequence, in wine growing the tractor driver has to be considered a worker potentially subjected to high level of vibrations, due to the poor machinery conditions often encountered, and sometimes to the rough soil surface of the vineyard combined with the high travelling speed adopted in carrying out many operations. About vibrations, the Italian Decree 81/08 basically refers to the European Directive 2002/44/CE, that provides some very strict limits of exposure, both for whole body and hand-arm districts. In Oltrepo pavese, a large hilly area located the south part of the Pavia province (Lombardy - Italy wine growing is the main agricultural activity; for this reason, a detailed survey on the vibration levels recorded at the tractor driver’s seat was carried out, in order to ascertain the real risk to which the operators are exposed. The activity in wine growing has been classified into 6 groups of similar tasks, as follows: 1. canopy management: pruning, trimming, binding, stripping, etc.; 2. soil management: harrowing, hoeing, subsoiling etc.; 3. inter-row management: chopping of pruning , pinching, grass mowing, etc.; 4. crop protection: pesticides and fungicides distribution, sulfidation, foliar fertilization, etc.; 5. grape harvesting: manual or mechanical; 6. transport: from the vineyard to the cellar. For each group of tasks, the vibration levels on 3 the traditional axes (x, y and z were recorded, and then an exposure time was calculated for each of them, in order to ascertain the risk level in comparison to what provided by the dedicated standard. Finally, a detailed

Microtopographic and Hydrological Controls over Respiratory Efflux and Late-Season Arctic Methane Emissions

Science.gov (United States)

Wilkman, E.; Zona, D.; Oechel, W. C.

2014-12-01

In recent years, Arctic peatlands have released approximately 35 Tg (3.5 x 1012g) of CH4 annually, corresponding to around 1/3 of the aggregate wetland CH4 fluxes and 16% of all natural emissions. As climate models increasingly suggest that current warming trends in the Arctic (4-8 °C higher annual surface air temperatures) will continue by century's end, carbon (C) cycling in these northern climes may be further amplified. Although much has been learned in recent decades, uncertainty remains in regard to the spatial and temporal extent of CO2 and CH4 emissions from these systems. Chamber based carbon flux measurements were gathered for three growing seasons from June 2007 to September 2013 in Barrow, Alaska to investigate the diurnal, weekly, and monthly patterns of CO2 and CH4 flux in the North American Arctic. For the 2007 and 2008 growing seasons, high temporal frequency auto-chambers (LI-8100A Automated Soil Flux System, LI-COR Biosciences) were used to gather over 18,000 individual flux measurements. From July to September 2013 an Ultraportable Greenhouse Gas Analyzer (Los Gatos Research Inc.) was deployed in concert with this soil flux system to gather high temporal frequency soil CO2 and CH4 fluxes. Nearby eddy covariance towers provided auxiliary meteorological and environmental data, while weekly transects amassed further surficial hydrological measures (pH, thaw depth, water table). For earlier periods of data, respiratory fluxes were partitioned into five microtopographic classes (polygon rims and troughs, low centered basins, high ridges, and flat mesic terrain). Conversely, for the later periods of data covered chamber fluxes were partitioned into three 'habitat' types (High, Medium, Wet) based on corresponding aboveground average water table extent. Marked dissimilarities were noted across habitat types and microtopographic classes. In general more mesic, waterlogged regions released greater quantities of CO2 across the growing season, while

Long-term follow-up of large maxillary advancements with distraction osteogenesis in growing and non-growing cleft lip and palate patients.

Science.gov (United States)

Meazzini, Maria Costanza; Basile, Valentina; Mazzoleni, Fabio; Bozzetti, Alberto; Brusati, Roberto

2015-01-01

Maxillary distraction osteogenesis (DO) in cleft lip and palate patients has been described by several authors, but most studies have a relatively short follow-up and do not clearly separate growing patients from non-growing patients. The records of 22 consecutive patients affected by cleft lip and palate, who underwent Le Fort I osteotomy and maxillary distraction with a rigid external distractor (RED), were reviewed. The sample was subdivided into a growing and a non-growing group. All patients had pre-DO cephalometric records, immediately post DO, 12 months post DO and long-term records with a long-term follow-up of >5 years (range 5-13 years). As a control sample for the growing group, cleft children with a negative overjet not subjected to distraction or any protraction treatment during growth were followed up until the completion of growth. The average maxillary advancement in the growing group was 22.2 ± 5.5 mm (range: 15-32 mm); in the non-growing group, it was 17.7 ± 6.6 mm (range: 6-25 mm). Excellent post-surgical stability was recorded in the adult sample. On the other hand, growing children had an average 16% relapse in the first year post DO and an additional 26% relapse in the long-term follow-up. This study seems to point out that early Le Fort I DO allows for the correction of very severe deformities. It is followed by a relatively high amount of true skeletal relapse in children with cleft lip and palate. Prognosis should be discussed in depth with the family and true aesthetic and psychological needs assessed. Copyright © 2014 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

Seasonal hydroclimatic impacts of Sun Corridor expansion

International Nuclear Information System (INIS)

Georgescu, M; Mahalov, A; Moustaoui, M

2012-01-01

Conversion of natural to urban land forms imparts influence on local and regional hydroclimate via modification of the surface energy and water balance, and consideration of such effects due to rapidly expanding megapolitan areas is necessary in light of the growing global share of urban inhabitants. Based on a suite of ensemble-based, multi-year simulations using the Weather Research and Forecasting (WRF) model, we quantify seasonally varying hydroclimatic impacts of the most rapidly expanding megapolitan area in the US: Arizona’s Sun Corridor, centered upon the Greater Phoenix metropolitan area. Using a scenario-based urban expansion approach that accounts for the full range of Sun Corridor growth uncertainty through 2050, we show that built environment induced warming for the maximum development scenario is greatest during the summer season (regionally averaged warming over AZ exceeds 1 °C). Warming remains significant during the spring and fall seasons (regionally averaged warming over AZ approaches 0.9 °C during both seasons), and is least during the winter season (regionally averaged warming over AZ of 0.5 °C). Impacts from a minimum expansion scenario are reduced, with regionally averaged warming ranging between 0.1 and 0.3 °C for all seasons except winter, when no warming impacts are diagnosed. Integration of highly reflective cool roofs within the built environment, increasingly recognized as a cost-effective option intended to offset the warming influence of urban complexes, reduces urban-induced warming considerably. However, impacts on the hydrologic cycle are aggravated via enhanced evapotranspiration reduction, leading to a 4% total accumulated precipitation decrease relative to the non-adaptive maximum expansion scenario. Our results highlight potentially unintended consequences of this adaptation approach within rapidly expanding megapolitan areas, and emphasize the need for undeniably sustainable development paths that account for

Short communication: Assessment of activity patterns of growing rabbits in a flux-controlled chamber

Directory of Open Access Journals (Sweden)

Irene Olivas

2013-06-01

Full Text Available Flux-controlled and metabolic chambers are often used for nutritional and environmental studies. However, the potential alterations of animal behaviour and welfare are so far not fully understood. In consequence, this study had 2 main objectives: to assess potential alterations of animal activity pattern and time budget inside a flux chamber, and to assess the importance of the “rearing up” behaviour. To this end, 10 growing rabbits of different ages (from 1 to 5 wk of the growing period were housed inside a flux chamber. Their activity was continuously recorded and assessed, determining the frequency and duration of 8 different behaviours: lying, sleeping, sitting, eating, drinking, walking, rearing up and others. Nocturnal rabbit behaviour and time budget were not altered inside the chamber if compared to previously described rabbit activity under conventional cages. In addition, rabbits in this experiment presented a tendency to perform “rearing up” when housed inside the flux chamber.

Diurnal and seasonal changes in stem increment and water use by yellow poplar trees in response to environmental stress.

Science.gov (United States)

McLaughlin, Samuel B; Wullschleger, Stan D; Nosal, Miloslav

2003-11-01

To evaluate indicators of whole-tree physiological responses to climate stress, we determined seasonal, daily and diurnal patterns of growth and water use in 10 yellow poplar (Liriodendron tulipifera L.) trees in a stand recently released from competition. Precise measurements of stem increment and sap flow made with automated electronic dendrometers and thermal dissipation probes, respectively, indicated close temporal linkages between water use and patterns of stem shrinkage and swelling during daily cycles of water depletion and recharge of extensible outer-stem tissues. These cycles also determined net daily basal area increment. Multivariate regression models based on a 123-day data series showed that daily diameter increments were related negatively to vapor pressure deficit (VPD), but positively to precipitation and temperature. The same model form with slight changes in coefficients yielded coefficients of determination of about 0.62 (0.57-0.66) across data subsets that included widely variable growth rates and VPDs. Model R2 was improved to 0.75 by using 3-day running mean daily growth data. Rapid recovery of stem diameter growth following short-term, diurnal reductions in VPD indicated that water stored in extensible stem tissues was part of a fast recharge system that limited hydration changes in the cambial zone during periods of water stress. There were substantial differences in the seasonal dynamics of growth among individual trees, and analyses indicated that faster-growing trees were more positively affected by precipitation, solar irradiance and temperature and more negatively affected by high VPD than slower-growing trees. There were no negative effects of ozone on daily growth rates in a year of low ozone concentrations.

An analysis of seasonal predictability in coupled model forecasts

Energy Technology Data Exchange (ETDEWEB)

Peng, P.; Wang, W. [NOAA, Climate Prediction Center, Washington, DC (United States); Kumar, A. [NOAA, Climate Prediction Center, Washington, DC (United States); NCEP/NWS/NOAA, Climate Prediction Center, Camp Springs, MD (United States)

2011-02-15

In the recent decade, operational seasonal prediction systems based on initialized coupled models have been developed. An analysis of how the predictability of seasonal means in the initialized coupled predictions evolves with lead-time is presented. Because of the short lead-time, such an analysis for the temporal behavior of seasonal predictability involves a mix of both the predictability of the first and the second kind. The analysis focuses on the lead-time dependence of ensemble mean variance, and the forecast spread. Further, the analysis is for a fixed target season of December-January-February, and is for sea surface temperature, rainfall, and 200-mb height. The analysis is based on a large set of hindcasts from an initialized coupled seasonal prediction system. Various aspects of predictability of the first and the second kind are highlighted for variables with long (for example, SST), and fast (for example, atmospheric) adjustment time scale. An additional focus of the analysis is how the predictability in the initialized coupled seasonal predictions compares with estimates based on the AMIP simulations. The results indicate that differences in the set up of AMIP simulations and coupled predictions, for example, representation of air-sea interactions, and evolution of forecast spread from initial conditions do not change fundamental conclusion about the seasonal predictability. A discussion of the analysis presented herein, and its implications for the use of AMIP simulations for climate attribution, and for time-slice experiments to provide regional information, is also included. (orig.)

A preliminary study of the effects of plastic film-mulched raised beds on soil temperature and crop performance of early-sown short-season spring maize (Zea mays L. in the North China Plain

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Jing Dang

2016-08-01

Full Text Available To identify a strategy for earlier sowing and harvesting of spring maize (Zea mays L. in an alternative maize–maize double cropping system, a 2-year field experiment was performed at Quzhou experimental station of China Agricultural University in 2014 and 2015. A short-season cultivar, Demeiya number 1 (KX7349, was used in the experiment. Soil temperature to 5 cm depth in the early crop growth stage, crop growth, crop yield, and water use of different treatments (plastic film-mulched raised bed (RF and flat field without plastic film mulching (CK in 2014; RF, plastic film-mulched flat field (FF, and CK in 2015 were measured or calculated and compared. Soil temperature in the film-mulched treatments was consistently higher than that in CK (1.6–3.5 °C in average during the early growth stage. Crops in plastic film-mulched treatments used 214 fewer growing-degree days (GDDs in 2014 and 262 fewer GDDs in 2015. In 2014, the RF treatment yielded 32.7% higher biomass than CK, although its 9.4% higher grain yield was not statistically significant. Also, RF used 17.9% less water and showed 33.1% higher water use efficiency (WUE than CK. In 2015, RF and FF showed 56.2% and 49.5% higher yield, 15.0% and 4.5% lower water use (ET, and 63.4% and 75.7% higher WUE, respectively, than CK. RF markedly increased soil temperature in the early crop season, accelerated crop growth, reduced ET, and greatly increased crop yield and WUE. Compared with FF, RF had no obvious effect on crop growth rate, although soil temperature during the period between sowing and stem elongation was slightly increased. However, RF resulted in lower ET and higher WUE than FF. Effects of RF on soil water dynamics as well as its cost-effectiveness remain topics for further study.

Temporal and spatial variability of frost-free seasons in the Great Lakes region of the United States

Science.gov (United States)

Lejiang Yu; Shiyuan Zhong; Xindi Bian; Warren E. Heilman; Jeffrey A. Andresen

2014-01-01

The frequency and timing of frost events and the length of the growing season are critical limiting factors in many human and natural ecosystems. This study investigates the temporal and spatial variability of the date of last spring frost (LSF), the date of first fall frost (FFF), and the length of the frost-free season (FFS) in the Great Lakes region of the United...

Optimal design and application of a compound cold storage system combining seasonal ice storage and chilled water storage

NARCIS (Netherlands)

Yan, C.; Shi, W.; Li, X.; Zhao, Y.

2016-01-01

Seasonal cold storage using natural cold sources for cooling is a sustainable cooling technique. However, this technique suffers from limitations such as large storage space and poor reliability. Combining seasonal storage with short-term storage might be a promising solution while it is not

Seasonal Variability in European Radon Measurements

Science.gov (United States)

Groves-Kirkby, C. J.; Denman, A. R.; Phillips, P. S.; Crockett, R. G. M.; Sinclair, J. M.

2009-04-01

In temperate climates, domestic radon concentration levels are generally seasonally dependent, the level in the home reflecting the convolution of two time-dependent functions. These are the source soil-gas radon concentration itself, and the principal force driving radon into the building from the soil, namely the pressure-difference between interior and exterior environment. While the meteorological influence can be regarded as relatively uniform on a European scale, its variability being defined largely by the influence of North-Atlantic weather systems, soil-gas radon is generally more variable as it is essentially geologically dependent. Seasonal variability of domestic radon concentration can therefore be expected to exhibit geographical variability, as is indeed the case. To compensate for the variability of domestic radon levels when assessing the long term radon health risks, the results of individual short-term measurements are generally converted to equivalent mean annual levels by application of a Seasonal Correction Factor (SCF). This is a multiplying factor, typically derived from measurements of a large number of homes, applied to the measured short-term radon concentration to provide a meaningful annual mean concentration for dose-estimation purposes. Following concern as to the universal applicability of a single SCF set, detailed studies in both the UK and France have reported location-specific SCF sets for different regions of each country. Further results indicate that SCFs applicable to the UK differ significantly from those applicable elsewhere in Europe and North America in both amplitude and phase, supporting the thesis that seasonal variability in indoor radon concentration cannot realistically be compensated for by a single national or international SCF scheme. Published data characterising the seasonal variability of European national domestic radon concentrations, has been collated and analysed, with the objective of identifying

Spatiotemporal patterns of High Mountain Asia's snowmelt season identified with an automated snowmelt detection algorithm, 1987–2016

Directory of Open Access Journals (Sweden)

T. Smith

2017-10-01

trends, but with generally smaller magnitudes than trends in snowmelt end. (2 Areas with long snowmelt periods, such as the Tibetan Plateau, show the strongest compression of the snowmelt season (negative trends. These trends are apparent regardless of the time period over which the regression is performed. (3 While trends averaged over 3 decades indicate generally earlier snowmelt seasons, data from the last 14 years (2002–2016 exhibit positive trends in many regions, such as parts of the Pamir and Kunlun Shan. Due to the short nature of the time series, it is not clear whether this change is a reversal of a long-term trend or simply interannual variability. (4 Some regions with stable or growing glaciers – such as the Karakoram and Kunlun Shan – see slightly later snowmelt seasons and longer snowmelt periods. It is likely that changes in the snowmelt regime of HMA account for some of the observed heterogeneity in glacier response to climate change. While the decadal increases in regional temperature have in general led to earlier and shortened melt seasons, changes in HMA's cryosphere have been spatially and temporally heterogeneous.

A methodology for investigation of the seasonal evolution in proglacial hydrograph form

Science.gov (United States)

Hannah, David M.; Gurnell, Angela M.; McGregor, Glenn R.

1999-11-01

This paper advances an objective method of diurnal hydrograph classification as an aid to exploring changes in the hydrological functioning of glacierized catchments over the ablation season. The temporal sequencing of different hydrograph classes allows identification of seasonal evolution in hydrograph form and also assists delimitation of hydrologically-meaningful time periods of similar diurnal discharge response. The effectiveness of this approach is illustrated by applying it to two contrasting summer discharge records for a small cirque basin. By comparing the results with patterns of surface energy receipt and glacier ablation, the seasonally transient relative influences of: (i) surface meltwater production and (ii) meltwater routing and storage conditions within the intervening glacier drainage system in determining runoff are elucidated. The method successfully characterizes distinct seasonal-scale changes in the diurnal outflow hydrograph during the ablation-dominated 1995 melt season but is also able to reveal underlying trends and short-term fluctuations in the precipitation-dominated, poorly ablation-regulated 1996 melt season. The limitations and benefits of this hydrograph classification technique are evaluated.

Proxy of monsoon seasonality in carbon isotopes from paleosols of the southern Chinese Loess Plateau

Science.gov (United States)

Wang, Hongfang; Follmer, L.R.

1998-01-01

Soil organic matter (SOM) and soil carbonate (SC) are common constituents in soils and are directly related to plant growth. SOM accumulates gradually from the decomposition of plant material over time, whereas SC formation is biased to dry-season soil-dissolved CO2 that derives from plant respiration during a drying phase of the growing season. In some mixed C3-C4 environments, the peak of C3 and C4 plant metabolism differs seasonally, and the carbon source that contributes to the SOM and SC can be different. Consequently, ??13C(SOM) values reflect an annual average of the floral biomass, but ??13C(SC) values reflect a seasonal aspect of the plant community. The relationship between ??13C(SC) and ??13C(SOM) is mainly controlled by how different the seasonal conditions are. Our results suggest that the relationship is a seasonal proxy that can be used to differentiate the seasonality effects of Indian, East Asian, and Siberian monsoons on the Chinese Loess Plateau during the last interglacial-glacial cycle.

Seasonal photosynthetic activity in evergreen conifer leaves monitored with spectral reflectance

Science.gov (United States)

Wong, C. Y.; Gamon, J. A.

2013-12-01

productivity. Furthermore, the seasonal transitions between photosynthetically active and inactive states can be clearly detected by the PRI. These findings have implications for using remote sensing to detect dynamics in photosynthetic activity in response to changing growing season length in northern latitudes.

Land Surface Phenologies and Seasonalities of Croplands and Grasslands in the US Prairie Pothole Region Using Passive Microwave Data (2003-2015)

Science.gov (United States)

Alemu, W. G.; Henebry, G. M.

2017-12-01

Grasslands and wetlands in the Prairie Pothole Region (PPR) have been converted to croplands in recent years. Crops cultivated in the PPR are also changing: spring wheat and alfalfa/hay are being switched to corn and soybean due to biofuel demand. According to the USDA Cropland Data Layer (CDL) from 2003 to 2015, spring wheat significantly decreased (r2 = 0.74), while corn and soybeans significantly increased (r2 = 0.86). We characterized land surface phenologies and land surface seasonalities across the PPR using the finer temporal (twice daily) but much lower spatial (25 km) resolution Advanced Microwave Scanning Radiometer (AMSR: blended from AMSR-E and AMSR2) enhanced land surface parameters for 2003-2015 (DOY 91-330 annual cycles). We tracked the temporal development of these land surface parameters as a function of accumulated growing degree-days (AGDD) based on the AMSR retrieved air temperature data. Growing degree-days (GDD) revealed distinct seasonality typical to temperate grasslands and croplands. GDD peaks were 23°C and it peaks at 1700°C AGDD. Precipitable water vapor (V) displayed seasonality comparable to GDD. Vegetation optical depth (VOD) revealed distinct land surface phenologies for grasslands versus croplands. We explored the changing crop fractions within the 25 km AMSR pixels using the CDL. Crop-dominated sites VOD time series caught the early spring growth, ploughing, and crop growth dynamics. In contrast, the VOD time series at grass-dominated sites exhibited a lower but more extended amplitude throughout the non-frozen season. VODs peaked at 1.6 and 1.3 for croplands and grasslands, respectively. Croplands peaked about a month later than grasslands (2200 °C AGDD vs. 1600 °C AGDD). The other parameters available from the AMSR dataset—soil moisture (sm), and fractional open water (fw)—together with the AGDD time series constructed from the AMSR air temperature data revealed the passage of storm systems during the growing season. Soil

Photoperiodic Co-Regulation of Kisspeptin, Neurokinin B and Dynorphin in the Hypothalamus of a Seasonal Rodent

DEFF Research Database (Denmark)

Bartzen-Sprauer, J; Klosen, P; Ciofi, P

2014-01-01

In many species, sexual activity varies on a seasonal basis. Kisspeptin (Kp), a hypothalamic neuropeptide acting as a strong activator of gonadotrophin-releasing hormone neurones, plays a critical role in this adaptive process. Recent studies report that two other neuropeptides, namely neurokinin...... (NKB) and dynorphin (DYN), are co-expressed with Kp (and therefore termed KNDy neurones) in the arcuate nucleus and that these peptides are also considered to influence GnRH secretion. The present study aimed to establish whether hypothalamic NKB and DYN expression is photoperiod......-dependent in a seasonal rodent, the Syrian hamster, which exhibits robust seasonal rhythms in reproductive activity. The majority of Kp neurones in the arcuate nucleus co-express NKB and DYN and the expression of all three peptides is decreased under a short (compared to long) photoperiod, leading to a 60% decrease......-localise with RFRP-immunoreactive neurones, and the expression of both NKB and DYN is higher under a short photoperiod, which is opposite to the short-day inhibition of RFRP expression. In conclusion, the present study shows that NKB and DYN display different photoperiodic variations in the Syrian hamster...

Seasonal variation in the temperature sensitivity of proteolytic enzyme activity in temperate forest soils

Science.gov (United States)

Brzostek, Edward R.; Finzi, Adrien C.

2012-03-01

Increasing soil temperature has the potential to alter the activity of the extracellular enzymes that mobilize nitrogen (N) from soil organic matter (SOM) and ultimately the availability of N for primary production. Proteolytic enzymes depolymerize N from proteinaceous components of SOM into amino acids, and their activity is a principal driver of the within-system cycle of soil N. The objectives of this study were to investigate whether the soils of temperate forest tree species differ in the temperature sensitivity of proteolytic enzyme activity over the growing season and the role of substrate limitation in regulating temperature sensitivity. Across species and sampling dates, proteolytic enzyme activity had relatively low sensitivity to temperature with a mean activation energy (Ea) of 33.5 kJ mol-1. Ea declined in white ash, American beech, and eastern hemlock soils across the growing season as soils warmed. By contrast, Eain sugar maple soil increased across the growing season. We used these data to develop a species-specific empirical model of proteolytic enzyme activity for the 2009 calendar year and studied the interactive effects of soil temperature (ambient or +5°C) and substrate limitation (ambient or elevated protein) on enzyme activity. Declines in substrate limitation had a larger single-factor effect on proteolytic enzyme activity than temperature, particularly in the spring. There was, however, a large synergistic effect of increasing temperature and substrate supply on proteolytic enzyme activity. Our results suggest limited increases in N availability with climate warming unless there is a parallel increase in the availability of protein substrates.

[Effects of Short-time Conservation Tillage Managements on Greenhouse Gases Emissions from Soybean-Winter Wheat Rotation System].

Science.gov (United States)

Xie, Yan; Chen, Xi; Hu, Zheng-hua; Chen, Shu-tao; Zhang, Han; Ling, Hui; Shen, Shuang-he

2016-04-15

Field experiments including one soybean growing season and one winter-wheat growing season were adopted. The experimental field was divided into four equal-area sub-blocks which differed from each other only in tillage managements, which were conventional tillage (T) , no-tillage with no straw cover ( NT) , conventional tillage with straw cover (TS) , and no-tillage with straw cover (NTS). CO₂ and N₂O emission fluxes from soil-crop system were measured by static chamber-gas chromatograph technique. The results showed that: compared with T, in the soybean growing season, NTS significantly increased the cumulative amount of CO₂ (CAC) from soil-soybean system by 27.9% (P = 0.045) during the flowering-podding stage, while NT significantly declined CAC by 28.9% (P = 0.043) during the grain filling-maturity stage. Compared with T, NT significantly declined the cumulative amount of N₂O (CAN) by 28.3% (P = 0.042) during the grain filling-maturity stage. In the winter-wheat growing season, compared with T, TS and NT significantly declined CAC by 24.3% (P = 0.032) and 36.0% (P = 0.041) during the elongation-booting stage, and also declined CAC by 26.8% (P = 0.027) and 33.1% (P = 0.038) during the maturity stage. During the turning-green stage, compared with T treatment, NT, NTS, and TS treatments had no significant effect on CAN, while NTS significant declined CAN by 42.0% (P = 0.035) compared with NT. Our findings suggested that conservation tillage managements had a more significant impact on CO₂ emission than 20 emission from soil-crop system.

BLOOD METABOLIC HORMONES AND LEPTIN IN GROWING LAMBS

Directory of Open Access Journals (Sweden)

Zvonko Antunović

2010-12-01

Full Text Available The aim of this paper is to determine the concentration of blood metabolic hormones and leptin levels in growing lambs. The research was carried out on Tsigai lambs in two periods (suckling and fattening during the winter feeding season. Lambs were suckling and ate a food mixture and alfalfa hay ad libitum, while during the fattening period they were fed only with the above mentioned mixture and alfalfa hay ad libitum. Their blood was analyzed on 35th and 75th day of age. Concentrations of minsulin, leptin and thyroid hormones were determined in the blood serum of lambs during both periods. In the blood of fattening lambs significantly higher (P0.05 insulin concentrations (1.05 and 0.54 μU/mL, were determined, compared to suckling lambs. A significant strong positive correlation between serum leptin and insulin (r = 0.85, P0.05. The concentration of thyroid hormones did not significantly differ depending on the period of measurement. These changes indicate that the measurement concentrations of metabolic hormones and leptin in blood are very important in order to understand the changes of metabolism and nutrient supply in growing lambs.

Sustainable biochar effects for low carbon crop production: A 5-crop season field experiment on a low fertility soil from Central China

Science.gov (United States)

Liu, X.

2014-12-01

Biochar's effects on improving soil fertility, enhancing crop productivity and reducing greenhouse gases (GHGs) emission from croplands had been well addressed in numerous short-term experiments with biochar soil amendment (BSA) mostly in a single crop season / cropping year. However, the persistence of these effects, after a single biochar application, has not yet been well known due to limited long-term field studies so far. Large scale BSA in agriculture is often commented on the high cost due to large amount of biochar in a single application. Here, we try to show the persistence of biochar effects on soil fertility and crop productivity improvement as well as GHGs emission reduction, using data from a field experiment with BSA for 5 crop seasons in central North China. A single amendment of biochar was performed at rates of 0 (C0), 20 (C20) and 40 t ha-1 (C40) before sowing of the first crop season. Emissions of CO2, CH4 and N2O were monitored with static closed chamber method throughout the crop growing season for the 1st, 2nd and 5th cropping. Crop yield was measured and topsoil samples were collected at harvest of each crop season. BSA altered most of the soil physic-chemical properties with a significant increase over control in soil organic carbon (SOC) and available potassium (K) content. The increase in SOC and available K was consistent over the 5 crop seasons after BSA. Despite a significant yield increase in the first maize season, enhancement of crop yield was not consistent over crop seasons without corresponding to the changes in soil nutrient availability. BSA did not change seasonal total CO2 efflux but greatly reduced N2O emissions throughout the five seasons. This supported a stable nature of biochar carbon in soil, which played a consistent role in reducing N2O emission, which showed inter-annual variation with changes in temperature and soil moisture conditions. The biochar effect was much more consistent under C40 than under C20 and with

Pacing Behavior and Tactical Positioning in 500-and 1000-m Short-Track Speed Skating

NARCIS (Netherlands)

Noorbergen, Olaf S.; Konings, Marco J.; Micklewright, Dominic; Elferink-Gemser, Marge T.; Hettinga, Florentina J.

Purpose: To explore pacing behavior and tactical positioning during the shorter 500- and 1000-m short-track competitions. Methods: Lap times and intermediate rankings of elite 500- and 1000-m short-track-skating competitors were collected over the 2012-13 season. First, lap times were analyzed using

Seasonality in the Austrian Economy: Common Seasonals and Forecasting

OpenAIRE

Kunst, Robert M.

1992-01-01

Abstract: Seasonal cointegration generalizes the idea of cointegration to processes with unit roots at frequencies different from 0. Here, also the dual notion of common trends, "common seasonals", is adopted for the seasonal case. Using a five-variable macroeconomic core system of the Austrian economy, it is demonstrated how common seasonals and seasonal cointegrating vectors look in practice. Statistical tests provide clear evidence on seasonal cointegration in the system. However, it is sh...

High-Capacity Short-Range Optical Communication Links

DEFF Research Database (Denmark)

Tatarczak, Anna

Over the last decade, we have observed a tremendous spread of end-user mobile devices. The user base of a mobile application can grow or shrink by millions per day. This situation creates a pressing need for highly scalable server infrastructure; a need nowadays satisfied through cloud computing...... offered by data centers. As the popularity of cloud computing soars, the demand for high-speed, short-range data center links grows. Vertical cavity surface emitting lasers (VCSEL) and multimode fibers (MMF) prove especially well-suited for such scenarios. VCSELs have high modulation bandwidths......, we achieve 10 Gbps over 400 m and then conrm the approach in an optimized system at 25 Gbps over 300 m. The techniques described in this thesis leverage additional degrees of freedom to better utilize the available resources of short-range links. The proposed schemes enable higher speeds and longer...

Onion seedlings versus onion sets in organic onion production

OpenAIRE

Kivijärvi, Pirjo; Hannukkala, Asko; Haapalainen, Minna; Iivonen, Sari

2017-01-01

The objective of this study is to find onion varieties that are suitable for seedling cultivation and high-yielding in our relatively cool and short growing season. In addition, the yield quantity, quality and long-term storage durability of onions produced from either seedlings or sets are compared. Rot incidence and composition of pathogen populations in diseased onions is monitored during the growing season and long-term storage. The field experiments and on-farm trials will be carried out...

Enhanced precipitation promotes decomposition and soil C stabilization in semiarid ecosystems, but seasonal timing of wetting matters

Science.gov (United States)

Campos, Xochi; Germino, Matthew; de Graaff, Marie-Anne

2017-01-01

AimsChanging precipitation regimes in semiarid ecosystems will affect the balance of soil carbon (C) input and release, but the net effect on soil C storage is unclear. We asked how changes in the amount and timing of precipitation affect litter decomposition, and soil C stabilization in semiarid ecosystems.MethodsThe study took place at a long-term (18 years) ecohydrology experiment located in Idaho. Precipitation treatments consisted of a doubling of annual precipitation (+200 mm) added either in the cold-dormant season or in the growing season. Experimental plots were planted with big sagebrush (Artemisia tridentata), or with crested wheatgrass (Agropyron cristatum). We quantified decomposition of sagebrush leaf litter, and we assessed organic soil C (SOC) in aggregates, and silt and clay fractions.ResultsWe found that: (1) increased precipitation applied in the growing season consistently enhanced decomposition rates relative to the ambient treatment, and (2) precipitation applied in the dormant season enhanced soil C stabilization.ConclusionsThese data indicate that prolonged increases in precipitation can promote soil C storage in semiarid ecosystems, but only if these increases happen at times of the year when conditions allow for precipitation to promote plant C inputs rates to soil.

Growing season methane emission from a boreal peatland in the continuous permafrost zone of Northeast China: effects of active layer depth and vegetation

Directory of Open Access Journals (Sweden)

Y. Miao

2012-11-01

Full Text Available Boreal peatlands are significant natural sources of methane and especially vulnerable to abrupt climate change. However, the controlling factors of CH₄ emission in boreal peatlands are still unclear. In this study, we investigated CH₄ fluxes and abiotic factors (temperature, water table depth, active layer depth, and dissolved CH₄ concentrations in pore water during the growing seasons in 2010 and 2011 in both shrub-sphagnum- and sedge-dominated plant communities in the continuous permafrost zone of Northeast China. The objective of our study was to examine the effects of vegetation types and abiotic factors on CH₄ fluxes from a boreal peatland. In an Eriophorum-dominated community, mean CH₄ emissions were 1.02 and 0.80 mg m⁻² h⁻¹ in 2010 and 2011, respectively. CH₄ fluxes (0.38 mg m⁻² h⁻¹ released from the shrub-mosses-dominated community were lower than that from Eriophorum-dominated community. Moreover, in the Eriophorum-dominated community, CH₄ fluxes showed a significant temporal pattern with a peak value in late August in both 2010 and 2011. However, no distinct seasonal variation was observed in the CH₄ flux in the shrub-mosses-dominated community. Interestingly, in both Eriophorum- and shrub-sphagnum-dominated communities, CH₄ fluxes did not show close correlation with air or soil temperature and water table depth, whereas CH₄ emissions correlated well to active layer depth and CH₄ concentration in soil pore water, especially in the Eriophorum-dominated community. Our results suggest that CH₄ released from the thawed CH₄-rich permafrost layer may be a key factor controlling CH₄ emissions in boreal peatlands, and highlight that CH₄ fluxes vary with vegetation type in boreal peatlands. With

Evaporation components of a boreal forest: variations during the growing season

Science.gov (United States)

Grelle, A.; Lundberg, A.; Lindroth, A.; Morén, A.-S.; Cienciala, E.

1997-10-01

To improve the understanding of interactions between the boreal forest and the climate system as a key issue for global climate change, the water budget of a mixed pine and spruce forest in central Sweden was estimated by measurements of the water flux components and the total evaporation flux during the period 16 May-31 October 1995. Total evaporation was measured using eddy correlation and the components were obtained using measurements of precipitation, throughfall, tree transpiration, and forest floor evaporation. On a daily basis, tree transpiration was the dominant evaporation component during the vegetation period. However, it could be efficiently blocked by a wet canopy associated with large interception evaporation. The accumulated total evaporation was 399 mm, transpiration was 243 mm, forest floor evaporation was 56 mm and interception evaporation was 74 mm. The accumulated sum of interception, transpiration, and floor evaporation was 51 mm larger than the actual measured total evaporation. This difference was mainly attributed to the fact that transpiration was measured in a rather dense 50-year-old stand while total evaporation represented the average conditions of older, roughly 100-year-old stands. To compare eddy-correlation measurements with small-scale measurements of evaporation components, a source area analysis was made to select the flux data that give the best representation of the investigated stand. Especially under stable atmospheric conditions the requirements for surface homogeneity were very high and extreme care had to be taken to be aware of the flux source areas. Canopy water storage was determined by two methods: by the water balance of the canopy, which gave a result of 3.3 mm; and by the so-called minimum method based on plots of throughfall versus precipitation, which gave a much lower value of 1.5 mm. Seasonal interception evaporation constituted 30% of the precipitation.

Frosts during the growing season. Frequency of occurrence and effects on current energy forestry. Sommarfroster. Foerekomster och effekter paa befintliga energiskogsodlingar

Energy Technology Data Exchange (ETDEWEB)

Christersson, L; Fircks, H von; Perttu, K

1984-01-01

Frost during the summer is very common in Sweden. Two kinds of summer frosts exists; one is called advection frost which is caused by cold air coming down over the country from the north and the other is an inversion frost caused by long-wave radiation from the ground taking place during calm clear nights. In this way the air closest to the ground is cooled. Eleven experimental areas are described as regards prehistory, vegetation, frequency of summer frosts, and energy forestry tests in progress. The amount of frost injuries is reported. Differences in frost hardiness of fast growing Salix clones in the growing state have been demonstrated. The results support the idea that the formation of ice crystals inside the growing tissues always take place around -2 degree C and that this ice crystal formation damages the growing part of the shoot of all tested clones. A fast growing shoot of Salix species has a longer elongation zone and this explains why a fast-growing shoot is more severly damaged than a slowly growing one at the same frost temperature. If the different clones are in a growing state there are only small differences in the amount of frost damage. On the other hand, there are great differences between the clones in the capacity of the surviving lateral buds to sprout. This capacity is foremost seen in clones of the species Salix dasyclados. Two year older shoots of different Salix species have never been damaged by summer frost because summer frosts do not reach the elongating zone of these shoots. In conclusions measures are listed on how to prevent or decrease the injuries caused by summer frosts. With 21 refs.

Seasonal pattern of metal bioaccumulation and their toxicity on Sphagnum squarrosum.

Science.gov (United States)

Saxena, Anuj

2006-01-01

Present study was undertaken as an attempt to study the effect of pollutants on biological responses of Sphagnum growing at Kainchi, Kumaon hills (Uttranchal). Sphagnum plants of almost identical size, collected from the marked sites of Kainchi in different seasons viz., monsoon, winter, summer and again in monsoon, were analysed for chlorophyll, protein, shoot length and nitrate reductase and peroxidase activities. Maximum chlorophyll, protein, shoots length and nitrate reductase activities were observed during the monsoon while minimum in summers. The abundance of Sphagnum and two other bryophytes, Marchantia and Plagiochasma was also higher in monsoon than in other seasons. The study also indicated that Sphagnum has more bioaccumulation and tolerance potential for heavy metals than Marchantia and Plagiochasma.

Seasonal climate change patterns due to cumulative CO2 emissions

Science.gov (United States)

Partanen, Antti-Ilari; Leduc, Martin; Damon Matthews, H.

2017-07-01

Cumulative CO2 emissions are near linearly related to both global and regional changes in annual-mean surface temperature. These relationships are known as the transient climate response to cumulative CO2 emissions (TCRE) and the regional TCRE (RTCRE), and have been shown to remain approximately constant over a wide range of cumulative emissions. Here, we assessed how well this relationship holds for seasonal patterns of temperature change, as well as for annual-mean and seasonal precipitation patterns. We analyzed an idealized scenario with CO2 concentration growing at an annual rate of 1% using data from 12 Earth system models from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Seasonal RTCRE values for temperature varied considerably, with the highest seasonal variation evident in the Arctic, where RTCRE was about 5.5 °C per Tt C for boreal winter and about 2.0 °C per Tt C for boreal summer. Also the precipitation response in the Arctic during boreal winter was stronger than during other seasons. We found that emission-normalized seasonal patterns of temperature change were relatively robust with respect to time, though they were sub-linear with respect to emissions particularly near the Arctic. Moreover, RTCRE patterns for precipitation could not be quantified robustly due to the large internal variability of precipitation. Our results suggest that cumulative CO2 emissions are a useful metric to predict regional and seasonal changes in precipitation and temperature. This extension of the TCRE framework to seasonal and regional climate change is helpful for communicating the link between emissions and climate change to policy-makers and the general public, and is well-suited for impact studies that could make use of estimated regional-scale climate changes that are consistent with the carbon budgets associated with global temperature targets.

Seasonal changes in physiological performance in wild Clarkia xantiana populations: Implications for the evolution of a compressed life cycle and self-fertilization.

Science.gov (United States)

Dudley, Leah S; Hove, Alisa A; Emms, Simon K; Verhoeven, Amy S; Mazer, Susan J

2015-06-01

One explanation for the evolution of selfing, the drought escape hypothesis, proposes that self-fertilization may evolve under conditions of intensifying seasonal drought as part of a suite of traits that enable plants to accelerate the completion of their life cycle, thereby escaping late-season drought. Here, we test two fundamental assumptions of this hypothesis in Clarkia xantiana: (1) that a seasonal decline in precipitation causes an increase in drought stress and (2) that this results in changes in physiological performance, reflecting these deteriorating conditions. We examined seasonal and interannual variation in abiotic environmental conditions (estimated by ambient temperature, relative humidity, predawn leaf water potentials, and carbon isotope ratios) and physiological traits (photosynthesis, conductance, transpiration, instantaneous water-use efficiency, ascorbate peroxidase and glutathione reductase activities, quantum yield of photosystem II, PSII potential efficiency) in field populations of C. xantiana in 2009 and 2010. In both years, plants experienced intensifying drought across the growing season. Gas exchange rates decreased over the growing season and were lower in 2009 (a relatively dry year) than in 2010, suggesting that the temporal changes from early to late spring were directly linked to the deteriorating environmental conditions. Seasonal declines in transpiration rate may have increased survival by protecting plants from desiccation. Concomitant declines in photosynthetic rate likely reduced the availability of resources for seed production late in the season. Thus, the physiological patterns observed are consistent with the conditions required for the drought escape hypothesis. © 2015 Botanical Society of America, Inc.

Analysis of seasonal, diurnal, and noctural growth patterns of young longleaf pine

Science.gov (United States)

John C. Gilbert; Ralph S. Meldahl; John S. Kush; William D. Boyer

2006-01-01

Forty longleaf pine (Pinus palustris Mill.) trees initially ranging from 1 to 1.5 m in height were measured on the Escambia Experimental Forest from 1969 through 1980. The trees were evenly divided between two soil types. From 1969 through 1970, height and diameter measurements were recorded one to four times weekly during the growing seasons and...

Feeding season duration and the relative success of capital and income spawning copepods

DEFF Research Database (Denmark)

Sainmont, Julie; Varpe, Øystein; Andersen, Ken Haste

to the spring bloom, using only its reserves accumulated the previous year (capital breeder). The success of these two strategies is related to the length of the spring bloom, the only source of nutrients for these copepods. We use an individual based model to approach the question of income versus capital...... breeders in a highly seasonal environment, and find that the capital breeders have a higher fitness during short spring bloom while the income breeder has an improved performance over long productive seasons...

Metaphyseal pattern: Uniqueness of this structure in growing bones originating from cartilaginous anlage

International Nuclear Information System (INIS)

Balmain, N.; Moscofian, A.; Cuisinier-Gleizes, P.

1983-01-01

Microradiographic examination of metaphyses in long and short tubular growing bones allowed detection of a repetitive, clearly defined pattern of three adjacent zones; the latter are successively formed by the mineralization of cartilaginous longitudinal intercolumnar septa and by the subsequent apposition of other mineralized tissues concurrently with resorption. Consequently, each zone of the metaphysis includes mineralized tissues of various compositions and ages, identifiable by their different mineralization densities. Microradiography of pieces of the growing skeleton in several animal species shows that the same organization is not only present in long and short tubular bones but also in many other such as the pelvis and scapula, cuboid bones like the calcaneum and talus, and cartilaginous bones at the base of the skull. This suggests that there is no difference between the osteogenesis pattern of these bones and tubular ones. The problem of identifying the factors generating such metaphyseal organization is raised. (orig.)

Peripheral kisspeptin reverses short photoperiod-induced gonadal regression in Syrian hamsters by promoting GNRH release

DEFF Research Database (Denmark)

Ansel, L; Bentsen, A H; Ancel, C

2011-01-01

In seasonal breeders, reproduction is synchronised by day length via the pineal hormone melatonin. In short winter days (short day, SD), the Syrian hamster displays a complete gonadal atrophy together with a marked reduction in expression of kisspeptins (Kp), a family of potent hypothalamic stimu...

Effect of season on the quality of forages selected by sheep in citrus plantations in Ghana

Directory of Open Access Journals (Sweden)

Leonard K. Adjorlolo

2014-09-01

Full Text Available The study aimed at assessing the effects of season on chemical composition of forages selected by sheep grazing in a citrus plantation. Forage species growing in a sweet orange (Citrus sinensis plantation were identified and sampled monthly for 2 years. Samples were bulked on monthly basis for chemical analysis. The average dry matter content of the forages increased from the rainy to the dry season but effects of season on the chemical components were inconsistent. Some species, such as Asystasia gangetica, had a higher crude protein concentration in the dry season, whereas for others, such as Panicum repens, the reverse occurred. However, average concentrations of crude protein, detergent fiber and components of fiber for all species for the rainy season were not significantly different from the dry season values. It was concluded that there were differences among forage species in their responses to changing seasons, such that grazing ruminants may select a diet to enable them to meet their nutritional requirements, provided forage biomass is adequate.Keywords: Crop-livestock integration, tree plantations, chemical composition, seasonal effects, forage quality.DOI: 10.17138/TGFT(2271-277

Introducing seasonal hydro-meteorological forecasts in local water management. First reflections from the Messara site, Crete, Greece.

Science.gov (United States)

Koutroulis, Aristeidis; Grillakis, Manolis; Tsanis, Ioannis

2017-04-01

Seasonal prediction is recently at the center of the forecasting research efforts, especially for regions that are projected to be severely affected by global warming. The value of skillful seasonal forecasts can be considerable for many sectors and especially for the agricultural in which water users and managers can benefit to better anticipate against drought conditions. Here we present the first reflections from the user/stakeholder interactions and the design of a tailored drought decision support system in an attempt to bring seasonal predictions into local practice for the Messara valley located in the central-south area of Crete, Greece. Findings from interactions with the users and stakeholders reveal that although long range and seasonal predictions are not used, there is a strong interest for this type of information. The increase in the skill of short range weather predictions is also of great interest. The drought monitoring and prediction tool under development that support local water and agricultural management will include (a) sources of skillful short to medium term forecast information, (b) tailored drought monitoring and forecasting indices for the local groundwater aquifer and rain-fed agriculture, and (c) seasonal inflow forecasts for the local dam through hydrologic simulation to support management of freshwater resources and drought impacts on irrigated agriculture.

Airborne Thermal Imagery to Detect the Seasonal Evolution of Crop Water Status in Peach, Nectarine and Saturn Peach Orchards

Directory of Open Access Journals (Sweden)

Joaquim Bellvert

2016-01-01

Full Text Available In the current scenario of worldwide limited water supplies, conserving water is a major concern in agricultural areas. Characterizing within-orchard spatial heterogeneity in water requirements would assist in improving irrigation water use efficiency and conserve water. The crop water stress index (CWSI has been successfully used as a crop water status indicator in several fruit tree species. In this study, the CWSI was developed in three Prunus persica L. cultivars at different phenological stages of the 2012 to 2014 growing seasons, using canopy temperature measurements of well-watered trees. The CWSI was then remotely estimated using high-resolution thermal imagery acquired from an airborne platform and related to leaf water potential (ѰL throughout the season. The feasibility of mapping within-orchard spatial variability of ѰL from thermal imagery was also explored. Results indicated that CWSI can be calculated using a common non-water-stressed baseline (NWSB, upper and lower limits for the entire growing season and for the three studied cultivars. Nevertheless, a phenological effect was detected in the CWSI vs. ѰL relationships. For a specific given CWSI value, ѰL was more negative as the crop developed. This different seasonal response followed the same trend for the three studied cultivars. The approach presented in this study demonstrated that CWSI is a feasible method to assess the spatial variability of tree water status in heterogeneous orchards, and to derive ѰL maps throughout a complete growing season. A sensitivity analysis of varying pixel size showed that a pixel size of 0.8 m or less was needed for precise ѰL mapping of peach and nectarine orchards with a tree crown area between 3.0 to 5.0 m2.

Preliminary observations on the species composition and ...

African Journals Online (AJOL)

Majority of the mushrooms appear during the rain season and are equally available during the short and long rains. This suggests that most species will grow well throughout the year whenever moisture level in the substrate is adequate irrespective of the season. Some of the species especially the Polypores (Ganoderma ...

Seasonal carbon storage and growth in Mediterranean tree seedlings under different water conditions.

Science.gov (United States)

Sanz-Pérez, Virginia; Castro-Díez, Pilar; Joffre, Richard

2009-09-01

In all Mediterranean-type ecosystems, evergreen and deciduous trees differing in wood anatomy, growth pattern and leaf habit coexist, suggesting distinct adaptative responses to environmental constraints. This study examined the effects of summer water stress on carbon (C) storage and growth in seedlings of three coexisting Mediterranean trees that differed in phenology and wood anatomy characteristics: Quercus ilex subsp. ballota (Desf.) Samp., Quercus faginea Lam. and Pinus halepensis L. Seedlings were subjected to two levels of watering during two consecutive summers and achieved a minimum of -0.5 and -2.5 MPa of predawn water potential in the control and water stress treatment, respectively. Both Quercus species concentrated their growth in the early growing season, demanding higher C in early spring but replenishing C-stores in autumn. These species allocated more biomass to roots, having larger belowground starch and lipid reserves. Quercus species differed in seasonal storage dynamics from P. halepensis. This species allocated most of its C to aboveground growth, which occurred gradually during the growing season, leading to fewer C-reserves. Soluble sugar and starch concentrations sharply declined in August in P. halepensis, probably because reserves support respiration demands as this species closed stomata earlier under water stress. Drought reduced growth of the three species, mainly in Q. faginea and P. halepensis, but not C-reserves, suggesting that growth under water stress conditions is not limited by C-availability.

A growing threat to the ozone layer from short-lived anthropogenic chlorocarbons

Directory of Open Access Journals (Sweden)

D. E. Oram

2017-10-01

Full Text Available Large and effective reductions in emissions of long-lived ozone-depleting substance (ODS are being achieved through the Montreal Protocol, the effectiveness of which can be seen in the declining atmospheric abundances of many ODSs. An important remaining uncertainty concerns the role of very short-lived substances (VSLSs which, owing to their relatively short atmospheric lifetimes (less than 6 months, are not regulated under the Montreal Protocol. Recent studies have found an unexplained increase in the global tropospheric abundance of one VSLS, dichloromethane (CH2Cl2, which has increased by around 60 % over the past decade. Here we report dramatic enhancements of several chlorine-containing VSLSs (Cl-VSLSs, including CH2Cl2 and CH2ClCH2Cl (1,2-dichloroethane, observed in surface and upper-tropospheric air in East and South East Asia. Surface observations were, on occasion, an order of magnitude higher than previously reported in the marine boundary layer, whilst upper-tropospheric data were up to 3 times higher than expected. In addition, we provide further evidence of an atmospheric transport mechanism whereby substantial amounts of industrial pollution from East Asia, including these chlorinated VSLSs, can rapidly, and regularly, be transported to tropical regions of the western Pacific and subsequently uplifted to the tropical upper troposphere. This latter region is a major provider of air entering the stratosphere, and so this mechanism, in conjunction with increasing emissions of Cl-VSLSs from East Asia, could potentially slow the expected recovery of stratospheric ozone.

Chlorophyll fluorescence tracks seasonal variations of photosynthesis from leaf to canopy in a temperate forest.

Science.gov (United States)

Yang, Hualei; Yang, Xi; Zhang, Yongguang; Heskel, Mary A; Lu, Xiaoliang; Munger, J William; Sun, Shucun; Tang, Jianwu

2017-07-01

Accurate estimation of terrestrial gross primary productivity (GPP) remains a challenge despite its importance in the global carbon cycle. Chlorophyll fluorescence (ChlF) has been recently adopted to understand photosynthesis and its response to the environment, particularly with remote sensing data. However, it remains unclear how ChlF and photosynthesis are linked at different spatial scales across the growing season. We examined seasonal relationships between ChlF and photosynthesis at the leaf, canopy, and ecosystem scales and explored how leaf-level ChlF was linked with canopy-scale solar-induced chlorophyll fluorescence (SIF) in a temperate deciduous forest at Harvard Forest, Massachusetts, USA. Our results show that ChlF captured the seasonal variations of photosynthesis with significant linear relationships between ChlF and photosynthesis across the growing season over different spatial scales (R 2  = 0.73, 0.77, and 0.86 at leaf, canopy, and satellite scales, respectively; P chlorophyll content (R 2  = 0.65 for canopy GPP SIF and chlorophyll content; P < 0.0001), leaf area index (LAI) (R 2  = 0.35 for canopy GPP SIF and LAI; P < 0.0001), and normalized difference vegetation index (NDVI) (R 2  = 0.36 for canopy GPP SIF and NDVI; P < 0.0001). Our results suggest that ChlF can be a powerful tool to track photosynthetic rates at leaf, canopy, and ecosystem scales. © 2016 John Wiley & Sons Ltd.

Global Trends in Seasonality of Normalized Difference Vegetation Index (NDVI, 1982–2011

Directory of Open Access Journals (Sweden)

Assaf Anyamba

2013-09-01

Full Text Available A 30-year series of global monthly Normalized Difference Vegetation Index (NDVI imagery derived from the Global Inventory Modeling and Mapping Studies (GIMMS NDVI3g archive was analyzed for the presence of trends in changing seasonality. Using the Seasonal Trend Analysis (STA procedure, over half (56.30% of land surfaces were found to exhibit significant trends. Almost half (46.10% of the significant trends belonged to three classes of seasonal trends (or changes. Class 1 consisted of areas that experienced a uniform increase in NDVI throughout the year, and was primarily associated with forested areas, particularly broadleaf forests. Class 2 consisted of areas experiencing an increase in the amplitude of the annual seasonal signal whereby increases in NDVI in the green season were balanced by decreases in the brown season. These areas were found primarily in grassland and shrubland regions. Class 3 was found primarily in the Taiga and Tundra biomes and exhibited increases in the annual summer peak in NDVI. While no single attribution of cause could be determined for each of these classes, it was evident that they are primarily found in natural areas (as opposed to anthropogenic land cover conversions and that they are consistent with climate-related ameliorations of growing conditions during the study period.

Soil emissions of nitric oxide in a seasonally dry tropical forest of Mexico

Science.gov (United States)

Davidson, Eric A.; Vitousek, Peter M.; Riley, Ralph; Matson, Pamela A.; Garcia-Mendez, Georgina; Maass, J. M.

1991-01-01

Soil emissions of NO were measured at the Chamela Biological Station, Mexico, using soil covers and a field apparatus of NO detection based on CrO3 conversion of NO to NO2 and detection of NO2 by chemiluminescence with Luminol. Mean NO fluxes from forest soils ranged from 0.14 to 0.52 ng NO-N/sq cm/hr during the dry season and from 0.73 to 1.27 ng NO-N/sq cm/hr during the wet season. A fertilized floodplain pasture exhibited higher fluxes, but an unfertilized upland pasture, which represents the fastest growing land use in the region, had flux rates similar to the forest sites. Wetting experiments at the end of the dry season caused large pulses of NO flux, equaling 10 percent to 20 percent of the estimated annual NO emissions of 0.5-1.0 kg N/ha from the forest sites. Absence of a forest canopy during the dry season and the first wet season rain probably results in substantial NO(x) export from the forest system that may be important to regional atmospheric chemical processes. Wetting experiments during the wet season and a natural rain event had little or no stimulatory effect on NO flux rates.

Heterothermy in growing king penguins.

Science.gov (United States)

Eichhorn, Götz; Groscolas, René; Le Glaunec, Gaële; Parisel, Camille; Arnold, Laurent; Medina, Patrice; Handrich, Yves

2011-08-16

A drop in body temperature allows significant energy savings in endotherms, but facultative heterothermy is usually restricted to small animals. Here we report that king penguin chicks (Aptenodytes patagonicus), which are able to fast for up to 5 months in winter, undergo marked seasonal heterothermy during this period of general food scarcity and slow-down of growth. They also experience short-term heterothermy below 20 °C in the lower abdomen during the intense (re)feeding period in spring, induced by cold meals and adverse weather. The heterothermic response involves reductions in peripheral temperature, reductions in thermal core volume and temporal abandonment of high core temperature. Among climate variables, air temperature and wind speed show the strongest effect on body temperature, but their effect size depends on physiological state. The observed heterothermy is remarkable for such a large bird (10 kg before fasting), which may account for its unrivalled fasting capacity among birds.

Kisspeptins and RFRP-3 act in concert to synchronize rodent reproduction with seasons

Directory of Open Access Journals (Sweden)

Valerie eSimonneaux

2013-02-01

Full Text Available Seasonal mammals use the photoperiodic variation in the nocturnal production of the pineal hormone melatonin to synchronize their reproductive activity with seasons. In rodents, the short day profile of melatonin secretion has long been proven to inhibit reproductive activity. Lately, we demonstrated that melatonin regulates the expression of the hypothalamic peptides kisspeptins (Kp and RFamide-related peptide-3 (RFRP-3, recently discovered as potent regulators of GnRH neuron activity. In the male Syrian hamster, Kp expression in the arcuate nucleus is down-regulated by melatonin independently of the inhibitory feedback of testosterone. A central or peripheral administration of Kp induces an increase in pituitary gonadotropins and gonadal hormone secretion, but most importantly a chronic infusion of the peptide reactivates the photoinhibited reproductive axis of Syrian hamsters kept in short day conditions. RFRP-3 expression in the dorsomedial hypothalamus is also strongly inhibited by melatonin in a short day photoperiod. Although RFRP-3 is usually considered as an inhibitory component of the gonadotropic axis, a central acute administration of RFRP-3 in the male Syrian hamster induces a marked increase in gonadotropin secretion and testosterone production. Furthermore, a chronic central infusion of RFRP-3 in short day-adapted hamsters reactivates the reproductive axis, in the same manner as Kp. Both Kp and RFRP-3 neurons project onto GnRH neurons and both neuropeptides regulate GnRH neuron activity. In addition, central RFRP-3 infusion was associated with a significant increase in arcuate Kp expression. However, the actual sites of action of both peptides in the Syrian hamster brain are still unknown. Altogether our findings indicate that Kp and RFRP neurons are pivotal relays for the seasonal regulation of reproduction, and also suggest that RFRP neurons might be the primary target of the melatoninergic message.

Seasonal Climate Signals in Multiple Tree-Ring Parameters: A Pilot Study of Pinus ponderosa in the Columbia River Basin

Science.gov (United States)

Dannenberg, M.; Wise, E. K.; Keung, J. H.

2014-12-01

Proxy-based reconstructions of past climate have played an integral role in assessments of historical climate change, and tree-ring widths (TRW) have a long history of use in this paleoclimate research due to their annual resolution, widespread availability, and sensitivity of growth processes to variation in temperature and water availability. Increasingly, studies have shown that additional tree-ring metrics—including earlywood and latewood widths (EW and LW, respectively), maximum latewood density, and the intensity of reflected blue light from latewood (BI)—can provide additional information on seasonal climatic variability that is not present in TRW alone due to different processes that affect growth in different parts of the growing season. Studies of these additional tree-ring metrics highlight their utility in climate reconstructions, but to date they have mostly been limited to a few tree species and regions. Here, we extend the range of previous studies on alternative tree-ring metrics by evaluating the seasonal climate signals in TRW, EW, LW, and BI of Pinus ponderosa at six semiarid sites surrounding the Columbia River basin in the U.S. Pacific Northwest (PNW). Cores from each site were cross-dated and EW, LW, and TRW were measured using standard dendrochronological procedures. BI was obtained using a high-resolution flatbed scanner and CooRecorder software. To evaluate the unique climate processes and seasonalities contributing to different dendrochronological metrics, monthly temperature and precipitation from each site were obtained from the PRISM climate model and were correlated with each of the tree-ring metrics using the MATLAB program SEASCORR. We also evaluate the potential of using multiple tree-ring metrics (rather than a single proxy) in reconstructions of precipitation in the PNW. Initial results suggest that 1) tree growth at each site is water-limited but with substantial differences among the sites in the strength and seasonality of

Seasonal variation of solar radiation and underwater irradiance in the Seto inland sea

International Nuclear Information System (INIS)

Endo, T.; Matsuda, O.; Imabayashi, H.

1983-01-01

The recent rapid eutrophication of the coastal seas of Japan has had a remarkable effect on the turbidity and transparency of the sea water, hence on the attenuation of underwater irradiance, which in turn influences the phytoplankton communities and primary productivity of the area. The present study deals with the continuous three years observation of the total short-wave radiation, direct short-wave radiation, diffused short-wave radiation and photosynthetically active radiation of tlle Seto Inland Sea. Along with these observations, reflected short-wave radiation from the sea and transmitted short-wave radiation into the sea were determined. The availability of solar radiation for primary production, vertical distribution of spectral irradiance and attenuation coefficient were also discussed in relation to the optical water type of the region. 1. A typical seasonal variation in the monthly mean daily solar radiation (total short-wave radiation) was observed, with a maximal value of 17.0 MJ 2 in July and minimal values of 7.4 to 7.5 MJ 2 through November to January. 2. Seasonal variation of direct short-wave radiation was nearly identical to that of total short-wave radiation, with 9.3 MJ 2 at maximum and 4.1MJ 2 at minimum. Diffused short-wave radiation increased in June and decreased in January. The ratio of diffused short-wave radiation to total short-wave radiation ranged from 394000 62% with an average of 49%.0 3. Seasonal variation of photosynthetically active radiation was very similar to that of direct short-wave radiation, with values of 7.3 MJ 2 in July and of 3.3 MJ 2 in December 4. The albedo at the sea surface changed according to the incidence angle and surface conditions. Average daily values ranged from 2.9% on a fine summer day to 10% on an overcasted day in winter. 5. Underwater irradiance at a depth of 50cm varied widely according to such parameters as turbidity and the surface condition of the water. Observation revealed a remarkable decrease

FORWINE - Statistical Downscaling of Seasonal forecasts for wine

Science.gov (United States)

Cardoso, Rita M.; Soares, Pedro M. M.; Miranda, Pedro M. A.

2016-04-01

The most renowned viticulture regions in the Iberian Peninsula have a long standing tradition in winemaking and are considered world-class grapevine (Vitis Vinifera L.) producing regions. Portugal is the 11th wine producer in the world, with internationally acclaimed wines, such as Port wine, and vineyards across the whole territory. Climate is widely acknowledged of one of the most important factors for grapevine development and growth (Fraga et al. 2014a and b; Jackson et al. 1993; Keller 2010). During the growing season (April-October in the Northern Hemisphere) of this perennial and deciduous crop, the climatic conditions are responsible for numerous morphologically and physiological changes. Anomalously low February-March mean temperature, anomalously high May mean temperature and anomalously high March precipitation tend to be favourable to wine production in the Douro Valley. Seasonal forecast of precipitation and temperature tailored to fit critical thresholds, for crucial seasons, can be used to inform management practices (viz. phytosanitary measures, land operations, marketing campaigns) and develop a wine production forecast. Statistical downscaling of precipitation, maximum, minimum temperatures is used to model wine production following Santos et al. (2013) and to calculate bioclimatic indices. The skill of the ensemble forecast is evaluated through anomaly correlation, ROC area, spread-error ratio and CRPS

Seasonal and Interannual Trends in Largest Cholera Endemic Megacity: Water Sustainability - Climate - Health Challenges in Dhaka, Bangladesh

Science.gov (United States)

Akanda, Ali S.; Jutla, Antarpreet; Faruque, Abu S. G.; Huq, Anwar; Colwell, Rita R.

2014-05-01

The last three decades of surveillance data shows a drastic increase of cholera prevalence in the largest cholera-endemic city in the world - Dhaka, Bangladesh. Emerging megacities in the region, especially those located in coastal areas also remain vulnerable to large scale drivers of cholera outbreaks. However, there has not been any systematic study on linking long-term disease trends with related changes in natural or societal variables. Here, we analyze the 30-year dynamics of urban cholera prevalence in Dhaka with changes in climatic or anthropogenic forcings: regional hydrology, flooding, water usage, changes in distribution systems, population growth and density in urban settlements, as well as shifting climate patterns and frequency of natural disasters. An interesting change is observed in the seasonal trends of cholera prevalence; while an endemic upward trend is seen in the dry season, the post-monsoon trend is epidemic in nature. In addition, the trend in the pre-monsoon dry season is significantly stronger than the post-monsoon wet season; and thus spring is becoming the dominant cholera season of the year. Evidence points to growing urbanization and rising population in unplanned settlements along the city peripheries. The rapid pressure of growth has led to an unsustainable and potentially disastrous situation with negligible-to-poor water and sanitation systems compounded by changing climatic patterns and increasing number of extreme weather events. Growing water scarcity in the dry season and lack of sustainable water and sanitation infrastructure for urban settlements have increased endemicity of cholera outbreaks in spring, while record flood events and prolonged post-monsoon inundation have contributed to increased epidemic outbreaks in fall. We analyze our findings with the World Health Organization recommended guidelines and investigate large scale water sustainability challenges in the context of climatic and anthropogenic changes in the

Short-term effects of simultaneous cardiovascular workout and ...

African Journals Online (AJOL)

PMD), has become a growing public health concern, as it may potentially result in the development of hearing difficulties. Objectives: The aim of the study was to determine the differential impact and short-term effects of simultaneous ...

Seasonal temperatures have more influence than nitrogen fertilizer rates on cucumber yield and nitrogen uptake in a double cropping system

Energy Technology Data Exchange (ETDEWEB)

Guo Ruiying; Li Xiaolin [College of Resources and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan Xilu, Haidian District, Beijing 100094 (China); Christie, Peter [College of Resources and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan Xilu, Haidian District, Beijing 100094 (China); Agricultural and Environmental Science Department, Queen' s University Belfast, Belfast BT9 5PX (United Kingdom); Chen Qing [College of Resources and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan Xilu, Haidian District, Beijing 100094 (China)], E-mail: qchen@cau.edu.cn; Zhang Fusuo [College of Resources and Environmental Sciences, China Agricultural University, No. 2 Yuanmingyuan Xilu, Haidian District, Beijing 100094 (China)

2008-02-15

Two-year greenhouse cucumber experiments were conducted to investigate seasonal effects on fruit yield, dry matter allocation, and N uptake in a double-cropping system with different fertilizer management. Seasonal effects were much greater than fertilizer effects, and winter-spring (WS) cucumber attained higher fruit yields and N uptake than autumn-winter (AW) cucumber due to lower cumulative air temperatures during fruit maturation in the AW season. Fertilizer N application and apparent N loss under recommended N management (Nmr) decreased by 40-78% and 33-48% without yield loss compared to conventional N management (Nmt) over four growing seasons. However, there were no seasonal differences in N recommendations, taking into consideration seasonal differences in crop N demand, critical nutrient supply in the root zone and N mineralization rate. - Nitrogen inputs can be reduced to minimize N losses to the environment while maintaining yields but N recommendations must reflect seasonal temperature effects.

Seasonal temperatures have more influence than nitrogen fertilizer rates on cucumber yield and nitrogen uptake in a double cropping system

International Nuclear Information System (INIS)

Guo Ruiying; Li Xiaolin; Christie, Peter; Chen Qing; Zhang Fusuo

2008-01-01

Two-year greenhouse cucumber experiments were conducted to investigate seasonal effects on fruit yield, dry matter allocation, and N uptake in a double-cropping system with different fertilizer management. Seasonal effects were much greater than fertilizer effects, and winter-spring (WS) cucumber attained higher fruit yields and N uptake than autumn-winter (AW) cucumber due to lower cumulative air temperatures during fruit maturation in the AW season. Fertilizer N application and apparent N loss under recommended N management (Nmr) decreased by 40-78% and 33-48% without yield loss compared to conventional N management (Nmt) over four growing seasons. However, there were no seasonal differences in N recommendations, taking into consideration seasonal differences in crop N demand, critical nutrient supply in the root zone and N mineralization rate. - Nitrogen inputs can be reduced to minimize N losses to the environment while maintaining yields but N recommendations must reflect seasonal temperature effects

Seasonal nutrient yield and digestibility of deer forage from a young pine plantation

Science.gov (United States)

Robert M. Blair; Henry L. Short; E.A. Epps

1977-01-01

Six classes of current herbaceous and woody forage were collected seasonally from a 5-year-old mixed loblolly (Pinus taeda)-shortleaf pine (Pinus echinata) plantation (in Texas) and subjected to nutrient analyses and nylon bag dry-matter digestion trials. Forages were most nutritious and digestible in the spring when tissues were succulent and growing rapidly. Browse...

Development, Validation, and Interlaboratory Evaluation of a Quantitative Multiplexing Method To Assess Levels of Ten Endogenous Allergens in Soybean Seed and Its Application to Field Trials Spanning Three Growing Seasons.

Science.gov (United States)

Hill, Ryan C; Oman, Trent J; Wang, Xiujuan; Shan, Guomin; Schafer, Barry; Herman, Rod A; Tobias, Rowel; Shippar, Jeff; Malayappan, Bhaskar; Sheng, Li; Xu, Austin; Bradshaw, Jason

2017-07-12

As part of the regulatory approval process in Europe, comparison of endogenous soybean allergen levels between genetically engineered (GE) and non-GE plants has been requested. A quantitative multiplex analytical method using tandem mass spectrometry was developed and validated to measure 10 potential soybean allergens from soybean seed. The analytical method was implemented at six laboratories to demonstrate the robustness of the method and further applied to three soybean field studies across multiple growing seasons (including 21 non-GE soybean varieties) to assess the natural variation of allergen levels. The results show environmental factors contribute more than genetic factors to the large variation in allergen abundance (2- to 50-fold between environmental replicates) as well as a large contribution of Gly m 5 and Gly m 6 to the total allergen profile, calling into question the scientific rational for measurement of endogenous allergen levels between GE and non-GE varieties in the safety assessment.

Grow, Baby, Grow

Science.gov (United States)

Maybe you quit smoking during your pregnancy. Or maybe you struggled and weren’t able to stay quit. Now that your baby is here, trying to stay away from smoking is still important. That’s because the chemicals in smoke can make it harder for your baby to grow like he or she should.

Changes in photosynthesis and soil moisture drive the seasonal soil respiration-temperature hysteresis relationship

Science.gov (United States)

Quan Zhang; Richard P. Phillips; Stefano Manzoni; Russell L. Scott; A. Christopher Oishi; Adrien Finzi; Edoardo Daly; Rodrigo Vargas; Kimberly A. Novick

2018-01-01

In nearly all large-scale terrestrial ecosystem models, soil respiration is represented as a function of soil temperature. However, the relationship between soil respiration and soil temperature is highly variable across sites and there is often a pronounced hysteresis in the soil respiration-temperature relationship over the course of the growing season. This...

Analysing environmental and fishing effects on a short-lived species ...

African Journals Online (AJOL)

Short-lived species are extremely dependent on the seasonal and interannual variability of environmental conditions, and determining their stock status is often difficult. This study investigates the effects of environmental variability and fishing pressure on the stock of octopus Octopus vulgaris in Senegalese waters over a ...

Environmental Growing Conditions in Five Production Systems Induce Stress Response and Affect Chemical Composition of Cocoa (Theobroma cacao L.) Beans.

Science.gov (United States)

Niether, Wiebke; Smit, Inga; Armengot, Laura; Schneider, Monika; Gerold, Gerhard; Pawelzik, Elke

2017-11-29

Cocoa beans are produced all across the humid tropics under different environmental conditions provided by the region but also by the season and the type of production system. Agroforestry systems compared to monocultures buffer climate extremes and therefore provide a less stressful environment for the understory cocoa, especially under seasonally varying conditions. We measured the element concentration as well as abiotic stress indicators (polyamines and total phenolic content) in beans derived from five different production systems comparing monocultures and agroforestry systems and from two harvesting seasons. Concentrations of N, Mg, S, Fe, Mn, Na, and Zn were higher in beans produced in agroforestry systems with high stem density and leaf area index. In the dry season, the N, Fe, and Cu concentration of the beans increased. The total phenolic content increased with proceeding of the dry season while other abiotic stress indicators like spermine decreased, implying an effect of the water availability on the chemical composition of the beans. Agroforestry systems did not buffer the variability of stress indicators over the seasons compared to monocultures. The effect of environmental growing conditions on bean chemical composition was not strong but can contribute to variations in cocoa bean quality.

Evaluating Downscaling Methods for Seasonal Climate Forecasts over East Africa

Science.gov (United States)

Roberts, J. Brent; Robertson, Franklin R.; Bosilovich, Michael; Lyon, Bradfield; Funk, Chris

2013-01-01

The U.S. National Multi-Model Ensemble seasonal forecasting system is providing hindcast and real-time data streams to be used in assessing and improving seasonal predictive capacity. The NASA / USAID SERVIR project, which leverages satellite and modeling-based resources for environmental decision making in developing nations, is focusing on the evaluation of NMME forecasts specifically for use in impact modeling within hub regions including East Africa, the Hindu Kush-Himalayan (HKH) region and Mesoamerica. One of the participating models in NMME is the NASA Goddard Earth Observing System (GEOS5). This work will present an intercomparison of downscaling methods using the GEOS5 seasonal forecasts of temperature and precipitation over East Africa. The current seasonal forecasting system provides monthly averaged forecast anomalies. These anomalies must be spatially downscaled and temporally disaggregated for use in application modeling (e.g. hydrology, agriculture). There are several available downscaling methodologies that can be implemented to accomplish this goal. Selected methods include both a non-homogenous hidden Markov model and an analogue based approach. A particular emphasis will be placed on quantifying the ability of different methods to capture the intermittency of precipitation within both the short and long rain seasons. Further, the ability to capture spatial covariances will be assessed. Both probabilistic and deterministic skill measures will be evaluated over the hindcast period

Levels of acid-soluble polyphosphate in growing cultures of Saccharomyces cerevisiae.

OpenAIRE

Solimene, R; Guerrini, A M; Donini, P

1980-01-01

Short-chain acid-soluble polyphosphates were extracted from growing cultures of Saccharomyces cerevisiae, and the changes in the levels of these compounds were determined. The production of acid-soluble polyphosphates correlated with the mitochondrial activities since it occurred in two bursts in respiration-competent yeast cells and in only one burst in respiration-deficient yeast cells. The possible role of these compounds is discussed.

Linking seasonal climate forecasts with crop models in Iberian Peninsula

Science.gov (United States)

Capa, Mirian; Ines, Amor; Baethgen, Walter; Rodriguez-Fonseca, Belen; Han, Eunjin; Ruiz-Ramos, Margarita

2015-04-01

Translating seasonal climate forecasts into agricultural production forecasts could help to establish early warning systems and to design crop management adaptation strategies that take advantage of favorable conditions or reduce the effect of adverse conditions. In this study, we use seasonal rainfall forecasts and crop models to improve predictability of wheat yield in the Iberian Peninsula (IP). Additionally, we estimate economic margins and production risks associated with extreme scenarios of seasonal rainfall forecast. This study evaluates two methods for disaggregating seasonal climate forecasts into daily weather data: 1) a stochastic weather generator (CondWG), and 2) a forecast tercile resampler (FResampler). Both methods were used to generate 100 (with FResampler) and 110 (with CondWG) weather series/sequences for three scenarios of seasonal rainfall forecasts. Simulated wheat yield is computed with the crop model CERES-wheat (Ritchie and Otter, 1985), which is included in Decision Support System for Agrotechnology Transfer (DSSAT v.4.5, Hoogenboom et al., 2010). Simulations were run at two locations in northeastern Spain where the crop model was calibrated and validated with independent field data. Once simulated yields were obtained, an assessment of farmer's gross margin for different seasonal climate forecasts was accomplished to estimate production risks under different climate scenarios. This methodology allows farmers to assess the benefits and risks of a seasonal weather forecast in IP prior to the crop growing season. The results of this study may have important implications on both, public (agricultural planning) and private (decision support to farmers, insurance companies) sectors. Acknowledgements Research by M. Capa-Morocho has been partly supported by a PICATA predoctoral fellowship of the Moncloa Campus of International Excellence (UCM-UPM) and MULCLIVAR project (CGL2012-38923-C02-02) References Hoogenboom, G. et al., 2010. The Decision

Changes in vegetation phenology are not reflected in atmospheric CO2 and 13 C/12 C seasonality.

Science.gov (United States)

Gonsamo, Alemu; D'Odorico, Petra; Chen, Jing M; Wu, Chaoyang; Buchmann, Nina

2017-10-01

Northern terrestrial ecosystems have shown global warming-induced advances in start, delays in end, and thus increased lengths of growing season and gross photosynthesis in recent decades. The tradeoffs between seasonal dynamics of two opposing fluxes, CO 2 uptake through photosynthesis and release through respiration, determine the influence of the terrestrial ecosystem on the atmospheric CO 2 and 13 C/ 12 C seasonality. Here, we use four CO 2 observation stations in the Northern Hemisphere, namely Alert, La Jolla, Point Barrow, and Mauna Loa Observatory, to determine how changes in vegetation productivity and phenology, respiration, and air temperature affect both the atmospheric CO 2 and 13 C/ 12 C seasonality. Since the 1960s, the only significant long-term trend of CO 2 and 13 C/ 12 C seasonality was observed at the northern most station, Alert, where the spring CO 2 drawdown dates advanced by 0.65 ± 0.55 days yr -1 , contributing to a nonsignificant increase in length of the CO 2 uptake period (0.74 ± 0.67 days yr -1 ). For Point Barrow station, vegetation phenology changes in well-watered ecosystems such as the Canadian and western Siberian wetlands contributed the most to 13 C/ 12 C seasonality while the CO 2 seasonality was primarily linked to nontree vegetation. Our results indicate significant increase in the Northern Hemisphere soil respiration. This means, increased respiration of 13 C depleted plant materials cancels out the 12 C gain from enhanced vegetation activities during the start and end of growing season. These findings suggest therefore that parallel warming-induced increases both in photosynthesis and respiration contribute to the long-term stability of CO 2 and 13 C/ 12 C seasonality under changing climate and vegetation activity. The summer photosynthesis and the soil respiration in the dormant seasons have become more vigorous which lead to increased peak-to-through CO 2 amplitude. As the relative magnitude of the increased

Effect of Short-Term Study Abroad Programs on Students' Cultural Adaptability

Science.gov (United States)

Mapp, Susan C.

2012-01-01

The number of U.S. students studying abroad has been growing, particularly those participating in short-term trips. However, literature on the effect of these short-term trips is lacking. The purpose of this study was to assess quantitatively the effect on bachelor students' cross-cultural adaptability using a pre-post design. Significant changes…

Histaminergic regulation of seasonal metabolic rhythms in Siberian hamsters.

Science.gov (United States)

I'anson, Helen; Jethwa, Preeti H; Warner, Amy; Ebling, Francis J P

2011-06-01

We investigated whether histaminergic tone contributes to the seasonal catabolic state in Siberian hamsters by determining the effect of ablation of histaminergic neurons on food intake, metabolic rate and body weight. A ribosomal toxin (saporin) conjugated to orexin-B was infused into the ventral tuberomammillary region of the hypothalamus, since most histaminergic neurons express orexin receptors. This caused not only 75-80% loss of histaminergic neurons in the posterior hypothalamus, but also some loss of other orexin-receptor expressing cells e.g. MCH neurons. In the long-day anabolic state, lesions produced a transient post-surgical decrease in body weight, but the hamsters recovered and maintained constant body weight, whereas weight gradually increased in sham-lesioned hamsters. VO(2) in the dark phase was significantly higher in the lesioned hamsters compared to shams, and locomotor activity also tended to be higher. In a second study in short days, sham-treated hamsters showed the expected seasonal decrease in body weight, but weight remained constant in the lesioned hamsters, as in the long-day study. Lesioned hamsters consumed more during the early dark phase and less during the light phase due to an increase in the frequency of meals during the dark and decreased meal size during the light, and their cumulative food intake in their home cages was greater than in the control hamsters. In summary, ablation of orexin-responsive cells in the posterior hypothalamus blocks the short-day induced decline in body weight by preventing seasonal hypophagia, evidence consistent with the hypothesis that central histaminergic mechanisms contribute to long-term regulation of body weight. Copyright © 2011 Elsevier Inc. All rights reserved.

Studies on the abnormality of embryo sac and pollen fertility in aurotetraploid rice during different growing seasons

International Nuclear Information System (INIS)

Shahid, M.; Jilanfan, S.; Changmin, W.; Peng, Z.; Xiang-dong, X.

2010-01-01

Auto tetraploid rice has a great genetic potential but low seed setting rate is the major encumbrance in its use. Embryo sac fertility and pollen fertility are the most important factors which affect the seed setting rate in auto tetraploid rice. Whole mount eosin B-staining confocal laser scanning microscopy (WE-CLSM) was used to study the fertility and abnormalities in embryo sacs of diploid and auto tetraploid rice during different seasons. The results indicated that the embryo sac fertility (64.5%) was much low in auto tetraploid than that in diploid rice (86%), and five main types of abnormal embryo sac were found in all 10 auto tetraploid rice. Moreover, some other type abnormal embryo sacs were also observed in auto tetraploid rice. Embryo sac without female germ unit and embryo sac degeneration were the most frequent types of abnormalities in auto tetraploid rice. Embryo sac fertility ranged from 49.3% to 79.3%, pollen fertility ranged from 56.2 to 85.9%, and seed setting rate varied from 12.5 to 69.01% in various genotypes of auto tetraploid rice. Embryo sac and pollen fertility were found to have a significant correlation with seed setting rate. Seasons have significant effect on pollen and embryo sac fertility in both type of rice. All the auto tetraploid lines exhibited different types of embryo sac abnormalities which indicated that these might be related to different genotypes. (author)

A Theoretical Approach to Understanding Population Dynamics with Seasonal Developmental Durations

Science.gov (United States)

Lou, Yijun; Zhao, Xiao-Qiang

2017-04-01

There is a growing body of biological investigations to understand impacts of seasonally changing environmental conditions on population dynamics in various research fields such as single population growth and disease transmission. On the other side, understanding the population dynamics subject to seasonally changing weather conditions plays a fundamental role in predicting the trends of population patterns and disease transmission risks under the scenarios of climate change. With the host-macroparasite interaction as a motivating example, we propose a synthesized approach for investigating the population dynamics subject to seasonal environmental variations from theoretical point of view, where the model development, basic reproduction ratio formulation and computation, and rigorous mathematical analysis are involved. The resultant model with periodic delay presents a novel term related to the rate of change of the developmental duration, bringing new challenges to dynamics analysis. By investigating a periodic semiflow on a suitably chosen phase space, the global dynamics of a threshold type is established: all solutions either go to zero when basic reproduction ratio is less than one, or stabilize at a positive periodic state when the reproduction ratio is greater than one. The synthesized approach developed here is applicable to broader contexts of investigating biological systems with seasonal developmental durations.

Trace element seasonality in marine macroalgae of different functional-form groups.

Science.gov (United States)

Malea, Paraskevi; Chatziapostolou, Anastasia; Kevrekidis, Theodoros

2015-02-01

Novel information on the seasonality of element accumulation in seaweeds is provided. Seasonal patterns of As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Sr, U, V and Zn concentrations in macroalgae belonging to different functional-form groups (Ulva intestinalis, Ulva rigida, Codium fragile, Gracilaria gracilis) from the Thessaloniki Gulf, Aegean Sea were determined and compared. Uni- and multivariate data analyses were applied. Element concentrations generally decreased during spring and/or summer, probably due to the growth effect, but a reverse trend, particularly in Ulva species, was also observed. Most elements (Cd, Co, Cr, Cu, Mo, Ni, Pb, Sr) in Ulva species displayed a comparatively low monthly variability, indicating that the extent of seasonal variation is closely related to thallus morphology and growth strategy. In particular, these data suggest that Cd, Co, Cr, Cu, Mo, Ni, Pb and Sr contents in fast-growing, sheet-like macroalgae are less influenced by the season, compared to their contents in coarsely-branched and thick-leathery macroalgae; therefore, sheet-like macroalgae may be more appropriate to be used in biomonitoring of coastal waters. The data presented could be utilized in the development of biomonitoring programmes for the protection of coastal environments. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interaction in Short rotation coppice willow, Salix viminalis genotype mixtures

Energy Technology Data Exchange (ETDEWEB)

Begley, D. [Department of Biological Sciences, Queen' s University Belfast, Newforge Lane, Belfast BT9 5PX, Northern Ireland (United Kingdom); McCracken, A.R. [Applied Plant Science and Biometrics Division, Agri-Food and Biosciences Institute, 18A Newforge Lane, Belfast BT9 5PX, Northern Ireland (United Kingdom)]|[Northern Ireland Horticulture and Plant Breeding Station, Applied Plant Science and Biometrics Division, Agri-Food and Biosciences Institute, Loughgall, Co., Armagh BT61 8JB, Northern Ireland (United Kingdom); Dawson, W.M. [Northern Ireland Horticulture and Plant Breeding Station, Applied Plant Science and Biometrics Division, Agri-Food and Biosciences Institute, Loughgall, Co., Armagh BT61 8JB, Northern Ireland (United Kingdom); Watson, S. [Applied Plant Science and Biometrics Division, Agri-Food and Biosciences Institute, 18A Newforge Lane, Belfast BT9 5PX, Northern Ireland (United Kingdom)

2009-02-15

Seven straight Salix viminalis genotypes with different levels of rust (Melampsora epitea) susceptibility were grown as mono-plots as well as being incorporated into a range of mixtures. Two 3-year harvests (2003 and 2006) were taken. Disease progress was followed on each of the individual genotypes throughout each growing season 2001-2006. In 2003 there were small but significant yield increases from the mixtures compared to the yield of individual components grown as mono-plots. These differences were not evident at the second harvest in 2006. No consistent effect of mixtures on reducing rust on the most susceptible genotype, Salix viminalis '77082' were observed. In some years, e.g. 2003, at certain times during the growing season, significant reductions were observed on Salix viminalis '77082' in certain 3-way mixtures compared to mono-plots. These, however, were not repeated consistently in subsequent years. It was concluded that the current commercial practice in many parts of Europe of planting mixtures as a disease control strategy will only be effective if there is sufficient genetic diversity between the Salix genotypes incorporated into the mixture. (author)

Satellite assessment of early-season forecasts for vegetation conditions of grazing allotments in Nevada, United States

Science.gov (United States)

Fifteen years of enhanced vegetation index data from the MODIS sensor are examined in conjunction with precipitation and the Palmer drought severity index to assess how well growing season conditions for vegetation within grazing allotments of Nevada can be predicted at different times of the year. ...

Effects of Forest Gaps on Litter Lignin and Cellulose Dynamics Vary Seasonally in an Alpine Forest

Directory of Open Access Journals (Sweden)

Han Li

2016-01-01

Full Text Available To understand how forest gaps and the associated canopy control litter lignin and cellulose dynamics by redistributing the winter snow coverage and hydrothermal conditions in the growing season, a field litterbag trial was conducted in the alpine Minjiang fir (Abies faxoniana Rehder and E.H. Wilson forest in a transitional area located in the upper reaches of the Yangtze River and the eastern Tibetan Plateau. Over the first year of litter decomposition, the litter exhibited absolute cellulose loss and absolute lignin accumulation except for the red birch litter. The changes in litter cellulose and lignin were significantly affected by the interactions among gap position, period and species. Litter cellulose exhibited a greater loss in the winter with the highest daily loss rate observed during the snow cover period. Both cellulose and lignin exhibited greater changes under the deep snow cover at the gap center in the winter, but the opposite pattern occurred under the closed canopy in the growing season. The results suggest that decreased snowpack seasonality due to winter warming may limit litter cellulose and lignin degradation in alpine forest ecosystems, which could further inhibit litter decomposition. As a result, the ongoing winter warming and gap vanishing would slow soil carbon sequestration from foliar litter in cold biomes.

The alpha-tocopherol content of leaves of pedunculate oak (Quercus robur L.)--variation over the growing season and along the vertical light gradient in the canopy.

Science.gov (United States)

Hansen, Ute; Schneiderheinze, Jenny; Stadelmann, Simone; Rank, Barbara

2003-01-01

This study was performed in order to investigate whether the actual requirement for defence against photo-oxidative stress is reflected by the alpha-tocopherol (alpha-Toco) content in leaves of pedunculate oak (Quercus robur L.). Antioxidants and pigments were quantified in leaves that were collected on six days between May and September 2000 in a mixed pine/oak forest at canopy positions differing in light environment. Pools of hydrophilic antioxidants and photo-protective xanthophyll cycle pigments (V + A + Z) reflected the anti-oxidative demand, as these pools increased with the average light intensity to which the leaves were acclimated. The photo-protective demand was not the determinant of the alpha-Toco content of oak leaves, as (1) foliage of a young oak, exposed to low light levels in the understorey, contained higher amounts of this lipophilic antioxidant than leaves sampled from semimature oaks at canopy positions with a similar light environment, and (2) a strong increase in the alpha-Toco content over the growing season was detected at each investigated crown position, whereas the V + A + Z pool did not show a concomitant accumulation during leaf ageing. The rate of alpha-Toco accumulation differed distinctly between samples taken at different canopy positions.

Application of electron-beam irradiation on the production of salted and seasoned short-necked clam, Tapes Pilippinarum, for safe distribution

Energy Technology Data Exchange (ETDEWEB)

Kim, B.; Song, H.P.; Choe, J.H.; Jung, S. [Department of Animal Science and Biotechnology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Jang, A. [Quality Control and Utilization of Animal Products, National Institute of Animal Science, Suwon 441-706 (Korea, Republic of); Kim, Y.J. [Food Safety Research Division, Korea Food Research Institute, Seongnam 463-746 (Korea, Republic of); Jo, C. [Department of Animal Science and Biotechnology, Chungnam National University, Daejeon 305-764 (Korea, Republic of)], E-mail: cheorun@cnu.ac.kr

2009-07-15

Salted and seasoned short-necked clam (Tapes Philippinarum; SNC) and its major ingredients, red hot pepper powder, ginger, garlic and onion were irradiated at 0.5, 1, 2 and 5 kGy, respectively, and the microbiological and sensory quality were evaluated. The water activities of SNC and red pepper powder were 0.91 and 0.56, respectively, and others were higher than 0.97. The initial microbial populations of SNC were approximately 3.99, 4.38 and 2.22 log CFU/g for total aerobic bacteria, yeast and mold, and coliform bacteria. The highest contamination of total aerobic bacteria was detected from ground ginger among ingredients at 5.51 log CFU/g. Electron-beam irradiation (0, 0.5, 1, 2 and 5 kGy) significantly reduced the initial microbial level of SNC and its ingredients not only immediately after irradiation, but also during storage at 10 {sup o}C for 4 weeks (p<0.05). There was no adverse change of sensory score except for the color of onion irradiated at 5 kGy, which results in a lower score than control. From the results electron-beam irradiation is a useful tool to enhance the storage stability and safe distribution of SNC.

The role of arbuscular mycorrhizal fungi on the early-stage restoration of seasonally dry tropical forest in Chamela, Mexico

Directory of Open Access Journals (Sweden)

Pilar Huante

2012-04-01

Full Text Available It was evaluated the effect of two different sources of local inocula from two contrasting sites (mature forest, pasture of arbuscular mycorrhizae fungi (AMF and a non-mycorrhizal control on the plant growth of six woody species differing in functional characteristics (slow-, intermediate- and fast-growth, when introduced in a seasonally tropical dry forest (STDF converted into abandoned pasture. Six plots (12 X 12m were set as AMF inoculum source. Six replicates of six different species arranged in a Latin Square design were set in each plot. Plant height, cover area and the number of leaves produced by individual plant was measured monthly during the first growing season in each treatment. Species differed in their ability to benefit from AMF and the largest responsiveness in plant height and leaf production was exhibited by the slow-growing species Swietenia humilis, Hintonia latiflora and Cordia alliodora. At the end of the growing season (November, the plant height of the fast growing species Tabebuia donnel-smithii, Ceiba pentandra and Guazuma ulmifolia were not influenced by AMF. However, inocula of AMF increased leaf production of all plant species regardless the functional characteristics of the species, suggesting a better exploitation of above-ground space and generating a light limited environment under the canopy, which contributed to pasture suppression. Inoculation of seedlings planted in abandoned pasture areas is recommended for ecological restoration due to the high responsiveness of seedling growth in most of species. Use of forest inoculum with its higher diversity of AMF could accelerate the ecological restoration of the above and below-ground comunities.

A model of seasonal foliage dynamics of the subtropical mangrove species Rhizophora stylosa Griff. growing at the northern limit of its distribution

Directory of Open Access Journals (Sweden)

Sahadev Sharma

2014-08-01

Full Text Available Background Progress of forest production in response to the environment requires a quantitative understanding of leaf area development. Therefore, it is necessary to investigate the dynamics of seasonal crown foliage in order to understand the productivity of mangroves, which play an important role in the subtropical and tropical coastlines of the world. Method Crown foliage dynamics of the mangrove Rhizophora stylosa were studies to reveal patterns of leaf recruitment, survival and seasonal leaf area growth. Results Flushing of leaves occurred throughout the year, but both flushing and leaf area growth pattern of leaves varied with season. Maximum flushing occurred in summer, but leaf areas did not differ significantly with season. The half-expansion period is longer, and the intrinsic rate of increase was lower in winter. Summer flushed leaves grew faster at their initial stage and reached their maximum area over a shorter period of time. The difference in temperature and air vapor pressure deficit (VPD between summer and winter contributed to the present dynamics of foliage patterns. The mean leaf longevity was estimated to be 13.1 month. The crown foliage area was almost stable throughout the year. Conclusions Homeostatic control of the crown foliage area may be accompanied by the existence of ecophysiological mechanisms in R. stylosa. Integrating crown foliage dynamics into forest models represents an important step towards incorporating physiological mechanisms into the models for predicting growth responses to environmental changes and for understanding the complex responses of tree growth and litter production.

Identifying spikes and seasonal components in electricity spot price data: A guide to robust modeling

International Nuclear Information System (INIS)

Janczura, Joanna; Trück, Stefan; Weron, Rafał; Wolff, Rodney C.

2013-01-01

An important issue in fitting stochastic models to electricity spot prices is the estimation of a component to deal with trends and seasonality in the data. Unfortunately, estimation routines for the long-term and short-term seasonal pattern are usually quite sensitive to extreme observations, known as electricity price spikes. Improved robustness of the model can be achieved by (a) filtering the data with some reasonable procedure for outlier detection, and then (b) using estimation and testing procedures on the filtered data. In this paper we examine the effects of different treatments of extreme observations on model estimation and on determining the number of spikes (outliers). In particular we compare results for the estimation of the seasonal and stochastic components of electricity spot prices using either the original or filtered data. We find significant evidence for a superior estimation of both the seasonal short-term and long-term components when the data have been treated carefully for outliers. Overall, our findings point out the substantial impact the treatment of extreme observations may have on these issues and, therefore, also on the pricing of electricity derivatives like futures and option contracts. An added value of our study is the ranking of different filtering techniques used in the energy economics literature, suggesting which methods could be and which should not be used for spike identification. - Highlights: • First comprehensive study on the impact of spikes on seasonal pattern estimation • The effects of different treatments of spikes on model estimation are examined. • Cleaning spot prices for outliers yields superior estimates of the seasonal pattern. • Removing outliers provides better parameter estimates for the stochastic process. • Rankings of filtering techniques suggested in the literature are provided

An ethics curriculum for short-term global health trainees

OpenAIRE

DeCamp, Matthew; Rodriguez, Joce; Hecht, Shelby; Barry, Michele; Sugarman, Jeremy

2013-01-01

Background Interest in short-term global health training and service programs continues to grow, yet they can be associated with a variety of ethical issues for which trainees or others with limited global health experience may not be prepared to address. Therefore, there is a clear need for educational interventions concerning these ethical issues. Methods We developed and evaluated an introductory curriculum, ?Ethical Challenges in Short-term Global Health Training.? The curriculum was deve...

Oxygen isotopic analyses of individual planktic foraminifera species: Implications for seasonality in the western Arabian Sea

Digital Repository Service at National Institute of Oceanography (India)

Naidu, P.D.; Niitsuma, N.; Naik, S.S.

The variation of stable isotopes between individual shells of planktic foraminifera of a given species and size may provide short-term seasonal insight on Paleoceanography. In this context, oxygen isotope analyses of individual Globigerinoides...

The effect of seasonal changes and climatic factors on suicide attempts of young people.

Science.gov (United States)

Akkaya-Kalayci, Türkan; Vyssoki, Benjamin; Winkler, Dietmar; Willeit, Matthaeus; Kapusta, Nestor D; Dorffner, Georg; Özlü-Erkilic, Zeliha

2017-11-15

Seasonal changes and climatic factors like ambient temperature, sunlight duration and rainfall can influence suicidal behavior. This study analyses the relationship between seasonal changes and climatic variations and suicide attempts in 2131 young patients in Istanbul, Turkey. In our study sample, there was an association between suicide attempts in youths and seasonal changes, as suicide attempts occurred most frequently during summer in females as well as in males. Furthermore, there was a positive correlation between the mean temperature over the past 10 days and temperature at the index day and suicide attempts in females. After seasonality effects were mathematically removed, the mean temperature 10 days before a suicide attempt remained significant in males only, indicating a possible short-term influence of temperature on suicide attempts. This study shows an association between suicide attempts of young people and climatic changes, in particular temperature changes as well as seasonal changes. Therefore, the influence of seasonal changes and climatic factors on young suicide attempters should get more attention in research to understand the biopsychosocial mechanisms playing a role in suicide attempts of young people. As suicide attempts most frequently occur in young people, further research is of considerable clinical importance.

Role of burning season on initial understory vegetation response to prescribed fire in a mixed conifer forest

Science.gov (United States)

Knapp, E.E.; Schwilk, D.W.; Kane, J.M.; Keeley, J.E.

2007-01-01

Although the majority of fires in the western United States historically occurred during the late summer or early fall when fuels were dry and plants were dormant or nearly so, early-season prescribed burns are often ignited when fuels are still moist and plants are actively growing. The purpose of this study was to determine if burn season influences postfire vegetation recovery. Replicated early-season burn, late-season burn, and unburned control units were established in a mixed conifer forest, and understory vegetation was evaluated before and after treatment. Vegetation generally recovered rapidly after prescribed burning. However, late-season burns resulted in a temporary but significant drop in cover and a decline in species richness at the 1 m 2 scale in the following year. For two of the several taxa that were negatively affected by burning, the reduction in frequency was greater after late-season than early-season burns. Early-season burns may have moderated the effect of fire by consuming less fuel and lessening the amount of soil heating. Our results suggest that, when burned under high fuel loading conditions, many plant species respond more strongly to differences in fire intensity and severity than to timing of the burn relative to stage of plant growth. ?? 2007 NRC.

Seasonal variation in radiocesium concentrations in three tree species

International Nuclear Information System (INIS)

Garten, C.R. Jr.; Briese, L.A.; Sharitz, R.R.; Gentry, J.B.

1975-01-01

Radiocesium concentrations in leaves and stems of black willow (Salix nigra), wax myrtle (Myrica cerifera), and tag alder (Alnus serrulata) trees inhabiting a floodplain contaminated by production-reactor effluents were measured over 1 year. In willow and myrtle trees, leaf radiocesium levels were highest in the spring and declined during the growing season; stem levels remained relatively unchanged or exhibited a slight increase. Seasonal changes in alder tree parts depended on the site examined. The relationship among component parts was essentially consistent across species and collecting sites in the summer. The radiocesium concentrations in order of rank were: roots greater than or equal to leaves greater than stems. Species differences in component-part radiocesium levels were dependent on the part sampled and the collecting site examined. Mean soil to plant-part concentration factors in summer ranged from 0.9 to 7.6, and species means across leaves, stems, and roots averaged 2.1, 3.8, and 6.2 for alder, willow, and myrtle trees, respectively

Revisiting factors controlling methane emissions from high-Arctic tundra

DEFF Research Database (Denmark)

Mastepanov, M.; Sigsgaard, C.; Tagesson, T.

2013-01-01

controlling methane emission, i.e. temperature and water table position. Late in the growing season CH4 emissions were found to be very similar between the study years (except the extremely dry 2010) despite large differences in climatic factors (temperature and water table). Late-season bursts of CH4...... short-term control factors (temperature and water table). Our findings suggest the importance of multiyear studies with a continued focus on shoulder seasons in Arctic ecosystems....

Global left ventricular function in cardiac CT. Evaluation of an automated 3D region-growing segmentation algorithm

International Nuclear Information System (INIS)

Muehlenbruch, Georg; Das, Marco; Hohl, Christian; Wildberger, Joachim E.; Guenther, Rolf W.; Mahnken, Andreas H.; Rinck, Daniel; Flohr, Thomas G.; Koos, Ralf; Knackstedt, Christian

2006-01-01

The purpose was to evaluate a new semi-automated 3D region-growing segmentation algorithm for functional analysis of the left ventricle in multislice CT (MSCT) of the heart. Twenty patients underwent contrast-enhanced MSCT of the heart (collimation 16 x 0.75 mm; 120 kV; 550 mAseff). Multiphase image reconstructions with 1-mm axial slices and 8-mm short-axis slices were performed. Left ventricular volume measurements (end-diastolic volume, end-systolic volume, ejection fraction and stroke volume) from manually drawn endocardial contours in the short axis slices were compared to semi-automated region-growing segmentation of the left ventricle from the 1-mm axial slices. The post-processing-time for both methods was recorded. Applying the new region-growing algorithm in 13/20 patients (65%), proper segmentation of the left ventricle was feasible. In these patients, the signal-to-noise ratio was higher than in the remaining patients (3.2±1.0 vs. 2.6±0.6). Volume measurements of both segmentation algorithms showed an excellent correlation (all P≤0.0001); the limits of agreement for the ejection fraction were 2.3±8.3 ml. In the patients with proper segmentation the mean post-processing time using the region-growing algorithm was diminished by 44.2%. On the basis of a good contrast-enhanced data set, a left ventricular volume analysis using the new semi-automated region-growing segmentation algorithm is technically feasible, accurate and more time-effective. (orig.)

Global Analysis of Empirical Relationships Between Annual Climate and Seasonality of NDVI

Science.gov (United States)

Potter, C. S.

1997-01-01

This study describes the use of satellite data to calibrate a new climate-vegetation greenness function for global change studies. We examined statistical relationships between annual climate indexes (temperature, precipitation, and surface radiation) and seasonal attributes of the AVHRR Normalized Difference Vegetation Index (NDVI) time series for the mid-1980s in order to refine our empirical understanding of intraannual patterns and global abiotic controls on natural vegetation dynamics. Multiple linear regression results using global l(sup o) gridded data sets suggest that three climate indexes: growing degree days, annual precipitation total, and an annual moisture index together can account to 70-80 percent of the variation in the NDVI seasonal extremes (maximum and minimum values) for the calibration year 1984. Inclusion of the same climate index values from the previous year explained no significant additional portion of the global scale variation in NDVI seasonal extremes. The monthly timing of NDVI extremes was closely associated with seasonal patterns in maximum and minimum temperature and rainfall, with lag times of 1 to 2 months. We separated well-drained areas from l(sup o) grid cells mapped as greater than 25 percent inundated coverage for estimation of both the magnitude and timing of seasonal NDVI maximum values. Predicted monthly NDVI, derived from our climate-based regression equations and Fourier smoothing algorithms, shows good agreement with observed NDVI at a series of ecosystem test locations from around the globe. Regions in which NDVI seasonal extremes were not accurately predicted are mainly high latitude ecosystems and other remote locations where climate station data are sparse.

Evaluating EO-based canopy water stress from seasonally detrended NDVI and SIWSI with modeled evapotranspiration in the Senegal River Basin

DEFF Research Database (Denmark)

Olsen, Jørgen L.; Stisen, Simon; Proud, Simon Richard

2015-01-01

the Shortwave Infrared Water Stress Index (SIWSI) as compared to Normalized Difference Vegetation Index (NDVI). We perform a spatio-temporal evaluation of NDVI and SIWSI using geostationary remote sensing imagery from the Spinning Enhanced Visible and Infrared Imager (SEVIRI). The indices and their seasonally......Satellite remote sensing of vegetation parameters and stress is a key issue for semi-arid areas such as the Sahel, where vegetation is an important part of the natural resource base. In this study we examine if additional information can be obtained on intra-seasonal short term scale by using...... gradient in the river catchment. The hypothesis that short term evolution of index anomalies are related to canopy water status was tested by comparing 10-day averages of ETa with short term changes in daily NDVI and SIWSI anomalies, and moderate to strong coefficients of determination where found when...

Diverging seasonal extremes for ocean acidification during the twenty-first century

Science.gov (United States)

Kwiatkowski, Lester; Orr, James C.

2018-01-01

How ocean acidification will affect marine organisms depends on changes in both the long-term mean and the short-term temporal variability of carbonate chemistry1-8. Although the decadal-to-centennial response to atmospheric CO2 and climate change is constrained by observations and models1, 9, little is known about corresponding changes in seasonality10-12, particularly for pH. Here we assess the latter by analysing nine earth system models (ESMs) forced with a business-as-usual emissions scenario13. During the twenty-first century, the seasonal cycle of surface-ocean pH was attenuated by 16 ± 7%, on average, whereas that for hydrogen ion concentration [H+] was amplified by 81 ± 16%. Simultaneously, the seasonal amplitude of the aragonite saturation state (Ωarag) was attenuated except in the subtropics, where it was amplified. These contrasting changes derive from regionally varying sensitivities of these variables to atmospheric CO2 and climate change and to diverging trends in seasonal extremes in the primary controlling variables (temperature, dissolved inorganic carbon and alkalinity). Projected seasonality changes will tend to exacerbate the impacts of increasing [H+] on marine organisms during the summer and ameliorate the impacts during the winter, although the opposite holds in the high latitudes. Similarly, over most of the ocean, impacts from declining Ωarag are likely to be intensified during the summer and dampened during the winter.

Discoloration of polyvinyl chloride (PVC) tape as a proxy for water-table depth in peatlands: validation and assessment of seasonal variability

Science.gov (United States)

Booth, Robert K.; Hotchkiss, Sara C.; Wilcox, Douglas A.

2005-01-01

Summary: 1. Discoloration of polyvinyl chloride (PVC) tape has been used in peatland ecological and hydrological studies as an inexpensive way to monitor changes in water-table depth and reducing conditions. 2. We investigated the relationship between depth of PVC tape discoloration and measured water-table depth at monthly time steps during the growing season within nine kettle peatlands of northern Wisconsin. Our specific objectives were to: (1) determine if PVC discoloration is an accurate method of inferring water-table depth in Sphagnum-dominated kettle peatlands of the region; (2) assess seasonal variability in the accuracy of the method; and (3) determine if systematic differences in accuracy occurred among microhabitats, PVC tape colour and peatlands. 3. Our results indicated that PVC tape discoloration can be used to describe gradients of water-table depth in kettle peatlands. However, accuracy differed among the peatlands studied, and was systematically biased in early spring and late summer/autumn. Regardless of the month when the tape was installed, the highest elevations of PVC tape discoloration showed the strongest correlation with midsummer (around July) water-table depth and average water-table depth during the growing season. 4. The PVC tape discoloration method should be used cautiously when precise estimates are needed of seasonal changes in the water-table.

Growing season variability of net ecosystem CO2 exchange and evapotranspiration of a sphagnum mire in the broad-leaved forest zone of European Russia

International Nuclear Information System (INIS)

Olchev, A; Volkova, E; Karataeva, T; Novenko, E

2013-01-01

The spatial and temporal variability of net ecosystem exchange (NEE) of CO 2 and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest–steppe zones in the central part of European Russia in the Tula region was described using results from field measurements. NEE and ET were measured using a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO 2 /H 2 O analyzer, LI-840A (Li-Cor, USA) along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and in May 2013. The results of the field measurements showed significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation and ground water level. The seasonal patterns of NEE and ET within the mire were quite different. During the entire growing season the central part of the mire was a sink of CO 2 for the atmosphere. NEE reached maximal values in June–July (−6.8 ± 4.2 μmol m −2 s −1 ). The southern peripheral part of the mire, due to strong shading by the surrounding forest, was a sink of CO 2 for the atmosphere in June–July only. ET reached maximal values in the well-lighted central parts of the mire in May (0.34 ± 0.20 mm h −1 ) mainly because of high air and surface temperatures and the very wet upper peat horizon and sphagnum moss. Herbaceous species made the maximum contribution to the total gross primary production (GPP) in both the central and the peripheral parts of the mire. The contribution of sphagnum to the total GPP of these plant communities was relatively small and ranged on sunny days of July–August from −1.1 ± 1.1 mgC g −1 of dry weight (DW) per hour in the peripheral zone of the mire to −0.6 ± 0.2 mgC g −1 DW h −1 at the mire center. The sphagnum layer made the maximum contribution to total ET at the mire center (0

Influence of season of birth on growth and reproductive development of Brahman bulls.

Science.gov (United States)

Tatman, Shawn R; Neuendorff, Don A; Wilson, Timothy W; Randel, Ronald D

2004-07-01

Seasonal effects on reproduction are more dramatic in Bos indicus than Bos taurus cattle. This experiment evaluated reproductive development of fall- (n=7) versus spring- (n = 10) born Brahman bulls to determine if season of birth affects reproductive development. Measurements of growth and reproductive development began after weaning and continued at bi-weekly intervals until each bull reached sexual maturity. Different stages of sexual development were classified according to characteristics of the ejaculate and included first sperm in the ejaculate, puberty (> 50 x 10(6) sperm/ejaculate), and sexual maturity (two ejaculates with > 500 = 10(6) sperm/ejaculate). Average daily increases in all measured traits were similar in fall- and spring-born bulls and there were no differences in age, body weight, scrotal circumference, or paired testis volume between groups at first sperm or puberty. However, fall-born bulls were older (P days versus 481 days, respectively) as the interval between puberty and sexual maturity was longer (P days versus 54 days, respectively). The prolonged interval between puberty and sexual maturity in fall-born calves coincided with a short photoperiod (winter) whereas the short interval between puberty and sexual maturity in spring-born calves coincided with a long photoperiod (summer). In conclusion, season of birth affected sexual development; photoperiod might be involved in regulating testicular function immediately after puberty in Brahman bulls.

Different growth responses of C3 and C4 grasses to seasonal water and nitrogen regimes and competition in a pot experiment.

Science.gov (United States)

Niu, Shuli; Liu, Weixing; Wan, Shiqiang

2008-01-01

Understanding temporal niche separation between C(3) and C(4) species (e.g. C(3) species flourishing in a cool spring and autumn while C(4) species being more active in a hot summer) is essential for exploring the mechanism for their co-existence. Two parallel pot experiments were conducted, with one focusing on water and the other on nitrogen (N), to examine growth responses to water or nitrogen (N) seasonality and competition of two co-existing species Leymus chinensis (C(3) grass) and Chloris virgata (C(4) grass) in a grassland. The two species were planted in either monoculture (two individuals of one species per pot) or a mixture (two individuals including one L. chinensis and one C. virgata per pot) under three different water or N seasonality regimes, i.e. the average model (AM) with water or N evenly distributed over the growing season, the one-peak model (OPM) with more water or N in the summer than in the spring and autumn, and the two-peak model (TPM) with more water or N in the spring and autumn than in the summer. Seasonal water regimes significantly affected biomass in L. chinensis but not in C. virgata, while N seasonality impacted biomass and relative growth rate of both species over the growing season. L. chinensis accumulated more biomass under the AM and TPM than OPM water or N treatments. Final biomass of C. virgata was less impacted by water and N seasonality than that of L. chinensis. Interspecific competition significantly decreased final biomass in L. chinensis but not in C. virgata, suggesting an asymmetric competition between the two species. The magnitude of interspecific competition varied with water and N seasonality. Changes in productivity and competition balance of L. chinensis and C. virgata under shifting seasonal water and N availabilities suggest a contribution of seasonal variability in precipitation and N to the temporal niche separation between C(3) and C(4) species.

Earlier Snowmelt Changes the Ratio Between Early and Late Season Forest Productivity

Science.gov (United States)

Knowles, J. F.; Molotch, N. P.; Trujillo, E.; Litvak, M. E.

2017-12-01

Future projections of declining snowpack and increasing potential evaporation associated with climate warming are predicted to advance the timing of snowmelt in mountain ecosystems globally. This scenario has direct implications for snowmelt-driven forest productivity, but the net effect of temporally shifting moisture dynamics is unknown with respect to the annual carbon balance. Accordingly, this study uses both satellite- and tower-based observations to document the forest productivity response to snowpack and potential evaporation variability between 1989 and 2012 throughout the southern Rocky Mountain ecoregion, USA. These results show that a combination of low snow accumulation and record high potential evaporation in 2012 resulted in the 34-year minimum ecosystem productivity that could be indicative of future conditions. Moreover, early and late season productivity were significantly and inversely related, suggesting that future shifts toward earlier or reduced snowmelt could increase late-season moisture stress to vegetation and thus restrict productivity despite a longer growing season. This relationship was further subject to modification by summer precipitation, and the controls on the early/late season productivity ratio are explored within the context of ecosystem carbon storage in the future. Any perturbation to the carbon cycle at this scale represents a potential feedback to climate change since snow-covered forests represent an important global carbon sink.

Ultra-short-course booster is effective in recurrent grass pollen-induced allergic rhinoconjunctivitis.

Science.gov (United States)

Pfaar, O; Lang, S; Pieper-Fürst, U; Astvatsatourov, A; Gerich, F; Klimek, L; Kramer, M F; Reydelet, Y; Shah-Hosseini, K; Mösges, R

2018-01-01

A relevant proportion of allergic rhinoconjunctivitis (ARC) patients experience recurrent symptoms after successfully completing allergen immunotherapy (AIT). This prospective, controlled, noninterventional study used internationally standardized instruments to determine the clinical effects of a preseasonal, ultra-short-course booster AIT on clinical outcome parameters. This two-arm study included patients aged ≥12 years with recurrent grass pollen-induced seasonal AR who had completed a successful course of any grass pollen AIT at least 5 years before enrolment. Overall, 56 patients received one preseasonal short-course booster AIT using tyrosine-absorbed grass pollen allergoids containing the adjuvant monophosphoryl lipid A (MPL ® ); 51 control patients received symptomatic medication. The combined symptom and medication score (CSMS) was recorded in the (peak) grass pollen season. Furthermore, concomitant (antiallergic) medication use, the patients' state of health, Mini Rhinoconjunctivitis Quality of Life Questionnaire (MiniRQLQ) results and safety/tolerability of the treatment were assessed. The CSMS in the peak grass pollen season was significantly lower in the booster AIT group (Δ=38.4%, Pallergoids containing the adjuvant MPL ® effectively prevents re-occurrence of symptoms in patients with grass pollen-induced ARC. © 2017 The Authors. Allergy Published by John Wiley & Sons Ltd.

Seasonal carbohydrate storage and mobilization in bearing and non-bearing pistachio (Pistacia vera) trees.

Science.gov (United States)

Spann, Timothy M; Beede, Robert H; Dejong, Theodore M

2008-02-01

We analyzed annual carbohydrate storage and mobilization of bearing ("on") and non-bearing ("off") 'Kerman' pistachio (Pistacia vera L.) trees growing on three different rootstocks. On all rootstocks, carbohydrate storage in shoots and branches of "on" and "off" trees was lowest following the spring growth flush. In "off" trees, stored carbohydrates increased and remained high after the initial growth flush. In "on" trees, stem carbohydrates increased temporarily in early summer, but were mobilized in mid-season during kernel fill, and then increased again after nut harvest. During the dormant season, the only substantial differences in carbohydrate storage between previously "on" and "off" trees were found in the roots of the weakest rootstock. The annual carbohydrate storage and mobilization pattern in canopy branches of heavily cropped pistachio trees appeared to be driven by carbohydrate demands related to nut development and untempered by tree vigor. Mobilization of carbohydrates from current-season and 1- and 2-year-old stem wood of "on" trees during the primary period of kernel fill corresponded with the period of inflorescence bud abscission. Thus, the alternate bearing pattern associated with inflorescence bud abscission in 'Kerman' pistachio may be a function of mid-season mobilization of stored carbohydrates in current-season stems resulting in stimulation of inflorescence bud abscission.

Seasonal response of ghrelin, growth hormone, and insulin-like growth factor I in the free-ranging Florida manatee (Trichechus manatus latirostris)

Science.gov (United States)

Tighe, Rachel L; Bonde, Robert K.; Avery, Julie P.

2016-01-01

Seasonal changes in light, temperature, and food availability stimulate a physiological response in an animal. Seasonal adaptations are well studied in Arctic, Sub-Arctic, and hibernating mammals; however, limited studies have been conducted in sub-tropical species. The Florida manatee (Trichechus manatus latirostris), a sub-tropical marine mammal, forages less during colder temperatures and may rely on adipose stores for maintenance energy requirements. Metabolic hormones, growth hormone (GH), insulin-like growth factor (IGF)-I, and ghrelin influence growth rate, accretion of lean and adipose tissue. They have been shown to regulate seasonal changes in body composition. The objective of this research was to investigate manatee metabolic hormones in two seasons to determine if manatees exhibit seasonality and if these hormones are associated with seasonal changes in body composition. In addition, age related differences in these metabolic hormones were assessed in multiple age classes. Concentrations of GH, IGF-I, and ghrelin were quantified in adult manatee serum using heterologous radioimmunoassays. Samples were compared between short (winter) and long (summer) photoperiods (n = 22 male, 20 female) and by age class (adult, juvenile, and calf) in long photoperiods (n = 37). Short photoperiods tended to have reduced GH (p = 0.08), greater IGF-I (p = 0.01), and greater blubber depth (p = 0.03) compared with long photoperiods. No differences were observed in ghrelin (p = 0.66). Surprisingly, no age related differences were observed in IGF-I or ghrelin concentrations (p > 0.05). However, serum concentrations of GH tended (p = 0.07) to be greater in calves and juveniles compared with adults. Increased IGF-I, greater blubber thickness, and reduced GH during short photoperiod suggest a prioritization for adipose deposition. Whereas, increased GH, reduced blubber thickness, and decreased IGF-I in long photoperiod suggest prioritization of lean tissue

Chemical composition and fuel wood characteristics of fast growing tree species in India

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Chauhan, S. K.; Soni, R.

2012-04-01

India is one of the growing economy in the world and energy is a critical input to sustain the growth of development. Country aims at security and efficiency of energy. Though fossil fuel will continue to play a dominant role in energy scenario but country is committed to global environmental well being thus stressing on environment friendly technologies. Concerns of energy security in this changing climatic situation have led to increasing support for the development of new renewable source of energy. Government though is determined to facilitate bio-energy and many projects have been established but initial after-affects more specifically on the domestic fuelwood are evident. Even the biomass power generating units are facing biomass crisis and accordingly the prices are going up. The CDM projects are supporting the viability of these units resultantly the Indian basket has a large number of biomass projects (144 out of total 506 with 28 per cent CERs). The use for fuelwood as a primary source of energy for domestic purpose by the poor people (approx. 80 per cent) and establishment of bio-energy plants may lead to deforestation to a great extent and only solution to this dilemma is to shift the wood harvest from the natural forests to energy plantations. However, there is conspicuous lack of knowledge with regards to the fuelwood characteristics of fast growing tree species for their selection for energy plantations. The calorific value of the species is important criteria for selection for fuel but it is affected by the proportions of biochemical constituents present in them. The aim of the present work was to study the biomass production, calorific value and chemical composition of different short rotation tree species. The study was done from the perspective of using the fast growing tree species for energy production at short rotation and the study concluded that short rotation tree species like Gmelina arborea, Eucalyptus tereticornis, Pongamia pinnata

Seasonal Belowground Ecosystem and Eco-enzymatic Responses to Soil pH and Phosphorus Availability in Temperate Hardwood Forests

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Smemo, K. A.; Deforest, J. L.; Petersen, S. L.; Burke, D.; Hewins, C.; Kluber, L. A.; Kyker, S. R.

2013-12-01

Atmospheric acid deposition can increase phosphorus (P) limitation in temperate hardwood forests by increasing N availability, and therefore P demand, and/or by decreasing pH and occluding inorganic P. However, only recently have studies demonstrated that P limitation can occur in temperate forests and very little is known about the temporal aspects of P dynamics in acidic forest soils and how seasonal shifts in nutrient availability and demand influence microbial investment in extracellular enzymes. The objectives of this study were to investigate how P availability and soil pH influence seasonal patterns of nutrient cycling and soil microbial activity in hardwood forests that experience chronic acid deposition. We experimentally manipulated soil pH, P, or both for three years and examined soil treatment responses in fall, winter, spring, early summer, and late summer. We found that site (glaciated versus unglaciated) and treatment had the most significant influence on nutrient pools and cycling. In general, nutrient pools were higher in glaciated soils than unglaciated for measured nutrients, including total C and N (2-3 times higher), extractable inorganic nitrogen, and readily available P. Treatment had no impact on total C and N pools in either region, but did affect other measured nutrients such as ammonium, which was greatest in the elevated pH treatment for both sites. As expected, readily available P pools were highest in the elevated P treatments (3 fold increase in both sites), but raising pH decreased available P pools in the glaciated site. Raising soil pH increased both net N mineralization rates and net P mineralization rates, regardless of site. Nitrification responses were complex, but we observed an overall significant nitrification increase under elevated pH, particularly in the growing season. Extracellular enzyme activity showed more seasonal patterns than site and treatment effects, exhibiting significant growing season activity reductions for

Seasonal timing of first rain storms affects rare plant population dynamics

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Levine, J.M.; McEachern, A.K.; Cowan, C.

2011-01-01

A major challenge in forecasting the ecological consequences of climate change is understanding the relative importance of changes to mean conditions vs. changes to discrete climatic events, such as storms, frosts, or droughts. Here we show that the first major storm of the growing season strongly influences the population dynamics of three rare and endangered annual plant species in a coastal California (USA) ecosystem. In a field experiment we used moisture barriers and water addition to manipulate the timing and temperature associated with first major rains of the season. The three focal species showed two- to fivefold variation in per capita population growth rates between the different storm treatments, comparable to variation found in a prior experiment imposing eightfold differences in season-long precipitation. Variation in germination was a major demographic driver of how two of three species responded to the first rains. For one of these species, the timing of the storm was the most critical determinant of its germination, while the other showed enhanced germination with colder storm temperatures. The role of temperature was further supported by laboratory trials showing enhanced germination in cooler treatments. Our work suggests that, because of species-specific cues for demographic transitions such as germination, changes to discrete climate events may be as, if not more, important than changes to season-long variables.

Seasonal correction factors in radon exposure assessment: are they help or hindrance?

International Nuclear Information System (INIS)

Denman, A.R.; Groves-Kirkby, C.J.; Phillips, P.S.; Woolridge, A.C.; Crockett, R.G.M.

2008-01-01

Northern Hemisphere radon levels are generally higher in Winter than in Summer, primarily due to the increased interior/exterior temperature difference during the heating season, which results in greater atmospheric pressure differential and enhanced radon ingress. Following a survey of domestic radon levels in the United Kingdom (UK), the former National Radiological Protection Board (NRPB) established measurement protocols and promulgated nationally-applicable Seasonal Correction Factors (SCF). These factors convert a one-month or three-month radon concentration measurement, commencing in any month of the year, to an annual mean radon concentration. Subsequent study suggests that this approach may not be sufficiently sensitive to local conditions, and a major independent investigation reported seasonal correction factors specific to nine geographic regions, together with a composite set applicable to all regions. Similar geographical variability has been observed in other countries. In a recent evaluation of the applicability of short-term exposures in quantifying long-term domestic radon levels, radon levels in 34 houses were monitored over a 12-month period with 1-week, 1-month and 3-month exposures. Radon concentration variation departed significantly from that expected on the basis of the recommended SCFs, with year-end discontinuities at all exposure durations. Weekly monitoring with electrets was continued in three of these locations for four years. Short-term variations in radon levels were observed, particularly during the shorter exposures, and this dataset has also shown year-on-year variations. Overall, SCFs derived from this dataset are significantly lower than those recommended, but are comparable with other results from the UK and elsewhere, particularly those that recognise geological diversity and are consequently prepared on a regional rather than a national basis. These findings call into question the validity of using nationally

Abundance, Fishing Season and Management Strategy for Blue Swimming Crab (Portunus pelagicus) in Pangkajene Kepulauan, South Sulawesi, Indonesia.

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Wiyono, Eko Sri; Ihsan

2018-03-01

In order to manage blue swimming crabs in Pangkajene Kepulauan, management measures are required. Since the environment which affects the abundance of the blue swimming crab varies seasonally, it is necessary to take into account the seasonal nature with the aim of developing a management strategy. The objectives of this study are to define the abundance of and fishing season of blue swimming crabs in the Pangkajene Kepulauan waters, South Sulawesi, Indonesia. The fishing season was analysed using seasonal index analysis, while fish abundance was analysed by means of Equilibrium-Schaefer. The result of this study demonstrated that fishermen allocate their fishing gear all year, although the fish catch is seasonal. Based on analysis of the result, the fishing season for the blue swimming crabs is short. The peak fishing season starts in May and finishes in June. However, in order to enable their families to earn a living, fishermen operated their fishing gear throughout the year. As a result, both catch landing and effort were close to maximum sustainable yield (MSY). In order to reduce fishing pressure, it is necessary to reduce fishing gear and have a seasonal arrangement regarding fishing gear allocation.

Seasonal variations of aerosol residence time in the lower atmospheric boundary layer

International Nuclear Information System (INIS)

Ahmed, A.A.; Mohamed, A.; Ali, A.E.; Barakat, A.; Abd El-Hady, M.; El-Hussein, A.

2004-01-01

During a one year period, from Jan. 2002 up to Dec. 2002, approximately 130 air samples were analyzed to determine the atmospheric air activity concentrations of short- and long-lived ( 222 Rn) decay products 214 Pb and 210 Pb. The samples were taken by using a single-filter technique and γ-spectrometry was applied to determine the activity concentrations. A seasonal fluctuation in the concentration of 214 Pb and 210 Pb in surface air was observed. The activity concentrations of both radionuclides were observed to be relatively higher during the winter/autumn season than in spring/summer season. The mean activity concentration of 214 Pb and 210 Pb within the whole year was found to be 1.4±0.27 Bq m -3 and 1.2±0.15 mBq m -3 , respectively. Different 210 Pb: 214 Pb activity ratios during the year varied between 1.78x10 -4 and 1.6x10 -3 with a mean value of 8.9x10 -4 ±7.6x10 -5 . From the ratio between the activity concentrations of the radon decay products 214 Pb and 210 Pb a mean residence time (MRT) of aerosol particles in the atmosphere of about 10.5±0.91 d could be estimated. The seasonal variation pattern shows relatively higher values of MRT in spring/summer season than in winter/autumn season. The MRT data together with relative humidity (RH), air temperature (T) and wind speed (WS), were used for a comprehensive regression analysis of its seasonal variation in the atmospheric air

A New Strategy for Short-Term Load Forecasting

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Yi Yang

2013-01-01

Full Text Available Electricity is a special energy which is hard to store, so the electricity demand forecasting remains an important problem. Accurate short-term load forecasting (STLF plays a vital role in power systems because it is the essential part of power system planning and operation, and it is also fundamental in many applications. Considering that an individual forecasting model usually cannot work very well for STLF, a hybrid model based on the seasonal ARIMA model and BP neural network is presented in this paper to improve the forecasting accuracy. Firstly the seasonal ARIMA model is adopted to forecast the electric load demand day ahead; then, by using the residual load demand series obtained in this forecasting process as the original series, the follow-up residual series is forecasted by BP neural network; finally, by summing up the forecasted residual series and the forecasted load demand series got by seasonal ARIMA model, the final load demand forecasting series is obtained. Case studies show that the new strategy is quite useful to improve the accuracy of STLF.

Seasonal and interannual dynamics of soil microbial biomass and available nitrogen in an alpine meadow in the eastern part of Qinghai-Tibet Plateau, China

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Xu, Bo; Wang, Jinniu; Wu, Ning; Wu, Yan; Shi, Fusun

2018-01-01

Soil microbial activity varies seasonally in frozen alpine soils during cold seasons and plays a crucial role in available N pool accumulation in soil. The intra- and interannual patterns of microbial and nutrient dynamics reflect the influences of changing weather factors, and thus provide important insights into the biogeochemical cycles and ecological functions of ecosystems. We documented the seasonal and interannual dynamics of soil microbial and available N in an alpine meadow in the eastern part of Qinghai-Tibet Plateau, China, between April 2011 and October 2013. Soil was collected in the middle of each month and analyzed for water content, microbial biomass C (MBC) and N (MBN), dissolved organic C and N, and inorganic N. Soil microbial community composition was measured by the dilution-plate method. Fungi and actinomycetes dominated the microbial community during the nongrowing seasons, and the proportion of bacteria increased considerably during the early growing seasons. Trends of consistently increasing MBC and available N pools were observed during the nongrowing seasons. MBC sharply declined during soil thaw and was accompanied by a peak in available N pool. Induced by changes in soil temperatures, significant shifts in the structures and functions of microbial communities were observed during the winter-spring transition and largely contributed to microbial reduction. The divergent seasonal dynamics of different N forms showed a complementary nutrient supply pattern during the growing season. Similarities between the interannual dynamics of microbial biomass and available N pools were observed, and soil temperature and water conditions were the primary environmental factors driving interannual fluctuations. Owing to the changes in climate, seasonal soil microbial activities and nutrient supply patterns are expected to change further, and these changes may have crucial implications for the productivity and biodiversity of alpine ecosystems.

Filocrono em batateira afetado pelo tamanho do tubérculo-semente e pela época de cultivo Phyllocrono in potato affected by tuber-seed size and growing season

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Nereu Augusto Streck

2009-01-01

Full Text Available O objetivo deste trabalho foi estimar o filocrono de plantas de batata da cultivar Asterix oriundas de diferentes tamanhos de tubérculos-semente, em duas épocas de cultivo em campo utilizando o conceito de graus-dia para o cálculo do filocrono. O experimento foi desenvolvido em Santa Maria (RS, na primavera de 2003 e no outono de 2004. Foram usados quatro tamanhos de tubérculos-semente da cultivar de batata Asterix: entre 2 e 4 cm, 4 e 6 cm, 6 e 8 cm e 8 e 10 cm. O filocrono (ºC dia folha-1 foi estimado pelo inverso do coeficiente angular da relação entre número de folhas na haste principal e a soma térmica calculada por três métodos: método 1 - considera apenas a temperatura base; método 2 - considera a temperatura base e a temperatura ótima, e método 3 - considera a temperatura base, a temperatura ótima e a temperatura máxima. O tamanho do tubérculo-semente não afetou o filocrono, mas o método de cálculo da soma térmica e a época de cultivo afetaram o filocrono da batateira cultivar Asterix. No método de cálculo da soma térmica a ser usado no filocrono da batateira cultivar Asterix, recomenda-se usar a temperatura base e a temperatura ótima, pois com este método, o filocrono foi similar entre as épocas de cultivo.The objective of this study was to estimate the phyllochron of the potato cultivar Asterix in plants derived from different tuber seed sizes in two field growing seasons using the concept of degrees-days for calculating the phyllochron. The experiment was conducted in Santa Maria, RS, during Spring 2003 and Fall 2004. Four classes of tuber-seed diameter of the potato cultivar Asterix were used: 2-4 cm, 4-6 cm, 6-8 cm and 8-10 cm. The phyllochron was estimated as the inverse of the slope of the linear regression of main stem leaves number against the thermal time calculated with three methods: method 1 - considering only the base temperature, method 2 - considering the base temperature and the optimum

Seasonal dynamics of nitrate and ammonium ion concentrations in soil solutions collected using MacroRhizon suction cups.

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Kabala, Cezary; Karczewska, Anna; Gałka, Bernard; Cuske, Mateusz; Sowiński, Józef

2017-07-01

The aims of the study were to analyse the concentration of nitrate and ammonium ions in soil solutions obtained using MacroRhizon miniaturized composite suction cups under field conditions and to determine potential nitrogen leaching from soil fertilized with three types of fertilizers (standard urea, slow-release urea, and ammonium nitrate) at the doses of 90 and 180 kg ha -1 , applied once or divided into two rates. During a 3-year growing experiment with sugar sorghum, the concentration of nitrate and ammonium ions in soil solutions was the highest with standard urea fertilization and the lowest in variants fertilized with slow-release urea for most of the months of the growing season. Higher concentrations of both nitrogen forms were noted at the fertilizer dose of 180 kg ha -1 . One-time fertilization, at both doses, resulted in higher nitrate concentrations in June and July, while dividing the dose into two rates resulted in higher nitrate concentrations between August and November. The highest potential for nitrate leaching during the growing season was in July. The tests confirmed that the miniaturized suction cups MacroRhizon are highly useful for routine monitoring the concentration of nitrate and ammonium ions in soil solutions under field conditions.

Toward the definition of a carbon budget model: seasonal variation and temperature effect on respiration rate of vegetative and reproductive organs of pistachio trees (Pistacia vera).

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Marra, Francesco P; Barone, Ettore; La Mantia, Michele; Caruso, Tiziano

2009-09-01

This study, as a preliminary step toward the definition of a carbon budget model for pistachio trees (Pistacia vera L.), aimed at estimating and evaluating the dynamics of respiration of vegetative and reproductive organs of pistachio tree. Trials were performed in 2005 in a commercial orchard located in Sicily (370 m a.s.l.) on five bearing 20-year-old pistachio trees of cv. Bianca grafted onto Pistachio terebinthus L. Growth analyses and respiration measurements were done on vegetative (leaf) and reproductive (infructescence) organs during the entire growing season (April-September) at biweekly intervals. Results suggested that the respiration rates of pistachio reproductive and vegetative organs were related to their developmental stage. Both for leaf and for infructescence, the highest values were observed during the earlier stages of growth corresponding to the phases of most intense organ growth. The sensitivity of respiration activity to temperature changes, measured by Q(10), showed an increase throughout the transition from immature to mature leaves, as well as during fruit development. The data collected were also used to estimate the seasonal carbon loss by respiration activity for a single leaf and a single infructescence. The amount of carbon lost by respiration was affected by short-term temperature patterns, organ developmental stage and tissue function.

Effects of a short-term pre-season training programme on the body composition and anaerobic performance of professional rugby union players.

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Argus, Christos K; Gill, Nicholas; Keogh, Justin; Hopkins, Will G; Beaven, C Martyn

2010-04-01

Pre-season rugby training develops the physical requisites for competition and consists of a high volume of resistance training and anaerobic and aerobic conditioning. However, the effects of a rugby union pre-season in professional athletes are currently unknown. Therefore, the purpose of this investigation was to determine the effects of a 4-week pre-season on 33 professional rugby union players. Bench press and box squat increased moderately (13.6 kg, 90% confidence limits +/-2.9 kg and 17.6 +/- 8.0 kg, respectively) over the training phase. Small decreases in bench throw (70.6 +/- 53.5 W), jump squat (280.1 +/- 232.4 W), and fat mass (1.4 +/- 0.4 kg) were observed. In addition, small increases were seen in fat-free mass (2.0 +/- 0.6 kg) and flexed upper-arm girth (0.6 +/- 0.2 cm), while moderate increases were observed in mid-thigh girth (1.9 +/- 0.5 cm) and perception of fatigue (0.6 +/- 0.4 units). Increases in strength and body composition were observed in elite rugby union players after 4 weeks of intensive pre-season training, but this may have been the result of a return to fitness levels prior to the off-season. Decreases in power may reflect high training volumes and increases in perceived of fatigue.

Association with humans and seasonality interact to reverse predictions for animal space use.

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Laver, Peter N; Alexander, Kathleen A

2018-01-01

Variation in animal space use reflects fitness trade-offs associated with ecological constraints. Associated theories such as the metabolic theory of ecology and the resource dispersion hypothesis generate predictions about what drives variation in animal space use. But, metabolic theory is usually tested in macro-ecological studies and is seldom invoked explicitly in within-species studies. Full evaluation of the resource dispersion hypothesis requires testing in more species. Neither have been evaluated in the context of anthropogenic landscape change. In this study, we used data for banded mongooses ( Mungos mungo ) in northeastern Botswana, along a gradient of association with humans, to test for effects of space use drivers predicted by these theories. We used Bayesian parameter estimation and inference from linear models to test for seasonal differences in space use metrics and to model seasonal effects of space use drivers. Results suggest that space use is strongly associated with variation in the level of overlap that mongoose groups have with humans. Seasonality influences this association, reversing seasonal space use predictions historically-accepted by ecologists. We found support for predictions of the metabolic theory when moderated by seasonality, by association with humans and by their interaction. Space use of mongooses living in association with humans was more concentrated in the dry season than the wet season, when historically-accepted ecological theory predicted more dispersed space use. Resource richness factors such as building density were associated with space use only during the dry season. We found negligible support for predictions of the resource dispersion hypothesis in general or for metabolic theory where seasonality and association with humans were not included. For mongooses living in association with humans, space use was not associated with patch dispersion or group size over both seasons. In our study, living in association

Seasonality of reproduction and production in farm fishes, birds and mammals.

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Chemineau, P; Malpaux, B; Brillard, J P; Fostier, A

2007-03-01

A very large majority of farm animals express seasonal variations in their production traits, thus inducing seasonal availability of fresh derived animal products (meat, milk, cheese and eggs). This pattern is in part the consequence of the farmer's objective to market his products in the most economically favourable period. It may also be imposed by the season-dependent access to feed resources, as in ruminants, or by the specific requirements derived from adaptation to environmental conditions such as water temperature in fish. But seasonal variations in animal products are also the consequence of constraints resulting from the occurrence of a more or less marked seasonal reproductive season in most farm animal species including fish, poultry and mammals. Like their wild counterparts, at mid and high latitudes, most farm animals normally give birth at the end of winter-early spring, the most favourable period for the progeny to survive and thus promote the next generation. As a consequence, most species show seasonal variations in their ovulation frequency (mammals and fish: presence or absence of ovulation; birds: variations or suppression of laying rates), spermatogenic activity (from moderate to complete absence of sperm production), gamete quality (variations in fertilisation rates and embryo survival), and also sexual behaviour. Among species of interest for animal production, fishes and birds are generally considered as more directly sensitive to external factors (mainly temperature in fish, photoperiod in birds). In all species, it is therefore advisable that artificial photoperiodic treatments consisting of extra-light during natural short days (in chickens, turkeys, guinea fowl, sheep and goats) or melatonin during long days (in goats, sheep) be extensively used to either adjust the breeding season to animal producer needs and/or to completely overcome seasonal variations of sperm production in artificial insemination centres (mammals) and breeder flock

Seasonal and episodic moisture controls on plant and microbial contributions to soil respiration.

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Carbone, Mariah S; Still, Christopher J; Ambrose, Anthony R; Dawson, Todd E; Williams, A Park; Boot, Claudia M; Schaeffer, Sean M; Schimel, Joshua P

2011-09-01

Moisture inputs drive soil respiration (SR) dynamics in semi-arid and arid ecosystems. However, determining the contributions of root and microbial respiration to SR, and their separate temporal responses to periodic drought and water pulses, remains poorly understood. This study was conducted in a pine forest ecosystem with a Mediterranean-type climate that receives seasonally varying precipitation inputs from both rainfall (in the winter) and fog-drip (primarily in the summer). We used automated SR measurements, radiocarbon SR source partitioning, and a water addition experiment to understand how SR, and its separate root and microbial sources, respond to seasonal and episodic changes in moisture. Seasonal changes in SR were driven by surface soil water content and large changes in root respiration contributions. Superimposed on these seasonal patterns were episodic pulses of precipitation that determined the short-term SR patterns. Warm season precipitation pulses derived from fog-drip, and rainfall following extended dry periods, stimulated the largest SR responses. Microbial respiration dominated these SR responses, increasing within hours, whereas root respiration responded more slowly over days. We conclude that root and microbial respiration sources respond differently in timing and magnitude to both seasonal and episodic moisture inputs. These findings have important implications for the mechanistic representation of SR in models and the response of dry ecosystems to changes in precipitation patterns.

Seasonal and clonal variation in cellulose microfibril orientation during cell wall formation of tracheids in Cryptomeria japonica.

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Jyske, Tuula; Fujiwara, Takeshi; Kuroda, Katsushi; Iki, Taiichi; Zhang, Chunhua; Jyske, Tuomas K; Abe, Hisashi

2014-08-01

To investigate the biological mechanism by which trees control the changes in microfibril (MF) orientation among secondary cell wall layers of conifer tracheids, we studied seasonal variation in the orientation of newly deposited MFs during tracheid cell wall development in Japanese cedar (Cryptomeria japonica D. Don) trees growing in Central Japan (36°36'N, 140°39'E). Sample blocks were repeatedly collected from four 16-year-old clones of different origins during the growing season of 2010 to investigate the hypotheses that changes in cellulose MF orientation between wall layers exhibited seasonal and clonal differences. The progressive change in the orientation of newly deposited MFs on the primary and secondary cell wall layers of tracheids was detected by field-emission-scanning electron microscopy. Tracheid production and differentiation was studied by light microscopy. We observed a decreasing trend in the orientation of deposited MFs from earlywood to latewood in the S2 and S1 layers, where MFs appeared in a Z-helix. In contrast, no seasonal pattern in the orientation of the MFs in the S-helix was observed. Minor clonal variation was observed in the phenology of tracheid production and differentiation. We concluded that a seasonal decreasing trend in the orientation of the MFs in the Z-helix in S1 and S2 was present, whereas the MFs in other layers exhibited minor random variations. Thus, the orientation of the MFs in S2 was affected by seasonal factors, whereas the MFs in other layers were more intrinsically controlled. The within-ring variations in the MF orientation and thus the resulting average MF angle might also be related to genotypic differences in the tracheid production and differentiation rate. However, our results do not exclude other intrinsic and environmental regulations in the change in MF orientation, which remains a topic for future studies. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions

A data assimilation framework for constraining upscaled cropland carbon flux seasonality and biometry with MODIS

Directory of Open Access Journals (Sweden)

O. Sus

2013-04-01

Full Text Available Agroecosystem models are strongly dependent on information on land management patterns for regional applications. Land management practices play a major role in determining global yield variability, and add an anthropogenic signal to the observed seasonality of atmospheric CO2 concentrations. However, there is still little knowledge on spatial and temporal variability of important farmland activities such as crop sowing dates, and thus these remain rather crudely approximated within carbon cycle studies. In this study, we present a framework allowing for spatio-temporally resolved simulation of cropland carbon fluxes under observational constraints on land management and canopy greenness. We apply data assimilation methodology in order to explicitly account for information on sowing dates and model leaf area index. MODIS 250 m vegetation index data were assimilated both in batch-calibration for sowing date estimation and sequentially for improved model state estimation, using the ensemble Kalman filter (EnKF, into a crop carbon mass balance model (SPAc. In doing so, we are able to quantify the multiannual (2000–2006 regional carbon flux and biometry seasonality of maize–soybean crop rotations surrounding the Bondville Ameriflux eddy covariance site, averaged over 104 pixel locations within the wider area. (1 Validation at the Bondville site shows that growing season C cycling is simulated accurately with MODIS-derived sowing dates, and we expect that this framework allows for accurate simulations of C cycling at locations for which ground-truth data are not available. Thus, this framework enables modellers to simulate current (i.e. last 10 yr carbon cycling of major agricultural regions. Averaged over the 104 field patches analysed, relative spatial variability for biometry and net ecosystem exchange ranges from ∼7% to ∼18%. The annual sign of net biome productivity is not significantly different from carbon neutrality. (2 Moreover

Environmental controls of daytime leaf carbon exchange: Implications for estimates of ecosystem fluxes in a deciduous forest

Science.gov (United States)

Heskel, M.; Tang, J.

2017-12-01

Leaf-level photosynthesis and respiration are sensitive to short- and long-term changed in temperature, and how these processes respond to phenological and seasonal transitions and daily temperature variation dictate how carbon is first assimilated and released in terrestrial ecosystems. We examined the short-term temperature response of daytime leaf carbon exchange at Harvard Forest across growing season, with the specific objective to quantify the light inhibition of dark respiration and photorespiration in leaves and use this to better inform daytime carbon assimilation and efflux estimates at the canopy scale. Dark and light respiration increased with measurement temperature and varied seasonally in a proportional manner, with the level of inhibition remaining relatively constant through the growing season. Higher rates of mitochondrial respiration and photorespiration at warmer temperatures drove a lower carbon use efficiency. Using temperature, light, and canopy leaf area index values to drive models, we estimate partitioned ecosystem fluxes and re-calculate gross primary production under multiple scenarios that include and exclude the impact of light inhibition, thermal acclimation, and seasonal variation in physiology. Quantifying the contribution of these `small fluxes' to ecosystem carbon exchange in forests provides a nuanced approach for integrating physiology into regional model estimates derived from eddy covariance and remote-sensing methods.

Can reduced stocking rates and natural forage utilization produce market sized catfish from fingerlings in one growing season

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The purpose of this study was to determine the feasibility of growing marketable channel catfish Ictalurus punctatus from pond-run fingerlings (15.9 g/fish) using low stocking densities (7,413 or 14,826 fish/ha) and electrified bug lights to enhance natural forage available to fish. Even at low sto...

Extending to seasonal scales the current usage of short range weather forecasts and climate projections for water management in Spain

Science.gov (United States)

Rodriguez-Camino, Ernesto; Voces, José; Sánchez, Eroteida; Navascues, Beatriz; Pouget, Laurent; Roldan, Tamara; Gómez, Manuel; Cabello, Angels; Comas, Pau; Pastor, Fernando; Concepción García-Gómez, M.°; José Gil, Juan; Gil, Delfina; Galván, Rogelio; Solera, Abel

2016-04-01

This presentation, first, briefly describes the current use of weather forecasts and climate projections delivered by AEMET for water management in Spain. The potential use of seasonal climate predictions for water -in particular dams- management is then discussed more in-depth, using a pilot experience carried out by a multidisciplinary group coordinated by AEMET and DG for Water of Spain. This initiative is being developed in the framework of the national implementation of the GFCS and the European project, EUPORIAS. Among the main components of this experience there are meteorological and hydrological observations, and an empirical seasonal forecasting technique that provides an ensemble of water reservoir inflows. These forecasted inflows feed a prediction model for the dam state that has been adapted for this purpose. The full system is being tested retrospectively, over several decades, for selected water reservoirs located in different Spanish river basins. The assessment includes an objective verification of the probabilistic seasonal forecasts using standard metrics, and the evaluation of the potential social and economic benefits, with special attention to drought and flooding conditions. The methodology of implementation of these seasonal predictions in the decision making process is being developed in close collaboration with final users participating in this pilot experience.

Effect of Nigella sativa or Curcumin on Daily Body Weight Gain, Feed Intake and some Physiological Functions in Growing Zaraibi Goats during Hot Summer Season

International Nuclear Information System (INIS)

Habeeb, A.A.M.; El-Tarabany, A.A.

2012-01-01

Twenty one Zaraibi kids, aged 4-5 months and weighed on average 9.5 ±0.2 kg were divided into three groups, seven kids in each. The experiment was beginning after the end of weaning period and lasted 5 months (May, June, July, August and September). Kids in the 1st group were fed the basal ration (concentrate feed mixture plus Barseem hay without additives (Control), while those in the 2nd and 3rd groups were fed the same basal ration supplemented daily with crushed 2 gram from Nigella or Curcumin per one kg CFM, respectively. Nigella sativa (Nigella) and Curcumin addition to the diet of kids during months of the hot summer season comparison with control group improved significantly the final LBW at the end of 5 months by 5.56 and 4.8 kg and increased significantly average daily body gain (DBG) of kids by 62.2 and 54.25 g, respectively. Supplementation improved the animal immunity function i.e. total protein and globulin concentrations as well as thyroid hormonal levels (T4 and T3) and decreased the factor related to heart disease (total cholesterol and total lipids), glucose and cortisol levels in the blood plasma. At the same time, liver and kidney functions were not affected negatively by supplementation either with Nigella or Curcumin. Supplementation the diet of growing goats increased also significantly the Hb values and RBC'S count as well as the concentrations of Na, K, and Pi.

Growing media [Chapter 5

Science.gov (United States)

Douglass F. Jacobs; Thomas D. Landis; Tara Luna

2009-01-01

Selecting the proper growing medium is one of the most important considerations in nursery plant production. A growing medium can be defined as a substance through which roots grow and extract water and nutrients. In native plant nurseries, a growing medium can consist of native soil but is more commonly an "artificial soil" composed of materials such as peat...

Effects of Altered Seasonality of Precipitation on Grass Production and Grasshopper Performance in a Northern Mixed Prairie.

Science.gov (United States)

Branson, David H

2017-06-01

Climatic changes are leading to differing patterns and timing of precipitation in grassland ecosystems, with the seasonal timing of precipitation affecting plant biomass and plant composition. No previous studies have examined how drought seasonality affects grasshopper performance and the impact of herbivory on vegetation. We modified seasonal patterns of precipitation and grasshopper density in a manipulative experiment to examine if seasonality of drought combined with herbivory affected plant biomass, nitrogen content, and grasshopper performance. Grass biomass was affected by both precipitation and grasshopper density treatments, while nitrogen content of grass was higher with early-season drought. Proportional survival was negatively affected by initial density, while survival was higher with early drought than with full-season drought. Drought timing affected the outcome, with early summer drought increasing grass nitrogen content and grasshopper survival, while season-long and late-season drought did not. The results support arguments that our knowledge of plant responses to seasonal short-term variation in climate is limited and illustrate the importance of experiments manipulating precipitation phenology. The results confirm that understanding the season of drought is critical for predicting grasshopper population dynamics, as extreme early summer drought may be required to strongly affect Melanoplus sanguinipes (F.) performance. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by US Government employees and is in the public domain in the US.

Simulated sensitivity of African terrestrial ecosystem photosynthesis to rainfall frequency, intensity, and rainy season length

Science.gov (United States)

Guan, Kaiyu; Good, Stephen P.; Caylor, Kelly K.; Medvigy, David; Pan, Ming; Wood, Eric F.; Sato, Hisashi; Biasutti, Michela; Chen, Min; Ahlström, Anders; Xu, Xiangtao

2018-02-01

There is growing evidence of ongoing changes in the statistics of intra-seasonal rainfall variability over large parts of the world. Changes in annual total rainfall may arise from shifts, either singly or in a combination, of distinctive intra-seasonal characteristics -i.e. rainfall frequency, rainfall intensity, and rainfall seasonality. Understanding how various ecosystems respond to the changes in intra-seasonal rainfall characteristics is critical for predictions of future biome shifts and ecosystem services under climate change, especially for arid and semi-arid ecosystems. Here, we use an advanced dynamic vegetation model (SEIB-DGVM) coupled with a stochastic rainfall/weather simulator to answer the following question: how does the productivity of ecosystems respond to a given percentage change in the total seasonal rainfall that is realized by varying only one of the three rainfall characteristics (rainfall frequency, intensity, and rainy season length)? We conducted ensemble simulations for continental Africa for a realistic range of changes (-20% ~ +20%) in total rainfall amount. We find that the simulated ecosystem productivity (measured by gross primary production, GPP) shows distinctive responses to the intra-seasonal rainfall characteristics. Specifically, increase in rainfall frequency can lead to 28% more GPP increase than the same percentage increase in rainfall intensity; in tropical woodlands, GPP sensitivity to changes in rainy season length is ~4 times larger than to the same percentage changes in rainfall frequency or intensity. In contrast, shifts in the simulated biome distribution are much less sensitive to intra-seasonal rainfall characteristics than they are to total rainfall amount. Our results reveal three major distinctive productivity responses to seasonal rainfall variability—‘chronic water stress’, ‘acute water stress’ and ‘minimum water stress’ - which are respectively associated with three broad spatial patterns of