Decrease In Mean Annual Precipitation Research Articles

Investigating a Century of Rainfall: The Impact of Elevation on Precipitation Changes (Northern Tuscany, Italy)

Precipitation is crucial for water resource renewal, but climate change alters their frequency and amounts, challenging societies for correct and effective water management. However, modifications of precipitation dynamics appear to be not uniformly distributed, both in space and time. Even in relatively small areas, precipitation shows the coexistence of positive and negative trends. Local topography seems to be a strong driver of precipitation changes. Understanding precipitation changes and their relationship with local topography is crucial for society’s resilience. Taking advantage of a dense and long-lasting (1920–2019) meteorological monitoring network, we analyzed the precipitation changes over the last century in a sensitive and strategic area in the Mediterranean hotspot. The study area corresponds to northern Tuscany (Italy), where its topography comprises mountain ridges and coastal and river plains. Forty-eight rain gauges were selected with continuous annual precipitation time series. These were analyzed for trends and differences in mean annual precipitation between the stable period of 1921–1970 and the last 30-year 1990–2019. The relationship between precipitation changes and local topography was also examined. The results show the following highlights: (i) A general decrease in precipitation was found through the century, even if variability is marked. (ii) The mountain ridges show the largest decrease in mean annual precipitation. (iii) The precipitation change entity over the last century was not homogenous and was dependent on topography and geographical setting. (iv) A decrease in annual precipitation of up to 400 mm was found for the mountainous sites.

Biochar effects on crop yield variability

Context or ProblemNumerous studies have demonstrated that biochar application can increase crop yield by improving soil properties and health. Yet, these studies, however, neglected how biochar alters yield variability across years – reflecting the yield stability. Objective or Research questionThis study aimed to investigate the effects of biochar application on crop yield variability. MethodsPublished data from 38 experimental sites were collected from the Web-of-Science. Two-thirds of the data were originated from three main staple crops: maize, wheat, and rice. The remaining were from rapeseed, soybean, sweet potato, and peppermint. Biochar effects on crop yield and its variability as well as their driving factors were analyzed by linear mixed models depending on soil conditions, field management practices, and climate types. ResultsBiochar increased the crop yield globally by 14 %, especially in soils with low pH (< 5.5), low nitrogen (N) and phosphorus (P) inputs (≤ 120 kg N ha−1, < 35 kg P ha−1), with high biochar inputs (≥ 20 Mg ha−1), and under crop rotation. Biochar increased crop yields by 12 % in short-term (≤ 5 years) and 21 % in long-term (> 5 years) experiments. Biochar increased yield variability by 42 % in acidic soils (pH < 5.5) and by 24 % with low N inputs (≤ 120 kg N ha−1), mainly because its liming and fertilization effects were short-lasting within the first few years. The yield variability after biochar application decreased with the increase in mean annual temperature, inter-annual variabilities of temperature and precipitation, but with the decrease in mean annual precipitation in the growing season. Yield variability under biochar increased in short-term experiments by 27 %, but there was no change (0 %) in long-term experiments because of the higher yield gains and resistance to fluctuating weather conditions. Therefore, crop yield variability decreased with increasing yield in long-term experiments. ConclusionsBiochar application increased short-term variability of crop yields, but its long-term variability remained unaffected. Implications or SignificanceThis study highlights that biochar can support steadily future crop production in the long run.

Integrated hydrological modeling and water resource assessment in the Mayurakshi River Basin: A comprehensive study from historical data to future predictions

This study employs the SWAT hydrologic model to integrate climatological and hydrological processes for an in-depth analysis of the Mayurakshi River Basin. Utilizing the Markov Chain Model, the study evaluates water availability, flow patterns, and the basin's response to various climatic and land-use scenarios. Over 30 years of daily observed river discharge data were rigorously calibrated, validated, and analyzed for uncertainty, with critical data from the Massanjore Dam and Tilpara Barrage gauge stations characterizing the river's hydrological behavior. The result suggests the watershed received an average annual precipitation of 1432.4 mm, with evapotranspiration accounting for 40% of total water loss (578.4 mm). Surface runoff constituted over 90% of the total discharge, highlighting its importance for agricultural practices, particularly during the dry season. However future projections (2021-2031) indicate a significant decrease in mean annual precipitation (1404.7 mm) and a drop in evapotranspiration (542.1 mm or 38% of mean precipitation), attributed to reduced vegetation cover and increased settlement, leading to enhanced surface runoff. By quantifying internal renewable blue water, evapotranspiration, and soil water, this research provides crucial data for long-term water resource planning and assessment. The findings are valuable for national, regional, and transboundary water management agencies, offering insights into sustainable water resource management under changing climatic and different land-use conditions.

The Spatio-Temporal Dynamics of Water Resources (Rainfall and Snow) in the Sierra Nevada Mountain Range (Southern Spain)

This paper describes the use of a unique spatio-temporally resolved precipitation and temperature dataset to assess the spatio-temporal dynamics of water resources over a period of almost seven decades across the Sierra Nevada mountain range, which is the most southern Alpine environment in Europe. The altitude and geographical location of this isolated alpine environment makes it a good detector of climate change. The data were generated by applying geostatistical co-kriging to significant instrumental precipitation and temperature (minimum, maximum and mean) datasets. The correlation between precipitation and altitude was not particularly high and the statistical analysis yielded some surprising results in the form of mean annual precipitation maps and yearly precipitation time series. These results confirm the importance of orographic precipitation in the Sierra Nevada mountain range and show a decrease in mean annual precipitation of 33 mm per decade. Seasonality, however, has remained constant throughout the period of the study. The results show that previous studies have overestimated the altitudinal precipitation gradient in the Sierra Nevada and reveal its complex spatial variability. In addition, the results show a clear correspondence between the mean annual precipitation and the NAO index and, to a much lesser extent, the WeMO index. With respect to temperature, there is a high correlation between minimum temperature and altitude (coefficient of correlation = −0.84) and between maximum temperature and altitude (coefficient of correlation = −0.9). Thus, our spatial temperature maps were very similar to topographic maps, but the temporal trend was complex, with negative (decreasing) and positive (increasing) trends. A dynamic model of snowfall can be obtained by using the degree-day methodology. These results should be considered when checking the local performance of climatological models.

Effects of land use and climate on carbon and nitrogen pool partitioning in European mountain grasslands

European mountain grasslands are increasingly affected by land-use changes and climate, which have been suggested to exert important controls on grassland carbon (C) and nitrogen (N) pools. However, so far there has been no synthetic study on whether and how land-use changes and climate interactively affect the partitioning of these pools amongst the different grassland compartments. We analyzed the partitioning of C and N pools of 36 European mountain grasslands differing in land-use and climate with respect to above- and belowground phytomass, litter and topsoil (top 23 cm). We found that a reduction of management intensity and the abandonment of hay meadows and pastures increased above-ground phytomass, root mass and litter as well as their respective C and N pools, concurrently decreasing the fractional contribution of the topsoil to the total organic carbon pool. These changes were strongly driven by the cessation of cutting and grazing, a shift in plant functional groups and a related reduction in litter quality. Across all grasslands studied, variation in the impact of land management on the topsoil N pool and C/N-ratio were mainly explained by soil clay content combined with pH. Across the grasslands, below-ground phytomass as well as phytomass- and litter C concentrations were inversely related to the mean annual temperature; furthermore, C/N-ratios of phytomass and litter increased with decreasing mean annual precipitation. Within the topsoil compartment, C concentrations decreased from colder to warmer sites, and increased with increasing precipitation. Climate generally influenced effects of land use on C and N pools mainly through mean annual temperature and less through mean annual precipitation. We conclude that site-specific conditions need to be considered for understanding the effects of land use and of current and future climate changes on grassland C and N pools.

酸雨对中国陆地生态系统土壤呼吸影响的整合分析

PDF HTML阅读 XML下载 导出引用 引用提醒 酸雨对中国陆地生态系统土壤呼吸影响的整合分析 DOI: 10.5846/stxb202110202959 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31901296）；广东省基础与应用基础研究基金项目（2021A1515010652）；广州市基础研究计划项目（202102020289） Effects of acid rain on soil respiration in Chinese terrestrial ecosystems: A meta-analysis Author: Affiliation: Fund Project: This work was supported by the National Natural Science Foundation of China (31901296), the Guangdong Basic and Applied Basic Research Foundation (2021A1515010652), and the Guangzhou Basic Research Program (2021000031). 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:通过整合分析（Meta-analysis）国内外公开发表的81篇模拟酸雨实验论文的2683条有效观测数据，量化了酸雨对中国3个主要陆地生态系统（森林、草地和农田）土壤呼吸（Rs）及其组分（自养呼吸（Ra）、异养呼吸（Rh））的影响。结果表明，酸雨显著降低了Rs （-9.6%）、Rh （-7.7%）和Ra （-11.7%）；酸雨pH越低，Rs及其组分的降幅越大；野外实验对Rh和Ra的负效应大于温室实验。酸雨对Rs的负效应在农田最大（-14.7%），草地次之（-10.8%），森林最小（-8.0%）；森林Rh、Ra对酸雨的响应与Rs一致，不同林型间差异不显著；草地Rh和Ra在酸雨处理下分别显著降低和增加。Rs、Rh与土壤pH显著正相关，与土壤有机碳（SOC）显著负相关；Rh和Ra分别与地上和地下生物量显著正相关。酸雨对Rs和Ra的负效应随纬度的增加而减弱，随年平均温的升高而增强，对Rs的正效应随年平均降水的降低而增强。研究表明，酸雨不仅降低了土壤pH，抑制了植物生长，减少了植物向土壤的碳输入，还降低了微生物活性，减少了Rh，导致SOC分解降低，因而未显著改变土壤碳库。研究结果将为全球变化背景下我国陆地生态系统的碳预算提供科学借鉴。 Abstract:Anthropogenic activities over the last four decades have increased depositions of sulfur dioxide (SO2) and nitrogen oxides (NOx) by three to five fold in China, which resulted in a serious problem of acid rain with adverse effects on terrestrial carbon cycle. Soil respiration (Rs) as the second largest flux for the most terrestrial carbon cycle, and its two components (i.e., autotrophic respiration (Ra) and heterotrophic respiration (Rh)) are extremely sensitive to anthropogenic acid rain due to its detrimental effects on plant growth and soil microbes. Although numerous ecosystem-level manipulative experiments were conducted to explore the underlying mechanisms how acid rain affected Rs, a quantitative synthesis of previous studies on the effects of acid rain on Rs and its two components across different terrestrial ecosystems was scarce. By conducting a meta-analysis of 2683 observations from 81 independent experimental studies, we quantified the directions and magnitudes of the responses of Rs, Ra, and Rh to simulated acid rain (SAR) in three major terrestrial ecosystems (i.e., forest, grassland, farmland) in China. Across all the experimental studies, our results showed that SAR significantly reduced Rs (-9.6%), Rh (-11.7%) and Ra (-11.7%), and the degree of reduction was proportional to the pH of SAR. The negative effects of SAR on Rh and Ra were greater in field experiment than that in pot experiment due to the differences in the intensity of SAR and experimental duration. Among different terrestrial ecosystem types, the negative effect of SAR on Rs was the most negative in farmland ecosystems (-14.7%), followed by grassland (-10.8%) and forest (-8.0%) ecosystems. The responses of Rh and Ra to SAR in forest ecosystems were consistent with that of Rs, and there were no significant differences among different forest types (i.e., coniferous forest, coniferous and broadleaved mixed forest and broadleaved forest). In grassland ecosystems, the response to SAR was negative for Rh, but positive for Ra. Linear-regression analysis showed that Rs and Rh were positively correlated with soil pH, but negatively correlated with soil organic carbon (SOC). Rh and Ra were positively correlated with aboveground biomass (AGB) and belowground biomass (BGB), respectively. Meta-regression analysis indicated that the negative effects of SAR on Rs and Ra were decreased with the increase of latitude, and increased with the increase of mean annual temperature (MAT), whereas the positive effect of SAR on Rs increased with a decrease in mean annual precipitation (MAP). Based on this meta-analysis, we found that SAR not only reduced soil pH, inhibited plant growth, and thus reduced plant carbon input to soil, but also inhibited microbial activities, reduced Rh, and SOC decomposition rate. Therefore, anthropogenic acid rain significantly altered the input and output of SOC, but did not significantly change the content of SOC in terrestrial ecosystems. These results will provide scientific basis for assessing the carbon budget of the Chinese terrestrial ecosystems in response to global change. 参考文献 相似文献 引证文献

Spatiotemporal partitioning of savanna plant functional type productivity along NATT

Realistic representations and simulation of mass and energy exchanges across heterogeneous landscapes can be a challenge in land surface and dynamic vegetation models. For mixed life-form biomes such as savannas, plant function is very difficult to parameterise due to the distinct physiological characteristics of tree and grass plant functional types (PFTs) that vary dramatically across space and time. The partitioning of their fractional contributions to ecosystem gross primary production (GPP) remains to be achieved at regional scale using remote sensing. The objective of this study was to partition savanna gross primary production (GPP) into tree and grass functional components based on their distinctive phenological characteristics. Comparison of the remote sensing partitioned GPPtree and GPPgrass against field measurements from eddy covariance (EC) towers showed an overall good agreement in terms of both GPP seasonality and magnitude. We found total GPP, as well as its tree and grass components, decreased dramatically with rainfall over the North Australian Tropical Transect (NATT), from the Eucalyptus forest and woodland in the northern humid coast to the grasslands, Acacia woodlands and shrublands in the southern xeric interior. Spatially, GPPtree showed a steeper decrease with precipitation along the NATT compared to GPPgrass, thus tree/grass GPP ratios also decreased from the northern mesic region to the arid south region of the NATT. However, results also showed a second trend at the southern part of the transect, where tree-grass ratios and total GPP increased with decreasing mean annual precipitation, and this occurred in the physiognomic transition from hummock grasslands to Acacia woodland savannas. Total GPP and tree-grass GPP ratios across climate extremes were found to be primarily driven by grass layer response to rainfall dynamics. The grass-containing xeric savannas exhibited a higher hydroclimatic sensitivity, whereas GPP in the northern mesic savannas was fairly stable across years despite large variations in rainfall amount. The pronounced spatiotemporal variations in savanna vegetation productivity encountered along the NATT study area suggests that the savanna biome is particularly sensitive and vulnerable to predicted future climate change and hydroclimatic variability.

Evaluating drought-induced mortality risk for Robinia pseudoacacia plantations along the precipitation gradient on the Chinese Loess Plateau

Extensive afforestation with exotic species like Robinia pseudoacacia on the Chinese Loess Plateau are facing high drought-induced mortality risk due to the large fluctuations in annual precipitation and severe soil desiccation. The aim of this study was to assess the risk of drought-induced mortality for R. pseudoacacia plantations on the Loess Plateau based on plant hydraulics. We modified the routines of soil-plant-atmosphere water transfer in the Biome BioGeochemistry model (Biome-BGC) using a plant hydraulic model based on the supply-demand theory. The modified model efficiently captured the dynamics of canopy transpiration, soil moisture, leaf water potential, and regional variation in leaf area index in R. pseudoacacia stands on the Loess Plateau. We simulated the 50-year (1968–2017) plant hydraulic dynamics at 14 sites along a precipitation gradient on the Loess Plateau. The results indicated that annual average percentage loss of whole-plant hydraulic conductance (APLK) showed strong temporal variation due to climatic variability, which was positively correlated with annual potential evapotranspiration (PET) and the aridity index (the ratio of PET to annual precipitation). Along the precipitation gradient, the maximum APLK increased linearly with decreasing mean annual precipitation (MAP) and could exceed 60% at sites with MAP <446.1 mm. The sustainable growth of R. pseudoacacia plantations at these sites would face a severe threat. We analyzed the effect of soil desiccation on drought-induced mortality risk further. Soil desiccation increased the sensitivity of plant hydraulic safety to precipitation variability considerably, and the effect was more significant in areas with lower MAP. These quantitative findings should be helpful for evaluating and promoting the sustainability of plantation forests on the Loess Plateau.

Projected precipitation changes over the south Asian region for every 0.5 °C increase in global warming

Using all ensemble members of NCAR CCSM4 for historical natural, RCP4.5 and RCP8.5 scenarios from CMIP5, we analyse changes in mean and extreme precipitation over the south Asian region for every 0.5 oC increase in global warming. An increase in mean annual precipitation is projected over majority of the south Asian region with increased levels of warming. Over Indian land, the spatially-averaged annual mean precipitation shows an increase in the range of ~2-14 % based on the RCP scenario and level of warming. However, a decrease in mean annual precipitation is projected over northwest parts of the Indian sub-continent and the equatorial Indian Ocean with increased levels of warming. In general, we find multifold increase in the frequency of occurrence of daily precipitation extremes over the Indian subcontinent and surrounding oceans. Over Indian land, frequency of occurrence of daily precipitation extremes show up to three-fold increase under both RCP scenarios for global warming levels in the range of 1.5 oC–2.5 oC. With further increase in warming we find that the frequency of occurrence of daily precipitation extremes could show a massive four- to six-fold increase over majority of Indian land. Notably, unlike the projected increase in the frequency of occurrence of daily precipitation extremes, the projected change in annual mean precipitation is found to be insignificant in a 1.5 oC warmer world, over majority of the south Asian region, under both RCP scenarios. Given the projected large increase in frequency of daily precipitation extremes with increased levels of warming, our study provides scientific support to the recommendations of the Paris Agreement of 2015.

Formation of a Rain Shadow: O and H Stable Isotope Records in Authigenic Clays From the Siwalik Group in Eastern Bhutan

AbstractWe measure the oxygen and hydrogen stable isotope composition of authigenic clays from Himalayan foreland sediments (Siwalik Group), and from present day small stream waters in eastern Bhutan to explore the impact of uplift of the Shillong Plateau on rain shadow formation over the Himalayan foothills. Stable isotope data from authigenic clay minerals (&lt;2 μm) suggest the presence of three paleoclimatic periods during deposition of the Siwalik Group, between ∼7 and ∼1 Ma. The mean δ18O value in paleometeoric waters, which were in equilibrium with clay minerals, is ∼2.5‰ lower than in modern meteoric and stream waters at the elevation of the foreland basin. We discuss the factors that could have changed the isotopic composition of water over time and we conclude that (a) the most likely and significant cause for the increase in meteoric water δ18O values over time is the “amount effect,” specifically, a decrease in mean annual precipitation. (b) The change in mean annual precipitation over the foreland basin and foothills of the Himalaya is the result of orographic effect caused by the Shillong Plateau's uplift. The critical elevation of the Shillong Plateau required to induce significant orographic precipitation was attained after ∼1.2 Ma. (c) By applying scale analysis, we estimate that the mean annual precipitation over the foreland basin of the eastern Bhutan Himalayas has decreased by a factor of 1.7–2.5 over the last 1–3 million years.

Hydrological Modeling of Climate Change Impacts in a Tropical River Basin: A Case Study of the Cauto River, Cuba

The soil and water assessment tool (SWAT) model was applied for the first time in Cuba to assess the potential impacts of climate change on water availability in the Cauto River basin. The model was calibrated (and validated) for the 2001–2006 (2007–2010) period at a monthly timescale in two subbasins La Fuente and Las Coloradas, representative of middle and upper sections of the Cauto basin; the calibrated models showed good performance. The output available for the regional climate Model RegCM4.3 was used to force the calibrated SWAT models to simulate a baseline (1970–2000) period and near-future (2015–2039) hydrologic regimes under the representative concentration pathway (RCP) 8.5 emission scenario. The future projections suggest regional increases of 1.5 °C in mean annual temperature and a 38% decrease in mean annual precipitation in the subbasins. These changes translate to possible reductions in the annual streamflow of up to 61% with respect to the baseline period, whereas the aquifer recharge in the basin is expected to decrease up to 58%, with a consequent reduction of groundwater flow, especially during the boreal summer wet season. These projection scenarios should be of interest to water resources managers in tropical regions.

The hydraulic transfers “Setif-Hodna” to cope with impact of climate change on Setif high plains region

PurposeThe purpose of this paper is twofold: first, to show the impact of greenhouse gas emission scenarios on annual temperature and precipitation changes during three periods of the twenty-first century in Setif region by using two selected GCMs; and second, to show the importance of “Setif-Hodna” hydraulic transfers’ project, like a method to adapt to the water scarcity in the future.Design/methodology/approachThis study investigates likely changes in annual temperature and precipitation over Setif high plains region (North-East of Algeria) under four Special Report on Emission Scenarios scenarios: A1B, B1, A2 and B2, between three time slices: 2030, 2060 and 2090. MAGICC-SCENGEN 5.3v.2 was used as a tool for downscaling the two selected general circulation models.FindingsThe projections of GFDLCM20 and GFDLCM21 indicate that annual temperature will increase under the four scenarios and across the three time slices. GFDLCM20 predictions indicate a general decrease in mean annual precipitation across the four scenarios, with average of −3.02, −2.47 and −1.07 percent in 2030, 2060 and 2090, respectively. GFDLCM21 show a high decrease, with values of −18.72, −27.2 and −31.9 percent across the three periods, respectively.Originality/valueThis work is one of the first to study the impact of greenhouse gas emission scenarios on annual temperature and precipitation changes over the region, and present the hydraulic transfers project “Setif-Hodna” like an adaptive strategy to limit the effect of water scarcity in this region.

Evolution of integrated lake status since the last deglaciation: A high-resolution sedimentary record from Lake Gonghai, Shanxi, China

Alpine lakes not only provide internationally important habitats for endangered species, they also play a crucial role in the regional water balance. Unfortunately, a rapid loss of alpine lakes in China has occurred in recent decades; however, intensive human activities, together with regional differences in the responses of lakes to climate change, has impeded our understanding of the contribution of climate change to the loss of these lakes. To better understand how alpine lakes will evolve with continuing global warming, we used the analysis of new sedimentary proxies from Lake Gonghai, an undisturbed alpine lake, together with a review of published records, to reconstruct variations in integrated lake status since the last deglaciation. From 14,660–11,890 cal. yr BP the lake was in the most unstable state, indicated by the highest amplitude fluctuations in lake level and the within-lake environment. The lake status experienced clear millennial-scale changes. During the early and middle Holocene (11,890–3200 cal. yr BP), the most stable lake status occurred, consistent with the highest precipitation levels. Owing to the highest level of freshwater influx in the middle Holocene (8–5 ka), the lake water was the deepest and most acidic. At this time, the dense vegetation cover resulted in maximum catchment stability and the lowest level of soil erosion, and hence the lowest sediment accumulation rate. From 3200 cal. yr BP, decreasing mean annual precipitation resulted in a moderately stable lake status, a shallow water depth and more alkaline lake water. The sparse vegetation cover caused a dramatic increase in the erosion rate and hence in the sediment accumulation rate. We infer that variations in local humidity were the major control on the integrated lake status during the last ~14,600 cal. yr BP. With the anticipated progression of global warming, the status of the alpine lakes in the region may continue to deteriorate and appropriate mitigation strategies are imperative.

Environmental and species-specific controls on δ13C and δ15N in dominant woody plants from central-western Argentinian drylands

Spatial variation in mean annual precipitation is the principal driver of plant water and nitrogen status in drylands. The natural abundance of carbon stable isotopes (δ13C) in photosynthetic tissues of C3 plants is an indicator of time-integrated behaviour of stomatal conductance; while that of nitrogen stable isotopes (δ15N) is an indicator of the main source of plant N (soil N vs. atmospheric N2). Previous studies in drylands have documented that plant δ13C and δ15N values increase with decreasing mean annual precipitation due to reductions in stomatal conductance, and soil enriched in 15N, respectively. However, evidence for this comes from studies focused on stable isotopes measurements integrated at the plant community level or on dominant plants at the site level, but little effort has been made to study C and N isotope variations within a species growing along rainfall gradients. We analysed plant δ13C, δ15N and C/N values of three woody species having different phenological leaf traits (deciduous, perennial and aphyllous) along a regional mean annual precipitation gradient from the central-western Argentinian drylands. Noticeably, plant δ13C and δ15N values in the three woody species did not increase towards sites with low precipitation or at the start of the growing season (drier period), as we expected. These results suggest that environmental factors other than mean annual precipitation may be affecting plant δ13C and δ15N. The short-term environmental conditions may interact with species-specific plant traits related to water and nitrogen use strategies and override the predictive influence of the mean annual precipitation on plant δ13C and δ15N widely reported in drylands.

Simulation of climate change in Iran during 2071-2100 using PRECIS regional climate modelling system

Parameters such as future precipitation, temperature, snowfall, and runoff were modeled using PRECIS regionalclimate modeling system in Iran with the horizontal resolutions of 0.44×0.44°C in latitude and longitude under SRESA2 and B2 scenarios. The dataset was based on HadAM3p during the periods of 1961-1990 and 2071-2100. Theoverall precipitation error of the model in the period of 1961-1990 was 5.3%. Minimum errors were found to be overAzari, north-central, and Kordi regions. Maximum and minimum monthly precipitation errors were found inSeptember and May, respectively; but, minimum and maximum seasonal biases were found in spring and winter with-0.1 and -17.2% errors, respectively. Results revealed a decrease in mean annual precipitation toward the end of the21st century by 7.8 mm in B2 scenario and 10.1 mm in A2 Scenario with maximum regional decrease of 100 mm inthe southeast of the Caspian Sea. The decrease in precipitation was higher for A2 scenario, whereas it was minimumfor B1 scenario. Mean annual temperature of Iran during 2071-2100 would be projected to increase by 4.5-5.5°C inA2 scenario and 3-4°C in B2 scenarios compared to 1961-1990. It was shown that mean annual changes in runoffover the country were negligible both in A2 and B2 scenarios. Maximum annual amount of runoff increase was foundover western part of the Caspian Sea, Zagros and Alborz mountain chains by 6.4-15. 8mm. Results also indicated thatannual snowfall would decrease by the maximum amount of 22.9-23.7 cm over Zagros and Alborz mountain chains.

Lupinus elegans KUNTH ASSISTED MIGRATION IN COMMON GARDEN FIELD TESTS

Lupinus elegans is a species used in ecological restoration and agroforestry programs, because it is tolerant to stress and fixes nitrogen. Genetic variation in quantitative traits was studied in six populations of L. elegans collected along an altitudinal gradient (2312 to 2885 m) in the Mil Cumbres region, east-central Michoacán state, México. Provenance tests were planted at 2600 and 2800 m altitude in two common garden field trials. Tests aimed to evaluate the performance at a different altitude than the site of the seed source, simulating an altitudinal-assisted migration. Survival, plant height growth and aerial biomass were measured. For each provenance and experimental sites, climatic variables were estimated for contemporary climate (average 1961-1990) and future climate (decade centered in 2030, by averaging six model scenarios). It was estimated that by the year 2030 there will be, on average, an increment of 1.4 °C in mean annual temperature, an increase of 518 degree-days &gt; 5 °C (DD5), a 90 mm decrease in mean annual precipitation (MAP) (-7.3 % of contemporary MAP), and a 0.0077 increase in an aridity index (DD50.5/MAP). An ANOVA for each site revealed that in the higher altitude site (2800 m) populations exhibited a pronounced pattern of genetic differentiation (P = 0.0001), in which plant height and biomass are associated with the transfer distance between their place of origin and the experimental site. This distance can be expressed in difference in altitude, mean annual temperature, or aridity index. At the site at higher altitude, plants originated from populations growing at higher altitudes were taller and had more biomass than those originated grown at lower altitudes (R2 ≥ 0.85, P ≤ 0.0302). In contrast, in the lower altitude site (2600 m), although there were nearly significant differences (P ≤ 0.0615) between populations for all of the variables, there was no clinal pattern. In general, the populations grew less when they were moved away from their original climate: those from the higher altitudes grew less in the 2600 m site, and those from the lower altitudes grew less in the 2800 m site. This indicates that climate change will likely induce less growth in several populations, thus it is recommended to promote gradual assisted migration.

Vegetation Activity in the Upper Oueme Basin (Benin, Africa) Studied from SPOT-VGT (2002-2012) According to Land Cover

Signs of climate change in West Africa over the last few decades are among the significant observed in the tropics, in particular the decrease in mean annual precipitation. Although such change has brought about new eco-climatic constraints on vegetation forms, it has not proven easy to determine interannual and intra-seasonal variations on a regional scale for major vegetation forms, whether natural or highly artificial as a result of human activities. The present study analyzes vegetation activity via a Normalized Difference Vegetation Index (NDVI) defined from ten-day SPOT-VGT data (one-km resolution, covering the period from 2002 to 2012) in the African Monsoon Multidisciplinary Analysis (AMMA) Program observation zone, located in the Upper Oueme River Basin in Benin. The statistical analysis is mainly based on a multifactor approach allowing approximately 54% of interannual NDVI variations to be accounted for. Results show that spatio-temporal NDVI variability in the River Basin is highly dependent on land use, be it forest, wooded savanna, farmland or areas undergoing conversion.

How much climate change can pastoral livelihoods tolerate? Modelling rangeland use and evaluating risk

Livestock is the most important source of income for pastoral livelihoods in drylands. Pastoralists have developed flexible resource utilization strategies that enable them to cope with the high spatio-temporal resource variability typical to these areas. However, climate change in the form of decreasing mean annual precipitation accompanied by increasing variability has important consequences for rangeland productivity and thus pastoral livelihood security. Here, we use a spatial simulation model to assess impacts of changing precipitation regimes, and to identify limits of tolerance for these changes beyond which pastoral livelihoods cannot be secured. We also examine strategies to control these limits.Our results indicate that: (i) while reduced mean annual precipitation always had negative effects, increased precipitation variability can have negative, none or even positive effects, depending on the vegetation's recovery potential. (ii) Depending on income requirements there are limits of tolerance to decreases in mean annual precipitation beyond which precipitation regimes overcharge the coping capacity of the pastoral household and threaten its livelihood. (iii) There are certain strategies, in particular “Increasing mobility” and “Diversifying income for coping with income risks from pastoralism”, that allow the limits of tolerance to be shifted to a certain extent. We conclude that it is important to consider climate change and human requirements together to create appropriate climate change mitigation strategies in pastoral systems. Our results also shed new light on the discussion on disequilibrium rangeland systems by identifying mechanisms that can support fluctuating but non-degrading herbivore-vegetation dynamics. The paper finishes with remarks on the broader potential of the presented modelling approach beyond rangelands.

The effects of precipitation regime on soil carbon pools on the Yucatan Peninsula

Abstract:The effects of precipitation regime on the size of soil carbon (C) pools were compared in mature tropical dry forests of the Yucatan Peninsula. Our study included three forest stands in each, a dry site (potential evapotranspiration ratio = 3.2 mm mm−1; mean annual precipitation = 537 mm), a wetter site (2.0 mm mm−1; 993 mm) and a site in which water was comparatively less limiting (1.3 mm mm−1; 1086 mm). At each site, soil C pools in dead fallen phytomass (includes leaves, flowers, fruits, small twigs and deadwood debris) deposited on the litter layer and in roots and organic matter of the mineral soil (from the upper 10 cm) were measured in samples collected during the dry season. A high proportion of the total C pool (93–95%) was in the top 10 cm of soil in all forest sites. The smallest C pool was in roots (1.8–2.4% of the total C), meanwhile the C in the litter layer represented 3–5% of the total pool. These patterns were observed irrespective of study site. However, distribution of C (i.e. wood debris vs. fine litter) varied across sites; the proportion of the forest-floor C pool in wood debris decreased from 80% in the driest site, to 51% and 42% in 993-mm and 1086-mm sites, respectively. Overall, we observed that three pools (wood debris, roots and soil organic C) provide evidence for the significant decrease in soil C storage with increase in mean annual precipitation in Yucatan Peninsula. A potential explanation for this unexpected pattern includes an increasing C turnover time with decreasing mean annual precipitation, resulting in higher C accumulation per unit of C input in the driest site.

Shifts in plant species elevational range limits and abundances observed over nearly five decades in a western North America mountain range

AbstractQuestionHave there been shifts in abundance and distribution of alpine and sub‐alpine plant species along an elevational gradient in an arid North American mountain range during the last half‐century?LocationElevational gradient in the White Mountains, California, USA (37°30′ N, 118°10′ W).MethodsWe conducted a 49‐yr re‐survey of plant species distribution and abundance in areas originally surveyed in 1961. Species abundance data were collected along line transects between elevations of 2900 and 4000 m. We evaluated the degree of plant community shift over time across elevations; specifically, we expected species ranges to shift upward such that species peak abundances would be observed higher in elevation in 2010 than in 1961. To address this expectation we conducted a permutational multivariate linear model analysis with elevation, soil type and year as factors. We further performed single‐species analyses to evaluate how focal species contributed to the multivariate community‐level shifts between 2010 and 1961, and how these varied across elevations and soil types. Growing season climate data (June 1 through October 31) collected between 1961 and 2010 were analysed to quantify the change in annual mean temperature and precipitation at this site.ResultsWe found that Artemisia rothrockii increased in abundance at the upper reaches of its distribution between the 2010 and 1961 surveys. Additionally, we recorded significant declines in abundances in the lower elevation ranges of three alpine cushion plants: Trifolium andersonii, Phlox condensata and Eriogonum ovalifolium. These shifts coincided with a 0.98 °C increase in mean growing season temperatures and a 53 mm decrease in mean annual precipitation between 1961 and 2010.ConclusionsThese results suggest that rising temperatures and decreasing precipitation are negatively impacting alpine plant species while promoting expansion of sub‐alpine species, possibly signalling the transition of this alpine plant community to sagebrush steppe.