Precipitation and Reproduction are Negatively Associated with Female Turkey Survival

Understanding how reproductive tradeoffs act in concert with abiotic elements to affect survival is important for effective management and conservation of wildlife populations, particularly for at-risk or harvested species. Wild turkeys (Meleagris gallopavo) are a high-interest species for consumptive and non-consumptive uses, and female survival is a primary factor influencing turkey population dynamics. We radio-tracked and collected survival data on 140 female Merriam's wild turkeys (M. g. merriami) in the northern Black Hills, South Dakota, USA, 2016–2018. We developed and compared a set of candidate models to evaluate how nest incubation, brood rearing, and precipitation could be associated with female survival. Increased time spent incubating was associated with reduced female survival. Additionally, daily precipitation was associated with reduced survival of incubating females. Seasonal survival was lowest during spring and winter. A female that did not incubate a nest was predicted to have a higher rate of annual survival (0.53, 85% CI = 0.48–0.59) than a female that incubated a single nest (0.47, 85% CI = 0.42–0.53). Despite the relative proximity of population segments, we estimated that annual survival for nesting and non-nesting females was lower in the northern Black Hills compared to annual female survival in the southern Black Hills, underscoring the need for region-specific data when possible. © 2020 The Wildlife Society.     

降水变化对红砂-珍珠碳、氮、磷化学计量特征的影响

以荒漠C3植物红砂(Reaumuria soongarica)和C4植物珍珠(Salsola passerina)为材料,在西北干旱荒漠区沿自然降水梯度,对不同降水条件下单生和混生红砂与珍珠根、茎、叶器官碳、氮、磷化学计量指标进行测定,分析其在不同生境下化学计量特征对种间关系及环境胁迫的响应规律。结果表明:(1)随干旱胁迫程度增加(降水量的减少),红砂各器官C含量平均升高7.73%,N、P含量分别平均降低6.20%、10.61%;珍珠各器官C含量平均升高7.36%,N、P含量分别平均降低5.93%、14.03%。两种植物叶片C含量升高表明其光合速率较低,生长缓慢,但对外界不利环境的防御能力增强,能更好地适应干旱环境。(2)干旱胁迫改变了红砂和珍珠的N、P含量在各器官的分配模式,两种植物N、P含量在叶部高于根部,在根、叶中N/P明显高于茎,表明两种植物不同器官受到的养分限制不同。(3)红砂各器官C、N、P含量高于珍珠,说明红砂防御能力较强,生长速率高,对资源的竞争和利用能力较珍珠强;珍珠C/N和C/P均高于红砂,表明珍珠比红砂有较强的碳同化能力和较高的营养利用效率。(4)在干旱胁迫条件下,红砂和珍珠均表现为碳素积累、氮磷素限制的格局,它们对于氮和磷的养分利用不活跃,受到氮和磷养分的限制较为均衡。     

陕甘宁地区降水同位素云下二次蒸发效应

大气降水过程中,雨滴由云层底部降落至地面经过不饱和空气时发生的蒸发现象,即为云下二次蒸发,这会使得降水同位素组成发生改变。利用氢氧稳定同位素方法研究云下二次蒸发效应的时空变化及其成因,对探讨区域水循环过程具有重要意义。本研究基于陕甘宁地区2018年3月—2019年2月187个气象站逐小时气象数据,采用改进后的Stewart模型,分析了该区域蒸发剩余比(f)与降水过量氘变化量(Δd)的时空变化,并探讨了f以及气象要素与Δd的关系。结果表明: 从小时尺度来看,该区域各省f与Δd最小值均出现在白天,最大值出现在夜晚,即白天云下二次蒸发效应更明显。从月尺度来看,各省f、Δd月变化趋势较为一致,最小值多出现在夏半年,最大值多出现在冬半年,即夏半年云下二次蒸发效应更显著。研究区f、Δd值在季节尺度上的空间变化一致:春季,东、西部地区较大,中部较小;夏季,西北部地区偏小,其他地区偏大;秋季,由南向北减小;冬季,中部、南部较小,西部及东北部较大,研究区不同季节云下二次蒸发效应的空间差异显著。陕甘宁三省(区)f与Δd的线性关系的斜率均小于1‰·%^-1,这可能与该地区干旱半干旱气候具有较大关系。当气温较高,相对湿度、水汽压、降水量和雨滴直径较小时,Δd值较小,云下二次蒸发效应较明显。     

西南高山亚高山区植被水分利用效率时空特征及其与气候因子的关系

水分利用效率(WUE)是深入理解生态系统水碳循环及其耦合关系的重要指标。为了揭示气候变化背景下区域尺度不同植被类型的响应和适应特征, 对中国西南高山亚高山地区2000-2014年的9种植被类型的WUE时空特征及其影响因素进行探究。该研究基于MODIS总初级生产力(GPP)、蒸散发(ET)数据和气象数据, 估算西南高山亚高山区植被WUE, 采用趋势分析及相关分析等方法, 分析了研究区植被WUE与气温、降水及海拔的关系。主要结果: (1)西南高山亚高山区2000-2014年植被WUE多年均值为0.95 g·m^-2·mm^-1, 整体呈显著增加趋势, 增速为0.011 g·m^-2·mm^-1·a^-1; 空间上WUE呈东南高西北低的分布, 85.84%区域的WUE呈增加趋势。(2)西南高山亚高山区各植被类型WUE多年均值表现为常绿针叶林>稀树草原>常绿阔叶林>有林草原>农田>落叶阔叶林>混交林>郁闭灌丛>草地; 时间上, 各植被类型WUE均呈上升趋势。(3)西南高山亚高山区89.56%区域的WUE与气温正相关, 92.54%区域的WUE与降水量负相关; 各植被类型中, 草地WUE与气温的相关性最高, 有林草原WUE与降水量的相关性最高。(4)西南高山亚高山区典型的地带性顶极植被常绿针叶林的WUE具有较强的海拔适应性及应对气候变化的能力。     

Spatial-temporal character of vegetation cover and its influence factors in the Shule River Basin China,during 1985–2011

Abstract

Vegetation coverage is an important indicator of the terrestrial ecosystems, and it provides crucial significance for evaluation and analysis of vegetation change. The Shule River Basin is a typical ecological fragile region in the inland of Northwest China. We used vegetation coverage index as given in Technical Specifications for Assessment of Ecological Environment. Geographic information system (GIS) spatial analysis was used to analyze the temporal and spatial features of vegetation cover in the Shule River Basin and its influencing factors from 1986 to 2011. The results showed that vegetable cover is very low in most areas of Shule River Basin with only the upstream parts of the oasis and watershed haven high vegetation cover. The average vegetation coverage index increased from 6.78 to 8.31 during 1986–2011. An area of 59,998?km² in the Shule River Basin has unchanged vegetation coverage index and this account for 51.7% of watershed areas for the period of the study. Also, an area of 31,721?km² recorded an increased vegetable cover, accounting for 27.3% while an area of 24,372?km² decreased vegetation cover which accounts for 21.0%. There was different correlation between vegetation cover and annual precipitation in the Shule River Basin.     

Precipitation‐drainage cycles lead to hot moments in soil carbon dioxide dynamics in a Neotropical wet forest

Soil CO₂ concentrations and emissions from tropical forests are modulated seasonally by precipitation. However, subseasonal responses to meteorological events (e.g., storms, drought) are less well known. Here, we present the effects of meteorological variability on short‐term (hours to months) dynamics of soil CO₂ concentrations and emissions in a Neotropical wet forest. We continuously monitored soil temperature, moisture, and CO₂ for a three‐year period (2015–2017), encompassing normal conditions, floods, a dry El Niño period, and a hurricane. We used a coupled model (Hydrus‐1D) for soil water propagation, heat transfer, and diffusive gas transport to explain observed soil moisture, soil temperature, and soil CO₂ concentration responses to meteorology, and we estimated soil CO₂ efflux with a gradient‐flux model. Then, we predicted changes in soil CO₂ concentrations and emissions under different warming climate change scenarios. Observed short‐term (hourly to daily) soil CO₂ concentration responded more to precipitation than to other meteorological variables (including lower pressure during the hurricane). Observed soil CO₂ failed to exhibit diel patterns (associated with diel temperature fluctuations in drier climates), except during the drier El Niño period. Climate change scenarios showed enhanced soil CO₂ due to warmer conditions, while precipitation played a critical role in moderating the balance between concentrations and emissions. The scenario with increased precipitation (based on a regional model projection) led to increases of +11% in soil CO₂ concentrations and +4% in soil CO₂ emissions. The scenario with decreased precipitation (based on global circulation model projections) resulted in increases of +4% in soil CO₂ concentrations and +18% in soil CO₂ emissions, and presented more prominent hot moments in soil CO₂ outgassing. These findings suggest that soil CO₂ will increase under warmer climate in tropical wet forests, and precipitation patterns will define the intensity of CO₂ outgassing hot moments.     

Annual ecosystem respiration is resistant to changes in freeze–thaw periods in semi‐arid permafrost

Warming in cold regions alters freezing and thawing (F–T) of soil in winter, exposing soil organic carbon to decomposition. Carbon‐rich permafrost is expected to release more CO₂ to the atmosphere through ecosystem respiration (Re) under future climate scenarios. However, the mechanisms of the responses of freeze – thaw periods to climate change and their coupling with Re in situ are poorly understood. Here, using 2 years of continuous data, we test how changes in F–T events relate to annual Re under four warming levels and precipitation addition in a semi‐arid grassland with discontinuous alpine permafrost. Warming shortened the entire F–T period because the frozen period shortened more than the extended freezing period. It decreased total Re during the F–T period mainly due to decrease in mean Re rate. However, warming did not alter annual Re because of reduced soil water content and the small contribution of total Re during the F–T period to annual Re. Although there were no effects of precipitation addition alone or interactions with warming on F–T events, precipitation addition increased total Re during the F–T period and the whole year. This decoupling between changes in soil freeze – thaw events and annual Re could result from their different driving factors. Our results suggest that annual Re could be mainly determined by soil water content rather than by change in freeze – thaw periods induced by warming in semi‐arid alpine permafrost.     

Precipitation controls seed bank size and its role in alpine meadow community regeneration with increasing altitude

The Tibetan Plateau has undergone significant climate warming in recent decades, and precipitation has also become increasingly variable. Much research has explored the effects of climate change on vegetation on this plateau. As potential vegetation buried in the soil, the soil seed bank is an important resource for ecosystem restoration and resilience. However, almost no studies have explored the effects of climate change on seed banks and the mechanisms of these effects. We used an altitudinal gradient to represent a decrease in temperature and collected soil seed bank samples from 27 alpine meadows (3,158–4,002 m) along this gradient. A structural equation model was used to explore the direct effects of mean annual precipitation (MAP) and mean annual temperature (MAT) on the soil seed bank and their indirect effects through aboveground vegetation and soil environmental factors. The species richness and abundance of the aboveground vegetation varied little along the altitudinal gradient, while the species richness and density of the seed bank decreased. The similarity between the seed bank and aboveground vegetation decreased with altitude; specifically, it decreased with MAP but was not related to MAT. The increase in MAP with increasing altitude directly decreased the species richness and density of the seed bank, while the increase in MAP and decrease in MAT with increasing altitude indirectly increased and decreased the species richness of the seed bank, respectively, by directly increasing and decreasing the species richness of the plant community. The size of the soil seed bank declined with increasing altitude. Increases in precipitation directly decreased the species richness and density and indirectly decreased the species richness of the seed bank with increasing elevation. The role of the seed bank in aboveground plant community regeneration decreases with increasing altitude, and this process is controlled by precipitation but not temperature.