模拟增温和降雨增加对撂荒草地土壤胞外酶活性及计量特征的影响

土壤胞外酶活性是催化土壤有机质分解的关键限速步骤,而且对外界环境的变化极其敏感,然而却很少有研究聚焦于土壤胞外酶活性对气候变化的响应,尤其是在黄土高原地区.以黄土丘陵区撂荒草地为研究对象,野外模拟气候变暖和降水增加,通过测定土壤理化性质、植被群落特征和土壤酶活性,探究土壤酶活性及计量比对气候变化的响应特征及驱动因素.结果表明,增温、增雨以及二者的交互作用均显著降低了土壤β-1,4-葡糖苷酶(BG)和纤维二糖水解酶(CBH)活性,然而,土壤β-1,4-木糖苷酶(BX)活性在气候变化处理下却呈现出增加趋势,其中,增温处理的增幅最大,达到了63.15%.增温增雨的交互显著增加了β-1,4-N-乙酰氨基葡萄糖苷酶(NAG)和亮氨酸胺肽酶(LAP)以及碱性磷酸酶(ALP)活性,分别增加了34.32%、 12.97%和44.86%.增温显著增加了过氧化物酶(PER)活性,而增雨显著降低了PER酶活性,增雨以及增温增雨显著降低了多酚氧化酶(PPO)活性,这主要归因于植物群落科组成的变化.增雨和增温增雨处理下碳降解酶活性∶氮降解酶活性(CEs∶NEs)和氮降解酶活性∶磷降解酶活性(NEs∶PEs)显著...     

A new method for broad-scale modeling and projection of plant assemblages under climatic,biotic, and environmental cofiltering

There is increasing interestin broad-scale analysis, modeling, and prediction of the distribution and composition of plant species assemblages under climatic, environmental, and biotic change, particularly for conservation purposes. We devised a method to reliably predict the impact of climate change on large assemblages of plant communities, while also considering competing biotic and environmental factors. To this purpose, we first used multilabel algorithms in order to convert the task of explaining a large assemblage of plant communities into a classification framework able to capture with high cross-validated accuracy the pattern of species distributions under a composite set of biotic and abiotic factors. We applied our model to a large set of plant communities in the Swiss Alps. Our model explained presences and absences of 175 plant species in 608 plots with >87% cross-validated accuracy, predicted decreases in α, β, and γ diversity by 2040 under both moderate and extreme climate scenarios, and identified likely advantaged and disadvantaged plant species under climate change. Multilabel variable selection revealed the overriding importance of topography, soils, and temperature extremes (rather than averages) in determining the distribution of plant species in the study area and their response to climate change. Our method addressed a number of challenging research problems, such as scaling to large numbers of species, considering species relationships and rarity, and addressing an overwhelming proportion of absences in presence–absence matrices. By handling hundreds to thousands of plants and plots simultaneously over large areas, our method can inform broad-scale conservation of plant species under climate change because it allows species that require urgent conservation action (assisted migration, seed conservation, and ex situ conservation) to be detected and prioritized. Our method also increases the practicality of assisted colonization of plant species by helping to prevent ill-advised introduction of plant species with limited future survival probability.     

2000~2020年西南地区植被NDVI对气候变化和人类活动响应特征

研究植被变化及其对气候变化和人类活动的响应机制,对区域生态保护和植被恢复具有重要现实意义.利用MODIS NDVI数据、基于站点的气象数据和土地利用数据,结合Theil-Sen Median趋势分析、Mann-Kendall显著性分析、残差分析、偏相关分析和复相关分析等方法,基于不同地貌单元,分析2000～2020年中国西南地区植被覆盖时空演变特征及其对气候和土地利用变化的响应特征.结果表明,2000～2020年西南地区植被NDVI整体呈波动上升趋势,上升斜率在空间上呈东南高和西北低的分异格局.气候变化和人类活动对西南地区植被NDVI上升均以促进作用为主,且对广西丘陵植被生长的促进作用强于其他地貌单元.2000～2020年间西南地区植被NDVI与气温和降水呈正相关,与相对湿度和日照时数呈负相关,且温度是影响西南地区植被NDVI变化的气候主导因子.城市扩张在一定程度上减少了区域植被覆盖,但得益于适宜的气候条件以及林业生态工程的实施,西南地区整体植被覆盖以上升为主.研究结果可为西南地区生态保护及经济可持续发展提供科学依据.     

同质环境下不同锦鸡儿属植物根际土壤细菌群落结构差异及其影响因素

采用高通量测序技术分析同质环境下小叶锦鸡儿、中间锦鸡儿和荒漠锦鸡儿根际土壤细菌多样性及群落结构,以期探讨驱动锦鸡儿属植物根际土壤细菌群落结构构建的关键因子.结果表明,土壤样品中共检测到细菌42门55纲123目244科558属,优势菌门为变形菌门(Proteobacteria)、蓝藻门(Cyanobacteria)、放线菌门(Actinobacteria)、拟杆菌门(Bacteroidetes)、厚壁菌门(Firmicutes)和酸杆菌门(Acidobacteria)(相对丰度>1%),优势属为苯基杆菌属(Phenylobacterium)、剑菌属(Ensifer)和鞘氨醇菌属(Chitinophaga).双因素方差分析表明,物种间差异显著影响土壤细菌香农指数和辛普森指数(P<0.05),种源和物种交互作用对土壤细菌的物种数、 Chao1指数、香农指数和辛普森指数均影响显著(P<0.05).主坐标分析表明,3种锦鸡儿属植物根际土壤细菌群落结构差异显著(P<0.05),且聚类分析显示来自不同种源地的中间锦鸡儿和荒漠锦鸡儿根际土壤细菌群落结构组成不同.通过冗余分析发现...     

Climate change and adoption of sustainable land management practices in the Niger basin of Benin

Due to the important role that the agricultural sector plays in sustaining growth and reducing poverty in developing countries, the adoption of practices that have the potential to simultaneously improve agricultural productivity while minimizing environmental impacts is essential. This paper examines the determinants of farmers’ perceptions of climate change and subsequent adoption of sustainable land management practices in the Niger basin of Benin. Binary and multivariate probit models are applied in a two‐stage regression procedure to cross‐sectional data collected through a survey of 545 randomly selected farm households in 28 villages. The findings indicate that there are substitutabilities among three pairs of sustainable land management practices being used by the farmers. Climate change perception is positively related to land tenure, experience in farming, number of relatives, tractor use, and membership in farmers’ organizations, and negatively related to household size, remoteness, and plough use. Moreover, the findings reveal that the uptake of land management practices is related to assets, land tenure, education level of the household head, remoteness, social network, non‐irrigated land size, having a farm located near a river/lake/stream, tractor and plough use, being a subsistence farmer or not, and memberships in farmers’ organizations. The adoption of sustainable land management practices could be encouraged through improving access to markets, adequate roads, and technologies, as well as by promoting membership in farmers’ organizations.     

Climate variability,water levels,and fish catch in the Upper East Region of Ghana

The aim of the research was to investigate the effects of climate variability on selected water bodies in the Upper East Region of Ghana using time series decomposition and simple linear regression analyses. Data on temperature and rainfall (1960–2015), annual total fish catch (1996–2016), and the recorded water levels (1987–2015) of a major reservoir, the Tono, were used. Time series decomposition analyses were performed on the rainfall, temperature, and water level data to identify their trends. While temperature was increasing, rainfall was decreasing and resulted in a decrease in the water level in the Tono Reservoir. The decreasing water level in the reservoir made fish catch easier, which led to overfishing. Out of the other 39 dugouts studied, 8 (21%) were silted. Also, rainfall was decreasing at 4.4% per decade and minimum and maximum temperatures were increasing at 2.5% and 0.03% per decade, respectively. The minimum, maximum, and mean water levels of the Tono Reservoir were 3.7, 8.0, and 4.9 meters (m), respectively. The water level of the Tono Reservoir was decreasing by ?0.08 m per year. It is concluded that the water level in the Tono Reservoir was continually decreasing as a result of decreasing rainfall and increasing maximum and minimum temperatures. To maintain a much more stable microclimate and decrease the siltation rate of the reservoirs, farmers are advised to stop farming along the banks of water bodies and avoid clearing vegetation. Fishermen are also encouraged to adopt fish farming in enclosed areas within the reservoir to meet the growing protein demands in the Upper East Region of Ghana.     

Meadow Restoration Increases Baseflow and Groundwater Storage in the Sierra Nevada Mountains of California

In mountains of the western United States, channel incision has drawn down the water table across thousands of square kilometers of meadow floodplain. Here climate change is resulting in earlier melt and reduced snowpack and water resource managers are responding by investing in meadow restoration to increase springtime storage and summer flows. The record‐setting California drought (2012–2015) provided an opportunity to evaluate this strategy under the warmer and drier conditions expected to impact mountain water supplies. In 2012, 0.1 km² of meadow floodplain was reconnected by filling an incised channel through Indian Valley in the central Sierra Nevada Mountains of California. Despite sustained drought conditions after restoration, summer baseflow from the meadow increased 5–12 times. Before restoration, the total summer outflow from the meadow was 5% more than the total summer inflow. After restoration, total summer outflow from the meadow was between 35% and 95% more than total summer inflow. In the worst year of the drought (2015), when inflow to the meadow ceased for at least one month, summer baseflow was at least five times greater than before restoration. Groundwater levels also rose at four out of five sites near the stream channel. Filling the incised channel and reconnecting the meadow floodplain increased water availability and streamflow, despite unprecedented drought conditions.     

Reservoir Sedimentation Rates in the Little Washita River Experimental Watershed,Oklahoma: Measurement and Controlling Factors

Forty‐five flood control reservoirs, authorized in the Watershed Protection and Flood Prevention Act 1954, were installed by United States Department of Agriculture (USDA) between 1969 and 1982 in the Little Washita River Experimental Watershed (LWREW), located in central Oklahoma. Over time, these reservoirs have lost sediment and flood storage capacity due to sedimentation, with rates dependent on upstream land use and climate variability. In this study, sedimentation rates for 12 reservoirs representing three major land use categories within LWREW were measured based on bathymetric surveys that used acoustic profiling system. Physiographic and climate attributes of drainage area of surveyed reservoirs were extracted from publicly available data sources including topographic maps, digital elevation models, USDA Natural Resource Conservation Service soils, and weather station databases. Correlation, principal component analysis, and stepwise regression were utilized to analyze the relationship between normalized reservoir sedimentation rates (ReSRa) and the drainage area characteristics to determine the major variables controlling sedimentation within the LWREW. Percent of drainage area with extreme slopes, saturated hydraulic conductivity, and maximum daily rainfall event recorded in spring explained most of the variability in ReSRa. It was also found that percent reduction in reservoir surface area can be used as a surrogate for estimating ReSRa. The implications of the results are discussed.     

From disaster management to adaptive governance? Governance challenges to achieving resilient food systems in Australia

Building resilient food systems in the context of climate change and increased natural disasters depends on governance being more ‘adaptive’. Through a case study of events surrounding the extensive flooding that occurred in Queensland, Australia, in 2011, this paper examines how governance settings and processes affected food system actors’ engagement with three aspects of adaptive governance – responsibility, participation and collaboration – as those actors sought to ensure food availability and access during the crisis. We found that, despite the existence of formal governance instruments committed to disaster management, food security and resilience at local, state and national levels, responsibilities for ensuring food supply during a disaster were not clearly articulated. Responsibility was largely assumed by supermarkets, who in turn increased the influence of retailer–government coalitions. The participation of non-supermarket food system actors in governance was low, and there was limited collaboration between local, and other, levels of governance. The policy challenge is to ensure that responsibility, participation and collaboration become a stronger foci for adaptive governance during and after a disaster such as flooding.