环境异质性对三峡库区支流香溪河附石硅藻群落的影响及驱动作用

环境异质性在一定程度上不仅可以增加物种多样性,而且影响了陆生生物群落的稳定性.然而,环境异质性如何影响水生态系统附石硅藻群落的物种多样性却较少报道.因此,以三峡库区支流香溪河的附石硅藻为研究对象,通过量化和比较香溪河在时间尺度上的环境异质性,探究其在驱动物种多样性变化的作用.结果表明,环境异质性、分类β-多样性和功能β-多样性均表现为非蓄水期显著高于蓄水期,且周转组分均对不同水文期β-多样性贡献较大,而分类α-多样性则是蓄水期显著高于非蓄水期.此外,功能α-多样性中除功能丰富度非蓄水期显著高于蓄水期外,功能均匀度和功能分散度均无显著差异.基于相似或相异度矩阵的多元回归(MRM)分析表明,NH⁺₄-N和SiO^2-₃-Si是影响非蓄水期香溪河附石硅藻群落的关键环境异质因子,而影响蓄水期香溪河附石硅藻群落的关键环境异质因子为NH⁺₄-N、 SiO^2-₃-Si和TP.这表明三峡库区不同水文期的环境异质性显著影响附石硅藻的...     

Influence of Riffle and Snag Habitat Specific Sampling on Stream Macroinvertebrate Assemblage Measures in Bioassessment

Stream macroinvertebrate communities vary naturally among types of habitats where they are sampled, which affects the results of environmental assessment. We analyzed macroinvertebrates collected from riffle and snag habitats to evaluate influences of habitat-specific sampling on taxon occurrence, assemblage measures, and biotic indices. We found considerably more macroinvertebrate taxa unique to snags (143 taxa) than to riffles (75 taxa), and the numbers of taxa found in both riffles and snags (149 taxa) were similar to that found in snags. About 64% of the 47 macroinvertebrate measures we tested differed significantly between riffles and snags. Eighty percent intercepts of regressions between biotic indices and urban or agricultural land uses differed significantly between riffles and snags. The Hilsenhoff biotic index calculated from snag samples explained 69% of the variance of riffle samples and classified 66% of the sites into the same stream health group as the riffle samples. However, four multimetric indices for snag samples explained less than 50% of the variance of riffle samples and classified less than 50% of the sites into the same health group as the riffle samples. We concluded that macroinvertebrate indices developed for riffle/run habitat should not be used for snag samples to assess stream impairment. We recommend developing an index of biotic integrity specifically for snags and using snags as an alternate sampling substrate for streams that naturally lack riffles.     

基于地理探测器的中国陆地生态系统土壤有机碳空间异质性影响因子分析

中国陆地生态系统土壤有机碳库对全球生态系统碳平衡具有显著影响.为揭示土壤碳库空间分布的潜在主控因子并为今后建立碳库空间分布模型提供依据,利用地理探测器对中国陆地生态系统表层土壤(0—20 cm)有机碳密度的影响因子(气温、降水量、DEM、NDVI、陆地生态系统类型、人口密度)进行空间分异性探测和定量归因.结果表明:自然...     

The need for constructing endangered fish habitats that conform to climate-driven flow changes in a western U.S. river

Warmwater fish habitat in the San Juan River of the southwestern United States has been reduced by over 30% as a result of water depletion, reservoir inundation, and cold-water dam releases combined with drought-related changes in hydrology. This reduction and a suite of other factors have contributed to declines in native fish populations including the federally endangered Colorado Pikeminnow (Ptychocheilus lucius) and Razorback Sucker (Xyrauchen texanus). Conservation efforts for these species include determining flow needs; protecting, managing, and augmenting habitats; and stocking hatchery fish. But the young of stocked fish have low survival due largely to a paucity of nursery habitat not being reformed and maintained under current conditions. Flow recommendations for Navajo Dam releases designed to mimic the river's natural hydrograph have not been met due to water shortages, and the desired outcomes of increased channel complexity and enhanced fish habitat have not been observed. Forecasted hydrology that includes ongoing drought shows that achieving the flow targets through further dam reoperations is unlikely. Mechanical construction of early life-stage habitats is a highly recommended complement to flow management for offsetting the effects of flow reduction and habitat loss. Habitats with features that are effective and resilient under a range of flows are important in counterbalancing the effects of climate change.     

云南拉市海流域退耕还湿对农户的增收效应

基于云南拉市海流域2005～2016年的农户面板数据,采用双重差分法(DID)并借助PSM-DID、工具变量、安慰剂测试等多种稳健性检验工具,对退耕还湿的增收效应进行实证分析.研究发现,退耕还湿对农户增收具有显著的促进作用,使家庭总收入和人均收入分别提高了39.2％和43.5％,这一结论在进行多项稳健性检验后仍然成立;...     

Comparison of Three Pebble Count Protocols (EMAP,PIBO, and SFT) in Two Mountain Gravel‐Bed Streams1

Abstract: Although the term ``pebble count'' is in widespread use, there is no standardized methodology used for the field application of this procedure. Each pebble count analysis is the product of several methodological choices, any of which are capable of influencing the final result. Because there are virtually countless variations on pebble count protocols, the question of how their results differ when applied to the same study reach is becoming increasingly important. This study compared three pebble count protocols: the reach‐averaged Environmental Monitoring and Assessment Program (EMAP) protocol named after the EMAP developed by the Environmental Protection Agency, the habitat‐unit specific U.S. Forest Service’s PACFISH/INFISH Biological Opinion (PIBO) Effectiveness Monitoring Program protocol, and a data‐intensive method developed by the authors named Sampling Frame and Template (SFT). When applied to the same study reaches, particle‐size distributions varied among the three pebble count protocols because of differences in sample locations within a stream reach and along a transect, in particle selection, and particle‐size determination. The EMAP protocol yielded considerably finer, and the PIBO protocol considerably coarser distributions than the SFT protocol in the pool‐riffle study streams, suggesting that the data cannot be used interchangeably. Approximately half of the difference was due to sampling at different areas within the study reach (i.e., wetted width, riffles, and bankfull width) and at different locations within a transect. The other half was attributed to using different methods for particle selection from the bed, particle‐size determination, and the use of wide, nonstandard size classes. Most of the differences in sampling outcomes could be eliminated by using simple field tools, by collecting a larger sample size, and by systematically sampling the entire bankfull channel and all geomorphic units within the reach.     

南京市城市生态污染现状、成因分析及治理对策

通过系统研究,定量分析了南京市1997－1999年水质污染,大气环境质量,酸雨等现状,进而系统探讨了该市城市化进程中出现的主要生态环境问题,并运用生态景观异性理论和方法,结合实际调查情况,对主要的生态污染致成原因进行了分析,最后提出了具体的南京市生态环境问题治理与实现地续发展的对策。     

广州城市绿地系统景观生态学分析

绿地是城市这个人工景观中最重要的自然要素。以往对绿地的研究主要集中于能量流动等功能方面,很少涉及空间结构,在本文中,将利用景观生态学中的原理和方法,分析广州市绿地景观的异质性,并提出一些建议。     

Effects of preference heterogeneity among landowners on spatial conservation prioritization

The participation of private landowners in conservation is crucial to efficient biodiversity conservation. This is especially the case in settings where the share of private ownership is large and the economic costs associated with land acquisition are high. We used probit regression analysis and historical participation data to examine the likelihood of participation of Danish forest owners in a voluntary conservation program. We used the results to spatially predict the likelihood of participation of all forest owners in Denmark. We merged spatial data on the presence of forest, cadastral information on participation contracts, and individual‐level socioeconomic information about the forest owners and their households. We included predicted participation in a probability model for species survival. Uninformed and informed (included land owner characteristics) models were then incorporated into a spatial prioritization for conservation of unmanaged forests. The choice models are based on sociodemographic data on the entire population of Danish forest owners and historical data on their participation in conservation schemes. Inclusion in the model of information on private landowners’ willingness to supply land for conservation yielded at intermediate budget levels up to 30% more expected species coverage than the uninformed prioritization scheme. Our landowner‐choice model provides an example of moving toward more implementable conservation planning.     

Connecting science,policy, and implementation for landscape‐scale habitat connectivity

We examined the links between the science and policy of habitat corridors to better understand how corridors can be implemented effectively. As a case study, we focused on a suite of landscape‐scale connectivity plans in tropical and subtropical Asia (Malaysia, Singapore, and Bhutan). The process of corridor designation may be more efficient if the scientific determination of optimal corridor locations and arrangement is synchronized in time with political buy‐in and establishment of policies to create corridors. Land tenure and the intactness of existing habitat in the region are also important to consider because optimal connectivity strategies may be very different if there are few, versus many, political jurisdictions (including commercial and traditional land tenures) and intact versus degraded habitat between patches. Novel financing mechanisms for corridors include bed taxes, payments for ecosystem services, and strategic forest certifications. Gaps in knowledge of effective corridor design include an understanding of how corridors, particularly those managed by local communities, can be protected from degradation and unsustainable hunting. There is a critical need for quantitative, data‐driven models that can be used to prioritize potential corridors or multicorridor networks based on their relative contributions to long‐term metacommunity persistence.