Influence of agricultural landscape structure on a Southern High Plains,USA, amphibian assemblage

Landscape structure can influence demographics of spatially structured populations, particularly less vagile organisms such as amphibians. We examined the influence of agricultural landscape structure on community composition and relative abundance of the 4 most common amphibians in the Southern High Plains of central USA. Amphibian populations were monitored using pitfall traps and drift fence at 16 playa wetlands (8 playas/year) in 1999 and 2000. We quantified landscape structure surrounding each playa via estimating 13 spatial metrics that indexed playa isolation and inter-playa landscape complexity. Multivariate ordination and univariate correlations and regressions indicated that landscape structure was associated with community composition and relative abundance for 2 of the 4 amphibians. Spadefoots (Spea multiplicata, S. bombifrons) generally were positively associated with decreasing inter-playa distance and increasing inter-playa landscape complexity. Great Plains toads (Bufo cognatus) and barred tiger salamanders (Ambystoma tigrinum mavortium) usually were negatively associated with spadefoots but not influenced by landscape structure. Composition and relative abundance patterns were related to amphibian body size, which can influence species vagility and perception to landscape permeability. Spatial separation of these species in the multivariate ordination also may have been a consequence of differential competitive ability among species. These results suggest agricultural landscape structure may influence abundance and composition of spatially structured amphibian populations. This also is the first applied documentation that inter-patch landscape complexity can affect intra-patch community composition of amphibians as predicted by metapopulation theory. In the Southern High Plains, landscape complexity is positively associated with agricultural cultivation. Agricultural cultivation increases sedimentation, decreases hydroperiod, alters amphibian community dynamics, and negatively impacts postmetamorphic body size of amphibians in playa wetlands. Thus, conservation efforts should focus on preserving or restoring native landscape structure, hydroperiod, and connectivity among playas to maintain native amphibian populations and historic inter-playa movement.     

敦煌阳关国家级自然保护区湿地现状及保护对策

阐述了甘肃敦煌阳关国家级自然保护区湿地资源的类型和特点,分析了保护区湿地保护和利用存在的问题,提出了加大宣传教育,提高环保意识;制定科学合理的湿地保护、恢复和开发规划;提高科研监测水平;实施湿地恢复工程;加强环境监测等保护对策。     

The distribution of three uncommon freshwater gastropods in the drainage ditches of British grazing marshes

Marshland drainage channels (=ditches) in the UK are relicts of a once extensive habitat whose management requires quantitative information on the ecology of marshland organisms. Three freshwater gastropods in the UK Red Data Book (RDB), Segmentina nitida, Anisus vorticulus and Valvata macrostoma, are particularly poorly known, and we examined their macro-distribution across 106 ditches on four grazing marshes in SE England. Distribution reflected natural water quality, vegetation and anthropogenic factors. S. nitida occupied shallow calcareous ditches with dense emergent vegetation while A. vorticulus occupied less calcareous ditches with high plant diversity. Ditches with V. macrostoma were dominated by floating plants and slightly elevated chloride. S. nitida and V. macrostoma were absent from otherwise suitable ditches that had elevated nitrate and nitrite indicating effects from eutrophication. Conservation of these three gastropods at the regional scale requires reductions in catchment fertiliser use and also the protection of enough sites to provide the required range of natural factors (e.g., Cl and Ca). At the marsh scale, we suggest that quasi-traditional and rotational ditch clearance can provide the vegetation dynamics and diverse ditch network to ensure suitable habitat for all three species. Better information is required about dispersal, about the effectiveness of reintroduction, and about the most sensitive methods of ditch management.     

向海沼泽湿地土壤碱解氮含量的季节变化特征研究

对比分析向海沼泽封闭性湿地和开放性湿地土壤中碱解氮含量的季节变化特征结果表明,2个典型区湿地表层土壤中碱解氮含量呈不规则“N”形变化曲线,其他土壤层次变化则相对和缓,但植物枯死期各层均表现出碱解氮含量增加趋势;各层土壤碱解氮季节动态变化过程均可采用三次多项式拟合模拟,且模拟效果均较好。     

The value of bat-boxes in the conservation of Pipistrellus pygmaeus in wetland rice paddies

Wetlands with rice paddies are key habitats in the conservation of biodiversity in the Mediterranean Region and are potentially suitable habitats for foraging bats, since they provide food (insects) and drinking places; nevertheless, many wetlands lack natural roosting sites. A bat-box program designed to ascertain bat-box preferences was initiated in 1999 in the Ebro Delta (NE Spain), one of the most important wetlands in Europe. A total of 69 bat-boxes of two types (single and double compartment) were placed on three supports (trees, houses, and posts) facing east or west. Pipistrellus pygmaeus occupancy rates and the number of individuals per box were monitored on 16 occasions from July 2000 to February 2004. Bat-box preferences were only detected during the breeding season. Bat abundance was higher in east-facing boxes, in double-compartment boxes, and in boxes placed on posts and houses. Boxes on natural supports (trees) were avoided. Bat-box occupancy rates were higher during the breeding season (95.6%, spring-summer) due to the formation of maternity colonies. The number of individuals in bat-boxes during the breeding season increased as the study period progressed (from summer 2000 to summer 2003), suggesting a high degree of acceptance by maternity colonies of these alternative locations. Occupancy rates observed were the highest ever reported in bat-box scientific literature. This study highlights the role of bat-box programs as useful alternative management tools for the conservation of bat populations in highly productive wetland habitats where few natural roost sites are available.     

Cost-effectiveness of groundwater conservation measures: A multi-level analysis with policy implications

Groundwater in Spain, as in other arid and semiarid countries worldwide, has been widely used in the expansion of irrigated agriculture. In the Spanish Mancha Occidental aquifer, the excessive, and sometimes illegal, water abstraction for irrigation has promoted outstanding socioeconomic development in the area, but it has also resulted in exploitation of the aquifer and degradation of valuable wetlands. Water policies implemented in the region have not yet managed to restore the aquifer and face strong social opposition. This paper uses a multi-scale modeling approach to explore the environmental and socio-economic impacts of alternative water conservation measures at the farm and basin levels. It also analyzes their comparative cost-effectiveness to help policy makers identify the least costly policy option for achieving the goal of the Mancha Occidental aquifer's sustainability. To conduct this analysis, a Mathematical Programming Model has been developed to simulate: the closing-up and taxed-legalization of unlicensed wells, uniform volumetric and block-rate water prices, water quotas, and water markets. Aggregate results show that net social costs are not substantially different across policy option, so none of the considered policy options will be clearly more cost-effective than the others. However, there are significant differences between private and public costs (at the farm and sub-basin levels), which will be critical for determining the application in practice of these policies. Results show that controlling illegal water mining (through the legalization of unlicensed wells) is necessary, but is not sufficient to recover the aquifer. Rather, effective water management in this area will require the implementation of other water management policies as well. Among them, uniform volumetric and block-rate water pricing policies will entail the lowest net social cost, but will produce important income losses in the smallest and most water-intensive farms, which might put at risk the viability of these farms and the social acceptance of the policies. Further investigations on social costs, policy enforcement capacity and public participation in water management are highly recommended.     

西藏尼洋河—雅江流域林芝段河谷湿地土壤理化性质研究

通过对尼洋河—雅江流域林芝段河谷湿地土壤理化性质的研究,分析湿地植被覆盖率、全氮、全磷、全钾、有机质以及水溶性盐总量的空间分布特征及其相互关系。     

陕西黄河湿地苍鹭的觅食地特征

2010年6～8月,利用样方和因子分析等方法对陕西黄河湿地30处苍鹭觅食生境和300个对照样方进行了研究,以及调查了植被密度、植被高度等10个参数。独立样本T检验和Mann-Whitney U-test检验表明植被密度、干扰度、苇丛高度、土壤干湿程度等4个因子在苍鹭觅食生境与对照样方间的差异达极显著水平（P〈0.01）,植被盖度、苇丛密度2个因子也达到显著水平（P〈0.05）,植被高度、水深和至明水面距离则无显著差异。主要成分分析表明植被因子、干扰因子、水因子在苍鹭觅食地选择中均占有重要作用。     

陕西黄河湿地夏季鸟类群落结构与多样性分析

为陕西黄河湿地的生物多样性保护及管理工作提供参考资料,对陕西黄河湿地夏季鸟类群落结构与多样性进行了分析。结果表明:陕西黄河湿地共有鸟类61种,隶属于15目33科。湿地鸟类群落的多样性指数最高,总干渠次之,农田-居民区生境第三,黄土崖最低。在各群落类型中,湿地和总干渠鸟类群落间的相似性程度最高。     

小兴安岭沼泽甲烷通量日变化分析

利用静态暗箱-气相色谱法,研究了小兴安岭7种沼泽类型生长季初期、中期、末期甲烷(CH_4)通量的日变化规律,结果表明:小兴安岭沼泽甲烷通量无统一的日变化规律,且与温度和水位两个环境因子的相关性较弱.7个沼泽类型中,仅毛赤杨(Alnus sibirica)沼泽和白桦(Betula platyphylla)沼泽甲烷通量峰值在生长季初期、中期、末期出现的时间大致相同,且都为单峰曲线;苔草(Carex schmidtii)沼泽、灌丛沼泽和落叶松(Larix gmelinii)-泥炭藓(Sphagnum spp.)沼泽甲烷通量的峰值在不同时期出现的时间不同,多数为单峰曲线;落叶松-苔草沼泽和落叶松-藓类沼泽甲烷通量速率较小,多数时间吸收甲烷,没有明显的日变化规律.不同类型沼泽和生长期之间甲烷通量没有统一的日变化规律,说明在进行区域甲烷排放总量的估测时,增加每天的观测频率,或者长期、大量的观测数据可能会对提高估测精度有很大帮助.