Spatial Distribution Modelling of Kobresia pygmaea (Cyperaceae) on the Qinghai-Tibetan Plateau

Kobresia pygmaea Willd. dominates the alpine meadow ecosystem on the Qinghai-Tibet Plateau. Knowledge of this species’ distribution and ecological environment could provide valuable insights into the alpine ecosystem and key species living there, support species and ecosystem conservation in alpine regions, and build on species origin and evolutionary research. To avoid modelling uncertainty encountered in a single approach, four species distribution model algorithms (Surface Range Envelope (SRE), Generalized Linear Model (GLM), Generalized Boosted Regression (GBM) and Maximum Entropy (MAXENT)), were used to simulate the distribution of K. pygmaea based on occurrence samples that were verified using DNA sequencing techniques. Species distribution modelling revealed a vast distribution region of K. pygmaea in the northern Tibetan Highlands and alpine meadows in the southern and eastern declivity of the plateau. A high evaluation performance was found for the GLM, GBM and MAXENT models. Different potential range size patterns for the four models were found between 374340-482605 km² (average = 421591 km²). Precipitation during growing seasons was found to be the dominant factor accounting for the distribution, consistent with patterns of heat and water patterns conditions of alpine ecosystems on the plateau. Species distribution models provide a simple and reliable approach to simulating the spatial patterns of species inhabiting the Qinghai-Tibet Plateau.     

应用物种敏感性分布评估有机磷农药对淡水生物的急性生态风险

构建了4种常用有机磷农药(二嗪磷、对硫磷、杀螟硫磷和马拉硫磷)对淡水生物的物种敏感性分布(SSD)曲线,计算了4种有机磷农药对不同淡水生物的5%危害浓度(HC5)及其不同暴露浓度对淡水生物的潜在影响比例(PAF),分析了4种有机磷农药的急性生态风险,比较了脊椎动物和无脊椎动物(包括鱼类、甲壳类以及昆虫与蜘蛛类)对4种有机磷农药的敏感性,评估了3个典型水体中常用有机磷农药的联合生态风险.结果表明:1)通过HC5和PAF值的比较发现,4种有机磷农药对无脊椎动物的毒性与生态风险明显高于脊椎动物,对甲壳类的毒性与生态风险最大,对鱼类的毒性与生态风险最小.2)通过SSD曲线的对比发现,当对数暴露浓度小于3.5μg/L时,4种有机磷农药对无脊椎动物的生态风险明显高于脊椎动物;而当对数暴露浓度大于4.5μg/L时,其对脊椎动物的生态风险较大.3)在绝大多数暴露浓度下,无脊椎动物比脊椎动物对4种有机磷农药更敏感;在较低暴露浓度下,甲壳类对4种有机磷农药的敏感性较高;而在较高暴露浓度下,昆虫和蜘蛛类对其敏感性较高.4)长江、九龙江和五小川流域水体中对硫磷与马拉硫磷对淡水生物的PAF以及它们的复合潜在影响比例(msPAF)均小于0.5%,生态风险很低.     

Dynamic Changes of Stipa bungeana Steppe Species Diversity as Better Indicators for Soil Quality and Sustainable Utilization Mode in Yunwu Mountain Nature Reserve,Ningxia, China

Due to serious degradation of typical Stipa bungeana steppe community on the Loess Plateau, a 26‐year (1982–2007) experiment has been carried out by methods of forbidden grazing, cutting, and rotational grazing. Our results show that the process of succession of long‐term enclosed S. bungeana community can be divided into two stages: 1980–1996, the forward succession stage, when the species diversity and biomass reach the peak (33.7 species/m² and 1349.41 g/m², respectively); 1997–2007, the slow succession stage, when the gradually thickening of litter layer (litter depth reaches 3–5 cm) directly causes the reduction of species diversity and biomass to 19.1 species/m² and 863.19 g/m², respectively. While under the cutting and rotational grazing methods, grassland succession can be divided into four stages: 1st–5th year, the continuing growth stage; 6th–9th year, the vigorous competing stage; 10th–15th year, the aggregation growth stage of constructive species with biomass reaching the peak (1444.19 g/m²); and 16th–23rd year, stable growth stage of constructive species, which form sub‐climax and are eventually dominated by S. bungeana, with the species diversity and biomass of 25–27 species/m² and 956.76–1165.35 g/m², respectively. The constructive species suddenly change in the 24th year, and the population of S. grandis increases rapidly to 21 m^?2 accounting for 25% of the total plant population. Long‐term enclosure leads to decreased species diversity and biomass and is not beneficial for grassland renewing. The species diversity and biomass of degraded grassland continuously decrease to 10 species/m² and 392.1 g/m² due to long‐term artificial failure and transitionally grazing, leading to harden soil with slow rainfall infiltration, where plants can only sustain life under the drought condition. Therefore, reasonable cutting and rotational grazing are the methods of choice for the gradual increase of species diversity and promotion of the natural renewal and forward succession of the grassland on Loess Plateau. These results provide reliable information for the diversity dynamic change as better indictors of soil quality and sustainable utilization mode.     

Potential responses of oligochaetes (Annelida, Clitellata) to global changes: Experimental fertilization in a lowland stream of Argentina (South America)

One of the possible consequences of climatic change for streams and rivers in the pampean region of South America is an increment in nutrient loads. To analyze this possible perturbation on a biological scale, the response of oligochaetes to an experimental eutrophication of the La Choza Stream, Argentina was studied. We proposed that the addition of nutrients could increase the abundance, biomass, and species composition of the stream. Two stretches (Control and Treatment sites) were selected, with bimonthly samples being taken (March 2007 through February 2009) in two habitat types: the sediments and the aquatic vegetation. On each sampling occasion the environmental variables were measured. The nutrient addition consisted in the continuous dissolution of a commercial fertilizer. The oligochaete mean density and total biomass, the taxonomic richness, the Shannon diversity (H′), and the evenness (E) were calculated and the BACI ANOVA design used to compare the differences between the sites. Thirty-three species of the families Naididae (Naidinae, Pristininae, Tubificinae, and Rhyacodrilinae), Opistocystidae, Enchytraeidae plus Aphanoneura Aeolosomatidae were collected. The oligochaete abundance and biomass increased significantly in the sediments and on the aquatic vegetation, especially among the Naidinae and Pristininae during their asexual reproductive phase. The diversity and evenness varied significantly in the sediments with the nutrient addition. Significant differences in the species richness and diversity were found on the aquatic vegetation, with both increasing at the treatment site after the fertilization. A significant correlation (Spearman) was observed between the oligochaete density in the sediments and the NO₃-N and NH₄-N concentration in the water. The increment in the naidines resistant to the fertilizer throughout the experiment could be explained by the greater nutrient availability, their mode of reproduction, and their short life cycles. The results of our study suggested that the incorporation of nutrients modified the composition of the oligochaete assemblage in favor of herbivores and detrivores. The usefulness of these indicator organisms in monitoring freshwater systems is subsequently discussed.     

Predicting fish species richness and assemblages with climatic,geographic and morphometric factors: A broad-scale study in Chinese lakes

The present study was designed to investigate the relative importance of climatic (temperature and precipitation), geographic (altitude) and morphometric (lake area) factors in predicting fish species richness and assemblages in Chinese lakes at a large spatial scale. Two recursive partitioning tree-based approaches: Classification and Regression Trees (CARTs) and Multivariate Regression Trees (MRTs) were employed to generate predictive models respectively. Six fish assemblages were thus defined from the MRT model. The results indicated that lake altitude was the main determinant for predicting fish assemblages in Chinese lakes (30.43%), followed by precipitation of the driest month (10.47%), temperature annual range (3.62%) and annual mean temperature (3.15%). Validated CART model implied that precipitation of driest month, maximum temperature of warmest month and lake area were the main predictors in determining fish species richness patterns. Overall, our results indicated that the altitudinal extent and range of climatic variation was sufficient to overshadow the area effect in predicting fish species richness and assemblages in Chinese lakes. At the macroecological scale, the effect of temperature and precipitation on fish richness and assemblages also suggests future changes in fish diversity as a consequence of climate change.     

Decline in the species richness contribution of Echinodermata to the macrobenthos in the shelf seas of China

Echinoderms play crucial roles in the structure of marine macrobenthic communities. They are sensitive to excess absorption of CO₂ by the ocean, which induces ocean acidification and ocean warming. In the shelf seas of China, the mean sea surface temperature has a faster warming rate compared with the mean rate of the global ocean, and the apparent decrease in pH is due not only to the increased CO₂ absorption in seawater, but also eutrophication. However, little is known about the associated changes in the diversity of echinoderms and their roles in macrobenthic communities in the seas of China. In this study, we conducted a meta-analysis of 77 case studies in 51 papers to examine the changes in the contribution of echinoderm species richness to the macrobenthos in the shelf seas of China since the 1980s. The relative species richness (RSR) was considered as the metric to evaluate these changes. Trends analysis revealed significant declines in RSR in the shelf seas of China, the Yellow Sea, and the East China Sea from 1997 to 2009. Compared with the RSR before 1997, no significant changes in mean RSR were found after 1997, except in the Bohai Sea. In addition, relative change in the RSR of echinoderms and species richness of macrobenthos led to more changes (decrease or increase) in their respective biomasses. Our results imply that changes in species richness may alter the macrobenthic productivity of the marine benthic ecosystem.     

The response of Clitellata (Annelida) to environmental gradients in spring fens

Patterns in aquatic Clitellata assemblage composition are known to be driven by several environmental gradients, with water chemistry and substratum characteristics being particularly important. In this study we explored 54 isolated spring fens across the eastern Czech Republic and Slovakia. These fens varied in calcium and magnesium concentrations, forming a sharp and well defined environmental gradient running from calcium-poor acidic fens to extremely calcium-rich tufa-forming fens. We found that the main changes in clitellate species composition were controlled by this gradient, and/or total organic carbon content, over a wide area, including fen sites differing in other environmental conditions and historical development. However, this pattern was weakened in sites with a high organic matter content, which represented a second driver of change in assemblage composition along with water temperature. Three main types of fens were determined using cluster analysis based on clitellate assemblage composition. However, only the first type, which included tufa-forming fens, was found to fit with the previously established spring fen types based on vegetation (i.e. extremely mineral-rich fens with a tufa, brown-moss mineral-rich fens, mineral-rich Sphagnum fens and mineral-poor Sphagnum fens). The second clitellate type included sites with low temperatures and occasional desiccation, while the third type was characterised by high temperatures and trophy. Using eight environmental predictors, we were able to significantly explain changes in the population abundances of all 12 common species (i.e. recorded at 15-plus sites). The results from individual species modelling also suggests that an increase in organic matter content can trigger compositional shifts towards assemblages of common eurytopic tubificid species. Thus, human-induced eutrophication and negative changes in spring fen hydrology, mainly drying up, can represent a serious threat for species-specific assemblages of aquatic clitellates, especially at alkaline sites due to their isolated and spatially limited nature.     

基于卫星轨道扰动理论的重力反演算法

为了更充分利用低轨重力卫星的高精度观测数据,根据卫星轨道的扰动理论,导出了应用卫星轨道与星间距离观测值联合反演地球重力场模型的算法.该算法的实质是将牛顿运动方程在卫星轨道处进行展开,转化为第二类Volterra积分方程,并采用基于移动窗口的9次多项式内插公式进行数值求解.给出了该算法的观测方程,用QR分解法消去局部参数矩阵,最后采用预条件共轭梯度法求解法方程.利用GRACE卫星2008-01-01~2008-08-01时间段内的轨道及星间距离观测数据,解算了120阶次的地球重力场模型SWJTU-GRACE01S,该模型在120阶处的阶方差为1.58×10^-8,大地水准面差距累计误差为22.29 cm,与美国GPS水准网比较的标准差为0.793 m,结果表明:SWJTU-GRACE01S模型精度介于EIGEN-GRACE01S与EIGEN-GRACE02S模型之间,从而验证了该算法的有效性.     

Derelict fishing nets in Puget Sound and the Northwest Straits: Patterns and threats to marine fauna

Derelict fishing gear remains in the marine environment for years, entangling, and killing marine organisms worldwide. Since 2002, hundreds of derelict nets containing over 32,000 marine animals have been recovered from Washington’s inland waters. Analysis of 870 gillnets found many were derelict for years; most were recovered from northern Puget Sound and high-relief rocky habitats and were relatively small, of recent construction, in good condition, stretched open, and in relatively shallow water. Marine organisms documented in recovered gillnets included 31,278 invertebrates (76 species), 1036 fishes (22 species), 514 birds (16 species), and 23 mammals (4 species); 56% of invertebrates, 93% of fish, and 100% of birds and mammals were dead when recovered. For all taxa, mortality was generally associated with gillnet effectiveness (total area, age and condition, and suspension in the water). Mortality from derelict fishing gear is underestimated at recovery and may be important for species of economic and conservation concern.     

长江口北支湿地鸟类多样性研究——鸟类物种多样性研究

通过对长江口北支湿地鸟类资源的野外实地调查,共记录到鸟类16目41科216种。鸟类以水鸟为主,其中鸻鹬类、雁鸭类、鹭类、鸥类为水鸟的优势类群,鸻鹬类在种类、数量上最多;以非繁殖鸟(冬候鸟和旅鸟)为主;东洋界种占绝对优势,其次为广布种,古北界种所占比例最小;濒危和珍稀鸟类种类较多,数量较少,且以水鸟为主,湿地生境是其主要生境。鸟类的G指数为4.38,F指数为23.03,G-F指数为0.81,与黄河三角洲湿地和闽江河口湿地相比,长江口北支湿地鸟类的科间多样性和属间多样性均较高。