里海西北部Caspian地区草原扩大与啮齿类群落结构的变化

于1997-1999年检测了俄联邦卡尔梅克(Kalmyki)共和国ChernieZemly半干旱草原由10个物种组成的啮齿类群落。该区域的植被特点是家畜大量减少后形成的恢复植被。我们的任务之一就是了解不同啮齿动物的生境需求,以预测不同物种对环境变化的特异性反应。我们也检测了群落空间结构、生态位参数和物种多样性。逐步回归分析表明,各种啮齿动物的空间分布仅部分地决定于已知环境因子(2-6个变量)。虽然方程式具有强显著性,但决定系数R2很低,不超过18%。对于大多数种类,这种结果可由最近草原扩大而来的生境异质性降低解释。物种生境选择条件和资源的明显低水平可能是由物种对环境变化的惯性反应造成的。判别函数分析和主分量分析结果表明,群落结构以及单个物种的生态位参数在不同年间并不稳定。空间分层结构在种间中等和低重叠的高物种多样性年度表现明显。多样性、生态位组成和生态位宽度分析结果表明,不同物种对环境条件和资源变化的反应具有不同的个性化方式。同时,物种对环境动态的明显个性化反应成为物种多样性定向变化的原因。限定空间和相对单一条件下的结果表明,啮齿类α多样性与生境结构复杂性呈正相关,而与生境生产力特征呈负相关。观察表明,卡尔梅克国草原扩大伴随着初级生产力的升高和生境异质性的降低。随着时间的推移会导致大多数草原和半干旱区域啮齿类多样性的降低,并形成动物区系核心.

Steppe expansion and changes in the structure of the rodent community in north-western Caspian region (Republic of Kalmykia, RF)

In 1997-1999 I examined a 10-species rodent community in "Chernie Zemly", a semi-desert region in the Republic of Kalmykia (Russian Federation). The region was characterized by a restoration succession of vegetation after a ten-fold decrease of live-stock. One task was to understand the habitat requirements of rodent species in order to predict species-specific responses to environmental changes. I also examined spatial patterns of community structure, niche parameters and species diversity. Stepwise Regression Analysis showed that spatial distribution of each rodent species was only partly determined by known environmental variables (from two to six variables) with significant regression coefficients. Although the equations were strongly significant, the R2 values were low, not exceeding 18%. For most species, this result can be explained by recent steppe expansion associated with a decrease of habitat heterogeneity. The apparently low level of species' selection of habitat conditions and resources may be the result of some inertia in species' responses to environmental changes. Results obtained using Discriminant Function Analysis and Principal Component Analysis signifies that the community structure, as well as parameters of individual species' niches were not stable from year to year. Spatial guild structure was well expressed during a year of high species abundance when niche overlap was higher in pairs of species with moderate and low overlap. Results of analysis of abundance, niche position and niche breadth show that species tend to respond to fluctuating conditions and resources in their own individualistic manner. At the same time, a well pronounced individualism in responses of species to the environmental dynamic may become a reason for directional change in species diversity. Results provided in a limited spatial scale with relatively uniform conditions show that rodents' α-diversity correlates positively with habitat structural complexity and negatively with characteristics of habitat productivity. The observed steppe expansion in Kalmykia means an increase of primary productivity and a decrease in habitat heterogeneity. Over time this process may lead to a decrease of abundance and diversity of rodents of mostly desert and semi-desert origin, that still form a nucleus of the fauna.