School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China.
Department of Earth and Environmental Sciences, Macquarie University, Sydney 2109, Australia.
Sci Total Environ. 2021 Aug 15;782:146724. doi: 10.1016/j.scitotenv.2021.146724. Epub 2021 Mar 25.
Habitat degradation is expected to alter community structure and consequently, ecosystem functions including the maintenance of biodiversity. Understanding the underlying abiotic and biotic assembly mechanisms controlling temporal and spatial community structure and patterns is a central issue in biodiversity conservation. In this study, using monthly time series of fish abundance data collected over a three-year period, we compared the temporal community dynamics in natural habitats and poplar plantations in one of the largest river-lake floodplain ecosystems in China, the Dongting Lake. We found a prevailing strong positive species covariance, i.e. species abundance changes in the same way, in all communities that was significantly negatively impacted by higher water nutrient levels. In contrast to species covariance, community stability, which was measured by the average of aggregated abundance divided by temporal standard deviation, was significantly higher in poplar plantations than in natural habitats. The positive species covariance, which was consistent for both wet and dry years and among habitat types, had significantly negative effects on community stability. Furthermore, our results demonstrated that the ecological stochasticity (i.e. community assembly processes generating diversity patterns that are indistinguishable from random chance) was significantly higher in natural sites than in poplar plantations, suggesting that deterministic processes might control the community composition (richness and abundance) at the modified habitat through reducing species synchrony and positive species covariance observed in the natural habitats, leading to significantly lower temporal β-diversity. When combined, our results suggest that habitat modification created environmental conditions for the development of stable fish community in the highly dynamic floodplains, leading to niche-based community with lower temporal β-diversity.
生境退化预计会改变群落结构，并因此改变生态系统功能，包括生物多样性的维持。了解控制时间和空间群落结构和格局的基础非生物和生物组装机制是生物多样性保护的核心问题。在这项研究中，我们使用了三年间每月采集的鱼类丰度数据的时间序列，比较了中国最大的河湖泛滥平原生态系统之一——洞庭湖的天然生境和杨树林中的时间群落动态。我们发现，所有群落中都存在强烈的正物种协变，即物种丰度变化方式相同，这种协变受到较高的水养分水平的显著负面影响。与物种协变相反，群落稳定性（通过聚合丰度的平均值除以时间标准差来衡量）在杨树林中显著高于天然生境。这种在干湿年份和生境类型中都一致的正物种协变对群落稳定性有显著的负面影响。此外，我们的结果表明，生态随机性（即产生与随机机会无法区分的多样性模式的群落组装过程）在自然地点显著高于杨树林，这表明确定性过程可能通过减少物种同步性和在天然生境中观察到的正物种协变来控制经过改造的生境中的群落组成（丰富度和丰度），从而导致时间β多样性显著降低。综合来看，我们的结果表明，生境改造为高度动态泛滥平原中稳定鱼类群落的发展创造了条件，导致了基于生态位的群落，时间β多样性较低。
