State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China.
State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China.
Sci Total Environ. 2019 Apr 1;659:150-160. doi: 10.1016/j.scitotenv.2018.12.310. Epub 2018 Dec 22.
The biodiversity value of river-oxbow lake systems in high plateau peatland has been little recognized, and there are many gaps in our understanding of their ecology. In this study, we investigated the river-oxbow lake system of the Bai River basin, the main tributary of the Yellow River Source in the Zoige wetland from 2015 to 2016, in attempt to show how the environmental variations, especially hydrological connectivity and macrophyte biomass in the river-oxbow lake system influenced macroinvertebrates. Habitat patches were investigated in 11 river cross-sections and 18 oxbow lakes in the Bai River basin. Through hierarchical clustering and non-metric multidimensional scaling, four main types of habitats were identified in the river-oxbow lake system in the plateau: sand-bed river, cobble-bed river, sparse-macrophyte oxbow lake, and luxuriant-macrophyte oxbow lake. The luxuriant-macrophyte oxbows were characterized by high dissolved oxygen concentrations, alkalinity, and higher macroinvertebrate richness, density, biomass, and the Improved Shannon-Wiener Index in comparison to the other habitat types. Additionally, influential patterns of environmental variables on macroinvertebrates were analyzed using redundancy analysis. Lasso regression models were established to describe how macroinvertebrate density responded to macrophyte biomass and other variables, and how macrophyte biomass responded to hydrological connectivity and oxbow size. It was revealed that reduced hydrological connectivity and reduced oxbow size played important roles in increasing the biomass of submerged macrophyte, and dense macrophyte was directly responsible for the high biodiversity of macroinvertebrates. Different from the commonly believed unimodal influential pattern that medium hydrological connectivity supports the highest biodiversity in oxbow lakes reported in previous studies, macroinvertebrates in the high plateau river-oxbow lake systems benefited from low connectivity and reduced size. Oxbow lakes, especially those covered with luxuriant macrophytes, diversified the macroinvertebrate assemblages and enhanced primary consumer biomass at the regional scale.
高海拔泥炭地河流牛轭湖系统的生物多样性价值尚未得到充分认识，我们对其生态的了解还存在许多空白。本研究于 2015 年至 2016 年期间，调查了黄河源区主要支流之一若尔盖湿地白河河流牛轭湖系统，旨在展示环境变化，特别是河流牛轭湖系统的水文连通性和大型植物生物量如何影响大型无脊椎动物。在白河流域的 11 个河流横断面和 18 个牛轭湖中调查了栖息地斑块。通过层次聚类和非度量多维标度，确定了高原河流牛轭湖系统中的四种主要栖息地类型：沙底河流、卵石底河流、稀疏大型植物牛轭湖和繁茂大型植物牛轭湖。与其他栖息地类型相比，繁茂大型植物牛轭湖具有较高的溶解氧浓度、碱度以及较高的大型无脊椎动物丰富度、密度、生物量和改进的 Shannon-Wiener 指数。此外，还使用冗余分析分析了环境变量对大型无脊椎动物的影响模式。使用套索回归模型来描述大型无脊椎动物密度如何响应大型植物生物量和其他变量，以及大型植物生物量如何响应水文连通性和牛轭湖大小。结果表明，减少水文连通性和减少牛轭湖大小在增加淹没大型植物生物量方面发挥了重要作用，而密集的大型植物直接导致了大型无脊椎动物的高生物多样性。与先前研究中普遍认为的中水文连通性支持牛轭湖中最高生物多样性的单峰影响模式不同，高原河流牛轭湖系统中的大型无脊椎动物受益于低连通性和减小的规模。牛轭湖，特别是那些覆盖着繁茂大型植物的牛轭湖，在区域尺度上多样化了大型无脊椎动物组合，并提高了初级消费者的生物量。
