土地利用对长江中游河流大型无脊椎动物多样性格局的影响

Anthropogenic land use has been identified as one of the major stresses dramatically altering many aspects of biological activities in the Central Yangtze rivers, especially its biodiversity decline. However, the knowledge about the process and mechanism linked to this human-induced intervention driving this decline remains yet limited, particularly its macroinvertebrate assemblages. Hence, we address this issue by choosing the Du River, the largest tributary of the Han River, located in a biologically interesting transition between northern-tropic and warm-temperate regions, as one-case study. The aims of this study concentrate mainly on the impacts of land use on three aspects (α, β and γ) of macroinvertebrate species diversity in the whole watershed scale. Firstly, we depict the key characteristics of α and γ diversities within its two major influents (Huiwan and Guandu Rivers) subjected to different land exploitation (e.g., forest, agricultural use and urbanization), then detect their differences within and between these tributaries. Secondly, we explore the β diversity patterns within and between the influents. Then combining these β traits with determined environmental parameters involved by the land development, we can identify the key factors driving the detected β diversity patterns. Finally, by integrating these factors into a proposed statistic framework, we could determine their roles on different aspects of species diversity patterns in different strength, direction and to some extent. Thus, this study could reveal the key process and mechanisms implicated in land use driving lotic macroinvertebrate diversity in different spatio-temporal scales and scenarios. These results should further promote the understanding of land use effects on diversity patterns from a variety of viewpoints, and can provide important background for landscape assessment, management and conservation planning.

大规模的土地利用已显著改变长江中游河流生物多样性的分布格局。而对由土地开发驱动这一地区河流生物多样性下降的关键过程和机制的认识仍然十分有限，特别是对大型无脊椎动物。项目拟以汉江最大的支流——堵河为研究地域，系统开展该流域土地利用格局对大型无脊椎动物物种多样性三个层面(α、β和γ)影响的研究。首先，描述α和γ多样性在该流域两大支流(汇湾河和官渡河)内的时空动态及变化规律，并分析在不同土地利用条件下α和γ多样性在两支流间的差异。其次，刻画β多样性格局在两支流内/间的分布规律、差异及水平，并甄别出由土地利用引起的驱动这些格局变化的关键环境参数和它们的变化过程和途径。最后，将这些关键驱动因子纳入设定的统计框架，解析它们各自/联合的作用力大小、方向和水平，揭示在不同时空尺度及场景下驱动大型无脊椎动物多样性格局的关键过程和机制。研究结果可为河流生物多样性评价、流域系统管理、开发和保护等提供科学支撑。

本项目通过对汉江最大支流——堵河流域大型无脊椎动物的生态调查，分析了该流域内不同土地利用类型下河流环境特征和大型无脊椎动物群落多样性格局(alpha、beta和gamma)的变化规律。首先，对不同土地利用类型下的河流环境特征进行比较，单因素方差分析显示，在四组样点中，城镇型样点的水质具有最高的电导、氮盐、磷酸盐和化学需氧量；森林型样点的以上水质指标则处于最低的水平，农田型样点水质指标值则处于两者之间，表明自森林—农田—城镇样点水质状况逐渐恶化的趋势。坝下型样点有与流域面积不相称的较小河宽与流速，说明大坝对河流流量的影响颇大。其次，分析不同土地利用条件下alpha和gamma多样性的差异，在alpha多样性方面，物种丰富度、Shannon-Wiener和Simpson多样性指数均呈现森林型样点最高，农田型样点次之，城镇和坝下样点最低的趋势；在gamma多样性方面，流域面积较小的官渡河却具有比流域面积较大的汇湾河更高的物种丰富度(145 vs. 138)、Shannon-Wiener指数(3.919 vs. 3.748)、Simpson指数(0.960 vs. 0.956)和均匀度指数(0.788 vs. 0.761)。之后，利用NMDS分析和扩散同质性检验分析比较beta多样性格局的差异，结果显示，不同土地利用类型样点间的beta多样性差异显著，森林型和农田型样点的beta多样性显著高于城镇和坝下样点。最后，采用基于距离的线性模型和基于距离的冗余度分析分别对alpha多样性指数—环境和群落结构—环境关系进行分析，结果显示，影响物种丰富度、Shannon-Wiener、Simpson和Evenness多样性指数的关键环境因子不尽相同，总体而言，%城镇、海拔、底质类型、TP和溶解氧是影响各alpha多样性指数的关键环境变量。影响群落结构的关键环境变量为海拔、各土地利用类型百分比，水温、电导和溶解氧，说明土地利用类型、受土地利用影响的水体理化参数和海拔对大型无脊椎动物的beta多样性均有着显著影响。本研究基于物种多样性的不同层面(alpha、beta和gamma)，揭示了土地利用开发背景下大型无脊椎动物多样性格局的关键驱动过程和机制，为河流生物多样性评价、流域系统管理、修复和保护等提供了科学支撑。