长白山森林生态系统凋落物层和土壤层跳虫物种多样性和功能多样性对海拔梯度的响应

山脉是生物多样性研究的热点地区,以往关于山脉的研究多集中于地上植物和脊椎动物,无脊椎动物相关的研究明显滞后。跳虫(Collembola)是土壤无脊椎动物的主要类群之一,在分解有机质、疏松和活化土壤过程中发挥着重要的作用。以跳虫为研究对象,采用梯度格局法,在长白山北坡自海拔800 m至1700 m,每隔150 m进行凋落物层和土壤层样品的采集,对比分析了土壤层和凋落物层的群落组成与群落结构,采用4个物种多样性指数(丰富度指数、Pielou均匀度指数、Shannon-Weiner多样性指数和Simpson多样性指数)和4个功能多样性指数(功能丰富度FRic指数、功能均匀度FEve指数、二次熵Rao''s Q指数和功能离散FEiv指数),探讨了多样性沿海拔梯度的分布格局。共获得跳虫5542头,隶属于12科42属83种,其中等节跳科为绝对优势类群(相对密度>50%)。非度量多维尺度分析结果表明,凋落物层和土壤层的跳虫群落结构差异显著,长角跳科、鳞跳科和疣跳科物种多分布于凋落物层,而棘跳科物种多分布于土壤层。线性或二次回归模型结果表明,在凋落物层跳虫的丰富度指数,Shannon-Weiner多样性指数和Simpson多样性指数沿海拔梯度的变化呈增加格局;但在土壤层跳虫物种多样性指数沿海拔梯度的变化无明显趋势。在凋落物层,跳虫的功能丰富度指数和功能离散度Rao''s Q指数随海拔梯度的变化呈现单峰分布格局;在土壤层,跳虫的功能丰富度指数随海拔梯度的变化也呈现单峰分布格局,但其他功能多样性指数沿海拔梯度的变化无明显趋势。研究表明凋落物层和土壤层跳虫的群落组成,群落结构及多样性存在显著差异,跳虫的物种多样性指数和功能多样性指数对海拔梯度变化的响应不同,未来在探讨土壤动物沿海拔梯度的分布格局及其物种共存机制时,应综合考量垂直分层(凋落物层和土壤层)和多个度量维度(物种多样性和功能多样性)。

Taxonomic and functional diversity of Collembola in litter and soil along an altitudinal gradient at Changbai Mountain,China

Mountains are hotspots for biodiversity research because they harbor high number of species and cover a wide range of abiotic factors along altitudes. Compared with above-ground plants and animals, soil animal communities along altitudinal gradients have been little studied. Collembola are among the most abundant soil invertebrates contributing to essential ecosystem functions such as decomposition processes. We used Collembola as model soil animals and analyzed changes in their community structure in litter and soil of forests along a gradient ranging from 800 to 1700 m at the Changbai Mountain. Further, changes in four taxonomic diversity indexes (richness index, evenness index, Shannon-Wiener index, and Simpson diversity index) and four functional diversity indexes (functional richness index, functional evenness index, Rao''s quadratic index, and functional divergence index) were studied. A total of 5,542 Collembola individuals, belonging to 12 families, 42 genera, and 83 species were sampled, with Isotomidae being most dominant (>50% of total individuals). Non-metric multidimensional scaling showed that Collembola community composition varied in both litter and soil. Species of Entomobryidae, Tomoceridae, and Neanuridae mostly colonized the litter layer, whereas Onychiuridae mostly colonized the soil. We used linear and quadratic regression models to explore altitudinal patterns in Collembola diversity. In litter, the richness, Shannon-Wiener diversity index and Simpson diversity index significantly positively correlated with altitude. By contrast, in soil, the taxonomic diversity indexes did not change significantly with altitude. For functional diversity, in litter functional richness index and Rao''s quadratic index followed a hump-shaped pattern along the altitudinal gradient. In soil the functional richness index also showed the same trend, but other functional diversity indexes did not change in a consistent way with altitude. Overall, the results highlight that it is crucial to consider the vertical distribution of soil animals in litter and soil, and use multiple dimensions including taxonomic and functional diversity measures for understanding changes in diversity patterns of soil fauna along altitudinal gradients.