Assessing high compositional differences of beetle assemblages across vertical woodland strata in the New Forest, Hampshire, England

Closed-canopy woodlands are complex ecosystems with strong vertical environmental stratification. The degree to which this vertical stratification has led to compartmentalisation in invertebrate assemblages in temperate woodlands has been researched to a limited extent, yet there are still gaps in our understanding. Here, we used five different sampling methods to sample beetles across vertical strata of nine woodland sites in the New Forest National Park, Hampshire, England. The sampling methods yielded 2412 individuals across 157 species, of which 46 were significant indicator species for one stratum or a combination of strata. Multivariate analysis of composition showed a strong separation at a subfamily level between strata, with many only found in a single stratum. This suggests a strongly compartmentalised vertical stratification of the beetle assemblages at both species and higher taxonomic levels. Our results display that multiple strata need to be sampled to obtain true estimates of overall beetle species richness in woodlands and forests. Limitations in using a single sampling method and biases using mixed sampling method protocols across a vertical transect are also discussed.

郁闭林（Closed-canopy woodlands）是一类具备显著垂直环境分层的复杂生态系统。针对温带郁闭林中，该垂直分层是否推动无脊椎动物群落（invertebrate assemblages）产生分区现象的相关研究尚且有限，学界对该问题的认知仍存在诸多空白。本研究以英国汉普郡新森林国家公园内的9处林地样点为研究对象，采用5种不同采样方法，对各垂直分层中的甲虫（beetles）类群开展采集工作。本次采样共获取157个物种、总计2412个甲虫个体，其中46个为对应单一垂直分层或多层组合的显著指示物种。群落组成的多变量分析（multivariate analysis）结果显示，在亚科（subfamily）分类阶元层面，不同垂直分层间存在显著的群落分隔，多数甲虫类群仅在单一垂直分层中被采集到。这表明甲虫群落在物种及更高分类阶元层面均存在显著的垂直分层分隔现象。本研究结果证实，若要准确估算林地与森林中甲虫的整体物种丰富度（species richness），需对多个垂直分层进行采样。本文同时探讨了单一采样方法的局限性，以及在垂直样带（vertical transect）中混用采样方法方案所引发的采样偏差。