Edaphic fauna in a vegetation gradient in the Sete Cidades National Park

Abstract The vegetation physionomy and cover can show patterns of diversity and composition of the edaphic community, depending on the quantity and quality of litter in a specific habitat. The objective of this study was to evaluate the effect of the vegetation gradient formed by Graminoid Field (GRF), Cerrado Sensu Stricto (CSS), Cerradão (CRD) and Semideciduous Seasonal Forest (SSF) on density, diversity and composition of the edaphic fauna community in two seasons of the year, in the Sete Cidades National Park (Piauí state). For fauna sampling, a total of eight pitfall traps, distanced 10 m, were placed in each area in the central part of each system, where they remained for seven days. In the wet period, there was a tendency to increase the number of individuals as a function of the complexity of the vegetation formation, with the inverse occurring in the dry period. It was verified an environmental variation of the climatic factors temperature and humidity according to the vegetal formation, contributing to a heterogeneous distribution of the fauna. The GRF formation presented a significantly lower value of average richness only in the dry period. Regarding the variables of diversity and uniformity, they did not show drastic variations in relation to the vegetation gradient studied. The dominant groups in the vegetation gradient were Formicidae, Coleoptera, Aranae, Acari and Collembola, with reduction of the number of Coleoptera in the dry season. Principal component analysis (PCA) revealed greater differences in the composition of the communities between the vegetation formations for the rainy season. At this time, the formations SSF and CRD were associated to a greater diversity of invertebrates than CSS and GRF, demonstrating the influence of the vegetation complexity on the soil fauna community.摘要 植被外貌与盖度可反映土壤动物群落的多样性与组成模式，其关联取决于特定生境中枯落物的数量与质量。本研究旨在评估由禾草群落（Graminoid Field, GRF）、塞拉多狭义稀树草原（Cerrado Sensu Stricto, CSS）、密灌塞拉多（Cerradão, CRD）与半落叶季节性林（Semideciduous Seasonal Forest, SSF）构成的植被梯度，对一年中湿季与旱季内巴西皮奥伊州塞特西达德斯国家公园内土壤动物群落（edaphic fauna community）的密度、多样性及组成的影响。 动物群落采样采用巴氏陷阱（pitfall traps）：各植被系统的中心区域各布设8个间距10米的陷阱，持续放置7天。湿季时，个体数量随植被群落复杂度的提升呈上升趋势，旱季则呈现相反趋势。研究证实，气候因子（温度与湿度）随植被类型产生环境异质性变化，进而导致土壤动物群落呈现异质性分布。仅在旱季，禾草群落的平均类群丰富度显著低于其他植被类型。就多样性与均匀度指数而言，其在本次研究的植被梯度间未出现显著波动。植被梯度中的优势类群为蚁科（Formicidae）、鞘翅目（Coleoptera）、蜘蛛目（Aranae）、蜱螨亚纲（Acari）与弹尾纲（Collembola），旱季鞘翅目的个体数量有所减少。主成分分析（Principal Component Analysis, PCA）结果显示，湿季时不同植被类型对应的动物群落组成差异更为显著。此时，半落叶季节性林与密灌塞拉多的无脊椎动物多样性高于塞拉多狭义稀树草原与禾草群落，印证了植被复杂度对土壤动物群落的调控作用。