Functional diversity and composition of Caatinga woody flora are negatively impacted by chronic anthropogenic disturbance

Tropical plant assemblages can be taxonomically and phylogenetically impoverished by chronic anthropogenic disturbance (CAD), such as firewood collection and extensive grazing. However, to what extent the functional dimension responds to CAD is still unclear. Such knowledge is urgently required for predicting, preventing or even reversing the impacts of CAD.
Chronic anthropogenic disturbance may operate as an ecological filter by selecting functional trait values (e.g. low wood density), thereby altering the functional composition and diversity of plant assemblages. We tested this hypothesis using 29 woody plant assemblages across three ontogenetic stages (seedlings, saplings and adults) in a 220‐km2 landscape of the Caatinga, northeast Brazil. We adopted a CAD index consisting of four indicators (proximity to urban centre and houses and the density of both people and livestock) and tested how well it explained the functional diversity and effect sizes (richness, evenness and dispersio...

长期人为干扰（chronic anthropogenic disturbance，CAD）可导致热带植物群落在分类学与系统发育维度上出现多样性衰退，这类干扰涵盖薪柴采集与粗放放牧。然而，植物群落的功能维度在多大程度上会响应长期人为干扰，目前仍不明晰。相关研究认知对于预测、防控乃至逆转长期人为干扰的生态影响而言，需求迫切。
长期人为干扰可作为一种生态过滤因子，通过筛选功能性状数值（如较低的木材密度）发挥作用，进而改变植物群落的功能组成与多样性。我们依托巴西东北部卡廷加（Caatinga）区域内一片220平方千米的景观，针对3个个体发育阶段（幼苗、幼树与成年植株）的29个木本植物群落开展研究，以验证上述假说。我们采用了由4项指标构成的长期人为干扰指数，即距城镇与居民点的距离、人口密度以及牲畜密度，并检验该指数对功能多样性及效应量（丰富度、均匀度与离散度……）的解释效力。