Data from: Of niche differentiation, dispersal ability and historical legacies: what drives woody community assembly in recent Mediterranean forests?

Community assembly rules have been extensively studied, but its association with regional environmental variation, while land use history remains largely unexplored. Land use history might be especially important in Mediterranean forests, considering their historical deforestation and recent afforestation. Using forest inventories and historical (1956) and recent (2000) land cover maps, we explored the following hypotheses: 1) woody species assembly is driven by environmental factors, but also by historical landscape attributes; 2) recent forests exhibit lower woody species richness than pre-existing due to the existence of colonization credits; 3) these credits are modulated by species’ life-forms and dispersal mechanisms. We examined the association of forest historical type (pre-existing versus recent) with total species richness and that of diverse life-forms and dispersal groups, also considering the effects of current environment and past landscape factors. When accounting for these effects, no significant differences in woody species richness were found between forest historical types except for vertebrate-dispersed species. Species richness of this group was affected by the interaction of forest historical type with distance to coast and rainfall: vertebrate-dispersed species richness increased with rainfall and distance to the coast in recent forests, while it was higher in dryer sites in pre-existing forests. In addition, forest historical types showed differences in woody species composition associated to diverse environmental and past landscape factors. In view of these results we can conclude that: 1) community assembly in terms of species richness is fast enough to exhaust most colonization credit in recent Mediterranean forests except for vertebrate-dispersed species; 2) for these species, colonization credit is affected by the interplay of forest history and a set of proxies of niche and landscape constraints of species dispersal and establishment; 3) woody species assemblage is mostly shaped by the species’ ecological niches in these forests.群落装配（community assembly）规律已得到广泛研究，但群落装配与区域环境变异的关联，以及土地利用历史的影响，目前仍在很大程度上未被充分探索。考虑到地中海森林曾经历过历史上的砍伐活动与近期的造林工程，土地利用历史在该类森林中可能尤为重要。本研究借助森林清查数据，以及1956年的历史土地覆盖图与2000年的近期土地覆盖图，对以下假说展开了探索：1) 木本物种装配既受环境因子驱动，同时也受到历史景观属性的影响；2) 由于定植信贷（colonization credit）的存在，新近形成的森林的木本物种丰富度会低于原生森林；3) 这些定植信贷会受到物种生活型（life-form）与扩散机制的调控。我们探究了森林历史类型（原生林与新近林）与总物种丰富度、不同生活型类群以及不同扩散类群的物种丰富度之间的关联，同时也考虑了当前环境与历史景观因子的影响。在控制上述影响因子后，研究发现，除脊椎动物扩散类群的物种外，两类森林历史类型的木本物种丰富度并无显著差异。该类群的物种丰富度受到森林历史类型与距海岸距离、降雨量的交互作用影响：在新近林中，脊椎动物扩散类群的物种丰富度随降雨量增加以及距海岸距离增大而升高，而在原生林中，该类群的物种丰富度在更为干旱的生境中更高。此外，两类森林历史类型的木本物种组成差异，与多种环境因子及历史景观因子相关联。基于上述研究结果，我们可以得出以下结论：1) 就物种丰富度而言，地中海森林新近林的群落装配过程足够快速，能够耗尽除脊椎动物扩散类群之外的大部分定植信贷；2) 对于该类群而言，定植信贷受到森林历史与一组表征物种扩散和定植的生态位（niche）及景观限制因子的交互作用影响；3) 在该类地中海森林中，木本物种装配主要由物种的生态位所塑造。