Partitioning the functional variation of tree seedlings during secondary succession in a tropical lowland rainforest

Abstract

AbstractThe seedling stage is a key phase in the regeneration dynamics of forest communities. The functional diversity of tree seedlings is closely related to the structuring and functioning of forest ecosystems. Here, we examined and partitioned variations of tree seedlings in functional diversity over a chronosequence (younger secondary forest, 18–30 yr; older secondary forest, 60 yr; and old growth forest) after shifting cultivation in a tropical lowland rainforest area on Hainan Island, China. Results showed that the variations of seedling functional diversities revealed a unimodal pattern during the secondary succession. The functional diversities of seedlings were overall lower in the secondary than in old growth forests. The relative role of edaphic factors and tree community factors changed with the successional process. The variations in functional diversity explained by edaphic factors were higher than those by tree community factors in the younger secondary forest. However, with the procession of secondary succession, variations in functional diversities of seedlings explained by tree community factors were increasing. The determinants for functional diversities of seedlings varied with successional stages. Seedling functional diversities were affected by edaphic factors in the younger secondary growth forest. Meanwhile, in the older secondary forest, seedling functional diversities were affected mostly by soil nutrients and tree community factors. In the old growth forest, seedling functional diversities were affected by available nitrogen and tree community factors. Our results suggest that edaphic factors play an important role in the younger secondary forest, while tree community factors in the older secondary forest and unexplained factors in the old growth forest.