Edge tree functional traits and their association with edaphic factors in seasonally dry forests in northern Thailand

Abstract

The relationships between plant traits and soil properties in forest edges can provide insights into tree species recovery in edge habitats. In this study, we investigated the relationships between plant functional traits and soil conditions related to tree species recovery at the edges of two seasonally dry forests, a mixed deciduous forest (MDF) and a deciduous dipterocarp forest (DDF) in northern Thailand. We analyzed differences in functional trait diversity and community-level trait values between forests and performed RLQ analysis to assess the associations among species abundance, plant traits, and soil variables. We found that the MDF site had greater functional diversity and was dominated by plants with high specific leaf area (SLA) and leaf dry-matter content (LDMC) at the community level, whereas the DDF site had lower diversity and was dominated by plants with high wood density (WD) and leaf thickness (LT). The RLQ results indicated that at the MDF site, tree species with greater SLA (e.g., Pterocarpus macrocarpus, Dalbergia cultrata, and Phanera bracteata) were associated with soil clay content and nutrient status (i.e., nitrogen and calcium). Species with greater LDMC and leaf size (e.g., Xylia xylocarpa, Schleichera oleosa, and Chukrasia tabularis) were associated with soil organic matter content. At the DDF site, species with greater WD and LT (e.g., Dipterocarpus obtusifolius, Shorea siamensis, and Buchanania lanzan) were associated with soil sand content and bulk density. These patterns reflect the interplay between soil conditions and plant traits in the edge habitats of seasonally dry forests. Our results indicate that the edge effects on plant communities within seasonally dry forests depend on soil conditions and species-specific plant traits.