Shading Gradients Drive Differential Responses of Leaf Traits in an Early Community Germinated by Forest Topsoil

Abstract

Seedling performance in the early stage is crucial to natural forest restoration, and functional traits have been widely employed in exploring plant adaptation under field conditions. However, the responses and variabilities of leaf traits have not been clearly defined at the light gradients that are used in restoration practices. We evaluated the variation in leaf treats in species and community levels in a controlled field plot with shading treatments. We found that the variation characteristics differed across different species and trait types along shading gradients. Individuals of most species had a larger leaf area (LA) and specific leaf area (SLA) in the shaded habitats, while only a few tree species showed significant responses in their leaf shape and chlorophyll concentration. Although LA and SLA showed similar directions and trends of changes in the trait mean, four response models were observed based on the light points corresponding to initial responses and following trends. The extent of within-species trait variation for each treatment was similar at the community level due to diverse changes in the direction and degrees of variation in co-occurring species. Intraspecific variation was limited within each shading treatment, while it noticeably contributed to the local adaptation in the entire heterogeneous restoration community. Our findings indicate that species with different trait combinations will have different responses to light gradients, and that the mean and degree of variation in leaf traits will also lead to distinctive strategies being created to match the different shading conditions. Vegetation restoration should consider the adaptive traits and their response diversity when selecting species and for habitat management with specific trait–environment interactions.