南亚热带常绿阔叶林冠层和林下层优势种叶功能性状响应异质生境的差异 postprint

Abstract: Plant species can adapt to heterogeneous habitats through variations in functional traits. For the plants with different growth forms, how to adjust their phenotypes to adapt to the environment has been one of the core topics in ecology. To clarify the response mechanisms of plant species with different growth forms to heterogeneous habitats in south subtropical forests, we measured a total of 8 functional traits involving 4 structural traits (leaf thickness, leaf length/width ratio, leaf dry matter content and leaf specific leaf area) and 4 stoichiometric traits (leaf N concentration, leaf P concentration, 13C and 15N) of 5 dominant trees (2 canopy species and 3 understory species) and their diameter at breast height, in 27 quadrats (20 m × 20 m) at different elevations and convexity along three mountain ridges within the 20-hm2 lower subtropical evergreen broad-leaved forest plot at Dinghu Mountain in Guangdong Province. We analyzed and compared the differences in responses of the canopy and understory species to different elevations and convexity in terms of functional traits. The results were as follows: (1) There existed some leaf functional traits in each tree species that were significantly correlated with altitude, but for convexity, only the leaf area of Cryptocarya chinensis was positively correlated with convexity and the leaf nitrogen content of Blastus cochinchinensis was negatively correlated with convexity. (2) Specific leaf area, leaf thickness and 15N were generally more responsive to elevation, while leaf length/width ratio and leaf dry matter content were less responsive. (3) There were significant differences in specific leaf area, leaf dry matter content and leaf N concentration between canopy and understory tree species in heterogeneous habitats. Compared with canopy tree species, understory tree species had lower leaf thickness, leaf dry matter content and  13C. Moreover, canopy and understory species responded to elevation and convexity to different extents, with understory species having more functional traits with significant differences in different types of habitats. The results indicate that the degree of response to the environment varied greatly between plants with different growth forms, i.e., the dominant understory tree species had greater plasticity in the heterogeneous habitats than the dominant canopy species in the forest plot. In addition, specific leaf area, leaf thickness and 15N are important and effective traits indicating plant adaptation and responses to the environment in the lower subtropical evergreen broad-leaved forest.