Abstract: Seedling adaptation to precipitation change is of great significance in the development and succession of tropical forests under global climate changes. Here, we conducted a field-based experiment to assess the performance of different functional seedlings (Cassia siamea, nitrogen (N)-fixing, and Syzygium hancei, non-N-fixing species) to altered precipitation patterns (control; wetter wet season, WW; delayed wet season, DW) in a secondary tropical forest of southern China. The results showed that WW and DW treatments significantly increased the leaf mass per area of S. hancei; however, precipitation treatment significantly decreased the leaf chlorophyll (chl) a content in C. siamea but significantly increased the leaf chl b and total chl contents in S. hancei. WW treatment significantly increased the relative growth rate of height and total biomass of S. hancei. Additionally, WW and DW treatments significantly increased the leaf soluble sugar contents of both species. DW treatment significantly increased the starch content of the leaves and coarse roots of S. hancei and significantly enhanced the leaf non-structural carbohydrate (NSC) contents of both species. WW treatment upregulated the allocation of soluble sugar, starch, and NSC in the leaves and fine roots in C. siamea. Thus, variations in NSC storage and allocation among organs in two species may directly reflect the different adaptation mechanisms to altered precipitation. Our results indicate that S. hancei adjusts the NSC contents, while C. siamea shifts the NSC allocation among different organs to adapt to the altered precipitation in tropical forests.

Key words: non-structural carbohydrate, leaf mass per area, photosynthetic pigment, precipitation pattern, secondary tropical forest