Divergent adaptation of different functional tree seedlings to precipitation changes in a secondary tropical forest

Abstract Seedling adaptation to precipitation change is of great significance for the development and succession of tropical forests under the global climate changes. Here, we conducted a field-based manipulative experiment to assess the performance of different functional seedling (Cassia siamea, N-fixing, and Syzygium hancei, non-N-fixing species) to altered precipitation pattern (control; wetter wet season, WW; delay dry season, DW) in a secondary tropical forest of southern China. The results showed that WW (wetter wet season) and DW (delay dry season) treatments significantly increased leaf mass per area (LMA) of S. hancei, however, precipitation treatment significantly decreased the leaf chlorophyll a concentration of C. siamea, while significantly increased leaf chl b and total chl contents of S. hancei. WW treatment significantly increased the relative grow rate (RGR) of height and total biomass of S. hancei seedling. Additionally, WW and DW treatments significantly increased the leaf soluble sugar concentrations of both seedlings, while DW significantly raised the starch concentration of leaf and coarse root of S. hancei. Moreover, DW treatment significantly enhanced leaf NSC concentrations of both seedlings in this tropical forests. It is surprising that WW treatment unregulated the allocation of soluble sugar, starch, and NSC of leaf and fine root in C. siamea. Thus, the variations of NSC storage and allocation among different tissues in two seedlings may directly reflect the different adapting mechanisms to altered precipitation pattern. Therefore, our results indicated that the S. hancei (non-N-fixing) seedling may adjust the NSC concentrations while the C. siamea (N-fixing) seedling may shift the NSC allocation among different organs adapting to the altered precipitation in the tropical forest.