Relationships Between Hydraulic Traits And Species Abundance Changes In A Tropical Seasonal Rain Forest Community

Due to global climate change,shifts in rainfall patterns and increasing temperatures have increased the frequency and severity of droughts in Southwestern tropical regions of China.The drought-induced changes in the composition of tropical forest communities have been reported in several previous studies,but the underlying eco-physiological mechanisms are not fully understood.Hydraulic traits are vital to identify the drought adaptation of plant species.Exploring the relationships between key hydraulic traits and species abundance dynamics provides a powerful tool to predict the effects of climate change on community structure in the present region.This study was carried out in a permanent plot of a tropical seasonal rain forest in Xishuangbanna.Based on yearly community-survey?2004 ? 2015?,we calculated the slopes of the abundance-year relationship for each of the 46 studied tree species.The abundance of five species decreased significantly over time?Decrease?.Twenty species did not show any significant changes?Non-significant?.Twenty-one species increased in abundance?Increase?.For each species,we measured the specific leaf area?SLA?,sapwood density?WD?,sapwood-specific hydraulic conductivity?k_s?,leaf-specific hydraulic conductivity?k_l?,leaf / sapwood area ratio?A_l/A_s?and leaf water potential at turgor loss point(?_tlp).We examined the relationships between abundance-year slopes and hydraulic traits across species using linear regressions.Our results indicated that species abundance-year slopes were significantly related to ?_tlp,WD and k_s.Species with higher sapwood density,lower hydraulic conductivity and more negative ?_tlp increase in abundance.Conversely,decreased-abundance species have the opposite traits.However,species abundance-year slopes were not related to k_l,SLA and A_l/A_s,which may be related to the large species variation and seasonal change of these traits in tropical seasonal rainforests.This study demonstrates that hydraulic traits are good predictors of species abundance dynamics in tropical seasonal rainforest under global changes.Since several important hydraulic traits(e.g.,?_tlp and WD)can predict community abundance dynamics,and are easy to measure,we recommend that these hydraulic traits could be incorporated into traits-based models of community dynamics.