A Functional Basis for the Assembly of Australian Subtropical Rainforest Tree Communities

Understanding the role of climate in the assembly of rainforest tree communities is informative for predicting how future climates will impact species and communities. We surveyed rainforest tree communities across the Australian subtropics (spanning 600 to 2500 mm rainfall year^-1) and measured functional traits on 285 (91%) of all recorded species. We used principal component analysis to create axes approximating species' hydraulic strategies, leaf economics and stature and included these as predictors in joint species distribution models, along with traits describing dispersal ability and leaf phenology. Hydraulic strategy and leaf phenology strongly modulated species' occurrence trends along the moisture availability gradient, while stature and leaf economics modulated species' responses to minimum temperature and soil variables, respectively. Overall, we quantify the occurrence trends of almost half of Australia's subtropical rainforest tree species based on their functional traits, providing a general foundation for prediction under ongoing climate change.