Community assembly in a tropical cloud forest related to specific leaf area and maximum species height

Abstract

AbstractQuestionWe tested whether co‐existing tree species in tropical dwarf forests were deterministically assembled along gradients of air temperature, relative humidity and light availability, according to two important functional traits, specific leaf area (SLA) and maximum species height (Hmax).LocationTropical montane cloud forest, Bawangling Nature Reserve, Hainan Island, south China.MethodsNull model analyses were used in conjunction with trait and species composition data collected to test our hypotheses at four plot sizes (25 m2, 100 m2, 400 m2 and 900 m2), addressing whether the consistent importance of variation in SLA and Hmax extends to these unique forests, as well as theoretical predictions concerning how patterns change with plot size.ResultsLow SLA species were significantly over‐represented within forest communities for the two largest plot sizes, and taller‐growing tree species were over‐represented across all four plot sizes. Plot‐level analyses indicated that low SLA species were associated with lower temperatures.ConclusionsOur results show that tropical dwarf forests are deterministically assembled with respect to these two traits, and are consistent with other studies indicating that SLA responds to abiotic filters. Co‐existing tree species were not significantly divergent for these two traits, indicating that variation in these two traits among trees does not contribute to niche differences (i.e. limiting similarity) and therefore co‐existence within forest plots. Finally, our study demonstrates that patterns of community assembly change with plot size; however, trait convergence did not increase with plot size as previously predicted.