Lianas shift towards larger sizes and more acquisitive trait values in an Asian tropical rainforest

Global change is impacting forests worldwide, leading to shifts in forest dynamics and functional composition. We evaluated the changes in the liana community and trait composition over a five-year period (2014–2019) in a Chinese tropical rainforest and assessed the underlying putative mechanisms. We monitored >20,000 lianas in a 20-ha plot, and analyzed community changes for each of the 20 1-ha plots. To identify the putative drivers underlying community change, we used community-weighted mean (CWM) trait values of 18 functional traits that are important for liana performance. During the 5-year period, liana density decreased by 12.6% because of the high mortality of small lianas, whereas liana basal area increased by 5.8% because of the high growth of large lianas. After 5 years, liana communities showed a shift in trait values indicating that they changed towards more large, acquisitive lianas with rapid water use. The temporal shift from slow to fast community trait spectra in carbon, nutrient, and water use was also supported by shifts in the individual CWM traits, from conservative tough leaves towards more acquisitive and water-spending leaves with higher K concentration, leaf thickness, and vessel diameter. Overall, we found no support for a role of disturbances or drought as drivers of the observed changes in the studied liana community. Instead, our study implies that CO₂ fertilization should be considered to better understand dynamics in liana communities in tropical forests.

Abstract in Chinese is available with online material.