Variations In Leaf Traits With Plant Size And Leaf Height In Karst Forest Trees

Intraspecific trait variation is an important topic of functional ecology research.Investigating the drivers of intraspecific trait variation sheds light on plant adaptation strategies in heterogeneous environments.An important research direction of intraspecific trait variation is to understand the effect of plant development on plant leaf traits.Exploring how development shapes plant intraspecific leaf trait variation deepens our understandings of the drivers of intraspecific leaf trait variation.During plant development,the size of the plant increases and closer to the forest canopy,its light environment and water conductance also change,which drive the temporal change in individual-level leaf traits.In addition,even within the same plant,leaves at different height receive different light and differ in water conductance,which shape the spatial variations of individual-level leaf traits.Here,took the karst forests of Maolan National Nature Reserve in Guizhou as the study site,and the plant leaf traits in the karst forest as the research object,we explored how the leaf traits change with plant development（i.e.,plant size）,and how the traits differ between leaves at different heights of the same plant.We measured four leaf traits（i.e.,specific leaf area（SLA）,leaf area,leaf thickness,leaf dry-matter content（LDMC））of three common tree species in Maolan karst forests,including Clausena dunniana,Cyclobalanopsis glauca and Lindera communis,in two topographic habitats,namely hilltop and slope.We further measured two local-scale environmental factors（i.e.,the canopy height and the rock-bareness rate）.We explored the effects of plant size on the leaf traits,and we examined the difference in the traits of leaves at the upper and lower layers of the crown of the same plant for the three study species.By adopting statistical methods such as linear mixed-effects model and Wilocoxon signed-rank test,we found that（1）the leaf traits changed with plant size.Specifically,with plant size increased,SLA decreased,while leaf area and LDMC increased.After controlling for the effects of environmental factors,plant size still exerted similar effects on the leaf traits.When each topographic habitat was analyzed separately,plant size showed similar influences on leaf traits in each habitat,especially the hilltop,leaf traits shifted towards increasingly conserved resource-use strategies as plant size increased.（2）The differences in the leaf traits of the upper and lower crown layer of individuals were generally similar in the three study species.Specifically,the SLA and leaf area of the upper layer were smaller,but the leaf thickness was larger,than those at the lower layer.The differences commonly exist in each topographic habitat.These findings imply that leaves generally shifted towards resourceconservative strategies during plant development and with leaf height in the Maolan karst forests.This study deepens our understandings of the causes of intraspecific leaf traits spatial and temporal variations in Maolan karst forest woody plants,and provides support for karst forest conservation.