Intraspecific Trait Variability:Extent, Sources And Spatial Structure In An Evergreen Broad-leaved Forest In Tiantong, Zhejiang Province

Functional traits are increasingly used to investigate community structure, ecosystem functioning or to classify species into functional groups where the focus is on trait differences between co-occurring species. However, several recent studies have shown that intraspecific trait variability (ITV) can have significant effects on ecosystem functioning. Investigation into ITV may open a new opportunity to better understand the underling mechanisms of community assembly.Based on this, we carried out the field experiment of plant functional traits on a 4.84ha fixed sample plots located in the 20ha evergreen broad-leaved forest dynamics plot in Tiantong, Zhejiang province. We only choose Individuals of species with frequency≥50, and four functional traits were measured. Through the use of linear mixed model, variance component analysis, Rao index and spatial point processes, we addressed the three following questions:(i) Is intraspecific trait variability negligible compared to interspecific trait variability? (ii) How are the α and β diversity of intraspecific trait structured across different spatial scales? (iii) How the intraspecific trait variability changes with the increasing of spatial scale? And what is the underling ecological process?The research findings were as follows:1) The intraspecific trait variability was not negligible compared to interspecific trait variability. And the extent of intraspecific trait variability is related to species and traits. Besides, there were negative relationship between intraspecific trait variability and species’abundance and frequency.2) At small spatial scales, low environmental and genetic variability within plots led to low intraspecific a diversity. While high environmental and genetic variability between plots led to high intraspecific (3 diversity. At large spatial scales, high environmental and genetic variability within plots, while low environmental and genetic variability between plots, led to high intraspecific α diversity but low intraspecific β diversity.3) Low environmental and genetic variability at small spatial scales caused low intraspecific trait variability. Widening the study scale tends to increase the environmental and genetic variability that is included, so the extent of ITV continues to increase with increasing spatial scale until the entire environment is included since studies at broader scales include contrasting biomes and thus the whole potential ITV. As expected, the habitat filtering hypothesis provided a better fit to the observed IVI-spatial scale relationship. And for the mean leaf area(MLA) and leaf dry matter content(LDMC), the dispersal limitation have the same approximation compared with those made by the habitat filtering hypothesis.In conclusion, by analyzing the extent, source and spatial structure of ITV, the results showed that the intraspecific trait variability was not negligible, and with the increasing of spatial scales the intraspecific a diversity tends to increase while the intraspecific β diversity tends to decrease. What’s more, the ITV continues to increase with increasing spatial scale until the entire environment is included. And the spatial structure of ITV was affected by both neutral process and niche process.