Patterns of plant trait–environment relationships along a forest succession gradient in tropical dry forest Florida Keys

Background/Question/Methods

In most part of South Florida tropical dry forests, the early colonized trees on disturbed uplands are mostly deciduous species cable of surviving for several years after establishment. However, trees in mature forests are generally characterized by a suite of evergreen species, most of which are completely absent in younger stands even in seedling stage. This complete transition from one functional group to another in the course of stand development suggests a distinct change in the underlying environment during the course of succession. Such change in hammock functional groups as a function of the changing environmental drivers during succession in tropical dry forests is unknown and addressing this question may help to understand which drivers of change act as filters that select for and against particular groups of species and traits. In this study, we evaluate functional traits for forty woody species occurring along a successional gradient. The study was conducted in dry tropical forest in northern Key Largo in Florida Keys representing one of the extensive remaining examples of seasonal tropical dry forests in Florida. Ten 20 × 20 m²plot of various age, ranging widely in stand age (from 20 years to mature forests that have not experienced catastrophic disturbance for at least 100 years), were used for sampling. Species abundance (number of individuals greater than 1 cm dbh)and nine traits were measured for each stand. 

Results/Conclusions

A significant change in the overall trait distribution across the successional gradient was found. Most of the traits showed correlation with stand age and showed preference to a certain environment.  Younger stands are associated with high specific leaf area and low wood density. However, tree height and basal diameter are correlated with elevation. Stand age was the most important variable explaining the distribution of community characteristics. The patterns of trait shift may be predictable and can be used to characterize habitats and stage of forest succession. It is also found that early successional forest are mostly shaped by environmental driven processes, and as forest get older and structurally more complex, they are increasingly shaped by competitively driven processes leading to limiting similarity.