The fate of natural areas remains uncertain due to ongoing fragmentation of landscapes as anthropogenic activities intensify. The novel conditions created by landscape fragmentation may act as filters selecting for individuals with a suite of traits that enable them to survive and grow in remaining fragments. However, efforts to generalize the magnitude and drivers of the loss of functional diversity of fragmented communities are hampered by the multiple and interacting scales at which landscape fragmentation takes place.
Multi-scale approaches have been suggested as more appropriate than simple regression models to understand species responses to landscape fragmentation. But to date, no such hierarchical modeling approach has been applied to fragmented communities, thus the impact of landscape fragmentation on trait distributions at different spatial scales remains a fairly unexplored area. Here we provide a multi-scale hierarchical approach linking processes at the fragment and landscape scales and their effects on functional diversity in a fragmented forest located in the East Usambara Mountains of Tanzania.
Results/Conclusions
Our results suggest that novel abiotic conditions that characterize newly formed edges shift the competitive hierarchies among tree species, favouring species with fast growth. Furthermore, there is a reduction in alpha functional richness that may be driven in part by the low functional richness for wood density occurring in the small fragments. Moreover, while results at the plot scale suggest a trend for higher functional evenness of wood density occurring at the edges of remnant forest fragments, at the fragment scale we find evidence of reduced evenness in wood density. Thus, depending on the observed spatial scale, we reach different results and conclusions demonstrating the importance of developing a mechanistic understanding of landscape fragmentation using a multi-scale approach.
In summary, our results demonstrate the utility of a multi-scale approach to investigate the effects of landscape fragmentation on functional diversity. We anticipate that the proposed approach will guide investigations on the impacts of landscape fragmentation on functional diversity and facilitate comparable quantitative analyses across fragmented landscapes.