Drivers of floristic composition in Bukit Timah Nature Reserve: an investigation of leaf functional traits

Abstract

Forest fragmentation and associated edge effects can lead to considerable ecosystem degradation resulting in high mortality and loss of biodiversity. Bukit Timah Nature Reserve is a forest fragment that has been closely monitored for nearly 20 years. Though fragmentation is typically associated with negative consequences, Bukit Timah showed unexpected resilience to fragmentation effects. Interestingly, alterations in community structure were observed, though significant changes in stem density and basal area did not occur. The aim of this study was to explore the drivers of said compositional change, through examining four species of tropical rainforest trees. Two of these species are currently increasing in abundance (Shorea curtisii and Streblus elongatus) and two are decreasing in abundance (Gynotroches axillaris and Santiria apiculata). The study examined leaf mass per area, chlorophyll content, leaf thickness, and stomatal density. The results showed significant differences between species in trait values for all four functional traits, but no overarching trends to explain alteration in species composition were found. The results indicate that the four functional traits assessed are not critical in shaping community composition. Potential other drivers are explored, such as correlation with water transport systems. This is timely and important research in the face of dwindling primary forest in South-East Asia, and represents a global shift in priorities towards protecting ecological biodiversity.