Plant productivity and belowground resource partitioning in gradients of tropical land-use intensity and tree species diversity

Tropical Rain forest conversion is associated with severe losses in species and functional diversity. Oil palm and rubber monocultures are more susceptible to water deficits due to more cavitation sensitive xylem as species loss has reduced functional diversity Hence our main study area will be biodiversity enrichment experiment site. We aim to focus on linking belowground and aboveground functional trait diversity and assess the importance of functional diversity for buffering plant productivity against stress. To investigate we use the ingrowth core approach with additional installation of 100 mini-rhizotrons to determine root birth, death and turnover rates and compare results to the outcomes of the ingrowth core study. We will also investigate spatial resource partitioning in the plantation to understand the resource uptake and potential asymmetry of root competition between palms and dicot trees using stable isotope technique. Regarding root water uptake we plan to study the root competition intensity and the degree of asymmetry between oil palms and studied dicot trees. The method includes sap flux techniques using miniature sap flow gauges on exposed roots of competing oil palms and different dicot tree species in moist and drier periods. The study may thus lead to a better understanding of below-ground functioning and resource acquisition.