Synergies and trade-offs in P acquisition strategies underlying tropical dipterocarp forests in Southeast Asia

M. Y. LEE, Q. Y. HO, W. T. A. GOH, D. YAM, K. M. ANDERSEN

Asian School of the Environment, Nanyang Technological University, 59 Nanyang Dr, (S)636921, Singapore

Phosphorus limitation is pervasive throughout many pantropical forest communities. However, P acquisition strategies have rarely been examined in Southeast Asian dipterocarp-dominated forests, constraining our understanding of how pantropical species adapt to P limitation. Our study seeks to uncover trade-offs between P acquisition strategies across evolutionarily diverse tropical forest species and how root traits contribute towards inorganic and organic P uptake in nutrient-limited soils. We examined the root morphology, architecture, phosphomonoesterase activity, nutrient content and mycorrhizal colonisation intensity of 33 species in Bukit Timah Nature Reserve and found three main dimensions of trait variation. These dimensions capture multiple aspects of plant P acquisition strategies, including fungal collaboration with mycorrhizal, resource conservatism and variations in phosphatase activity to access organic P. Unexpectedly, arbuscular mycorrhizal colonisation was uncorrelated with the fungal collaboration gradient but correlated negatively with root tissue density on the resource conservatism gradient. Dipterocarps were rarely colonised by ectomycorrhizal but exhibited significantly greater phosphomonoesterase activity. Ultimately, our study expands the known diversity of trait combinations species utilise for P uptake in nutrient-limited environments, while providing evidence that trait ordinations observed from temperate and neotropical ecosystems may not be generalisable to Southeast Asian dipterocarp-dominated forests, mainly due to differences in mycorrhizal associations.