Nutrient acquisition strategies and fine root dynamics determine differences in soil carbon between contrast tropical forest types

N.C. RACZKA, V. SRINIVASAN, C. COLLINS, J.C. QUEZADA, R.S. SUKRI, A.R. COBB, E.M. SLADE, D.A. WARDLE, & K.M. ANDERSEN

Asian School of the Environment, College of Science, Nanyang Technological University, 59 Nanyang Drive, Singapore 639798

Southeast Asian tropical forests consist of highly distinct habitats, holding significant biodiversity and carbon stores.  Heath forests and peat swamp forests are two unique forest types that have a paucity of data on the belowground processes, such as how trees acquire nutrients that control soil carbon cycling.  Differences belowground can affect how much carbon is stored or lost to the atmosphere, thus to better understand carbon dynamics we sampled the soil to a depth of two meters in nine paired plots in both heath and peat swamp forests in Brunei.  We hypothesised that heath forests would contain greater fine roots with depth and have these roots colonized by arbuscular mycorrhizae.  In contrast, peat swamp forests would contain greater fine roots at the surface with ectomycorrhizal colonization and greater root necromass.  We found that heath forests store similar carbon in fine roots while peat swamp forests store more carbon in dead roots that resist decomposition in waterlogged conditions.  Additionally, we found differences between arbuscular mycorrhizal colonization rates in the heath forests and ectomycorrhizal colonization in the peat swamp forest.  These differences are important in tree nutrient acquisition strategies and implications for how these forests will store carbon belowground with climate change.