EFFECTS OF CARBON SUBSTRATE LABILITY ON TROPICAL PEAT MINERALIZATION UNDER AEROBIC AND ANAEROBIC CONDITIONS

摘要

Extensive draining at tropical ombrotrophic peatlands in Southeast Asia has made them global 'hot spots' for greenhouse gas emissions. Here, we present the first data on how management practises affect carbon (C) mineralization processes at these soils. We compared the peat carbon mineralization potentials of pristine forest to those of drained fire affected soils, with and without additional labile substrates (glucose, glutamate and NO3- N) and in oxic and anoxic conditions by dedicated ex situ experiments. Carbon mineralization (CO2 and CH4 production) rates were higher in the forest peat, which contains more labile C due to higher input via vegetation. Production rates decreased with depth in peat profile together with decreasing availability of labile carbon. Consequently, the increase in C mineralization rates after labile substrate addition was relatively modest from forest site as compared to the reclaimed site and from the top layers as compared to deeper layers. Methanogenesis had little importance in total carbon mineralization. Surprisingly, oxygen availability was not an ultimate requirement for substantial CO2 production rates. Flooding of these sites will therefore reduce, but not completely cease, peat carbon loss. Reintroduced substantial vegetation and fertilization in degraded peatlands can enrich recalcitrant peat with simple C and N compounds and thus increase microbiological activity. This outcome reinforces the importance of decomposition-resistant litter types and sufficient litter allocation in the maintenance of ombrotrophic tropical peat carbon store regardless of the land management type.