A04 - Stock, turnover and functions of carbon in heavily weathered soils under lowland rainforest transformation systems

Strong decrease of organic carbon (C) stocks and degradation of soil properties after transformation of lowland rainforest to plantations was shown in the 1st phase. Based on δ 13C along soil depth, two processes decreasing C stocks were distinguished: erosion and mineralization of soil organic matter (SOM). Both processes and low litter input under plantations lead to high stability of the remaining C and consequently to its low functionality for providing C sources and energy for microorganisms and maintaining soil fertility and ecosystem stability. However, C availability was higher in rubber than in the oil palm plantation despite similar C losses and erosion. In the 2nd phase the project will reveal these main processes of C stock decrease on new sites including a broader ecological context and various management practices. Further, the project will especially focus on the differences of stability of remaining soil C between intensive plantations by new approaches including FTIR, MIR and VISNIR measurements and incubations, C fractionation, isotopic composition, Rock-Eval pyrolysis, and 3D fluorescence. Because we expect that the most changes are ongoing in very short periods after the rainforest transformation - the hot moments, we will focus on the processes over these short periods:
after removal of rainforest or old oil palm plantations as well as after strong monsoon rains.
The project will strongly contribute to the overall goals of the planned CRC by providing data on stocks, forms and processes of C transformation after forest conversion to plantation by focusing on the stability of C and its availability for soil microorganisms. The project is closely integrated into other projects of groups A, B and C investigating changes in the belowground system with focus on soil fertility, productivity, ecosystem stability and modelling perspectives. Further, the study is integrated into other projects of groups B and C investigating the effects of decreasing soil fertility on biodiversity, economic and social responses.