Soil greenhouse gas fluxes and C stocks as affected by phosphorus addition in a newly established Acacia mangium plantation in Indonesia

A 2-year-long monitoring experiment was conducted to determine the effects of phosphorus (P) addition on nitrous oxide (N2O) emission, methane (CH4) uptake and carbon (C) sequestration and decomposition in a newly established Acacia mangium plantation in South Sumatra, Indonesia. We established three large plots and prepared six control sub-plots and four sub-plots with P added in each large plot. Gas emissions were measured using a chamber method. We also measured selected physical and chemical parameters for soil, fresh leaves, litter layers, and the aboveground biomass of Acacia trees. Mean daily N2O flux was reduced (0.42 mg N m−2 day−1) by P addition. The reduction in N2O emissions resulting from P addition was likely to be due to the stimulation of root uptake of soil N and water, as suggested by the soil N and WFPS dynamics and correlations with N2O fluxes. P addition significantly increased (25.6 Mg ha−1 20 months−1) the Acacia biomass, contributing to an increase (46.9 Mg CO2-e ha−1) in C sequestration. P addition also stimulated soil C decomposition. Soil total C (TC) decreased significantly (0.14 kg C m−2) in the second year of P addition; CO2 emissions from soil were also stimulated (0.29 g C m−2 day−1) by P addition. P addition reduced (0.15 mg C m−2 day−1) CH4 uptake significantly, although the difference was small.