Seasonal differences in soil respiration and methane uptake in rubber plantation and rainforest uri icon

abstract

  • Rubber plantations expanded remarkably in South-East Asia, while the impact of this land use change on soil carbon dynamics and greenhouse gases emissions has not been sufficiently understood. We measured monthly soil CO2 fluxes during one year as well as CH4 fluxes during the rainy season in secondary rainforest, 9 and 22 year-old rubber monoculture and 22-year-old rubber-tea intercropping in Xishuangbanna, Southwest China. Our aim was to assess the impact of the land use change on soil carbon fluxes and quantify the factors determining the difference in the carbon fluxes. A linear mixed effect model was used in studying the soil temperature and moisture variation and temperature sensitivity (Q10) of soil respiration. The temporal pattern of soil respiration distinctly differed between sites during the rainy season: rainforest maintained a high soil respiration rate, while soil respiration became suppressed (by up to 69%) during the most moist period in rubber plantations. Rainforest soils thus emitted the highest amount of CO2 with an annual cumulative flux of 8.48 أ 0.71 Mg C haâ??1 yrâ??1, compared to 6.75 أ 0.79, 5.98 أ 0.42 and 5.09 أ 0.47 Mg C haâ??1 yrâ??1 for mature rubber, rubber-tea intercropping, and young rubber, respectively. Additionally, the soil CH4 uptake was stronger in rainforest than in rubber plantations during the wet period. Soil temperature was the main factor explaining the overall seasonal variation of soil respiration. Adding a quadratic soil moisture term into the model accounted for moisture effects, identified moisture tipping points, and improved temperature sensitivity assessment when high soil moisture suppressed soil respiration under rubber. Temperature sensitivity of soil respiration was higher for rainforest soil compared to rubber plantations, Q10 values were 3.1 for rainforest and 1.7, 2.2 and 2.4 for mature rubber, rubber-tea intercropping and young rubber respectively. Converting rainforest to rubber plantations tended to reduce soil CO2 emissions and weakened CH4 uptake especially during the very wet period. The altered condition of soil aeration under converted land appears to have a pronounced impact on processes of carbon fluxes from the soil and thus mitigates the positive feedback of climate change given the large area of cultivated rubber. © 2017 Elsevier B.V

publication date

  • 2017
  • 2017