Impact of rubber-based land use changes on soil properties and carbon pools: A meta-analysis

The rapid expansion of rubber plantations may have greatly influenced the carbon stocks of the ecosystem, with potential impacts on mitigating climate change and future carbon fluxes. Therefore, soil carbon pools and other properties must be reliably estimated after rubber-based land cover transitions. The aim of this meta-analysis is to understand how various land use changes based on rubber plantations affect soil physicochemical properties, especially soil organic carbon (SOC) pools. This study focuses on three land use changes: (1) forest-to-rubber conversion; (2) rubber monoculture vs. intercropping; and (3) the age and altitude of the rubber stand over a chronosequence in rubber plots. Results showed that the conversion of forest to rubber plantation significantly reduced the SOC, microbial carbon (MBC), total nitrogen (TN) and total magnesium pools by 24%, 35%, 13% and 94% respectively, whereas rubber intercropping with different crops profoundly increased the SOC and MBC pools by 6% and 24% on average, respectively. The improvement of rubber intercropping on SOC and properties mainly occurred in the surface soil at 0-20 cm and at altitudes of 500-800 m, but these effects were diminished in the subsurface soil at 20-60 cm and at altitudes higher than 800 m. Rubber intercropping plantations can significantly alleviate soil acidification. Changes in the response ratio of SOC were closely related to the variations in soil clay, bulk density, and C/N ratio. These results suggest that rubber-based land use management policies should promote intercropping plantations, especially those with woody plants, and the altitude of rubber planting should be manipulated to minimize the loss of soil C, N, and other nutrients.