Responses of soil greenhouse gases emission to forest degradation: A global synthesis

Forest degradation is a worldwide serious problem associated with human disturbance and climate change. Land use change from natural forest to plantation, grassland or agricultural land may lead to profound alteration in the emission of soil greenhouse gases (GHG). Here, we presented a global synthesis of forest degradation effects on soil GHG and explored the potential mechanisms. Based on 242 cases from 87 studies in the world, we found forest degradation decreased soil CO₂ emission and increased soil CH₄ efflux across all degradation types, but had no significant impact on soil N₂O emission. Similar responses of soil GHG were found in temperate and tropical regions, except that N₂O showed significant positive response to forest degradation in temperate region but no response in tropical region. Forest degradation effects on soil GHG varied among land use change types. Moreover, changes of soil MBC, root biomass and litterfall had positive effects on the response of soil CO₂ emission to forest degradation across all climatic regions globally, whereas the drivers differed among forest degradation types. Change of soil NO₃^- was consistently the key driver for the response of soil N₂O emission. The response of soil CH₄ was significantly correlated to changes in soil pH and available nitrogen, depending on the spatial scale and degradation type. Our findings enhance the knowledge of the potential mechanisms for the responses of soil CO₂, N₂O and CH₄ emission to forest degradation and improve the assessment of the impacts of land use change on soil GHG emission

Keywords: Forest degradation; Land use change; GHG; Soil CO₂; Soil N₂O; Soil CH₄