Effects of Vegetation Restoration Type on Soil Greenhouse Gas Emissions and Associated Microbial Regulation on the Loess Plateau

Investigating responses of soil greenhouse gas (GHG) emissions to vegetation restoration is important for global warming mitigation. On the Loess Plateau, a wide range of vegetation restoration strategies have been implemented to control land degradation. However, the thorough quantification of soil GHG emissions triggered by different modes of vegetation restoration is insufficient. There is still a knowledge gap regarding the regulation of soil biochemical and microbial processing on soil GHG emissions. To do so, we compared responses of soil GHG emissions to various types of vegetation restoration on the Loess Plateau, and investigated the changes in soil properties as well as microbial composition and activities. We found that artificial plantation of Caragana korshinskii had low soil carbon dioxide (CO₂) emission, while natural grassland had high CO₂ emission. The possible explanations could be related to higher moisture and microbial biomass carbon, and greater nitrogen limitation in natural grassland, which was controlled by actinomycetes and gram-negative bacteria. Natural grassland had low soil nitrous oxide (N₂O) emission and high methane (CH₄) uptake, whereas Prunus mume had high N₂O emission and Medicago sativa had low CH₄ uptake, respectively. Soil N₂O emission could be driven by fungi and gram-positive bacteria which were affected by N availability and dissolved organic carbon. Soil CH₄ consumption was associated with anaerobic bacteria and gram-negative bacteria which were affected by N availability and moisture. These different emissions of CO₂, N₂O and CH₄ generated the largest total GHG emissions for plantation of Prunus mume, but the smallest total GHG emissions for natural grassland and plantation of leguminous Caragana korshinskii. Overall, our findings suggested that the restoration of natural grassland and artificial N-fixing shrubland like Caragana korshinskii should be encouraged to alleviate GHG emissions, with the practical implications for selecting suitable modes and species to improve ecological sustainability in degraded lands.