Species mixing improves soil properties and enzymatic activities in Chinese fir plantations: A meta-analysis

It is becoming a tendency for multispecies plantations to be promoted worldwide to enhance carbon seques-tration and provide better ecosystem services. Soil physicochemical properties and enzymatic activities are critical for tree growth and biogeochemical processes. However, the effects of species mixing on soil properties and enzymatic activities in monoculture plantation forests remain unclear. We conducted a meta-analysis to quantify the effects of species mixing on soil physicochemical properties and enzymatic activities in Chinese fir plantations. We collected 4,620 paired observations from 120 studies. We found that soil physicochemical properties and enzymatic activities increased by 13.97% and 36.34% in species mixing plantations compared to monoculture plantations. Species mixing enhanced soil aeration, water holding capacity, and the total amount and availability of nutrients, increased the soil organic carbon stocks and improved soil nutrient cycling in plantations. The effects of species mixing on soil physicochemical properties and enzymatic activities were negatively correlated with slope, mean annual temperature, and mean annual precipitation but positively correlated with the number of tree species and the proportion of mixed species. In summary, our meta-analysis highlights the positive effects of species mixing on soil nutrient cycling and ecosystem function in Chinese fir plantations and recommends species mixing rather than monoculture plantations for afforestation to support the sustainable and healthy development of forests.