Effects of Betula platyphylla invasion in North China on soil aggregate stability, soil organic carbon and active carbon composition of larch plantation

Aims In order to better understand the changes in the potential carbon sequestration capacity of forest soil after the invasion of broad-leaved trees into pure larch plantations, the effects of broadleaf tree invasion on soil aggregate stability and carbon sequestration by soil organic carbon and active carbon components were studied. Methods In northern China, the pure Larix principis-rupprechtii plantations and the Larix principis-rupprechtii plantations invaded by Betula platyphylla at various degrees with the same site conditions were selected (Betula platyphylla had a mixed degree of 0.2 and 0.4, respectively). ANOVA, correlation analysis, principal component analysis and structural equation were conducted to interpret the relations between Betula platyphylla invasion and soil properties. Results The distribution of soil macroaggregates (> 0.25 mm) increased with the increase in the mixed degree of Betula platyphylla. The mixture of Betula platyphylla could effectively increase the organic carbon and active carbon components of the original soil and soil aggregates of different diameter classes. The forest growth in this study area was mainly limited by nitrogen. The invasion of Betula platyphylla had an indirect impact on soil carbon sequestration by affecting the soil physical and chemical properties and the aggregate stability. Conclusions The invasion of Betula platyphylla had significant positive effects on soil aggregate stability, erosion resistance and soil nutrient status in Larix principis-rupprechtii plantation. The coniferous and broad-leaved mixture was a good strategy to increase the soil quality and soil organic carbon sequestration of the Larix principis-rupprechtii plantation in this area.