The Effect of Soil Physical Structure on Soil Carbon and Nitrogen Sequestration Across Land Use Types

Abstract

Land use change driven by human activities is the most prevalent and direct way to alter soil quality and function, thereby affecting soil carbon and nitrogen sequestration. Nevertheless, the impact of soil physical structure on soil carbon and nitrogen sequestration across various land use types within the same area remains unclear. This research collected soil samples from five land use types: natural forests, artificial forests, shrublands, meadows, and farmlands. We investigated the soil's physical structure, soil carbon and nitrogen pools within aggregates, and their driving factors under the five land use types. Our results showed that the soil organic carbon (SOC) and total nitrogen (TN) in both natural and artificial forests were mainly stored in macroaggregates, while SOC and TN in shrublands, farmlands, and meadows were primarily stored in microaggregates. Meanwhile, they were stored primarily in microaggregates in shrublands, meadows, and farmlands. However, the soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were mainly stored in medium-sized aggregates. Moreover, the SOC of soil macroaggregates in natural forests, artificial forests, shrublands, and meadows was 16.4%, 23.7%, 8.6%, and 40.7% higher than in farmland. Comparatively, the MBC of soil macroaggregates in natural forests, artificial forests, shrublands, and meadows was 48.9%, 26.4%, 37.0%, and 18.8% higher than it in farmland. Through analysis, we have found that the soil C and N sequestration were closely related to the physical structure, and soil enzyme activity had a substantial impact on the accumulation of soil microbial biomass. Our results indicate that the changes of soil C and N under different land use types were mainly driven by the content of C and N in macroaggregates. These results highlight the importance of soil physical structure in soil C and N sequestration, providing insights into sustainable land use management practices.

Keywords: Soil physical structure, Soil aggregates, Soil carbon and nitrogen sequestration, Soil microbial biomass, Land use types