Soil organic matter stabilization and carbon-cycling enzyme activity are affected by land management

Abstract

Increasing carbon (C) storage in soil is a key aspect of climate change mitigation strategies and requires an understanding of the impacts of land management on soil C cycling. The primary aim of this study is to investigate how land management impacts key soil organic matter stabilization and cycling processes affecting soil C storage. Soil sampling was undertaken across seven transects crossing the boundary between agriculture and forestry. The transects covered 3 pasture (AP) and 4 arable (AA) fields combined with 3 young secondary woodlands (50-60 years old - WY) and 4 mature/ancient semi-natural woodlands (110 to >400 years old – WM). Physical fractionation of soil organic matter pools was performed, together with pH, carbon and nitrogen content, as well as activity of four enzymes associated with C transformation in the soil. Woodland soils were associated with significantly higher content of light fraction C and greater enzyme activity in comparison to agricultural soils. Enzyme activity and soil organic C decreased with soil depth regardless of land-use type. We did not, however, observe any effect of the distance from the land use boundary on either enzyme activity and soil C pools. Our results indicate that analysis of soil organic matter (SOM) fractions can act as an indicator of decomposition rates of SOM in forest and agricultural ecosystems.