Land use effects on soil quality along a native wetland to cropland chronosequence

A large proportion of wetlands that once existed have been destroyed, and a factor usually neglected is how the duration of cultivation affects soil quality. This study aimed to reveal how land use change impacts soil quality in the temporal dimension through soil organic carbon, water-stable aggregates, and enzymes activities. Soil samples from a native wetland and five croplands which have been cultivated for 3, 8, 16, 22, and 24 years were collected. The results showed that the change patterns for the parameters measured were not straightforward along the temporal dimension, and the cultivated-time of 16 years can be regarded as the critical point of short-term and long-term impacts. Our results also implied that >1000 μm and <53 μm soil aggregate fractions were more sensitive to land use changes, and the total soil organic C losses in the croplands were mainly due to these two fractions. In addition, the geometric mean of the assayed enzyme activities (GMea) has been proven to be integrative enough to evaluate soil quality without analyzing physical and chemical properties. Therefore, we must pay attention to the detailed information of soil quality along the temporal dimension after the native wetland is converted to the cropland.

► Soil organic C concentrations significantly decreased after land use changes.
► The distribution and C storage of soil aggregate were affected by soil cultivation.
► Soil enzymes activities were significantly related to soil nutrients availability.
► Conversions from wetland to cropland have negative impacts on soil quality.