Conservative agriculture facilitates soil carbon, nitrogen accumulation, and aggregate stabilization under periodic flooding regimes

Abstract Aggregates play crucial roles in protecting soil carbon (C) and nitrogen (N) loss since aggregates could mediate the effect of environmental factors on the C and N accumulation. As ecotone habitats, reservoir riparian zones undergo disturbances from both land use and dam-regulated flooding, which could pose threats to aggregate stability. Yet, we know little about the effects of the flooding intensity and land use on the dynamics of soil C and N, as well as the mediating role of soil aggregates. In this study, along a flooding gradient, firstly we examined the effects of seven land-use types (corn, rice paddy, and vegetable lands; Chinese fir, willow, and mulberry restored lands; and grassland) on soil C and N accumulation; secondly, we identified the size distribution and stability of aggregates in mediating the effect of riparian land uses under periodic flooding regimes. We found that the C and N concentrations in soil aggregate fractions were all significantly impacted by land-use types, and aggregate-size distribution showed tight links with both land-use types and C and N contents. Conservative farmlands contained a higher proportion of macro-aggregates which stores significantly higher C and N concentrations than micro-aggregates. Notably, higher aggregate stability was also found in conservative farmland. We concluded that, in the riparian ecotone, conservative farming promotes C and N accumulation via stabilizing aggregate fractions, and suggested the conservative practices could be acceptable for soil conservation considering the scarcity of land resources in the ambient mountainous regions.