首页|Effects of vegetation presence on soil net N mineralization are independent of landscape position and vegetation type in an eroding watershed
Effects of vegetation presence on soil net N mineralization are independent of landscape position and vegetation type in an eroding watershed
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NSTL
Elsevier
Soil erosion can dramatically alter soil nitrogen (N) cycling, but it has rarely been examined under in-situ conditions due to the complicated interaction between erosion and vegetation. Comparing the effects of vegetation presence at eroding and depositional sites would provide a direct understanding of such effects. Herein, we investigated how soil N dynamics (mineral N pools and net N mineralization rates) responded to vegetation presence (plot with vs. without vegetation), landscape position (eroding vs. depositional sites) and vegetation type (grassland vs. woodland) during a two-year manipulation experiment using an in-situ incubation method in the hilly-gully region of China's Loess Plateau. The results showed that soils on eroding site had higher concentrations of nitrate (3.820 +/- 0.302 vs. 2.642 +/- 0.280 mg kg-1) and mineral N (5.853 +/- 0.320 vs. 4.308 +/- 0.287 mg kg-1) but similar rates of net nitrification (0.057 +/- 0.013 vs. 0.051 +/- 0.011 mg kg-1 d-1) and mineralization (0.056 +/- 0.014 vs. 0.056 +/- 0.013 mg kg-1 d-1) in comparison to depositional site in all grassland plots. The concentrations of soil nitrate and mineral N and rates of net nitrification and mineralization in legume woodland were 26%, 19%, 88% and 64% higher than that in grassland in all slope plots, respectively. Although vegetation presence significantly decreased soil nitrate (-57%) and total mineral N (-27%) concentrations, it did not affect the rates of net nitrification and mineralization. The effects of vegetation presence on soil net N mineralization occurred irrespective of landscape position and vegetation type(P > 0.05), but varied with season or year, with greater effects in 2017 growing season than in the non-growing season and 2018 growing season. Redundancy analysis and hierarchical partitioning indicated that the above- and blow-ground biomass accounted for most of the variation in soil N mineralization. These results suggested that the variations in soil mineral N and net N mineralization in relation to vegetation presence in this eroding watershed were consistent across different landscape positions and vegetation types, but showed intra- and inter-annual variability.
NSTL
Elsevier
