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Seasonal Changes of Soil Nitrogen Mineralization Along Restoration Gradient of Sandy Grassland, Northern China

Lv Peng, Zuo Xiaoan, Sun Shanshan, Zhang Jing, Zhao Shenglong, Hu Ya

Polish Journal of Ecology

2020

Vol. 68, nr 4

283--295

Soil nitrogen mineralization strongly affects N availability, thus impacting the primary productivity in ecosystems. The seasonal environmental changes affect soil mineralization in restored sandy grasslands such as a studied mobile dune (MD), a semi-fixed dune (SFD), a fixed dune (FD) and a grassland (G). During the growing season, we examined the association of soil N mineralization rate with vegetation characteristics, soil properties and climatic factors through the multivariate stepwise regression model. The vegetation cover, species diversity, above- and belowground biomass, soil carbon, nitrogen, soil water content (SWC), pH, electrical conductivity, very fine sand, clay and silt fractions increased during sandy grassland restoration. The NH4+-N concentration in MD and SFD was higher than that in FD and G, while NO3--N and inorganic N concentration showed a reverse trend. The NH4+N, NO3--N and inorganic N concentrations in MD, SFD and FD reached to the highest values in June, while in G they were highest in May. The net mineralization and nitrification rates increased with sandy grassland restoration; both of these rates were much greater in June than in other months at all sites. Regression analysis showed that the NO3--N concentration, SWC, pH of the soil and precipitation could explain 75% of the total variation in net nitrification rate, and the NO3--N concentration and precipitation could explain 59% of the total variation in the net mineralization rate. These results illustrate that the sandy grassland restoration can enhance the soil N availability, with soil N mineralization mainly determined by the changes of the NO3--N concentration and precipitation.