Aims Vegetation-soil nutrient interation is a key process in maintaining stability and multifunctionality of terrestrial ecosystems. However, vegetation-soil interaction on carbon (C), nitrogen (N) and phosphorus (P) and the key drivers in promoting plant succession during sandy land restoration are still unclear. In this study, based on ecological stoichiometry theory, the vegetation-soil nutrient interaction in sandy land from the perspective of soil microorganisms was explored, and the limiting factors for ecological restoration of degraded vegetation in sandy land were also investigated.
Methods We selected different landscape types in Hulun Buir Sandy Land, including mobile dunes, semi-mobile dunes, semi-fixed dunes, fixed dunes, and sandy grassland. The space-for-time substitution approach was used to investigate the characteristics of the C, N, and P stochastic geometries of the vegetation-soil coordination equilibrium and the key drivers in the restoration processes. In addition, a correlation analysis between vegetation-soil stoichiometry and soil microbial communities was performed to reveal multiple driving mechanisms of soil physicochemical factors, plant communities, and soil microbial communities on plant-soil stoichiometry during plant restoration in degraded sandy areas.
Important findings 1) With vegetation restoration in degraded sandy land, soil C, N, and P contents, as well as the ratio of C:P and N:P showed significant increasing trends. Conversely, C, N, and P contents and their stoichiometry in living plants and roots did not show clear trends. These results suggest that sandy plant communities are still capable of maintaining their nutrient balance, and that their stoichiometric balance is relatively stable with environmental conditions recover and change. 2) Soil C:P (12.08-38.40) was at a low level, resulting in net soil P mineralization, and microbial decomposition of organic matter was not limited by P, and above-ground plant N:P was all lower than 10, indicating that the growth of vegetation in Hulun Buir Sandy Land was mainly limited by N. 3) Meanwhile, the soil N:P continued to increase, indicating that the supply of soil N gradually increased, while the supply of P gradually decreased, and P could be a limiting element in the later stages of vegetation restoration. 4) During vegetation restoration in the Hulun Buir Sandy Land, soil stoichiometry and pH had direct significant positive effects on plant stoichiometry, while soil microorganisms indirectly affected plant stoichiometry by regulating soil stoichiometry. In addition, the indirect effects of soil moisture, soil texture, and electrical conductivity on soil and plant stoichiometry should not be neglected. Thus, this study provides a theoretical basis for adaptive management and prediction of ecosystem restoration in degraded sandy soils.