Effects Of Vegetation Restoration Of Sandy Land On The Characteristics Of Soil Carbon,Nitrogen,Phosphorus And Its Ecological Stoichiometry In Zoige Plateau

The Zoige Plateau is located on the eastern margin of the Qinghai-Tibet Plateau,China,an essential national region of water conservation and biodiversity conversation.Human activities,climate change,and biological factors have deteriorated grassland degradation and desertification in this region.Several projects have been implemented to prevent desertification,especially in ecological recovery programs.Therefore,evaluating the effectiveness of ecological restoration projects,optimizing restoration measures of alpine sandy land,and promoting the healthy sustainable development of alpine grassland were critical scientific questions to be solved in this area.In this study,we investigated the characteristics of aboveground plant communities,and determined soil properties in 0-100 cm soil profiles under different vegetation restoration measures in typical representative region.We tried to reveal the effect of different vegetation recovery types on plant communities,soil carbon,nitrogen and phosphorus contents,storage,and ecological stoichiometric characteristics,and their above and below interaction relation.The main results are as follows:1.Compared to severe desertified grassland,fencing enclosure,artificial reseeding and artificial planting Salix cupularis sandy land significantly restored herb coverage,biomass,Margalef richness index,Shannon-Weiner diversity index,Simpson dominance index,and Pielou evenness index(P < 0.05).Compared to natural grassland and shrubby grassland,there existed controversial results.2.The soil bulk density of all recovery types of sandy land in the Zoige Plateau had an increasing tendency with the deepening of 0-100 cm soil depth.This study’s high-low order of soil bulk density was severe desertified grassland > artificial planting of Salix cupularis,artificial reseeding,fencing enclosure > natural grassland.The artificial reseeding,fencing enclosure and artificial planting Salix cupularis had higher soil water than the severely degraded grassland in 0-10 cm soil layer.At the same time,the soil moisture content of natural shrubland,artificial reseeding,and natural grassland decreased gradually with the deepening of 0-100 cm soil profile.3.The contents of soil organic carbon,total nitrogen,and total phosphorus under all vegetation restoration types decreased with 0-100 cm soil depth in the Zoige Plateau.All vegetation restoration types of sandy land had lower soil organic carbon,total nitrogen,and total phosphorus than natural grassland.Compared with the severely degraded grassland,that had contrasting relusts.The storage of soil carbon,nitrogen,and phosphorus in the natural grassland was significantly higher than those vegetation restoration types in sandy land(P < 0.05).Soil carbon and nitrogen storage in fencing enclosure and artificial reseeding were markedly higher than in severe desertified grassland and artificially planting Salix cupularis sandy land.4.The transition between natural grassland and shrubby grassland significantly increased the soil carbon,nitrogen and phosphorus content and storage(P < 0.05).The shrubby grassland had a higher ratio of carbon to nitrogen,the ratio of carbon to phosphorus,and the ratio of nitrogen to phosphorus than that of natural grassland.This transition was beneficial to the accumulation of soil organic matter and the mitigation of nitrogen limitation,which improved soil nutrients and function.These provided a reference basis for artificial vegetation restoration of sandy land.The content and storage of soil carbon,nitrogen and phosphorus under artificial planting of Salix cupularis sandy land were significantly lower than natural grassland and severe desertified grassland(P < 0.05).The ratios of C: N,C: P,and N: P under artificial planting of Salix cupularis sandy land had a similar trend.Artificial planting shrubs would not be conducive to the accumulation of organic matter,promote the increase of phosphorus mineralization rate,and form severe nitrogen limitation.According to the above results,compared to severe desertified grassland,fencing enclosure,artificial reseeding,and artificial planting Salix cupularis promoted the recovery of aboveground plant communities,improved soil carbon,nitrogen,and phosphorus content and storage,and strengthened the regulation of ecological stoichiometry.However,the plant community and soil nutrients under all recovery types of sandy land did not reach the natural grassland initial status compared with natural grassland.We still need to strengthen the comprehensive research on the optimal of vegetation restoration models and the technological innovation of soil amendment.The grass-shrub transitions significantly increased the soil carbon,nitrogen and phosphorus content and storage,and improved the soil quality.Our study can provide scientific reference for the ecological restoration and protection of alpine sandy land.