Effects Of Nitrogen And Silicon Addition On Soil Physicochemical Properties And Aboveground Productivity Of Native And Degraded Meadows

Silicon(Si)is one of the important trace elements that make up the plant body.The addition of exogenous silicon will affect the soil nutrients and thus have a positive effect on the community structure.Most of the previous studies focused on the effects of nitrogen fertilizer and silicon fertilizer application on the soil,community structure and function of native meadow,but there were few comparative studies on the soil physicochemical and the response of different plant functional groups to nitrogen addition of native meadow and degraded meadow.In this study,the alpine meadow of Qinghai-Tibet Plateau was taken as the research object,and the effects of the addition of N and Si(Si8,Si12)alone and the mixed addition of N and Si(N7Si8,N7Si12,N14Si8,N14Si12)on soil physicochemical properties and plant community productivity of the native meadow and degraded meadow were studied.The main findings were as follows:1.Both the addition of Si and the mixed addition of N and Si significantly reduced the soil p H values of the native and degraded meadows,in which the mixed addition of N and Si had a greater effect on the soil p H values of the two kinds of meadows than the single addition of Si,and the reduced range of soil p H values of the degraded meadow was larger than that of the native meadow.The contents of soil organic carbon,total nitrogen,available phosphorus,ammonium nitrogen,soil total phosphorus and nitrate nitrogen were increased by N and Si mixed addition.Compared with the control group,the contents of soil organic carbon,total nitrogen,available phosphorus,ammonium nitrogen,total phosphorus and nitrate nitrogen increased by 14.35%,39.56%,22.74%,136.09%,18.52% and 70.69%,respectively,under N14Si12 treatment.The contents of soil organic carbon,soil total phosphorus and available phosphorus increased by 10.33%,11.10% and 31.30% under Si12 treatment compared with the control group,respectively.The contents of total nitrogen,ammonium nitrogen,nitrate nitrogen,soil organic carbon and available phosphorus in the degraded meadow were increased by 26.26%,194.37%,115.63%,6.84% and 22.80% under the treatment of N14Si12 compared with the control group,respectively.The content of available P and organic carbon in degraded meadow soil increased by 31.33% and 13.55% under Si12 treatment compared with control group,but had no significant effect on soil total P.2.The addition of Si alone and the mixed addition of N and Si significantly promoted the biomass of gramineous functional groups in both native and degraded meadows,and the increase amount under the mixed treatment of N and Si was higher than that under the single addition of Si.Combined addition of N and Si significantly increased the abundance and plant height of the two kinds of meadow grasses,and the increase of the abundance of the degraded meadow grasses was greater.Single addition of Si had a significant effect on the plant height of the native meadow grasses,but had no significant effect on the plant height of the degraded meadow grasses.3.The addition of Si alone and the mixed addition of N and Si significantly promoted the biomass of sedge functional groups in both native and degraded meadows,and the increase of the mixed addition of N and Si was higher than that of Si alone.The addition of Si alone and N and Si combined also had significant effects on the abundance and plant height of sedge family in the native and degraded meadows,and the increase of the abundance of sedge family in the degraded meadow was larger.4.Si supplementation alone significantly increased the abundance and plant height of grass functional groups in the native and degraded meadows,and significantly increased the biomass of grass functional groups in the degraded meadow,but decreased the biomass of grass functional groups in the native meadow;The mixed addition of N and Si significantly decreased the biomass,abundance and plant height of functional groups of grass in the native meadow,but significantly increased the biomass,abundance and plant height of functional groups of grass in the degraded meadow.In conclusion,N and Si fertilization can increase soil nutrient content in native and degraded meadows,but the effects on different meadows are different,and the change of soil nutrient content in degraded meadows is more responsive to the addition of N and Si.At the same time,the above ground biomass,plant height and abundance of grasses,seperaceae and miscellaneous grasses in native and degraded meadows were significantly increased by Si addition and N and Si combined addition,but the above ground biomass of grasses and seperaceae was not significantly different between the two species.This study enriched the research on the effects of nitrogen and silicon addition on the alpine meadow,and provides a new theoretical basis for the restoration and management of degraded alpine meadow on the Qinghai-Tibet Plateau.