Response Of Litter Decomposition To Different Restoration Measures In Horqin Saline-alkali Grassland

Horqin grassland is a typical agro-pastoral ecotone in northern China,which has an area about 5.17×10~4km~2.In recent years,its stability has been destroyed due to climate change and people’s unreasonable use of grassland.Litter,as an important carrier that connects plants and soil in the grassland ecosystem,cannot be ignored in grassland restoration and utilization.For this reason,in this experiment,two restoration measures was adopted in the salinized grassland in Jarud Banner,Tongliao City,Inner Mongolia from October 2019 to September 2020,i.e.sanded+supplementary sowing and organic fertilizer+supplementary sowing.Decomposition experiments of 3 single species of litter and 4 types of mixed litter were carried out,and the response of the decomposition characteristics of litter to different restoration measures was compared.The main research conclusions are as follows:(1)During the one-year decomposition period,the decomposition rule of litter was first slow and then become fast.The mass residue rate of single species of litter is in the order of Leymus chinensis>Agropyron cristatum>Melilotus suaveolens;while among the mixed litter,Leymus chinensis-Agropyron cristatum has the highest residual rate.The mass residue rate of Agropyron cristatum-Melilotus suaveolens in Moderate degenerate sanded restoration measures and heavy degenerate organic fertilizer restoration measures were significantly lower than the litter of the other three groups of Leymus chinensis-Agropyron cristatum,Leymus chinensis-Melilotus suaveolens and Leymus chinensis-Agropyron cristatum-Melilotus suaveolens(P<0.05).(2)Soil water content is the main factor affecting the decomposition of litter.The decomposition rate in heavy saline-alkaliized grassland is higher than that in moderate saline-alkaliized grassland.Degradation gradient,restoration measures and litter types all affect the decomposition rate.There were significant differences in the decomposition of litter of different species under the same restoration measures,as well as the decomposition of the same type of litters under different restoration measures(P<0.05).Moreover,there was an interaction among the three factors.(3)The residual rate of litter was positively correlated with the contents of total carbon and potassium,and negatively correlated with cellulose and lignin(P<0.05);There was a negative correlation between the total nitrogen content and the mass residual rate of Leymus chinensis-Agropyron cristatum and Leymus chinensis-Melilotus suaveolen,while the single and mixed decomposition of Agropyron cristatum and Melilotus Melilotus were positive correlation with total nitrogen content.(4)The mixing effect of litter decomposition mainly depends on the litter species.The carbon residual rate of mixed litters was additive effect;nitrogen was antagonistic effect,and potassium was synergistic effect.Cellulose showed antagonistic effect in moderately salinized grassland and synergistic effect in heavy salinized grassland.The antagonistic effect of lignin was only observed when the three litters were mixed.