围封和施肥对高寒草甸群落特征和植被碳氮库的影响OA北大核心CSTPCD

The objective of this study was to determine how two different restoration measures,i.e.,grazing exclusion and fertilization,affect degraded alpine meadows.A field study was conducted to compare the effects of grazing exclusion for various periods(0,4,13 yrs)and long-term fertilization(with nitrogen,N,and phosphorus,P)on community characteristics and vegetation carbon(C)and N pools.The results showed that:1)The species richness index and Shannon-Wiener index decreased significantly with increasing years of grazing exclusion,while Simpson's index and the Pielou index increased and then decreased.The addition of N and P fertilizers significantly decreased the species richness index and Shannon-Wiener index.2)Aboveground biomass and root biomass were significantly increased after both 4 and 13 years of grazing exclusion,reaching the maximum at 4 years,whereas litter biomass increased gradually with increasing years of grazing exclusion.The effect of long-term fertilization on biomass was not significant.3)After grazing exclusion,vegetation C and N stocks increased significantly,with aboveground biomass and root C and N pools being highest at 4 years of grazing exclusion,and litter C and N pools being highest at 13 years of grazing exclusion.Long-term fertilization had no significant effect on vegetation C stocks,and only long-term N addition significantly increased the aboveground biomass N pools.4)Partial least squares path modeling showed that grazing exclusion and fertilization led to changes in environmental factors that restrained community diversity and promoted the accumulation of plant biomass and vegetation C pools,while fertilization affected vegetation N pools.In summary,grazing exclusion generally restrained species diversity,but promoted community productivity and increased vegetation C and N pools,while long-term N addition had no significant positive effect on species diversity and vegetation C pools,but increased vegetation N pools.