氮磷添加对藏东南高寒草甸植物群落及土壤理化性质的影响OA

In recent years,the intensification of global nitrogen deposition has induced a shift from traditional N limitation to phosphorus limitation in alpine meadows.However,whether phosphorus supplementation alleviates or exacerbates the negative effects of nitrogen deposition remains to be systematically elucidated.To clarify the regula-tory mechanisms of combined nitrogen and phosphorus addition on plant community and soil properties in alpine meadows,a five-year field control experiment was conducted in the alpine meadow of the Sejila Mountains in south-eastern Xizang starting in 2019.A total of nine combined nitrogen and phosphorus addition treatments with varying gradients[nitrogen:50,75 and 100 kg/(hm²·a);phosphorus:10,15 and 20 kg/(hm²·a)]were established,along with a control treatment(Natural condition).The results indicated that:Long-term combined nitrogen and phospho-rus addition significantly led to plant diversity decline and community structure differentiation(P<0.05),with the Shannon-Wiener index showing a maximum reduction of 21.32%under the high nitrogen and phosphorus treatment;The regulatory effect of phosphorus input on plant community characteristics exhibited a distinct nitrogen-level dependency.Under the low nitrogen treatment[50 kg/(hm²·a)],phosphorus addition effectively alleviated diversity loss with increasing phosphorus application;however,this mitigating effect was no longer significant under the high nitrogen background[100 kg/(hm²·a)];Nutrient inputs altered interspecific competition patterns,with the dominance of Cyperaceae species increasing with nutrient addition,while that of Asteraceae species significantly decreased(P<0.05);Long-term nitrogen and phosphorus addition significantly reduced soil pH(P<0.05),with greatest reduction of 8.28%observed under high nitrogen and high phosphorus treat-ment.Simultaneously,soil available potassium content decreased significantly across all fertilization treatments(P<0.05),with a maximum reduction of 52.79%observed under the high nitrogen and low phosphorus treat-ment.Correlation analysis further revealed a significant positive correlation between soil pH,available potas-sium content,and plant diversity(P<0.05).In conclusion,high-intensity joint nutrient inputs represent a criti-cal driving force for plant diversity decline and soil acidification in alpine meadows,while phosphorus availabil-ity plays a buffering role under low nitrogen conditions,albeit with limited regulatory capacity under high nitro-gen backgrounds.Long-term nitrogen and phosphorus inputs further affect plant community stability by acidify-ing the soil and altering nutrient balance.