放牧和氮磷添加对典型草原植物叶片养分回收的影响OA

Research on nutrient cycling in grassland ecosystems has mainly focused on external nutrient cycling,whereas relatively limited attention has been paid to internal nutrient resorption and reutilization within plants.Grazing and nutrient addition are common management practices in grassland ecosystems,but their regulatory mechanisms on leaf nutrient resorption remain unclear.Based on a long-term controlled experiment involving grazing and nitrogen-phosphorus addition in a typical steppe of Inner Mongolia,this study selected three representative dominant plants,Leymus chinensis,Stipa grandis,and Cleistogenes squarrosa,to systematically examine how grazing and nitrogen-phosphorus addition affected soil nutrient status,foliar nitrogen and phosphorus concentrations,and nutrient resorption traits.The results showed that grazing only increased soil total phosphorus content,whereas its main effects on nitrogen and phospho-rus resorption proficiency in L.chinensis,S.grandis and C.squarrosa were not significant.In addition,grazing did not significantly affect nitrogen or phosphorus resorption efficiency in the three species.Nitro-gen and phosphorus addition decreased nitrogen and phosphorus resorption proficiency in L.chinensis and S.grandis,respectively,but had no significant effect on nutrient resorption proficiency in C.squarrosa.Nitrogen and phosphorus addition also significantly altered nutrient resorption efficiency among different species.Specifically,nitrogen addition reduced both nitrogen and phosphorus resorption efficiency in L.chinensis,but increased nitrogen resorption efficiency in C.squarrosa;phosphorus addition increased phos-phorus resorption efficiency in C.squarrosa;and nutrient resorption efficiency in S.grandis remained gen-erally stable across different treatments.Correlation analysis showed that leaf nitrogen and phosphorus con-tents and nutrient resorption characteristics were closely associated with soil nutrient status,although the direction and magnitude of responses differed among species.In conclusion,under the grazing intensity and timescale of this experiment,nitrogen and phosphorus addition serves as a key factor regulating nutrient resorption in typical steppe plants,whereas the direct regulatory effect of grazing is relatively weak.This study provides a scientific basis for understanding the internal nutrient cycling processes in grassland plants under the combined effects of grazing disturbance and external nutrient inputs.