Effect of Grazing Intensity on Soil and Plant δ15N of an Alpine Meadow

Abstract

The mechanisms underlying the retention of inorganic N were still not well understood in an alpine meadow on the Tibetan Plateau as well as in other high-altitude meadow sites greatly grazed and disturbed. We conducted field soil and dominant species foliar nitrogen natural abundance of stable isotope ratios (delta N-15) under four grazing intensities. It was demonstrated that soil delta N-15 decreased significantly from 5.83 +/- 0.20% to 2.17 +/- 0.48% at 0-10 cm with the elevation of grazing intensity. Grazing reduced the degree of ecosystem N openness. The delta N-15 value of surface soil was mainly affected by soil total nitrogen. Furthermore, the degree of nitrogen limitation increased with grazing elevation for sedge family and Gramineae family plants.