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 (δ15N) under four grazing intensities. It was demonstrated that soil δ15N 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 δ15N 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.