Abstract: Grazing intensity and resource availability can affect the compensatory growth of defoliated plants. In this paper, a 2-year field manipulative experiment was conducted to study the effects of clipping (stubbled 1 cm, stubbled 3 cm, and unclipped), fertilizing (fertilized and unfertilized), and watering (watered and nonwatered) on the compensatory growth of Elymus natans. The compensatory height (CH), specific leaf area (SLA), net photosynthesis rate (NPR), and relative growth rate (RGR) were measured, aimed to approach the compensatory mechanism of the species. With increasing clipping intensity, the ramet density, SLA, and RGR of E. nutans increased significantly, while the CH decreased. No significant difference was observed in the leaf NPR among different clipping treatments. Fertilizing greatly promoted the CH, SLA, NPR and RGR of the species. Watering and the interaction among clipping, watering, and fertilizing had no significant effects on the species. These results suggested that E. nutans had certain density compensation mechanism, but the undercompensation in plant height resulting from the CH was restrained by clipping. An appreciable increase in SLA and RGR after defoliated was not enough to induce overcompensation in plant height. However, fertilizing could enhance the compensation ability, and promote the plant species tolerance against defoliation. Our results confirmed the improved limiting resource model (LRM).

Key words: Organic matter, Soil microbial community, Biolog GN2, Carbon source