Effects of clipping, fertilizing and watering on compensatory growth of Kobresia humilis
刈割、施肥和浇水对矮嵩草补偿生长的影响

Aims Kobresia humilis meadow is a disturbance-dependent (disclimax) community resulting from long-term and heavy grazing. Our objectives were to (a) examine how the compensatory growth of K. humilis (including ramet density, compensatory height and compensatory aboveground biomass per ramet) varies with different levels of clipping, fertilizing and watering and (b) examine changes in specific leaf area (SLA), lamina net photosynthetic rate (Pn) and relative growth rate (RGR) in order to reveal the compensatory mechanisms of the species. Methods Our field experiment was carried out at the Haibei Research Station of the Chinese Academy of Sciences from 2007 to 2009. The experiment used a split-plot design with clipping treatment on the whole plot (stubbled 1 cm, 3 cm and unclipped) and both fertilizer (fertilized and unfertilized) and water (watered and unwatered) treatments in subplots. We analyzed effects of clipping, fertilizing and watering on the response variables by multivariate ANOVA. We used stepwise regression analysis to determine the contribution of SLA, Pn and RGR to compensatory growth and Pearson’s correlation to determine the correlation among ramet density, compensatory height and compensatory aboveground biomass. Important findings Compensatory height and SLA were reduced after clipping; RGR of ramet height and aboveground biomass, ramet density and compensatory biomass were increased. Fertilizing can increase ramet density, compensatory height, compensatory biomass, RGR of ramet height and aboveground biomass, SLA and Pn. The effect of watering on compensatory height and RGR of ramet height under stubbled 1 cm clipping was not obvious, but reduced them under stubbled 3 cm clipping. The interactions of clipping, fertilizing and watering showed that the relation between clipping and fertilizing is “antagonistic” and the relation between clipping and watering is “cooperative”. Although K. humilis appeared under compensation in plant height, fertilizing could enhance the compensation ability and promote tolerance against defoliation at a certain level of clipping.