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作 者 ：Zhu Zhi-hong and Sun Shang-qi

Keywords:Total nonstructural carbohydrate, Seasonal variation, Defoliation, Kobresia hu-milis,

Abstract:The seasonal variation of total nonstructural carbohydrates (TNC) concentration in crowns and roots of Kobresia humilis were determined during 1993～ 1994. The effects of defoliation on TNC concentration and the relationship between the aboveground growth and TNC concentration in crown were analysed. TNC were mostly stored in crowns exhibiting great seasonal fluctuations with narrow V-shaped cycle. TNC concentration of crown varied inversely with the net increased of leaf number in the entire growing season, but it dependedlargely on the dead to survival leaf ratio in the early growth season, with a constant of 20.59% at a ratio of 0.16, either decreased or increased when the ratio was greater or less than 0.16 respectively. In the later, there was a significant positive correlation between the TNC concentration of crowns and the cumulative leaves. However, in mid-season, no significant correlation was found between the aboveground growth and the TNC concentration of crowns. The reserve pools (concentration X crown biomass) had no significant differences among various grazing treatments. Intense clipping at two phenological stages caused reduction of reserves during regeneration, but at the end of the growth season, there was no significant difference between clipped and unclipped plants, as well as between clipping intensities.TNC concentration of crowns and roots significantly decreased following early heavy clipping, but it recovered rapidly in crowns. Clipping at mid-stage affected greatly on TNC con-centration of roots. Clipping influenced more on TNC concentration of roots but grazing had more influence on that of crowns.

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