Responses of plant morphology and seed quality to long-term overgrazing in Leymus chinensis
Leymus chinensis (Trin.) Tzvel. is a perennial species of Gramineae. It is also a palatable forage; but under severe and prolonged grazing, the individuals of L. chinensis become miniaturized and do not immediately revert to normal when grazing stress is removed. To explore the miniaturization mechanism, we compared the difference in the 3-year period 2002 to 2004 between miniaturized L. chinensi and normal L. chinensis on morphological character and asexual reproduction. The result shows that 1000-seed weight, germination percentage, plant height, fiber root length, height of first ramet, individual biomass and seed weight of single spike were significantly lower (p < 0.01) in miniaturized plants, but the tiller number was higher (p < 0.05) than the normal ones. Overgrazing was the main factor causing individual miniaturization of L. chinensis. We propose that individual miniaturization was a protection strategy to adapt all kind of stress and present a negative feedback mechanism. This study maybe also an important step towards understanding the succession sequences in the restoration of typical steppe and delivering the baseline reference for a sound steppe management plan.
Key words: Leymus chinensis, grazing succession, individual miniaturization, tiller number.