以甘南亚高山草甸常见牧草垂穗披碱草(Elymus nutans)为对象，通过考察种群密度、施肥与刈割处理等对植物生长和生殖的影响效应，比较了垂穗披碱草在5个密度及2个施肥实验处理条件下对4种刈割处理的补偿性反应特点。结果表明，在所有密度及施肥处理条件下，早期轻度刈割处理 (分蘖期刈割，留茬4 cm) 都有利于植物的补偿作用，后期重度处理 (拔节期刈割，留茬2 cm) 可显著降低植物的地上部分生物量及生殖部分干重 (穗重)。在不施肥情况下，刈割对垂穗披碱草的影响程度随种群密度而加大，在低密度处理中早期轻度刈割的植物发生了超补偿。可以认为，低密度种群中植物具有较多的分蘖是植物在刈割后表现出较高补偿能力的一个重要生物学原因。实验还发现，施肥可提高植物个体的分蘖能力和秆叶再生能力，因而总体上可增强植物的补偿能力，并且在中等密度条件下垂穗披碱草的补偿能力较强，尽管没有发生超补偿现象。不过，施肥主要是有利于植物地上营养器官的补偿，生殖器官的补偿程度较小一些。试验结果对科学管理人工草场具有一定的指导意义。
Studies of simulated grazing of Elymus nutans, a common species in subalpine meadows in Gannan, were conducted to assess the effects of population density and fertilization on the plant compensatory responses to mowing. We subjected Elymus nutans to different types of mowing treatment, early or late (3 June or 28 July, 2001) and light or heavy mowing (4 cm or 2 cm from the ground), to different levels of soil fertility (unfertilized or fertilized), and to different levels of intraspecific competition (five designed sowing densities: 100, 400, 800, 1 600 and 3 200 seeds·m-2).Plant responses to these treatments were measured as changes in plant aboveground biomass and inflorescence dry weight, and the degrees of compensation were measured as changes in compensation indixes that related plant aboveground biomass or inflorescence dry weight of mowed to control plots. Our results showed that population density, soil fertility and mowing treatments significantly affected plant growth, and there were no interactions between two factors and among three factors (density × soil fertility × mowing).Mowed plants growing in early and light mowing treatment plots were more or less enhanced, and grew better than in other treatment plots. Further, early and light mowed plants in the low-density (100 seeds·m-2) and unfertilized plots showed enhanced growth (overcompensation), and the number of tillers and plant compensatory ability decreased with increasing density. These results indicated that plant compensation ability was directly related to the number of tillers. The compensation may be considered as an indirect consequence of growth of low tillers when apical dominance is removed.Mowed plants in fertilized plots showed enhanced growth irrespective of the population density. Our results support the view that rapid plant regrowth was more likely to occur under low-stress conditions. We also found that plant vegetative growing than reproductive growing was enhanced when the soil was fertilized. We suggest that overcompensation should not generally be considered as an adaptive response, but rather as a maximal end in the continuum of plant responses to herbivory.
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