不同频次刈割对羊草草原主要植物种群能量现存量的影响

对内蒙古羊草草原主要植物种群能量现存量对刈割频次响应的研究表明，在17年不同频次刈割干扰影响下，植物种群能量现存量随刈割频次的变化表现出不同的变化趋势，据此可以划分出3个不同的刈割响应类群：受抑种、耐刈种和受益种。受抑种包括羊草、羽茅、黄囊苔草、葱属植物和直根型杂类草; 耐刈种包括大针茅和冰草; 受益种包括洽草和糙隐子草。对于种群相对能量现存量而言，除羊草随刈割频次的增加呈显著下降趋势外，其他受抑种均随刈割频次的增加保持相对稳定，而受益种和耐刈种的相对值则随刈割频次的增加而呈增加趋势。同时，刈割对植物能量现存量的影响还表现在植物热值变化上，但变化幅度小于10%。

Effects of Mowing Frequency on the Energy Standing Crops of Major Populations in a Leymus chinensis Steppe of Inner Mongolia

Through field experiments involving different mowing frequencies for 17 years, we studied variation of the energy standing crops of major populations in a Leymus chinensis steppe of Inner Mongolia. The populations were divided into 3 mowing response groups accordingto response to mowing frequency: species restrained by mowing, species that benefited from mowing, and species whose distribution remained steady under mowing. The restrained species include L. chinensis, Achnatherum sibiricum, Carex korsinskyi, Allium spp. and other forbs,which decreased in distribution with increasing mowing frequency. The species that benefited include Koeleria cristata and Cleistogenes squarrosa, which increased in distribution withincreasing mowing frequency. The tolerant species include Stipa grandis and Agropyron michnoi, which did not change in distribution under mowing disturbance. As far as the relative energystanding crops, all but L. chinensis gradually declined in distribution with increasing mowing frequency; other restrained species did not change in distribution, while the species that benefited and those whose distribution was steady increased with increasing mowing frequency. Successive mowing also influenced the caloric values of some species but the variation was less than 10%.