不同轮割制度对内蒙古大针茅草原群落组成的影响

野外试验设计结合室内分析,探讨了以大针茅(Stipa grandis)为建群种的锡林郭勒典型草原区不同轮割制度对割草场产量、物种组成、群落结构及营养状态的影响.一年割2次的利用方式在短期内生物量收获较大,但这种状态较难持续;完全围封不利用也不利于草场恢复;一年割1次的适度刈割制度在当地较为合理,但是连年刈割会导致草场营养贫瘠,植物补偿现象减弱.越高频刈割对大针茅和羊草(Leymus chinensis)种群的影响越严重,产量明显减少,重要值下降,而糙隐子草(Cleistogenes squarrosa)种群则相反;随刈割频度的增高根茎禾草在群落中的相对生物量上升,丛生禾草下降,二者明显互补.刈割对土壤和植物的N素质量分数影响最明显,连续刈割3年的土壤有效N质量分数较对照区降低18.62%,且达到显著水平,有效p,K质量分数也分别下降8.79%和1.93%.

EFFECT OF MOWING SYSTEMS ON COMPOSITION OF STIPA GRANDIS COMMUNITY IN INNER MONGOLIA STEPPE

In the grassland region of Inner Mongolia,a large amount of grass is mowed by herdsmen in autumn and is prepared to feed to livestock in winter.Soil nutrient content is deficient seriously because of mowing continuously,and the grassland has been degenerated more and more.Considering of these problems,The effect of different mowing systems on the standing crops,species composition,community structure and nutrient content of Stipa grandis grassland of typical steppe is designed and analyzed.The results show that the standing crops of community mowed twice one year is higher in short period,but can't be persistent in long run,and the yield of no mowing control plots is also low,so the system of mowing once a year is reasonable for local grassland correspondingly.But the grassland mowed with this frequency for a long time must also be degenerate,especially deficit soil nutrient content.For example,Compared to control plot,soil nitrogen content of plots mowed once a year can be reduced significantly by 18.62% in third year.Tall grasses mowed with high-frequency will be seriously affected,such as Stipa grandis and Leymus chinensis,concrete phenomenon is showed as following: the standing crops of Stipa grandis reduced,tall grass(Stipa grandis and Leymus chinensis) standing crops percentage in community decreased too,important value lessened,and nutrient content is deficient.While the situation of Cleistogenes squarrosa is reverse.And for the two functional groups of life forms,rhizome grass and bunch grass,high frequent mowing could make much higher standing crops percentage of rhizome grass and less of bunch grass,the two functional groups have significant compensating action,and they have negative correlation.