刈割强度对大针茅草原地上生物量时间稳定性的影响

在草地刈割过程中, 群落地上生物量的时间稳定性与物种多样性及物种异步性关系密切。本文基于2014-2018年的野外刈割实验, 研究了围封(对照, 无刈割)、轻度(留茬8 cm)、中度(留茬5 cm)和重度(留茬2 cm)等不同刈割强度对内蒙古大针茅(Stipa grandis)典型草原地上生物量时间稳定性的影响。结果表明: (1)与围封相比, 刈割对群落时间稳定性无显著影响, 但对种群平均时间稳定性影响显著, 重度刈割处理的种群平均时间稳定性显著降低; 且种群平均时间稳定性与群落时间稳定性无显著相关关系, 表明这二者独立波动。(2)与围封相比, 重度刈割处理的物种丰富度显著降低, 但它与群落时间稳定性无显著相关关系, 表明物种丰富度不是群落地上生物量时间稳定性的主导因素; 此外, 重度刈割处理的群落抵抗力显著降低, 但也与群落时间稳定性无显著相关关系。(3)异步性与群落稳定性存在极显著正相关关系, 但刈割对异步性无显著影响, 故未造成群落稳定性显著变化。因此, 异步性可能是影响群落时间稳定性的主导效应之一, 在草地管理与利用过程中, 可从物种异步性角度来对草地稳定性进行评价。

Effects of mowing intensity on temporal stability of aboveground biomass in the Stipa grandis steppe

We conducted a mowing experiment between 2014 and 2018 to test the effects of different mowing intensity on the temporal stability of aboveground biomass in the Stipa grandis typical steppe in Inner Mongolia. Four mowing treatments were tested: enclosure (CK, no mowing), light mowing (stubble 8 cm), moderate mowing (stubble 5 cm) and heavy mowing (stubble 2 cm). We found that mowing had no significant effect on the temporal stability of the community compared with the enclosure, but it had a significant impact on the mean temporal stability of species. Under heavy mowing the mean temporal stability of species significantly decreased, and there was no significant correlation between the mean temporal stability of species and the temporal stability of community, indicating that these fluctuated independently. Compared with the enclosure (CK), species richness under heavy mowing reduced significantly, but had no significant correlation with community temporal stability, indicating that species richness was not the dominant factor in the temporal stability of community. In addition, the community resistance reduced significantly under heavy mowing but it also had no significant correlation with the temporal stability of the community. We found that there was a very significantly positive correlation between asynchrony and community temporal stability, but that mowing had no significant effect on asynchrony, so it did not cause significant changes in community stability. Therefore, asynchrony may be one of the dominant effects on the temporal stability of the community. In the process of grassland management and utilization, the stability of grassland could be evaluated from the perspective of species asynchrony.