地表火干扰时间序列上樟子松林竞争强度的变化

林火是樟子松林重要的干扰因子,通过空间代替时间对地表火干扰时间序列上的天然樟子松林进行全林木定位调查,以单木竞争模型分析林分不同组分的竞争强度,通过Kriging法估计了火后林下更新幼树的密度。结果表明,存活林木各组分的竞争强度均显著地降低;地表火干扰12 a后存活林木各组分的竞争强度均比火后1 a存活林木相应各组分的竞争强度显著地降低;另外,火后更新幼树也更多地趋于地表火干扰形成的林隙中。因此,地表火干扰时间序列上林木竞争强度显著的持续降低,火后存活个体将有更充足的可利用资源和环境,林火成为樟子松林发育演替的重要驱动力。

Variation of competition intensity across a chronosequence in surface fire- mediated Mongolian pine forest

Fire is a crucial disturbance factor in Mongolian pine forest. Under the approach of space for time substitution, competition intensities of trees were explored using the long tradition of distance-dependent competition index in two 1-hm2 fully mapped plots of Mongolian pine forest across a chronosequence of different intervals of time-since-fire, in Hulun Buir sand region, Inner Mongolia, China. Recruits were also estimated using the geostatistics method of kriging in a-1994-burned stand (B94). Our results show that (1) competition intensities of survival components were all significantly lower than those of pre-mortality agents; (2) competition intensities of survival components in B94 were significantly lower than those of corresponding components in B06 (a 2006-burned stand); (3) most recruits inhabited in the gaps triggered by surface fire in B94. Thus, competition intensity would decrease continuously and significantly across the chronosequence. The survival components may have more resources and space to live on due to the diminishments of competition intensities of stems, which are driven by surface fire, a dynamic driving force in the developing process of Mongolian pine forest.