渐伐对草类-兴安落叶松林下植被多样性的影响

生物多样性关系到森林生态系统的稳定性及其功能的正常发挥，渐伐可为林下更新创造有利条件，进而对林下植被多样性产生影响。在大兴安岭兴安落叶松（Larixgmelinii（Rupr．）Rupr．）林区，采用空间代替时间的方法，应用Simpson指数、Shannon．Wiener指数和Pielou均匀度指数，以原始林为对照，研究不同林龄草类．兴安落叶松渐伐林下植被物种多样性的变化规律。结果表明：在群落恢复过程中，渐伐林灌木层多桦性指数呈先升高后降低的变化规律，草本层呈“降低→升高→降低”的趋势，且渐伐林在灌木层多样性指数最高的中龄林时期，草本层多样性指数最低；而原始林在生长发育过程中林下植被多样性指数变化规律一致，均呈“升高→降低→升高”的趋势；渐伐林和原始林林下植被多样性指数均在演替中期（中龄林或近熟林）最高，演替前期和后期相对降低。对比灌木层和草本层发现，渐伐林和原始林各龄林的simpson指数和Shannon．Wiener指数均为草本层〉灌木层。与原始林相比较，渐伐后群落各龄林灌木层Simpson指数、Shannon-Wiener指数和均匀性指数及草本层均匀性指数均显著增加，可见渐伐有利于林下植被的发育和多样性的提高。

Effect of successive cutting on the diversity of understory vegetation in herbage-Larix gmelinii forest

Higher plant diversity enhances the stability of disturbed forest ecosystem, successive cutting may stimulate the generation of understorey vegetation and then change the diversity. Compared with the virgin Larix gmelinii forest, we analyzed the effect of successive cutting on the shrubby and herbaceous diversity in herbage-Larix gmelinii forest which in different succession process with applying Simpson index, Shannon-Wiener index and Pielou evenness index. The results showed that the shrubby and herbaceous diversity under different succession process has been increased significantly when compared with the corresponding stage in virgin forest. The diversity was always higher in herbaceous than in shrubby both in the successive cutting forest and in the virgin forest when showed with the Simpson index and Shannon-Wiener index. The different development mode was found in the shrubby and herbaceous ofherbage-Larix gmeliniiforest during the community successive process. The lowest herbaceous diversity was coincided with the largest shrubby diversity in middle age of successive cutting forest. While the diversity of shrubby and herbaceous under virgin forest showed harmoniously dynamic, which showed highest diversity in the middle succession stage and lowest in the early and later succession stage. In conclusion, our study demonstrates that the proper successive cutting is needed for the understorey vegetation generation and the increase of diversity in Larix gmelinii forest of cold temperate zone.