低效低质人工林优化改造后林下植被多样性研究

采用样地调查法，对经过人工优化改造的陕西吴起县城周边的低效低质林，选取了其中的11种改造模式（即人工林林分）及1块天然次生林，进行了林下植被多样性的研究。结果表明：12个样地共调查到55种植物，各样地林下植物种有11-23种；阿尔泰狗娃花（altaicus（Willd．）Novopokr．）、达呼里胡枝子（davuriea（Laxm．JSehi月d1．）、赖草（JPc口li”淞（GeorgOTzveL）、针茅（capillataLinn．）、毛连蒿（vestitaWall．exBess．）和委陵菜（chinensisSer．）是最常见的种。而赖草、毛连蒿、达呼里胡枝子、华北米蒿（giraldiiPamp．）、茵陈蒿（capillarisThunb．）、艾蒿（1avandulaefolia DC．）是改造后人工林林下重要值最大的优势种，植物偶见种也较多；不同样地林下植物多样性指数差异显著；物种多样性指数Gleason指数和种间相遇机率（PIE）指数变化趋势基本一致，Simpsom指数、Pielou均匀度指数变化趋势与前两者相反，Shannon—Wiener指数变化趋势不明显。分析表明：人工林林下植被多样性较之天然林要差，其多样性受人工林林分密度、林龄及林分组成等影响。

Understory biodiversity of managed plantation stands from the inefficient and inferior forests

The understory biodiversity was studied using ground plot investigation for eleven managed plantation stands from inefficient and inferior forest and one natural secondary stand （control）. As a result, there were 55 species on all 12 plots, ranging from 11 to 23 species. The most commonly happened species were Altaicus OVilld.） Novopokr., Ddavurica （Laxm.） Schindl., Capillata Linn., Vestita Wall. ex Bess., Chinensis Set. The dominant species were Secalinus （Georgi） Tzvel., Vestita Wall ex Bess., Davurica （Laxm.） Schindl., Giraldii Pamp., Capillaris Thunb., Lavandulaefolia DC. There were significant difference in biodiversity between plots. The variation tendency of Gleason index was consistent with that of PIE index. Simpson index and Pielou evenness index was opposite to Gleason and PIE. There was no apparent variation in Shannon--Wiener Index. It was suggested that the biodiversity of plantation stands was influenced by stand age, density, and composition. The biodiversity of plantation stand was poorer than natural forest.