黄土丘陵区人工林下草本层植物的结构特征

Structure Characteristics of Herbages Under Five Types of Artificial Forest Plantations in Loess Hilly Region

调查分析了黄土丘陵区5种人工乔灌林小叶杨（Populus simonii）林，山杏（Prunus armeniaca）林，山桃（Prunus davidiana）林，沙棘（Hippophae reamnoides）林，柠条（Caratana korshinskii）林下草本层植物的物种组成、结构特征及其差异。结果表明：5种人工乔灌林下共有37种草本植物，各人工林林下物种组成数量在17～25之间变化，其中以杏树林最多；5种人工林下草本层平均盖度、平均高度、平均生物量存在较大差异，但多样性指数相差不显著。总体来说，黄土丘陵区人工乔灌林下草本植物物种组成较少，物种多样性指数较低，结构参数较小，说明该地区人工林林下环境条件较差，严重影响草本植物个体的生长发育和群落结构。综合分析表明，具有较低林分密度和林冠郁闭度的山杏林是恢复状况相对最好的人工林，揭示了保持合理的林分密度，同时采取疏伐、修枝等管理措施是促进人工林生长发育以及林下草本植物物种多样性和片层结构改善的关键。

In order to understand the herbage biodiversity and synusia structure of artificial forest, we investigated herbages under five forest types of Populus simonii （ PS ） , Prunus armeniaca （ PA ） , Prunus davidiana （ PD ） , Hippophae reanmoides（HR） and Caragana korshinskii （CK）. In the 37 herbaceous species identified, only 18, 25, 20, 25 and 17species were present in the PS, PA, PD, HR and CK forests, respectively. For herbages, Sti- pa bungeana, Arthraxon h ispidus, Potentilla m ultifida and Thymus mongolicus were common in the five plantations. The average coverage, height and biomass of herbages in five artificial forests were different obviously, but community biodiversity was similar. In conclusion, low biodiversity and limited structure development（coverage, height, biomass） under five artificial forests indicate that the environments under artificial plantations are very bad and affect herbage individual development and community structure. Results show that the best herbage communi- ty has developed under the Prunus armeniaca forest with a relatively open canopy and low tree density, which suggests that the measures of tree thinning and canopy pruning to keep reasonable density are crucial for promoting artificial forest development, and improving herbage biodiversity and community structure.