毛乌素沙地杨树人工林林下植物群落特征

目的 研究人工林林下植物群落特征及其与林分因子的关系，对沙地植被恢复成效的评价和人工林管理具有重要意义。 方法 本研究以毛乌素沙地杨树人工林群落为研究对象，调查研究林下植物群落特征，并重点探讨了林分郁闭度、密度等林分因子对林下植被的影响。 结果 研究区杨树人工林林下共发现植物32种，隶属于12科28属，其中豆科、禾本科、菊科植物最多，占总植物种的62.51%；林下草本植物生活型以多年生草本植物为主，占总物种的78.13%，植物水分生态类型以旱生、中旱生植物为主，占总物种数的75.00%，其次为旱中生和中生植物；林下草本层Margalef丰富度指数变化范围为1.20～3.17，Simpson优势度指数变化范围为0.48～0.88，Shannon-Wiener多样性指数变化范围为0.95～2.34，Pielou均匀度指数变化范围为0.16～0.48，林龄32年生时林下物种多样性最高；结构方程模型结果显示林分郁闭度和密度与林下灌木层盖度之间存在负效应关系，人工林郁闭度较高时，林下无灌木层形成。林分郁闭度的增加有利于草本层的发育，而林分密度与草本层盖度、地上生物量、物种丰富度和Shannon-Wiener多样性指数之间存在负效应关系，灌木层对草本层的影响与乔木层相似。 结论 毛乌素沙地杨树人工林林下草本植物多样性较高，灌木种类较少，其大小受郁闭度和密度等林分因子的影响较明显。适当调控林分密度和结构，将有利于毛乌素沙地杨树人工林林下物种多样性的维持和近自然改造。

Characteristics of Understory Plant Community of Poplar Plantation in Mu Us Sandy Land

Objective To study the characteristics of understory plant communities of plantations and their relationship with stand factors, which is of great significance for evaluating the effectiveness of vegetation restoration in sandy areas and managing plantations. Methods In this study, based on the poplar plantation in Mu Us sandy land the understory plant community was investigated. The effects of stand factors such as canopy density and density on understory vegetation were studied. Results The results showed that a total of 32 species of herbaceous plants belonging to 28 genera of 12 families were found in the herbaceous layer under the poplar plantation in the study area,. Among them, Leguminosae, Gramineae and Compositae plants were the most species, accounting for 62.51% of the total plant species. The life forms of understory herbaceous plants were mainly perennial herbaceous plants, accounting for 78.13% of the total species. The plant water ecotypes were mainly xerophytes and mesoxerophytes, accounting for 75.00% of the total species, followed by xeromesophytes and mesophytes. The Margalef richness index, Simpson dominance index, Shannon-Wiener diversity index and Pielou evenness index of understory herb layer ranged from 1.20 to 3.17, 0.48 to 0.88, 0.95 to 2.34 and 0.16 to 0.48, respectively. The species diversity was the highest when the forest age was 32 years. The results of the structural equation model showed that canopy density and stand density were negatively correlated with the coverage of the understory shrub layer. When the plantation canopy density was high, no shrub layer was found under the forest. The increase of canopy density was beneficial to the development of herbaceous layer, and there was a negative effect relationship between stand density and herbaceous layer, which affects the growth of herbaceous plants under the forest. The effect of shrub layer on herbaceous layer was similar to that of tree layer. Conclusion The diversity of understory herbaceous plants in poplar plantations in Mu Us Sandy Land is high, and there are fewer shrub species. The size is obviously affected by stand factors such as canopy density and stand density. Appropriate regulation of stand density and structure will be conducive to the maintenance of understory species diversity and close-to-nature management of poplar plantations in Mu Us Sandy Land.