广西大青山西南桦人工林林下植物优势种群分布格局

Effects of different stand types on spatial distribution characteristics of understory plants in Betula alnoides plantations at Daqingshan mountain, Guangxi

以广西大青山林区西南桦纯林、西南桦×灰木莲混交林和西南桦×马尾松混交林作为研究对象,调查林下植物种类、数量和盖度等植被因子,应用重要值和扩散系数(DI)、负二项式分布(K)和聚块性指数(PAI)等测定指标,探讨3种造林模式对西南桦人工林林下植物优势种群分布格局的影响。结果表明:(1)西南桦纯林植物种类最多,西南桦×马尾松混交林次之,西南桦×灰木莲混交林中物种数量最少。(2)林下共有幼树优势种漆树,在西南桦×马尾松混交林呈聚集分布,但聚集程度不够明显,在纯林和西南桦×灰木莲混交林为均匀分布;灌木九节和藤本植物玉叶金花,在西南桦×灰木莲混交林和西南桦×马尾松混交林呈强烈聚集分布,两者在纯林聚集程度不明显;弓果黍和五节芒均在3种西南桦林内均呈强烈聚集分布。(3)3种造林模式对西南桦林下植物优势种及其分布格局的影响存在差异;我们建议适当立地选择、减少西南桦纯林比例,宜选取马尾松作为伴生树种混交造林,采取合理的营林措施,改善林分环境,提高林分异质性,从而促进西南桦人工林健康、高效的可持续经营。

The pure plantation of Betula alnoides, mixed plantations between Betula alnoides and Manglietia glaucaor, Pinus massonianain Daqingshan mountains area were selected to study the effect of afforestation modes on the distribution pattern of dominant population in the understory of Betula alnoides plantation by investigating the species, number and coverage of understory plants, means of important values and diffusivity coefficient（DI）, negative binomial distribution（K） and clustering index（PAI）. The results show that：（1） the pure plantation of Betula alnoides had the largest number of plant species, followed by mixed plantation between Betula alnoidesand Pinus massoniana, and mixed plantation of Betula alnoides and Manglietia glauca.（2） The dominant species Toxicodendron delavayi was distributed aggregately in the understory of Betula alnoides×Pinus massoniana mixed plantation. However, it was evenly distributed in the other plantations. Psychotria asiatica and liane Mussaenda pubescenswere clumped significantly both in Betulaalnoides×Manglietia glauca and Betula alnoides×Pinus massoniana mixed plantations, while the aggregation intensity was weaker in Betula alnoides pure plantation. Moreover, Cyrtococcum patens and Miscanthus floridulus showed clumped pattern in all plantations.（3）There were significant different in the understory dominant species and their distribution among three kinds of afforestation modes. Therefore, some measurements were taken, such as selecting proper site, reducing the proportion of Betula alnoidespure forest, selecting the Pinus massoniana mixed, to improve the forest environment and heterogeneity, and thus promote the healthy and efficient development of Betula alnoides plantation.