Stand density is a critical factor impacting the diversity of understory plants. We analyzed the diversity of understory plants and soil seed banks, as well as their relationship by setting up three planting densities in a Pinus massoniana plantation, including low density (1575 trees·hm-2, D1), medium (2474 trees·hm-2, D2), and high (3550 trees·hm-2, D3). It aimed to provide a scientific basis for the implementation of the multi-objective sustainable development of plantations. The results showed that there were 70 species of herbs and shrubs belonging to 42 families and 62 genera. D1 was dominated by heliophiles, whereas both the D2 and D3 were dominated by shade-tolerant species. The Margalef (M), Shannon (H), Simpson (D), Pielou (Jsw), and Altalo (Al) indices of the herbs and shrubs exhibited a downward trend with increasing stand den-sity. In the herb layer, D1 and D3 showed significant difference in H, D, Jsw and Al. There were significant differences of Jsw and Al in the shrub layer among the three stand densities, but no diffe-rence of H and D. H, D, Jsw and Al in the soil seed bank first decreased and then increased with increasing stand density, with species richness and diversity being the highest in D1. The similarity coefficient of Jaccard and Sorensen among different stand densities was low. In the herb layer, M was positively correlated with Jsw. The correlations between stand density and H, D, Jsw and Al were greater in the shrub layer than in the herb layer. There was significant negative correlation between stand density and Jsw both in the shrub and herb layers. The stand density of 1575 trees·hm-2 was comparatively beneficial for the development of understory, plant diversity, and sustainability of P. massoniana plantation.
林分密度是影响林下植物多样性的重要因子。本研究以马尾松人工林为对象,设置低密度(1575株·hm-2,D1)、中密度(2474株·hm-2,D2)和高密度(3550株·hm-2,D3)3个林分密度,分析林下植物和土壤种子库多样性及二者的关系,为马尾松人工林实现多目标可持续发展提供科学依据。结果表明: 3种林分密度林下草本与灌木植物共有42科62属70种,D1密度以喜光植物种类分布较多,而D2、D3密度以耐阴植物为主;3种林分密度间的草本、灌木的Margalef (M)、Shannon (H)、Simpson (D)、Pielou (Jsw)、Alatalo (Al)指数均随林分密度增加而呈下降趋势,且在草本与灌木层中对密度的响应不同。在草本层中,D1与D3的H、D、Jsw、Al指数均存在显著差异;在灌木层中,不同林分密度Jsw和Al指数存在显著差异,H和D指数差异不显著。土壤种子库H、D、Jsw和Al指数均随林分密度增加呈先下降后升高趋势,D1密度的物种丰富度及多样性最高;不同林分密度下土壤种子库Jaccard与Sorensen相似性系数均较低。草本层M与Jsw指数呈显著正相关;灌木层林分密度与H、D、Jsw、Al指数的相关性大于草本层,而草本、灌木层的林分密度与Jsw指数均呈显著负相关。林分密度1575株·hm-2是马尾松林下植被生长发育较为合适的密度,能够维持林下植物多样性,有利于马尾松人工林的可持续经营。.
Keywords: Pinus massoniana plantation; species composition; stand density; α diversity.