Herbs are an important part of the forest ecosystem, and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances. Based on the near-mature secondary coniferous and broad-leaved mixed forest in Jilin Province Forestry Experimental Zone, this study analyzed seasonal changes of species diversity and biomass of the understory herb layer after different intensities of thinning. The results showed that although the composition of herbaceous species and the ranking of importance values were affected by thinning intensity, they were mainly determined by seasonal changes. Across the entire growing season, the species with the highest importance values in thinning treatments included Carex pilosa, Aegopodium alpestre, Meehania urticifolia, and Filipendula palmata, which dominated the herb layer of the coniferous and broad-leaved mixed forest. The number of species, Margalef index, Shannon-Wiener index and Simpson index all had their highest values in May, and gradually decreased with months. Pielou index was roughly inverted “N” throughout the growing season. Thinning did not increase the species diversity. Thinning can promote the total biomass, above- and below-ground biomass. The number of plants per unit area and coverage were related to the total biomass, above- and below-ground biomass. The average height had a significantly positive correlation with herb biomass in May but not in July. However, it exerted a significantly negative correlation with herb biomass in September. The biomass in the same month increased with increasing thinning intensity. Total herb biomass, above- and below-ground biomass showed positive correlations with Shannon-Winner index, Simpson index and Pielou evenness index in May. Thinning mainly changed the light environment in the forest, which would improve the plant diversity and biomass of herb layer in a short time. And different thinning intensity had different effects on the diversity of understory herb layer. The findings provide theoretical basis and reference for reasonable thinning and tending in coniferous and broad-leaved mixed forests.

中文翻译：

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间伐强度对长白山针阔混交林林下草本植物多样性和生物量的影响

草本植物是森林生态系统的重要组成部分，其多样性和生物量可以反映森林间伐干扰后植被的恢复情况。以吉林省林业试验区近成熟次生针阔混交林为研究对象，分析了不同疏伐强度后林下草本层物种多样性和生物量的季节变化。结果表明，虽然草本植物种类组成和重要性值排序受间伐强度影响，但主要受季节变化影响。在整个生长季节，间伐处理中具有最高重要性值的物种包括 Carex pilosa、Aegopodium alpestre、Meehania urticifolia 和 Filipendula palmata，以针阔混交林草本层为主。物种数、Margalef 指数、Shannon-Wiener 指数和 Simpson 指数均在 5 月份达到最高值，并随月份逐渐下降。Pielou指数在整个生长季节大致倒“N”。间伐并没有增加物种多样性。间伐可以促进总生物量、地上和地下生物量。单位面积的植物数量和覆盖率与总生物量、地上和地下生物量有关。5月平均高度与草本生物量呈显着正相关，7月无显着正相关。然而，它与9月份的草本生物量呈显着负相关。同月生物量随着间伐强度的增加而增加。总草本生物量，5月份地上部和下部生物量与Shannon-Winner指数、Simpson指数和Pielou均匀度指数呈正相关。间伐主要改变森林中的光环境，在短时间内提高草本层的植物多样性和生物量。不同间伐强度对林下草本层多样性的影响不同。研究结果为针阔混交林合理间伐抚育提供了理论依据和参考。