Abstract
BackgroundHerbs 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.ResultsThe 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.ConclusionsThinning 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.
Highlights
Herbs are an important part of the forest ecosystem, and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances
In December 2012, 4 plots were thinned with actual intensity of 0, 17.2 %, 32.7 %, and 50.8 % respectively, which were defined as unthinning (CK), light thinning (LT), moderate thinning (MT) and heavy thinning (HT) (Liu et al 2019)
The relative abundance (RA), relative coverage (RC), relative height (RH), and importance value (IV) of herbaceous plants based on the obtained data were calculated
Summary
Herbs are an important part of the forest ecosystem, and their diversity and biomass can reflect the restoration of vegetation after forest thinning disturbances. If the disturbance severely destroys the original forest ecosystem, herbaceous plants will usually recover fast, thereby quickly improving the soil site conditions, reducing the intensity of solar radiation on the ground, and providing important protection for the regeneration of trees and shrubs and the growth of seedlings (Huang et al 2016). Reasonable thinning can maintain the stability and structure of the forest ecosystem while obtaining timber, and achieve sustainable forest management (Zhou et al 2015). Thinning can affect forest growth, understory vegetation regeneration, forest spatial structure, forest species diversity (Rong et al 2014; You et al 2015; Gong et al 2015; Huang 2016). Some studies have reported that thinning can promote the growth of tree height and diameter at breast height, increase forest stock and improve wood quality (An et al 2012), and improve the understory environment, reduce understory competition among species, and promote the increase in the growth and diversity of understory species, especially the understory herb layer (Li et al 2012)
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