Effect of thinning intensity on understory herbaceous diversity and biomass in mixed coniferous and broad-leaved forests of Changbai Mountain

Abstract

Background 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. Results 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. Conclusions 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.

Understory vegetation diversity, soil properties and microbial community response to different thinning intensities in Cryptomeria japonica var. sinensis plantations

“…In each subplot or quadrat, the number was counted, and coverage and frequency were measured for each understory plant species in October 2019. The Shannon index and Pielou index were calculated (Wang G. et al, 2021), and the relative species abundance was calculated to indicate the species richness for the shrub and herb layers.…”

Species diversity pattern and its drivers of the understory herbaceous plants in a Chinese subtropical forest

“…To date, the majority of our knowledge of forest biodiversity comes from woody plants (Murphy et al, 2016), which only represent a small fraction of biodiversity in the forest community. However, as an important component in forests, knowledge of community structure and species diversity for understory herbaceous communities remains scarce (Wang et al, 2021).…”

“…On the one hand, herbaceous plants and woody plants show quite differences in the root system (Cicuzza et al, 2013), leaves, and stature, which may lead to a significant difference in responding to light resources and available nutrition (Siebert, 2002;Ramadhanil et al, 2008), and ultimately present a different diversity pattern. On the other hand, local environmental factors, such as elevation, slope (Wiharto et al, 2021), soil (Beck and Givnish, 2021;Mao et al, 2021), community edge (De Pauw et al, 2021), thinning intensity (Wang et al, 2021), and climate change (Cacciatori et al, 2022), also have been shown to have significant effects on the diversity of understory herbaceous plants. However, the effect of habitat filtration may be different between woody and herbaceous plants.…”

“…However, these present studies mainly focus on tropical forests and cold temperate forests and usually do not take subtropical understory into consideration (Wang et al, 2021;Garg et al, 2022). Understory herbaceous plants in different climatic zones, such as tropical and temperate forests, may show different species richness and biodiversity (Gilliam, 2007).…”

Thinning can increase shrub diversity and decrease herb diversity by regulating light and soil environments

“…Another opposing view is that the improvement of light after thinning will reduce the diversity of understory vegetation. There are two main explanations: (1) In the cases of light-intensity thinning, the light environment changes a little but also produced forest gaps, which would lead to the death of shade-tolerant species (Wang et al, 2021); (2) As for the high-intensity thinning, the understory light is significantly enhanced, while one or few responsive species would quickly monopolize resources, and the other species died from the competition (Newman, 1973;Alaback and Herman, 1988;Thomas et al, 1999). Meanwhile, Soil properties are an important factor driving the distribution pattern of small-scale vegetation species (Siefert et al, 2012), and its influence on plant species diversity is complicated and does not show consistent regularity (Ning et al, 2019).…”