Thinning affects microbial biomass without changing enzyme activity in the soil of Pinus densiflora Sieb. et Zucc. forests after 7 years

Abstract

& Key message Thinning increased microbial biomass but did not alter enzyme activities in the soil of Pinus densiflora Sieb. et Zucc. forests in South Korea. This effect of thinning was larger under a relatively heavy thinning intensity, but there was divergence in the magnitude between sites. & Context The balance between microbial biomass accumulation and enzymatic C and N assimilation determines the level of bioavailable C and N. However, the effects of thinning on these parameters remain contradictory and unconfirmed. & Aims The effects of thinning intensity on microbial biomass and enzyme activity were assessed in the soil of Pinus densiflora Sieb. et Zucc. forests in South Korea. & Methods Un-thinned control and 15 and 30% basal area thinning treatments were applied to two 51-to 60-year-old P. densiflora forests with different management histories, topographies, rainfall amounts, and soils. Seven years after thinning, microbial biomass and activities of N-acetyl-glucosaminidase, β-glucosidase, cellobiohydrolase, β-xylosidase, phenol oxidase, and peroxidase were measured before and after seasonally concentrated rains and at 0-10 cm depth. & Results Microbial biomass was generally highest under the 30% basal area thinning and lowest under the control, and was positively correlated to total soil C and N. The increase in microbial biomass was lower at the site displaying sandier, drier, and more acidic soils and retaining smaller amounts of thinning residue. Conversely, thinning had no significant effect on activities of all enzymes at both sites in both periods.

Seasonal Variations and Thinning Effects on Soil Phosphorus Fractions in Larix principis-rupprechtii Mayr. Plantations

“…Thinning can affect soil microbial structure and function by altering microenvironments (e.g., soil moisture and temperature), as well as the quality and quantity of substrate inputs (e.g., litter and roots), which can further influence soil P bioavailability [13]. Kim, et al [14] reported that thinning promotes the accumulation of microbial biomass, and is positively correlated with total soil C and N. Furthermore, this effect of thinning was found to increase with thinning intensity. Due to an increase in rainwater and a reduction of transpiration [15], soil moisture content in temperate broad-leaved deciduous forests [16], northern evergreen coniferous forests [17], and subtropical forests [18] was significantly higher in heavily thinned forest stands.…”

Soil Element Stoichiometry Drives Bacterial Community Composition Following Thinning in A Larix Plantation in the Subalpine Regions of Northern China

“…For example, Shen et al (2018) [14] observed increases in SOC, STN, and STP after thinning. Yang et al (2017) [11] and Kim et al (2018) [43] suggested a positive influence of thinning on the soil microbial biomass. We found the availability of soil nutrient contents also increased via the variation of understory environmental factors after thinning, as evidenced by higher SBD, SMC, ammonium nitrogen, nitrate nitrogen, and available phosphorus (Table 1).…”

“…Soil microbial community activity increases when more decomposable organic matter is available, especially on the soil surface [49,58]. Therefore, taking thinning intensity, stand type, and restoration time into consideration is necessary to interpret the response mechanism of bacterial diversity to thinning activity [43].…”

The Effect of Forest Thinning on Soil Microbial Community Structure and Function

“…forests, where the abundance of soil microbes increased significantly after seven years of thinning [44]. This is because thinning had increased carbon inputs from litter, root exudates, and dead fine root [43,44]. However, decreased soil microbial abundance in forest thinning had also been reported [11].…”