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Downed woody debris (DWD) can alter the chemical and biological properties of forest soils, and this process is affected by the degree of DWD decay. Our aim was to assess the effects of the entire decay process of DWD on the associated soil microbial communities. Here, we examined the differences in soil microbial community size and composition among five decay stages (DC Ⅰ–Ⅴ) of Masson pine (Pinus massoniana Lamb.) at two soil depths in a climate transitional forest and then linked these differences to soil chemical properties. The decay of DWD increased soil total PLFAs, and the complexity of soil microbial networks was highest in stage Ⅱ and then decreased with the decay stage. The relative abundance of fungi increased with the decay stage, while the relative abundance of gram-positive bacteria decreased with the decay stage. The microbial community composition at a soil depth of 0–10 cm was mainly driven by soil pH and organic C (SOC), and at a depth of 10–20 cm, soil pH was the primary determinant of microbial community composition. Our findings suggest that DWD decomposition reduces microbial physiological stress, promotes fungal growth, and stimulates microbial biomass, highlighting the positive impact of DWD on forest soils. Future research is needed to elucidate the universal effects of DWD decomposition on soil properties, especially focusing on the response of soil microbial processes to the decomposition time of DWD. [ABSTRACT FROM AUTHOR]

• Rs and Rh was reduced more in D50 than in D25. • Thinning decreased Rs and Rh. • Changes in Rs and Rh can be attributed to varied soil moisture and microbial biomass C. Silvicultural practices are essential for alleviating the impacts of drought on the health and structure of forest ecosystems. However, it is yet uncertain how precipitation reduction and forest management together affect soil carbon (C) cycling. Therefore, we carried out a one-year field manipulative experiment to examine the influences of decreased precipitation and thinning on soil respiration (Rs) and its heterotrophic component (Rh) in a coniferous-broadleaved mixed forest in a warm temperate-subtropical climate transition zone in Central China. We found that thinning significantly suppressed Rs by 13.9%, but decreased precipitation by 25% did not affect it, and decreased precipitation by 50% significantly decreased it by 18.6%. Thinning significantly reduced Rh by 12.2%, and decreased precipitation by 25% and 50% significantly decreased Rh by 15.9% and 23.5%, respectively. The decreasing Rh was primarily to blame for the reduction in Rs. Reduced soil moisture and microbial biomass C were the key regulators of declines in Rh and Rs caused by decreased precipitation or thinning. There was no evidence of an interactive impact between decreased precipitation and thinning on Rs or Rh. Our findings indicate that decreased precipitation and thinning may alleviate soil C release in the short term and enhance their potential benefits for soil C accumulation under future climate change scenarios. [ABSTRACT FROM AUTHOR]

• Effect of 3-yr litter/understory removal on soil microbial community was studied. • Both litter and understory removal change microbial biomass and community structure. • Litter removal exerts greater effect on bacterial community than understory removal. • Soil NH 4 +-N and moisture regulate bacterial biomass under litter removal. • This work highlights different management practices in climate transitional forests. Litter and understory play important roles in maintaining structure and functions of belowground ecosystems in forests. However, how litter and understory affect soil microbial community is unclear. As part of a three-year (2016–2018) manipulative experiment, this study was designed to evaluate the effects of litter and/or understory removal on soil microbial community in a coniferous-broadleaved mixed forest of the subtropical-warm temperate transition zone in Central China. The results showed that soil moisture, NO 3 −-N, NH 4 +-N, and dissolved organic carbon were decreased under litter removal, but remained unchanged under understory removal. Total, bacteria, and actinomycetes PLFAs were significantly reduced by 11.2%, 16.3%, and 11.0% under litter removal, and by 10.1%, 13.3%, and 12.5% under understory removal, respectively. Both litter and understory removal suppressed network complexity of soil microbial community, but litter removal showed much stronger impacts on the biomass (−14.9 mg kg−1 vs. −10.9 mg kg−1) and composition (−7.77% vs. −2.89%) of bacteria (including gram-positive and gram-negative bacteria) as well as fungi to bacteria ratio than understory removal. Changes of soil NH 4 +-N and moisture might be primarily responsible for the inhibitory effects of litter removal on soil gram-positive and gram-negative bacterial biomass, respectively. Our findings highlight the contrasting responses of soil microbial community to litter and understory removal and would facilitate the mechanistic understanding of these two management practices on belowground ecology in climate transitional forests. [ABSTRACT FROM AUTHOR]