关键词: 间伐, 细菌, 真菌, 微生物残体碳, 结构方程模型

Abstract:

Objective: The differences of soil physicochemical properties, enzyme activities, microbial residue carbon and their contribution to soil organic carbon (SOC) of Cunninghamia lanceolata plantation under different thinning intensities were analyzed, and a new regulation mechanism of soil physicochemical properties and enzyme activities on microbial residue carbon accumulation was revealed. It provides a scientific theoretical basis for the sustainable management of Cunninghamia lanceolata plantations, alleviating global climate change and achieving the goal of "carbon neutrality" in my country. Method: Taking the Cunninghamia lanceolata plantation in Guanzhuang state-owned forest farm in Fujian Province as the object, the soil samples of 0-10 cm and 10-20 cm in different thinning intensities (31%, 45%, 63%) were collected, and aminosugars were used as microorganisms. Markers of residues, to explore the effects of thinning intensity and soil depth on the accumulation characteristics of soil microbial residues. Result: 1) The contents of soil bacterial microbial residue carbon (MRC_B), fungal microbial residue carbon (MRC_F), and microbial residue carbon (MRC) all increased significantly with the increase of thinning The ratio of carbon to bacterial residues (MRC_F/MRC_B) decreased with the increase of thinning intensity; soil MRC_B, MRC_F, MRC, MRC_F/MRC_B decreased with the deepening of soil layer. 2) The contribution rates of soil MRC_B, MRC_F and MRC to SOC were 13.20%-18.99%, 28.42%-39.72%, and 41.62%-58.70% under different thinning intensities, and they all increased with the deepening of the soil layer. 3) In the 0-10 and 10-20 cm soil layers, SOC, total phosphorus (TP), available phosphorus (AP), microbial biomass carbon (MBC), dissolved organic carbon (DOC), nitrate nitrogen. The contents of (NO₃^?-N) and ammonium nitrogen (NH₄⁺-N) were in the order of heavy thinning > moderate thinning > weak thinning, while pH value and density decreased with the increase of thinning intensity. 4) Both thinning intensity and soil layer depth had significant or extremely significant effects on soil enzyme activity ( P<0.05). The content of polyphenol oxidase decreased first and then increased; and with the deepening of the soil layer, the activities of the four enzymes all showed a decreasing trend. 5) Structural equation modeling (SEM) analysis showed that soil chemical properties and enzyme activities were latent variables that had a greater impact on the carbon content of soil microbial residues in the 0-10 and 10-20 cm soil layers, respectively. The soil single factor that has a greater impact on the latent variable soil microbial residue carbon content is the soluble carbon (P=0.002) and ammonium nitrogen (P=0.066) content in the 0-10 cm soil layer, and the 10-20 cm soil layer is Peroxidase (P=0.002) and nitrate (P=0.034) content. Conclusion: With the increase of thinning intensity, soil physicochemical properties and enzyme activities of Cunninghamia lanceolata plantations changed significantly, and the content of soil various forms of carbon and microbial residue carbon increased continuously; the structural equation model was well fitted, and the latent variable soil microbial residue carbon content was mainly It is regulated by the latent variables of soil chemical properties (soluble carbon, ammonium nitrogen and nitrate nitrogen) and enzyme activity (peroxidase), so in Cunninghamia lanceolata plantation management, soil nutrients and enzyme activities can be improved by moderate management density , and increase the carbon content of microbial residues and their contribution to the SOC pool.

Key words: thinning, bacteria, fungi, microbial residual carbon, structural equation model