Soil Microbial Biomass and Extracellular Enzyme Activities: Key Regulators of Short-term Soil Respiration in

Temperate Korean Forests

Saher Amna1*, Jieun Ahn1, Gaeun Kim1, Yowhan Son1

(1Department of Environmental Science and Ecological Science Engineering, Korea University)

Abstract: Forest soil respiration is one of the most important aspects of understanding carbon cycling in terrestrial ecosystems. This study investigated the impact of various forest stands and monthly variations on soil respiration (Rs) in the urban forest of Seoul, South Korea. In May and June 2024, the Rs measurements using closed-static chambers were conducted once a month from 10 am to 2 pm in three different forest stands: deciduous Zelkova serrata (ZS), evergreen coniferous Pinus koraiensis (PK), and deciduous coniferous Metasequoia glyptostroboides (MS). Simultaneously, soil temperature and moisture were monitored. Additionally, topsoils at a depth of 0-10 cm were sampled to assess total carbon (TC) and nitrogen (TN), soil microbial biomass carbon (MBC) and nitrogen (MBN), and soil extracellular enzymes activities (EEAs) of β-glucosidase (BG), cellobiohydrolase (CBD), β-xylosidase (BX), N-acetylglucosaminidase (NAG), and leucine aminopeptidase (LAP). The mean Rs over the two months in ZS, PK, and MS were 426.46 ± 106.5 mg C m² h-¹, 161.52 ± 9.94 mg C m² h-¹, and 145.23 ± 33.34 mg C m² h-¹, respectively. Both forest stands and sampling months significantly impacted Rs (p < 0.001). The ZS showed higher Rs compared to the PK and MS. Moreover, all stands, except for the PK, had higher Rs in June compared to May (p < 0.001). Among the measured soil properties, Rs showed the strongest positive correlations with MBC, MBN, BX, CBD, and BG (R2 > 0.90; p < 0.001). These findings underscore that soil microbial activities are key regulators of Rs under different forest stands. However, a long-term study is needed to elucidate the mechanisms of seasonal variations in Rs and soil microbial activities, considering different forest stands' physiological and phenological characteristics.

Acknowledgments: This study was supported by the National Research Foundation of the Republic of Korea (NRF-2022R1A2C1011309).