Abstract: Urban forest is an important carbon sink. Soil respiration plays a crucial role in the carbon cycling of urban ecosystems. Currently, the research on forest soil respiration is mostly focused on natural forests, less is known on soil respiration of urban forest. Here, we explored the characteristics and influencing factors of soil respiration in different urban forests, including Pinus tabuliformis, Picea koraiensis, Populus alba × P. berolinensis, and Ginkgo biloba stands in Shenyang of China. Soil respiration rate, soil physical and chemical properties and enzyme activities in each stand were measured from April to October 2023. The results showed that: (1) Soil respiration rates across the four forest stands exhibited a single-peak seasonal variation, with higher values observed in summer and lower values in spring and autumn. (2) There were significant differences in soil respiration rates among the different stands (P<0.05), with the highest value being recorded under the G. biloba stand (2.82±0.19 μmol·m^-2·s^-1). (3) Soil respiration rates of the four forest stands were significantly exponentially correlated with soil temperature (P<0.001). For P. koraiensis and P. alba × P. berolinensis stands, soil respiration rates were significantly linearly correlated with soil moisture (5 cm) (P<0.01). (4) Soil respiration rate was positively correlated with the contents of soil organic matter and ammonium, the activities of sucrase, urease and polyphenol oxidase (P<0.05), while it was negatively correlated with soil pH and nitrate content (P<0.05). Hierarchical partitioning analysis indicated soil temperature was the most important factor affecting soil respiration rate. Our results can enrich the theory of terrestrial soil carbon cycle and provide a scientific basis for the construction and management of urban forests in northern regions under the context of climate change.

Key words: soil respiration, forest stand, soil physicochemical property, soil enzyme activity