Abstract: Aims In recent years, fires triggered by extreme weather have caused severe damage to forest ecosystems, leading to a sharp increase in tree mortality. Non-structural carbohydrates (NSC) can reflect the response of plants to post-fire environmental changes and their adaptive strategies. However, there are currently few studies on the changing patterns and response mechanisms of NSC concentrations in different plant organs with time since fire. Methods In the Huzhong area of the Da Hinggan Mountains, four severely burned plots with different burn times and one adjacent unburned plot were selected using the "space instead of time" method. The local dominant shrub species, Vaccinium vitis-idaea, was used as the research object, and the leaves and branches of different ages (current year and perennial), fine roots and rhizosphere soil samples were collected to determine the soluble sugar and starch concentrations of each organ, functional traits of leaves and fine roots, and the soil properties. Important findings The order of NSC concentrations in different organs of V. vitis-idaea was leaves > branches > fine roots. The soluble sugar concentration of current year leaves increased significantly after fire, whereas the starch concentration of perennial leaves increased significantly. The starch concentration of the current year branches was significantly higher than that of perennial branches from 2 to 10 years after fire. The NSC concentrations of branches and fine roots 18 years after fire were still significantly different from those without fire. In addition, leaf NSC concentration was negatively correlated with soil pH, leaf specific area and leaf nitrogen content; branch NSC concentration was positively correlated with time since fire and soil available phosphorus content, and negatively correlated with fine root nitrogen content; fine root NSC concentration was positively correlated with time since fire and negatively correlated with fine root nitrogen content. In conclusion, the response of V. vitis-idaea leaf-branch-fine root NSC concentrations to time since fire showed significant organ variability, which is of great significance for accurately understanding the physiological and ecological changes of plants during post fire recovery.

Key words: Forest fire disturbance, Leaf age, Soluble sugar, Soil properties, Plant traits