Abstract: Research on the sensitivity of carbon isotope composition (δ¹³C) dynamics to temperature (Q₁₀) and its influencing factors in the process of ecosystem respiration (Re) can accurately predict the trend for ecosystem carbon release with global warming for assessing ecosystem carbon sequestration capacity. We used stable isotope techniques to monitor canopy CO₂ concentration and δ¹³C in a cold-temperate Larix gmelinii forest in Northeast China. δ¹³C values were also analyzed in plant and soil samples across five stand types. The sensitivity of δ¹³C dynamics to temperature during Re and the main factors affecting the variation in Q₁₀ values were determined. Carbon isotope composition of ecosystem respiration (δ¹³C_Re), autotrophic respiration (δ¹³C_Ra), and heterotrophic respiration (δ¹³C_Rh) decreased with increase in temperature, and δ¹³C_Ra < δ¹³C_Re < δ¹³C_Rh. The contribution of Ra and Rh to Re were 51.57 and 48.42%, respectively. Temperature and precipitation had inhibitory effects on Q₁₀, whereas soil organic carbon and total nitrogen had stimulatory effects. Autotrophic respiration is the dominant pathway for carbon release in this ecosystem. Heterotrophic respiration, and particularly maintenance respiration, are more temperature-sensitive. Rising temperatures and precipitation reduce the δ¹³C sensitivity to temperature.

Key words: Ecosystem respiration, Autotrophic respiration, Heterotrophic respiration, Carbon isotopes, Temperature sensitivity, Larix gmelinii