Ecosystem respiration and its controlling factors in a coniferous and broad-leaved mixed forest in Dinghushan, China

Accurate estimation of ecosystem respiration (R_eco) in forest ecosystems is critical for validating terrestrial carbon models. Continuous eddy covariance measurements of R_eco were conducted in a coniferous and broad-leaved mixed forest located in Dinghushan Nature Reserve of southern China. R_eco was estimated and the controlling environmental factors were analyzed based on two years' data from 2003 to 2004. Major results included that: (1) R_eco was affected by soil temperature, soil moisture, canopy air temperature and humidity, where soil temperature at 5 cm depth was the dominant factor. (2) The exponential equation, Van't Hoff equation, Arrhenius equation and Lyold-Talor equation can be used to describe the relationship between R_eco and temperature factors with similar statistical significance, while Lyold-Talor equation was the most sensitive to the temperature index (Q₁₀). (3) The multiplicative model driven by soil temperature (T_s) and soil moisture (M_s) was more corresponsive to R_eco, which explained that there were more R_eco variations than Lyold-Talor equation, both for higher and lower M_s. However, there was no statistical difference between the two models. (4) Annually accumulated R_eco of the mixed forest in 2003 was estimated as 1100–1135.6 gC m⁻² a⁻¹ by using daytime data, which was 12%–25% higher than R_eco (921–975 gC m⁻² a⁻¹) estimated by using nighttime data. The results suggested that using daytime data to estimate R_eco can avoid the common underestimation problem caused by using eddy covariance methods. The study provides a basic method for further study on accurate estimation of net ecosystem CO₂ exchange (NEE) in the coniferous and broad-leaved mixed forest in southern China.