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

Accurate estimation of ecosystem respiration (Reco) in forest ecosystems is critical for validating terrestrial carbon models. Continuous eddy covariance measurements of Reco were conducted in a coniferous and broad-leaved mixed forest located in Dinghushan Nature Reserve of southern China. Reco was estimated and the controlling environmental factors were analyzed based on two years' data from 2003 to 2004. Major results included that: (1) Reco 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 Reco 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 (Ts) and soil moisture (Ms) was more corresponsive to Reco, which explained that there were more Reco variations than Lyold-Talor equation, both for higher and lower Ms. However, there was no statistical difference between the two models. (4) Annually accumulated Reco 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 Reco (921–975 gC m−2 a−1) estimated by using nighttime data. The results suggested that using daytime data to estimate Reco 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.