Instrument heating correction effect on estimation of ecosystem carbon and water fluxes

Eddy covariance is widely applied in obtaining ecosystem carbon and water fluxes. However, in open-path eddy covariance system, the instrument may heat up the environment, and introduce uncertainties into the data. To scale the instrument heating effect, three typical ecosystems in ChinaFLUX, i.e., Changbaishan temperate mixed forest (CBS), Haibei shrub meadow (HBGC), and Dinghushan subtropical evergreen broad-leaved forest (DHS), were selected, and the instrument heating correction effect on the estimation of the carbon and water fluxes was analyzed. Instrument heating correction had no significant effect on the ecosystem energy balance closure and water flux, but decreased the net ecosystem production (NEP) of CBS and HBGC during their non-growth season significantly, and led to a decrease in the annual sum NEP of the two ecosystems. However, no evidence was observed that heating correction affected the NEP of DHS. The decrement of NEP was strongly affected by annual mean air temperature. In CBS ecosystem, the NEP decreased by 7.7%-10.4%, much lower than that (76.6%-85.2%) in HBGC ecosystem. The significant decrease of NEP in HBGC ecosystem could be due to the remarkable change in NEP during night, which in return could increase the ecosystem’s respiration (RE). Therefore, it would be necessary to fully consider the effect of instrument heating correction on the accurate estimation of carbon budget in temperate ecosystems.