仪器的加热效应校正对生态系统碳水通量估算的影响

涡度相关技术的广泛应用为获取生态系统碳、水通量提供了可能,但在开路式涡度相关系统中,仪器的加热效应增大了观测数据的不确定性。为了衡量仪器的加热效应,以ChinaFLUX3个典型生态系统(长白山温带针阔混交林(CBS)、海北灌丛草甸(HBGC)、鼎湖山亚热带常绿阔叶林(DHS))为研究对象,就仪器的加热效应校正对碳、水通量估算的影响进行分析。结果表明:加热校正没有改变生态系统的能量闭合特征,也没有对水汽通量的估算产生影响,但显著减小了CBS和HBGC非生长季的净生态系统生产力(NEP),进而减少了NEP的年总量,对DHS没有显著影响。NEP减小幅度受到温度的强烈影响,CBS为7.7%～10.4%,远小于HBGC的76.6%～85.2%,HBGC的NEP大幅降低主要是由夜间NEP的改变导致生态系统呼吸(RE)的增大而引起。因而,在温带生态系统中,充分考虑加热校正对于准确估算生态系统的碳收支具有重要作用。

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.