The use of forest stand age information in an atmospheric CO2 inversion applied to North America

[摘要] Atmospheric inversions have become an important tool in quantifying carbondioxide (CO₂) sinks and sources at a variety of spatiotemporal scales,but associated large uncertainties restrain the inversion research communityfrom reaching agreement on many important subjects. We enhanced anatmospheric inversion of the CO₂ flux for North America by introducingspatially explicit information on forest stand age for US and Canada as anadditional constraint, since forest carbon dynamics are closely related totime since disturbance. To use stand age information in the inversion, weconverted stand age into an age factor, and included the covariances betweensubcontinental regions in the inversion based on the similarity of the agefactors. Our inversion results show that, considering age factors, regionswith recently disturbed or old forests are often nudged towards carbonsources, while regions with middle-aged productive forests are shiftedtowards sinks. This conforms to stand age effects observed in flux networks.At the subcontinental level, our inverted carbon fluxes agree well withcontinuous estimates of net ecosystem carbon exchange (NEE) upscaled fromeddy covariance flux data based on MODIS data. Inverted fluxes with theage constraint exhibit stronger correlation to these upscaled NEE estimatesthan those inverted without the age constraint. While the carbon flux at thecontinental and subcontinental scales is predominantly determined byatmospheric CO₂ observations, the age constraint is shown to havepotential to improve the inversion of the carbon flux distribution amongsubcontinental regions, especially for regions lacking atmospheric CO₂observations.

[学科分类] 地球化学与岩石