Above-ground woody carbon sequestration measured from treerings is coherent with net ecosystem productivity at fiveeddy-covariance sites

摘要

Attempts to combine biometric and eddy-covariance (EC) quantifications of carbon allocationto different storage pools in forests have been inconsistent and variably successful in thepast. We assessed above-ground biomass changes at five long-term EC forest stations based ontree-ring width and wood density measurements, together with multiple allometric models.Measurements were validated with site-specific biomass estimates and compared with thesum of monthly CO2 fluxes between 1997 and 2009. Biometric measurements and seasonal net ecosystem productivity (NEP) proved largelycompatible and suggested that carbon sequestered between January and July is mainly usedfor volume increase, whereas that taken up between August and September supports a combinationof cell wall thickening and storage. The inter-annual variability in above-groundwoody carbon uptake was significantly linked with wood production at the sites, rangingbetween 110 and 370 g Cm~(-2) yr~(-1), thereby accounting for 10-25% of gross primary productivity(GPP), 15-32% of terrestrial ecosystem respiration (TER) and 25-80% of NEP. The observed seasonal partitioning of carbon used to support different wood formationprocesses refines our knowledge on the dynamics and magnitude of carbon allocation inforests across the major European climatic zones. It may thus contribute, for example, toimproved vegetation model parameterization and provides an enhanced framework to linktree-ring parameters with EC measurements.