engleski

Inter-annual variability of CO2 exchange between pedunculate oak forest (Quercus robur L.) and the atmosphere

Water vapor and carbon dioxide are the main atmospheric constituents which are controlling the Earth’s climate. Rapid increase in atmospheric content of carbon dioxide since the beginning of industrial revolution is considered as one of the main drivers of climate changes on Earth. Only about 40% of total anthropogenic emissions of CO2 remain in the atmosphere, while the rest of emitted CO2 is stored in oceans and land. Terrestrial sink of carbon are global soils and forests. Forests sequester CO2 from the atmosphere and assimilate carbon into above- and belowground biomass and by that partially offset anthropogenic emission of CO2 and participate in a regulation of climate. Because of these findings monitoring of CO2 exchange between atmosphere and underlying forest ecosystems has gained significant importance. Micrometeorological eddy covariance method has shown like the most accurate way for direct flux measurement of trace gases and today is standard tool for estimating net ecosystem exchange (NEE) of trace gases between atmosphere and underlying surface. Within this research 10-year eddy covariance experiment (2008-2017) was carried out in young pedunculate oak (Quercus robur L.) stands (40-45 years old) which are part of the forest complex of river Kupa basin. Over the entire study period, Jastrebarsko forest acted as a carbon sink, with an average annual NEE of -268 ± 88 gC m-2 yr-1. Estimated NEE was partitioned into gross primary production (GPP) and ecosystem respiration (RECO). Furthermore, RECO was partitioned into heterotrophic (Rh) and autotrophic respiration (Ra). Most important carbon flux in forest ecosystems, net primary production (NPP), was estimated by subtracting autotrophic respiration of plants Ra from GPP. Causes of inter-annual variability of carbon NEE were investigated. Also, impact of extreme weather events (droughts and floods) on carbon fluxes was investigated. For validation of EC measurements, biometric estimate of the net primary productivity (NPPBM), which was built on periodic measurement and simple modelling, was compared with NPPEC. Comparison of NPPEC and NPPBM showed a good agreement (R2=0.46). Both estimates showed a negative trend in NPP over the study period, with a stronger decrease in NPPBM (-18.7 gC m-2 yr-2) than in NPPEC (-7.8 gC m-2 yr-2).

CO2, NEE, GPP, RECO, NPP, eddy covariance, pedunculate oak

nije evidentirano