Carbon dioxide fluxes over an ancient broadleaved deciduous woodland in southern England

Abstract

Abstract.We present results from a study of canopyatmosphere fluxes of carbon dioxide from 2007 to 2009 above a site in Wytham Woods, an ancient temperate broadleaved deciduous forest in southern England. Gapfilled net ecosystem exchange (NEE) data were partitioned into gross primary productivity (GPP) and ecosystem respiration (R e ) and analysed on daily, monthly and annual timescales. Over the continuous 24 month study period annual GPP was estimated to be 21.1 Mg C ha −1 yr −1 and R e to be 19.8 Mg C ha −1 yr −1 ; net ecosystem productivity (NEP) was 1.2 Mg C ha −1 yr −1 . These estimates were compared with independent bottom-up estimates derived from net primary productivity (NPP) and flux chamber measurements recorded at a plot within the flux footprint in 2008 (GPP = 26.5 ± 6.8 Mg C ha −1 yr −1 , R e = 24.8 ± 6.8 Mg C ha −1 yr −1 , biomass increment = ∼1.7 Mg C ha −1 yr −1 ). Over the two years the difference in seasonal NEP was predominantly caused by changes in ecosystem respiration, whereas GPP remained similar for equivalent months in different years. Although solar radiation was the largest influence on daily values of CO 2 fluxes (R 2 = 0.53 for the summer months for a linear regression), variation in R e appeared to be driven by temperature. Our findings suggest that this ancient woodland site is currently a substantial sink for carbon, resulting from continued growth that is probably a legacy of past management practices abandoned over 40 years ago. Our GPP and R e values are generally higher than other broadleaved temperate deciduous woodlands and may represent the influence of the UK's maritime climate, or the particular species composition of this site. The carbon sink value of Wytham Woods Correspondence to: Y. Malhi (yadvinder.malhi@ouce.ox.ac.uk) supports the protection and management of temperate deciduous woodlands (including those managed for conservation rather than silvicultural objectives) as a strategy to mitigate atmospheric carbon dioxide increases.

Seasonal Variations of Carbon Dioxide, Water Vapor and Energy Fluxes in Tropical Indian Mangroves

“…Removal of such data caused a data gap of around 23%. There is no universal method to account for advection [33] and our method is in agreement with the several authors recording such errors using open path systems [26,32,34].…”

“…The corrected data is then gap-filled and partitioned into gross primary productivity (GPP) and ecosystem respiration (Re). The secondary data processing methodology used is similar to the proposed corrections by Thomas et al [32].…”

“…It is assumed that the extreme spikes are due to non-localized advection events or other non-stationary phenomena and not because of the natural phenomena [32].…”

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