Stem respiration and carbon dioxide efflux of young Populus deltoides trees in relation to temperature and xylem carbon dioxide concentration

Abstract

Oxidative respiration is strongly temperature driven. However, in woody stems, efflux of CO(2) to the atmosphere (E (A)), commonly used to estimate the rate of respiration (R (S)), and stem temperature (T (st)) have often been poorly correlated, which we hypothesized was due to transport of respired CO(2) in xylem sap, especially under high rates of sap flow (f (s)). To test this, we measured E (A), T (st), f (s) and xylem sap CO(2) concentrations ([CO(2)*]) in 3-year-old Populus deltoides trees under different weather conditions (sunny and rainy days) in autumn. We also calculated R (S) by mass balance as the sum of both outward and internal CO(2) fluxes and hypothesized that R (S) would correlate better with T (st) than E (A). We found that E (A) sometimes correlated well with T (st), but not on sunny mornings and afternoons or on rainy days. When the temperature effect on E (A) was accounted for, a clear positive relationship between E (A) and xylem [CO(2)*] was found. [CO(2)*] varied diurnally and increased substantially at night and during periods of rain. Changes in [CO(2)*] were related to changes in f (s) but not T (st). We conclude that changes in both respiration and internal CO(2) transport altered E (A). The dominant component flux of R (S) was E (A). However, on a 24-h basis, the internal transport flux represented 9-18% and 3-7% of R (S) on sunny and rainy days, respectively, indicating that the contribution of stem respiration to forest C balance may be larger than previously estimated based on E (A) measurements. Unexpectedly, the relationship between R (S) and T (st) was sometimes weak in two of the three trees. We conclude that in addition to temperature, other factors such as water deficits or substrate availability exert control on the rate of stem respiration so that simple temperature functions are not sufficient to predict stem respiration.

Dynamics of temperature normalized stem CO₂ efflux in Norway spruce stand

“…Similarly strong correlation was observed also in other studies (e.g. Zha et al, 2004;Saveyn et al, 2008). That infers that stem temperature is a main factor driving CO 2 effl ux from stems.…”

“…Maier and Clinton, 2006;Teskey and McGuire, 2005) the relationship between CO 2 effl ux and CO 2 concentration in xylem was observed. Saveyn et al (2008) observed a signifi cant increase in stem CO 2 concentration during rain. He explained that as a result of an increase in cell respiration and stopping sap fl ow which would transport the CO 2 off .…”

Carbon flux to woody tissues in a beech/spruce forest during summer and in response to chronic O<sub>3</sub> exposure

“…Stem CO 2 efflux was based on the volume (V in m 3 ) of the stem sector behind the chamber (i.e. living tissue of bark and sapwood) and coarse root CO 2 efflux on the totally enclosed coarse root volume, respectively (Desrochers et al, 2002;Saveyn et al, 2008). …”

Transporte y reciclaje de CO2 en el interior del árbol: factores que complican la estimación de la respiración leñosa a través de la emisión radial de CO2

“…Por ejemplo, en el trabajo de McGuire y Teskey (2004), la albura de Platanus occidentalis exhibía un flujo axial en las horas centrales del día en que la transpiración era máxima muy superior al registrado durante 24 h (103 mmol CO 2 m -3 s -1 ), es decir un 71 % de la respiración estimada a partir del balance de masa entre el flujo axial, radial y de almacenamiento del CO 2 . Igualmente, Saveyn et al (2008) observaron que el flujo axial en Populus deltoides Bartr. ex Marsh.…”