Relating coarse root respiration to root diameter in clonal Eucalyptus stands in the Republic of the Congo
Claire Marsden (1, 2, 3), Yann Nouvellon (1, 2) and Daniel Epron (4)
1. CIRAD, UPR-80, Campus de Baillarguet TA 10/C, 34398 Montpellier cedex 5, France / 2. UR2PI, BP 1291, Pointe Noire, Republic of the Congo / 3. Corresponding author () / 4. Nancy University, UMR INRA UHP 1137 Ecologie et Ecophysiologie Forestière, Université Henri Poincaré Nancy 1, Faculté des
Sciences, BP 239, 54506 Vandoeuvre les Nancy cedex, France / Received November 13, 2007; accepted March 14, 2008; published online June 2, 2008
Summary
Root respiration is an important component of the carbon balance of a forest ecosystem. We measured CO2 efflux of excised fine roots and intact coarse roots in 3-, 4- and 13-year-old Eucalyptus stands in the region of Pointe-Noire, Republic of the Congo. A transportable and adaptable closed chamber gas exchange system
directly measured CO2 efflux of roots from 0.5 to 32 mm in diameter. Fluxes were corrected for measurement system leaks and normalized to a reference
temperature of 30 °C. Mean fine root respiration rates at the reference temperature varied between 8.5 and 10.8 μmol CO2 kg–1 s–1 depending on the stand. Coarse root respiration was strongly negatively correlated to root diameter. We propose a model based
on a radial gradient of respiratory activity within the root to simulate the exponential decrease in respiration with diameter.
Although many sources of uncertainty in the measurements remain, as discussed in this paper, these results provide a basis
for scaling up organ-level root respiration measurements to the tree and stand levels.
Keywords:
closed chamber gas exchange system, direct measurements, root CO2 efflux.
