© 2006 Heron Publishing—Victoria, Canada
In vivo and in situ rhizosphere respiration in Acer saccharum and Betula alleghaniensis seedlings grown in contrasting light regimes
Sylvain Delagrange (1, 2, 3), Frédéric Huc (2), Christian Messier (1), Pierre Dizengremel (4) and Erwin Dreyer (2)
1. Groupe de Recherche en Ecologie Forestière inter-universitaire (GREFi), Université du Québec À Montréal, C.P. 8888, Succ.
Centre ville, Montréal, Québec, Canada, H3P 3P8 / 2. UMR 1137 INRA–UHP Ecologie et écophysiologie forestières, Equipe Bioclimatologie Ecophysiologie Phytoécologie, 54280 Champenoux,
France / 3. Corresponding author (delagrange.sylvain@courrier.uqam.ca) / 4. UMR 1137 INRA–UHP Ecologie et écophysiologie forestières, Equipe Ecophysiologie cellulaire et moléculaire, 54500 Vandoeuvre-Les-Nancy,
France / Received February 15, 2005; accepted August 15, 2005; published online April 3, 2006
Summary
A perfusive method combined with an open-system carbon dioxide measurement system was used to assess rhizosphere respiration
of Acer saccharum Marsh. (sugar maple) and Betula alleghaniensis Britton (yellow birch) seedlings grown in 8-l pots filled with coarse sand. We compared in vivo and in situ rhizosphere respiration
between species, among light regimes (40, 17 and 6% of full daylight) and at different times during the day. To compute specific
rhizosphere respiration, temperature corrections were made with either species-specific coefficients (Q10) based on the observed change in respiration rate between 15 and 21 °C or an arbitrarily assigned Q10 of 2. Estimated, species-specific Q10 values were 3.0 and 3.4 for A. saccharum and B. alleghaniensis, respectively, and did not vary with light regime. Using either method of temperature correction, specific rhizosphere respiration
did not differ either between A. saccharum and B. alleghaniensis, or among light regimes except in A. saccharum at 6% of full daylight. At this irradiance, seedlings were smaller than in the other light treatments, with a larger fine
root fraction of total root dry mass, resulting in higher respiration rates. Specific rhizosphere respiration was significantly
higher during the afternoon than at other times of day when temperature-corrected on the basis of an arbitrary Q10 of 2, suggesting the possibility of diurnal variation in a temperature-independent component of rhizosphere respiration.
Keywords:
circadian variations, fine roots, open gas chamber, Q
10, root, sugar maple, temperature, yellow birch.
