In vivo and in situ rhizosphère respiration in Acer saccharum and Betula alleghaniensis seedlings grown in contrasting light regimes
2006
Delagrange , Sylvain (INRA (France). UMR 1137 Ecologie et Ecophysiologie Forestières) | Huc , Frédéric (INRA (France). UMR 1137 Ecologie et Ecophysiologie Forestières) | Messier , Christian (Université du Québec(Canada). Groupe de Recherche en Ecologie Forestière inter-universitaire (GREFi)) | Dizengremel , Pierre (INRA (France). UMR 1137 Ecologie et Ecophysiologie Forestières) | Dreyer , Erwin (INRA (France). UMR 1137 Ecologie et Ecophysiologie Forestières)
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 Ur, own in 8-1 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 (Q(10)) based on the observed change in respiration rate between 15 and 21 degrees C or an arbitrarily assigned Q(10) of 2. Estimated, species-specific Q(10) 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 Q(10) of 2, suggesting the possibility of diurnal variation in a temperature-independent component of rhizosphere respiration.
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