Fine root respiration in mature eastern white pine (Pinus strobus) in situ: the importance of CO(2) in controlled environments.
We measured seasonal fine root respiration rate in situ while controlling chamber temperature and [CO(2)]. Atmospheric [CO(2)] ([CO(2)](a)) and measured soil [CO(2)] ([CO(2)](s)) were alternately delivered to a cuvette containing intact fine roots of eastern white pine (Pinus strobus L.). Respiration rates were consistently higher in [CO(2)](a) than in [CO(2)](s) and were almost three times higher during midsummer. Respiration rates were immediately reversed after returning to the alternate [CO(2)] (i.e., [CO(2)](a) --> [CO(2)](s) --> [CO(2)](a), and vice versa) suggesting a direct effect of elevated [CO(2)] on apparent respiration. Soil-[CO(2)]-based respiration rates decreased with increasing [CO(2)] on a dry mass and tissue [N] basis. We conclude that estimates of soil CO(2) flux and soil carbon budgets may be improved by more completely accounting for the rhizosphere microclimate (i.e., soil temperature and [CO(2)](s)) during measurement of fine root respiration.
Clinton
Barton D.
BD
USDA Forest Service, Southern Research Station, Coweeta Hydrologic Lab, 3160 Coweeta Lab Road, Otto, NC 28763, USA.
Vose
James M.
JM