Fine root respiration in mature eastern white pine (Pinus strobus) in situ: the importance of CO2 in controlled environments.
Clinton and Vose measured seasonal fine root respiration rate in situ while controlling chamber temperature and [CO2]. Atmospheric and [CO2] ([CO2]a) and measured soil [CO2] ([CO2]s) were alternately delivered to a cuvette containing intact fine roots of eastern white pine (Pinus strobus L.). Respiration rates were consistently higher in [CO2] [CO2]a than in [CO2]s, and were almost three times higher during midsummer. Respiration rates were immediately reversed after returning to the alternate [CO2] (i.e., [CO2]a ® [CO2]s ® [CO2]a, and vice versa) suggesting a direct effect of elevated [CO2] on apparent respiration. Soil[CO2] -based respiration rates decreased with increasing [CO2] on a dry mass and tissue [N] basis. The authors conclude that estimates of soil CO2 flux and soil carbon budgets may be improved by more completely accounting for the rhizosphere microclimate (i.e., soil temperature and [CO2]s) during measurement of fine root respiration.