Effects of soil temperature on the carbon exchange of taiga seedlings.: I. Root respiration

Abstract

Seedlings of Alnuscrispa (Ait.) Pursh, Populusbalsamifera L., Populustremuloides Michx., and Betulapapyrifera Marsh., hardwood species of the taiga of interior Alaska, were grown in sand in a controlled environment room at day–night temperatures of 25 and 20 °C, respectively, with a 20-h day length. After establishment, pots containing each species were placed under soil-temperature treatments of 5, 15, and 25 °C while maintaining extant air-temperature and light regimes. Both total and maintenance respiration of the roots were measured under these temperature treatments by monitoring the efflux of CO2 from the potted soil mass. An estimate of root-growth respiration was calculated as the difference between total and maintenance respiration. Total root respiration increased from three- to five-fold as soil temperature increased over the 20 °C experimental range. Growth-respiration response was species specific, occurring only at 5 °C soil temperature in A. crispa, at both 15 and 25 °C in P. balsamifera, and at all three soil temperatures in P. tremuloides. Growth respiration of the roots was a nearly constant fraction of total root respiration within a species, averaging 0.17 mg CO2•h−1•g root dry weight−1 in A. crispa and P. balsamifera, but nearly twice that, 0.33 mg CO2•h−1•g root dry weight−1, in P. tremuloides. Growth respiration was not determined for B. papyrifera.