Growth and maintenance respiration in stems of Pinuscontorta and Piceaengelmannii

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Abstract
Stem maintenance respiration was linearly related to live-cell volume for lodgepole pine (Pinus contorta var. latifolia Engelm.) from 4 to 36 cm dbh and for Engelmann spruce (Picea engelmannii Parry) from 0 to 20 cm dbh. Sapwood contained greater than 80% of the total live-cell volume in stems. Bole surface area, commonly used to estimate tree respiration costs, poorly estimated stem maintenance respiration. At 15.degree. C, maintenance costs for lodgepole pine were 6.6 .times. 10-5 kg C .cntdot. (kg C sapwood)-1 .cntdot. d-1. Stem respiration during the growth season, both corrected and uncorrected for maintenance, correlated well with annual stemwood growth. Annual stem maintenance respiration for trees and stands can be estimated using sapwood volume, and sapwood temperature, and knowledge of respiratory behavior. Total respiration (construction plus maintenance) estimated using stem growth and a model of maintenance respiration was compared with actual respiration measurements integrated over a 100-d growing season. Estimated respiration agreed with the integraded measurements for Englemann spruce, but overestimated the integrated measurements by 73% in lodgepole pine. These results suggest that estimates of stem respiration made during the growing season may be affected by transpiration.