Stem/branch maintenance respiration of Japanese red pine stand

Stem/branch maintenance respiration for a stand of Japanese red pine (Pinus densiflora) during the dormant season was examined using an open flow system. The stem/branch respiration rates per unit of volume were closely related to the thickness of the stems and branches, e.g. it decreased with increasing diameter (p < 0.0001). When the respiration rates on the various positions were regressed against the stem temperature of the specific position, Q10 values decreased with increasing diameter. The variation of Q10 ranged from 1.28 to 6.4. These Q10 variations should have represented the variation of stem/branch temperature within the tree. The increase in time lag corresponded with an increase in diameter. We estimated the annual maintenance respiration for stem and branches at stand level based on the respiration rate-diameter relation, the Q10-diameter relation, and the pipe model theory. In the P. densiflora stand, total annual maintenance respiration was estimated to be 2.55 t C ha−1 year−1 (1.40 t C ha−1 year−1 for stems, and 1.15 t C ha−1 year−1 for branches). This suggests that branch respiration is an important component of total aboveground woody respiration at the stand-level (about 45%). Within the distribution of annual maintenance respiration rates for each D class, the stem and branch of 25–30 cm D class was the highest, and accounted for 33% and 31% of total stem and branch respiration rates, respectively. According to our results and those of previous studies, maintenance respiration correlated positively with annual mean temperature and LAI, and correlated negatively with stand age and latitude.