PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Stem respiration in a secondary northern hardwood forest in Japan.

Utsugi, Hajime^*,1, Liang, Naishen³, Watanabe, Tsutomu², Abe, Shin¹, Tobita, Hiroyuki¹, Maruyama, Yutaka¹, ¹ Hokkaido Research Center, Forestry and Forest Products Research Institute, Sapporo, Hokkaido, Japan³ CGER, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan² Forestry and Forest products Research Institute, Tsukuba, Ibaraki, Japan

ABSTRACT- We measured stem respiration rate of three hardwood species in a secondary northern hardwood forest in Japan. The study site was mixed and un-even aged forest. The canopy over-story is ,Betula platyphylla var. japonica, Quercus mongolica, Kalopanax septemlobus, Populus maximowiczii and Tilia japonica, in order of decreasing predominance. The former three species occupied 85% of forest biomass. We measured the stem respiration, diameter increments and stem temperature for B. platyphylla, Q. mongolica and K. septemlobus at four heights of positions (2, 5, 8 and 18m in height). The chamber for measurement of stem respiration by closed system completely encircles a segment of stem. The chamber length along the bole ranges from 20 to 80 cm, and chamber volume ranges from 8 to 25 liters according to the bole size. We verified the accuracy of this system with LI-6400-09 soil CO₂ flux measurement system. The result of the regression analysis showed that a same value of stem respiration was obtained by both methods. In all species, stem diameter increased in growing season (from July to August). We assumed that dormancy of tree growth have started from September. Stem respiration rate per stem surface area at 15C° in July (1.2;micromolm^-2s^-1) was larger than that in the dormant season (0.6). Q₁₀ in dormant season (2.4) was larger than that in growing season (1.7). Comparing tree species, stem respiration in K. septemlobus was larger than B. platyphylla and Q. mongolica, but Q₁₀ in each species was not different at growing or dormant seasons. The tree-top respiration rate of all species was largest in the stem at growing season. The vertical difference in Q₁₀ in each species was not clear. For all data pooled, respiration rate at 15C° correlated with annual stem growth rate on a stem surface area basis in not only growing season but also dormant season.

Key words: Stem respiration, Hard wood forest, Q₁₀, Seasonal change