ALBERT

Description:    Stem CO 2 efflux ( E S ) is an important component of forest ecosystem carbon budgets and net ecosystem CO 2 exchange, but little is known about E S in temperate forests in Northeastern China, an area with a large extent of forest. We measured E S along with stem temperature at 1 cm depth ( T s) over a 9 month period in 2007 on ten dominant tree species of secondary forests of the region. Other measurements included the autotrophic component of soil CO 2 efflux ( E A ) and stem diameter at breast height (DBH). Our objectives were to (1) examine the seasonal patterns and species differences in E S , and (2) determine the correlations between E S and T s, DBH and E A . Mean E S for the measurement period ranged from 1.09 to 1.74 μmol CO 2  m −2  s −1 among the ten species. The sensitivity of E S to T s ( Q 10 ) ranged from 1.87 to 2.61. Across the ten species 57–89% of variation in E S was explained by T S and DBH. There was also a linear relationship between mean E S and E A . E S was better predicted by T s in the dormant season than the growing season, indicating that additional factors such as growth respiration and internal transport of CO 2 in the xylem became more important contributors to E S during the growing season. Stem CO 2 efflux increased, and Q 10 decreased, with increasing DBH in all species. Although temperature exerts strong control on the rate of cellular respiration, we conclude that in tree stems in situ, T S , DBH and many other factors affect the relationship between CO 2 evolution by respiring cells and the diffusion of CO 2 to the stem surface. Content Type Journal Article Category Original Paper Pages 1-11 DOI 10.1007/s00468-012-0698-3 Authors J. Y. Yang, Center for Ecological Research, Northeast Forestry University, Harbin, 150040 China R. O. Teskey, Warnell School of Forestry and Natural Resources, University of Georgia, Athens, 30602 USA C. K. Wang, Center for Ecological Research, Northeast Forestry University, Harbin, 150040 China Journal Trees - Structure and Function Online ISSN 1432-2285 Print ISSN 0931-1890