HOME     SCHEDULE     AUTHOR INDEX     SUBJECT INDEX              

PARENT SESSION

Effects of Sap Flow and Wood Respiratory Activity on CO2 Efflux from Stems of Mature Dacrydium cupressinum Trees in a Temperate Rainforest in New Zealand.

Bowman, William *,1, Barbour, Margaret 2, Turnbull, Matthew3, Tissue, David 4, Whitehead, David2, Griffin, Kevin 5, 1 Columbia University, New York, NY, USA2 Landcare Research, Lincoln, New Zealand3 University of Canterbury, Christchurch, New Zealand4 Texas Tech University, Lubbock, TX, USA5 Columbia University, Palisades, NY, USA

ABSTRACT- Measurements of CO2 efflux from stems and branches, sap velocity, and respiratory activity of excised wood cores were conducted in Dacrydium cupressinum trees that differed in diameter, age, and canopy emergence. The objective of this study was to determine if consistent linkages exist between respiratory production of CO2 within stems, xylem transport of CO2, and the rate of CO2 diffusing from stem surfaces. Stem CO2 efflux was depressed during periods of sap flow compared to the efflux rate expected for a given stem temperature and was positively correlated with sapwood density. In contrast, no significant relationships were observed between CO2 efflux and the respiratory activity of wood tissues. Between 86 and 91% of woody tissue respiration diffuses to the atmosphere over a 24 h period. However, xylem transport and internal storage of CO2 can significantly influence stem CO2 efflux at certain times of the day and may account for up to 17-39% and 11-16%, respectively, of woody tissue respiration. These results demonstrate that differences in sap flow rates and xylem anatomy are critically important for explaining within- and between-tree variation in CO2 efflux from stems.

Key words: Stem Respiration, CO2 Efflux, Dacrydium cupressinum, Sapwood

All materials copyright The Ecological Society of America (ESA), and may not be used without written permission.