Freeze/thaw transitions in boreal forests using imaging radar: early BOREAS results
McDonald K, Way J, Zimmermann R, Rignot E. 1995. Freeze/thaw transitions in boreal forests using imaging radar: early BOREAS results. Bulletin of the Ecological Society of America. 76(3):363
Measurements of the length of the growing season may improve current estimates of net annual CO2 flux in the boreal regions. For coniferous forest species, the summer frost free period bounds the growing season length. Based on imaging radar measurements collected in Alaska, freezing results in a significant change in radar backscatter. In addressing the usc of radar data for estimating growing season length, there are two questions to be addressed. First, the relationship between canopy, bole and soil freezing and photosynthetic activity must be ascertained. Secondly, the sensitivity of imaging radar to freeze/thaw processes must be assessed. In particular, is radar sensitive to canopy or soil freezing, or both? To address these questions, in situ soil, stem and root temperatures, and stem xylem flux were measured over a complete annual cycle in 1994 at the BOREAS test sites in Canada. ERS-1 satellite radar data were also acquired throughout 1994. The temperature and xylem flux data show a clear transition in soil and stem thawing and start of growing season. This information has been correlated with the ERS-1 data in which freeze/thaw transitions show clear changes in radar backscatter. The implications on annual CO2 flux will be discussed.
- Type
- Journal Article
- Authors
- McDonald, Kyle; Way, JoBea; Zimmermann, Reiner; Rignot, Eric
- Units
- DENA
- Keywords
- Boreal, BOREAS, Forest, Forestry, freeze, IAR, Radar, thaw, Transition