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Harvard Forest REU Symposium Abstract 2010
- Title: Using Granier style thermal dissipation probes to analyze canopy-bole time lags and interspecies differences in daily sap flow patterns
- Author: Sarah F Choudhury (Harvard College (Harvard University))
- Abstract:
Limitations in xylem transport capacity have a significant impact on rates of carbon uptake by forest trees. Although trees can offset such hydraulic limitations by drawing on water stored within the stem, a reliance on stored water is thought to be incompatible with high rates of xylem transport.
We used Granier's style thermal dissipation probes to measure sap flow in oaks, maples and pines, with the goal of comparing temporal and spatial patterns of sap flow in species with markedly different xylem anatomies. By investigating time lags between the movement of water indicated by sap flow probes installed in the base of the tree and in the crown, we sought to determine if plants use water stored in their trunks to offset limitations in xylem transport capacity.
The maples and pines show a crown- bole time lag that appears to be absent in the oaks. This suggests that the lags are biological in origin, and not an artifact of the probes themselves, as has been suggested. In the pines, the canopy sap flow varied between the East and West sectors, but the bole probe showed a more symmetrical pattern, indicating integration of flow and less sectoriality .
Further study will help us understand daily patterns of water use and stomatal aperture by canopy species and thus will help elucidate how forest carbon and water exchange is affected by species composition.
- Research Category: Forest-Atmosphere Exchange; Physiological Ecology, Population Dynamics, and Species Interactions
