Variability in tree transpiration across buffer and upland zones in a small headwater catchment

PARTNERS: North Carolina Forest Service; North Carolina State University; North Carolina Department of Agriculture and Consumer Services

SUMMARY: Transpiration is a key component in the water budget that is used to quantify water resource demands across large and small source water catchments. Topography and soil moisture conditions vary across headwater catchments, resulting in a range or a series of pocket transpiration responses by species in a mixed forests. The amount of water used by species at different locations within a watershed is not well captured by models and may be a contributing factor to outputs that over or under estimate water use and stream discharge at local and regional scales.

This study will quantify differences in riparian buffer, mid-slope, and upland-slope sap flux density to further refine what is understand about how location affects species-specific transpiration in a mixed pine-hardwood forest; quantify how much more water is used by the riparian buffer stand when compared to water used by the total stand; and compare and contrast site measurements to simulated stand discharge, evapotranspiration, and transpiration from the MIKE SHE hydrological model.

Quantifying tree water use in the buffer, mid-slope, and upland-slope zones across the landscape and integrating/averaging those data can improve total stand transpiration estimates. In addition, comparing those transpiration values to model outputs will be useful information to water resource managers who use these data to develop strategies and make decisions to sustain water quantity.

EFETAC's ROLE: Eastern Threat Center biological scientist Johnny Boggs leads this research project.

STATUS: Ongoing

PROGRESS: In 2015, researchers began monitoring tree water used at three sapflow stations (one in the buffer, mid-slope, and upland-slope).

Knowledge gained from monitoring transpiration conditions in the study watershed at various locations will eventually be incorporated with existing literature and models to help land managers better understand how Piedmont watersheds store, release, and discharge water across growing and dormant seasons and how to apply the most appropriate management practices for water resources, particularly during drought periods.


LINKS:

CONTACT: Johnny Boggs, Eastern Threat Center Biological Scientist, johnny.boggs@usda.gov or 919-549-4060


Updated July 2018

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