Samantha Karpyshin | ALES Graduate Seminar

Date(s) - 19/09/2019
8:30 am - 9:30 am
150 South Academic Building (SAB), South Academic Building, University of Alberta, Edmonton AB

A graduate exam seminar is a presentation of the student’s final research project for their degree.  This is an ALES MSc Final Exam Seminar by Samantha Karpyshin.  This seminar is open to the general public to attend.

Thesis Topic :

Transpiration Response of Residual Lodgepole pine after Partial-cut and Strip-shelterwood Harvesting in Alberta’s Southern Rocky Mountains

Seminar Abstract:

Forest harvesting reduces forest canopy cover which can reduce evapotranspiration and affect the hydrologic regime of watersheds. Prior research has shown while transpiration is reduced by the removal of trees, it can also affect soil moisture and meteorological variables (e.g. temperature, wind, RH) governing water use of un-harvested residual trees. While this may increase transpiration of residual trees after harvesting, this has not been documented in older mature forests that would typically be harvested. Thus, the net affect of harvesting on total transpiration in harvested watersheds remains unclear. This study explores the transpiration response of mature (> 50 years) lodgepole pine (Pinus contorta) where transpiration, soil moisture, and meteorological conditions were evaluated for two growing seasons after partial-cut (PC) and strip-shelterwood (SC) harvesting. While transpiration was greatest during the moister, early growing season compared to the drier, late season in all stands, transpiration was 60 % greater in residual trees in the PC stand and ~ 40 % greater in the SC stand compared to the reference (un-harvested) stand. Atmospheric moisture demand increased by ~ 10 %, while the shallow soil moisture storage increased by ~ 50 % in the SC stand and in the deeper soil layers by 40 % in the PC stand compared to the reference stand. Spatial patterns in transpiration strongly mirrored the spatial and temporal patterns in these above-ground (atmospheric moisture demand) and below-ground (soil moisture) controls regulating transpiration after harvesting. When changes in post-harvest transpiration rates were scaled up to larger spatial scales, results suggest that increased transpiration by residual trees may compensate for the reduction of transpiration by trees removed during harvesting. This is an important finding, as area harvested may not serve as a direct proxy indicator of potential hydrologic change.

MSc with Dr. Uldis Silins and Dr. Miles Dyck

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