Remote sensing of ecosystem trajectories as a proxy-indicator for watershed water balance.anomalies within Boreal Plains watersheds, Alberta Canada


Ecosystem trajectories are inextricably linked to hydrology, however, water availability is not easily observed within the landscape. The response of vegetation to soil water availability may provide an indicator of local hydrology and the resilience or sensitivity of ecosystems to long-term changes in water balance. In this study, vegetation trajectories derived from Landsat Modified Soil Adjusted Vegetation Index (MSAVI) over a 22-year period are used as an indicator of spatio-temporal changes of watershed water balance and surface water storage within six proximal watersheds of the Boreal Plains ecoregion of Alberta, Canada. The interactions between hydrology, topography, geology and land cover type are examined as they relate to vegetation change.


Runoff ratio (runoff/precipitation) is greater within watersheds with greater variability of relief, compared within sub-humid, wetland-dominated watersheds (average = 0.35, 0.20, respectively), which experience lagged runoff response. The impacts of a two-year drought had a greater impact on vegetation trajectories within variable relief watersheds containing a high proportion of coarse grain surficial geology. The drought extended for an additional one to two years within three sub-humid watersheds, reducing watershed runoff to less than 50 mmper water year (November to October) in two watersheds. However, proportional area of decline of MSAVI was significantly less within these watersheds. The results of this study indicate that wetlands play an important role for local water balance and ecosystem maintenance during periods of water stress and should be considered within land use planning and reclamation strategies of the Boreal Plains.

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