Michael Doren
Spatio-Temporal Analysis of Forest Response to Hurricane Damage in Point Pleasant Park, Halifax, Nova Scotia © 2011
Remote sensing is both a practical and affordable technology for use in the assessment and monitoring of dynamic changes within forested landscapes. In this project, we use high spatial resolution multispectral satellite imagery (QuickBird) to characterize the response of forest in Point Pleasant Park, Halifax, to damage caused by Hurricane Juan in 2003. Type and trajectory of forest response is evaluated for three time intervals (2005-2007, 2007-2009 and 2005-2009) using the normalized difference vegetation index (NDVI) as a biophysical indicator of vegetation change. A thresholding approach that combined field and other ancillary data with change vector analysis is used to separate change from no change, and to classify the magnitude of response as either moderate or large. Post-hurricane forest response followed a typical recovery path characteristic of other hurricane-disturbed forests. Moderate recovery of vegetation (mostly early successional species) was widespread and occurred in 52% of the originally damaged forest area between 2005 and 2007. The rate of response (vigour) slowed as well as retracted in spatial coverage between 2007 and 2009, only identified in 24% of the same forest area. NDVI values may have experienced saturation during the latter time interval, which could have resulted in an underestimation of the amount of actual vegetation change. Forest decline (dieback of pre-hurricane vegetation) was restricted to small areas representing less than 2% of the study area in either time interval. Physical landscape variables (slope, aspect, soil type and initial vegetation damage intensity) are investigated for correlation with forest response. Results show that slope, aspect, soil type and initial damage intensity were all influential variables governing the spatial variability of forest response between 2005 and 2007 but not between 2007 and 2009. Overall, results confirm that the type and rate of immediate forest response was highly influenced by spatial variability in initial hurricane damage intensity.