Large Area Monitoring with a MODIS-based Disturbance Index (DI) Sensitive to Annual and Seasonal Variations

Disturbance of the vegetated land surface, due to factors such as fire, insect infestation, windthrow andharvesting, is a fundamental driver of the composition forested landscapes with information on disturbanceproviding critical insights into species composition, vegetation condition and structure. Long-term climatevariability is expected to lead to increases in both the magnitude and distribution of disturbances. As aconsequence it is important to develop monitoring systems to better understand these changes in theterrestrial biosphere as well to inform managers about disturbance agents more typically captured throughspecific monitoring programs (such as focused on insect, fire, or agricultural conditions). Changes in thecondition, composition and distribution pattern of vegetation can lead to changes in the spectral and thermalsignature of the land surface. Using a 6-year time series of MODerate-resolution Imaging Spectroradiometer(MODIS) Land Surface Temperature (LST) and Enhanced Vegetation Index (EVI) data we apply a previouslyproposed Disturbance Index (DI) which has been shown to be sensitive to both continuous anddiscontinuous change. Using Canada as an example area, we demonstrate the capacity of this DisturbanceIndex to monitor land dynamics over time. As expected, our results confirm a significant relationshipbetween area flagged as disturbed by the index and area burnt as estimated from other satellite sources(R2=0.78, pb0.0001). The DI also demonstrates a sensitivity to capture and depict changes related to insectinfestations. Further, on a regional basis the DI produces change information matching measured wide-areamoisture conditions (i.e., drought) and corresponding agricultural outputs. These findings indicate that formonitoring a large area, such as Canada, the time series based DI is a useful tool to aid in change detectionand national monitoring activities.