Analysis of remotely-sensed vegetation conditions during droughts and a mountain pine beetle outbreak, Gearhart Mountain Wilderness, Oregon

This data release includes data-processing scripts, data products, and associated metadata for a remote-sensing based approach to characterize vegetation conditions within a dry, mixed conifer forest study area in southern Oregon in 2001 (a single year drought without any widespread insect mortality) and 2009 (during a multi-year drought that coincided with a severe outbreak of mountain pine beetle; MPB). This analysis involved several steps. First, time-series climate data were compiled and plotted to identify drought periods. Similarly, time-series data representing insect outbreaks were compiled and plotted to identify trends in insect mortality. The study area was classified into forest canopy types using existing modeled estimates of tree basal area by tree species. Using remotely-sensed Normalized Difference Moisture Index (NDMI) from the Landsat archive, NDMI anomalies from reference conditions were calculated in 2001 and 2009. Based on these anomalies, and using the forest classification map, refugia from drought (in 2001) and combined drought-MPB effects (in 2009) were identified as NDMI anomalies greater than the 90th-percentile value within each forest type. Once refugia had been identified, landscape variables (topographic, soil, and forest stand characteristics) were compiled and used to model the landscape controls on refugia locations using Boosted Regression Tree (BRT) modeling, a machine-learning algorithm. For detailed descriptions of data-release components, please consult the appropriate metadata documents that accompany the processing scripts and data products.