Look for complete geospatial metadata in this layer's associated xml document available from the download link


* Metric Name: Time Since Last Disturbance  

* Tier: 2  

* Data Vintage: 2021  

* Unit Of Measure: Years  

* Metric Definition and Relevance: The metric for time since disturbance ("tsd") was measured as time in years before 2021 since the most recent disturbance of at least 25% canopy cover loss per 30m pixel as defined by eDaRT Mortality Magnitude Index (MMI) layers. MMI values less than 25% were not considered. 

The most recent disturbance class ("dist_class") of the most recent
disturbance of 25% magnitude or greater detected by eDaRT and were prioritized
in the order: fire (1), treatment (2), eDaRT (3). For example, if a pixel
intersected a fire perimeter and a treatment polygon, that pixel would be
assigned a code of 1 (fire) rather than 2 (treatment). Note that while the
occurrence of and magnitude of a disturbance was determined using eDaRT,
disturbance class was determined first using fire perimeters and FACTS
activities, with remaining eDaRT disturbances collectively assigned to insect-
and disease-related tree mortality. This data layer currently exists only for
the Sierra Nevada region.

  

* Creation Method: Layers representing time since disturbance, most recent disturbance magnitude, and most recent disturbance class were produced using the Ecosystem Disturbance and Recovery Tracker (eDaRT), Forest Activities ([FACTS](https://data.fs.usda.gov/nrm/briefingpapers/FACTS.pdf)) and CAL FIRE Timber Harvesting Plan ([THP](https://www.fire.ca.gov/programs/resource-management/forest-practice/timber-harvesting/timber-harvesting-plan-thp/)) databases, and the CAL FIRE Fire and Resource Assessment Program ([FRAP](https://frap.fire.ca.gov/mapping/gis-data/)) fire perimeter dataset. All layers are complete for the entire area within the 300s and 400s eDaRT scenes as well as for scenes 103, 105, and 501. The reference year was set to 2021 since fire history and eDaRT only reported up through 2020. The earliest year assessed was 2010 since eDaRT data prior to 2010 was used for model training and is not reliable.  

* Credits: Caden Chamberlain, Environmental and Forest Sciences, University of Washington \--University of Washington