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* Metric Name: Shrublands with Low natural regeneration potential post-fire in southern California  

* Tier: 2  

* Data Vintage: 2020  

* Unit Of Measure: Binary. 1 = shrub pixel has low regeneration potential post-fire, 0 = shrub pixel has potential to regenerate post-fire (based on decision rules).  

* Metric Definition and Relevance: Identifying locations where shrubland vegetation will not recover naturally post-fire is a challenge given the vast areas that are regularly burned in southern California. When shrublands are within the historic fire return interval, e.g., 55 years for low-elevation shrubland, biomass accumulates and shrub cover recovers after 10–14 years. However, in many parts of southern California, the fire return interval has decreased, often in conjunction with an increase in non-native plant species, drought, and nitrogen deposition. Under these conditions, post-fire biomass recovery can be impeded and, in some cases, may result in type conversion from native shrubland to non-native grassland. Researchers developed a repeatable method to identify areas of low regeneration potential in southern California using fire history data and applying two thresholds guided by the published literature. Low regeneration pixels either had a ‘number of fires in the last 40 years’ of three or more fires, or the ‘time since last fire’ was <10 years. Researchers identified pixels that met these criteria as having low natural regeneration potential post-fire and, as a consequence, these areas could represent candidate areas for post-fire restoration in shrublands. 

The spatial extent of these data cover 6,441,208 ha and is defined by the 42
Level IV Ecoregions (Bailey 2016) that intersect the four southern US
Department of Agriculture (USDA) National Forests in southern California
(Angeles, Cleveland, Los Padres, and San Bernardino):

  

* Creation Method: Researchers obtained the historical wildfire perimeter database from the California Department of Forestry and Fire Protection (FRAP 2021). They then generated from this database a set of binary rasters indicating the occurrence of fire in a pixel for a given year across the southern California study area. The years for this input data stack range from 1967 to 2020. Researchers implemented a script to calculate the low natural regeneration potential rasters.. Two binary rasters were created for each year, one with the number of fires that burned in the last 40 years and one with the number of fires in the last 10 years. These inputs were then used to create a raster depicting low shrub regeneration potential for any given year, defined as 3 or more fires in 40 years or 1 or more fires in the last 10 years (see Dryad publication for more details).  

* Credits: Underwood, E.C. and A. D. Hollander. 2023. Areas of low natural regeneration potential post-fire in shrublands of southern California (selected years between 2008 and 2020) [Dataset]. Dryad.  See Underwood and Hollander 2023 for rasters for the other 8 years