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* Metric Name: Distribution of obligate resprouting, obligate seeding, and facultative seeding shrub species  

* Tier: 2  

* Data Vintage: 2011  

* Unit Of Measure: Percentage of life history/post-fire regeneration type per pixel (0 – 100)  

* Metric Definition and Relevance: This dataset consists of 5 raster files of the proportion of above ground live biomass in these vegetation type categories: (1) Shrub obligate resprouting; (2) Shrub obligate seeding; (3) Shrub facultative seeding; (4) Tree; and (5) Herb. 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):

Mediterranean-climate region (MCR) shrublands have evolved a set of
regeneration strategies in response to periodic, high-intensity wildfires:
obligate seeding (OS), obligate resprouting (OR), and facultative seeding (FS)
species. Spatial variation is seen in different regeneration strategies. In
California, previous studies have found a higher abundance of OR species in
mesic environments and OS species in xeric environments).

Analyzing the spatial rasters depicting OS-, OR- or FS- dominated pixels,
researchers found dramatically different spatial patterns between the three
shrub regeneration strategies. FS species covered the greatest spatial
distribution, accounting for 3,372,125 ha (71%) of shrub dominated pixels in
the study area: the FS group covered a range of productivity gradients and
vegetation types, although it was notably absent from high elevation areas. In
contrast, OS-dominated pixels covered the smallest spatial area (21,899 ha, 5%
of shrub dominated pixels) occurring throughout the study area from coastal
Big Sur and the Santa Ynez Mountains on the Los Padres National Forest to
interior locations including the eastern fringes of the San Jacinto mountains
(desert shrub vegetation) in the south. Finally, pixels dominated by OR
species covered a similarly small area, 25,075 ha (5% of shrub dominated
pixels in the study area), showing aggregations in the San Bernardino and San
Gorgonio Mountains on the San Bernardino National Forest; San Gabriel
Mountains on the Angeles National Forest, and throughout higher elevations on
the Los Padres National Forest. OR-dominated pixels were notably absent in
lower elevation areas with low water availability, as indicated in the
relationship with climatic water deficit and solar radiation. The proportion
of each post-fire shrub regeneration type is critical for a number of reasons,
including assessing the ability of shrublands to recover from multiple, short-
interval fires or helping to prioritize areas for post-fire restoration.

  

* Creation Method: Researchers developed a multinomial model using temporally dynamic and static variables to predict the distribution of the three shrub post-fire regeneration strategies - obligate seeders (OS), facultative seeders (FS), obligate resprouters (OR), plus trees and herbs, in southern California. Researchers used 222 USDA Forest Service Forest Inventory and Analysis (FIA) plots and 17 predictor variables including: median 2001-2020 NDVI and biomass, vegetation type, precipitation, slope, aspect, and soil characteristics. Each predictor variable was available as a raster dataset to which the model was applied to produce the 5 raster files which estimate the proportion (percentage) of biomass within each of the five groups. Overall, model cross-validation showed the accuracy achieved 50% of predicted value within 8 to 24 percent of the actual value, with prediction accuracy highest for herb biomass and lowest for OR. Of the three shrub regeneration strategies, OS biomass was predicted with the highest accuracy and narrowest environmental range.

The files are named as follows:

SoCal_ObResprouters_pp_v1.tif = percentage of obligate resprouter biomass per
pixel.

SoCal_ObSeeders_pp_v1.tif = percentage of obligate seeder biomass per pixel.

SoCal_FacSeeders_pp_v1.tif = percentage of facultative seeder biomass per
pixel.

SoCal_Tree_pp_v1.tif = percentage of tree biomass per pixel.

SoCal_Herb_pp_v1.tif = percentage of herb biomass per pixel.

  

* Credits: Underwood, E.C., Q.M. Sorenson, C.C. Schrader-Patton, N.A. Molinari and H.D. Safford. 2023. Resprouting, seeding, and facultative seeding shrub species in California’s Mediterranean-type climate region. _Frontiers in Ecology and Evolution_ 11:1158265. doi: 10.3389/fevo.2023.1158265 Underwood, E.C.; Q.M. Sorenson, C.C. Schrader-Patton (2023). Obligate resprouting, obligate seeding, and facultative seeding shrub species in California’s Mediterranean-type climate region [Dataset]. Dryad.