DOI: 10.6078/d1dt4s
title: Intermediate fire severity diversity promotes richness of forest carnivores in California

description: Aim: Fire can strongly influence ecosystem function, and human activities
 are disrupting fire activity at the global scale. Ecological theory and a
 growing body of literature suggest that a mixed severity fire regime
 promotes biodiversity in western North America. Some researchers advocate
 the use of pyrodiversity (i.e., heterogeneity in aspects of the fire
 regime such as time since fire or severity) as a conservation index to be
 maximized. Others caution against this approach arguing that the index
 oversimplifies fire-biodiversity interactions across trophic, spatial, and
 temporal scales. We evaluated the effects of several landscape-scale
 pyrodiversity indices, and their severity and time-since-fire components,
 on species richness of forest carnivores. Location: Northern California,
 United States Methods: We gathered data on fire history and
 mammal occurrence from camera trap surveys at 1,451 sites across Northern
 California public and private forestlands during 2009–2018. We used this
 data to model the effects of fire severity diversity, and its components
 (i.e., low, moderate, and high severity wildfires), on carnivore richness
 at short (10 years) and longer (25 years) timeframes. We repeated the
 modeling using a measure of time-since-fire diversity and its components
 (&lt;10 yrs, 10–20 yrs, 20–30 ys, 30–40 yrs, 40–100 yrs.). We used
 Bayesian multispecies occupancy modeling to correct for imperfect
 measurement of species richness. Results: We found that carnivore
 richness was highest at locations with intermediate fire severity
 diversity (0.46, 90%CI: 0.40–0.52) calculated using Simpson’s Measure of
 Evenness (range: 0–1) for the 10-yr timeframe, and the results were almost
 identical yet less precise for the longer timeframe. When we separated
 fire severity diversity into its components, we found that carnivore
 richness was highest at locations where 17% (90%CI: 4–20) of the landscape
 had experienced low severity burns over the past decade. In contrast, we
 found no association between time-since-fire diversity and carnivore
 richness, however, an intermediate amount of one of the components (e.g,
 the total amount of fire in the past 10 years) was positively associated
 with carnivore richness. Our results are consistent with a mixed severity
 fire regime wherein there is a greater extent of low severity than high
 severity fire. Main Conclusions: Overall our results suggest that
 carnivores would benefit from landscapes managed for greater, but not
 maximal, fire severity diversity. Our results also suggest that
 prescribed, low severity burns may provide ecological services to wildlife
 not otherwise provided by silviculture in a managed forest landscape.
description: For 2009 through 2018 we conducted wildlife surveys using camera
 traps at a total of 1,451 sites across the study area. Our annual survey
 season began in early August and continued through late November or early
 December. The duration of surveys was 2–5 weeks, and both camera traps
 within a hexagon were always surveyed concurrently. We reviewed photos
 from camera surveys to identify all mammal detections to species. We
 created a detection history for each site that indicated whether (“1”) or
 not (“0”) a species was observed for each 24-hour survey day up to 30
 days. Average survey duration was 18.7 days. We used
 the Monitoring Trends in Burn Severity (MTBS) spatial database of fire
 severity of all wildfires &gt;500 ha in the USA since 1984. To measure
 fire severity diversity, we computed Simpson’s Measure of Evenness (SME)
 of the four burn category proportions from MTBS (none, low, moderate,
 high) at both the 10-year and 25-year timeframes. We repeated a similar
 analytical process for calculating covariates pertaining to time since
 fire, although the data available allowed us to inspect a longer timeframe
 than we used for fire severity. Data were processed in
 R and are available in a .Rdata file. See the
 accompanying manuscript for a full description of methodology.
description: The .Rdata file provided comprises eight R objects:
 covars_site, a data frame containing site-level
 covariates for sampling locations. The column "site" is a unique
 ID for each site rands.out, a data frame containing
 site-level covariates for randomly selected, non-sampled sites used in
 calculating the typical conditions over the landscape
 spec_trasnl, a two-column data frame translating species codes
 into common names standards, a matrix giving the mean
 and standard deviation of the covariate data columns for use in
 back-transforming scaled covariates yday, a matrix
 giving the Julian date of each each site-sampling event
 lag, a numeric array giving the site-species-event specific
 covariate for time since last detection project, a
 binomial vector indicating which of two project protocols was used for
 each site y, the binomial array of
 detection/nondetection data. The value of y[<em>i, j, k</em>]
 indicates whether species <em>k</em> was detected on visit
 <em>j</em> to site <em>i</em>, with a 0
 representing nondetection, a 1 representing detection, and a NA indicating
 that site <em>i</em> was sampled fewer than
 <em>j</em> times. These data
 can be imported into an R session via the command
 load([filepath]).