DOI: 10.5061/dryad.tdz08kq78
title: Pyrodiversity of boreal lake islands begets biodiversity of beetles, plants, and birds

description: Global fire regimes are changing, raising concerns about the ability of
 fire-prone ecosystems to maintain biodiversity. We tested whether the
 pyrodiversity-biodiversity hypothesis (i.e., variation in post-fire
 characteristics promotes biodiversity) or alternative hypotheses better
 explain patterns of biodiversity in a true island system. Using fixed-area
 sampling plots in a chronosequence of 42 boreal lake islands spanning
 gradients in island area (1-350.4 ha), isolation (0.1-7.9 km from
 mainland), and fire history (1-231+ year since fire), we tested whether
 alpha and beta diversity of beetles, plants, and birds increased with
 spatial (within-island variation in burn severity) and temporal (variation
 in time since fire among islands) pyrodiversity, respectively. Species
 richness of plants and birds increased with spatial pyrodiversity,
 indicating that habitat heterogeneity from localized variation in burn
 severity supported more species in some groups. Beta diversity of all taxa
 increased with temporal pyrodiversity, highlighting the importance of
 conserving age-class variation within the boreal patch mosaic. In
 contrast, the habitat amount hypothesis and island biogeography theory
 were weak predictors of species richness across all taxa, and island area
 and isolation did not consistently affect beta diversity among the
 islands. Our findings emphasize the importance of maintaining
 pyrodiversity in boreal landscapes to combat biodiversity loss in the age
 of “megafires” and suggest leveraging the fire refugia effects of large
 lakes within the region to conserve vital components of temporal
 pyrodiversity such as old-growth forests.
description: # Pyrodiversity of boreal lake islands begets biodiversity of beetles,
 plants, and birds https://doi.org/10.5061/dryad.tdz08kq78 These data are
 from a field experiment conducted in the Lac la Ronge Provincial Park
 region of northern Saskatchewan, Canada between 2019-2022. The experiment
 made use of 42 islands spanning gradients in time since fire, island area,
 and isolation with data collected from a single 30 x 30 m plot established
 on each island. The edge of each island plot was at least 15 meters from
 the water's edge. Information on local habitat variables as well as
 species data for beetles, plants, and birds that were collected from each
 island plot are included in the accompanying .csv and R code files. The
 .csv file `'alpha_diversity_model_selection_19islands.csv'`
 contains information that was used in the model selection analysis of our
 paper. Island refers to a unique two-digit island code for each island,
 'year.burned' is the calendar year of the most recent burn for
 each island, 'fire.stdev' is the standard deviation of
 relativized burn ratio scores for each island that was obtained from the
 burn severity rasters constructed in Google Earth Engine, and
 'fire.stdev.stand' is the standard deviation of relativized burn
 ratio scores for each island after applying a resampling procedure to
 account for differences in island size (see manuscript). The variables
 'beetle.richness', 'bird.richness', and
 'plant.richness' correspond to the number of species of these
 groups detected on each island. The variables
 'beetle.msom.richness' and 'bird.msom.richness' are
 the adjusted species richness values for beetles and birds calculated
 using multi-species occupancy models, which accounted for species-level
 variation in detection. Island area is listed under the variable
 'log10area' and was calculated as log10(area+1) to avoid
 negative values associated with small island sizes. Island isolation is
 listed under the variable 'buffer5000' as a proportion of land
 within a 5 km buffer around each island, with a value of 1 indicating an
 island is completely surrounded by water (no land). Time since fire (e.g.
 time.since.fire.beetles, time.since.fire.plants, and
 time.since.fire.birds) is the number of years between the age of the
 oldest tree at each island site and when each of the major taxa was
 sampled. The variables 'Lat' and 'Long' indicate the
 latitudinal and longitudinal coordinates (decimal degrees) for the center
 of each island plot. The variables 'buffer_1' and
 'buffer_10' refer to the habitat amount (value of 1 indicating
 an island is completely surrounded by land/habitat) for each island
 measured at scales of 1 km (birds) and 10 km (beetles/plants, see
 Supplemental Material of paper). The R code file
 `'Model_Selection_19islands_RCode.R'` contains R code that was
 used to perform our model selection analysis with the data contained in
 the .csv file 'alpha_diversity_model_selection_19islands'. This
 file also includes code that was used to calculate the p-values,
 regression coefficients, and deviance explained by the models, and to test
 for spatial autocorrelation in our models. The .csv file
 `'alpha_diversity_ALL_islands.csv'` contains the same variables
 and data descriptions as the file
 'alpha_diversity_model_selection_19islands' except that it also
 includes data for an additional 23 islands that were not included in our
 model selection analysis. The .csv files containing island species
 community data (`beetles_speciesmatrix_presenceabsence.csv`,
 `vascularplants_speciesmatrix_presenceabsence.csv`, and
 `borealbirds_speciesmatrix_presenceabsence.csv`) were used to measure beta
 diversity (jaccard's index) across gradients of time since fire,
 island area, and island isolation. The information in each community
 matrix includes data on the presence/absence for species (columns; 466
 beetle species, 101 plants species, and 54 birds species for the full set
 of 42 islands (rows). A cell value of 1 indicates presence and a value of
 0 indicates absence. Note: the files
 vascularplants_speciesmatrix_presenceabsence.csv and
 vascularplants_speciesmatrix_presenceabsence_RDA.csv have empty cells for
 the island 'BS' because this island burned before vascular plant
 surveys could be conducted. The .csv file
 `'island_isolation.csv'` contains isolation values for each
 island under the column 'buffer5000'. The values are the
 proportion of land within a 5 km buffer around each island, with a value
 of 1 indicating an island is completely surrounded by water (no land).
 This file was used to calculate pairwise differences in isolation for the
 42 islands used in our beta diversity analysis. The .csv file
 `'island_logarea.csv'` contains data on total island area for
 each island (log10(area+1) transformed). This file was used to calculate
 pairwise differences in island area for the 42 islands used in our beta
 diversity analysis. The .csv files `'time_since_fire_beetles'`,
 `'time_since_fire_plants'`, and
 `'time_since_fire_birds'` contain the column 'TSF'
 which indicates the estimated number of years. This estimate varies
 slightly across taxa and sites depending on when sampling occurred during
 our three year study. The R code file
 `'BetaDiversity_Analysis_RCode.R'` contains R code that was used
 to model pairwise dissimilarities in our species community data as a
 function of pairwise differences in time since fire (temporal
 pyrodiversity), island area, and island isolation. This code uses data
 contained in the species matrices
 ('beetles_speciesmatrix_presenceabsence.csv',
 'plants_speciesmatrix_presenceabsence.csv', and
 'birds_speciesmatrix_presenceabsence.csv') and the files used to
 construct our time since fire ('time_since_fire_beetles.csv',
 'time_since_fire_plants.csv', and
 'time_since_fire_birds.csv'), island area
 ('island_logarea.csv'), and island isolation
 ('island_isolation.csv') distance matrices. The .csv file
 `'RDA_environmental_variables.csv'` includes environmental
 variables that were used in our Redundancy Analysis (RDA) and step
 function analysis. Island refers to a unique two-digit island code for
 each island, 'plant.richness' is the total number of plant
 species detected on each island, 'log10area' is the area of each
 island (subject to a log10(area+1) transformation), 'buffer5000'
 is a measure of island isolation and reflects the proportion of land
 within a 5 km buffer around each island, with a value of 1 indicating an
 island is completely surrounded by water (no land). The variables
 'time.since.fire.beetles', 'time.since.fire.plants',
 and 'time.since.fire.birds' is the number of years between the
 age of the oldest tree at each island site and when each of the major taxa
 was sampled on each island. The variables 'charcoal.yes' and
 'charcoal.no' indicate the volume of coarse woody debris with
 and without charcoal, respectively, for each island (units in m^3^). The
 variables 'frugivore.abund' and 'insectivore.abund'
 refers to the counts of frugivorous and insectivorous birds, respectively.
 'Bird.abundance' is the total number of bird counts for each
 island. 'Basal.area' is the cross-sectional area of living and
 dead trees measured at diameter breast height within a 10 m radius of the
 center of each plot (units in m^3^). 'Beetle.catch.rate' is the
 number of beetle specimens collected on each island divided by the total
 number of trap days. The variables
 'deciduous.canopy.cover.percent.a.d' and
 'deciduous.understory.cover.percent.a.d' refers to the % cover
 of deciduous vegetation measured using the line-intercept method, where
 overstory includes stems ≥ 4 cm diameter, &gt; 2 m in height and
 understory includes stems &lt; 4 cm diameter breast height [DBH], &lt; 2 m
 in height. The variables 'conifer.canopy.cover.perecent.a.d' and
 'conifer.understory.canopy.percent.a.d' is the same as above,
 but for conifers and the 'a.d' at the end of each variable name
 indicates that the data for alive and dead vegetation was combined. The
 variable 'total.cwd.volume' (units in m^3^) refers to the total
 volume of coarse woody debris (CWD, ≥ 4 cm diameter), estimated using the
 formula: V = *π r2 h*, where r is the radius at the middle of each piece
 and *h* is the length of each piece of CWD in each island plot. The
 variables 'cwd.dc1', 'cwd.dc2', etc. are the volume of
 CWD listed by decay class (units in m^3^), with decay class 1 (i.e.,
 cwd.dc1) referring to fresh deadwood and decay class 5 being the
 most-decayed stage. The .xlsx file `'Beetle_species_list.xlsx'`
 contains the complete list of 466 beetle species (Coleoptera) sampled on
 42 lake islands (1 to 231+ years since fire) in the Lac la Ronge region
 following the nomenclature of Bousquet et al. (2013). Beetle species
 marked with an asterisk (*) indicate those that were only detected on
 either of the two islands sampled in the year immediately following fire
 (islands MI and HF, see Supplemental Table 1). References for body size
 information are listed in the Supplemental Material. The R code file
 `'RDA_analysis.R'` contains R code that was used for Redundancy
 Analysis of our species community data. This code uses data contained in
 the .csv files 'beetles_speciesmatrix_presenceabsence.csv',
 'bird_speciesmatrix_presenceabsence.csv', and
 'plant_speciesmatrix_presenceabsence_RDA.csv' (note that the
 name changed for the plant data) and the environmental data in .csv file
 'RDA_environmental_variables.csv'.