DOI: 10.5061/dryad.dv41ns262
title: Context-dependent disturbance synergies: Subcortical competitors may constrain bark beetle irruption following wildfires

description: Wildfires and bark beetles have historically interacted to create complex
 and resilient forests. However, recent record-breaking wildfires in
 western North America raise concerns that the large areas of injured and
 dead trees could facilitate increases in insect populations that respond
 to resource pulses. Populations of Douglas-fir beetle (Dendroctonus
 pseudotsugae), the primary mortality agent of Douglas-fir (Pseudotsugae
 menziesii) often irrupt following fires due to the resultant ephemeral
 pulses of defensively compromised hosts. Other subcortical phloeophagous
 insects are also attracted to fire (e.g., woodboring Coleoptera:
 Buprestidae, Cerambycidae), and similarly colonize damaged trees. Although
 Douglas-fir beetle and woodboring beetle species are known to colonize the
 phloem of injured trees, the potential for interactions among them
 following fire is relatively unknown. Rapid colonization by woodborers of
 the bark beetle niche following fires could constrain bark beetle
 population growth, potentially suppressing population irruptions through
 subcortical competition. To evaluate this hypothesis, we studied three
 wildfire complexes in mature Douglas-fir forests that burned in British
 Columbia in 2017. We found Douglas-fir beetle preferentially colonized
 mature stands containing large-diameter trees with moderate fire injury,
 and that these trees were frequently co-colonized by woodborers. In the
 absence of woodborers, we found that potential rates of increase of
 Douglas-fir beetle populations (i.e., offspring per female) were
 sufficient to lead to a local population irruption. Conversely, when
 woodborers were common (&gt;50% of trees infested per stand),
 potential rates of increase of Douglas-fir beetle populations fell below
 replacement. These findings suggest that competition by woodboring beetles
 may suppress irruptions of Douglas-fir beetle in fire-injured forests. Our
 results reveal complex, context-dependent interactions among disturbance
 agents, and indicate that population irruptions by resource pulse-driven
 bark beetles following fire may depend upon the response of local
 subcortical competitors. Forest management practices that enhance the
 diversity and abundance of non-irruptive phloeophagous insects such as
 many woodboring beetle species may limit the potential for wildfires to
 contribute to subsequent bark beetle outbreaks.
description: # Context-dependent disturbance synergies: Subcortical competitors may
 constrain bark beetle irruption following wildfires
 [https://doi.org/10.5061/dryad.dv41ns262](https://doi.org/10.5061/dryad.dv41ns262) ## Description of the data and file structure These data were derived from field sampling conducted in the interior Douglas-fir forests of British Columbia by Mitchell et al., in 2019. Additional data (not shared here) was derived from the same field season and published in Kitchens* et al., 2022 ([https://doi.org/10.1016/j.foreco.2022.120203](https://doi.org/10.1016/j.foreco.2022.120203 "Persistent link using digital object identifier")).  \**Note: Kate Mitchell has previously published under her maiden name Kitchens, but this is the same researcher across both studies*  Four files have been provided and attached.  Three excel .csv files containing raw field data are named as follows, and apply to the relevant models/hypotheses which were tested in the manuscript:  **Tree Level Preference.csv** (for the testing of the tree level preference model) **Tree Level Performance.csv** (for the testing of the tree level performance model) **Plot Level All Data.csv** (for the testing of both the performance and preference plot level models) Some information across these .csv files is repeated, as all data was derived from the same field sampling season and protocols outlined in Mitchell et al., 2025 (see *Methods*). For information about individual variables and how they were collected, see *Methods*. For descriptions of variables, see tables below. Blank cells represent missing data.  One R Markdown (.rmd) file containing cleaned and summarized code pertaining to model creation and evaluation is also attached as: **Mitchell et al 2025.rmd** There is no attached readme file for the code, as all directions and relevant information are structured into the markdown file as needed. As stated in the code, if there are any questions please reach out to Kate Mitchell ([kate.a.mitchell@gov.bc.ca](mailto:kate.a.mitchell@gov.bc.ca)) and Allan Carroll ([allan.carroll@ubc.ca](mailto:allan.carroll@ubc.ca)).  ## Sharing/Access information The authors request that any additional work on these data (including but not limited to follow-up publications) be done with the permission of the Forest Insect Disturbance Ecology Lab (FIDEL) PI Allan Carroll. For permission, additional information or questions about these data, please contact [allan.carroll@ubc.ca](mailto:allan.carroll@ubc.ca). ## Variable Descriptions ###### **Plot Level All Data.csv** | Variables | Units | Description | | :------------- | :--------------- | :----------------------------------------------------------------------------------------------------------------------------------------------------------------- | | complex | categorical | Fire complex names, EH = Elephant Hill, CTA = Hanceville Riske Creek, GL = Prouton Lakes | | plot | categorical | Plot name/identifiers | | dbhallspp | cm | Diameter at breast height (dbh), calculated as average for all species | | dbhdf | cm | Diameter at breast height (dbh), plot level average for Douglas-fir (df) only | | ba | m^2/ha | basal area | | htallspp | m | plot-level average of tree height for all species | | htdf | m | plot-level average of tree height for Douglas-fir (df) only | | charallspp | proportion | plot-level average of proportion of bole char (m) as a function of total tree height (m), calculated for all species | | chardf | proportion | plot-level average of proportion of bole char (m) as a function of total tree height (m), calculated for Douglas-fir (df) only | | dfbsum | number | sum of Douglas-fir beetle (dfb) infested trees per plot | | wbsum | number | sum of woodborer (wb) infested trees per plot | | conifersum | number | sum of conifer trees per plot (all species) | | dfhostsum | number | sum of Douglas-fir (df) trees per plot | | dfprop | proportion | proportion of Douglas-fir (df) trees per plot | | dfbpropallspp | proportion | proportion of Douglas-fir beetle (dfb) attacked trees as a function of all conifer tree species per plot | | dfbprop | proportion | proportion of Douglas-fir beetle (dfb) attacked trees as a function of all Douglas-fir trees (df) per plot | | wbprop | proportion | proportion of woodborer (wb) attacked trees as a function of all conifer tree species per plot | | r | offspring/female | number of successfully emerging Douglas-fir beetle offspring per plot / number of initiating maternal gallery starts per plot. For more information see *Methods.* | | dfbdistkm | km | distance to existing Douglas-fir beetle outbreaks | | fd250mprop | proportion | proportion of Douglas-fir trees within the surrounding 250m areas of a given plot, as derived by VRI; for more information see *Methods*. | | fd250marea | proportion | total area of Douglas-fir trees within the surrounding 250m areas of a given plot, as derived by VRI; for more information see *Methods*. | | densitystemsha | stems/ha | plot-level stand density, as a function of stems per ha | cm = centimeters, m = meters, km = kilometers, ha = hectares ###### **Tree Level Preference.csv** | Variables | Units | Description | | :-------------- | :----------- | :---------------------------------------------------------------------------------------------------------------------------------------- | | complex | categorical | Fire complex names, EH = Elephant Hill, CTA = Hanceville Riske Creek, GL = Prouton Lakes | | plot | categorical | Plot name/identifiers | | Species | categorical | tree species identifier | | DBH | cm | Diameter at breast height | | avg char | proportion | proportion fire injury (m) / tree height (m) | | Tree Height | m | total tree height (m) | | wb | 0/1 | presence/absence of woodborer (wb) infestation per tree | | dfb-18 | 0/1 | presence/absence of Douglas-fir beetle (dfb) infestation per tree | | plot-ba | m^2/ha | basal area per plot | | dfprop | proportion | proportion of Douglas-fir (df) trees per plot | | wbprop | proportion | proportion of woodborer infested trees per plot | | fireweightavg | numerical | weighted average fire injury per plot | | fireunweightvar | numerical | unweighted average variation in fire injury per plot | | dfbdistkm | km | distance to existing Douglas-fir beetle outbreaks | | fd250mprop | proportion | proportion of Douglas-fir trees within the surrounding 250m areas of a given plot, as derived by VRI; for more information see *Methods*. | | fd250marea | proportion | total area of Douglas-fir trees within the surrounding 250m areas of a given plot, as derived by VRI; for more information see *Methods*. | | densitystemsha | stems per ha | plot-level stand density, as a function of stems per ha | ###### **Tree Level Performance.csv** | Variables | Units | Description | | :----------------- | :----------- | :---------------------------------------------------------------------------------------------------------------------------------------- | | complex | categorical | Fire complex names, EH = Elephant Hill, CTA = Hanceville Riske Creek, GL = Prouton Lakes | | plot | categorical | Plot name/identifiers | | treeid | categorical | tree name/identifier | | ba | m^2/ha | plot basal area | | mat\_gall\_length | cm | length of initiating maternal galleries | | imagej\_dfb\_perc | % | Perc of r-survey samples (ideally x2 per tree) occupied by Douglas-fir beetle (dfb) galleries | | wb\_pa | 0/1 | presence/absence of woodborer (wb) infestation per tree | | dfb\_pa\_18 | 0/1 | presence/absence of Douglas-fir beetle (dfb) infestation per tree | | offspring\_total | number | number of successful emerging Douglas-fir beetle offspring per tree  | | offspring\_gallery | proportion | offspring / gallery length (cm) | | rbai1 | numerical | relative basal area increment for 1 year pre-fire, see *Methods* for calculation.  | | rbai5 | numerical  | relative basal area increment for 5 years pre-fire, see *Methods* for calculation.  | | dbh | cm | Diameter at breast height per tree | | height | m | Height per tree | | char\_perc | % | Perc of bole char (m) / tree height per tree | | dfprop | proportion | proportion of Douglas-fir (df) trees per plot | | wbprop | proportion | proportion of woodborer infested trees per plot | | fireweightavg | numerical | weighted average fire injury per plot | | fireunweightvar | numerical | unweighted average variation in fire injury per plot | | dfbdistkm | km | distance to existing Douglas-fir beetle outbreaks | | fd250mprop | proportion | proportion of Douglas-fir trees within the surrounding 250m areas of a given plot, as derived by VRI; for more information see *Methods*. | | fd250marea | proportion | total area of Douglas-fir trees within the surrounding 250m areas of a given plot, as derived by VRI; for more information see *Methods*. | | densitystemsha | stems per ha | plot-level stand density, as a function of stems per ha |