DOI: 10.5061/dryad.h01d6sq
title: Data from: Corralling a black swan: natural range of variation in a forest landscape driven by rare, extreme events

description: The natural range of variation (NRV) is an important reference for
 ecosystem management, but has been scarcely quantified for forest
 landscapes driven by infrequent, severe disturbances. Extreme events such
 as large, stand-replacing wildfires at multi-century intervals are typical
 for these regimes; however, data on their characteristics are inherently
 scarce, and, for land management, these events are commonly considered too
 large and unpredictable to integrate into planning efforts (the proverbial
 ‘Black Swan’). Here, we estimate the NRV of late-seral (mature/old-growth)
 and early-seral (post-disturbance, pre-canopy-closure) conditions in a
 forest landscape driven by episodic, large stand-replacing wildfires: the
 Western Cascade Range of Washington, USA (2.7 million ha). These two seral
 stages are focal points for conservation and restoration objectives in
 many regions. Using a state-and-transition simulation approach
 incorporating uncertainty, we assess the degree to which NRV estimates
 differ under a broad range of literature-derived inputs regarding: a)
 overall fire rotations, and b) how fire area is distributed through time –
 as relatively frequent smaller events (less episodic), or fewer but larger
 events (more episodic). All combinations of literature-derived fire
 rotations and temporal distributions (i.e. ‘scenarios’) indicate that the
 largest wildfire events (or episodes) burned up to 10^5-10^6 hectares.
 Under most scenarios, wildfire dynamics produced 5th-95th percentile
 ranges for late-seral forests of ~47-90% of the region (median 70%), with
 structurally complex early-seral conditions composing ~1-30% (median 6%).
 Fire rotation was the main determinant of NRV, but temporal distribution
 was also important, with more episodic (temporally clustered) fire
 yielding wider NRV. In smaller landscapes (20,000 ha; typical of
 conservation reserves and management districts), ranges were 0-100%
 because fires commonly exceeded the landscape size. Current conditions are
 outside the estimated NRV, with the majority of the region instead covered
 by dense mid-seral forests (i.e. a regional landscape with no historical
 analog). Broad consistency in NRV estimates among widely varied fire
 regime parameters suggests these ranges are likely relevant even under
 changing climatic conditions, both historical and future. These results
 indicate management-relevant NRV estimates can be derived for seral stages
 of interest in extreme-event landscapes, even when incorporating inherent
 uncertainties in disturbance regimes.
description: README for
 State-and-transition simulation models and output The included models and
 output are associated with “Corralling a black swan: Natural range of
 variation in a forest landscape driven by rare, extreme events” by Daniel
 C. Donato, Joshua S. Halofsky, and Matthew J. Reilly. Please see README
 file for further details.   
 Models
 Within the
 'Models' folder are the 27 STSIM models run across the entire
 2.7 million ha landscape, and the nine STSMs run at the 20,000 ha scale.
 The models span all beta distributions, snychronies, and rotations used in
 the analysis. All models were run using the STSim package in the SyncroSim
 software (version 2.0.33). Both the package and software are freely
 available to download from https://syncrosim.com.   
 Output
 Landscape Within the
 'Output_Landscape' folder is the raw csv output for each of the
 27 landscape scenarios. Each scenario has a state output and a transition
 output containing annual values for each of our 50 simulations where each
 simulation was run for 10,000 years. State files were used to develop all
 structure-related summaries. Transition files were used to estimate all
 wildfire-related summaries. Output_Landscape.7z
 
 Output Twenty
 Thousand Hectares 'Output_Twenty_Thousand_Hectares' contains the raw csv output from the nine 20,000 ha scale scenarios. Each scenario has a state output and a transition output containing annual values for each of our 50 simulations where each simulation was run for 10,000 years. State files were used to develop all structure-related summaries. Transition files were used to estimate all wildfire-related summaries. Output_Twenty_Thousand_Hectares.7z