Climate‐altered fire regimes may increase extirpation risk in an upper subalpine conifer species of management concern. Issue 8 (25th August 2020)

• Record Type: Journal Article
• Authors: Pansing, Elizabeth R.; Tomback, Diana F.; Wunder, Michael B.
• Is Part Of: Ecosphere. Volume 11:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-25
• Subjects: altered fire regimes -- climate change -- Greater Yellowstone Ecosystem -- Pinus albicaulis -- population projection model -- whitebark pine -- wildfire; Ecology -- Periodicals; Ecology; Periodicals; 577.05
• DOI: 10.1002/ecs2.3220
• Languages: English
• ISSNs: 2150-8925

Abstract

Abstract: Climate change is transforming forest structure and function by altering the timing, frequency, intensity, and spatial extent of episodic disturbances. Wildland fire regimes in western U.S. coniferous forests are now characterized by longer fire seasons and greater frequency, with further changes expected. Identifying the impacts of altered fire regimes on forest resources may enable land managers to plan mitigation strategies or prepare for novel or altered communities. We created a stochastic, density‐dependent, matrix projection model for a whitebark pine ( Pinus albicaulis ) metapopulation to estimate the impacts of increasing fire frequency on metapopulation persistence. Whitebark pine is a widely distributed foundation species of management concern found in upper subalpine and tree line forests of the Northern Rocky Mountains. We parameterized the model using empirically based demographic data from the Greater Yellowstone Ecosystem (GYE) and validated the model by comparing observed whitebark pine densities to those projected by the model when parameterized with historical demographic rates and fire frequencies. We reparameterized the model with current demographic rates including mortality from insect outbreaks and exotic disease. We compared odds of functional extirpation among six scenarios comprising three altered fire frequencies (fires suppressed, historical fire return interval of 268 yr, and decreasing fire return intervals from current to 97 yr) and two seed dispersal probabilities. Historical parameterization with high dispersal probability projected median whitebark pine densities (40.95 trees/ha, first and third quartiles: 21.89, 67.25), which were similar to empirically estimated densities (40.62 trees/ha, first and third quartiles: 12.04, 114.15). Odds of functional extirpation with increasing fire frequency were 8.26 and 139.91 times higher than historical fire frequency and fire suppression, respectively. In decreasing fire return interval scenarios, odds of functional extirpation were 1.76 times higher in low than high dispersal probability scenarios. These findings suggest that fire suppression may be required to maintain whitebark pine metapopulations in the GYE and that maintaining stand networks connected by high rates of seed dispersal could increase metapopulation resiliency.