Factors influencing the persistence of a fire‐sensitive Artemisia species in a fire‐dependent ecosystem

Abstract

Fire refugia and patchiness are important to the persistence of fire-sensitive species and may facilitate biodiversity conservation in fire-dependent landscapes.Playing the role of ecosystem engineers, large herbivores alter vegetation structure and can reduce wildfire risk. However, herbivore effects on the spatial variability of fire and the persistence of fire-sensitive species are not clear. To examine the hypothesis that large herbivores support the persistence of firesensitive species through the creation of fire refugia in fire-prone landscapes, we examined the response of a fire-sensitive plant, Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis [Beetle & Young]) to fire and grazing in the fire-dependent mixed-grass prairie of the northern Great Plains. We carried out a controlled burn in 2010 within pre-established exclosures that allowed differential access to wild and domestic herbivores and no record of fire in the previous 75 years due to fire suppression efforts. The experiment was set up with a split-plot design to also examine potential changes in plots that were not burned. Canopy cover of big sagebrush was recorded before the burn in 2010 and again in 2011 with percent area burned recorded within 1-month post-fire in the burned plots. Percentage area burned was the greatest in ungulate exclosures (92% AE 2%) and the least in open areas (55% AE 21%), suggesting that large herbivores influenced fire behavior (e.g., reducing fire intensity and rate of spread) and are likely to increase fire patchiness through their alterations to the fuel bed. Regression analysis indicated that the proportion of sagebrush cover lost was significantly correlated with the proportion of area burned (R 2 = 0.76, p = 0.05). No differences in the non-burn plots were observed among grazing treatments or among years. Altogether, this illustrates the potential importance of large herbivores in creating biotic-driven fire refugia for fire-sensitive species to survive within the flammable fuel matrix of fire-dependent grassland ecosystems such as the mixed-grass prairie. Our findings also attest to the resiliency of the northern Great Plains to fire and herbivory and underscore the value of managing grasslands for heterogeneity with spatial and temporal variations in these historic disturbances.

Grazing Effects on Fuels Vary by Community State in Wyoming Big Sagebrush Steppe

“…Reductions in fine fuel biomass and continuity and increased moisture content decreased the probability of fire in intact Wyoming big sagebrush communities (Davies et al 2017; Orr et al this issue ). Grazing by livestock also creates refugia for fire-sensitive species such as sagebrush in fire-dependent ecosystems (Dornbush et al 2022). Similarly, large herbivore grazing in the tropics (Bernardi et al 2019) and savannas (Trauernicht et al 2013) decreased fire probability.…”

A novel, post‐Soviet fire disturbance regime drives bird diversity and abundance on the Eurasian steppe

“…However, this would result in a loss of >80% of the bird data. A promising approach could also be an experimental set‐up with prescribed burning and pre‐established livestock exclosures (Dornbusch et al, 2022). This would allow to test the effects of grazing and fire independently and in combination, but due to the mobility of the steppe birds, exclosures would have to be very large.…”

Mechanical and biotic reclamation strategies for a post‐mine temperate grassland

“…Tukey post‐hoc tests followed any significant analysis of variance (ANOVA) results ( p ≤ 0.10). A range of p‐values is used in ecological studies across a variety of taxa and disciplines (Dornbusch et al, 2020, 2022; Gibson, 1989; Ranellucci et al, 2012). It is critical that the significance level is specified allowing the reader to assess the balance between statistical and biological significance.…”