Post-Wildfire Regeneration in a Sky-Island Mixed- Conifer Ecosystem of the North American Great Basin

Mackenzie Kilpatrick,Franco Biondi

doi:10.3390/f11090900

Mackenzie Kilpatrick, Franco Biondi

Open Access

https://doi.org/10.3390/f11090900

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Abstract

Information on wildfire impacts and ecosystem responses is relatively sparse in the Great Basin of North America, where subalpine ecosystems are generally dominated by five-needle pines. We analyzed existing vegetation, with an emphasis on regeneration following the year 2000 Phillips Ranch Fire, at a sky-island site in the Snake Range of eastern Nevada. Our main objective was to compare bristlecone pine (Pinus longaeva; PILO) post-fire establishment and survival to that of the co-occurring dominant conifers limber pine (Pinus flexilis; PIFL) and Engelmann spruce (Picea engelmannii; PIEN) in connection with site characteristics. Field data were collected in 40 circular 0.1 ha plots (17.8 m radius) randomly located using GIS so that half of them were inside (“burned”) and half were outside (“unburned”) the 2000 fire boundary. While evidence of previous burns was also found, we focused on impacts from the Phillips Ranch Fire. Mean total basal area, including live and dead stems, was not significantly different between plots inside the burn and plots outside the fire perimeter, but the live basal area was significantly less in the former than in the latter. Wildfire impacts did not limit regeneration, and indeed bristlecone seedlings and saplings were more abundant in plots inside the 2000 fire perimeter than in those outside of it. PILO regeneration, especially saplings, was more abundant than PIFL and PCEN combined, indicating that PILO can competitively regenerate under modern climatic conditions. Surviving PILO regeneration in burned plots was also taller than that of PIFL. By contrast, PCEN was nearly absent in the plots that had been impacted by fire. Additional research should explicitly address how climatic changes and disturbance processes may interact in shaping future vegetation dynamics.

Highlights

Wildfire shapes ecosystems through multiple interacting pathways, including their species composition, nutrient cycling, and spatial structure [1,2]
PCEN was nearly absent in the plots that had been impacted by fire
Our results indicate that wildfire impacts did not limit Pinus longaeva (PILO) regeneration, and bristlecone seedlings and saplings were more abundant in plots inside the fire perimeter than in those outside of it, but not to a statistically significant level

Summary

Introduction

Wildfire shapes ecosystems through multiple interacting pathways, including their species composition, nutrient cycling, and spatial structure [1,2]. In the western United States the role of fire varies spatially and temporally [6]. In the southwestern United States, prior to Euro-American settlement, frequent low-severity fires thinned understory vegetation in ponderosa pine forests [7], while in the upper montane and subalpine zone of the Rocky Mountains stand-replacing wildfires occurred at century-long intervals and left distinct cohorts of regeneration on the landscape [8]. Among western US ecoregions, the Great Basin stands out for its extreme topographical complexity, overall dryness, and steep orographic gradients [9], which result in sky-island montane and subalpine forests mostly dominated by conifer species [10].

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