Fire impacts on a forest obligate: western gray squirrel response to burn severity

mmerrick — Thu, 16 Apr 2020 21:22:10 +0000

Authors

Mazzamuto, Maria Vittoria

Mazzella, Maxwell N.

Merrick, Melissa J.

Koprowski, John L.

In the southwestern United States, climate change and climate–fire dynamics are affecting the distribution of natural and managed ecosystems. Forest obligate species on sky islands can experience a restriction in range with the increase of destructive forest fires. Using presence/absence data collected by hair tubes, we identified key habitat features that determine the western gray squirrel (Sciurus griseus) distribution on the sky island of the San Bernardino Mountains (California, USA) and determined post-fire differential use of burn severity in a landscape modified by fire. Gray squirrel presence was related to habitat features important for this species’ ecology and behavior, especially those associated with mature forests. The species was detected in areas with a high percentage of conifers that provide both an important food resource and good branches and cavities for nest sites. Gray squirrels occurred in all burn severities but occurred more in low and high severity sites than unburned sites. These results suggest that the gray squirrel can persist after a wildfire and can take advantage of the post-fire habitat structure if a mosaic of burn severities is maintained in the forest.

Additional Information

Mammalian Biology

Date of publication:

2020

Topics

hair tube

conifers

San Bernardino Mountains

Sciurus griseus

sky island

Research Categories

Disturbance Ecology Natural History Sky Islands Spatial Ecology

Response to fire by a forest specialist in isolated montane forest

mmerrick — Thu, 16 Apr 2020 21:10:54 +0000

Authors

Mazzella, Maxwell N.

Koprowski, John L.

Fire events have increased in scale and severity due to hotter, drier conditions brought on by climate change and fire suppression. Extreme fire events can be detrimental to forest specialists, especially populations at the edge of the species range, where conditions can vary from those within the core of the range. The San Bernardino flying squirrel (Glaucomys oregonensis californicus) is the southernmost subspecies of Humboldt’s flying squirrel and occurs only in the San Bernardino Mountains of southern California after apparent extirpation from the nearby San Jacinto Mountains. We used non-invasive methods to assess how fire affects flying squirrel occupancy. We surveyed for flying squirrels in burned and unburned areas of the San Bernardino Mountains, and measured habitat features to construct occupancy models. Our top models indicated that flying squirrels occupy lower burn severities but could still occur at higher burn severities if canopy cover remained intact, forest duff remained deep, and tree mortality remained low, especially on steeper slopes. Our study illustrates the ability of San Bernardino flying squirrels, and the potential for other flying squirrels, to survive major fire events and maintain their role in the forest ecosystem. Such results are especially important for species management and understanding how parts of an ecosystem can react as fire frequency and severity increases.