Evaluating the effects of alternative landscape management scenarios on three old-forest-associated predators over 100 years in the fire-prone forests of the Sierra Nevada, USA

Developing and implementing landscape-scale management strategies capable of balancing the need for restoring natural fire regimes and promoting ecosystem resiliency for future climate change remains an urgent need globally. To help guide development of a landscape management strategy capable of meeting multiple objectives, five alternative landscape management scenarios for reducing the risk of uncharacteristically severe wildfire using thinning or managed and prescribed wildfire were developed by local forest managers in the Lake Tahoe region of the Sierra Nevada mountains. Effects of each scenario on forest structure, composition, and wildfire behavior were simulated over a 100-year period using the dynamic landscape simulation model LANDIS-II. We developed empirical territory occurrence models for three old-forest-associated predators, using 22 California Spotted Owl, 28 Northern Goshawk, and 16 female Pacific marten territories and presence-only modeling to evaluate the effects of each management scenario. The recruitment of more old-forest habitat across the simulated landscape was a more significant factor than any differences in the management scenarios, resulting in increases in the numbers of territories for all three predators, regardless of scenario. Increases in the numbers of territories were slowed in Scenario 4, which had the greatest amount of thinning, but the positive trend continued decades beyond when the other scenarios began to show a decline in territory numbers from severe wildfire. However, increases in the numbers of territories over time were slowed and overall were the lowest for the two old-forest predators that were most sensitive to the amount of old forest at the territory scale in the scenario with the greatest pace and scale of treatments. This suggests a trade-off between slowing the increase in the numbers of territories in the short term from forest growth by using fuels treatments with increased pace and scale to create forest structure that is less susceptible to severe wildfire in the long term, and that these management scenarios may need to be re-evaluated in 50 years before committing to continuing management efforts that may ultimately become detrimental for old-forest predators within 100 years.