Recovery after fire
In sagebrush-dominated shrublands of western North America, warmer temperatures coupled with annual grass invasions are increasing the frequency and extent of wildfires. Postfire sagebrush recovery rates are unpredictable and many recent fires have resulted in the apparent loss of sagebrush habitat, resulting in a pressing need to identify management strategies that can promote post-fire sagebrush recovery. Major investments in post-fire seeding treatments have resulted in limited restoration success, and observational results suggest that successful post-fire sagebrush establishment requires favorable weather conditions coincident with the short period of seed viability. Repeating seeding treatments in multiple consecutive years has been suggested as potentially improving restoration success through bet-hedging, increasing the probability that seed availability will coincide with favorable weather conditions. However, this approach has not been tested for sagebrush, and delayed seeding treatment success may also be constrained by competition from other plants establishing after fire.
In this study, we studied natural big sagebrush regeneration patterns in small burns without seed constraints, allowing us to separate the influence of climate and seed availability on post-fire establishment and providing a natural analog to repeated seeding applications. We combined dendrochronological methods, repeated vegetation surveys, and detailed soil environmental measurements from a regional network of experimental prescribed fires to examine the temporal patterns of post-fire big sagebrush establishment along regional climatic gradients. Temporal and spatial patterns of sagebrush establishment were modeled as a function of both annual weather and site-level climate means.
Post-fire sagebrush establishment patterns showed highly episodic establishment, with most sites experiencing pulses of establishment in years in which soils stayed wet for longer. Given favorable soil environmental conditions, establishment probability remained high for up to a decade after fire, suggesting that competition with other established plants is not a major constraint to post-fire sagebrush establishment for some time after fire. Although drier/warmer sites were less likely to have favorable conditions for sagebrush establishment in a given year, all sites appeared to be on track for relatively rapid recovery to pre-burn levels of sagebrush canopy cover, regardless of the frequency of establishment events. These results suggest that, in the interior of larger fires where sagebrush recovery is expected to be limited by a lack of viable seeds, the window of opportunity for restoration efforts such as post-fire seeding or planting may be longer than previously thought. This is an especially important insight for burns in drier portions of the landscape, where there is a lower probability that ephemeral periods of seed availability will coincide with favorable weather conditions to result in successful sagebrush establishment. In those locations, an adaptive management approach that includes the option of repeated seeding will likely increase the probability of sagebrush recovery.
This research has been presented in five scientific and public presentations, and a manuscript and a non-technical summary article on the findings presented in this report are currently in preparation. Once completed, we will distribute these publications through the JFSP Great Basin Fire Science Exchange.