Research and Publications
View article.
The wide geographic distribution of several common haplotypes almost completely restricted to montane habitats suggests that dominant lineages in montane populations may possess adaptive syndromes that are preserved through reduced outcrossing rates or negative selection on outcrossed progeny. However, conclusive evidence of such local adaptation requires reciprocal seeding experiments and further characterization of adaptive traits and breeding system characteristics. Other lineages have likely risen to dominance in montane populations through selectively neutral processes.
View article.
Among sites with low-to-moderate tree cover, burning largely eliminated differences in understory composition, suggesting that biotic legacies were sufficient to result in predictable trajectories. In contrast, sites with high pre-fire tree cover transitioned into an annual forb-dominated community with sparse vegetation cover, suggesting that the loss of the understory community initiated unpredictable and divergent post-fire trajectories. Because plant communities were still changing four years after fire, it is unclear whether the alternate trajectories in sites with high tree cover will result in the formation of alternate states, or whether community composition will eventually converge with other sites at the same elevation. Results indicate that careful evaluation of site characteristics can be used to predict treatment outcomes at the woodland-shrubland interface, and to guide the appropriate use of prescribed fire or other management practices.
View article.
Results show that loss of perennial herbaceous species, which can result from inappropriate livestock grazing, and loss of shrubs, which often results from fire, interact to affect key functional groups. The implications are that ecosystem resilience to disturbance in Cold Desert shrublands decreases when competition from perennial native grasses and forbs for available resources no longer prevents dominance by A. tridentata and other shrubs and/ or annual invasive grasses. Managing livestock grazing to maintain or increase perennial herbaceous species, especially deep-rooted grasses, which contribute to resilience along elevation gradients, can help prevent threshold crossings to undesirable states and retain critical ecosystem services following disturbances such as wildfire.
View report.
In this report, guidelines are presented for restoring whitebark pine under future climates using the rangewide restoration strategy structure. The information to create the guidelines came from two sources: (1) a comprehensive review of the literature and (2) a modeling experiment that simulated various climate change, management, and fire exclusion scenarios. The general guidelines presented here are to be used with the rangewide strategy to address climate change impacts for planning, designing, implementing, and evaluating fine-scale restoration activities for whitebark pine by public land management agencies.
View article.
This study investigated the relative importance of site productivity and seasonal climate in explaining the variance in recovery time for 36 fires, comprising a fire chrono-sequence (from 1971 to 2007) for the Great Basin and Colorado Plateau. A. t. vaseyana recovery was positively related to precipitation in the cool season immediately following fire, likely because deep soil-water recharge that persists throughout the growing season enhances first-year seedling survival. Percentage sand fraction positively correlated with recovery rate yet negatively correlated with live cover in unburnt stands. Our data support the hypothesis that post-fire recovery rate of A. t. vaseyana depends on the climatically controlled ephemerality of the regeneration niche, as is likely true for many arid-land shrub species.
View research brief.
This study examined bark beetle mortality for two-years after fuel reduction treatment in mid-elevation mixed conifer forests at the University of California Blodgett Research Forest. As part of the National Fire and Fire Surrogate Study, the experimental treatments included prescribed fire (fire), mastication, the combination of the two, and a control.
View report.
This study found that:
- Few changes in most of the measured masticated fuel bed properties were detected over the 10 years represented in the sample. This indicates that in dry environments, it may take at least 10 years for ecological processes to change fuel characteristics enough for adverse fire effects to be mitigated.
- Burning masticated fuel beds in a laboratory revealed that there is a great deal of heat that is pulsed into the soil that could cause major mortality to belowground systems. This is especially true in high loading fuel beds with duff layers present.
- All masticated fuel beds dried to equilibrium in less than seven days, indication that these quickly drying fuels can be readily susceptible to smoldering combustion after 5-7 days of drying.
- Existing fuel models (including 11, SB1, SB2 and two existing custom fuel models) were good at representing fire behavior, indicating that there is no need to develop new, custom fuel models for masticated fuel beds.
View article.
The burnout time for upstream shrubs increased with an increase in shrub separation distance for all shrub sizes and wind speeds considered. The burnout time for the downstream shrub was found to decrease with an increase in the separation distance, reach a minimum, and then increase with an increase in separation distance. The trends observed in burnout times for downstream shrub were attributed to the balance between heat feedback into the downstream shrub from the flames in upstream shrubs and availability of sufficient oxygen for combustion to take place.
View article.
The significant variables for the fatal injury model were fire shelter use, slope steepness and flame height. The separation distances needed to ensure no more than a 1 or 5% probability of fatal injury, without the use of a fire shelter, for slopes less than 25% were 20 to 50 m for flame heights less than 10 m, and 1 to 4 times the flame height for flames taller than 10 m. The non-fatal injury model significant variables were fire shelter use, vehicle use and fuel type. At the 1 and 5% probability thresholds for a non-fatal injury, without the use of a fire shelter, the separation distances were 1 to 2, 6 to 7, and 12 to 16 times greater than the current safety zone guideline (i.e. 4 times the flame height) for timber, brush and grass fuel types respectively.
View research brief.
Fire is a strong driver of changes in montane forest structure in California’s Sierra Nevada and southern Cascade mountain ranges, which provide much of the snowpack and associated water storage for the state of California. A recent study by Stevens presented one of the first direct investigations in California of how fire can influence snowpack depth.