Studies of historical fire and vegetation conditions in dry conifer forests have demonstrated a high degree of heterogeneity across landscapes. However, there is a limit to the amount of inference that can be drawn from historical fire reconstructions. Contemporary-reference‖ landscapes may be able to provide information that is not available from historical reconstructions. In this study, we characterized variability in vegetation structure and composition across two Sierra Nevada landscapes with long-established fire restoration programs. We used tree, shrub, and surface fuel data from 117 initial plots, 86 of which were remeasured 8-12 years later, to identify the mechanisms driving variability in vegetation and fuel conditions. Our analyses identified nine distinct vegetation groups, with mean live tree basal area and density ranging from 0.3 to 72.7 m 2 ha-1 and 2.5 to 620 trees ha-1 for individual groups. For all plots combined, mean live tree basal area and density was 28.4 m 2 ha-1 and 215 trees ha-1 , but standard deviations (SD) were 29.1 m 2 ha-1 and 182 trees ha-1 , respectively. These ranges and SDs demonstrate considerable variability in vegetation structure, which was partially related to site productivity and previous fire severity. Fine surface fuel loads were generally low (overall mean, 16.1 Mg ha-1), but also exhibited high variability (SD, 12.6 Mg ha-1). Surprisingly, surface fuel loads based on initial measurement and change between measurements were not related to fire characteristics. The only statistical relationship found was that surface fuel loads were associated with forest structure and composition. These results capture a contemporary ‗natural' range of variability and can be used to guide landscape-level restoration efforts. More specifically, these results can help identify distinct targets for variable forest structures across landscapes.

Fuel hazard reduction treatments such as prescribed fire and mastication are widely used to reduce fuel hazard. These treatments help protect people from wildfire, yet may not be mutually beneficial for people and ecosystems in areas adapted to infrequent crown fire. Short-term studies indicate that some fuel hazard reduction treatments can be detrimental to biodiversity and ecosystem function, suggesting that land managers face an acute dilemma between protecting people or ecosystems. However, the long-term ecological trajectories and fuel hazard outcomes of fuel treatments are poorly understood. Using a 13-year replicated experimental study, we evaluated how shrub cover, non-native species abundance, native species diversity, and an obligate seeder responded to fuel treatments in California's northern chaparral. The fuel hazard reduction treatments (fire and mastication) and their seasons of implementation (fall, winter, and spring) had unique influences RESUMENLos tratamientos de reducción de combustibles como las quemas prescriptas y el triturado son ampliamente usados para reducir el peligro potencial de incendios. Estos tratamientos ayudan a proteger a la gente de los incendios, aunque pueden no ser mutuamente beneficiosos para la gente y los ecosistemas en áreas adaptadas a incendios de copa poco frecuentes. Estudios de corto plazo indican que los tratamientos de reducción de combustible pueden ser perjudiciales para la biodiversidad y el funcionamiento de los ecosistemas, sugiriendo que los gestores del territorio se enfrentan al dilema de tener que optar entre proteger a la gente o a los ecosistemas. Por otra parte, las trayectorias ecológicas y los resultados finales sobre el peligro de incendios por parte de los tratamientos de combustibles a largo plazo son aún poco entendidos. Usando un estudio experimental replicado durante 13 años, evaluamos como la cobertura de arbustos, la abundancia de especies no nativas, la diversidad de especies nativas y una especie que se reproduce obligadamente por semillas, responden a distintos tratamientos de reducción de combustible en el chaparral del norte de California. Los tratamientos de reducción de combustible (quemas prescriptas y triturado) y las estaciones en que fueron implementados (otoño, invierno, y primavera) tuvieron influencias únicas on plant communities. Untreated controls had continuous shrub canopy with no understory throughout the study. Recovery of shrubs after mastication was slower than recovery after fire. Ten years after treatment, shrub cover in fire treatments and spring mastications produced 1 % to 2 % less cover than the control, whereas fall mastications produced 8 % less cover than the control. The number of non-native plants, including non-native annual grasses, was higher after mastication treatments compared to fire treatments after 10 years. Surprisingly, mastication treatments also increased cover of an uncommon native shrub that is an obligate seeder. The season of treatment also influenced these outcomes, but to a lesser...

No abstract

Chaparral is an important fire-dominated plant community within the California Floristic Province, which covers about seven percent of California. Typically during a fire, heat immediately acts on Adenostoma fasciculatum (Chamise) seeds/m 2 in the soil seed bank. Smoke also reaches seeds on and near the soil surface. Chemical effects of fire, such as smoke and charcoal, are deposited on the soil surface and leach into the seed bank after fall rains. In nature, this results in enhanced germination of the seeds and the beginning of chaparral post-fire succession. Fire effects, both heat and chemical, have been supported to increase seed germination in numerous laboratory and field studies. I sought to utilize natural fire cues, such as heat, charate, and liquid smoke, to develop successful and efficient restoration prescriptions. The most successful restoration technique developed utilized Wright's Liquid Smoke and heat to increase seed germination of Adenostoma fasciculatum (Chamise), Ceanothus cuneatus (California lilac), and Salvia mellifera (Black Sage) significantly. A new restoration prescription for RCQ based on literature reviews and the above mentioned research is presented.