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Live fuel moisture, an important determinant of fire danger in Mediterranean ecosystems, exhibits seasonal changes in response to soil water availability. Both drought stress indices based on meteorological data and remote sensing indices based on vegetation water absorption can be used to monitor live fuel moisture. In this study, a cumulative water balance index (CWBI) for a time series spanning 1994–1997 and 1999–2001 was compared to field measured live fuel moisture and to equivalent water thickness (EWT) calculated from remote sensing data. A sigmoidal function was used to model the...

Understanding the trade~offs between short-term and long-term consequences\r\nof fire impacts on ecosystems is needed before a comprehensive fuels\r\nmanagement program can be implemented nationally. We are evaluating 3\r\npotential trade-off models at 8 locations in major U.S. fuel types, We present results of the initial testing of the 3 selected models/modelling approaches and a 4th model on the Bitterroot National Forest (BNF) in western Montana. The selected models/modelling approaches were 1) the Fire Emissions Trade-off Model (FETM), 2) sequential use of the SIMPPLLE and MAGIS...

With a rich diversity of aquatic habitats, including deep lakes, shallow ponds, and rushing streams, Dusy Basin in Sequoia-Kings Canyon National Parks typifies the high Sierra ecosystem where mountain yellow-legged frogs usually thrive. Yet throughout the Sierra, aquatic ecologist Kathleen Matthews found entire water basins empty of these amphibians. Comprehensive studies showed that exotic trout caused the precipitous decline.

The Willow (Empidonax traillii) and Pacific-slope (E. dificilis) flycatchers are generally similar in their morphology and foraging, but differ in their habitat and population dynamics. Through a concentration of constant-effort mist-netting stations, we documented the movements and composition of populations over a relatively large geographical province of southern Oregon and northern California. Although the Pacific-slope Flycatcher is far more common as a breeding species in much of the province, it becomes much less common than the Willow Flycatcher during migration. After breeding,...

We studied the distribution and abundance of drifting embryonic and larval fishes and lampreys in the Smith and Van Duzen rivers of northern California, U.S.A. We collected seven fish species in four families and at least one lamprey species in the drift. All taxa drifted almost exclusively at night. Sculpins, Cottus aleuticus and C. asper, outnumbered all other taxa, comprising 63% of the catch in the Van Duzen River and 90% of the catch in the Smith River. We estimated that sculpin drift reached 3 × 107 individuals h−1 during the relatively high flow period from late winter through early...

We report the characterization of a member of the auxin-induced IAA gene family from zinnia, designated zIAA8, which is expressed by mesophyll cells differentiating as tracheary elements in vitro. Transcription of zIAA8 is upregulated within 3 h after cell isolation in inductive medium, indicating that cells perceive and respond to growth factor stimulus early in culture. Transcript levels of zIAA8 remain high through 72 h of culture in medium containing auxin and cytokinin or auxin alone, but low in medium containing only cytokinin or control medium lacking growth factors, demonstrating...

This report summarizes findings from the regional and county socioeconomic assessment conducted for southern California. The 26-county region extends from San Diego to the San Francisco Bay Area. A majority of the state’s population resides within this region, which surrounds the four southern California National Forests (Angeles, Cleveland, Los Padres, and San Bernardino). Regional and county descriptions, including histories, population sociodemographics and projections, and quality of life indicators are examined. The information is of use to natural resource and area planners concerned...

Mast-fruiting or masting behavior is the cumulative result of the reproductive patterns of individuals within a population and thus involves components of individual variability, between-individual synchrony, and endogenous cycles of temporal autocorrelation. Extending prior work by Herrera, we explore the interrelationships of these components using data on individual seed production in 59 populations of plants from 24 species spanning a large range of annual variability, from species exhibiting strong masting to others with little annual variability in seed production. Estimates of...

Mountain rivers in particular are prone to sediment input in the form of pulses rather than a more continuous supply. These pulses often enter in the form of landslides from adjacent hillslopes or debris flows from steeper tributaries. The activities of humans such as timber harvesting, road building, and urban development can increase the frequency of sediment pulses. The question as to how mountain rivers accommodate pulses of sediment thus becomes of practical as well as academic significance.

Sediment often enters rivers in discrete pulses associated with landslides and debris flows. This is particularly so in the case of mountain streams. The topographic disturbance created on the bed of a stream by a single pulse must be gradually eliminated if the river is to maintain its morphological integrity. Two mechanisms for elimination have been identified: translation and dispersion.