Treesearch

The relationships between flame length, mass loss rate, and the Froude number have become well-established for many different fuels over the past 60 years. Chaparral, a mixture of shrub plants from the Mediterranean climate zone of southwestern North America, represents a fuel type—living plants—that has seldom been included in the development of these relationships. Flame length and mass loss data from single leaves to high bulk density fuel beds similar to wooden cribs were compared to existing correlations for circular and line burner configurations. Fuel moisture content of the fuels...

The spotted owl (Strix occidentalis) is one of the most studied raptors in the world (Lõmus 2004) because forest management throughout its range has the potential to negatively affect owl populations. Information on the California spotted owl (S. o. occidentalis) has been summarized in several literature reviews (e.g., Gutiérrez 1996; Gutiérrez and Carey 1985; Gutiérrez et al. 1995; Keane 2014; Roberts and North 2012; USFWS 1990, 1993, 2003, 2006; Verner et al. 1992a). However, the first comprehensive review of the biology of the California spotted owl was conducted by Verner et al....

California spotted owls (Strix occidentalis occidentalis) establish large home ranges averaging about 1279 ha (3,160 ac) (table 3-1), and within these home ranges individual owls select habitat at different scales, depending on their activity. At the smallest spatial scale, the nest tree, it appears there is very limited flexibility in the requirements. However, as owls select habitat at larger scales and for different activities, from nest stand to core area to foraging habitat, there is greater variability in the habitat characteristics, which suggests greater flexibility in selection....

This conservation assessment represents a comprehensive review by scientists of the current scientific knowledge about the ecology, habitat use, population dynamics, and current threats to the viability of the California spotted owl (Strix occidentalis). It is based primarily on peer-reviewed published information with an emphasis on new scientific information that has emerged since the first technical assessment for the California spotted owl (CASPO) was conducted in 1992. Substantial new information and insights exist for owls inhabiting the Sierra Nevada, but much less exists for...

The California spotted owl (Strix occidentalis occidentalis) occurs across a large portion of California, including the portion of the southern Cascade Range south of the Pit River that abuts the Sierra Nevada and throughout the Sierra Nevada, the mountains of central coastal California, and the Peninsular and Transverse Ranges of southern California. The future of the California spotted owl is of concern because of population trends over the past few decades, the potential impacts of forest management, and the threat of high-severity fire on its primary habitat of closed-canopy forest....

Counts of avian fledglings, nestlings, or clutch size that are bounded below by zero and above by some small integer form a discrete random variable distribution that is not approximated well by conventional parametric count distributions such as the Poisson or negative binomial. We developed a logistic quantile regression model to provide estimates of the empirical conditional distribution of a bounded discrete random variable. The logistic quantile regression model requires that counts are randomly jittered to a continuous random variable, logit transformed to bound them between specified...

In environmental research (i.e., plant ecophysiology, environmental microbiology, and environmental chemistry), some assays require incubation of samples at controlled temperature and darkness. Until now, due to a lack of equipment providing such possibility in situ, researchers had to move collected samples to the laboratory for incubation. Obviously, a delayed incubation and the ex situ conditions could seriously affect the assays’ results. A good example of analysis where water bath use is needed is the nitrate reductase activity (NRA) in vivo assay where plant tissue samples are...

Rare species present a challenge under changing environmental conditions as the genetic consequences of rarity may limit species ability to adapt to environmental change. To evaluate the evolutionary potential of a rare species, we assessed variation in traits important to plant fitness using multigenerational common garden experiments. Torrey pine, Pinus torreyana Parry, is one of the rarest pines in the world, restricted to one mainland and one island population. Morphological differentiation between island and mainland populations suggests adaptation to local environments may have...

To better understand the effects of debris flows on salmonid populations, we studied juvenile steelhead/rainbow trout (Oncorhynchus mykiss) populations in six streams in the Klamath Mountains of northern California: three affected by debris flows on 01 January 1997 and three that experienced elevated streamflows but no debris flows. We surveyed habitat and fish in study reaches on all six streams in September for three years following the disturbance. Pool depths, substrate size and substrate embededdness varied among streams but with no clear patterns to distinguish debris-flow from...

Frozen in the act of scavenging dinner, the vulture’s head lay on the fox’s abdomen, covering the hole it had been attempting to enlarge. When biologists pulled the bird away, they found not only a healthy looking, though dead, fox underneath, but also scores of insects scattered around. Less than a mile away the scene was repeated. This time the dead animal was a black bear, again with a vulture lying on top of it and numerous insects scattered nearby. These two scenes, which biologists found during raids conducted last year in California’s Lassen National Forest on “trespass marijuana...