Treesearch

Large woody debris (LWD) was inventoried in 1999 in five streams where LWD was removed in the early 1980s, and no LWD has been artificially introduced since. All study sites are second order channels near the confluence of the South Fork and main-stem Eel River, California. Watershed contributing areas range from 4.7 to 17.4 km², and mean active channel widths within study reaches range from 5.6 to 8.4 m. Vegetation is dominated by redwood (Sequoia sempervirens (D. Don) Endl.); three streams have old- and second-growth study reaches and two streams are entirely second growth. LWD volumes...

Terrestrial mollusks are important components of forest ecosystems, yet we know very little about the distribution and habitat of many of these species. We sampled for terrestrial mollusks in northern California with the goal of estimating the geographic ranges and developing predictive habitat models for five species that were assumed to be sensitive to land management activities. The species of interest were Ancotrema voyanum, Helminthoglypta talmadgei, Monadenia churchi, Monadenia fidelis klamathica, and M. f. ochromphalus. We randomly selected 308 plots for sampling from a grid of...

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Introduction Florida is a popular national and international tourist destination with 74.3 million visitors in 2000, and slightly more than half of these visited natural and protected areas (Visit Florida, 2001). However, in recent years, notably in 1998 and 2001, drought conditions have led to wildfires that affected large parts of the state, lead to smoke closure of interstate highways and air quality alerts (Albright, 1998; Davis, 1998; Dillon, 1998, Drummond, 1998, Farrington, 2001; Woodman, 1998a, 1998b). These conditions have become an increasing issue for recreational and leisure...

Conventional throughfall collection methods are labor intensive and analytically expensive to implement at broad scales. This study was conducted to test an alternative approach requiring infrequent sample collection and a greatly reduced number of chemical analyses. The major objective of the study was to determine the feasibility of using ion exchange resin (IER) to measure N deposition in throughfall with field deployment periods of 3 to 12 mo. Nitrogen deposition measurements in bulk throughfall collected under pine (Pinus sp.) canopies and in forest clearings were compared between...

Numerous populations from six spruce taxa, including four relict endemics, Picea chihuahuana (Chihuahua spruce), P. martinezii (Martínez spruce), P. mexicana (Mexican spruce), and P. breweriana (Brewer spruce), and two widespread species, P. engelmannii (Engelmann spruce) and P. pungens (blue spruce), were compared at homologous isozyme loci to test various hypotheses about their afŽfinities and origins. Each of the species was clearly separated, and Neighbor-Joining and Unweighted Pair Group analyses of Nei’s genetic distance grouped all populations within a taxon into their own...

Four years of severe drought from 1999 through 2003 led to unprecedented bark beetle activity in ponderosa and Jeffrey pine in the San Bernardino and San Jacinto Mountains of southern California. Pines in the San Bernardino Mountains also were heavily impacted by ozone and nitrogenous pollutants originating from urban and agricultural areas in the Los Angeles basin. We studied bark beetle activity and bark beetle associated tree mortality in pines at two drought-impacted sites in the San Bernardino Mountains, one receiving high levels of atmospheric pollutants, and one with more moderate...

We review recent advances in climate science that show cyclic climatic variation over multiple time scales and give examples of the impacts of this variation on plant populations in the western USA. The paleohistorical reconstructions we review and others indicate that plant specles track these cycles in individualistically complex ways. These dynamic histories suggest that genetic structures are in a non-equilibrium state, with populations constantly lagglng their environmental optima. Such dynamism may serve to maintain genetic variation in populations, which may be a hedge against rapid...