Treesearch

Patterns of association between humans and biodiversity typically show positive, negative, or negative quadratic relationships and can be described by 3 hypotheses: biologically rich areas that support high human population densities co-occur with areas of high biodiversity (productivity); biodiversity decreases monotonically with increasing human activities (ecosystem stress); and biodiversity peaks at intermediate levels of human influence (intermediate disturbance). To test these hypotheses, we compared anthropogenic land cover and housing units, as indices of human influence, with bird...

Low recruitment of new plants as currently observed in several California oak species might partly result from insufficient storage of vital resources (reduced ability to regrow after disturbance) or from low adaptation to environmental stress, such as drought. We conducted two studies under divergent environmental conditions to compare seedlings of California oaks with ecologically equivalent species from the eastern Mediterranean region, where recruitment has been substantial over the past 25-30 years. Resource concentrations (nonstructural carbohydrates and nitrogen) in taproots and the...

Plant species assemblages, communities or regional floras might be termed saturated when additional immigrant species are unsuccessful at establishing due to competitive exclusion or other inter-specific interactions, or when the immigration of species is off-set by extirpation of species. This is clearly not the case for state, regional or national floras in the USA where colonization (i.e. invasion by exotic species) exceeds extirpation by roughly a 24 to 1 margin. We report an alarming temporal trend in plant invasions in the Pacific Northwest over the past 100 years whereby counties...

Increasing levels of recreational use in wilderness, backcountry, and roadless areas has the potential to impact wildlife species, including those that depend on these protected areas for survival. Wildlife and wilderness managers will be more successful at reducing these impacts if they understand the potential impacts, factors affecting the magnitude of impacts, and available management strategies and implementation methods. In this reading list, we summarize over 230 books, articles, bibliographies, and Internet resources to provide managers with relevant research on backcountry...

We find ourselves in general agreement with many of Harrison's remarks especially since we both find our data present a ' strong case that at county to state scales, exotic plant invasions have led to few native plant extinctions' (emphasis added, Harrison 2007: 000). Where we differ appears related to the breadth of scales to which our conclusions may apply. In addition to the Myth of Plant Species Saturation (henceforth, the Myth paper ) in question, we have published several complementary papers which may alleviate some of Harrison's concerns.

For a broader study of the climate drivers of regional-fire years in the Northern Rockies, we reconstructed a history of surface fires at 21 sites in Idaho and western Montana. We targeted sites that historically sustained frequent surface fires and were dominated or codominated by ponderosa pine (Pinus ponderosa P. & C. Lawson). Our objective is to report the site-specific fire and site information we did not report in our regional study that might be useful to local land managers for determining such things as Fire Regime Condition Class. We include 23 sites-20 from our regional study...

This study evaluates the relative ability of simple light detection and ranging (lidar) indices (i.e., mean and maximum heights) and statistically derived canonical correlation analysis (CCA) variables attained from discrete-return lidar to estimate forest structure and forest biomass variables for three temperate subalpine forest sites. Both lidar and CCA explanatory variables performed well with lidar models having slightly higher explained variance and lower root mean square error. Adjusted R2 values were 0.93 and 0.93 for mean height, 0.74 and 0.73 for leaf area index, and 0.93 and...

Seed availability and leaf litter limit plant establishment in some ecosystems. To evaluate the hypothesis that these factors limit understory plant recruitment in Pinus ponderosa forests, I conducted a seeding and litter removal experiment at six thinned sites in the Fort Valley Experimental Forest, northern Arizona. Experimental seeding of four native species (Penstemon virgatus, Erigeron formosissimus, Elymus elymoides, and Festuca arizonica) and raking of litter occurred in 2005. Seeding resulted in a substantial recruitment of 14 to 103 seedlings/m2 (1 to 10/ft2) one month after...

The high cost of suppressing wildfires is taking a toll on federal and state agencies alike. Large wildland fires are complex, costly events influenced by a vast array of physical, climatic, and social factors. During five of the last eight years, the Forest Services' wildfire suppression expenditures have topped $1 billion, and total federal wildland suppression expenditures have been more than $1.4 billion. Wildfire suppression has become an increasingly larger part of an already constrained Forest Service budget, accounting for more than 40% of the budget in recent years compared to 10%...

The Taylor Woods "Levels-of-Growing-Stock" study was established in 1962 to create a replicated ponderosa pine density experiment for the Southwest, making a valuable addition to research in the Fort Valley Experimental Forest. Basal area treatments ranged from 5-20 m2/ha (19-80 ft2/ac) when installed, designed as growing stock levels 30/40, 60, 80, 100, 120 and 150. Residual trees averaged only 12 cm DBH despite being 42 years old. These 0.3- to 0.5-ha (0.75- to 1.24-ac) plots, with three of each growing stock level, were revisited for maintenance on a decadal basis including a recent...