Publications

Riparian ecosystems are characterized by abundance of water and frequent flow related disturbance. River regulation typically decreases peak flows, reducing the amount of disturbance and altering the vegetation. The San Miguel River is one of the last relatively unregulated rivers remaining in the Colorado River Watershed. One goal of major landowners along the San Miguel including the...

We investigated the functions of perch relocations within a communal night roost of wintering bald eagles (Haliaeetus leucocephalus) along the Nooksack River, Washington, during two winters. We tested seven predictions of two nonexclusive hypotheses: (1) bald eagles relocate within roosts to assess foraging success of conspecifics and (2) bald eagles relocate to obtain thermoregulatory...

Rates of change in final summer densities of two desert annuals, Eriogonum abertianum and Haplopappus gracilis, as constrained by their initial winter germination densities were estimated with regression quantiles and compared with mechanistic fits based on a self-thinning rule proposed by Guo et al. (1998); Oikos 83: 237–245). The allometric relation used was equivalent to S=Nf (Ni)−1...

The virile crayfish (Orconectes virilis), an aggressive polytrophic species, has been introduced into many Arizona streams. I investigated competition and predation between this crayfish and several native Arizona fishes. I conducted field experiments to assess competition for food between crayfish and fish, and laboratory experiments to examine competition for shelter and food, and...

Floodplain plant–herbivore–hydroperiod interactions have received little attention despite their potential as determinants of floodplain structure and functioning. We used five types of exclosures to differentially exclude small-, medium-, and large-sized mammals from accessing Fremont cottonwood (Populus deltoides Marshall subsp. wizlizenii (Watson) Eckenwalder) seedlings and saplings...

1. Knowledge of synchrony in trends is important to determining regional responses of lakes to disturbances such as atmospheric deposition and climate change. We explored the temporal coherence of physical and chemical characteristics of two series of mostly alpine lakes in nearby basins of the Colorado Rocky Mountains. Using year-to-year variation over a 10-year period, we asked whether...

We examine the relationships between abundance of grassland nesting songbirds observed in the Boulder Open Space, CO, USA and parameters that described landscape and habitat characteristics, in order to provide information for Boulder Open Space planners and managers. Data sets included bird abundance and plant species composition, collected during three breeding seasons (1994–1996), and...

Research beginning 40 years ago suggested that semi-arid lands of the USA have higher unit discharges for a given recurrence interval than occur in other areas. Convincing documentation and arguments for this suspicion, however, were not presented. Thus, records of measured rainfall intensities for specified durations and recurrence intervals, and theoretical depths of probable maximum

Woody riparian vegetation in western North American riparian ecosystems is commonly dependent on alluvial groundwater. Various natural and anthropogenic mechanisms can cause groundwater declines that stress riparian vegetation, but little quantitative information exists on the nature of plant response to different magnitudes, rates, and durations of groundwater decline. We observed...

No abstract available.

The purpose of this paper is to foster discussion on the basic issue of whether it is appropriate or not to intervene in designated wilderness areas that have been “trammeled by man” and, as a result, no longer retain their “primeval character and influence.” We explore this wilderness management dilemma (whether we can or should actively manage wilderness conditions to restore and...

Distribution, movements, and habitat use of 10 wild adult razorback suckers (Xyrauchen texanus) were examined in Lake Mohave, Arizona-Nevada, from November 1994 through July 1997. Movement rates (0.00-17.35 km d⁻¹) and ranges (x̄ = 39 km) were similar to those for riverine populations. All study fish returned to spawning sites used in previous years, but they also visited other spawning...