Publications

No abstract available.

The Lees Ferry reach of the Colorado River, a 25-kilometer segment of river located immediately downstream from Glen Canyon Dam, has contained a nonnative rainbow trout (Oncorhynchus mykiss) sport fishery since it was first stocked in 1964. The fishery has evolved over time in response to changes in dam operations and fish management. Long-term monitoring of the rainbow trout population...

Aeolian and fluvial processes play a fundamental role in dryland regions of the world and have important environmental and ecological consequences from local to global scales. Although both processes operate over similar spatial and temporal scales and are likely strongly coupled in many dryland systems, aeolian and fluvial processes have traditionally been studied separately, making it...

Large dams have been constructed on rivers to meet human demands for water, electricity, navigation, and recreation. As a consequence, flow and temperature regimes have been altered, strongly affecting river food webs and ecosystem processes. Experimental high‐flow dam releases, i.e., controlled floods, have been implemented on the Colorado River, USA, in an effort to reestablish pulsed...

The intensification of aridity due to anthropogenic climate change in the southwestern U.S. is likely to have a large impact on the growth and survival of plant species that may already be vulnerable to water stress. To make accurate predictions of plant responses to climate change, it is essential to determine the long‐term dynamics of plant species associated with past climate...

Marine Corps Air Station Yuma manages the Barry M. Goldwater Range-West, which encompasses approximately 2,800 square kilometers of Sonoran Desert habitat in southwestern Arizona. The Barry M. Goldwater Range is a major U.S. military installation designed as an air combat training location for the U.S. Marine Corps and U.S. Air Force, but it also includes some of the most pristine desert...

The federally endangered humpback chub Gila cypha in the Colorado River within Grand Canyon is currently the focus of a multiyear program of ecosystem-level experimentation designed to improve native fish survival and promote population recovery as part of the Glen Canyon Dam Adaptive Management Program. A key element of this experiment was a 4-year effort to remove nonnative fishes from...

Tropical rain forests play a dominant role in global biosphere-atmosphere CO2 exchange. Although climate and nutrient availability regulate net primary production (NPP) and decomposition in all terrestrial ecosystems, the nature and extent of such controls in tropical forests remain poorly resolved. We conducted a meta-analysis of carbon-nutrient-climate relationships in 113 sites across...

Several common methods for measuring suspended-sediment concentration in rivers in the United States use depth-integrating samplers to collect a velocity-weighted suspended-sediment sample in a subsample of a river cross section. Because depth-integrating samplers are always moving through the water column as they collect a sample, and can collect only a limited volume of water and...

Hourly fluctuations in flow from Glen Canyon Dam were increased in an attempt to limit the population of nonnative rainbow trout Oncorhynchus mykiss in the Colorado River, Arizona, due to concerns about negative effects of nonnative trout on endangered native fishes. Controlled floods have also been conducted to enhance native fish habitat. We estimated that rainbow trout incubation...

The humpback chub (Gila cypha) is an endangered native fish found only in the Colorado River Basin. In Grand Canyon, most humpback chub are found in the Little Colorado River and its confluence with the Colorado River. For decades, however, nonnative rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta), which prey on and compete with native fish, have dominated the Grand...

Increasing isolation of populations by habitat fragmentation threatens the persistence of many species, both from stochastic loss of small isolated populations, and from inbreeding effects in populations that have become genetically isolated. In the southwestern United States, amphibian habitat is naturally patchy in occurrence because of the prevailing aridity of the region. Streams...