Publications

Arid and semiarid ecosystems play a significant role in regulating global carbon cycling, yet our understanding of the controls over the dominant pathways of dryland CO2exchange remains poor. Substantial amounts of dryland soil are not covered by vascular plants and this patchiness in cover has important implications for spatial patterns and controls of carbon cycling. Spatial variation...

Sandbars along the Colorado River in Grand Canyon National Park, USA, are an important recreational resource used as campsites by over 25,000 river runners and hikers annually. The number and size of campsites decreased following the completion of Glen Canyon Dam in 1963 due to reductions of sediment that replenish sandbars and increases in vegetation cover caused by flow regulation...

Topographic measures are frequently used in a variety of landscape ecology applications, in their simplest form as elevation, slope, and aspect, but increasingly more complex measures are being employed. We explore terrain metric similarity with changes in scale, both grain and extent, and examine how selecting the best measures is sensitive to changes in application. There are three...

Timing and spatial dynamics of tamarisk (Tamarix spp. L.) defoliation by the biological control agent Diorhabda carinulata (Desbrochers) were evaluated. Relative abundance of D. carinulata and the phenology of tamarisk along the San Juan and Colorado rivers were recorded in 2011–2012. D. carinulata began reproducing in the spring when temperatures were >15°C. Variation in spring...

As a result of anthropomorphic alterations to the lower Colorado River basin and other southwestern rivers, water turbidity has been greatly reduced and introduced, nonnative fishes thrive in these waterways. To quantify key morphological features that may allow nonnative fishes to displace native fishes, we compared eye diameter (a proxy for visual acuity) and maximum anatomical gape (a...

Sediment transport and deposition (sedimentation) occurs from natural and anthropogenic sources in rivers, lakes, and reservoirs. Substantial changes in sediment transport (such as a major increase or decrease in sediment supply) can impact aquatic ecosystems that depend on a particular sediment quantity and particle size, for example, through altering stream-channel geomorphology or...

Background and aim Biological soil crusts (biocrusts) play numerous crucial roles in drylands, which comprise over 40% of Earth’s terrestrial surface. Among these key contributions is the fixation of atmospheric nitrogen. Yet, relatively little is known about the N2 fixation capabilities of different lichen species that are found in late successional biocrust communities across drylands...

Changes in land-use practices and the extirpation (local extinction) of beaver populations in the early 20th century during European settlement are believed to have resulted in many changes in how streams in the Western United States function. Some of the negative changes that have resulted include stream channelization, soil erosion, changing vegetation, water turbidity, and a loss of...

Dryland wind transport of sediment can accelerate soil erosion, degrade air quality, mobilize dunes, decrease water supply, and damage infrastructure. We measured aeolian sediment horizontal mass flux (q) at 100 cm height using passive aspirated sediment traps to better understand q variability on the Colorado Plateau. Measured q‘hot spots’ rival the highest ever recorded including 7,460...

The tamarisk leaf beetle (Diorhabda carinulata), introduced from Eurasia in 2001 as a biological control agent for the invasive plant Tamarix ramosissima, has spread widely throughout the western USA. With D. carinulata now very abundant, scientists and restoration managers have questioned what influence this introduced arthropod might have upon the avian component of riparian ecosystems...

Species losses and additions can disrupt the relationship between resident species and the structure and functioning of ecosystems. Persistent human-trampling, on the other hand, can have similar effects through the disruption of biocrusts on surface soils of semiarid systems, affecting soil stability and fixation of carbon and nitrogen. Here, we tested the interactive and synergistic...

Aim Predictions of future suitable habitat for plant species with climate change are known to be affected by uncertainty associated with statistical approaches, climate models and occurrence records. However, life history characteristics related to dispersal and establishment processes as well as sensitivity to barriers created by land‐use may also play important roles in shaping future