Publications

With growing concern for the depletion of soil resources, conventional soil maps need to be updated and provided at finer and finer resolutions to be able to support spatially explicit human–landscape models. Three US soil point datasets—the National Cooperative Soil Survey Characterization Database, the National Soil Information System, and the Rapid Carbon Assessment dataset—were...

Climate warming should result in hotter droughts of unprecedented severity in this century. Such droughts have been linked with massive tree mortality, and data suggest that warming interacts with drought to aggravate plant performance. Yet how forests will respond to hotter droughts remains unclear, as does the suite of mechanisms trees use to deal with hot droughts. We used an...

Background and aims Biocrusts are communities of cyanobacteria, mosses, and/or lichens found in drylands worldwide. Biocrusts are proposed to enhance soil fertility and productivity, but simultaneously act as a barrier to the invasive grass, Bromus tectorum, in western North America. Both biocrusts and B. tectorum are sensitive to climate change drivers, yet how their responses might...

Temporal and spatial nonuniformity in supplies of water and sand in a river network leads to sand transport that is in local disequilibrium with the upstream sand supply. In such river networks, sand is transported downstream as elongating waves in which coupled changes in grain size and transport occur. Depending on the magnitude of each sand‐supplying event and the interval between...

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...