Southwest Biological Science Center
Hydrological regime and climate interactively shape riparian vegetation composition along the Colorado River, Grand Canyon
Question: How closely do riparian plant communities track hydrological and climatic variation in space, and how do interactions among hydrological and climatic filters influence success of different management strategies? Location: Grand Canyon, Arizona, USA Methods: Multi-year vegetation surveys were conducted across a three hydrological zones –...Butterfield, Bradley J.; Palmquist, Emily C.; Ralston, Barbara
Dryland photoautotrophic soil surface communities endangered by global change
Photoautotrophic surface communities forming biological soil crusts (biocrusts) are crucial for soil stability as well as water, nutrient and trace gas cycling at regional and global scales. Quantitative information on their global coverage and the environmental factors driving their distribution patterns, however, are not readily available. We...Rodriguez-Caballero, Emilio; Belnap, Jayne; Büdel, Burkhard; Crutzen, Paul J.; Andreae, Meinrat O.; Pöschl, Ulrich; Weber, Bettina
Warm water temperatures and shifts in seasonality increase trout recruitment but only moderately decrease adult size in western North American tailwaters
Dams throughout western North America have altered thermal regimes in rivers, creating cold, clear “tailwaters” in which trout populations thrive. Ongoing drought in the region has led to highly publicized reductions in reservoir storage and raised concerns about potential reductions in downstream flows. Large changes in riverine thermal regimes...Dibble, Kimberly L.; Yackulic, Charles B.; Kennedy, Theodore A.
Monitoring riparian-vegetation composition and cover along the Colorado River downstream of Glen Canyon Dam, Arizona
Vegetation in the riparian zone (the area immediately adjacent to streams, such as stream banks) along the Colorado River downstream of Glen Canyon Dam, Arizona, supports many ecosystem and societal functions. In both Glen Canyon and Grand Canyon, this ecosystem has changed over time in response to flow alterations, invasive species, and...Palmquist, Emily C.; Ralston, Barbara E.; Sarr, Daniel A.; Johnson, Taylor C.
Climatic sensitivity of dryland soil CO2 fluxes differs dramatically with biological soil crust successional state
Arid and semiarid ecosystems make up approximately 41% of Earth’s terrestrial surface and are suggested to regulate the trend and interannual variability of the global terrestrial carbon (C) sink. Biological soil crusts (biocrusts) are common dryland soil surface communities of bryophytes, lichens, and/or cyanobacteria that bind the soil surface...Tucker, Colin; Ferrenberg, Scott; Reed, Sasha C.
Ecohydrological implications of aeolian sediment trapping by sparse vegetation in drylands
Aeolian processes are important drivers of ecosystem dynamics in drylands, and important feedbacks exist among aeolian – hydrological processes and vegetation. The trapping of wind-borne sediments by vegetation may result in changes in soil properties beneath the vegetation, which, in turn, can alter hydrological and biogeochemical processes....Gonzales, Howell B.; Ravi, Sujith; Li, Junran; Sankey, Joel B.
Post-fire redistribution of soil carbon and nitrogen at a grassland-shrubland ecotone
The rapid conversion of grasslands into shrublands has been observed in many arid and semiarid regions worldwide. Studies have shown that fire can provide certain forms of reversibility for shrub-grass transition due to resource homogenization and shrub mortality, especially in the early stages of shrub encroachment. Field-level post-fire soil...Wang, Guan; Li, Junran; Ravi, Sujith; Dukes, David; Gonzales, Howell B.; Sankey, Joel B.
Ecosystem thresholds, tipping points, and critical transitions
Abrupt shifts in ecosystems are cause for concern and will likelyintensify under global change (Scheffer et al., 2001). The terms‘thresho lds’, ‘tipping points’, and ‘critical transitions’ have beenused interchangeably to refer to sudden changes in the integrityor state of an ecosystem caused by environmental drivers(Holling, 1973; May, 1977)....Munson, Seth M.; Reed, Sasha C.; Peñuelas, Josep; McDowell, Nathan G.; Sala, Osvaldo E.
Population dynamics of the northern tamarisk beetle (Diorhabda carinulata) in the Colorado River Basin
Throughout the Southwestern United States, riparian systems contain narrow belts of vegetation along streams and rivers. Although only a small percentage of the total land cover, this ecosystem is important for maintaining high species diversity and population densities of birds. Anthropogenic changes to Western riverine systems have enhanced...Jamison, Levi R.; van Riper, Charles
The response of source-bordering aeolian dunefields to sediment-supply changes 1: Effects of wind variability and river-valley morphodynamics
Source-bordering dunefields (SBDs), which are primarily built and maintained with river-derived sediment, are found in many large river valleys and are currently impacted by changes in sediment supply due to climate change, land use changes, and river regulation. Despite their importance, a physically based, applied approach for quantifying the...Sankey, Joel B.; Kasprak, Alan; Caster, Joshua; East, Amy; Fairley, Helen C.
The response of source-bordering aeolian dunefields to sediment-supply changes 2: Controlled floods of the Colorado River in Grand Canyon, Arizona, USA
In the Colorado River downstream of Glen Canyon Dam in the Grand Canyon, USA, controlled floods are used to resupply sediment to, and rebuild, river sandbars that have eroded severely over the past five decades owing to dam-induced changes in river flow and sediment supply. In this study, we examine whether controlled floods, can in turn resupply...Sankey, Joel B.; Caster, Joshua; Kasprak, Alan; East, Amy
Convergent validity between willingness to pay elicitation methods: an application to Grand Canyon whitewater boaters
We directly compare trip willingness to pay (WTP) values between dichotomous choice contingent valuation (DCCV) and discrete choice experiment (DCE) stated preference surveys of private party Grand Canyon whitewater boaters. The consistency of DCCV and DCE estimates is debated in the literature, and this study contributes to the body of work...Neher, Christopher; Bair, Lucas S.; Duffield, John; Patterson, David A.; Neher, Katherine