Southwest Biological Science Center
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
Inferring species interactions through joint mark–recapture analysis
Introduced species are frequently implicated in declines of native species. In many cases, however, evidence linking introduced species to native declines is weak. Failure to make strong inferences regarding the role of introduced species can hamper attempts to predict population viability and delay effective management responses. For many species...Yackulic, Charles B.; Korman, Josh; Yard, Michael D.; Dzul, Maria C.
Technical note: False low turbidity readings from optical probes during high suspended-sediment concentrations
Turbidity, a measure of water clarity, is monitored for a variety of purposes including (1) to help determine whether water is safe to drink, (2) to establish background conditions of lakes and rivers and detect pollution caused by construction projects and stormwater discharge, (3) to study sediment transport in rivers...Voichick, Nicholas; Topping, David; Griffiths, Ronald
Automated remote cameras for monitoring alluvial sandbars on the Colorado River in Grand Canyon, Arizona
Automated camera systems deployed at 43 remote locations along the Colorado River corridor in Grand Canyon National Park, Arizona, are used to document sandbar erosion and deposition that are associated with the operations of Glen Canyon Dam. The camera systems, which can operate independently for a year or more, consist of a digital camera...Grams, Paul E.; Tusso, Robert B.; Buscombe, Daniel
Pulsed flows, tributary inputs, and food web structure in a highly regulated river
1.Dams disrupt the river continuum, altering hydrology, biodiversity, and energy flow. Although research indicates that tributary inputs have the potential to dilute these effects, knowledge at the food web level is still scarce.2.Here we examined the riverine food web structure of the Colorado River below Glen Canyon Dam, focusing on organic...Sabo, John; Caron, Melanie; Doucett, Richard R.; Dibble, Kimberly L.; Ruhi, Albert; Marks, Jane; Hungate, Bruce; Kennedy, Theodore A.
Using interviews and biological sign surveys to infer seasonal use of forested and agricultural portions of a human-dominated landscape by Asian elephants in Nepal
Understanding how wide-ranging animals use landscapes in which human use is highly heterogeneous is important for determining patterns of human–wildlife conflict and designing mitigation strategies. Here, we show how biological sign surveys in forested components of a human-dominated landscape can be combined with human interviews in agricultural...Lamichhane, Babu Ram; Subedi, Naresh; Pokheral, Chiranjibi Prasad; Dhakal, Maheshwar; Acharya, Krishna Prasad; Pradhan, Narendra Man Babu; Smith, James L. David; Malla, Sabita; Thakuri, Bishnu Singh; Yackulic, Charles B.
Macroecological patterns of sexual size dimorphism in turtles of the world
Sexual size dimorphism (SSD) is a well-documented phenomenon in both plants and animals; however, the ecological and evolutionary mechanisms that drive and maintain SSD patterns across geographic space at regional and global scales are understudied, especially for reptiles. Our goal was to examine geographic variation of turtle SSD and to explore...Agha, Mickey; Ennen, Joshua R.; Nowakowski, A. Justin; Lovich, Jeffrey E.; Sweat, Sarah C.; Todd, Brian D.
Forest floor and mineral soil respiration rates in a northern Minnesota red pine chronosequence
We measured total soil CO2 efflux (RS) and efflux from the forest floor layers (RFF) in red pine (Pinus resinosaAit.) stands of different ages to examine relationships between stand age and belowground C cycling. Soil temperature and RS were often lower in a 31-year-old stand (Y31) than in 9-year-old (Y9), 61-year-old (Y61), or 123-year-...Powers, Matthew; Kolka, Randall; Bradford, John B.; Palik, Brian J.; Jurgensen, Martin