Publications

Every organism is defined by a set of vital rates that evolve to enhance lifetime reproductive fitness and survival of individuals and their progeny. These traits vary due to the complex but sometimes predictable interactions between individuals, populations and their environments. Collectively, these attributes are referred to as life history traits and include age and size of maturity...

No abstract available.

Agricultural production is a fundamental activity conducted on 45% of the U.S. land area, 55% of Mexico’s land area, and 7% of Canada’s land area (World Bank 2016). Because of this vast spatial extent and the strong role that land management plays in how agricultural ecosystems function, agricultural lands and activities represent a large portion of the North American carbon budget...

Grasslands, which provide fundamental ecosystem services in many arid and semiarid regions of the world, are undergoing rapid increases in fire activity and are highly susceptible to postfire-accelerated soil erosion by wind. A quantitative assessment of physical processes that integrates fire-wind erosion feedbacks is therefore needed relative to vegetation change, soil biogeochemical...

Humpback chub, Gila cypha, is an endangered warm water fish endemic to the Colorado River basin of southwestern North America. In Grand Canyon National Park, cold hypolimnetic water-release temperatures from Glen Canyon Dam have largely precluded successful spawning and recruitment of humpback chub in the mainstem Colorado River. Therefore, the species has utilized the warmer, more...

Monitoring the status and trends of species is critical to their conservation and management. However, the current state of biodiversity monitoring is insufficient to detect such for most species and habitats, other than in a few localised areas. One of the biggest obstacles to adequate monitoring is the lack of local capacity to carry out such programs. Thus, building the capacity to do...

Climatic flux together with anthropogenic changes in land use and land cover pose major threats to wildlife, but our understanding of their combined impacts is limited. In arid southwestern North America, ferruginous pygmy-owls (Glaucidium brasilianum) are of major conservation concern due to marked declines in abundance linked to changes in land use and land cover during the past...

With their iconic shells, turtles are morphologically distinct in being the only extant or extinct vertebrate animals to have their shoulders and hips inside their rib cages. By the time an asteroid hit the earth 65.5 million years ago, causing the extinction of dinosaurs, turtles were already an ancient lineage that was 70% through their evolutionary history to date. The remarkable...

For more accurate projections of both the global carbon (C) cycle and the changing climate, a critical current need is to improve the representation of tropical forests in Earth system models. Tropical forests exchange more C, energy, and water with the atmosphere than any other class of land ecosystems. Further, tropical-forest C cycling is likely responding to the rapid global warming

Relocation studies of animal movement have focused on directed versus area restricted movement, which rely on correlations between step-length and turn angles, along with a degree of stationarity through time to define behavioral states. Although these approaches may work well for grazing foraging strategies in a patchy landscape, species that do not spend a significant amount of time...

The flow (Wright and Kaplinski, 2011), suspended sediment transport (Topping et al., 2000), sediment storage (Grams et al., 2013), and sedimentology of sandbars (Rubin et al., 1998) of the 250 miles of the Colorado River that run through Grand Canyon National Park have been well studied and described. However, there has been little systematic or synoptic description of the morphologies...

Alluvial sandbars occur in lateral recirculation zones (eddies) along the Colorado River in Grand Canyon National Park (Schmidt, 1990). Resource managers periodically release controlled floods from the upstream Glen Canyon Dam to rebuild these bars (Grams et al., 2015), which erode during fluctuating dam releases, and by hillslope runoff and wind deflation (Hazel et al., 2010). Because...