Plants

Concerns about energy security and rising greenhouse gas emissions have stimulated an unprecedented increase in the push for alternative energy use, including the use of plant biomass as a source of renewable energy (bioenergy). However, meeting alternative energy goals, while also meeting food demands and mitigating potential detrimental effects of industrialized agriculture, has emerged as a...

Riparian vegetation has increased dramatically along the Colorado River downstream of Glen Canyon Dam since the closure of the dam in 1963. The spatial patterns and temporal rates of vegetation increase occur due to changes in river hydrology, dam operations, and climate. The increase in vegetation, particularly onto otherwise bare sandbars, has impacted recreational, geomorphological, biological...

Dryland regions have been degraded by invasive species, wildfire, overgrazing, agricultural conversion, energy development, recreational activity, and urban growth. These disturbances and others are accelerated by one of the fastest growing human populations in the country and a pressing background of decreasing water availability due to drought and elevated temperatures that are projected to...

In the southwest US, monsoon precipitation increases sharply along a northwest to southeast gradient. Pleuraphis jamesii or galleta grass, is an important C4 grass species that spans across this large range in precipitation pattern. In this study we are assessing the ability of galleta grass to adapt to changes in the seasonality of rainfall (termed “plasticity”). In the fall of 2014, we...

Forests in the semiarid southwestern U.S. are expected to be highly vulnerable to increasing aridity anticipated with climate change. In particular, low elevation forests and the processes of tree regeneration and mortality are likely to be highly susceptible to climate change. This work seeks to characterize how, where and when forest ecosystems will change and identify management strategies to...

Historic over-grazing of arid grasslands in the Intermountain West has led to widespread soil erosion, loss of plant diversity, and invasion by exotic species. Degraded grassland conditions can be very persistent, even after livestock use has ceased. For example, in national parks on the Colorado Plateau, livestock have been excluded for decades, but soil and native plants have not recovered on...

Arizona is the home to at least 10 cacti that are listed as endangered, threatened, or under conservation agreement. Land use and management activities that occur on federal, and to some extent state, lands on which the cacti occur require consultation among the U.S. Fish and Wildlife Service (USFWS), the agency managing the land on which the cacti is growing, and the party proposing an activity...

Land managers face tremendous challenges in the future as drought and climate change alter the abundance, distribution, and interactions of plant species. These challenges will be especially daunting in the southwestern US, which is already experiencing elevated temperatures and prolonged droughts, resulting in reduced soil moisture in an already water-limited environment. These changes will...

Floodplain red gum forests are sites of high biodiversity in arid regions of south Australia. They depend on periodic floods from rivers, but dams and diversions have reduced flood frequencies, leading to deterioration of the trees. We determined the water requirements of red gum trees so environmental flows can be used to restore and maintain the forests. We used measurements of transpiration of...

The Upper San Pedro River is one of the few remaining undammed rivers that maintain a vibrant riparian ecosystem in the southwest. However, its riparian forest is threatened by diminishing groundwater and surface water inputs, due to either changes in watershed characteristics such as changes in riparian and upland vegetation, or human activities such as regional groundwater pumping. We used...

The Rio Grande/Rio Bravo (hereafter referred to as the Rio Grande) in the Big Bend region of Texas, USA, and Chihuahua, and Coahuila, MX has substantially narrowed since the early 1900s. This narrowing has been caused by the construction and operation of dams and irrigation diversions in upstream reaches of the Rio Grande in the U.S. and the Rio Conchos in Mexico that has reduced mean and peak...

Tropical forests take in and store more carbon than any other biome in the world, but increasing temperatures may pose a threat to this invaluable service. This research aims to explore how temperature affects key tropical forest functions, such as plant photosynthesis and soil respiration. To do this, the Tropical Responses to Altered Climate Experiment (TRACE) project will use infrared heating...