Treesearch

Crop lighting is an energy-intensive necessity for nursery production of high-quality native plants and forest tree seedlings. During the winter months (especially in northern USA latitudes) or overcast or cloudy days, the amount of solar radiation reaching greenhouse crops is insufficient resulting in growth cessation, early terminal bud formation, and failure of seedlings to reach target height for outplanting (Tinus, 1995; Lopez and Runkle, 2008). In light of this, nursery growers have added supplemental lighting to increase the daily light integral (DLI), defined as the photosynthetic...

The number of monarch butterflies, charismatic nomads of North America, is rapidly declining. Milkweeds (Asclepias spp.), which are the sole food source for monarch caterpillars, have also experienced a decline throughout the breeding range of this butterfly. Milkweeds can be grown from seeds or vegetatively from root cuttings or rhizomes. Seed germination is often improved with stratification and plants are easily grown with standard propagation methods. However, some species require adjustments to the substrate to reflect unique soil conditions of their natural habitat. We encourage you...

Blackbrush (Coleogyne ramosissima Torr.) is a regionally dominant shrub species found in the transition zone between North American warm and cold deserts where it occupies millions of hectares on National Park Service, Bureau of Land Management, and National Forest lands. Blackbrush habitat is under severe threat of loss from the combined effects of exotic annual grasses, increased fire frequency, and rapid climate change. Attempts to restore blackbrush habitat have met with limited success. This research synthesizes existing information on blackbrush biology and ecology. Our goal is to...

Large fires or "megafires" have been a major topic in wildland fire research and management for over a decade. There is great debate regarding the impacts of large fires. Many believe that they (1) are occurring too frequently, (2) are burning abnormally large areas, (3) cause uncharacteristically adverse ecological harm, and (4) must be suppressed at all costs. Others believe that large fires can effectively reintroduce fire back into those declining fire-prone ecosystems where fires have been excluded for decades, thereby (1) improving ecosystem health, (2) reducing future fire hazard,...

Context: Land-use change is a global phenomenon with potential to generate abrupt spatial changes in species’ distributions. Objectives: We assessed whether theory about the internal structure of bird species’ geographic ranges can be refined to reflect abrupt changes in distribution and abundance associated with human influences on landscapes, and whether the prevalence and diversity of bird–landscape threshold relationships may significantly complicate assemblage-level avian conservation. Methods; For three large regions in the United States, we used the North American Breeding Bird...

Pyrenophora semeniperda, an important pathogen in Bromus tectorum seed banks in semi-arid western North America, exhibits >4-fold variation in mycelial growth rate. Host seeds exhibit seasonal changes in dormancy that affect the risk of pathogen-caused mortality. The hypothesis tested is that contrasting seed dormancy phenotypes select for contrasting strategies for increasing pathogen fitness, and that increased fitness on nondormant seeds involves a resource trade-off between toxin production and growth. The strategy for successfully attacking rapidly germinating nondormant seeds at high...

Population-based threshold models using hydrothermal time (HTT) have been widely used to model seed germination. We used HTT to model conidial germination and mycelial growth for the seed pathogen Pyrenophora semeniperda in a novel approach to understanding its interactions with host seeds. Germination time courses and mycelial growth rates for P.semeniperda were measured on PDA amended to achieve a series of five water potentials (ca. 0 to -6 MPa) at six constant temperatures (5-30 °C). Conidial germination was described with alternative population-based models using constant or variable...

Wildfires destroy thousands of buildings every year in the wildland urban interface. However, fire typically only destroys a fraction of the buildings within a given fire perimeter, suggesting more could be done to mitigate risk if we understood how to configure residential landscapes so that both people and buildings could survive fire.

Population size and density estimates have traditionally been acceptable ways to track species’ response to changing environments; however, species' population centroid elevation has recently been an equally important metric. Packera franciscana (Greene) W.A. Weber and A. Love (Asteraceae; San Francisco Peaks ragwort) is a single mountain endemic plant found only in upper treeline and alpine talus habitats of the San Francisco Peaks in northern Arizona and is listed by the U.S. Fish and Wildlife Service as a Threatened species under the Endangered Species Act. We used 2 recreational...

Wildfires have been increasing in size and severity over recent decades. Forest managers use fuel treatments, including tree thinning and prescribed burning, to reduce the risk of high-severity fire. The impact of fuel treatments on carbon dynamics is not fully understood; previous research indicates that because carbon is removed during fuel treatments, the net effect may not be a reduction of carbon lost in the case of wildfire. The Rodeo-Chediski Fire, which burned in Arizona in 2002, was one of the largest and most severe wildfires recorded in the southwestern United States. Our...