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The deserts of the Southwest are under increasing pressure from growing human populations for land development - for cities, agriculture, livestock grazing, transportation and utility corridors, power plants, military activities, mining, and recreation. While some anthropogenic activities were initiated in the mid-1800s and have continued to present day, others are relatively new. The cumulative effects of historic and recent anthropogenic activities on natural resources have been both local and regional in scope. In addition, natural processes, such as local weather and global climate change, exert important influences on the landscape.
White pine blister rust (WPBR; Cronartium ribicola) – an exotic fungal pathogen first introduced into western North America in 1910 (McDonald and Hoff, 2001) – has contributed to dramatic population declines in several species of Western five-needled pines (the “white pines”) (Keane et al. 2011). For example, declines in Pinus albicaulis have been so severe that in 2011 the U.S. Fish and Wildlife Service determined that the species warranted listing under the Endangered Species Act (although the listing so far has been precluded by higher priority actions) (Federal Register 76, no.138 [July 19, 2011]: 42631-42654). White pines typically act as critical foundation species in Western forests, and their loss can have...
Mountain yellow-legged frogs (MYLF) comprise a historically abundant species complex (Sierra Nevada yellow-legged frogs, Rana sierrae, and mountain yellow-legged frogs, Rana muscosa) that occupied most high elevation aquatic habitats in the Sierra Nevada and Transverse and Peninsula ranges (Grinnell and Storer 1924, Vredenburg et al. 2005, 2007). In part because of their biphasic life cycle, MYLF are keystone species in montane food webs, and form a vital trophic link between aquatic and terrestrial ecosystems (Finlay and Vredenburg 2007). In recent decades, MYLF have declined dramatically, and are now extirpated from more than 90% of their historic range (Drost and Fellers 1996, Vredenburg et al. 2007). These declines...
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The translocated population of pronghorn (Antilocapra americana), on the Carrizo Plain National Monument (CPNM) in California, has experienced a 20-year history of population decline. Pronghorn demographic information for the CPNM is limited. More importantly, nothing is known about postnatal fawn survival, a period of extreme vulnerability in which mortality ranges from 40-80% and a critical factor affecting population trends.
Fires release carbon to the atmosphere through the combustion of organic material. Some of these greenhouse gases are returned to the landscape as biomass grows back subsequent to fires. The net change of carbon contained in vegetation on the landscape relative to pre-fire levels depends on the time since burning and the type of vegetation that grows back. The time for a forest to develop following a high severity wildfire can be several centuries, but fires that burn at lower severities may be able to replace biomass lost to fire in decadal timescales. The differing productivities of forests and their attendant regrowth rates, coupled with the characteristic fire return interval of each forest type make it difficult...
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A new analysis approach in landscape genetics and phylogeography is the creation of “genetic landscapes” to visualize genetic structure across geographic space. The Genetic Landscapes GIS Toolbox contains four tools to map genetic landscapes and to summarize multiple genetic landscapes as average and variance surfaces in ArcGIS ® (Environmental Science Research Institute, Redlands, CA, USA). Together, these tools automate a series of calculations and data manipulations to create genetic landscape surfaces directly from tables containing genetic distance or diversity data and sample location coordinates. This allows users with little GIS experience to create and analyze these complex raster surfaces with efficiency...
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We are most familiar with parasites due to the infectious diseases they cause in humans and domestic species. In tropical developing countries, for instance, Malaria, Schistosomiasis, and other neglected infectious diseases cause substantial human suffering. Most research on these diseases focuses on treating patients. Less is known about how ecology affects transmission. Of course, parasites infect non-human species. In fact, parasites are major components of biodiversity; they are dominant members of food webs, obtain biomass density comparable to free-living species, can control host populations, and can even manipulate hosts in ways that alter ecosystem function. Parasitism is a popular lifestyle, but exactly...
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In recent years, the Highly Pathogenic Avian Influenza (HPAI) strain H5N8 has been found in commercial and backyard poultry from British Columbia to California including commercial turkeys, broilers and ducks in the San Joaquin Valley of California. The recent outbreak of Highly Pathogenic Avian Influenza HPAI in North America has led to the depopulation of over 45 million poultry at approximately 200 operations in 15 states, including California, with a total economic impact over $1 billion (Eller 2015). In response, at least 29 countries as well as the European Union have banned importation of poultry from affected states. Wild waterfowl are key reservoirs of the virus, and understanding their role in transmission...
Wildfires have long been a part of the natural and human-altered environments of southern California. Keeley et al. (1999, 2004) have stated that large landscape level fires occurred in the past and will likely persist as long as southern California continues to experience episodes of severe fire weather (hot, dry winds). Despite fire suppression efforts and management plans, large and small wildfires continue to occur from both natural ignition sources and those associated with increasing human population (Keeley et al. 2004). In October and November of 2003, wildfires swept across southern California, consuming over 300,000 hectares (ha) of wild lands. This area included over 153,000 ha of San Diego County...