Registered users receive a variety of benefits including the ability to customize email alerts, create favorite journals list, and save searches.
Please note that a BioOne web account does not automatically grant access to full-text content. An institutional or society member subscription is required to view non-Open Access content.
Contact firstname.lastname@example.org with any questions.
The onset of plant dormancy has proven difficult to explain in nearly all ecosystems. Most research has focused on the end-of-season dynamics of deciduous ecosystems, where leaf coloration and leaf fall are the primary phenological responses. More complex are the end-of-season dynamics of grasslands, where the mechanism of dormancy is a gradual response to climatic variables. These complications are magnified in dry grasslands, where the effects of temperature on phenology are modulated by the availability of soil water. Our objectives were to identify the primary drivers influencing the timing of end of season on the shortgrass steppe and determine if the timing of start of season, end of season, or both influences the growing season length of the shortgrass steppe. Our results suggest that temperature and soil water interact to influence the timing of end of season in the shortgrass steppe and that growing season length is strongly related to the date of start of season and less so to the date of end of season. Our findings bear important implications for understanding semiarid ecosystems under climate change. Because future precipitation and temperature tend to diverge, understanding responses in seasonality of greenness as well as productivity in general must take both precipitation and temperature into account.
American pikas (Ochotona princeps) are small alpine lagomorphs and talus obligates with a narrow range of temperature tolerance, along with physiological and ecological characteristics that make them especially vulnerable to local extirpation in the face of climate change. Since their initial colonization of the Great Basin during the Pleistocene geological epoch, the distribution of pikas in this region has become more restricted, with population losses occurring especially in lower-elevation sites characterized by relatively low precipitation and high temperatures. Even where pikas have persisted, many populations are now restricted to higher elevations. We surveyed several sites in the Bodie Hills of eastern California known to have been recently occupied by pikas. Here we report the recent extirpations of 2 of these sites: one small cluster of anthropogenic patches in the historic Masonic Mining District and one natural patch on Masonic Mountain. These extirpations are consistent with those reported in California and across the Great Basin and may indicate the impending loss of pikas from this region due to impacts from global climate change.
Aquatic ecosystems overlying regions of limestone bedrock can feature active deposition of calcium carbonate in the form of travertine or tufa. Although most travertine deposits form a cement-like layer on stream substrates, mineral deposits can also form on benthic invertebrates. However, little is known about which taxa may be prone to calcium carbonate encrustation and which life history traits may make taxa more susceptible to becoming encrusted. Here we report the presence of calcium carbonate deposits on live insects collected from a montane stream in the Madrean Sky Islands (Huachuca Mountains) of Arizona between 2011 and 2013. Life history differences are examined between taxa with and without travertine deposits. Thirteen genera of aquatic insects were found with calcium carbonate deposits on the exoskeleton as well as 22 other genera, also encountered in the study stream, that have not previously been found with such deposits. Taxa with calcium carbonate encrustation had significantly longer-lived aquatic stages than those without encrustation. Furthermore, encrustation presence did not differ among aerial dispersal modes. These results suggest that the extent of calcium carbonate deposition on aquatic insects is primarily related to the length of time they are in the stream. Since mineral encrustation may reduce predation pressure and mobility, changes in patterns of travertine formation in these systems may have profound effects on ecological interactions.
Abert's squirrels (Sciurus aberti) are dependent upon ponderosa pine (Pinus ponderosa) forests in northern Arizona. Abert's squirrels feed primarily on the inner bark of ponderosa pine branches, as well as the tree's seeds and the hypogenous fungi associated with ponderosa pines. Abert's squirrels require interlocking tree canopies for escape cover and for feeding, particularly in winter months when snow impedes ground travel and the ability of Abert's squirrels to access fungi and hoarded food. In the Southwest, land managers in the ponderosa pine belt are implementing large-scale forest restoration treatments to reduce fire risk and return forest structure to pre-European settlement conditions. Restoration may decrease intrastand structural diversity and interstand heterogeneity for several decades, reducing the amount of habitat available to Abert's squirrels and reducing overall abundance. We estimated Abert's squirrel densities by enumerating squirrel feeding sign (branch clippings, clipped cones, truffle digging) over 9 years on 15 sites on Camp Navajo, an Arizona Army National Guard base in northern Arizona. Sites were treated at different times throughout the duration of the study. We evaluated the effects of forest restoration treatments on Abert's squirrel densities. We found no difference in Abert's squirrel densities on sites experiencing different treatment types. However, we did find a difference in Abert's squirrel densities between years.
The primary purpose of this study was to assess the chironomid species diversity of a high-gradient sandy-bottom watershed along the Colorado Front Range. Adult male Chironomidae were collected concurrently in 2007 and 2008 from 14 sites in the Fountain Creek Watershed (FCW), south central Colorado, USA, using ultraviolet night lights and sweep netting methods. Species-level identifications resulted in 151 species including 24 new species from 65 genera and 6 subfamilies. Forty species are reported here as new Colorado records, and many North American range extensions were recorded. Some species had geographical ranges that included the Neotropical, Afrotropical or Oriental regions. Species from high elevations and northern latitudes were common. Individual species accounts include annotated North American distributions, associated water quality and sediment (particle size) analyses for each site, and ecological notes. Species richness calculations using Jaccard and Sørensen similarity indices indicated, with some exceptions, that sites in closest proximity shared the most common species. Chironomus decorus was the most commonly collected species in the FCW, occurring at 13 of 14 sites; the orthoclad Cricotopus infuscatus was collected at 12 of the sites. In 2007–2008, the FCW had a very diverse chironomid species assemblage. How species composition changes in the watershed will be influenced by urbanization, global warming, and increased base flows from water diversions.
Seeds of many plant species are dispersed by seed-caching rodents that place groups of seeds in superficially buried scatterhoard caches. A case in point is Indian ricegrass (Achnatherum hymenoides), an important forage plant on arid western rangelands for which seedling recruitment comes largely from scatterhoards made by desert heteromyid rodents. A “diversionary seeding” strategy has been attempted for enhancing Indian ricegrass seedling recruitment by deploying commercially available seeds on the soil surface to divert rodents from recovering scatterhoards of Indian ricegrass seeds. The probability of such a passive restoration approach succeeding is likely affected by the relative desirability to rodents of Indian ricegrass seeds versus diversionary seeds. We conducted laboratory experiments to test preferences of Merriam's kangaroo rat (Dipodomys merriami), a primary dispersal agent of Indian ricegrass seeds, for Indian ricegrass seeds versus seeds of 5 diversionary seed candidates. Indian ricegrass seeds were consistently preferred over only 1 of the 5 alternate seeds in pairwise trials. In multiseed trials that presented all seed types (i.e., Indian ricegrass and the 5 alternates) simultaneously, ranking patterns of individual kangaroo rats varied significantly and Indian ricegrass was not preferred by any of the animals tested. Because individual kangaroo rats differed in seed preferences and all animals consumed certain seed types in greater amounts than they consumed Indian ricegrass, we suggest that using a mixture of different seed types in diversionary seedings is superior to deploying a single type of diversionary seeds. Understanding how population-level niche breadth is affected by dietary variation at the individual level can thus have important management implications.
Identification of individual animals is a valuable and often essential procedure for studies of animal behavior and population size. I present evidence that individual American badgers (Taxidea taxus) may be identified by natural features of their dorsal head stripes.