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The microbiotic crust study is among new focuses in investigating on the desertification control. Based on determination of algal crusts with different successive ages (4-, 8-, 17-, 34-, 42-year-old) and unconsolidated sand in the desert area, species composition and clustering analyses were carried out in this study. Results on successional orientation revealed that (1) the abundance of Cyanophyta, specially of Scytonema javanicum gradually decreased; (2) the abundance of Chlorophyta, Bacillariophyta and a species of Cyanophyta, Phormidium tenue increased; (3) the biodiversity increased gradually with the community succession; and (4) biomass of microalgae increased at the early stage, but decreased at the later...
Content Changing aspen distribution in response to climate change and fire is a major focus of biodiversity conservation, yet little is known about the potential response of aspen to these two driving forces along topoclimatic gradients. Objective This study is set to evaluate how aspen distribution might shift in response to different climate-fire scenarios in a semi-arid montane landscape, and quantify the influence of fire regime along topoclimatic gradients. Methods We used a novel integration of a forest landscape succession and disturbance model (LANDIS-II) with a fine-scale climatic water deficit approach to simulate dynamics of aspen and associated conifer and shrub species over the next 150 years under...
Mycorrhizae play a key role in ecosystem dynamics, and it is important to understand how environmental stress and climate change affect these symbionts. Several climate models predict that the intercontinental western United States will experience an increase in extreme precipitation events and warming temperatures. In 1996, northern Arizona, USA, experienced a 100-year drought that caused high local mortality of pinyon pine (Pinus edulis), a dominant tree of the southwest. We compared trunk growth, water potentials, and ectomycorrhizal dynamics for surviving trees at three high-mortality sites and adjacent low-mortality sites. Four major patterns emerged. First, surviving trees at sites that suffered high mortality...
This data package contains tables summarizing data collected during standardized gill net sampling conducted since 1957 and is part of the collection "Cornell Oneida Lake Data". The Cornell Biological Field Station (CBFS) serves as a primary field site for aquatic research at Cornell University (more information can be found at http://cbfs.dnr.cornell.edu/index.html) and is part of the Department of Natural Resources, College of Agriculture and Life Sciences. The centerpiece of the station's research program is a 60-year database on the food web of Oneida Lake, New York, that has been collected with support from the Cornell University Brown Endowment and from the New York State Department of Environmental Conservation....
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Recent investigations of demersal fish communities in deep (less than 50 m) rugged habitats have considerably increased our knowledge of the factors that influence the assemblage structure of fishes across mesophotic to deep-sea depths. Although habitat types influence deepwater fish distribution, whether different rugged seafloor features provide functionally equivalent habitat for fishes is poorly understood. In the northeastern Caribbean, numerous rugged seafloor features (e.g., seamounts, banks, canyons) punctuate insular margins, and thus create a remarkable setting in which to examine demersal fish communities across various seafloor features. Also in this region, several water masses are vertically layered...
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From 1988-1991, I studied desert rodent communities of the Canyon Country Province, Colorado Plateau. Study areas were located in Capitol Reef National Park, Utah and represented grassland, shrubland, and woodland habitats. I examined species richness, guild structure, body size, and microhabitat use, testing predictions based on patterns documented in other North American desert rodent faunas. Rodent assemblages were relatively simple with respect to species richness and number of taxonomic/foraging guilds. Among coexisting species, only the numerically dominant omnivores exhibited non-random body size. Co-occurences of species representing three taxonomic-foraging guilds were significantly different from expected...
On October 27, Paul Rogers of the Western Aspen Alliance discussed the impact of climate change on aspen ecosystems, with an emphasis on aspen fire types.The presentation covered the variability of aspen responses to fire and emphasized unique fire-related systems to wean practitioners from one-size-fits-all prescriptions for aspen forests. The Western Aspen Alliance is a partnership established to improve the management of aspen by linking ecological, social and economic sciences through collaboration and information sharing.
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Conclusions: Although there was not a detectable decrease in bird communitiy species richness resulting from experimental forest fragmentation, community structure was altered, and maintaining connections between fragments significantly mitigated these effects. Thresholds/Learnings: Synopsis: This study examined the effects of forest fragmentation on the richness, diversity, turnover, and abundance of breeding bird communities in old boreal mixed-wood forest by creating experimental forest fragments of 1, 10, 40, and 100 ha. Connected fragments were linked by 100 m wide buffer strips. The study detected no significant change in species richness as a result of forest harvesting, except in the 1 ha connected fragments...
Quaking aspen (Populus tremuloides Michx.) is the most widespread tree species in North America, and it is found throughout much of the Mountain West (MW) across a broad range of bioclimatic regions. Aspen typically regenerates asexually and prolifically after fire, and due to its seral status in many western conifer forests, aspen is often considered dependent upon disturbance for persistence. In many landscapes, historical evidence for post-fire aspen establishment is clear, and following extended fire-free periods senescing or declining aspen overstories sometimes lack adequate regeneration and are succeeding to conifers. However, aspen also forms relatively stable stands that contain little or no evidence of...
Quaking aspen (Populus tremuloides) woodlands are expected to be sensitive to climate change, and have declined in parts of the West. Great Basin mountain ranges may be near the limits of aspen’s climatic threshold, in terms of temperature and aridity, and thus are particularly vulnerable to climate change. Birds associating with aspen are likely to undergo regional population fluctuations and changes in distribution as a result of changes in aspen availability or distribution. Thus, understanding the habitat relationships of avian communities in aspen and other montane cover types is important for tracking the impacts of future landscape change. The mountainous terrain of the Humboldt-Toiyabe National Forest in...
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Arid ecosystems are often vulnerable to transformation to invasive-dominated states following fire, but data on persistence of these states are sparse. The grass/fire cycle is a feedback process between invasive annual grasses and fire frequency that often leads to the formation of alternative vegetation states dominated by the invasive grasses. However, other components of fire regimes, such as burn severity, also have the potential to produce long-term vegetation transformations. Our goal was to evaluate the influence of both fire frequency and burn severity on the transformation of woody-dominated communities to communities dominated by invasive grasses in major elevation zones of the Mojave Desert of western...
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Ephemeral aquatic habitats in Wupatki National Monument vary from naturally formed pools in arroyos over 5000 years old, to constructed catchment basins with ages estimated at 60?1000+ years old, and borrow pits and stock ponds 30?60 years old. The different ages of these pools provide different histories of colonization by amphibians and aquatic invertebrates, especially temporary pool specialists such as spadefoot toads and branchiopod crustaceans. Ten pools of five different origins and ages were surveyed in August and/or September 1997 for aquatic organisms; a total of 13 surveys were conducted. Twenty-two taxa were found, with the number of species in a pool during any survey ranging from one to 10. Species...
• Aspen communities are biologically rich and ecologically valuable, yet they face myriad threats, including changing climate, altered fire regimes, and excessive browsing by domestic and wild ungulates.• Recognizing the different types of aspen communities that occur in the Great Basin, and being able to distinguish between seral and stable aspen stands, can help managers better identify restoration needs and objectives.• Identifying key threats to aspen regeneration and persistence in a given stand or landscape is important to designing restoration plans, and to selecting appropriate treatment types.• Although some aspen stands will need intensive treatment (e.g., use of fire) to persist or remain healthy, other...
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The file contains ocular percent cover estimates for eight plant functional types occurring in lake-margin wetland plant communities in the Yukon River floodplain within the Yukon Flats National Wildlife Refuge. Observations were collected along up to four 100-meter linear transects oriented perpendicular to the lakeshore. Eight cover classes were used, and the median % cover for each cover class is shown in the dataset. Separate percent cover observations were recorded for each of eight distinct plant community encountered along each transect. Community types were associated with one of three aggregate community types (Grass/Sedge, Shrub, and Forest) for analyses. The dataset also includes a column indicating whether...
Although the impacts of exotic plant invasions on community structure and ecosystem processes are well appreciated, the pathways or mechanisms that underlie these impacts are poorly understood. Better exploration of these processes is essential to understanding why exotic plants impact only certain systems, and why only some invaders have large impacts. Here, we review over 150 studies to evaluate the mechanisms underlying the impacts of exotic plant invasions on plant and animal community structure, nutrient cycling, hydrology and fire regimes. We find that, while numerous studies have examined the impacts of invasions on plant diversity and composition, less than 5% test whether these effects arise through competition,...
The rank-abundance distribution (RAD) represents the manner in which species divide resources. Community-specific division rules that determine resource allocation among species, and thereby the shape of the RAD, have been hypothesized to account for observed stability of local species richness over time. While the shape of the RAD has been well studied, the temporal dynamics of this distribution have received much less attention. Here we assess changes in the shape of the RAD through time in a desert rodent community in Arizona (USA). Because energy use may be more appropriate for studying resource division than abundance, we also evaluate an energetic equivalent of the RAD. Significant, directional trends in the...
Quaking aspen is generally considered to be a fire-adapted species because it regenerates prolifically after fire, and it can be replaced by more shade-tolerant tree species in the absence of fire. As early-successional aspen stands transition to greater conifer-dominance, they become increasingly fire prone, until fire returns, and aspen again temporarily dominate. While this disturbance-succession cycle is critical to the persistence of aspen on many landscapes, some aspen stands persist on the landscape without fire. The complex role of fire is an important consideration for developing conservation and restoration strategies intended to sustain aspen.
    map background search result map search result map Survey of aquatic macroinvertebrates and amphibians at Wupatki National Monument, Arizona, USA: An evaluation of selected factors affecting species richness in ephemeral pools Desert Rodent Communities of the Canyon Country Province, Colorado Plateau Are boreal birds resilient to forest fragmentation? An experimental study of short-term community responses. Demersal fish assemblages on seamounts and other rugged features in the northeastern Caribbean Cover of Woody and Herbaceous Functional Groups in Burned and Unburned Plots, Mojave Desert, 2009-2013 Plant Functional Type Percent Cover Estimates from the Yukon Flats National Wildlife Refuge Survey of aquatic macroinvertebrates and amphibians at Wupatki National Monument, Arizona, USA: An evaluation of selected factors affecting species richness in ephemeral pools Desert Rodent Communities of the Canyon Country Province, Colorado Plateau Plant Functional Type Percent Cover Estimates from the Yukon Flats National Wildlife Refuge Demersal fish assemblages on seamounts and other rugged features in the northeastern Caribbean Cover of Woody and Herbaceous Functional Groups in Burned and Unburned Plots, Mojave Desert, 2009-2013