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Cultivated lands in the U.S. Midwest have been affected by soil erosion, causing soil organic carbon (SOC) redistribution in the landscape and other environmental and agricultural problems. The importance of SOC redistribution on soil productivity and crop yield, however, is still uncertain. In this study, we used a model framework, which includes the Unit Stream Power-based Erosion Deposition (USPED) and the Tillage Erosion Prediction (TEP) models, to understand the soil and SOC redistribution caused by water and tillage erosion in two agricultural fields in the U.S. Midwest. This model framework was evaluated for different digital elevation model (DEM) spatial resolutions (10-m, 24-m, 30-m, and 56-m) and topographic...
Riverine exports of organic and inorganic carbon (OC, IC) to oceans are intricately linked to processes occurring on land. Across high latitudes, thawing permafrost, alteration of hydrologic flow paths, and changes in vegetation may all affect this flux, with subsequent implications for regional and global carbon (C) budgets. Using a unique, multi-decadal dataset of continuous discharge coupled with water chemistry measurements for the Mackenzie River, we show major increases in dissolved OC (DOC) and IC (as alkalinity) fluxes since the early 1970s, for a watershed that covers 1.8 M km2 of northwestern Canada, and provides substantial inputs of freshwater and biogeochemical constituents to the Arctic Ocean. Over...
Soil organic carbon (SOC) storage plays a major role in the global carbon cycle and is affected by many factors including land use/management changes (e.g., biofuel production-oriented changes). However, the contributions of various factors to SOC changes are not well understood and quantified. This study was designed to investigate the impacts of changing farming practices, initial SOC levels, and biological enhancement of grain production on SOC dynamics and to attribute the relative contributions of major driving forces (CO2 enrichment and farming practices) using a fractional factorial modeling design. The case study at a crop site in Iowa in the United States demonstrated that the traditional corn-soybean (CS)...
Spatially-explicit state-and-transition simulation models of land use and land cover (LULC) increase our ability to assess regional landscape characteristics and associated carbon dynamics across multiple scenarios. By characterizing appropriate spatial attributes such as forest age and land-use distribution, a state-and-transition model can more effectively simulate the pattern and spread of LULC changes. This manuscript describes the methods and input parameters of the Land Use and Carbon Scenario Simulator (LUCAS), a customized state-and-transition simulation model utilized to assess the relative impacts of LULC on carbon stocks for the conterminous U.S. The methods and input parameters are spatially explicit...
Wind erosion and associated dust emissions play a fundamental role in many ecological processes and provide important biogeochemical connectivity at scales ranging from individual plants up to the entire globe. Yet, most ecological studies do not explicitly consider dust-driven processes, perhaps because most relevant research on aeolian (wind-driven) processes has been presented in a geosciences rather than an ecological context. To bridge this disciplinary gap, we provide a general overview of the ecological importance of dust, examine complex interactions between wind erosion and ecosystem dynamics from the scale of plants and surrounding space to regional and global scales, and highlight specific examples of...
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Collaboration has taken root in national forest planning, providing expanded opportunities for stakeholder participation in decision-making, but are these processes considered meaningful by key stakeholders? Do the processes result in increased participation by key stakeholders? We present results of a study of stakeholder perspectives of a collaborative planning process on the Grand Mesa, Uncompahgre, and Gunnison National Forests in Western Colorado, U.S.A. The stakeholders were stratified by participation levels in order to explore a possible relationship between participation and perceptions of the collaborative process. We used a Q-methodology approach to compare and contrast perspectives across participant...
In many places along the lower Colorado River, saltcedar (Tamarix spp) has replaced the native shrubs and trees, including arrowweed, mesquite, cottonwood and willows. Some have advocated that by removing saltcedar, we could save water and create environments more favourable to these native species. To test these assumptions we compared sap flux measurements of water used by native species in contrast to saltcedar, and compared soil salinity, ground water depth and soil moisture across a gradient of 200?1500 m from the river's edge on a floodplain terrace at Cibola National Wildlife Refuge (CNWR). We found that the fraction of land covered (fc) with vegetation in 2005?2007 was similar to that occupied by native...
Biological soil crusts, consisting of cyanobacteria, green algae, lichens, and mosses, are important in stabilizing soils in semi-arid and arid lands. Integrity of these crusts is compromised by compressional disturbances such as foot, vehicle, or livestock traffic. Using a portable wind tunnel, we found threshold friction velocities (TFVs) of undisturbed crusts well above wind forces experienced at these sites; consequently, these soils are not vulnerable to wind erosion. However, recently disturbed soils or soils with less well-developed crusts frequently experience wind speeds that exceed the stability thresholds of the crusts. Crustal biomass is concentrated in the top 3 mm of soils. Sandblasting by wind can...
Rising atmospheric carbon dioxide concentration ([CO2]) has the potential to stimulate ecosystem productivity and sink strength, reducing the effects of carbon (C) emissions on climate. In terrestrial ecosystems, increasing [CO2] can reduce soil nitrogen (N) availability to plants, preventing the stimulation of ecosystem C assimilation; a process known as progressive N limitation. Using ion exchange membranes to assess the availability of dissolved organic N, ammonium and nitrate, we found that CO2 enrichment in an Australian, temperate, perennial grassland did not increase plant productivity, but did reduce soil N availability, mostly by reducing nitrate availability. Importantly, the addition of 2 °C warming...
The evolution of water law provides a fascinating example of the responses of law to changing social and economic conditions. xcScott and Coustalin 1995 and xcMiller 1996 have provided the details of water law change from Roman times to the 20th century. The law of prior occupancy (an early version of the priority doctrine), wherein the earliest water users had first call on available water, was adopted in England from Roman Law. At the start of the industrial revolution, it became clear that these historical uses were preventing water access for the newer, more technical industries. To accommodate these needs, a ?reasonable use? doctrine evolved, allowing new activities access as long as they did not ?unreasonably?...
Valley-fill alluvium deposited from ca. A.D. 1400 to 1880 is widespread in tributaries of the Paria River and is largely coincident with the Little Ice Age epoch of global climate variability. Previous work showed that alluvium of this age is a mappable stratigraphic unit in many of the larger alluvial valleys of the southern Colorado Plateau. The alluvium is bounded by two disconformities resulting from prehistoric and historic arroyo cutting at ca. A.D. 1200–1400 and 1860–1910, respectively. The fill forms a terrace in the axial valleys of major through-flowing streams. This terrace and underlying deposits are continuous and interfinger with sediment in numerous small tributary valleys that head at the base of...
Mn uptake from MnCl2 solution and chlorophyll fluorescence (as a selected vitality parameter) were studied in the epiphytic lichens Lobaria pulmonaria (tripartite, heteromerous lichen with the green alga Dictyochloropsis as primary photobiont and Nostoc in cephalodia), Nephroma helveticum (bipartite, heteromerous lichen with Nostoc photobiont) and Leptogium saturninum (bipartite, homoiomerous lichen with Nostoc photobiont). Extracellular adsorption and intracellular uptake of Mn increased in the order L. pulmonaria < N. helveticum < L. saturninum. Mn increasingly reduced the effective quantum yield of photosystem 2 (?2) in the same order. CaCl2 and MgCl2 alleviated the Mn-induced reduction of ?2. Moist thalli of...
Stream discharge and geochemical data were collected at two sites along lower Ashley Creek, Utah, from 1999 to 2003, to assess the success of a site specific salinity and Se remediation project. The remediation project involved the replacement of a leaking sewage lagoon system that was interacting with Mancos Shale and increasing the dissolved salinity and Se load in Ashley Creek. Regression modeling successfully simulated the mean daily dissolved salinity and Se loads (R(2) values ranging from 0.82 to 0.97) at both the upstream (AC1) and downstream (AC2/AC2A) sites during the study period. Prior to lagoon closure, net gain in dissolved-salinity load exceeded 2177 metric tons/month and decreased after remediation...
Global climate change is projected to produce warmer, longer, and more frequent droughts, referred to here as “global change-type droughts�, which have the potential to trigger widespread tree die-off. However, drought-induced tree mortality cannot be predicted with confidence, because long-term field observations of plant water stress prior to, and culminating in, mortality are rare, precluding the development and testing of mechanisms. Here, we document plant water stress in two widely distributed, co-occurring species, piñon pine (Pinus edulis) and juniper (Juniperus monosperma), over more than a decade, leading up to regional-scale die-off of piñon pine trees in response to global change-related drought....
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Reports of decreasing quaking aspen (Populus tremuloides) cover in forests of the western USA have caused concern about the long-term persistence of aspen on landscape scales. We assessed changes in overstory aspen dominance on the Uncompahgre Plateau in western Colorado over a 20 year period. We measured stand density, species composition and regeneration in 53 undisturbed, mature pure aspen, pure conifer, and mixed aspen/conifer stands originally inventoried between 1979 and 1983. Ages of overstory and understory trees were used to evaluate long-term change in regeneration and overstory development. While pure aspen stands occupy 16% of the study area, mixed aspen and conifer stands cover 62% of the forested landscape...
This study evaluates the hypothesis that biological grazing refuges have an important role in plant-grazer interactions of grasslands with a long history of grazing. We assessed the hypothesis that clumps of the spiny cactus Opuntia polyacantha provide biological refuges from cattle grazing, affecting cover and seedhead production of associated vascular plants in the shortgrass steppe of the North America. The study was based on sampling inside and outside Opuntia clumps in eight long-term moderately grazed pastures established 60 yr ago and their respective ungrazed controls. Opuntia clumps provided a refuge for seedhead production of the dominant grass (Bouteloua gracilis) and for cover and seedhead production...
Categories: Publication; Types: Citation, Journal Citation; Tags: Oikos
Litter decomposition in terrestrial habitats is affected by many factors, including temperature, moisture, and nutrient and organic composition of litter. Among organic components, lignin is the primary controlling factor of decomposition rates of surface litter during the later phase of decomposition in most habitats and during the initial phase in warm, moist habitats (i.e., those with a high actual evapotranspiration, AET). In habitats with moderate AET's, we suggest that the decreased control by lignin over annual decomposition rates of surface litter is due, at least in part, to a significant periodic or seasonal influence of other carbonbased plant secondary metabolites over rates in the initial phase of decomposition....
The importance, and even the existence, of competition among plants in arid ecosystems has often been questioned. An influential statement of Shreve (113) asserted that interspecific competition does not occur in deserts, and Went (145) denied that competition between desert plants occurs at all. Neither provided evidence for his assertions, although Shreve pointed out the diversity of habits and phenologies found among desert species. He may have been responding to the strong emphasis placed on competition by Clements and his followers (e.g. 27). The importance of competition in natural communities has recently been debated (28, 109, 127). These reviews suggested that terrestrial plant communities are among the...
We analyzed the geographic distribution of Tubifex tubifex from various river drainages in central Colorado by genetic screening with specific mitochondrial 16S ribosomal DNA (mt 16S rDNA) markers. Four distinct mt 16S rDNA lineages are evident. The sites varied with respect to land- and water-use practices. All sites represented habitats presumed capable of supporting oligochaetes. At the locations where whirling disease has had the greatest impact on resident rainbow trout, T. tubifex, representing lineages I and III (genotypes known to be susceptible to Mxyobolus cerebralis), were most commonly found. In contrast, at sites less affected by whirling disease, T. tubifex of lineages V and VI that are more resistant...
Soil microbial respiration is a critical component of the global carbon cycle, but it is uncertain how properties of microbes affect this process. Previous studies have noted a thermodynamic trade-off between the rate and efficiency of growth in heterotrophic organisms. Growth rate and yield determine the biomass-specific respiration rate of growing microbial populations, but these traits have not previously been used to scale from microbial communities to ecosystems. Here we report seasonal variation in microbial growth kinetics and temperature responses (Q10) in a coniferous forest soil, relate these properties to cultured and uncultured soil microbes, and model the effects of shifting growth kinetics on soil...


map background search result map search result map Twenty-year change in aspen dominance in pure aspen and mixed aspen/conifer stands on the Uncompahgre Plateau, Colorado, USA Why won't they come? Stakeholder perspectives on collaborative national forest planning by participation level. Twenty-year change in aspen dominance in pure aspen and mixed aspen/conifer stands on the Uncompahgre Plateau, Colorado, USA Why won't they come? Stakeholder perspectives on collaborative national forest planning by participation level.