Sites In Colorado Research Articles

Soil amendment interacts with invasive grass and drought to uniquely influence aboveground versus belowground biomass in aridland restoration

Water‐holding soil amendments such as super‐absorbent polymer (SAP) may improve native species establishment in restoration but may also interact with precipitation or invasive species such as Bromus tectorum L. (cheatgrass or downy brome) to influence revegetation outcomes. We implemented an experiment at two sites in Colorado, U.S.A., in which we investigated the interactions of drought (66% reduction of ambient rainfall), B. tectorum seed addition (BRTE, 465 seeds/m2), and SAP soil amendment (25 g/m2) on initial plant establishment and 3‐year aboveground and belowground biomass and allocation. At one site, SAP resulted in higher native seeded species establishment but only with ambient precipitation. However, by the third year, we detected no SAP effects on native seeded species biomass. Treatments interacted to influence aboveground and belowground biomass and allocation differently. At one site, a SAP × precipitation interaction resulted in lower belowground biomass in plots with SAP and drought (61.7 ± 7.3 g/m2) than plots with drought alone (91.6 ± 18.1 g/m2). At the other site, a SAP × BRTE interaction resulted in higher belowground biomass in plots with SAP and BRTE (56.6 ± 11.2 g/m2) than BRTE alone (35.0 ± 3.7 g/m2). These patterns were not reflected in aboveground biomass. SAP should be used with caution in aridland restoration because initial positive effects may not translate to long‐term benefits, SAP may uniquely influence aboveground versus belowground biomass, and SAP can interact with environmental variables to impact developing plant communities in positive and negative ways.

Incorporating Climate Nonstationarity and Snowmelt Processes in Intensity–Duration–Frequency Analyses with Case Studies in Mountainous Areas

Abstract Downscaled high-resolution climate simulations were used to provide inputs to the physics-based Distributed Hydrology Soil Vegetation Model (DHSVM), which accounts for the combined effects of snowmelt and rainfall processes, to determine spatially distributed available water for runoff (AWR). After quasi-stationary time windows were identified based on model outputs extracted for two different mountainous field sites in Colorado and California, intensity–duration–frequency (IDF) curves for precipitation and AWR were generated and evaluated at each numerical grid to provide guidance on hydrological infrastructure design. Impacts of snowmelt are found to be spatially variable due to spatial heterogeneity associated with topography according to geostatistical analyses. AWR extremes have stronger spatial continuity compared to precipitation. Snowmelt impacts on AWR are more pronounced at the wet California site than at the semiarid Colorado site. The sensitivities of AWR and precipitation IDFs to increasing greenhouse gas emissions are found to be localized and spatially variable. In subregions with significant snowfall, snowmelt can result in an AWR (e.g., 6-h 100-yr events) that is 70% higher than precipitation. For comparison, future greenhouse gas emissions may increase 6-h 100-yr precipitation and AWR by up to 50% and 80%, respectively, toward the end of this century.

Evidence for accelerated weathering and sulfate export in high alpine environments

High elevation alpine ecosystems—the ‘water towers of the world’—provide water for human populations around the globe. Active geomorphic features such as glaciers and permafrost leave alpine ecosystems susceptible to changes in climate which could also lead to changing biogeochemistry and water quality. Here, we synthesize recent changes in high-elevation stream chemistry from multiple sites that demonstrate a consistent and widespread pattern of increasing sulfate and base cation concentrations or fluxes. This trend has occurred over the past 30 years and is consistent across multiple sites in the Rocky Mountains of the United States, western Canada, the European Alps, the Icelandic Shield, and the Himalayas in Asia. To better understand these recent changes and to examine the potential causes of increased sulfur and base cation concentrations in surface waters, we present a synthesis of global records as well as a high resolution 33 year record of atmospheric deposition and river export data from a long-term ecological research site in Colorado, USA. We evaluate which factors may be driving global shifts in stream chemistry including atmospheric deposition trends and broad climatic patterns. Our analysis suggests that recent changes in climate may be stimulating changes to hydrology and/or geomorphic processes, which in turn lead to accelerated weathering of bedrock. This cascade of effects has broad implications for the chemistry and quality of important surface water resources.

Fine‐Scale Habitat Selection by Breeding White‐Tailed Ptarmigan in Colorado

ABSTRACTSpecies distributions are influenced by climate and topography in alpine ecosystems, yet resource selection studies of alpine species are uncommon. Basic characteristics of habitats used by alpine‐endemic white‐tailed ptarmigan (Lagopus leucura) have been described to explain foraging behavior, morphology, and survival in many alpine regions; however, there is a lack of information about fine‐scale habitat selection for nesting and brood‐rearing, particularly in the southern extent of the species’ range. Few studies have tested whether nest and brood‐site selection by white‐tailed ptarmigan are influenced by fine‐scale components such as vegetation and arthropod communities. We assessed these fine‐scale habitat characteristics analyzing paired use‐available resource selection for nest (n = 61) and brood (n = 54) sites. We used conditional logistic regression for data collected in 2 alpine areas along the Front Range of Colorado, USA, during 2014 and 2015. We evaluated resource selection at larger (patch) and finer (nest site) scales. Nest‐site selection at the patch scale was best predicted by cover (%) of forage forbs, rock and gravel, and shrubs. Forage forb cover explained more variation in our top nest model at the patch scale when compared to models with specific vegetation species. Females placed their nests along elevational gradients but more so at lower elevations and selected for less graminoid cover at the nest‐site scale. Brood habitat selection at the patch level was influenced by cover (%) of rock and gravel and proximity to shrubs (m). Analysis of a subset of our brood data (n = 34) revealed females selected brood habitat that contained high arthropod abundance (e.g., Cicadellidae) over high vegetation cover, likely as a response to meet dietary requirements of chicks. Our results demonstrate how and where white‐tailed ptarmigan are currently selecting these different breeding sites in Colorado's alpine, giving us insight into consequences this alpine‐endemic bird may face if their breeding habitat is altered. © 2019 The Wildlife Society.

A Rainwater Harvesting Accounting Tool for Water Supply Availability in Colorado

Rainwater harvesting (RWH) is a renewable water supply option for nonpotable use, most commonly used for landscaping irrigation. Water rights in Colorado prohibit all RWH except residential rain barrels and a pilot project program that allows centralized rainwater harvesting for new development. Development of a natural catchment creates impervious surfaces, thereby increasing runoff, with a subsequent decrease in infiltration and losses to evapotranspiration; pilot projects are allowed to harvest a volume equal to the predevelopment runoff losses that would have occurred on new impervious areas at the site. To support this administrative policy, a tool was developed for the efficient calculation of daily allowable harvest at nearly any project site in Colorado. A reliable and useful policy tool requires the incorporation of hydrologic science with widely applicable, user-friendly design, a challenging balance of rigor and accessibility that is welcomed by engineers and policymakers alike. The daily allowable harvest is determined for each soil group as a percentage of infiltrated rainfall less the groundwater return. Horton’s infiltration method is used to model rainfall‒runoff for a range of soil parameters (NRCS hydrologic soil groups) and precipitation events (0.25- to 25-year return periods and 15-min to 24-h durations). For most events, the percent infiltration is 90% of the precipitation depth; this ratio decreases when precipitation exceeds the infiltration rate. Results are simplified in a spreadsheet tool for policy application, with allowable harvest rules binned by event duration and frequency. Simulations using the tool for a 2010‒2017 precipitation record from Colorado’s Front Range showed that RWH can supply up to 50% of the annual demand for traditional landscaping and over 100% of the water-smart landscaping demand.

Decreased nest survival associated with low temperatures in a high-elevation population of Mountain Plover (Charadrius montanus)

Mountain Plovers (Charadrius montanus) are migratory shorebirds of conservation concern that breed on grasslands and xeric tablelands scattered along the western edge of the Great Plains. Previous research from populations breeding on lower-elevation sites in Colorado and Montana suggests nest survival increases in cooler, drier environmental conditions. However, no studies have estimated Mountain Plover nest survival on high-elevation habitats, which have distinctively different climate and nesting phenology; therefore, it is unclear if these general trends hold true for the species as a whole or are regionally specific. In this study, we monitored nests of a population of Mountain Plovers breeding at high elevation in South Park, Colorado, to study influences on daily nest survival as compared to those found in literature from lower-elevation breeding sites. In contrast to studies on lower-elevation sites where daily maximum temperatures limited nest survival, we found daily minimum temperature best predicted variation in daily nest survival in South Park; survival odds declined with decreasing temperature. These results suggest that negative effects of extreme temperatures (hot or cold) may be generalities that exist between locales but are potentially mediated through different mechanisms at varying temporal scales. Although we cannot definitively conclude from our study why minimum temperature is associated with lower nest survival, we suggest alterations in incubation behavior may be a plausible mechanism that warrants future study. Overall, our study demonstrates the importance of considering differences between weather and phenology among breeding locations when estimating nest survival effects.

Total vegetation control: a comprehensive summary of herbicides, application timings, and resistance management options

AbstractTotal vegetation control (TVC) is an essential management practice to eliminate all vegetation for the purpose of protecting infrastructure, people, or natural resources on sites where vegetation poses major fire, visibility, and infrastructure risks. TVC is implemented on sites such as railroads, power substations, airports, roadsides, and oil and gas facilities. Current research has identified that tank-mixing two effective mechanisms of action is a superior resistance management strategy compared to rotating mechanisms of action; however, effective tank mixes for TVC have not been thoroughly evaluated. A field experiment was conducted from 2013 to 2014 at five sites in Colorado to compare 32 treatment combinations to two industry standards for TVC. Research objectives were (1) to identify herbicide tank-mix combinations for TVC with multiple effective mechanisms of action for resistance management, (2) to evaluate lower use rate alternatives to minimize nontarget impacts, and (3) to determine the efficacy of fall versus spring application timings. Seven treatments were identified as top-ranking treatments, averaging 96% bare-ground (BG) across five sites and two application timings. Four out of the seven top-ranked treatments included aminocyclopyrachlor, chlorsulfuron, and indaziflam. The industry standard diuron plus imazapyr was in the top ranking, whereas the other industry standard bromacil plus diuron performed inconsistently across sites. Probability modeling was used to predict the probability of achieving 97% or 100% BG with various treatment combinations. The combination of aminocyclopyrachlor, chlorsulfuron, indaziflam, and imazapyr had the highest predicted BG probability, with 88% predicted probability of achieving 100% BG, compared to 67% and 52% predicted probabilities for the industry standards diuron plus imazapyr and bromacil plus diuron, respectively. In three of the five sites, fall applications outperformed the same treatments applied in the spring. Several top-ranking treatments represent newer, lower use rate herbicide combinations that provide multiple mechanisms of action to manage herbicide-resistant weeds and minimize nontarget impacts.

A longitudinal intervention to improve young children\u2019s liking and consumption of new foods: findings from the Colorado LEAP study

BackgroundMany interventions have been conducted to improve young children’s liking and consumption of new foods however their impacts on children’s consumption have been limited. Consistent evidence supports the use of repeated exposure to improve liking for new foods however longitudinal effects lasting greater than 6 months often have not been demonstrated. Here we report the eating-related findings of the Colorado Longitudinal Eating And Physical Activity (LEAP) Study, a multi-component intervention, delivered primarily in the school setting, which aimed to improve children’s liking and consumption of a target food via repeated exposure and positive experiential learning.MethodsFour sites in rural Colorado, each housing Head Start preschool programs, matched on state vital statistics for childhood obesity rates, (2 intervention and 2 control sites) took part in a quasi-experimental study design which included 4 time points (baseline, post-intervention, one-year [Y1] and two- year [Y2] follow ups). A total of 250 children and families were enrolled (n = 143 intervention and n = 107 control; 41% Hispanic and 69% low-income). A 12-week intervention, Food Friends – Fun With New Foods®, delivered by trained preschool teachers and which focuses on positive and repeated experiences with new foods, and a 5-month (1 unit/month) social marketing “booster program” was delivered in kindergarten (one-year follow up) and 1st grade (two-year follow up). Main outcome measures included change in children’s liking for new foods, analyzed by ordinal regression using generalized estimating equations, and change in weighed consumption of new foods over time, analyzed using a hierarchical mixed effects model.ResultsThe intervention was delivered with good fidelity (87%). Both intervention and control groups demonstrated an increase in liking for the target food over time (p = 0.0001). The pattern of consumption of the target food was different, over time, for intervention and control groups (p < 0.005). In particular the change in intake between baseline and post-intervention was significantly greater in the intervention compared to the control group (p < 0.0001) though this pattern of change did not hold between baseline and Y2 follow up (p = 0.1144). Children in the intervention group who liked the target food consumed nearly double their baseline consumption at post-intervention (p < 0.0001;) and maintained this increase at Y2 follow up (p < 0.0001).ConclusionsThe Food Friends intervention, which utilized positive, repeated experiences with new foods, and was delivered with good fidelity by trained preschool teachers, found that larger improvements were observed in children’s eating behaviors than would be expected with developmentally-based changes in eating behaviors.Trial registration numberThis trial is registered at ClinicalTrials.gov: NCT01937481.Date registered: 09/09/2013; Retrospectively registered.Date first participant registered: 09/15/2010.

The Sustainable Harvest of Wild Populations of Oshá (Ligusticum porteri) in Southern Colorado for the Herbal Products Trade

It is a challenge to both use and conserve wild-harvested medicinal plants, especially when it appears they may be threatened by harvest pressure, and there is often limited biological information available to inform management decisions. Osha (Ligusticum porteri) is an important medicinal plant whose roots are harvested in the southwest USA and Mexico as an herbal remedy to treat flu, sore throat, and other illnesses. We studied population structure, root production, and the ability of osha to recover from harvest in different environmental contexts at two high-elevation southern Colorado sites with a goal of understanding what a sustainable rate of harvest might be. We experimentally harvested roots of mature osha plants at four different rates. Results indicate that low rates of harvest allow for stable osha populations over the short term (3–5 year) at our sites. Due to management interest by the USDA Forest Service, we propose a possible sustainable harvest rate of 50% of mature plants every 10 years. Given variability due to weather and other environmental factors, we recommend that future osha harvest should be planned and adjusted after careful monitoring.

Does No‐Tillage Mitigate Stover Removal in Irrigated Continuous Corn? A Multi‐Location Assessment

Core Ideas Long‐term residue removal with irrigation may degrade soil despite no‐tillage. Residue removal was assessed across three irrigated corn no‐tillage sites. Stover removal decreased soil organic C stocks by 6% and soil aggregation by 12%. Stover removal did not affect soil microbial biomass or composition. No tillage alone is not adequate to reduce erosion and maintain soil function. No‐tillage (NT) may ameliorate negative effects on soil properties from corn (Zea mays L.) stover harvest, but few long‐term irrigated continuous corn production systems have been evaluated to test this hypothesis. We evaluated three long‐term no‐tillage sites (4–13 yr) in Nebraska and Colorado that spanned a range of precipitation and soil organic carbon (SOC) levels. We measured SOC, δ13C of SOC, soil microbial biomass (SMB) and composition (i.e., phospholipid fatty acids, PLFAs), and water stable aggregation at all sites under stover retention vs. removal (∼60%). Surface SOC stocks (0–30‐cm depth) increased across the gradient and were 46.4, 57.4, and 63.1 Mg C ha–1 for Colorado, central Nebraska, and eastern Nebraska, respectively. Overall, residue removal decreased SOC stocks by 6% and soil aggregation by 12% in the 0‐ to 30‐cm depth. The δ13C signature of SOC indicated less new surface C storage under residue removal in Colorado, but not at the two Nebraska sites. Residue harvest did not decrease SMB or change soil microbial community structure, suggesting that high plant productivity buffered community composition from stover harvest impacts under NT but stimulated microbial activity levels that led to SOC loss. The high rates of stover removal used in this study decreased SOC stocks and aggregation at all sites compared to residue retained treatments, suggesting that no‐tillage alone was not sufficient to maintain erosion protection and soil function.

Distribution of a New Invasive Species, Sipha maydis (Heteroptera: Aphididae), on Cereals and Wild Grasses in the Southern Plains and Rocky Mountain States.

Sipha maydis Passerini (Heteroptera: Aphididae) is a cereal pest with an extensive geographical range that includes countries in Europe, Asia, Africa, and South America. Reports of S. maydis in the United States have been infrequent since it was first detected in California, 2007. Two studies, focused (NW CO) and multistate (OK, TX, NM, CO, UT, WY), were conducted to determine the distribution and host range of S. maydis in the Rocky Mountain and Southern Plains states over a 3-yr period, 2015-2017. In 2015, focused sampling in NW Colorado found S. maydis at 59% of the 37 sites, primarily on wheat. Sipha maydis did not survive extreme winter temperatures from late December 2015 to early January 2016 that ranged from -9.0 to -20.9°C over a 9-d period, which resulted in no aphids detected in 2016. In the multistate study, S. maydis occurred in 14.6% of 96 sites sampled in 2015, 8% of 123 sites in 2016, and 9% of 85 sites in 2017 at wide range of altitudes from 1,359 to 2,645 m. Sipha maydis occurred mainly in NW and SW Colorado and NE New Mexico along with a few sites in NE Colorado, SE Utah, and SE Wyoming. This aphid mainly infested wheat followed by a variety of eight wild grass species. No parasites, predators, sexual morphs, or significant plant damage occurred at the sites. Sipha maydis utilized 14 hosts in the United States including 8 new host records, which expands its host range to 52 plant species worldwide. Sipha maydis may be of concern to wheat, barley, and sorghum production in the United States if its populations continue to increase.

Evaluation of Turbulence Stability Schemes of Land Models for Stable Conditions

AbstractDuring stable conditions, simulated sensible heat fluxes, Qh, in land models exhibit a wide range of behavior, with some models decoupling the atmosphere and land surface, while others continue turbulent exchange. This behavior is dictated by the representation of stability within the model. We explicitly test the representation of Qh during stable conditions using observed surface temperature, air temperature, and wind speed at the Shallow Cold Pool (SCP) Experiment site in Colorado, USA. This site is characterized by frequent stable conditions and weak‐wind conditions, which are known to be difficult to represent in turbulence schemes. We test the log‐linear, Louis, Holtslag and de Bruin, Beljaar and Holtslag, and Cheng and Brutsaert stability schemes against the observations at the SCP site. We also evaluate the minimum conductance assumption commonly implemented in land models. Simulated Qh biases are generally small, due largely to compensating errors. Parameterizations could represent Qh in strong‐wind conditions and during the transition from a weak‐ to strong‐wind regime. The behavior of simulated Qh during strong winds was controlled by the aerodynamic surface roughness, z0. All models, except those that maintain a minimum conductance, were unable to represent turbulence in the weak‐wind regime. We discuss the interacting roles of countergradient fluxes, intermittent turbulence, and decoupled turbulence during this regime. Finally, we list the characteristics that a turbulence parameterization should include and recommend that land models should include a minimum conductance to simulate Qh in the weak‐wind regime.

Evaluating RZWQM2-CERES-Maize and Water Production Functions for Predicting Irrigated Maize Yield and Biomass in Eastern Colorado

Abstract. Complex crop models have been developed to simulate the interactions among biophysical processes and to extend experimental results beyond the local soil and climate conditions. However, in-depth studies on a model’s capability to predict crop growth under different conditions are sparse, and the question of whether a crop model outperforms a simple water production function (WPF) has not been answered. The objective of this study was to compare the predictive ability of a complex crop model with simple WPFs for yield and biomass estimation at three sites (Greeley, Fort Collins, and Akron) in eastern Colorado. Specifically, the CERES-Maize crop model in the Root Zone Water Quality Model (RZWQM2), which has been applied extensively in eastern Colorado for simulating maize growth, was compared to crop WPFs based on irrigation and rainfall amounts during growing seasons. Results showed that the predictive ability of CERES-Maize depended on which datasets were used for model parameterization, and that WPFs in general performed as good as or better than CERES-Maize based on a modified F-test after considering experimental uncertainties. The ability of CERES-Maize and the WPF derived from Greeley (2008-2011) to predict maize yield in Greeley (2012-2013), Fort Collins (2006-2010), and Akron (1984-1986) depended on year and site. WPFs outperformed CERES-Maize for Greeley (2012-2013) and Fort Collins (2006-2010) but performed similarly for Akron (1984-1986). This study also identified the need to improve crop model responses to water stress, especially at different growth stages, for cropping systems models to be adequate for estimating the impacts of irrigation management on yield. Ultimately, the choice between the use of a complex crop model and a simpler WPF depends on the purpose of the user and the required accuracy. Keywords: Biomass, CERES-Maize, DSSAT, Grain yield, Irrigation management, RZWQM, Water production function.

Rough Soil Surface Lessens Annual Grass Invasion in Disturbed Rangeland

Effective manipulations to prevent the spread of invasive species are needed. Downy brome (Bromus tectorum L.) is an annual invader that often expands after disturbances, compromising restoration of big sagebrush (Artemisia tridentata Nutt.) communities in western North America. This study examined the effects of two manipulations that may slow seed dispersal: soil microtopography (roughened with 50-cm relief or flat) and woody debris (0.024 m3·m−2 or none) on restoration of four disturbed mountain big sagebrush (A. tridentata Nutt. ssp. vaseyana) sites in Colorado. Treatments were crossed with seeding in a fully factorial experiment (n = 3). Microtopography and woody debris treatments were also crossed in a seed dispersal experiment using fluorescently marked downy brome seeds. In the restoration study, downy brome invaded two sites, one pervasively and one patchily. Seeding limited downy brome cover at both of these sites and also increased perennial grass and forb cover while limiting shrub cover. At the pervasively invaded site, the rough surface reduced unseeded plot downy brome cover from 13% to 3% by 5 yr post treatment. Woody debris increased shrub and perennial grass cover but had little effect on downy brome. In the seed dispersal experiment, the rough surface reduced downy brome mean dispersal distance twofold to threefold and 95% quantile distance threefold to sixfold. Woody debris slightly reduced downy brome dispersal only within rough surface plots. A rough surface may aid restoration by trapping downy brome seeds near the parent plant, limiting their spatial distribution, increasing intraspecific competition, and reducing propagule pressure. Designing landscapes to slow seed dispersal may help control invasives and promote establishment of seeded species.

Detectability of Repeated Airborne Laser Scanning for Mountain Landslide Monitoring

Multi-temporal airborne laser scanning (ALS) surveys have become a prime consideration for detecting landslide movements and evaluating landslide risk in mountain areas. The minimum elevation change (or detectability) that can be detected by repeated ALS surveys has become a critical threshold for landslide researchers and engineers to decide if ALS is a capable tool for detecting targeted landslides and arranging the minimum time span between two scans if ALS is a choice. The National Center for Airborne Laser Mapping (NCALM) at the University of Houston conducted three repeated ALS surveys at the Slumgullion landslide site in Colorado, U.S. over one week in July of 2015. These repeated ALS surveys provide valuable datasets for evaluating the vertical detectability of multi-temporal ALS surveys in a typical mountain area. According to this study, the difference of digital elevation models (DDEM) derived from ALS has the ability of detecting a minimum elevation change of 5 cm over flatter and moderately rugged terrain areas (slope &lt; 20 degrees) and a minimum of a 10-cm elevation change over rugged terrain areas (20 degrees &lt; slope &lt; 40 degrees). However, the DDEM values over highly rugged terrain areas (slope &gt; 40 degrees), such as cliff and landslide scarps, should be interpolated with caution. Global Navigation Satellite Systems (GNSS) and Terrestrial Laser Scanning (TLS) surveys were also performed at the middle portion of the landslide area for assessing the accuracy of ALS datasets. The accuracy of ALS varies from approximately one decimeter (~10 cm) to one foot (~30 cm) depending on the roughness of terrain surface and vegetation coverage (point density). The detectability and accuracy estimates of ALS measurements obtained from the case study could be used as a reference for estimating the performance of modern ALS in mountain areas with similar topography and vegetation coverage.

Lead isotope ratios of Pueblo I lead-glazed ceramics and galena from Colorado and Pueblo II galena from Chaco Canyon, New Mexico

The earliest glazes in the American Southwest were produced during the early Pueblo I period (ca. 750–850 CE) in the Upper San Juan region of Colorado. Petrographic and isotopic techniques were used to study these early glaze-painted pots and to address questions of production locales and procurement strategies. The results of this study identify the preferred source of lead utilized by the potters as originating in the Galena District, in the Lake City and Uncompahgre calderas, in the western San Juan Mountains of Colorado. Glaze paints from three locations in the Mesa Verde region were produced with galena from these deposits, indicating that even when potters were choosing to use different clays and temper, the source of lead remained the same. Galena ores from these deposits have additionally been identified at other locations, including Dillard, a Basketmaker III site in southwest Colorado and in Pueblo II contexts in Pueblo Bonito, Chaco Canyon in New Mexico, indicating continuity in knowledge of distant lead sources.

Multiple Proxy Estimates of Atmospheric CO2 From an Early Paleocene Rainforest

AbstractProxy estimates of atmospheric CO2 are necessary to reconstruct Earth's climate history. Confidence in paleo‐CO2 estimates can be increased by comparing results from multiple proxies at a single site, but so far this strategy has been implemented only for marine‐based techniques. Here we present CO2 estimates for the well‐studied early Paleocene Castle Rock site in Colorado using four paleobotanical proxies. Median estimates range from 470 to 813 ppm, demonstrating fair correspondence. The synthesis yields a median of 616 ppm (352–1110 ppm at 95% confidence), considerably higher than previous early Paleocene CO2 estimates (~300 ppm). Ash bed geochronology by the high‐precision U‐Pb method places the Castle Rock assemblage at 63.844 ± 0.097 Ma (fully propagated 2σ error). When these results are placed into the broader context of other Cenozoic CO2 estimates from plant‐gas‐exchange approaches and coeval estimates of global mean surface temperature, a pattern emerges of an Earth system sensitivity around 3 °C per CO2 doubling during the Paleocene and Eocene, a time with little land ice, then steepening to &gt;7 °C after the Eocene once land ice was present on Antarctica.

The impact of air pollutant deposition on solar energy system efficiency: An approach to estimate PV soiling effects with the Community Multiscale Air Quality (CMAQ) model

Deposition and accumulation of aerosol particles on photovoltaics (PV) panels, which is commonly referred to as “soiling of PV panels,” impacts the performance of the PV energy system. It is desirable to estimate the soiling effect at different locations and times for modeling the PV system performance and devising cost-effective mitigation. This study presents an approach to estimate the soiling effect by utilizing particulate matter (PM) dry deposition estimates from air quality model simulations. The Community Multiscale Air Quality (CMAQ) modeling system used in this study was developed by the U.S. Environmental Protection Agency (U.S. EPA) for air quality assessments, rule-making, and research. Three deposition estimates based on different surface roughness length parameters assumed in CMAQ were used to illustrate the soling effect in different land-use types. The results were analyzed for three locations in the U.S. for year 2011. One urban and one suburban location in Colorado were selected because there have been field measurements of particle deposition on solar panels and analysis on the consequent soiling effect performed at these locations. The third location is a coastal city in Texas, the City of Brownsville. These three locations have distinct ambient environments. CMAQ underestimates particle deposition by 40% to 80% when compared to the field measurements at the two sites in Colorado due to the underestimations in both the ambient PM10 concentration and deposition velocity. The estimated panel transmittance sensitivity due to the deposited particles is higher than the sensitivity obtained from the measurements in Colorado. The final soiling effect, which is transmittance loss, is estimated as 3.17 ± 4.20% for the Texas site, 0.45 ± 0.33%, and 0.31 ± 0.25% for the Colorado sites. Although the numbers are lower compared to the measurements in Colorado, the results are comparable with the soiling effects observed in U.S.

Soil Carbon Pools in Dryland Agroecosystems as Affected by Several Years of Drought

No-till and increased cropping intensity (CI) can increase yield and soil organic C (SOC) in the US Great Plains compared with traditional wheat ( L.)-fallow management. However, gains in SOC and other C pools may not be permanent. Increasing frequency of drought may reduce C inputs and potentially reverse gains accrued during wetter periods. This study examined the effect of drought on the persistence of SOC with two objectives: (i) to determine soil C pools (0-20 cm) after 24 yr in no-till as influenced by potential evapotranspiration (PET), landscape position (slope), and CI; and (ii) to compare the size of the C pools after the first 12 yr (wet) versus the subsequent 12 yr, notable for frequent droughts. Rotations were wheat-corn ( L.)-fallow (WCF), continuous cropping (CC), and a grass Conservation Reserve Program mixture planted across slopes at three sites in Colorado with similar precipitation but increasing PET. After 24 yr, water-soluble organic C increased with CI from WCF to CC to grass with 250, 340, and 440 kg C ha, respectively. Soil microbial biomass C also increased with CI-1500, 1660, and 2135 kg C ha for WCF, CC, and grass, respectively. The particulate organic matter C pool had a three-way interaction with PET, slope, and CI. Overall, between Years 12 and 24, SOC increased in grass by 16.9%, with a rate of 425 kg C ha yr sequestration compared with 10.5 and 1.4% for the WCF and CC systems, respectively.

Influence of Metal Contamination and Sediment Deposition on Benthic Invertebrate Colonization at the North Fork Clear Creek Superfund Site, Colorado, USA.

Assessing benthic invertebrate community responses to multiple stressors is necessary to improve the success of restoration and biomonitoring projects. Results of mesocosm and field experiments were integrated to predict how benthic macroinvertebrate communities would recover following the removal of acid mine drainage from the North Fork of Clear Creek (NFCC), a U.S. EPA Superfund site in Colorado, USA. We transferred reference and metal-contaminated sediment to an upstream reference site where colonization by benthic macroinvertebrates was measured over 30 days. Additionally, a mesocosm experiment was performed to test the hypothesis that patches of metal-contaminated substrate impede recolonization downstream. Abundance in all treatments increased over time during field experiments; however, colonization was slower in treatments with metal-contaminated fine sediment. Community assemblages in treatments with metal-contaminated fine substrate were significantly different from other treatments. Patterns in the mesocosm study were consistent with results of the field experiment and showed greater separation in community structure between streams with metal-contaminated sediments and reference-coarse habitats; however, biological traits also helped explain downstream colonization. This study suggests that after water quality improvements at NFCC, fine-sediment deposition will likely reduce recovery potential for some taxa; however highly mobile taxa that avoid patches of contaminated habitats can recover quickly.