Western Colorado Research Articles

Grazing-Induced Changes to Biological Soil Crust Cover Mediate Hillslope Erosion in Long-Term Exclosure Experiment

Dryland ecosystems are particularly vulnerable to erosion generated by livestock grazing. Quantifying this risk across a variety of landscape settings is essential for successful adaptive management, particularly in light of a changing climate. In the Upper Colorado River Basin, there are nearly 25 000 km2 of rangelands with underlying soils derived from Mancos Shale, an erodible and saline geologic parent material. Salinity is a major concern within the Colorado River watershed, much of which is attributed to runoff and leaching from Mancos Shale deposits. In a 60-yr paired-watershed experiment in western Colorado, we used silt fences to measure differences in saline hillslope erosion, including both total sediment yield and concentrations of primary saline constituents (Na and Se), in watersheds that were either exposed to grazing or where livestock was excluded. After accounting for the strong effects of soil type, slope, and antecedent precipitation, we found that grazing increased sediment loss by ≈50% across our 8-yr time series (0.1–1.5 tn ha−1), consistent with levels reported at the watershed scale in early published work from studies at the same location. Eroded sediment Se levels were low and unaffected by grazing history, but Na concentrations were significantly reduced on grazed hillslopes, likely due to depletion of surface Na in soils exposed to chronic soil disturbance by livestock. Variable selection and path analysis identified that biological soil crust (BSC) cover, more than any other variable, explained the differences in sediment yields between grazed and ungrazed watersheds, partially through the enhancement of soil aggregate stability. Our results suggest that BSC cover should be granted heightened consideration in rangeland decision support tools (e.g., state-and-transition models) and that measures to reduce surface disturbance from livestock such as altering the timing or intensity of grazing may be effective for reducing downstream impacts.

Climatic niche limits and community‐level vulnerability of obligate symbioses

AbstractAimCommunities with many species at their climatic niche limits may be vulnerable to species losses, suggesting that niche‐based measures can inform vulnerability assessments. We aimed to quantify spatial variation in community‐level vulnerability indices based on niche limits, not just central tendencies, to predict where climate changes will produce rapid, pronounced shifts in ecological communities.LocationNorth America.TaxonEpiphytic lichenized fungi.MethodsWe integrated broad‐extent herbarium data (46,343 North American sites, for estimation of realized niches) with systematic, whole‐community macrolichen surveys from the U.S. Forest Inventory and Analysis inventory (6,474 U.S. sites, for standardized vulnerability estimation). We introduce three niche‐based vulnerability indices describing (a) percentage of vulnerable species occurring at their upper climatic limits, (b) community‐mean percentile, and (c) deviation of local conditions from community‐mean upper limits. We also performed sensitivity analyses and evaluated vulnerability in future climate change scenarios.ResultsSensitivity of indices to uncertainty in climate variables was minor. Present‐day vulnerability was greatest in north‐central California, in the Southwest along the western Colorado Plateau, and on the Southeastern coastal plain—locations where climatically‐induced compositional changes will become most evident. Under future warming scenarios (+0.5 to + 3.6°C increases), the percentage of U.S. epiphytic macrolichen communities exceeding critical values grew from about 2%–20%.Main conclusionsIn all scenarios the most vulnerable communities were concentrated in low‐elevation and southerly locations, suggesting that many ostensibly “warm‐adapted” communities may be close to exceeding their climatic limits. Findings indicate that warming and moisture changes will modify community compositions through the local loss of intolerant species pushed beyond their niche limits. Assessing vulnerability of bioindicators such as lichens will help prioritize locations where the greatest climate‐induced changes in species distributions and diversity will occur.

Simulation of Sediment Flushing in Paonia Reservoir of Colorado

AbstractA one-dimensional sediment transport model (SRH-1D) was updated to simulate a sediment sluicing and flushing plan for the Paonia Reservoir, located on Muddy Creek in western Colorado. The P...

Genetic mark‐recapture analysis of winter faecal pellets allows estimation of population size in Sage Grouse Centrocercus urophasianus

The Sage Grouse Centrocercus urophasianus is a species of conservation concern throughout its range in western North America. Since the 1950s, the high count of males at leks has been used as an index for monitoring populations. However, the relationship between this lek‐count index and population size is unclear, and its reliability for assessing population trends has been questioned. We used non‐invasive genetic mark‐recapture analysis of faecal and feather samples to estimate pre‐breeding population size for the Parachute‐Piceance‐Roan, a small, geographically isolated population of Sage Grouse in western Colorado, during two consecutive winters from 2012 to 2014. We estimated total pre‐breeding population size as 335 (95% confidence interval (CI): 287–382) in the first winter and 745 (95% CI: 627–864) in the second, an approximate doubling in abundance between years. Although we also observed a large increase in the spring lek‐count index between those years, high male count data poorly represented mark‐recapture estimates of male abundance in each year. Our data suggest that lek counts are useful for detecting the direction and magnitude of large changes in Sage Grouse abundance over time but they may not reliably reflect small changes in abundance that may be relevant to small populations of conservation concern.

Passive processing of active nodal seismic data: estimation of <i>V</i><sub>P</sub>∕<i>V</i><sub>S</sub> ratios to characterize structure and hydrology of an alpine valley infill

Abstract. The advent of cable-free nodal arrays for conventional seismic reflection and refraction experiments is changing the acquisition style for active-source surveys. Instead of triggering short recording windows for each shot, the nodes are continuously recording over the entire acquisition period from the first to the last shot. The main benefit is a significant increase in geometrical and logistical flexibility. As a by-product, a significant amount of continuous data might also be collected. These data can be analyzed with passive seismic methods and therefore offer the possibility to complement subsurface characterization at marginal additional cost. We present data and results from a 2.4 km long active-source profile, which have recently been acquired in western Colorado (US) to characterize the structure and sedimentary infill of an over-deepened alpine valley. We show how the “leftover” passive data from the active-source acquisition can be processed towards a shear wave velocity model with seismic interferometry. The shear wave velocity model supports the structural interpretation of the active P-wave data, and the P-to-S-wave velocity ratio provides new insights into the nature and hydrological properties of the sedimentary infill. We discuss the benefits and limitations of our workflow and conclude with recommendations for the acquisition and processing of similar datasets.

Interactions between Resident Risk Perceptions and Wildfire Risk Mitigation: Evidence from Simultaneous Equations Modeling

Fire science emphasizes that mitigation actions on residential property, including structural hardening and maintaining defensible space, can reduce the risk of wildfire at a home. Accordingly, a rich body of social science literature investigates the determinants of wildfire risk mitigation behaviors of residents living in fire-prone areas. Here, we investigate relationships among wildfire hazards, residents’ risk perceptions, and conditions associated with mitigation actions using a combination of simulated wildfire conditions, household survey responses, and professionally assessed parcel characteristic data. We estimate a simultaneous model of these data that accounts for potential direct feedbacks between risk perceptions and parcel-level conditions. We also compare the use of self-reported versus assessed parcel-level data for estimating these relationships. Our analysis relies on paired survey and assessment data for approximately 2000 homes in western Colorado. Our simultaneous model demonstrates dual-directional interactions between risk perceptions and conditions associated with mitigation actions, with important implications for inference from simpler approaches. In addition to improving general understanding of decision-making about risk and natural hazards, our findings can support the effectiveness of publicly supported programs intended to encourage mitigation to reduce society’s overall wildfire risk.

Building integrated teams to address mental and behavioral health needs in rural primary care: The Western Colorado COEARTH project

The International Journal of Integrated Care (IJIC) is an online, open-access, peer-reviewed scientific journal that publishes original articles in the field of integrated care on a continuous basis.IJIC has an Impact Factor of 5.120 (2020 JCR, received in June 2021)

An introduced plant is associated with declines in terrestrial arthropods, but no change in stream invertebrates

Riverine systems often spread non-native species, yet the co-occurring impacts of introduced riparian vegetation on aquatic- and terrestrial-derived resources are unknown. We compared aquatic and terrestrial arthropod communities and their flux into and out of streams in riparian reaches invaded and uninvaded by Robinia neomexicana, a woody plant introduced to a western Colorado watershed. We found that invaded reaches had fewer terrestrial arthropods collected off foliage, conceivably because of the plant’s later leaf-out phenology. Overall, seasonal and annual factors best described terrestrial and aquatic arthropod communities. However, when we evaluated vegetation and stream characteristics in lieu of season and year, we found terrestrial arthropod biomass and richness were negatively related to cover of R. neomexicana and positively related to vegetative cover, forb cover, and vertical vegetation structure. Our results suggest ecosystems respond to landscape variation differently, where directly related food web components (i.e., terrestrial arthropods on introduced vegetation) respond stronger than more distally related constituents (i.e., aquatic insects).

P78 Lifestyle Medicine Intervention: Curbing Depression by Creating Food Pleasure

Background Lifestyle Medicine encompasses the adoption and maintenance of attitudes and behaviors that affect health and quality of life through diet and physical activity. Lack of motivation to eat healthier and be active is an issue commonly seen in our contemporary society. Objective This was a secondary data analysis of an interdisciplinary and evidence-based Lifestyle Medicine program to promote the adoption and sustainability of positive attitudes and behaviors towards nutrition. Study Design, Settings, and Participants Previously collected, de-identified data was obtained from a western Colorado hospital. This was an 18-week in-person program delivered by a multidisciplinary team of healthcare providers (MD, RDN, PT) that integrated nutrition education, cooking classes, and physical activity sessions to stimulate attitude and behavior change. The initiative aimed to improve employees' (n = 113) mental health and physical well-being by means of nutrition education. Measurable Outcome/Analysis Validated Patient Heath Questionnaires (PHQ-9) were taken pre- and post-program to determine changes in health mindset. Questionnaires were analyzed using paired t-tests and descriptive statistics. Results Scores from the PHQ-9 showed a significant decrease in mean scores (-3.32, P Conclusion Implementation of a comprehensive Lifestyle Medicine program by an interdisciplinary team may assist in reducing the severity and prevalence of a negative health mindset. Future research needs to be conducted to establish the impact of Lifestyle Medicine interventions in reducing an unhealthy way of thinking and stimulating food pleasure. Funding None.

Birth and evolution of the Virgin River fluvial system: ∼1 km of post–5 Ma uplift of the western Colorado Plateau

Birth and evolution of the Virgin River fluvial system: ∼1 km of post–5 Ma uplift of the western Colorado Plateau

High resolution linkage of channel-coastal plain and shallow marine facies belts, Desert Member to Lower Castlegate Sandstone stratigraphic interval, Book Cliffs, Utah-Colorado, USA

AbstractThe Campanian Desert Member and Lower Castlegate Sandstone in the Book Cliffs of east-central Utah to western Colorado, USA, has served as a foundational data set in the development of sequence stratigraphy. Contrary to previous work, no third-order sequence boundaries are recognized. These were originally thought to partition the neighboring coastal plain and shallow marine facies belts into separate systems tracts, unlinked in time or space. In contrast, adjoining channel-coastal plain and shallow marine facies belts are genetically-, temporally-, and spatially-related. Evidence includes the (i) synchronous, strongly progradational stacking patterns within each facies belt, (ii) gradational and conformable transitions between adjoining facies belts, accentuated by the ubiquity of flat-topped, rooted foreshore sandstones passing upwards into carbonaceous-rich-mudstone-dominated coastal plain, (iii) parasequence-scale interfingering of coastal plain-channel and foreshore-shoreface deposits, with channels, white caps and coals embedded within stacked shoreface parasequences, (iv) regional correlation of coals and flooding surfaces, and (v) near orthogonal paleocurrent relationship between channels and shorelines. Terminal channels incise into proximal foreshore-shoreface sandstones in most Desert-Castlegate parasequences. Incisions are generally confined to the parasequence in which the channels are nested, rarely cutting deeper. These shoreface-incised channels are cut and filled at a parasequence-scale, and are bounded above by the same flooding surface that caps each foreshore-shoreface package. The ubiquity of ascending regressive shoreface trajectories and near absence of descending regressive trajectories that intersect depositional slope argues against any significant sea level fall. Increased rates of sediment supply, driven by autogenic and/or allogenic processes, likely generated the strongly progradational Desert-Castlegate great tongue of sandstone.

Carbon Dioxide Concentrations and Efflux from Permanent, Semi-Permanent, and Temporary Subalpine Ponds

Small ponds account for a disproportionately high percentage of carbon dioxide emissions relative to their small surface area. It is therefore crucial to understand carbon flow in these ponds to refine the current global carbon budget, especially because climate change is affecting pond hydrology. High elevation ponds in the Elk Mountains of western Colorado are drying more frequently as the timing of snowmelt advances. We compared CO2 concentrations and fluxes among ponds of different hydroperiods over diel sampling periods during the course of the 2017 open-water period. CO2 concentrations were significantly negatively correlated with pond depth and averaged 77.6 ± 24.5 μmol L−1 (mean ± S.E.) across all ponds and sampling events. Ponds were up to twenty times supersaturated in CO2 with respect to the atmosphere. Flux was highly variable within individual ponds but correlated with time of sampling and was highest at night. Flux averaged 19.7 ± 18.8 mg CO2 m−2 h−1 across all ponds and sampling events. We also compared flux values obtained using modeled and empirical methods and found that widely-applied models of gas exchange rates using wind-based gas exchange (K) values yielded estimates of CO2 flux that were significantly higher than those obtained using the floating chamber approach, but estimates of CO2 flux using globally averaged convection-based K values were lower than those obtained using the floating chambers. Lastly, we integrated soil vs. water efflux measurements with long-term patterns in hydrology to predict how total season-long efflux might change under the more rapid drying regimes and longer seasons that are already occurring in these systems. Because soil CO2 efflux averaged 277.0 ± 49.0 mg CO2 m−2 h−1, temporary ponds emitted 674.1 ± 99.4 kg CO2 m−2 over the course of the 2017 season from ice-out to refreezing, which was over twice as much as permanent and semi-permanent ponds. Our results emphasize that contributions of CO2 from small ponds to the global carbon budget estimates will vary with pond hydroperiod and sampling methodology, which have been overlooked given that most previous estimates were collected from limited sampling periods and from pond waters alone. Furthermore, pond CO2 contributions are predicted to increase over time as pond areas transition from efflux from water to efflux from soil.

Preventive Fungicidal Control of Cytospora leucostoma in Peach Orchards in Colorado.

In western Colorado, Cytospora leucostoma is ubiquitous in peach orchards and has developed into a major limiting factor of peach production. The pathogen is unable to invade healthy intact phloem tissue of the tree, but instead, it requires a wound as a mode of entry. Bark injuries caused by cold and pruning in commercial orchard systems provide infection courts that, in suitable environment conditions, can lead to many successful fungal infections. Preventive fungicide control is an integral component of management in tree fruit production. Eighteen fungicides were tested at selected label dose rates for C. leucostoma control. All treatments were initially tested in vitro in fungicide-amended media dishes. Successful treatments were then tested under controlled conditions on detached peach branch segments. Effective fungicides identified in the laboratory assays (thiophanate-methyl, captan, lime sulfur, and copper hydroxide) were further tested as spray applications in the field and as wound sealant applications in combination with latex paint and kaolin clay. Of the treatments evaluated, thiophanate-methyl, captan, 50% latex paint, thiophanate-methyl amended in 50% latex paint, captan amended in 50% latex paint, and lime sulfur were most effective in reducing C. leucostoma necrotic area. Copper hydroxide was ineffective in all field trials and in some instances, yielded larger necrotic areas than the nontreated positive control shoots.

Pore-forming protein complexes from Pleurotus mushrooms kill western corn rootworm and Colorado potato beetle through targeting membrane ceramide phosphoethanolamine

Aegerolysins ostreolysin A (OlyA) and pleurotolysin A (PlyA), and pleurotolysin B (PlyB) with the membrane-attack-complex/perforin domain are proteins from the mushroom genus Pleurotus. Upon binding to sphingomyelin/cholesterol-enriched membranes, OlyA and PlyA can recruit PlyB to form multimeric bi-component transmembrane pores. Recently, Pleurotus aegerolysins OlyA, PlyA2 and erylysin A (EryA) were demonstrated to preferentially bind to artificial lipid membranes containing 50 mol% ceramide phosphoethanolamine (CPE), the main sphingolipid in invertebrate cell membranes. In this study, we demonstrate that OlyA6, PlyA2 and EryA bind to insect cells and to artificial lipid membranes with physiologically relevant CPE concentrations. Moreover, these aegerolysins permeabilize these membranes when combined with PlyB. These aegerolysin/PlyB complexes show selective toxicity toward western corn rootworm larvae and adults and Colorado potato beetle larvae. These data strongly suggest that these aegerolysin/PlyB complexes recognize CPE as their receptor molecule in the insect midgut. This mode of binding is different from those described for similar aegerolysin-based bacterial complexes, or other Bacillus thuringiensis Cry toxins, which have protein receptors. Targeting of Pleurotus aegerolysins to CPE and formation of transmembrane pores in concert with PlyB suggest the use of aegerolysin/PlyB complexes as novel biopesticides for the control of western corn rootworm and Colorado potato beetle.

Potential Spread of Cheatgrass and Other Invasive Species by Feral Horses in Western Colorado

The invasive grass cheatgrass (Bromus tectorum L.) presents major challenges for land management and habitat conservation in the western United States. Feral horses (Equus ferus caballus) have become overabundant in some areas of the West and can impact fragile semiarid ecosystems. Amid ongoing efforts to control cheatgrass in the Great Basin, we conducted a study to determine if feral horses contribute to the spread of cheatgrass through distribution via their feces. We collected feral horse fecal samples from Little Book Cliffs Herd Management Area in western Colorado in 2014. Fecal samples were dried, and 20 from each of 3 collection sessions were cultivated to examine germination success. Six species germinated from 18 samples (30%; mostly one plant per sample where germination occurred), including cheatgrass from 8% of samples. In a separate study we examined the diet of this same horse population using fecal plant DNA barcoding. Plant species that germinated were rare in the diet and germinated from fewer samples than expected relative to their detection in the diet. Our results suggest that feral horses could be contributing to cheatgrass propagation. Native ungulates and domestic cattle also have this potential. Although management of all large ungulates is necessary to mitigate cheatgrass spread, control of feral horse numbers is particularly necessary.

Measuring Desiccation Using Qualitative Changes: A Step Toward Determining Regional Decomposition Sequences.

The creation of a regional decomposition scoring system for western Colorado provides a model for the creation of regional systems. The development of a scoring system requires: (1) human remains, not proxies, (2) longitudinal observations, and (3) large sample size. First, an enhanced system (total body desiccation score; TBDS) was developed through observations of 40 human remains. This effort produced a categorical scoring model augmented by qualitative categories of gross tissue change. The new model was tested with retrospective photographic packets. A sample of eight donors with data collected over 3years was selected. Monthly data points over a maximum of a 3-year period yielded 112 data points. Correlations between TBDS and accumulated degree-days (ADD), and total body score (TBS) and ADD were approximately equal for a TBS below ~20, but the TBDS correlated better with ADD at higher TBS scores >20. The TBDS may be used to refine postmortem interval (PMI) models in areas where remains desiccate.

Post-fire vegetation communities in western Colorado

Post-fire vegetation communities in western Colorado

Climatology of Aerosol Optical Properties at Storm Peak Laboratory

ABSTRACT Aerosols create large uncertainty in the planetary energy balance due to both direct and indirect radiative forcing. Understanding aerosol seasonal patterns is essential for accurate climate change prediction, but mountain regions are often difficult for climate models to resolve. Therefore, long-term observations collected at high elevations are particularly useful. In-situ surface aerosol optical measurements were analyzed for the years 2011–2016 at a mountain site located in western Colorado and tied to potential sources based on relationships among the aerosol properties. The peak values for the scattering and absorption coefficients were observed during the summer, suggesting greater aerosol loading (likely due to wildfires), whereas the lowest values were observed during the winter, indicating cleaner conditions (due to less influence from the boundary layer). The scattering Angstrom exponent, a property that provides information about size distributions, revealed the predominance of coarse-mode particles during the spring, which is consistent with the presence of dust. The aerosols observed during the summer, however, were mostly composed of fine-mode particles. This increase in the fine fraction points to combustion, likely wildfires during the dry season (Hallar, 2015), as a source, which is further supported by the absorption Angstrom exponent dropping to its lowest value (close to 1) during the summer after exhibiting a slightly higher value (~1.3) during the spring. Schmeisser et al. (2017) suggests that, for in-situ aerosol, absorption Angstrom exponents larger than 1.5 may be indicative of dust if they are associated with low (< 1.3) scattering Angstrom exponents. The increase in combustion aerosols during the summer accompanied by high values for the single scattering albedo suggests that these aerosols underwent processing in the atmosphere before reaching Storm Peak Laboratory. These results are important for improving visibility and predicting future aerosol concentrations in the western U.S.

Re-evaluating the sedimentology and sequence stratigraphy of classic Book Cliffs outcrops at Tusher and Thompson canyons, eastern Utah, USA: Applications to correlation, modelling, and prediction in similar nearshore terrestrial to shallow marine subsurface settings worldwide

Abstract The Campanian Book Cliffs strata of eastern Utah and western Colorado has been used to develop, test and refine sedimentological and stratigraphic ideas and models over the years, including the principles and concepts of sequence stratigraphy. Book Cliffs data sets are often used as outcrop analogues for similar subsurface settings worldwide. Thousands of geologists have visited the Book Cliffs, including the archetypal Desert Member-to-Lower Castlegate Sandstone outcrops at Tusher and Thompson canyons, which are the focus of this study. These localities regularly serve as representative field stops for teaching sequence stratigraphy. Recent work has begun to cast doubt on certain aspects of the conventional sequence stratigraphic interpretation of the Desert-Castlegate interval, hence re-evaluation of these classic outcrops is warranted. A progradational stack of shallow marine to nearshore terrestrial facies are observed at Tusher Canyon. From bottom to top these include shelf mudstones, lower shoreface-to-inner shelf heterolithics, foreshore-to-upper shoreface sandstones cut by distributary and tidal-estuarine channels, coal-bearing coastal plain mudstones with single-storey fluvial sandstones, amalgamated multi-storey fluvial channel-fills, and a capping coastal plain mudstone package overlain by the marine mudstones of the Buck Tongue of the Mancos Shale. A similar progradationally-stacked facies succession is observed 30 km basinwards at Thompson Canyon, with the exception of the proximal amalgamated fluvial sandstone package, which is absent. Five of eleven Desert Member parasequences, D1 to D5, are noted at Tusher Canyon, while all eleven Desert parasequences, D1 to D11 and two of six Castlegate parasequences, C1 and C2, are identified at Thompson Canyon. Although parasequences and their flooding surfaces can be correlated between Tusher and Thompson canyons, the discrete shoreface-incised channels are only restricted to the proximal portions of each parasequence. These channels mostly cut foreshore-shoreface sandstones, and are not continuously correlatable between Tusher and Thompson canyons. Re-examination of these Desert-Castlegate outcrops exemplifies the misfit with the conventional sequence stratigraphic model, specifically the miscorrelation of the D5 and D11 shoreface-incised channels. Over 60 m of deposits separate the D5 and D11 horizons along 30 km of dip-oriented outcrop between Tusher and Thompson canyons. Contrary to earlier interpretations, the shoreface-incised channels in the Desert-Castlegate are not nested within larger incised valley-fills. An alternative model showing temporal and spatial linkage between the nearshore terrestrial and laterally adjoining shallow marine facies is the best fit with the Desert-Castlegate field observations. Selecting the appropriate correlation style has significant implications for the prediction of sand body continuity, connectivity and distribution, especially applications to subsurface data sets where visualization is limited and correlation uncertainties are high.

Integrating Results of Field Biomonitoring and Mesocosm Experiments To Validate Postspill Impacts of Petroleum Hydrocarbons on Stream Benthic Communities.

We integrated the results of field surveys with a mesocosm experiment to quantify the ecological impacts of a gasoline and diesel spill on a third-order stream in western Colorado (United States). The spill caused a massive fish-kill of brown trout ( Salmo trutta) and mottled sculpin ( Cottus bairdii), which extended several kilometers downstream. Despite significant decreases in petroleum hydrocarbon concentrations, subsequent surveys indicated little recovery of fish populations 4 years after the spill. Benthic macroinvertebrate communities were also affected, yet some metrics commonly used to assess stream ecological integrity (e.g., total abundance and species richness) showed no difference between impacted and reference sites. The failure of some groups to recover 2.5 years after the spill was likely a result of their comparatively slow reproduction and recolonization rates. To support our hypothesis that effects observed in the field resulted from petroleum exposure, we conducted a mesocosm experiment in which benthic macroinvertebrate communities were exposed to a simulated diesel spill. We observed significant decreases in the abundance of most macroinvertebrate groups at the lowest exposure concentration (75 mg/L diesel) and a strong concentration-dependent drift response across all groups. Our study suggests that relatively small petroleum spills can significantly affect stream communities, and these effects may persist several years after sediment concentrations return to background levels.