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At least 1,207 records · Page 67Linked to original sources

USGS2001

Ramet spacing of Elymus lanceolatus (thickspike wheatgrass) in response to neighbour density

Many plants exploit patchy resources through clonal foraging. Plants established in field plots were used to determine if Elymus lanceolatus ssp. lanceolatus (Scribner et J.G. Smith) Gould (thickspike wheatgrass) showed a clonal foraging response to neighbour densities, as it had previously shown to patchy soil nutrients. Neighbours consisted of the rhizomatous E. lanceolatus ssp. lanceolatus and the bunchgrass Elymus lanceolatus ssp. wawawaiensis (Scribner et Gould) J.R. Carlson et D.R. Dewey (proposed name), which are both native to the semiarid western U.S.A., and their ratios as well as total densities varied. Rather than an increase in spacing of exploratory ramets at high densities, as expected with clonal foraging, there was a decrease in spacing in both years of the experiment. Fewer target plants produced exploratory ramets at higher densities only in the second year. These reductions in exploratory clonal growth at higher neighbour densities, which were opposite to E . lanceolatus ssp. lanceolatus ' response to low-resource patches, occurred perhaps because soil resource levels were too low overall to support rhizome production, and this condition was more pronounced in the second year. Physical resistance from neighbour roots perhaps also reduced rhizome production. However, rhizome growth may not be beneficial in such cases, and plants may be adapted to produce exploratory rhizomes only when some high-resource patches are encountered by the clone.

Canadian Journal of Botany↗

USGS2011

Enhanced decomposition offsets enhanced productivity and soil carbon accumulation in coastal wetlands responding to climate change

Coastal wetlands are responsible for about half of all carbon burial in oceans, and their persistence as a valuable ecosystem depends largely on the ability to accumulate organic material at rates equivalent to relative sea level rise. Recent work suggests that 5 elevated CO2 and temperature warming will increase organic matter productivity and the ability of marshes to survive sea level rise. However, we find that organic decomposition rates increase by about 12% per degree of warming. Our measured temperature sensitivity is similar to studies from terrestrial systems, twice as high as the response of salt marsh productivity to temperature warming, and roughly equivalent to the productivity response associated with elevated CO2 10 in C3 marsh plants. Therefore, enhanced CO2 and warmer temperatures may actually make marshes less resilient to sea level rise, and tend to promote a release of soil carbon. Simple projections indicate that elevated temperatures will increase rates of sea level rise more than any acceleration in organic matter accumulation, suggesting the possibility of a positive feedback between 15 climate, sea level rise, and carbon emissions in coastal environment

Biogeosciences Discussions↗

USGS2016

Conditional vulnerability of plant diversity to atmospheric nitrogen deposition across the United States

Atmospheric nitrogen (N) deposition has been shown to decrease plant species richness along regional deposition gradients in Europe and in experimental manipulations. However, the general response of species richness to N deposition across different vegetation types, soil conditions, and climates remains largely unknown even though responses may be contingent on these environmental factors. We assessed the effect of N deposition on herbaceous richness for 15,136 forest, woodland, shrubland, and grassland sites across the continental United States, to address how edaphic and climatic conditions altered vulnerability to this stressor. In our dataset, with N deposition ranging from 1 to 19 kg N⋅ha−1⋅y−1, we found a unimodal relationship; richness increased at low deposition levels and decreased above 8.7 and 13.4 kg N⋅ha−1⋅y−1 in open and closed-canopy vegetation, respectively. N deposition exceeded critical loads for loss of plant species richness in 24% of 15,136 sites examined nationwide. There were negative relationships between species richness and N deposition in 36% of 44 community gradients. Vulnerability to N deposition was consistently higher in more acidic soils whereas the moderating roles of temperature and precipitation varied across scales. We demonstrate here that negative relationships between N deposition and species richness are common, albeit not universal, and that fine-scale processes can moderate vegetation responses to N deposition. Our results highlight the importance of contingent factors when estimating ecosystem vulnerability to N deposition and suggest that N deposition is affecting species richness in forested and nonforested systems across much of the continental United States.

PNAS↗

USGS2019

Biocrust science and global change

Global environmental changes such as climate and land‐use change affect ecosystems worldwide, and this New Phytologist Virtual Issue brings together fundamental research questions and novel approaches associated with the study of biological soil crusts in the context of such shifts. In a changing world, organisms can display a limited set of responses that will determine their persistence over varied spatial and temporal scales. Specifically, organisms might tolerate the change – for example, via phenotypic plasticity – and remain present in local communities. Alternatively, organisms might shift or retract their range to match their historical niche, they may adapt to the directional selection pressures imposed by change, or they could be driven to local (and possibly global) extinction. Efforts to understand which of these responses particular plant species or assemblages will exhibit are necessary for predicting changes in ecosystem functioning and trophic interactions under global change scenarios, and for managing and supporting sustainable terrestrial ecosystems. Accordingly, the assessment of plant responses to global change has become a significant research focus. Despite this impressive effort, our understanding and combined work to measure the responses to global change for species and communities of nonvascular autotrophs, such as the cyanobacteria, lichens, and bryophytes that form biological soil crusts (Fig. 1), remain rare compared with the large focus on vascular plants (Fig. 2; Reed et al., 2016). Nevertheless, these nonvascular photosynthetic communities and their responses to change could have critical implications for determining ecosystem structure and function at the global‐scale (Elbert et al., 2012; Ferrenberg et al., 2017; Rodriguez‐Caballero et al., 2018).

New Phytologist↗

USGS2022

Decline in biological soil crust N-fixing lichens linked to increasing summertime temperatures

Across many global drylands, biocrusts form a protective barrier on the soil surface and fill many critical roles in these harsh yet fragile environments. Previous short-term research suggests that climate change and invasive plant introduction can damage and alter biocrust communities, yet few long-term observations exist. Using a globally unique long-term record of continuous biocrust surveys from a rare never-grazed, protected grassland on the US Colorado Plateau, we found lichen species diversity and cover to be negatively correlated with increasing summer air temperatures, while moss species showed more sensitivity to variation in precipitation and invasive grass cover. These results suggest that dryland systems may be at a critical tipping point where ongoing warming could result in biological soil crust degradation.

Proceedings of the National Academies of Science (↗

USGS2020

Emerging and historical contaminants detected in desert rodents collected near a low‐level radioactive waste site

In an effort to determine contaminant presence, concentrations, and movement from a low‐level radioactive waste (LLRW) burial disposal site to ecosystems in the surrounding area, a study was developed to assess concentrations of per‐ and polyfluoroalkyl substances (PFAS), polychlorinated biphenyls (PCBs), and tritium. To complete this assessment small mammals, vegetation, soil, and insect samples were collected from areas within and adjacent to the Beatty, Nevada, LLRW site and from a reference area located approximately 3 km south of the LLRW site. Samples underwent analysis via liquid chromatography tandem mass spectrometry, gas chromatography mass spectrometry, or scintillation spectroscopy depending on the analyte of interest. Small mammal tissues showed maximum concentrations of over 1700 ng/g for PFAS, 1600 ng/g for PCBs, and 10 000 Bq/kg for tritium. The primary contaminants found in soil samples were PCBs, with maximum concentrations exceeding 25 ng/g. Trace amounts of PFAS were also detected in soils and insects. Only qualitative data were obtained from vegetation samples because of the complex matrix of the dominant plant species (creosote bush; Larrea tridentata [Sessé & Moc. ex DC.] Coville). Overall, these data indicate the presence of various anthropogenic contaminants in the ecosystem surrounding the LLRW area, but additional analyses are necessary to confirm the sources and migration pathways of PFAS and PCBs in this hyperarid environment. Environ Toxicol Chem 2020;00:1–8. © 2020 SETAC

Nevada↗

USGS2011

Vegetation index-based crop coefficients to estimate evapotranspiration by remote sensing in agricultural and natural ecosystems

Crop coefficients were developed to determine crop water needs based on the evapotranspiration (ET) of a reference crop under a given set of meteorological conditions. Starting in the 1980s, crop coefficients developed through lysimeter studies or set by expert opinion began to be supplemented by remotely sensed vegetation indices (VI) that measured the actual status of the crop on a field-by-field basis. VIs measure the density of green foliage based on the reflectance of visible and near infrared (NIR) light from the canopy, and are highly correlated with plant physiological processes that depend on light absorption by a canopy such as ET and photosynthesis. Reflectance-based crop coefficients have now been developed for numerous individual crops, including corn, wheat, alfalfa, cotton, potato, sugar beet, vegetables, grapes and orchard crops. Other research has shown that VIs can be used to predict ET over fields of mixed crops, allowing them to be used to monitor ET over entire irrigation districts. VI-based crop coefficients can help reduce agricultural water use by matching irrigation rates to the actual water needs of a crop as it grows instead of to a modeled crop growing under optimal conditions. Recently, the concept has been applied to natural ecosystems at the local, regional and continental scales of measurement, using time-series satellite data from the MODIS sensors on the Terra satellite. VIs or other visible-NIR band algorithms are combined with meteorological data to predict ET in numerous biome types, from deserts, to arctic tundra, to tropical rainforests. These methods often closely match ET measured on the ground at the global FluxNet array of eddy covariance moisture and carbon flux towers. The primary advantage of VI methods for estimating ET is that transpiration is closely related to radiation absorbed by the plant canopy, which is closely related to VIs. The primary disadvantage is that they cannot capture stress effects or soil evaporation. Copyright ?? 2011 John Wiley & Sons, Ltd.

Hydrological Processes↗

USGS2016

Conversion of native terrestrial ecosystems in Hawai‘i to novel grazing systems: a review

The remote oceanic islands of Hawai‘i exemplify the transformative effects that non-native herbivorous mammals can bring to isolated terrestrial ecosystems. We reviewed published literature containing systematically collected, analyzed, and peer-reviewed original data specifically addressing direct effects of non-native hoofed mammals (ungulates) on terrestrial ecosystems, and indirect effects and interactions on ecosystem processes in Hawai‘i. The effects of ungulates on native vegetation and ecosystems were addressed in 58 original studies and mostly showed strong short-term regeneration of dominant native trees and understory ferns after ungulate removal, but unassisted recovery was dependent on the extent of previous degradation. Ungulates were associated with herbivory, bark-stripping, disturbance by hoof action, soil erosion, enhanced nutrient cycling from the interaction of herbivory and grasses, and increased pyrogenicity and competition between native plants and pasture grasses. No studies demonstrated that ungulates benefitted native ecosystems except in short-term fire-risk reduction. However, non-native plants became problematic and continued to proliferate after release from herbivory, including at least 11 species of non-native pasture grasses that had become established prior to ungulate removal. Competition from non-native grasses inhibited native species regeneration where degradation was extensive. These processes have created novel grazing systems which, in some cases, have irreversibly altered Hawaii’s terrestrial ecology. Non-native plant control and outplanting of rarer native species will be necessary for recovery where degradation has been extensive. Lack of unassisted recovery in some locations should not be construed as a reason to not attempt restoration of other ecosystems.

Biological Invasions↗

USGS1986

15N-NMR INVESTIGATION OF HYDROXYLAMINE DERIVATIZED HUMIC SUBSTANCES.

Humic substances are the most abundant naturally occurring refactory organic compounds in soils and water. They have a broad range of physical, chemical and physiological properties. In soils, humic substances contribute to the cation exchange capacity, help maintain the physical structure, and play a role in plant growth and nutrition. In aquatic systems, humic substances serve to regulate the levels of inorganic constituents, yield trihalomethanes upon chlorination, and transport or concentrate organic and inorganic pollutants. The oxygen containing functional groups of humic and fulvic acids are believed to play a key role in the chemical properties of humic substances. This study was undertaken to gain additional information on the specific types of oxygen functionalities in humic substances. Since the analysis of hydroxyl moieties had been earlier established, we focused our attention on the analysis of ketone and aldehyde functional groups in humic substances.

Conference Paper↗

USGS2001

Methanogenic biodegradation of charcoal production wastes in groundwater at Kingsford, Michigan, USA

A house exploded in the City of Kingsford, Michigan USA. The explosion was caused by CH4 that leaked into the basement from the surrounding soil. Evidence suggests that biodegradation of products from the distillation and spillage at or near a former wood carbonization plant site was the major source of CH4 and CO2 in the groundwater system. The plant area is directly upgradient from deep groundwater, samples of which are green-yellow in colour, have a very strong odour of burnt wood, contain high concentrations of mononuclear aromatic and phenolic compounds, and extremely high concentrations of volatile fatty acids. The majority of the dissolved compounds in these groundwater samples have been shown, using laboratory microcosms, to be anaerobically biodegradable to CH4 and CO2. The biodegradable compounds, and the amounts of CH4 and CO2 produced in the microcosms, are consistent with observations from field samples.

Michigan↗

USGS1991

Sensitivity of desert cryptograms to air pollutants: soil crusts and rock lichens

Parks throughout the West are being faced with increasing air pollution threats from current or proposed industries near their boundaries. For this reason, it is important to understand the effects these industries may have on desert ecosystems. Rock lichens can be excellent biomonitors, acting as early warning systems of impending damage to other components of the desert ecosystem. Cryptogamic crusts, consisting mostly of cyanobacteria and lichens, may not only be excellent bioindicators, but also are an essential part of the desert ecosystem. Their presence is critical for soil stability as well as for the contribution of nitrogen to the ecosystem in a form available to higher plants. Air pollutants, such as emissions from coal-fired power plants, may threaten the healthy functioning of these non-vascular plants. The purpose of this study is to determine if, in fact, air pollutants do have an impact on the physiological functioning of cryptogamic crusts or rock lichens in desert systems and, if so, to what extent. Some results have already been obtained. Both rock lichens and cryptogamic crusts exhibit physiological damage in the vicinity of the Navajo Generating Station in Page, Arizona. Increased electrolyte leakage and chlorophyll degradation, along with reduced nitrogen fixation, have been found. Preliminary studies comparing sensitivity between substrates indicate that crusts on limestone and sandstone substrates may be more sensitive than those on gypsum.

Report↗

USGS2017

Holistic assessment of occurrence and fate of metolachlor within environmental compartments of agricultural watersheds

Background : Metolachlor [(RS)-2-Chloro- N -(2-ethyl-6-methyl-phenyl)- N -(1-methoxypropan-2-yl)acetamide] and two degradates (metolachlor ethane-sulfonic acid and metolachlor oxanilic acid) are commonly observed in surface and groundwater. The behavior and fate of these compounds were examined over a 12-year period in seven agricultural watersheds in the United States. They were quantified in air, rain, streams, overland flow, groundwater, soil water, subsurface drain water, and water at the stream/groundwater interface. The compounds were frequently detected in surface and groundwater associated with agricultural areas. A mass budget approach, based on all available data from the study and literature, was used to determine a percentage-wise generalized distribution and fate of applied parent metolachlor in typical agricultural environments. Results : In these watersheds, about 90% of applied metolachlor was taken up by plants or degraded, 10% volatilized, and 0.3% returned as rainfall. One percent was transported to surface water, while an equal amount infiltrated into the unsaturated zone soil water. < 0.02% reached the groundwater. Subsurface flow paths resulted in greater degradation of metolachlor because degradation reactions had more time to proceed. Conclusions : An understanding of the residence times of water in the different environmental compartments, and the important processes affecting metolachlor as it is transported along flowpaths among the environmental compartments allows for a degree of predictability of metolachlor's fate. Degradates with long half-lives can be used (in a limited capacity) as tracers of metolachlor, because of their persistence and widespread occurrence in the environment.

Science of the Total Environment↗

USGS1998

Effects of nutrient patches and root systems on the clonal plasticity of a rhizomatous grass

Clonal plant foraging has been examined primarily on individual clones exposed to resource-poor and resource-rich environments. We designed an experiment to examine the clonal foraging behavior of the rhizomatous grass Elymus lanceolatus ssp. lanceolatus under the influence of neighboring plant root systems in a heterogeneous nutrient environment. Individual Elymus clones were planted in large bins together with one of three neighboring grass species, Agropyron desertorum, Pseudoroegneria spicata, or Bromus tectorum, which differ in rooting density and growth activity. The position of Elymus clones was manipulated so rhizomes encountered a short-duration nutrient patch and subsequently root systems of the neighboring plants. Unexpectedly, the morphological plasticity of the perennial grass Elymus lanceolatus ssp. lanceolatus was influenced by the presence of the neighboring species much more than by the local nutrient enrichments, although nutrient patches did amplify some of the foraging responses. Elymus rhizomes branched readily and initiated large daughter plants as they encountered the low-density root systems of Pseudoroegneria. When Elymus encountered the fine, dense root systems of the annual Bromus, clonal expansion was initially reduced. Yet, after the short growing season of Bromus, Elymus resumed clonal expansion and produced several daughter plants. Elymus clones were most constrained by the fine, dense root systems of Agropyron desertorum. In this case, a few, long rhizomes avoided the densely rooted soil environment by growing aboveground as stolons crossing over the Agropyron tussocks. Elymus clonal biomass was largest in neighborhoods of Pseudoroegneria, intermediate in neighborhoods with Bromus, and smallest in neighborhoods with Agropyron. The latter were approximately half the size of those in the Pseudoroegneria environments. Elymus growth could not be explained by simple resource competition alone; other mechanisms must have been involved in the apparent differences in interference patterns of neighboring plants with Elymus.

Ecology↗

USGS2022

Sources and characteristics of dissolved organic carbon in the McKenzie River, Oregon, related to the formation of disinfection by-products in treated drinking water

Executive Summary This study characterized the concentration and quality of dissolved organic carbon (DOC) in the McKenzie River, a relatively undeveloped watershed in western Oregon, and its link to forming disinfection by-products (DBPs) in treated drinking water. The study aimed to identify the primary source(s) of DOC in source water for the Eugene Water & Electric Board’s (EWEB) conventional treatment plant on the McKenzie River near river mile 11, upstream of Hayden Bridge. The two classes of regulated compounds examined—trihalomethanes (THMs) and haloacetic acids (HAAs)—form when organic carbon in raw source water reacts with chlorine and (or) bromine during water treatment. The objectives of the study were to: characterize the amount and quality of DOC in the McKenzie River and select tributaries during storms; identify the most common types of carbon using UV-vis spectroscopy and other methods; evaluate optical properties for predicting DBP precursors in surface water; and identify land cover classes or vegetation types that may be important sources of organic carbon and DBP precursors in EWEB’s source water. Eleven storms were sampled synoptically in upstream-to-downstream fashion to provide a “snapshot” of water quality conditions at four sites on the McKenzie River from Frissell Bridge (6 miles downstream from Trail Bridge Reservoir) to the EWEB water treatment plant at Hayden Bridge and nine contributing tributaries. Storms included late summer and early autumn “first flush” events and late autumn, winter, and spring storms spanning a range in streamflows from 3,000 to 26,000 cubic feet per second as measured in the main stem McKenzie River at the EWEB water intake. Water samples were analyzed for DOC concentrations and optical properties (fluorescence and ultraviolet absorbance [UVA]) across a range of wavelengths to characterize the quantity and quality of dissolved organic matter (DOM) in the McKenzie River at the drinking water intake and upstream locations. Paired sets of source and finished water samples were collected at the EWEB treatment plant to identify DOC quality parameters in raw source water that might predict DBP concentrations in finished drinking water. DOC concentrations were relatively low in the McKenzie River (0.4–3 milligrams per liter [mg/L]; average 1.5 mg/L) but much higher in the tributaries. The highest DOC concentrations occurred during “first flush” storms in October 2012 and September 2013; the highest value (16 mg/L) was measured at the 52nd Street stormwater outfall. The average DOC concentration in the lower basin-tributaries was 3.8 mg/L; three middle basin tributaries—Quartz, Gate, and Haagen Creeks, which drain private forestland with less coniferous forest compared with other higher elevation tributaries— had slightly lower average DOC concentrations (2.8 mg/L). These middle-basin watersheds may be important sources of DOC and DBP precursors to the McKenzie River, even more so than the lower basin tributaries, depending on their flows (and loads). This is particularly true after the September 2020 Holiday Farm fire, which burned much of this area. DOC concentrations increased 68 percent in the McKenzie River between the uppermost reference site at Frissell Bridge and Vida; this includes drainage from Quartz Creek, Blue River Lake and Cougar Reservoir, which all contributed DOC to the main stem. In contrast, the lowermost tributaries draining most of the agricultural and urban land did not have a large effect on DOC in the McKenzie River despite their higher DOC concentrations because of their presumed relatively low streamflows and, consequently, DOC loads. Apart from the continuous flow monitors in the McKenzie River and some tributaries (Blue River and South Fork McKenzie River, and streamflow at Hayden Bridge and Vida, Camp Creek and some other locations), streamflow was not assessed during sample collection for this study. This lack of streamflow data precludes a detailed analysis of loads, which is discussed in the future studies section. All DBP concentrations in finished drinking water were less than EPA maximum contaminant levels (MCLs) of 0.080 mg/L for the four trihalomethanes (THM4) and 0.060 mg/L for five haloacetic acids (HAA5). During the 11 storm sampling events the maximum summed concentrations were about 0.040 mg/L for both THM4 and HAA5. Compliance monitoring samples, collected separately by EWEB, yielded some higher concentrations—0.046 mg/L THM4 and 0.047 HAA5—during the December 2012 storm. The corresponding benchmark quotient (BQ) values, which indicate how close a measured DBP concentration is to the MCL, were 0.58 and 0.78, respectively, for THM4 and HAA5. Compared with a similar 2007–08 McKenzie River study that did not target storm events, concentrations of THM4 and HAA5 in finished water were 68 percent and 33 percent higher, respectively, during the current study. Due to the high dilution rates in the McKenzie River main stem, many of the individual fluorescence excitation-emission measurements were low (<0.1 Raman units) and approached analytical detection limits. Parallel factor analysis (PARAFAC) resulted in a five-component model (C1–C5) that represents five unique organic fluorophores. Components C1, C2, and C3 represent DOM associated with soil-derived, humic-like, more degraded organic matter. In contrast, components C4 and C5 represent “fresher” DOM, derived from terrestrial and aquatic plants, including algae and cyanobacteria that are common in the McKenzie River and its tributaries and reservoirs. The fluorescence data and PARAFAC modeling suggest that most of the DOC in the McKenzie River originated from terrestrial sources (primarily components C1 and C2). The largest increases in DOC in the main stem occurred in the reach upstream of Vida, from inflows by Quartz Creek, Blue River, South Fork McKenzie River, and other tributaries. Concentrations of DBPs in EWEB’s finished drinking water were positively correlated with DOC concentrations in raw source water (THM4, p <0.05; HAA5, p <0.01) for paired samples collected 12−24 hours apart. DOC concentrations were significantly positively correlated ( p <0.001) with laboratory-based fluorescent dissolved organic matter (fDOM) measurements, suggesting fDOM as a useful parameter for monitoring and predicting DOC concentration in surface water and DBP concentrations in finished water. Of all the PARAFAC components in surface water, C5 had the highest correlations with DBPs in finished water (rho = 0.77–0.84, p <0.01), followed by components C1 and C2 (rho = 0.75 and 0.71, respectively, p <0.01). This C5 carbon is associated with recently produced DOM, possibly from decomposed terrestrial and aquatic vegetation. Model loadings of these three components were considerably higher in the sampled tributaries relative to the main stem McKenzie River, with most of the observed increases in the main stem apparent at Vida. This points to Quartz Creek or other tributaries in the reach between Frissell Bridge and the sampling site near Vida (South Fork McKenzie and Blue Rivers) as potentially key contributors of DOM source material that leads to the production of DBPs in treated drinking water. A limited load analysis showed that the reservoirs contributed 8–37 percent of the instantaneous DOC loads observed at Vida at the time of sampling, which suggests other sources such as Quartz Creek and other streams in the reach between Frissell Bridge and Vida are more important. Random forest analyses identified PARAFAC components C1 and C5 and fluorescence peaks A, C, M, T and N as the best predictors for HAA5 concentrations in finished drinking water, explaining 62.5 percent of the variation. The best predictors for THM4 were C1, C4 + C5, and peaks T, A, and N, which explained 33 percent of the variation. Several land cover and vegetation classes were correlated with DOC concentration and other optical measurements. The percentage of evergreen forest in each of the subwatersheds sampled was negatively correlated ( p <0.001) with DOC concentration and many optical indicators of DOM quantity: UVA 254 , fDOM, and all of the fluorescence peaks. In contrast, mixed (deciduous) forest was positively correlated ( p <0.001) with DOC, fDOM, UVA 254 , and several fluorescence peaks, demonstrating the importance of deciduous leaf fall in generating DOC and DBP precursors. The high level of human activities in the middle and lower portion of the basin—including timber harvesting and road construction on private forestland, agricultural, rural, industrial, and urban development—have resulted in the greatest loss in native coniferous and mixed deciduous forests in the basin. DOC loading from these tributaries and reservoir releases, which contain DOC from terrestrial and aquatic productivity, both enrich the McKenzie River. Concentrations of DOC increased an average of 71 percent (range 30–120 percent) in the McKenzie River between Frissell Bridge, the upstream reference site, and Vida. PARAFAC components C1, C2, and C5—which were correlated with DBPs in finished water—increased, on average, 109–136 percent (range 20–250 percent) in this same Frissell-to-Vida reach. These increases occur from input of tributaries in the middle basin such as Quartz Creek and others, as noted above. Future monitoring, field, and lab studies can improve our understanding of seasonal and spatial sources of organic carbon contributing DBP precursors to the McKenzie River and allow detection of long-term trends resulting from the recent Holiday Farm Fire, which burned 173,393 acres of forestland, including riparian areas along the main stem, and numerous structures, homes, and outbuildings in September 2020. Future studies could examine DOC fluxes and flushing of carbon from the watershed, investigate the role of precipitation amount and intensity in mobilizing carbon and sediment, and evaluate impacts to aquatic communities and human health as part of a post-fire assessment. Other areas ripe for study include evaluating the impacts of potential temperature increases on carbon sequestration and decomposition in the burned and unburned forests and identifying practices that foster sequestration of carbon in forest soils. The use of fluorescence sensors such as fDOM to monitor the concentration and composition of raw water supplies may be improved for detection of specific DBP precursors, to provide continuous and real-time information to treatment plant operators. Future studies that monitor DOM amount and quality, and DBP Formation Potential (FP), particularly during storm events, paired with streamflow measurements, as suggested above, could help identify areas that contribute high DOC loads and thus help managers identify the key areas to focus restoration activities. Other studies could examine treatment options for currently regulated DBPs and potentially unregulated compounds, including advanced biological treatments for their removal. This study was a collaboration between the U.S. Geological Survey (USGS) and EWEB in Eugene, Oregon, with additional funding provided from USGS Cooperative Matching Funds Program.

Oregon↗

USGS2006

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3-4 m) in dune-crest and dune-swale settings. Magnetite abundance also correlates strongly and positively with abundances of other elements (e.g., Ti, Li, As, Th, La, and Sc) that are geochemically stable in these environments. Soil-property variations with depth can be ascribed to three primary factors: (1) shifts in local geomorphic setting; (2) accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land-surface stability; and (3) variations in dust flux and composition that are likely related to changes in dust-source regions. Shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties. Variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic, chemical, and textural properties. The largest of these changes is found in sediment that spans late Pleistocene to early Holocene time. Increased dust inputs to the central Colorado Plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western North America that exposed vast surfaces capable of emitting dust. Soil properties that result from variable dust accumulation and redistribution in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12-15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity.

Catena↗

USGS2017

Natural resource inventory and monitoring for Ulaan Taiga Specially Protected Areas—An assessment of needs and opportunities in northern Mongolia

Between 1997 and 2011, Mongolia established three specially protected areas in the north-central part of the country to protect various high-value resources. These areas are jointly referred to as the Ulaan Taiga Specially Protected Areas. In accordance with the goals of the draft general management plan, this report identifies options for initiating an inventory and monitoring program for the three protected areas. Together, the three areas comprise over 1.5 million hectares of mountainous terrain west of Lake Hovsgol and bordering the Darkhad Valley. The area supports numerous rare ungulates, endangered fish, and over 40 species of threatened plants. Illegal mining, illegal logging, and poaching pose the most immediate threats to resources. As a first step, a review of published literature would inform natural resource management at the Ulaan Taiga Specially Protected Areas because it would inform other inventories. Vegetation classification and mapping also would inform other inventory efforts because the process incorporates geographic analysis to identify environmental gradients, fine-scale sampling that captures species composition and structure, and landscape-scale results that represent the variety and extent of habitats for various organisms. Mapping using satellite imagery reduces the cost per hectare. Following a determination of existing knowledge, field surveys of vertebrates and vascular plants would serve to build species lists and fill in gaps in existing knowledge. For abiotic resources, a focus on monitoring air quality, evaluating and monitoring water quality, and assembling and storing weather data would provide information for correlating resource response status with changing environmental conditions. Finally, we identify datasets that, if incorporated into a geographic information system, would inform resource management. They include political boundaries, infrastructure, topography, surficial geology, hydrology, fire history, and soils. In terms of tracking high-value resources, vegetation monitoring at the plot scale would provide a basis for detecting change in such characteristics as plant species composition, vegetation structure, and productivity that are associated with landscape-scale factors such as climate change or biotic interactions. Continued population monitoring of rare ungulates, particularly argali or wild sheep ( Ovis ammon ), would provide information on how populations are responding to natural and anthropogenic stressors. Siberian taimen ( Hucho taimen ) also is an important monitoring target given ongoing threats of poaching and climate change.

Ulaan Taiga Specially Protected Areas↗

USGS1997

The influence of vines on an oligohaline marsh community: Results of a removal and fertilization study

The effects of competitive suppression by vines on the non-vine plant community have received little attention in temperate habitats. This study investigated the impact vines have on their herbaceous hosts in a wetland community at two soil fertility levels. Plots in an oligohaline marsh were treated in a 2 x 2 factorial design with vine removal and fertilization over two growing seasons. There was no significant interaction between removal and fertilization treatments on any of the measured variables. Vine removal initially caused an increase in light penetration through the canopy, but by the end of the study, plots with vines removed had less light due to a 25% increase in biomass by the plants released from competition with vines. For plots with vines removed, species richness was higher during a brief period in the spring of the second year, but by the end of the study, richness in removal plots decreased relative to controls. Fertilization caused a 40% increase in biomass overall, although only two species, Sagittaria lancifolia L. and Polygonum punctatum Ell., showed dramatic increases. Despite fertilization causing a 40% decrease in light penetration to the ground, no change in species richness was observed. Overall, these results show that vine cover in this wetland suppresses non-vine species and reduces community biomass. Removal of vines increased biomass of non-vine dominants but resulted in only an ephemeral change in species richness. Fertilization did not increase the effects of vines on the non-vine community.

Oecologia↗

USGS1998

Species-environment relationships and vegetation patterns: Effects of spatial scale and tree life-stage

Do relationships between species and environmental gradients strengthen or weaken with tree life-stage (i.e., small seedlings, large seedlings, saplings, and mature trees)? Strengthened relationships may lead to distinct forest type boundaries, or weakening connections could lead to gradual ecotones and heterogeneous forest landscapes. We quantified the changes in forest dominance (basal area of tree species by life-stage) and environmental factors (elevation, slope, aspect, intercepted photosynthetically active radiation (PAR), summer soil moisture, and soil depth and texture) across 14 forest ecotones (n = 584, 10 m x 10 m plots) in Rocky Mountain National Park, Colorado, U.S.A. Local, ecotone-specific species-environment relationships, based on multiple regression techniques, generally strengthened from the small seedling stage (multiple R2 ranged from 0.00 to 0.26) to the tree stage (multiple R2 ranged from 0.20 to 0.61). At the landscape scale, combined canonical correspondence analysis (CCA) among species and for all tree life-stages suggested that the seedlings of most species became established in lower-elevation, drier sites than where mature trees of the same species dominated. However, conflicting evidence showed that species-environment relationships may weaken with tree life-stage. Seedlings were only found in a subset of plots (habitats) occupied by mature trees of the same species. At the landscape scale, CCA results showed that species-environment relationships weakened somewhat from the small seedling stage (86.4% of the variance explained by the first two axes) to the tree stage (76.6% of variance explained). The basal area of tree species co-occurring with Pinus contorta Doug. ex. Loud declined more gradually than P. contorta basal area declined across ecotones, resulting in less-distinct forest type boundaries. We conclude that broad, gradual ecotones and heterogeneous forest landscapes are created and maintained by: (1) sporadic establishment of seedlings in sub-optimal habitats; (2) survivorship of saplings and mature trees in a wider range of environmental conditions than seedlings presently endure; and (3) the longevity of trees and persistence of tree species in a broad range of soils, climates, and disturbance regimes.

Plant Ecology↗