SEARCH · USGS Science

Results for “Plants”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,639 records · Page 91Linked to original sources

USGS2001

Physiological variation among native and exotic winter annuals associated with microphytic soil crusts in the Mojave Desert

Microbiotic crusts are important components of many aridland soils. Research on crusts typically focuses on the increase in soil fertility due to N-fixing micro-organisms, the stabilization of soils against water and wind erosion and the impact of disturbance on N-cycling. The effect of microbiotic crusts on the associated plant community has received little attention. We quantified the influence of crusts on the production, species diversity, nutrient content and water relations of winter annual plant species associated with microbiotic soil crusts in the northeast Mojave Desert. Shoot biomass of winter annuals was 37% greater and plant density was 77% greater on crusts than were biomass and density on soils lacking crust cover (=bare soils). This greater production of annuals on crusts was likely due to enhanced soil conditions including an almost two-fold increase in soil organic matter and inorganic N compared to bare soils. Crusted soils also had 53% greater volumetric water content than bare soils during November and December, the time when winter annuals become established. As plant development progressed into spring, however, soil water availability decreased: More negative plant xylem water potentials were associated with greater plant biomass on crusted soils. Plants associated with microbiotic soil crusts had lower concentrations of N in shoots (mg N g −1 dry mass). However, total shoot N (mg N m −2 ) was the same in plants growing on the different soil types when biomass production peaked in April. Shoots had similar patterns in their concentration and content of P. Species diversity of annuals was not statistically different between the two soil types. Yet, while native annuals comprised the greatest proportion of shoot biomass on bare soils, exotic forbs and grasses produced more biomass on crusts. Total shoot nutrient content (biomass×concentration) of the two exotic annual species examined was dramatically greater on crusts than bare soils; only one native species had greater shoot content of N and P when growing on crusts than bare soils. Microbiotic crusts appear to increase site fertility in the northeast Mojave Desert, but nutrients and water distributed within a greater biomass of annual plants growing on microbiotic crusts likely resulted in lower concentrations of nutrients in plant tissue and lower xylem pressure potentials than plants growing on bare soils. Exotic annuals growing on crusts appear to respond to the higher N availability by growing faster, potentially outcompeting native annual species.

Plant and Soil↗

USGS2020

Resource segregation at fine spatial scales explains Karner blue butterfly (Lycaeides melissa samuelis) distribution

The resource concentration hypothesis predicts that herbivorous insect density scales positively with plant density because insects are better able to identify, and remain longer in, patches with denser plant resources. While some studies support this hypothesis, others do not. Different explanations have been proposed for this discrepancy, including variation in insect dispersal ability and diet breadth. We test the resource concentration hypothesis using the Karner blue butterfly ( Lycaeides melissa samuelis ), a specialist that relies on wild blue lupine ( Lupinus perennis ) as its sole host plant. We extended this hypothesis to test whether Karner blue density also scales positively with nectar plant resources. Our findings did not support the resource concentration hypothesis and demonstrate that the spatial segregation of nectar and host plant resources relative to each other can influence the location and abundance of Karner blues on the landscape. This is because the location of resources relative to each other influences the energy and time butterflies expend for flight activity, and thereby influences resource acquisition. During early summer when first brood Karner blues emerge, nectar and host plants were spatially segregated, and Karner blue density peaked at intermediate densities of nectar and host plants occurring at ratios approximately equal to 1:1. During late summer, we found no significant relationships between second brood Karner blues and nectar plants or host plants when there was no correlation between nectar and host plants. Conservation practitioners of specialist insects with low vagility can strategically manage the distribution of plant resources to minimize insect time and energy expenditure and promote resource acquisition for all of an insect’s life stages.

Journal of Insect Conservation↗

USGS1999

The effects of global climate change on seagrasses

The increasing rate of global climate change seen in this century, and predicted to accelerate into the next, will significantly impact the Earth's oceans. In this review, we examine previously published seagrass research through a lens of global climate change in order to consider the potential effects on the world's seagrasses. A primary effect of increased global temperature on seagrasses will be the alteration of growth rates and other physiological functions of the plants themselves. The distribution of seagrasses will shift as a result of increased temperature stress and changes in the patterns of sexual reproduction. Indirect temperature effects may include plant community changes as a result of increased eutrophication and changes in the frequency and intensity of extreme weather events. The direct effects of sea level rise on the coastal oceans will be to increase water depths, change tidal variation (both mean tide level and tidal prism), alter water movement, and increase seawater intrusion into estuaries and rivers. A major impact of all these changes on seagrasses and tidal freshwater plants will be a redistribution of existing habitats. The intrusion of ocean water into formerly fresh or brackish water areas will directly affect estuarine plant distribution by changing conditions at specific locations, causing some plants to relocate in order to stay within their tolerance zones and allowing others to expand their distribution inland. Distribution changes will result from the effects of salinity change on seed germination, propagule formation, photosynthesis, growth and biomass. Also, some plant communities may decline or be eliminated as a result of increased disease activity under more highly saline conditions. Increased water depth, which reduces the amount of light reaching existing seagrass beds, will directly reduce plant productivity where plants are light limited. Likewise, increases in water motion and tidal circulation will decrease the amount of light reaching the plants by increasing turbidity or by stimulating the growth of epiphytes. Increasing atmospheric carbon dioxide will directly elevate the amount of CO 2 in coastal waters. In areas where seagrasses are carbon limited, this may increase primary production, although whether this increase will be sustained with long-term CO 2 enrichment is uncertain. The impact of increases in CO 2 will vary with species and environmental circumstances, but will likely include species distribution by altering the competition between seagrass species as well as between seagrass and algal populations. The reaction of seagrasses to UV-B radiation may range from inhibition of photosynthetic activity, as seen for terrestrial plants and marine algae, to the increased metabolic cost of producing UV-B blocking compounds within plant tissue. The effects of UV-B radiation will likely be greatest in the tropics and in southern oceans. There is every reason to believe that, as with the predicted terrestrial effects of global climate change, impacts to seagrasses will be great. The changes that will occur in seagrass communities are difficult to predict; our assessment clearly points out the need for research directed toward the impact of global climate change on seagrasses.

Aquatic Botany↗

USGS1979

Population differentiation along a flood frequency gradient: Physiological adaptations to flooding in Nyssa sylvatica

Throughout the southeastern United States the hardwood Nyssa sylvatica (sensu lato) is distributed along a soil moisture gradient from upland sites, which are never flooded, to floodplains, which are periodically flooded and drained to permanently flooded swamps. Population differentiation with respect to flood tolerance and related physiological attributes was investigated using 1—year—old seedlings grown in a greenhouse from seed collected along this gradient. Upland plants were very intolerant of flooded soils. Their root systems deteriorated, root respiration rates dropped and, after a year under such conditions, survival was poor and those that did remain were greatly stunted and had accumulated large concentrations of many nutrient elements. In contrast swamp plants were quite tolerant of flooded soils. Upon flooding, parts of the orginal root system were lost but new roots were initiated which had an increased capacity for alcoholic fermentation. Many of these new roots were more succulent, larger in diameter, and less branched than drained roots. Such succulent roots however were only a temporary response to short—term flooding; plants flooded for a year did not have such roots, rather the root system superficially resembled drained roots. Concomitant with this return to drained—like roots was an increase in internal oxygen transport to the roots and a drop in alcoholic fermentation. Floodplain plants under drained conditions allocated less biomass to roots than to shoots and had high respiration rates, traits similar to upland plants. Under flooded conditions they initiated new roots with medium respiration rates, allocated less biomass to roots than to shoots, significantly increased oxygen transport to the roots and had high survival, traits similar to swamp plants. Thus, the floodplain population produced a distinctly flood—tolerant phenotype; but not nearly as tolerant of flooded conditions as the swamp phenotype. Floodplain plants differed from swamp plants in transporting less oxygen to the roots under drained conditions, initiating fewer succulent—type roots and not accelerating alcoholic fermentation upon flooding and after a year under flooded conditions having less total biomass, less oxygen transport to the roots and a greater accumulation of Fe and Mn in the roots. The floodplain plants apparently have been selected to be similar to upland plants under drained conditions and swamp plants under flooding and one consequence of this is that their tolerance of flooded conditions is intermediate. It is argued that one of the more important trade—offs in adapting to flooded conditions is that high internal oxygen transport carries with it a ‘cost’ in terms of excessive water loss under water stress conditions.

Ecological Monographs↗

USGS2010

Effects of simulated moose Alces alces browsing on the morphology of rowan Sorbus aucuparia

In much of northern Sweden moose Alces alces browse rowan Sorbus aucuparia heavily and commonly revisit previously browsed plants. Repeated browsing of rowan by moose has created some concern for its long-term survival in heavily browsed areas. We therefore measured how four years of simulated moose browsing at four population densities (0, 10, 30 and 50 moose/1,000 ha) changed plant height, crown width, available bite mass, the number of bites per plant and per plant forage biomass of rowan saplings. Increased biomass removal led to a significant decline in plant height (P < 0.001), but a significant increase in the number of bites per plant (P = 0.012). Increases in the number of bites per plant more than compensated for weak decreases in bite mass, leading to a weak increase in per plant forage biomass (P = 0.072). With the decline in plant height and increase in the number of stems per plant, a greater number of bites remain within the height reach of moose relative to unbrowsed controls. Moose therefore stand to benefit from revisiting previously browsed plants, which may result in feeding loops between moose and previously browsed rowan saplings. ?? 2010 Wildlife Biology, NKV.

Wildlife Biology↗

USGS2018

Potential impacts of projected climate change on vegetation-management strategies in Hawai‘i Volcanoes National Park

Climate change is expected to alter the seasonal and annual patterns of rainfall and temperature in the Hawaiian Islands. Land managers and other responsible agencies will need to know how plant-species habitats will change over the next century in order to manage these resources effectively. This issue is a major concern for resource managers at Hawai‘i Volcanoes National Park (HAVO), where currently managed Special Ecological Areas (SEAs) for important plant species and communities may no longer provide suitable habitats in the future as the climate changes. Expanding invasive-species distributions also may pose a threat to areas where native plants currently predominate. The objective of this project was to combine recent climate-modeling efforts for the state of Hawai‘i with existing models of plant-species distribution in order to forecast suitable habitat ranges under future climate conditions derived from the Coupled Model Intercomparison Project, phase 3 (CMIP3) global circulation model that was dynamically downscaled for the Hawaiian Islands by using the Hawai‘i Regional Climate Model (HRCM). The HRCM uses the A1B emission scenario (a median future climate projection) from the Special Report on Emissions Scenarios (SRES). On the basis of this model, maps showing projected plant-species ranges were generated for four years as snapshots in time (2000, 2040, 2070, 2090) and for three different trajectories of climate change (gradual, linear, rapid) between the present and future. We mapped probabilistic surfaces of suitable habitat for 39 plant species (both native and alien [nonnative]) identified as being of interest to HAVO resource managers. We displayed these surfaces in terms of change relative to present conditions, whether the range of a given plant species was expected to contract, expand, or remain the same in the future. Within HAVO, approximately two-thirds (18 of 29) of the modeled native plant species were projected to contract in range, whereas one-third (11 of 29) were projected to increase. Most of the HAVO SEAs were projected to lose most of the native plant species modeled. Within HAVO, all alien plant species except Lantana camara were projected to contract in range within the park; this trend was observed in most SEAs, including those at low, middle, and high elevations. Congruence was good in the “current” (2000) distribution of plant-species richness and SEA configurations; however, the congruence between species-richness hotspots and SEAs diminished by the projected “end-of-century” (2090) distribution. Over time, the projected species-richness hotspots increasingly occurred outside of the currently configured SEA boundaries.

Hawai'i↗

USGS1949

Ground-water supplies of the Ypsilanti area, Michigan

As of the date of this report (August 1945), the major water users in the Ypsilanti area are: (1) the city of Ypsilanti, (2) the Willow Run bomber plant, built by the Federal Government and operated by the Ford Motor Co., and (3) the war housing project of the Federal Public Housing Authority, designated in this report the Willow Run Townsite. The city, bomber plant, and townsite have required large quantities of water for domestic and industrial uses, and the necessary water supplies have been developed from wells. The Federal Works Agency had the responsibility of deciding whether the existing water facilities were adequate to meet the expected demands and determining the character of any additional public water-supply facilities that might be constructed with Federal assistance. In order to appraise the ground-water resources of the area the Federal Works Agency requested the Geological Survey to investigate the adequacy of the existing supplies and the availability of additional water. The present report is the result of the investigation, which was made in cooperation with the Michigan Geological Survey Division. The water supplies of the three major users are obtained from wells penetrating glacial and associated sands and gravels. Supplies for the city of Ypsilanti and the Willow Run bomber plant are obtained from wells in the valley of the Huron River; the supply for the Willow Run Townsite is obtained from wells penetrating glacial gravels underlying the upland northeast of the valley. The bedrock formations of the area either yield little water to wells or yield water that is too highly mineralized for most uses. The water supply for the bomber plant is obtained from three closely spaced, highly productive wells at the northern edge of the Huron River, a little more than 3 miles southeast of Ypsilanti. The water receives complete treatment in a modern treatment plant. River water also can be treated and has been used occasionally in the winter and spring. The average daily pumpage during periods of maximum production at the bomber plant has been 4.5 to 4.75 million gallons. On June 30, 1945, production of bombers was suspended, and the plant went on a. maintenance basis. The water supply of the bomber-plant well field is replenished by recharge from precipitation and from the Huron River. The evidence shows that recharge from the river is one of the principal sources of water and gives assurance both of the adequacy of the present supply and of the availability of additional water if needed. The safe yield of the three existing wells is estimated to be not less than 6 million gallons per day. The Ypsilanti public water supply is obtained from three tubular wells drilled in 1943, which replaced a number of suction-pumped tubular wells and one large dug well. All the wells penetrate sand and gravel in the bend of the Huron River in the southeastern part of Ypsilanti. The water is treated in a modern treatment plant completed in 1939. The average daily pumpage in million gallons was about 1.68 in 1942, 1.70 in 1943, and 1.66 in 1944. Considerable water was furnished to the Willow Run bomber plant from the Ypsilanti public-supply system during the period from August 1941 through March 1943. The available information indicates that the water pumped from the Ypsilanti well field is replenished by ground-water flow from adjacent stretches of the Huron Valley and from the upland areas outside the valley, from precipitation on the valley in the vicinity of the well field, and possibly from the Huron River. It is believed that sufficient water can be obtained from the well field to meet the expected demand for a considerable time. The safe yield of the present wells is estimated to be not less than 3 million gallons per day, and detailed pumping tests might show that still larger supplies could be safely developed. The water supply of the Willow Run Townsite is obtained from four wells in two well fields about 2 miles apart, one well in the northwest or Prospect and Geddes Road field, and three wells in the southeast or Wiard Road field. The pumpage was originally expected to be 2 to 3 million gallons per day, but it averaged only about 450,000 gallons per day from March 1943 through June 1945. The evidence afforded by logs of wells and by pumping tests indicates that the water-bearing gravels at the townsite are covered by relatively impermeable materials and thus that the rate of recharge is low. However, only relatively small declines in water level have occurred during more than 2 years' operation of the wells, indicating that recharge may occur nearby. The safe yield of the present wells is estimated to be 1.0 to 1.5 million gallons per day, and detailed pumping tests might show it to be somewhat greater. The water supply of the Willow Run Townsite has the smallest potential capacity of the three major ground-water supplies in the area; however, the demand has been relatively small, and no difficulty should arise unless this demand increases greatly. The investigation involved the drilling of 13 test wells to locate additional ground-water supplies, on the assumption that the wartime demand for water in the Ypsilanti area might increase beyond the capacity of the present sources. All 13 wells were drilled at sites selected by the Geological Survey. Two wells on the Willow Run Townsite were drilled by the Federal Public Housing Authority and 11 at other sites by the Federal Works Agency. Records of the wells are given in the report and discussed with respect to the availability of water at the different sites; similarly, the results of the controlled pumping tests made on four of the test wells drilled by the Federal Works Agency are analyzed and discussed with respect to the availability of additional water. The combined results of the test drilling and the pumping tests show that emergency supplies of several million gallons per day can be developed at the sites of the test wells. The best site shown by the test drilling is on the south bank of the Huron River opposite the bomber-plant well field, where a Well with a capacity of several thousand gallons per minute could be constructed if necessary. Three wells in the outwash-filled valley now occupied by Fleming Creek, on two of which pumping tests were made, show that emergency supplies ranging from a few hundred thousand to a million gallons per day could be developed at these test-well sites if necessary. Smaller Supplies ranging from a gallon or two per minute to perhaps 100,000 or 200,000 gallons per day could be developed at the sites of the remaining test Wells. Pumping tests made on the supply wells of the three major water users by the consulting-engineering firms who designed the systems are analyzed and discussed briefly by the authors. The report includes maps and graphs showing the surficial geology of the area, the location of wells, and fluctuations of water level in selected wells. Alsp included are tables giving data on water levels and pumpage, chemical analyses of representative ground waters, and records of wells.

Michigan↗

USGS1997

Early vegetational changes on a forested wetland constructed for mitigation

Changes in vegetation were studied on 15 acres of a 35 acre forested wetland created as a mitigation site in Anne Arundel County, Maryland during 1994-96. Meter-square sampling on four different hydrologic elevations determined that grasses initially dominated the area, but decreased from 59 percent in 1994 to 51 percent in 1995 and 30 percent in 1996. Herbaceous non-grass plants (forbs) increased from 19 percent to 56 percent in the three-year period. Area with no plant cover decreased from 21 percent in 1994 to 11 percent in 1995, and 10 percent in 1996. Woody plants comprised 2 percent of the cover in 1994, increased to 4 percent in 1995, and remained at 4 percent in 1996. The increase of woody plants was mainly from natural regeneration (pioneer) plants. Monitoring of the transplanted trees and shrubs indicated 35 percent mortality and little growth of surviving plants. The pioneer woody plant forming most of the cover was black willow (Salix nigra). Differences in the vegetation were observed among the four elevations, although no differences were observed for the major vegetation classes between plots that were planted and those that were not planted with woody plants. Dominant grass species was redtop (Agrostis stolonifera), which comprised 51 percent of the cover in 1994 and 42 percent cover in 1995 and 23 percent in 1996. Other species that were common were bush clover (Lespedeza cuneata), Japanese clover (Lespedeza striata) and flat pea (Lathyrus sylvestris). All four of these dominant species were part of the original seed mixtures that were seeded on the site. A total of 134 species of plants was recorded on the site indicating a fairly diverse community for a newly established habitat.

Wetland Journal↗

USGS2011

Ecosystem response to removal of exotic riparian shrubs and a transition to upland vegetation

Understanding plant community change over time is essential for managing important ecosystems such as riparian areas. This study analyzed historic vegetation using soil seed banks and the effects of riparian shrub removal treatments and channel incision on ecosystem and plant community dynamics in Canyon de Chelly National Monument, Arizona. We focused on how seeds, nutrients, and ground water influence the floristic composition of post-treatment vegetation and addressed three questions: (1) How does pre-treatment soil seed bank composition reflect post-treatment vegetation composition? (2) How does shrub removal affect post-treatment riparian vegetation composition, seed rain inputs, and ground water dynamics? and (3) Is available soil nitrogen increased near dead Russian olive plants following removal and does this influence post-treatment vegetation? We analyzed seed bank composition across the study area, analyzed differences in vegetation, ground water levels, and seed rain between control, cut-stump and whole-plant removal areas, and compared soil nitrogen and vegetation near removed Russian olive to areas lacking Russian olive. The soil seed bank contained more riparian plants, more native and fewer exotic plants than the extant vegetation. Both shrub removal methods decreased exotic plant cover, decreased tamarisk and Russian olive seed inputs, and increased native plant cover after 2 years. Neither method increased ground water levels. Soil near dead Russian olive trees indicated a short-term increase in soil nitrogen following plant removal but did not influence vegetation composition compared to areas without Russian olive. Following tamarisk and Russian olive removal, our study sites were colonized by upland plant species. Many western North American rivers have tamarisk and Russian olive on floodplains abandoned by channel incision, river regulation or both. Our results are widely applicable to sites where drying has occurred and vegetation establishment following shrub removal is likely to be by upland species.

Plant Ecology↗

USGS2017

Spatial variation in edaphic characteristics is a stronger control than nitrogen inputs in regulating soil microbial effects on a desert grass

Increased atmospheric nitrogen (N) deposition can have wide-ranging effects on plant community structure and ecosystem function, some of which may be indirectly mediated by soil microbial responses to an altered biogeochemical environment. In this study, soils from a field N fertilization experiment that spanned a soil texture gradient were used as inocula in the greenhouse to assess the indirect effects of soil microbial communities on growth of a desert grass. Plant performance and interaction with soil microbiota were evaluated via plant above- and belowground biomass, leaf N concentration, and root fungal colonization. Nitrogen fertilization in the field increased the benefits of soil microbial inoculation to plant leaf N concentration, but did not alter the effect of soil microbes on plant growth. Plant-microbe interaction outcomes differed most strongly among sites with different soil textures, where the soil microbial community from the sandiest site was most beneficial to host plant growth. The findings of this study suggest that in a desert grassland, increases in atmospheric N deposition may exert a more subtle influence on plant-microbe interactions by altering plant nutrient status, whereas edaphic factors can alter the whole-plant growth response to soil microbial associates.

Journal of Arid Environments↗

USGS2021

Assessing the uncertainties in climatic estimates based on vegetation assemblages: Examples from modern vegetation assemblages in the American Southwest

Assemblages of fossil plant remains have been widely used to reconstruct past climatic conditions, usually through the application of methods that involve either finding vegetation analogues on the modern landscape (and using the modern associated climatic values as the basis for an estimate) or using the modern climatic ranges of individual taxa in an assemblage to determine the range of a given climate variable that would allow these plant taxa to live together. Although these approaches are relatively straightforward, it is difficult to assess the uncertainties associated with each approach, particularly in regard to their application to plant macrofossil assemblages. To explore the uncertainty that may arise from inaccuracy and imprecision in climate reconstructions and from ecological considerations we used variants of both approaches to estimate climate from two data sets of modern vegetation assemblages from the southwestern United States: (1) 1752 gridded “virtual plant assemblages” based on plant range maps that provide uniform spatial coverage of the presence or absence of major woody plant taxa across the study area; and (2) 43 modern packrat ( Neotoma spp.) midden presence-absence assemblages that are similar to fossil midden assemblages. By comparing observed and estimated climate values, we evaluated the quality of the climate estimates, identified sources of uncertainty, and characterized the nature and magnitude of the effects of these uncertainties on the climate estimates. Uncertainties in estimating climate from vegetation assemblages arise because any given plant taxon (or assemblage) must have the resiliency to survive a range of climatic variability, and because of the strong intercorrelations among climatic variables in the modern climate data. Additional sources of uncertainty in climate estimates from plant assemblages include: (1) the modern climate and plant distribution data that are selected as the basis for estimation; (2) the particular quantitative approach that is used to estimate climate; (3) the sufficiency of the number of taxa in the analysis for providing an unbiased representation of the vegetation community as it existed for each time period in the analysis; and, (4) the location of the assemblage on the climatic and environmental gradients in the calibration data set for each climate variable under consideration. We conclude that vegetation assemblages can provide valid and reproducible estimates of climatic variables and that the primary trends and mapped patterns in the observed climate data can be reconstructed from such estimates. However, many factors may affect the quality of an estimate from a given plant assemblage, including aspects of data selection, data adequacy, methodologies, and the location of the assemblage site relative to gradients in the base climate data. It is particularly difficult to accurately estimate extreme values in the observed climate data, because estimated values from either end of an observed climate gradient necessarily “move toward the middle” of the gradient. In addition, the interval chosen to represent modern climate (here we used 1961 to 1990) may have a large impact on the size of the estimated difference between modern and past climate at a given site.

Arizona, California, Colorado, Nevada, New Mexico,↗

USGS2003

Effects of life-state on detectability in a demographic study of the terrestrial orchid Cleistes bifaria

1. Most plant demographic studies follow marked individuals in permanent plots. Plots tend to be small, so detectability is assumed to be one for every individual. However, detectability could be affected by factors such as plant traits, time, space, observer, previous detection, biotic interactions, and especially by life - state . 2. We used a double-observer survey and closed population capture-recapture modelling to estimate state -specific detectability of the orchid Cleistes bifaria in a long-term study plot of 41.2 m 2 . Based on AIC c model selection, detectability was different for each life - state and for tagged vs. previously untagged plants. There were no differences in detectability between the two observers. 3. Detectability estimates (SE) for one-leaf vegetative, two-leaf vegetative, and flowering/fruiting states correlated with mean size of these states and were 0.76 (0.05), 0.92 (0.06), and 1 (0.00), respectively, for previously tagged plants, and 0.84 (0.08), 0.75 (0.22), and 0 (0.00), respectively, for previously untagged plants. (We had insufficient data to obtain a satisfactory estimate of previously untagged flowering plants). 4. Our estimates are for a medium-sized plant in a small and intensively surveyed plot. It is possible that detectability is even lower for larger plots and smaller plants or smaller life -states (e.g. seedlings) and that detectabilities < I are widespread in plant demographic studies. 5. State -dependent detectabilities are especially worrying since they will lead to a size- or state -biased sample from the study plot. Failure to incorporate detectability into demographic estimation methods introduces a bias into most estimates of population parameters such as fecundity, recruitment, mortality, and transition rates between life -states. We illustrate this by a simple example using a matrix model, where a hypothetical population was stable but, due to imperfect detection, wrongly projected to be declining at a rate of 8% per year. 6. Almost all plant demographic studies are based on models for discrete states. State and size are important predictors both for demographic rates and detectability . We suggest that even in studies based on small plots, state - or size-specific detectability should be estimated at least at some point to avoid biased inference about the dynamics of the population sampled.

Journal of Ecology↗

USGS2008

Elevated CO 2 enhances biological contributions to elevation change in coastal wetlands by offsetting stressors associated with sea-level rise

1. Sea-level rise, one indirect consequence of increasing atmospheric CO 2 , poses a major challenge to long-term stability of coastal wetlands. An important question is whether direct effects of elevated CO 2 on the capacity of marsh plants to accrete organic material and to maintain surface elevations outweigh indirect negative effects of stressors associated with sea-level rise (salinity and flooding). 2. In this study, we used a mesocosm approach to examine potential direct and indirect effects of atmospheric CO 2 concentration, salinity and flooding on elevation change in a brackish marsh community dominated by a C 3 species, Schoenoplectus americanus, and a C 4 grass, Spartina patens. This experimental design permitted identification of mechanisms and their role in controlling elevation change, and the development of models that can be tested in the field. 3. To test hypotheses related to CO 2 and sea-level rise, we used conventional anova procedures in conjunction with structural equation modelling (SEM). SEM explained 78% of the variability in elevation change and showed the direct, positive effect of S. americanus production on elevation. The SEM indicated that C 3 plant response was influenced by interactive effects between CO 2 and salinity on plant growth, not a direct CO 2 fertilization effect. Elevated CO 2 ameliorated negative effects of salinity on S. americanus and enhanced biomass contribution to elevation. 4. The positive relationship between S. americanus production and elevation change can be explained by shoot-base expansion under elevated CO 2 conditions, which led to vertical soil displacement. While the response of this species may differ under other environmental conditions, shoot-base expansion and the general contribution of C 3 plant production to elevation change may be an important mechanism contributing to soil expansion and elevation gain in other coastal wetlands. 5. Synthesis. Our results revealed previously unrecognized interactions and mechanisms contributing to marsh elevation change, including amelioration of salt stress by elevated CO 2 and the importance of plant production and shoot-base expansion for elevation gain. Identification of biological processes contributing to elevation change is an important first step in developing comprehensive models that permit more accurate predictions of whether coastal marshes will persist with continued sea-level rise or become submerged. ?? 2008 The Authors.

Journal of Ecology↗

USGS2020

Getting to the root of restoration: Considering root traits for improved restoration outcomes under drought and competition

A foundational goal of trait‐based ecology, including trait‐based restoration, is to link specific traits to community assembly, biodiversity, and ecosystem function. Despite a growing awareness of the importance of belowground traits for ecological processes, a synthesis of how to root traits can inform restoration of terrestrial plant communities is lacking. We reviewed and summarized existing literature focused on root traits in relation to plant performance measures (i.e. survival, establishment, productivity) in the contexts of drought and competition (including invasion). Root traits related to belowground resource acquisition (e.g. high specific root length, deep roots) are frequently related to drought avoidance (i.e. a plant strategy based on optimizing water uptake to maintain function), whereas studies relating root traits to drought tolerance (i.e. a plant strategy that allows plants to withstand low hydration) remain limited. More studies have linked root traits to plant competitive effects (i.e. the influence of a plant has on neighbors) than to competitive responses (i.e. a plant's ability to resist the effects of neighbors). Because plants with acquisitive traits decrease resources to the detriment of neighbors, root traits associated with rapid resource acquisition (e.g. high specific root length) may be important for understanding competitive effects. Albeit more limited, research suggests root traits associated with resource conservation or stress tolerance (e.g. high root tissue density, high root diameter) may elucidate mechanisms related to competitive responses. Re‐vegetation outcomes may be improved by considering root traits, but only if clear links are made between traits and plant performance in varied contexts.

Restoration Ecology↗

USGS1965

Movements of hatchery-reared lake trout in Lake Superior

The history of stocking of lake trout (Salvelinus namaycush) in the Great Lakes is reviewed. The study of movements is based on capture of 24,275 fin-clipped lake trout taken in experimental gill nets and trawls and commercial gill nets. Yearling lake trout planted from shore dispersed to 15-fath (27-m) depths in 3A? hr. Most fish remained within 2 miles (3.2 km) of the planting site 2 months, but within 4 months some fish had moved as much as 17 miles (27 km). The highest abundance of planted lake trout was in areas 2-4 miles (3.2-6.4 km) from the planting site even 3 years after release. Distance moved and size of fish were not correlated. Dispersal of lake trout begins at planting and probably continues until the fish are mature. Most movement was eastward in southern Lake Superior and followed the counterclockwise surface currents. Movement is most rapid in areas of strong currents and slowest in areas of weak currents or eddies. Movement to areas west of the Keweenaw Peninsula was insignificant from plantings in Keweenaw Bay and nil from other plantings farther east. Lake trout planted in the eastern third of the lake dispersed more randomly than those planted farther west. Few fish moved farther offshore than the 50-fath (91-m) contour. Lake trout planted in Canadian waters made insignificant contributions to populations in US waters.

Journal of the Fisheries Research Board of Canada↗

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↗

USGS2000

Elk-effects vegetation monitoring program for Tomales Point Elk Range, Point Reyes National Seashore, California

The monitoring program for elk effects on Tomales Point vegetation is designed to provide information on how tule elk grazing affects plant communities and rare species. The basic objective of the program is to show whether the elk are driving the vegetation into an unacceptable state by their grazing. The expectation is that as elk numbers increase, grazing pressure will increase too, resulting in unacceptable levels of any or all of the following: low vegetation ground cover, poor nutritional quality for the elk, undesirable increases in weedy species, unacceptable loss of native plant biodiversity, population declines in rare plants, population declines in plants used for food and nectar by the endangered silverspot butterfly, and increased erosion. The monitoring program has 3 basic components designed to provide complementary information on different aspects of the elk-vegetation system. Long-term plant community monitoring along permanent transects will show how plant species composition and cover are changing since cattle removal in 1979, and it will show whether any of he undesirable traits listed above are developing in the vegetation. However, monitoring these transects alone will not tell us what the effects of continued grazing by elk are apart from changes the vegetation would be undergoing anyway. In order to tease apart the elk effects from change that is happening because of cattle removal, elk exclosures are needed. By sampling inside and outside exclosures, we will be able to see how elk are modifying the rates and directions of change in the vegetation that would be happening in their absence. In a sense, the exclosures serve as a “check” on elk effects. They will allow us to interpret how much of the change is due to elk and how much can be attributed to other processes such as natural succession or weather patterns. This information will allow us to analyze whether changing elk management will have a desirable effect on the vegetation. Finally, periodic mapping and counting of plants in rare plant populations will show whether plant population ranges are expanding and populations are stable or growing. If not, then management actions can be taken to improve habitat conditions for the plants. A general summary of the rationale and sample design for each of the 3 components of the elk-effects monitoring program follows. Field sampling for the entire program should require about 15 weeks for a 2 to 3- person team, and data processing, analysis, and report writing should require about 9 weeks. Time and labor estimates for this program are given in Table A-1. In addition to elk-effects monitoring, Point Reyes staff periodically monitor fire transects and residual dry matter plots on Tomales Point. They are not included as part of the elk-effects monitoring program and they are described elsewhere. Protocols for fire and residual dry matter sampling are not included in the time estimate for the elk- effects monitoring program.

Open-File Report↗

USGS2011

Quantifying viruses and bacteria in wastewater—Results, interpretation methods, and quality control

Membrane bioreactors (MBR), used for wastewater treatment in Ohio and elsewhere in the United States, have pore sizes small enough to theoretically reduce concentrations of protozoa and bacteria, but not viruses. Sampling for viruses in wastewater is seldom done and not required. Instead, the bacterial indicators Escherichia coli (E. coli) and fecal coliforms are the required microbial measures of effluents for wastewater-discharge permits. Information is needed on the effectiveness of MBRs in removing human enteric viruses from wastewaters, particularly as compared to conventional wastewater treatment before and after disinfection. A total of 73 regular and 28 quality-control (QC) samples were collected at three MBR and two conventional wastewater plants in Ohio during 23 regular and 3 QC sampling trips in 2008-10. Samples were collected at various stages in the treatment processes and analyzed for bacterial indicators E. coli, fecal coliforms, and enterococci by membrane filtration; somatic and F-specific coliphage by the single agar layer (SAL) method; adenovirus, enterovirus, norovirus GI and GII, rotavirus, and hepatitis A virus by molecular methods; and viruses by cell culture. While addressing the main objective of the study-comparing removal of viruses and bacterial indicators in MBR and conventional plants-it was realized that work was needed to identify data analysis and quantification methods for interpreting enteric virus and QC data. Therefore, methods for quantifying viruses, qualifying results, and applying QC data to interpretations are described in this report. During each regular sampling trip, samples were collected (1) before conventional or MBR treatment (post-preliminary), (2) after secondary or MBR treatment (post-secondary or post-MBR), (3) after tertiary treatment (one conventional plant only), and (4) after disinfection (post-disinfection). Glass-wool fiber filtration was used to concentrate enteric viruses from large volumes, and small volume grab samples were collected for direct-plating analyses for bacterial indicators and coliphage. After filtration, the viruses were eluted from the filter and further concentrated. The final concentrated sample volume (FCSV) was used for enteric virus analysis by use of two methods-cell culture and a molecular method, polymerase chain reaction (PCR). Quantitative PCR (qPCR) for DNA viruses and quantitative reverse-transcriptase PCR (qRT-PCR) for RNA viruses were used in this study. To support data interpretations, the assay limit of detection (ALOD) was set for each virus assay and used to determine sample reporting limits (SRLs). For qPCR and qRT-PCR the ALOD was an estimated value because it was not established according to established method detection limit procedures. The SRLs were different for each sample because effective sample volumes (the volume of the original sample that was actually used in each analysis) were different for each sample. Effective sample volumes were much less than the original sample volumes because of reductions from processing steps and (or) from when dilutions were made to minimize the effects from PCR-inhibiting substances. Codes were used to further qualify the virus data and indicate the level of uncertainty associated with each measurement. Quality-control samples were used to support data interpretations. Field and laboratory blanks for bacteria, coliphage, and enteric viruses were all below detection, indicating that it was unlikely that samples were contaminated from equipment or processing procedures. The absolute value log differences (AVLDs) between concurrent replicate pairs were calculated to identify the variability associated with each measurement. For bacterial indicators and coliphage, the AVLD results indicated that concentrations <10 colony-forming units or plaque-forming units per 100 mL can differ between replicates by as much as 1 log, whereas higher concentrations can differ by as much as 0.3 log. The AVLD results for viruses indicated that differences between replicates can be as great as 1.2 log genomic copies per liter, regardless of the concentration of virus. Relatively large differences in molecular results for viruses between replicate pairs were likely due to lack of precision for samples with small effective volumes. Concentrations of E. coli, fecal coliforms, enterococci, and somatic and F-specific coliphage in post-secondary and post-tertiary samples in conventional plants were higher than those in post-MBR samples. In post-MBR and post-secondary samples, concentrations of somatic coliphage were higher than F-specific coliphage. In post-disinfection samples from two MBR plants (the third MBR plant had operational issues) and the ultraviolet conventional plant, concentrations for all bacterial indicators and coliphage were near or below detection; from the chlorine conventional plant, concentrations in post-disinfection samples were in the single or double digits. All of the plants met the National Pollutant Discharge Elimination System required effluent limits established for fecal coliforms. Norovirus GII and hepatitis A virus were not detected in any samples, and rotavirus was detected in one sample but could not be quantified. Adenovirus was found in 100 percent, enterovirus in over one-half, and norovirus GI in about one-half of post-preliminary wastewater samples. Adenovirus and enterovirus were detected throughout the treatment processes, and norovirus GI was detected less often than the other two enteric viruses. Culturable viruses were detected in post-preliminary samples and in only two post-treatment samples from the plant with operational issues.

Scientific Investigations Report↗