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Results for “Plant Ecology and Diversity”

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At least 127 records · Page 7Linked to original sources
USGS1949

Research in coal paleobotany since 1943

The varied applications of paleobotany to coal resource studies, coal technology, and to fundamental physical and chemical research on coal are briefly indicated. The usual conception of paleobotany is not as broad as this, and many of the studies of fossil plants have been conducted without reference to the part the plant materials assume in composing coal. The interrelationship of paleobotany with the physical constitution and petrography of coal is an intimate one. which is too involved for treatment in the present paper. Chief emphasis is devoted to review of plant microfossil investigations during the past several years.The consistent abundance of plant microfossils in coal and its associated rocks is now generally recognized. One of the greatest difficulties in using this material for correlation and for extending our knowledge of the plant composition of coal has been in systematic (taxonomic) treatment of the materials. The reviews of recent literature are presented chiefly with reference to the diverse systematic approaches of various authors. The contrast between essentially nonbotanical or morphologic classification schemes, which are simpler to apply and which may serve adequately for local correlational studies, and those studies conceived on a more fundamental basis of plant taxonomy, for paleogeographic and ecologic interpretation of botanically related groups, is presented. Both viewpoints should be kept clearly in mind, since differing circumstances of study and differing objectives may suggest the advisability of using one rather than the other method of systematic treatment of these fossils. No other fossils are so conveniently available from the coal deposits of primary interest.

Economic Geology↗
USGS2013

Space can substitute for time in predicting climate-change effects on biodiversity

“Space-for-time” substitution is widely used in biodiversity modeling to infer past or future trajectories of ecological systems from contemporary spatial patterns. However, the foundational assumption—that drivers of spatial gradients of species composition also drive temporal changes in diversity—rarely is tested. Here, we empirically test the space-for-time assumption by constructing orthogonal datasets of compositional turnover of plant taxa and climatic dissimilarity through time and across space from Late Quaternary pollen records in eastern North America, then modeling climate-driven compositional turnover. Predictions relying on space-for-time substitution were ∼72% as accurate as “time-for-time” predictions. However, space-for-time substitution performed poorly during the Holocene when temporal variation in climate was small relative to spatial variation and required subsampling to match the extent of spatial and temporal climatic gradients. Despite this caution, our results generally support the judicious use of space-for-time substitution in modeling community responses to climate change.

Proceedings of the National Academy of Sciences↗
USGS2003

Differences in native soil ecology associated with invasion of the exotic annual chenopod, Halgeton glomeratus

Various biotic and abiotic components of soil ecology differed significantly across an area where Halogeton glomeratus is invading a native winterfat, [ Krascheninnikovia (= Ceratoides ) lanata ] community. Nutrient levels were significantly different among the native, ecotone, and exotic-derived soils. NO 3 , P, K, and Na all increased as the cover of halogeton increased. Only Ca was highest in the winterfat area. A principal components analysis, conducted separately for water-soluble and exchangeable cations, revealed clear separation between halogeton- and winterfat-derived soils. The diversity of soil bacteria was highest in the exotic, intermediate in the ecotone, and lowest in the native community. Although further studies are necessary, our results offer evidence that invasion by halogeton alters soil chemistry and soil ecology, possibly creating conditions that favor halogeton over native plants.

Biology and Fertility of Soils↗
USGS2019

Evaluating mechanisms of plant‐mediated effects on herbivore persistence and occupancy across an ecoregion

Contemporary climate change is rapidly creating one of the greatest challenges for management and conservation during the 21st century. Mountain ecosystems, which have a high degree of spatial heterogeneity and contain numerous habitat specialists, have been identified as particularly vulnerable. We used data from multiple years across sites spanning a >40 million ha ecoregion to test hypotheses regarding how community‐level characteristics of vegetation may affect a mammalian generalist herbivore, the American pika ( Ochotona princeps ). We examined patterns of pika persistence across sites in the hydrographic Great Basin, and occupancy within a subset of these sites. We used mixed‐effects logistic regression models to compare evidence in support of competing explanations for each pattern within an information–theoretic framework (using Akaike's information criterion). Models reflected four hypothesized classes of mechanisms related to nutritional ecology, ecosystem function, indirect indication of climatic effects, and (synergistic) combinations of these three classes. At the site level, models reflecting synergistic effects received the most support. At the within‐site level, support appeared to be split equally among hypotheses containing predictors related to either nutritional ecology or indirect climate effects. Well‐supported predictors included cover of invasive plant species, cover of more‐xeric plant species, species evenness, and proportion of graminoid species. Our results both (1) identify important aspects of vegetation communities that may influence herbivore distribution in mountainous areas across a large, diverse geographic region, and (2) contribute to an improved understanding of how mountain ecosystems may be affected by ongoing climate change, more broadly.

California, Idaho, Nevada, Oregon, Utah, Wyoming↗
USGS2018

Effects of feral horse herds on plant communities across a precipitation gradient

Feral horses are widespread in the western United States, with the majority of feral horse herds found in the Great Basin. There is a federal mandate to manage these herds in order to maintain “ecological balance”; however, understanding of the specific effects of feral horse grazing on rangeland plant communities in this region is incomplete. To address this research gap, we utilized long-term grazing exclosures and fenceline contrasts to evaluate the impacts of feral horses on several plant community variables (diversity, richness, dominance, and biomass) and species composition. Because the effects of grazing can vary with site precipitation and productivity, we selected 5 sites from 4 different rangeland types (Great Basin Desert, Colorado Plateau, Rocky Mountain grassland, and mixed grass prairie) that spanned a mean annual precipitation gradient of 229 to 413 mm. Our results did not reveal a significant effect of feral horse grazing on plant community composition, species richness, diversity, evenness, or dominance. In contrast, total aboveground herbaceous biomass and grass biomass were significantly reduced with feral horse grazing, but these effects did not vary with mean annual precipitation. Our results suggest that, at least at the sites we studied, feral horses have affected the plant community by reducing herbaceous biomass but have not caused plant community shifts. Additional multisite studies, preferably with standardized exclosures and larger sample sizes, would increase our understanding of feral horse grazing effects and inform management of feral horse herds in the western United States.

Colorado, Montana, Nevada, North Dakota, Utah↗
USGS2017

Short-term and long-term evapotranspiration rates at ecological restoration sites along a large river receiving rare flow events

Many large rivers around the world no longer flow to their deltas, due to ever greater water withdrawals and diversions for human needs. However, the importance of riparian ecosystems is drawing increasing recognition, leading to the allocation of environmental flows to restore river processes. Accurate estimates of riparian plant evapotranspiration (ET) are needed to understand how the riverine system responds to these rare events and achieve the goals of environmental flows. In 2014, historic environmental flows were released into the Lower Colorado River at Morelos Dam (Mexico); this once perennial but now dry reach is the final stretch to the mighty Colorado River Delta. One of the primary goals was to supply native vegetation restoration sites along the reach with water to help seedlings establish and boost groundwater levels to foster the planted saplings. Patterns in ET before, during, and after the flows are useful for evaluating whether this goal was met and understanding the role that ET plays in this now ephemeral river system. Here, diurnal fluctuations in groundwater levels and MODIS data were used to compare estimates of ET specifically at three native vegetation restoration sites during 2014 planned flow events, while MODIS data was used to evaluate long-term (2002 – 2016) ET responses to restoration efforts at these sites. Overall, ET was generally 0 - 10 mm d -1 across sites and although daily ET values from groundwater data were highly variable, weekly averaged estimates were highly correlated with MODIS-derived estimates at most sites. The influence of the 2014 flow events was not immediately apparent in the results, although the process of clearing vegetation and planting native vegetation at the restoration sites was clearly visible in the results.

Colorado River↗
USGS2009

Fungal endophytes: diversity and functional roles

All plants in natural ecosystems appear to be symbiotic with fungal endophytes. This highly diverse group of fungi can have profound impacts on plant communities through increasing fitness by conferring abiotic and biotic stress tolerance, increasing biomass and decreasing water consumption, or decreasing fitness by altering resource allocation. Despite more than 100 yr of research resulting in thousands of journal articles, the ecological significance of these fungi remains poorly characterized. Historically, two endophytic groups (clavicipitaceous (C) and nonclavicipitaceous (NC)) have been discriminated based on phylogeny and life history traits. Here, we show that NC-endophytes represent three distinct functional groups based on host colonization and transmission, in planta biodiversity and fitness benefits conferred to hosts. Using this framework, we contrast the life histories, interactions with hosts and potential roles in plant ecophysiology of C- and NC-endophytes, and highlight several key questions for future work in endophyte biology.

New Phytologist↗
USGS2020

Continuous water-quality and suspended-sediment transport monitoring in the San Francisco Bay, California, water years 2016–17

The U.S. Geological Survey (USGS) monitors water quality and suspended-sediment transport in the San Francisco Bay (Bay) as part of a multi-agency effort to address estuary management, water supply, and ecological concerns. The San Francisco Bay area is home to millions of people, and the Bay teems with plants and both resident and migratory wildlife, and fish. Freshwater mixes with salt water in the Bay and is subject to riverine influences (floods, droughts, managed reservoir releases, and freshwater diversions) and marine influences (tides, waves, and effects of salt water). To understand this environment, the USGS along with its cooperators (see “Acknowledgments”), has been monitoring the Bay’s waters continuously since 1988.

California↗
USGS2004

Population structure and inbreeding vary with successional stage in created Spartina alterniflora marshes

Recruitment patterns in clonal plant populations are predicted to vary with seed dispersal capability and disturbance regime, such that species with small, widely dispersed seeds will become increasingly dominated by vegetative recruitment on disturbed areas following early colonization. Subsequent mortality due to competitive or stochastic effects is then predicted to cause a gradual decline in both clonal diversity and the ability of surviving clones to avoid geitonogamous mating and possible inbreeding depression. We tested predictions of these hypotheses by comparing four adjacent populations of the salt marsh plant, Spartina alterniflora, ranging in age from 2 to ∼50 yr, by measuring fine‐scale genetic structure at the level of both ramets and genets, and the rate of inbreeding. For this purpose, we sampled maternal tissue and seeds from discrete patches in the field and then genotyped both maternal and seedling tissue (germinated in a growth chamber) using standard molecular protocols. As predicted, we observed an increase in clonal diversity (measured as the complement of the Simpson Index corrected for finite sample sizes, 1 − D ) up to a maximum of 0.71 within 3‐m 2 patches at 16 yr, declining to 0.55 by ∼50 yr. Local recruitment of seedlings was evident as genetic structure occurring at the level of patches, as measured by the fixation index, θ, which was inversely correlated with diversity ( R 2 > 0.90 at all patch scales). Outcrossing rates were positively associated with clonal diversity, with the highest level (89%) at an intermediate level of 1 − D. The greatest selfing (32%) occurred in young (2‐yr‐old) patches with low diversity. Biparental inbreeding was minimal in all populations, never exceeding 1%. Inbreeding depression was inferred to be severe, as evidenced by near‐zero adult inbreeding coefficients. These results suggest a possible fitness trade‐off between clonal growth and the opportunity for outcrossing. We recommend that restoration plantings of clonal species with limited sexual recruitment capabilities should be designed to ensure adequate clonal diversity for the avoidance of inbreeding and the ability to adapt to subsequent environmental disturbances.

Louisiana↗
USGS2018

Continuous water-quality and suspended-sediment transport monitoring in the San Francisco Bay, California, water years 2014–15

The U.S. Geological Survey (USGS) monitors water quality and suspended-sediment transport in the San Francisco Bay (bay) as part of a multi-agency effort to address management, water supply, and ecological concerns. The San Francisco Bay area is home to millions of people, and the bay teems both with resident and with migratory wildlife, plants, and fish. Freshwater mixes with salt water in the bay, which is subject both to riverine influences (floods, droughts, managed reservoir releases and freshwater diversions) and to marine influences (tides, waves, effects of salt water). To understand this environment, the USGS, along with its partners (see “Acknowledgements”), has been monitoring the bay’s waters continuously since 1988. Several water-quality variables are of particular importance to State and Federal resource managers and are monitored at key locations throughout the bay (fig. 1). Salinity, which indicates the relative mixing of fresh and ocean waters in the bay, is derived from specific conductance measurements. Water temperature, along with salinity, affects the density of water, which controls gravity-driven circulation patterns and stratification in the water column. Turbidity, a measure of light scattered from suspended particles in the water, is used to estimate suspended-sediment concentration (SSC). Suspended sediment affects the bay in multiple ways: attenuation of sunlight in the water column, affecting phytoplankton growth; deposition on tidal marsh and intertidal mudflats, which can help sustain these habitats as sea level rises; deposition in ports and shipping channels, which can necessitate dredging; and often, adsorption of contaminants, affecting their distribution and concentrations in the environment. Dissolved oxygen concentration, essential to a healthy ecosystem and a fundamental indicator of water quality, is affected by water temperature, salinity, ecosystem metabolism, tidal currents, and wind. Tidal currents in the bay reverse four times a day, and wind direction and intensity typically vary on a daily cycle. Consequently, salinity, water temperature, SSC, and dissolved-oxygen concentration vary spatially and temporally throughout the bay. Therefore, continuous measurements are needed to observe these changes. The purpose of this fact sheet is to provide information about these variables, as well as internet links to access these continuous water-quality data collected by the USGS.

California↗
USGS2024

Human activity drives establishment, but not invasion, of non-native plants on islands

Island ecosystems are particularly susceptible to the impacts of invasive species. Many rare and endangered species that are endemic to islands are negatively affected by invasions. Past studies have shown that the establishment of non-native species on islands is related to native plant richness, habitat heterogeneity, island age, human activity, and climate. However, it is unclear whether the factors promoting establishment (i.e. the formation of self-sustaining populations) also promote subsequent invasion (i.e. spread and negative impacts). Using data from 4308 non-native plant species across 46 islands and archipelagos globally, we examined which biogeographic characteristics influence established and invasive plant richness using generalized linear models nested within piecewise structural equation models. Our results indicate that anthropogenic land use (i.e. human modification) is strongly associated with establishment but not invasion, that climate (maximum monthly temperature) is strongly associated with invasion but not establishment, and that habitat heterogeneity (represented by maximum elevation and island area) is strongly associated with both establishment and invasion. Island isolation explains native plant richness well, but is not associated with established and invasive plant richness, likely due to anthropogenic introductions. We conclude that anthropogenic land use on islands is likely to be a proxy for the number of introductions (i.e. propagule pressure), which is more important for establishment than invasion. Conversely, islands with more diverse habitats and favorable (warm) climate conditions are likely to contain more available niche space (i.e. ‘vacant niches’) which create opportunities for both establishment and invasion. By evaluating multiple stages of the invasion process, we differentiate between the biogeographic characteristics that influence plant establishment (which does not necessarily lead to ecological impacts) versus those that influence subsequent plant invasion (which does lead to negative impacts).

Ecography↗
USGS2020

Divergent biotic and abiotic filtering of root endosphere and rhizosphere soil fungal communities along ecological gradients

Plant roots assemble two distinct microbial compartments: the rhizosphere (microbes in soil surrounding roots) and the endosphere (microbes within roots). Our knowledge of fungal community assembly in these compartments is limited, especially in wetlands. We tested the hypothesis that biotic factors would have direct effects on rhizosphere and endosphere assembly, while abiotic factors would have direct and indirect effects. Using a field study, we examined the influences of salinity, water level and biotic factors on baldcypress (Taxodium distichum) fungal communities. We found that endosphere fungi were correlated with host density and canopy cover as opposed to rhizosphere, suggesting that hosts can impose selective filters on fungi colonizing into their roots. Meanwhile, local abiotic conditions strongly influenced both rhizosphere and endosphere diversity in opposite patterns: e.g. highest endosphere diversity (hump-shaped) while lowest rhizosphere diversity (U-shaped) at intermediate salinity levels. These results indicate that the assembly and structure for the root endosphere and rhizosphere within a host can be shaped by different processes. Our results also highlight the importance of assessing how environmental changes affect plant and plant-associated fungal communities in wetland ecosystems where saltwater intrusion and sea level rise are major threats to both plant and fungal communities.

FEMS Microbiology Ecology↗
USGS2005

Fine-scale spatial variation in plant species richness and its relationship to environmental conditions in coastal marshlands

Previous studies have shown that variations in environmental conditions play a major role in explaining variations in plant species richness at community and landscape scales. In this study, we considered the degree to which fine-scale spatial variations in richness could be related to fine-scale variations in abiotic and biotic factors. To examine spatial variation in richness, grids of 1 m 2 plots were laid out at five sites within a coastal riverine wetland landscape. At each site, a 5 × 7 array of plots was established adjacent to the river’s edge with plots one meter apart. In addition to the estimation of species richness, environmental measurements included sediment salinity, plot microelevation, percent of plot recently disturbed, and estimated community biomass. Our analysis strategy was to combine the use of structural equation modeling (path modeling) with an assessment of spatial association. Mantel’s tests revealed significant spatial autocorrelation in species richness at four of the five sites sampled, indicating that richness in a plot correlated with the richness of nearby plots. We subsequently considered the degree to which spatial autocorrelations in richness could be explained by spatial autocorrelations in environmental conditions. Once data were corrected for environmental correlations, spatial autocorrelation in residual species richness could not be detected at any site. Based on these results, we conclude that in this coastal wetland, there appears to be a fine-scale mapping of diversity to microgradients in environmental conditions.

Louisiana↗
USGS2013

Relationships between the health of Alaska Native communities and our environment -- phase 1, exploring and communicating

Alaska Natives depend on local natural resources for nutritional and, for many, spiritual health. As a result, public health in Alaska is strongly influenced by the relationship between people and their surrounding physical, chemical, and biological environments. Alaska is vast with diverse wildlife and plant communities that are valued as subsistence foods (fig. 1). These resources are supported by equally diverse ecosystems and their underpinning landforms and geologies. The U.S. Geological Survey (USGS) is attempting to integrate physical, chemical, and biological information to better describe current (2013) environments and project scenarios for the future. Integrating ecological data into the public health dialogue is challenging for the more than 280 rural communities of Alaska. This fact sheet reviews a recent USGS effort, the Geographic Information System (GIS) Native Health Project, to better incorporate scientific information into such dialogue.

Alaska↗
USGS2019

Field-level characteristics influence wild bee functional guilds on public lands managed for conservation

Throughout the Midwestern US, many public lands set aside for conservation engage in management activities (e.g., agriculture) that may act as stressors on wild bee populations. Several studies have investigated how wild bees respond to large-scale agriculture production; however, there has been limited assessment of how wild bees may be impacted by agricultural activity on public lands or how local variables may influence bee communities in these same areas. In this study, we assessed the abundance and richness of wild bee floral and nesting guilds at 30 agricultural field margins located on five Conservation Areas in Missouri. Generally, regardless of guild, bee abundance and richness was greater in field margins with more floral diversity and taller vegetation. Bee guilds responded negatively to agricultural production in Conservation Areas with fewer soil- and cavity-nesting bees collected in margins adjacent to annually cropped fields. Although fewer diet specialists were collected, specialist bee abundance and richness was greater in margins near fields that were uncropped (i.e., vegetated, but not row-cropped) during the previous year. Overall, the percentage of trees and shrubs within 800 m of study fields (i.e., “woodland”) was negatively associated with abundance and richness of bees, but specifically, reduced richness of soil-nesters and diet specialists. Our findings indicate agricultural management activities on public lands may lead to decreased abundance and richness of wild bee guilds. If public lands are to be managed for species diversity, including wild bees, maintaining diverse plant communities with taller vegetation (>100 cm) near cultivated fields and/or modifying agricultural production practices on public lands may greatly improve the conservation of local bee communities.

Global Ecology and Conservation↗
USGS2003

Quantitative characterization of the regressive ecological succession by fractal analysis of plant spatial patterns

We studied the effect of grazing on the degree of regression of successional vegetation dynamic in a semi-arid Mediterranean matorral. We quantified the spatial distribution patterns of the vegetation by fractal analyses, using the fractal information dimension and spatial autocorrelation measured by detrended fluctuation analyses (DFA). It is the first time that fractal analysis of plant spatial patterns has been used to characterize the regressive ecological succession. Plant spatial patterns were compared over a long-term grazing gradient (low, medium and heavy grazing pressure) and on ungrazed sites for two different plant communities: A middle dense matorral of Chamaerops and Periploca at Sabinar-Romeral and a middle dense matorral of Chamaerops, Rhamnus and Ulex at Requena-Montano. The two communities differed also in the microclimatic characteristics (sea oriented at the Sabinar-Romeral site and inland oriented at the Requena-Montano site). The information fractal dimension increased as we moved from a middle dense matorral to discontinuous and scattered matorral and, finally to the late regressive succession, at Stipa steppe stage. At this stage a drastic change in the fractal dimension revealed a change in the vegetation structure, accurately indicating end successional vegetation stages. Long-term correlation analysis (DFA) revealed that an increase in grazing pressure leads to unpredictability (randomness) in species distributions, a reduction in diversity, and an increase in cover of the regressive successional species, e.g. Stipa tenacissima L. These comparisons provide a quantitative characterization of the successional dynamic of plant spatial patterns in response to grazing perturbation gradient. ?? 2002 Elsevier Science B.V. All rights reserved.

Cabo de Gata Natural Park↗
USGS2020

Predicting bird guilds using vegetation composition and structure on a wild and scenic river in Arizona

Riparian areas are among the most ecologically diverse terrestrial ecosystems but make up <2% of landscape area in southwestern USA. Many species of resident and neotropical migratory birds utilize riparian habitats for breeding, foraging, and nesting. We quantified vegetation composition and structure to predict bird guilds on Wild and Scenic portions of the Verde River, Arizona. We grouped plant species into guilds based on similar functional traits to describe composition. We surveyed birds during the breeding and migrating season to determine abundance and categorized species into guilds using preferences of breeding habitat, foraging substrate, and nest placement. Riparian obligate and facultative breeding guilds were most common. Both vegetation composition and structure were useful predictors of birds. Vegetation structure was most complex in gallery riparian forest. Abundance of riparian-obligate birds in the breeding guild were positively associated with vegetation structure of dense, multi-canopy canopy and tall trees. Abundance of most bird guilds were positively associated with composition of tall trees ( Populus fremontii , Salix gooddingii ) and drought tolerant shrubs ( Prosopis velutina, Celtis reticulata ). Our findings show complex riparian habitat important to wildlife is created by both composition and structure of near-stream vegetation that is tied to hydrology and sensitive to flow change.

Arizona↗
USGS2020

Ecological interfaces between land and flowing water: Themes and trends in riparian research and management

This paper provides an overview of past, present and future themes for research and management of riparian zones, often relating to papers within this Wetlands Special Feature. Riparian research expanded in the United States around 1980 with themes that recognized (1) damage from excessive livestock, or (2) damage from river damming and diversion, and (3) the beneficial capacity of riparian buffers to intercept and assimilate nutrients and other water contaminants. Research expanded globally in the 1990s, with themes including (4) plant life history requirements and (5) reliance on fluvial geomorphic dynamics that enable riparian rejuvenation. Resource managers recognized that riparian areas provide (6) rich wildlife habitats (7) along with valued ecosystem services, (8) which encouraged conservation and restoration initiatives, (9) including environmental flow regimes. Floodplains are (10) vulnerable to invasive plants and management has included biocontrol such as for Tamarix in the American Southwest. Into the twenty-first century, (11) climate change is advancing, and riparian ecosystems may be especially impacted due to the compound challenges from increasing water demand and declining summer flows. As an emerging opportunity, (12) while reservoirs submerge floodplain vegetation, reservoir deltas may support compensatory riparian wetlands. (13) Studies increasingly utilize remote sensing tools including satellite imagery, LiDAR and unmanned aircraft systems, and (14) the coordination of large data sets invites digital ecology, including artificial intelligence and machine learning. Since riparian zones are centres for human activities, (15) there are opportunities for citizen science, social media and internet applications, which will increasingly democratize riparian research and management.

Wetlands↗