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At least 721 records · Page 40Linked to original sources

USGS2021

Growth inhibition of the harmful alga Prymnesium parvum by plant-derived products and identification of ellipticine as highly potent allelochemical

Prymnesium parvum is a toxin-producing harmful alga that has caused ecological and economic damage worldwide. Effective methods to control blooms of this species in the field, however, are unavailable. This study examined five natural compounds present in the invasive plant Arundo donax and one synthetic derivative (5,6-dichlorogramine) for their effect on P. parvum growth. All compounds except one inhibited growth in the following order of potency: ellipticine > > 5,6-dichlorogramine > 1 H-indole = 2,4,6-trimethyl-benzonitrile > gramine. Ellipticine was by far the most potent inhibitor, with full algicidal activity at concentrations as low as 0.04 mg L −1 and 3- and 9-day IC 50 values of 0.012 and 0.007 mg L −1 , respectively. A reduction in chlorophyll content and swimming activity and an increase in length and volume (swelling) were documented in algal cells exposed to 0.01–0.02 mg ellipticine L −1 . These results show that ellipticine is among the most potent natural algicides identified to date. The sixth compound tested, oleamide, unexpectedly stimulated algal growth above control levels. Overall, these observations confirm the existence of highly potent anti- P. parvum allelochemicals in giant reed and demonstrate potential for using products derived from this plant in the development of natural, environmentally friendly methods to control harmful algal blooms.

Journal of Applied Phycology↗

USGS2007

Prescribed fire and cutting as tools for reducing woody plant succession in a created salt marsh

This paper reports on efforts to reduce woody successional growth by the native shrub Iva frutescens L. in a created salt marsh by using prescribed fire and cutting. Experimental treatments included a winter burn, cutting plants at ground level, and a combination burn-and-cut treatment, with replicate plots of each. Iva frutescens proved to be extremely hardy, with zero mortality following the cutting, burning, or combination treatment; similar levels of regrowth were observed for all treatments. Individual shrub response, however, was found to be related to initial plant size, ground water level and salinity, and two fire characteristics (total heating >60??C and total heat index >60??C). Fire severity, sediment nutrient concentrations, and other abiotic factors had no observable effects. ?? 2007 Springer Science+Business Media B.V.

Wetlands Ecology and Management↗

USGS2024

Spatial patterns as long transients in submersed-floating plant competition with biocontrol

A cellular automata model was developed and parameterized to test the effectiveness of application of biological control insects to water hyacinth ( Pontederia crassipes ), which is an invasive floating plant species in many parts of the world and outcompetes many submersed native aquatic species in southern Florida. In the model, P. crassipes was allowed to compete with Nuttall’s waterweed ( Elodea nuttallii ). In the absence of biocontrol acting on the P. crassipes , E. nuttallii excluded P. crassipes at low concentrations of the limiting nutrient (nitrogen), and the reverse occurred at high nutrient concentrations. At intermediate values, alternative stable states could occur; either P. crassipes alone or a mixture of the two species. When the biocontrol agent, the weevil Neochetina eichhorniae , was applied in the model, there was initially a rapid reduction of the P. crassipes , however, over time a regular striped pattern of moving spatially alternating stripes of P. crassipes and E. nuttallii emerged. -This pattern of moving stripes emerged and persisted over thousands of days but could quickly transform into an irregular pattern at some apparently random time, when either external stochasticity (added adult weevils) or only the weak internal stochasticity of weevil movements occurred. The cause of the end of the long transient can be traced to a single slightly irregular pixel within the striped pattern. Model parameters were varied to study effects of plant growth rate, nutrient concentration and nutrient diffusion rate on the dynamics of the system.

Theoretical Ecology↗

USGS2016

Effect of phytoremediation on concentrations of benzene, toluene, naphthalene, and dissolved oxygen in groundwater at a former manufactured gas plant site, Charleston, South Carolina, USA, 1998–2014

Concentrations of benzene, toluene, naphthalene, and dissolved oxygen in groundwater at a former manufactured gas plant site near Charleston, South Carolina, USA, have been monitored since the installation of a phytoremediation system of hybrid poplar trees in 1998. Between 2000 and 2014, the concentrations of benzene, toluene, and naphthalene (BT&N) in groundwater in the planted area have decreased. For example, in the monitoring well containing the highest concentrations of BT&N, benzene concentrations decreased from 10,200 µg/L to less than 4000 µg/L, toluene concentrations decreased from 2420 µg/L to less than 20 µg/L, and naphthalene concentrations decreased from 6840 µg/L to less than 3000 µg/L. Concentrations of BT&N in groundwater in all wells were observed to be lower during the summer months relative to the winter months of a particular year during the first few years after installing the phytoremediation system, most likely due to increased transpiration and contaminant uptake by the hybrid poplar trees during the warm summer months; this pathway of uptake by trees was confirmed by the detection of benzene, toluene, and naphthalene in trees during sampling events in 2002, and later in the study in 2012. These data suggest that the phytoremediation system affects the groundwater contaminants on a seasonal basis and, over multiple years, has resulted in a cumulative decrease in dissolved-phase contaminant concentrations in groundwater. The removal of dissolved organic contaminants from the aquifer has resulted in a lower demand on dissolved oxygen supplied by recharge and, as a result, the redox status of the groundwater has changed from anoxic to oxic conditions. This study provides much needed information for water managers and other scientists on the viability of the long-term effectiveness of phytoremediation in decreasing groundwater contaminants and increasing dissolved oxygen at sites contaminated by benzene, toluene, and naphthalene.

South Carolina↗

USGS2009

Conceptual hierarchical modeling to describe wetland plant community organization

Using multivariate analysis, we created a hierarchical modeling process that describes how differently-scaled environmental factors interact to affect wetland-scale plant community organization in a system of small, isolated wetlands on Mount Desert Island, Maine. We followed the procedure: 1) delineate wetland groups using cluster analysis, 2) identify differently scaled environmental gradients using non-metric multidimensional scaling, 3) order gradient hierarchical levels according to spatiotem-poral scale of fluctuation, and 4) assemble hierarchical model using group relationships with ordination axes and post-hoc tests of environmental differences. Using this process, we determined 1) large wetland size and poor surface water chemistry led to the development of shrub fen wetland vegetation, 2) Sphagnum and water chemistry differences affected fen vs. marsh / sedge meadows status within small wetlands, and 3) small-scale hydrologic differences explained transitions between forested vs. non-forested and marsh vs. sedge meadow vegetation. This hierarchical modeling process can help explain how upper level contextual processes constrain biotic community response to lower-level environmental changes. It creates models with more nuanced spatiotemporal complexity than classification and regression tree procedures. Using this process, wetland scientists will be able to generate more generalizable theories of plant community organization, and useful management models. ?? Society of Wetland Scientists 2009.

Wetlands↗

USGS2011

Carbon gas fluxes in re-established wetlands on organic soils differ relative to plant community and hydrology

We measured CO 2 and CH 4 fluxes for 6 years following permanent flooding of an agriculturally managed organic soil at two water depths (~25 and ~55 cm standing water) in the Sacramento–San Joaquin Delta, California, as part of research studying C dynamics in re-established wetlands. Flooding rapidly reduced gaseous C losses, and radiocarbon data showed that this, in part, was due to reduced oxidation of "old" C preserved in the organic soils. Both CO 2 and CH 4 emissions from the water surface increased during the first few growing seasons, concomitant with emergent marsh establishment, and thereafter appeared to stabilize according to plant communities. Areas of emergent marsh vegetation in the shallower wetland had greater net CO 2 influx (-485 mg Cm -1 h -1 ), and lower CH 4 emissions (11.5 mg Cm -2 h -1 ), than in the deeper wetland (-381 and 14.1 mg Cm -2 h -1 , respectively). Areas with submerged and floating vegetation in the deeper wetland had CH 4 emissions similar to emergent vegetation (11.9 and 12.6 mg Cm -2 h -1 , respectively), despite lower net CO 2 influx (-102 gC m -2 h -1 ). Measurements of plant moderated net CO 2 influx and CH 4 efflux indicated greatest potential reduction of greenhouse gases in the more shallowly flooded wetland.

California↗

USGS2013

Exotic plant colonization and occupancy within riparian areas of the Interior Columbia River and Upper Missouri River basins, USA

Exotic plant invasions into riparia often result in shifts in vegetative composition, altered stream function, and cascading effects to biota at multiple scales. Characterizing the distribution patterns of exotic plants is an important step in directing targeted research to identify mechanisms of invasion and potential management strategies. In this study, we employed occupancy models to examine the associations of landscape, climate, and disturbance attributes with the colonization and occupancy patterns for spotted knapweed ( Centaurea stoebe L.), Canada thistle ( Cirsium arvense L., Scop.), and cheatgrass ( Bromus tectorum L.) in the riparia of headwater streams ( n  = 1,091) in the Interior Columbia River and Upper Missouri River Basins. We found relatively low occupancy rates for cheatgrass (0.06, SE = 0.02) and spotted knapweed (0.04, SE = 0.01), but moderate occupancy of Canada thistle (0.28, SE = 0.05); colonization rates were low across all species (<0.01). We found the distributions of spotted knapweed, Canada thistle, and cheatgrass to exhibit significant associations with both ambient climate conditions and anthropogenic and natural disturbances. We attribute the low to moderate occupancy and colonization rates to the relatively remote locations of our sample sites within headwater streams and urge consideration of means to prevent further invasions.

Interior Columbia River and Upper Missouri River b↗

USGS2017

Plant and insect remains from the Wisconsinan interstadial/stadial transition at Wedron, north-central Illinois

Organic material exposed within a small swale fill in Pit 6 of the Wedron Silica Sand Co. near Wedron in LaSalle County, Illinois, includes well-preserved pollen, plant macrofossils, and insect remains. This material occurs in slackwater sediment in the lower part of the Peddicord Formation, which was deposited as existing valleys were dammed by fluvial aggradation during the initial late Wisconsinan advance of Laurentide ice into the Wedron area. Wood from the organic horizon has a radiocarbon age of 21,460 ?? 470 yr B.P. (ISGS-1486). The pollen spectrum is dominated by Picea, Pinus, and Cyperaceae. Plant macrofossils comprise a mix of boreal-forest taxa, including Picea, Larix laricina, and the moss Campylium stellatum; subarctic species including Betula glandulosa, Empetrum nigrum, and Selaginella selaginoides; along with the predominantly arctic Vaccinium uliginosum var. alpinum, Dryas integrifolia, and Rhododendron lapponicum. The insect fauna contains the western montane ground beetle Opisthius richardsoni; several arctic-subarctic ground beetles including Diacheila polita, Helophorus sibiricus, and Pterostichus (Cryobius) caribou; and a diverse assemblage of insects that today inhabit the boreal forest. We interpret the biotic record to record a phase in the transition from closed boreal forest to open tundra as climatic conditions deteriorated in advance of continental glaciation. ?? 1990.

Quaternary Research↗

USGS1975

Sandrewia, n. gen., a problematical plant from the Lower Permian of Texas and Kansas

Sandrewia , n. gen., monotypified by S. texana , n. sp., is a plant from Lower Permian beds of north-central Texas and east-central Kansas. It is characterized by stout axes with spirally disposed, laxly inserted, petiolate leaves; the laminae are broadly flabelliform with coarse, open venation. The leaves are reminiscent of the vojnovskyalean Nephropsis , of the Permian Petchora Basin, U.S.S.R., but biologic relationships are only speculative because of limited material. However, leaf characteristics render Sandrewia easily identifiable. Its presently limited stratigraphic range, along with floristic associations, indicates it may be a useful guide fossil and supports the author's beliefs regarding important times and places in Paleozoic plant evolution.

Kansas, Texas↗

USGS2013

Radiocarbon dating of plant macrofossils from tidal-marsh sediment

Tidal-marsh sediment is an archive of Holocene environmental changes, including movements of sea and land levels, and extreme events such as hurricanes, earthquakes, and tsunamis. Accurate and precise radiocarbon dating of environmental changes is necessary to estimate rates of change and the recurrence interval (frequency) of events. Plant macrofossils preserved in growth position (or deposited soon after death) in tidal-marsh sediment are ideal samples for dating such changes. In this chapter, we focus on the selection of plant macrofossils for radiocarbon dating and the application of ages from different types of macrofossils to varied research projects, and make recommendations for selection and preparation of tidal-marsh samples for dating.

Book chapter↗

USGS2022

Climate change and plant regeneration from seeds in Mediterranean regions of the Northern Hemisphere

Mediterranean regions are biodiversity hotspots whose landscapes are characterized by evergreen sclerophyllous vegetation, mild-wet winters, and hot-dry summers. In the Northern Hemisphere, they occur in the Mediterranean Basin and California regions. In these areas, whose habitats are heavily shaped by centuries of anthropic activities, the main effects of climate change include a decrease in precipitation and change in its regime, a pronounced warming, an increase in frequency of extreme temperature events, and altered and intensified fire regimes. Climate change poses a double challenge to the regeneration from seeds of Mediterranean plants. Warmer winters mainly affect the seed germination phase by limiting “typical” Mediterranean cold-cued germination in autumn/winter and reducing overwinter dormancy release for those species whose seeds germinate in spring. Harsher summers are detrimental for the establishment phase, compromising seedling survival. However, evidence of phenotypic plasticity in some Mediterranean plants suggests potential adaptation to a changing climate in the short- to medium-term for species of these regions.

Book chapter↗

USGS2010

Control of one invasive plant species allows exotic grasses to become dominant in northern Great Plains grasslands

Decline of leafy spurge (Euphorbia esula) in the northern Great Plains of the US is generally viewed as a success story for biological control, but quality of the vegetation that survived the infestation is key to recovery of ecosystem function. In addition, effects of other invasive species, notably cool-season exotic grasses, must be taken into account. Objectives of this study were (1) to evaluate direction and significance of changes in biomass of native and exotic grasses, forbs, and leafy spurge and in plant species composition following control of leafy spurge by flea beetles and (2) to evaluate the relative effects of leafy spurge and exotic grasses on biomass of native grasses, biomass of forbs, and richness of native species. We monitored species composition (1998-2003 and 2008) and biomass (2000, 2002, 2003 and 2008) of these groups on spurge-infested and noninfested permanent plots at three sites with unbroken prairie sod in North Dakota, USA. We found little evidence, in terms of species richness or biomass of native grasses or forbs, that leafy spurge was being replaced by desirable native species, although desirable as well as weedy and exotic species were characteristic of 2008 vegetation at all three sites. Structural equation models revealed that leafy spurge had temporally intermittent negative effects on forb biomass and species richness, but no effects on native grasses. In contrast, exotic grass had consistently strong, negative effects on native grass biomass, as well as stronger negative effects than leafy spurge on native species richness. Although substantial native plant diversity remains at these sites, exotic grasses pose an important threat to these crucial building blocks of native prairie ecosystems. ?? 2010.

Biological Conservation↗

USGS2010

Abundances and distribution of minerals and elements in high-alumina coal fly ash from the Jungar Power Plant, Inner Mongolia, China

The fly ash from the Jungar Power Plant, Inner Mongolia, China, is unique because it is highly enriched in alumina (Al 2 O 3 >50%). The fly ash mainly consists of amorphous glass and mullite and trace amounts of corundum, quartz, char, calcite, K-feldspar, clay minerals, and Fe-bearing minerals. The mullite content in fly ash is as high as 37.4% because of high boehmite and kaolinite contents in feed coal. Corundum is a characteristic mineral formed during the combustion of boehmite-rich coal.Samples from the economizer were sieved into six size fractions (<120, 120-160, 160-300, 300-360, 360-500, and >500 mesh) and separated into magnetic, mullite+corundum+quartz (MCQ) and glass phases for mineralogical and chemical analysis. The corundum content increases but amorphous glass decreases with decreasing particle size. Fractions of small particle sizes are relatively high in mullite, probably because mullite was formed from fine clay mineral particles under high-temperature combustion condition. Similarly, fine corundum crystals formed in the boiler from boehmite in feed coal. The magnetic phase consists of hematite, magnetite, magnesioferrite, and MgFeAlO 4 crystals. The MCQ phase is composed of 89% mullite, 6.1% corundum, 4.5% quartz, and 0.5% K-feldspar.Overall, the fly ash from the power plant is significantly enriched in Al 2 O 3 with an average of 51.9%, but poor in SiO 2 , Fe 2 O 3 , CaO, MgO, Na 2 O, P 2 O 5 , and As. Arsenic, TiO 2 , Th, Al 2 O 3 , Bi, La, Ga, Ni, and V are high in mullite, and the magnetic matter is enriched in Fe 2 O 3 , CaO, MnO, TiO 2 , Cs, Co, As, Cd, Ba, Ni, Sb, MgO, Zn, and V. The remaining elements are high in the glass fraction. The concentration of K 2 O, Na 2 O, P 2 O 5 , Nb, Cr, Ta, U, W, Rb, and Ni do not clearly vary with particle size, while SiO 2 and Hg decrease and the remaining elements clearly increase with decreasing particle size. ?? 2009 Elsevier B.V.

International Journal of Coal Geology↗

USGS2020

Wave-like patterns of plant phenology determine ungulate movement tactics

Animals exhibit a diversity of movement tactics [1]. Tracking resources that change across space and time is predicted to be a fundamental driver of animal movement [2]. For example, some migratory ungulates (i.e., hooved mammals) closely track the progression of highly nutritious plant green-up, a phenomenon called “green-wave surfing” [3-5]. Yet, general principles describing how the dynamic nature of resources determine movement tactics are lacking [6]. We tested emerging theory that predicts surfing and the existence of migratory behavior will be favored in environments where green-up is fleeting and moves sequentially across large landscapes (i.e., wave-like green-up) [7]. Landscapes exhibiting wave-like patterns of green-up facilitated surfing and explained the existence of migratory behavior across 61 populations of four ungulate species on two continents (n=1,696 individuals). At the species level, foraging benefits were equivalent between tactics, suggesting that each movement tactic is fine tuned to local patterns of plant phenology. For decades, ecologists have sought to understand how animals move to select habitat, commonly defining habitat as a set of static patches [8, 9]. Our findings indicate that animal movement tactics emerge as a function of the flux of resources across space and time, underscoring the need to redefine habitat to include its dynamic attributes. As global habitats continue to be modified by anthropogenic disturbance and climate change [10], our synthesis provides a generalizable framework to understand how animal movement will be influenced by altered patterns of resource phenology.

Alberta, British Columbia, Idaho, Wyoming↗

USGS2024

Avian communities respond to plant and landscape composition in actively revegetated floodplains of the Colorado River delta in Mexico

We examined the influence of local habitat factors such as plant community composition and species cover, and landscape habitat factors (e.g., land cover types) on the composition of the avian community in an arid-region large river delta (Colorado River). This 106 river km-long study area has experienced restoration through environmental water deliveries and active management of vegetation for ca. 10 years after decades of degradation. Variation partitioning and spatial models (Moran Eigenvector Maps) showed that plant communities and land cover combined explained 29.3% of the variability of 115 bird species, with a high overlap of 13.1% as vegetation and landscape factors were partially confounded and spatially correlated. Redundancy analyses showed that a higher cover of native riparian trees and shrubs and a larger amount of land covered by forests, typical characteristics of revegetated sites, favored bird species with affinity for riparian forests. Marshland and open water landscape features and high cover of macrophytes (which were common in the wettest river reach among the five included in the study), irrespective of active revegetation, were associated with a higher prevalence of wetland birds. Dominance by the non-native shrub Tamarix spp. and, especially, barren areas were detrimental to most bird species. The proportion of agricultural lands around the study sites was related to high abundance of generalists and some non-native species. Overall, our study showed that both local (vegetation) and landscape (land use) factors are important considerations for restoration of riparian bird communities.

Ecological Engineering↗

USGS2012

Plant toxins and trophic cascades alter fire regime and succession on a boral forest landscape

Two models were integrated in order to study the effect of plant toxicity and a trophic cascade on forest succession and fire patterns across a boreal landscape in central Alaska. One of the models, ALFRESCO, is a cellular automata model that stochastically simulates transitions from spruce dominated 1 km2 spatial cells to deciduous woody vegetation based on stochastic fires, and from deciduous woody vegetation to spruce based on age of the cell with some stochastic variation. The other model, the ‘toxin-dependent functional response’ model (TDFRM) simulates woody vegetation types with different levels of toxicity, an herbivore browser (moose) that can forage selectively on these types, and a carnivore (wolf) that preys on the herbivore. Here we replace the simple succession rules in each ALFRESCO cell by plant–herbivore–carnivore dynamics from TDFRM. The central hypothesis tested in the integrated model is that the herbivore, by feeding selectively on low-toxicity deciduous woody vegetation, speeds succession towards high-toxicity evergreens, like spruce. Wolves, by keeping moose populations down, can help slow the succession. Our results confirmed this hypothesis for the model calibrated to the Tanana floodplain of Alaska. We used the model to estimate the effects of different levels of wolf control. Simulations indicated that management reductions in wolf densities could reduce the mean time to transition from deciduous to spruce by more than 15 years, thereby increasing landscape flammability. The integrated model can be useful in estimating ecosystem impacts of wolf control and moose harvesting in central Alaska.

Alaska↗

USGS2010

Determination of antibiotics in sewage from hospitals, nursery and slaughter house, wastewater treatment plant and source water in Chongqing region of Three Gorge Reservoir in China

Sewage samples from 4 hospitals, 1 nursery, 1 slaughter house, 1 wastewater treatment plant and 5 source water samples of Chongqing region of Three Gorge Reservoir were analyzed for macrolide, lincosamide, trimethoprim, fluorouinolone, sulfonamide and tetracycline antibiotics by online solid-phase extraction and liquid chromatography-tandem mass spectrometry. Results showed that the concentration of ofloxacin (OFX) in hospital was the highest among all water environments ranged from 1.660 μg/L to 4.240 μg/L and norfloxacin (NOR, 0.136–1.620 μg/L), ciproflaxacin (CIP, ranged from 0.011 μg/L to 0.136 μg/L), trimethoprim (TMP, 0.061–0.174 μg/L) were commonly detected. Removal range of antibiotics in the wastewater treatment plant was 18–100% and the removal ratio of tylosin, oxytetracycline and tetracycline were 100%. Relatively higher removal efficiencies were observed for tylosin (TYL), oxytetracycline (OXY) and tetracycline (TET)(100%), while lower removal efficiencies were observed for Trimethoprim (TMP, 1%), Epi-iso-chlorotetracycline (EICIC, 18%) and Erythromycin-H 2 O (ERY-H 2 O, 24%). Antibiotics were removed more efficiently in primary treatment compared with those in secondary treatment.

Chongqing region, Three Gorge Reservoir↗

USGS2021

Freezing temperatures restrict woody plant recruitment and restoration efforts in abandoned montane pastures

Tropical montane forests are being lost at an alarming rate but harbor some of the globe’s most unique biodiversity. The Hawaiian archipelago is a prime example of the importance of high elevation forests to species conservation and persistence as they serve as the last refugia for Hawaiian birds. Yet these forests have been converted to invasive dominated pastures, and efforts to restore them have been met with limited success. Unsuccessful forest restoration may be due to freezing temperatures acting as a demographic bottleneck by killing seedlings recruiting into pastures. We determined freezing tolerances of eight common native woody plants at a high-elevation forest on Hawaiʻi Island and compared these freezing tolerances to two years of site-specific winter temperatures and 17 years of regional temperature records. Low temperature extremes were more severe and common in pastures than under nearby 30-year-old canopy trees. Freezing temperatures over two years were severe enough to damage leaf tissues of six of eight species tested. Those species that displayed the greatest freezing tolerance were also those found naturally recruiting into open pastures. Temperature trends over the past 17 years show monthly minimum temperatures are not increasing as predicted by climate change. Persistent severe freezing events may limit seedling recruitment in the pasture, slowing native woody plant expansion into these abandoned pastures. The species-level differences in freezing tolerance show that current management actions are using species that are at high risk to freezing damage outside of the forest canopy and that alternative species may warrant consideration.

Global Ecology and Conservation↗