bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Isolated Trees in Facilitating Tree Seedling Recruitment at a Degraded Sub‐Tropical Rainforest Site
Authors: Toh Ing , Gillespie Melina , Lamb David 
Published: March 2003

AbstractSuccessional development at abandoned farmlands in southern Queensland, formerly occupied by sub‐tropical rain forest is centred around scattered, isolated trees. Soil seed banks contain few woody plants and most tree species appear to be recruited from seed dispersed into the site by birds or bats. Scattered, low‐growing trees <3 m in height act as the initial focus for the activities of seed‐dispersing birds, but this process is accelerated by the development of taller trees> 6 m in height that act as bird perches. The identity of these trees and whether or not they offer a fruit reward appears to matter less than their structure and suitability as a bird perch. The process of seedling recruitment may be accelerated when two or more trees form a cluster. The proportion of seedlings that survive and grow beyond 150 cm in height appears to be very small. Most of those that do can be classed as secondary rather than primary forest species, even though many primary forest species initially colonize the site. These observations were used to develop guidelines to accelerate the recovery of rainforest at degraded sites. The guidelines promote the early establishment of species that are usually poorly dispersed (e.g., large‐fruited species), planted in scattered clumps. The guidelines should be suitable for situations where relatively large areas are in need of rehabilitation.
Reducing Competitive Suppression of a Rare Annual Forb by Restoring Native California Perennial Grasslands
Authors: Carlsen Tina M. , Menke John W. , Pavlik Bruce M. 
Published: March 2003

AbstractPopulations of the rare annual forb Amsinckia grandiflora may be declining because of competitive suppression by exotic annual grasses, and may perform better in a matrix of native perennial bunchgrasses. We conducted a field competition experiment in which Amsinckia seedlings were transplanted into forty 0.64‐m2 experimental plots of exotic annual grassland or restored perennial grassland. The perennial grassland plots were restored using mature 3 cm‐diameter plants of the native perennial bunchgrass Poa secunda planted in three densities. The exotic annual grassland plots were established in four densities through manual removal of existing plants. Both grass types reduced soil water potential with increasing biomass, but this reduction was not significantly different between grass types. Both grass types significantly reduced the production of Amsinckia inflorescences. At low and intermediate densities (dry biomass per unit area of 20–80 g/m2), the exotic annual grasses reduced Amsinckia inflorescence number to a greater extent than did Poa, although at high densities (>90 g/m2) both grass types reduced the number of Amsinckia inflorescences to the same extent. The response of Amsinckia inflorescence number to Poa biomass was linear, whereas the same response to the annual grass biomass is logarithmic, and appeared to be related to graminoid cover. This may be because of the different growth forms exhibited by the two grass types. Results of this research suggest that restored native perennial grasslands at intermediate densities have a high habitat value for the potential establishment of the native annual A. grandiflora.
Deer Herbivory as an Ecological Constraint to Restoration of Degraded Riparian Corridors
Authors: Opperman Jeff J. , Merenlender Adina M. 
Published: March 2003

AbstractUngulate herbivory can impact riparian vegetation in several ways, such as by reducing vigor or reproductive output of mature plants, and through increased mortality of seedlings and saplings. Much work has focused on the effects of livestock grazing within riparian corridors, while few studies have addressed the influence of native ungulate herbivory on riparian vegetation. This study investigated the effect of deer herbivory on riparian regeneration along three streams with degraded riparian corridors in Mendocino County, California. We utilized existing stream restoration efforts by private landowners and natural resource agencies to compare six deer exclosures with six upstream control plots. Livestock were excluded from both exclosure and control plots. Three of the deer exclosures had been in place for 15 years, one for 6 years, and two for 4 years. The abundance and size distribution of woody riparian plant species such as Salix exigua, S. laevigata, S. lasiolepis, Alnus rhombifolia, and Fraxinus latifolia were quantified for each exclosure and control plot. The mean density of saplings in deer exclosures was 0.49 ± 0.15/m2, while the mean density of saplings in control plots was 0.05 ± 0.02/m2. Within exclosures, 35% of saplings were less than 1 m and 65% were greater than 1 m; within control plots, 97% of saplings were less than 1 m in height. The fact that little regeneration had occurred in control plots suggests that deer herbivory can substantially reduce the rate of recovery of woody riparian species within degraded riparian corridors. Exclusionary fencing has demonstrated promising results for riparian restoration in a region with intense deer herbivory.
Restoration of a Cirsio‐Molinietum Fen Meadow on an Agriculturally Improved Pasture
Authors: Tallowin J. R. B. , Smith R. E. N. 
Published: March 2003

AbstractThe objective of this study was to identify soil nutrient availability conditions that would allow the establishment of key species of the Molinia caerulea‐Cirsium dissectum fen meadow. The restoration site was a species‐poor agriculturally improved pasture that had received no inorganic fertilizer for greater than 13 years. Treatments designed to reduce site fertility included: cutting and removal of herbage, cultivation, fallowing and topsoil removal. Straw and/or lignitic‐clay were incorporated as soil amendment treatments. Cirsio‐Molinietum species were either sown or planted as seedlings on treated plots. Neither soil nitrogen nor potassium availability, per se, appeared to limit the establishment of Cirsio‐Molinietum species, whereas enhanced phosphorus availability did. Removal of the top 15–20 cm of soil reduced the total soil phosphorus amount by about 85 percent and depleted plant P availability. Nutrient‐poor and relatively calcium‐enriched soil exposed by topsoil removal allowed the development of a community with affinities to the Cirsio‐Molinietum typical fen meadow. Redundancy analysis indicated the existence of marked vegetational gradients within the topsoil removal treatments that were influenced by the straw and the lignitic‐clay amendments. The way in which these two amendments influenced edaphic conditions were unclear. Where the topsoil was not removed the vegetation became dominated by a few competitive species and although many of the planted Cirsio‐Molinietum species were still present after four years, they were found only in trace amounts. Removal of most of the soil organic matter was a practical success in that it created suitable edaphic conditions for all the planted Cirsio‐Molinietum species to remain well established.
Soil Seed Bank as an Input of Seed Source in Revegetation of Lead / Zinc Mine Tailings
Authors: Zhang Z. Q. , Shu W. S. , Lan C. Y. , Wong M. H. 
Published: March 2003

AbstractThe goal of the present study was to assess a soil seed bank as an input seed source for revegetating lead/zinc (Pb/Zn) mine tailings. The seed bank source was abandoned farmland, whose top 10‐cm layer of topsoil contained 6,850 ± 377 seeds/m2 from 41 species. The seeds in the soil were principally distributed in the upper 0–2 cm, which held 75.8% of total seeds and 92.7% of species composition. The top 2‐cm layer of topsoil may be sufficient to serve the purpose of providing a seed source for revegetation on derelict lands, including mined lands. Four different thicknesses of topsoil (1, 2, 4, and 8 cm, redistributed from the total 0–10‐cm layer from the farmland) were field‐tested on the Pb/Zn mine tailings. There was no significant difference in seedling density among the 4 thickness treatments. Many seeds in the treatments with more than 1‐cm of topsoil were unable to emerge from the deeper layer. Seedlings in plots with topsoil of 1‐, 2‐ and 4‐cm failed to establish within 1 year due to the extremely high acidity (pH 2.39 to 2.76). A shallow layer of topsoil cannot neutralize the sulfuric acid generated from oxidation of pyrites in the tailings. For establishment of seedlings on metalliferous lands, an insulating layer such as subsoil, building rubble, or domestic refuse is necessary before covering with valuable topsoil. The woody legume Leucaena leucocephala grown on the tailings with a topsoil cover of 8‐cm was the most dominant species. Lead was accumulated in root, branch, stem bark, and xylem, which accounted for more than 80% of the total metal concentration in the plant. This portion of Pb will reside in the plant for a long period, while the smaller portion of Pb in the leaf (about 15%) could be returned to the environment as litter during growth. Woody plants may have an advantage in metal‐phyto‐remediation over herbaceous plants.
Restoration of a Landfill Site in Berlin, Germany by Spontaneous and Directed Succession
Authors: Rebele Franz , Lehmann Cornelia 
Published: March 2003

AbstractWe report on spontaneous and directed succession on a dry sandy landfill site of low fertility at Berlin‐Malchow, Germany. Changes in species composition and cover were followed on unmown and mown permanent plots of 2 × 2 m size through 5 years of vegetation development. Species richness on unmown plots was relatively constant during the time of observation, with 20 to 25 species per 4 m2. Total cover of unmown plots continuously increased from approximately 10% in the first year to 80% in the fifth year. There are no clearly discernible sequential successional stages until present. The species composition includes species of all life forms, which colonized the site immediately after the initiation of the succession process representing the initial floristic composition type of vegetation development. However, perennial grasses and herbs gradually increased in cover up to approximately 40%. Woody plants were also present from the first year of succession and increased up to more than 20% cover in the fifth year, forming a shrub layer (>0.5 m) after the second year. Mowing significantly increased species richness, which was evident from the third year onward. This effect was mainly due to the reduction of the tall perennial grass Calamagrostis epigejos. Solidago canadensis and woody species were also significantly affected (lower cover and height), whereas short perennial herbs like Plantago lanceolata and Trifolium repens benefited from mowing.
Patterns of Species Richness and Composition in Re‐Created Grassland
Authors: Sluis William J. 
Published: March 2003

AbstractThe success of many prairie restorations is not well documented. A restoration begun in 1975 at the Fermi National Accelerator Laboratory near Chicago, Illinois allows assessment of restoration efforts as well as changes through time. Data are presented on species richness and composition for 13 restorations planted in successive years between 1975 and 1990 and two remnant prairies. Presence of species was recorded using a stratified random design. Species richness at several scales and non‐metric multidimensional scaling ordination were used to assess trends in the vegetation. Species richness declined through time at all scales examined and was always less in the restored prairies than that found in the remnant prairies. Species composition changed with time but not in the direction of the composition found in the remnants. Our understanding of the maintenance of species richness is not sufficient to allow the re‐creation of patterns of species found in remnant grassland communities.
An Assessment of a Small Urban Stream Restoration Project in Northern California
Authors: Purcell Alison H. , Friedrich Carla , Resh Vincent H. 
Published: March 2003

AbstractStream restoration projects have become increasingly common, and the need for systematic post‐project evaluation, particularly for small‐scale projects, is evident. This study describes how a 70‐m restored reach of a small urban stream, Baxter Creek (in Poinsett Park, El Cerrito, California), was quickly and inexpensively evaluated using habitat, biological, and resident‐attitude assessments. The restoration involved opening a previously culverted channel, planting riparian vegetation, and adding in‐stream step‐pool sequences and sinuosity. Replicated benthic macroinvertebrate samples from the restored site and an upstream unrestored site were compared using several metrics, including taxa richness and a biotic index. Both biological and habitat quality improved in the restored compared with the unrestored section. However, when compared with a creek restored 12 years before, habitat condition was of lower quality in the recently restored creek. A survey of the neighborhood residents indicated that, overall, they were pleased with the restored creek site. The approach used in this demonstration project may be applicable to other small‐scale evaluations of urban stream restorations.
Decomposition of Sarcocornia quinqueflora on an Iron‐Smelting Slag Substrate
Authors: Dick T. M. , Streever W. J. , Osunkoya O. O. 
Published: March 2003

AbstractRestoration of salt marsh habitat is becoming more common in Australia. However, little is known about restoring salt marshes on substrates contaminated by slag from iron smelting, which could affect microbial activity. This study, conducted near Newcastle, Australia, compares initial C, N, and P mass and decomposition of Sarcocornia quinqueflora (glasswort or samphire) from (1) a restoration site with a slag‐and‐mud substrate, (2) the restoration site's donor marsh, and (3) other nearby sites sampled to provide information on background variability. A litterbag technique with a 180‐day incubation period was used to quantify total, C, N, and P mass losses from decomposition. Although there were significant differences between sites in initial N mass and loss of C and P over the period of our study, the presence of slag did not slow decomposition rates as measured using litterbags. Further work is needed to assess other aspects of wetland structure and function on slag substrates.
Biological Weighting Functions for the Effect of UV Radiation on Carbon Partitioning in Microalgae
Authors: Franklin L. A. , Neale P. J. 
Published: March 2003

AbstractUV radiation clearly inhibits phytoplankton photosynthesis, with direct effects on both photosystem II and the enzyme, Rubisco, that catalyses the first reaction of the photosynthetic carbon reduction cycle. The subsequent partitioning of fixed carbon into macromolecular pools (carbohydrates, lipids, and proteins) is also affected by UV exposure, although relative changes in allocation are not well‐documented and vary considerably. The wavelength specificity of inhibition of photosynthesis has been described by spectral weighting functions, or biological weighting functions (BWFs) that combine the effect of UV radiation with interactive effects of longer wavelengths. BWFs permit one to compare the effects of different radiation sources or various ozone depletion scenarios. However, no data are available from which BWFs for partitioning can be determined, as experimental techniques have varied widely. These BWFs are essential for predicting the effects of increased UV‐B on other trophic levels, and for analyzing the cost and benefit of synthesizing protective compounds. Using a polychromatic approach, we are developing BWFs for the partitioning of 14C in Thalassiosira pseudonana (3H) at photosynthetically saturating irradiance. We are comparing these functions to BWFs calculated from simultaneous measurements of primary productivity. We have found consistent differences in sensitivity to UV exposure among the pools, and are testing these differences for significance using a variety of model and calculation approaches.
Three New Species of Gracilariopsis (Gracilariales, Rhodophyta) From the North‐Western Atlantic
Authors: Gurgel C. F. D. , Fredericq S. 
Published: March 2003

AbstractA recent molecular phylogenetic study inferred from chloroplast‐encoded rbcL sequence analyses based on 20 specimens of Gracilariopsis. Dawson 1949 worldwide confirmed the monophyly of the genus and revealed the existence of three new Caribbean species (Gurgel et al. J. Phycol., submitted). Gracilariopsis sp. 1 collected in the Mexican Gulf of Mexico is sister to G. tenuifrons. Gracilariopsis sp. 2 collected in Caribbean Panama (Colón City) and Venezuela (Paraguana Península) is morphologically closely related to G. panamensis. Gracilariopsis sp. 3 collected in Venezuela (La Vela de Coro) is distinct from all other terete and stringy species that characterize the genus by being a flat‐foliose taxon; it also shows a basal topology with uncertain phylogenetic relationship to an undetermined species from Japan and China and to G. heteroclada from the Philippines. The lack of clear‐cut vegetative and reproductive features among the species coupled with a high degree of thallus plasticity may account for the fact that genetically distinct species were not previously recognized as taxonomically distinct. Our molecular and morphological studies reveal that the diversity of Gracilariopsis species in the western Atlantic and probably in the rest of the world is currently underestimated. Morphologically detailed descriptions for all three new species are provided.
Bioassessment of Stream‐Water Quality Using Benthic and Planktonic Algae Collected Along an Urban Intensity Gradient in the Eastern Cornbelt Plains Ecoregion, Ohio, USA
Authors: Hambrook J. A. 
Published: March 2003

AbstractAlgae possess many attributes that make them ideal organisms to employ in water‐quality investigations. They are ubiquitous, ecologically important, and sensitive to a broad range of stressors; moreover, they respond rapidly to changes in water quality. As part of the USGS National Water Quality Assessment (NAWQA) Program, two methods of analyzing stream‐dwelling algae were used to assess relations among nutrient concentrations, algae, and overall biological integrity of streams along a gradient from agricultural to urban land cover. One method is based on algal production (chlorophyll a, biomass, and 48‐h measures of dissolved oxygen), whereas the other is based on algal community assemblages (species abundance, biovolume, and autecology). Quantitative periphyton and phytoplankton samples were collected from 30 stream reaches in small watersheds (drainage area 7.7–188.7 km2) in south‐west Ohio, during July 2000. Phytoplankton Chl a ranged from 0.5 mg/L in an urban area to 43 mg/L in an agricultural basin, whereas the epilithic periphyton Chl a ranged from 2 mg/m2 in an urban area to 142 mg/m2 in an agricultural basin. Spearman correlations were used to indicate relations between the physical, chemical, and biological factors and measures of algal production. Multivariate analysis of algal species abundance and metrics will be used to characterize gradients of algal community response relative to chemical and landscape factors. Results will be discussed in relation to the influence of urban land‐use intensity and the US Environmental Protection Agency nutrient criteria proposed for this region. The extent to which the algal production and community structure results are useful for bioassessment of stream health will be evaluated with regard to understanding community responses to organic enrichment, dissolved oxygen, specific conductance, light availability, pesticide concentrations, and the monitoring of watershed management practices.
Impacts of Reduced Salinity on Seagrasses in Indian River Lagoon
Authors: Hanisak M. D. 
Published: March 2003

AbstractFrom November 1993 to November 1995, a study was conducted in Indian River Lagoon (IRL) to determine relationships of light attenuation, water quality, and seagrass at sites representing a range of water quality conditions. There were considerable interannual differences at the sites. The most striking event occurred at a station in northern Banana River, an area of IRL considered the least anthropogenically impacted. This station had a well‐developed, multispecies seagrass bed (Halodule wrightii and Syringodium filiforme, with small quantities of Halophila englemannii). Throughout the first year, salinity was stable (90% of weekly values ranged from 26 to 32 ppt). Beginning in November 1994, the cover, shoot density, and biomass of all three species declined precipitously due to sharply reduced salinities associated with high rainfall and run‐off. Salinities during the following year varied little and remained low (90% of weekly values ranged from 13.5 to 19.8 ppt). The lack of recovery to earlier salinity levels was due to the long residence time (about 1 year) in that portion of IRL. Seagrass cover, shoot density, and biomass reached minima in May 1995. By August 1995, Halodule began to recover, but nearly 8 years later, Syringodium has not recovered to 1994 levels.
Synchrotron‐Based Infrared Imaging of Euglena Gracilis Single Cells
Authors: Hirschmugl C. , Bunta M. , Holt J. , Giordano M. , Skilirov A. , Strickler J. R. 
Published: March 2003

AbstractInfrared (IR) microspectroscopy is used to examine and identify the chemistry in individual living cells of Euglena gracilis. The spectra provide relative concentrations of lipids, proteins and carbohydrates in the specimen. Diffraction‐limited, spatially resolved IR images of single cells of the microalga were measured using synchrotron radiation as a bright IR source. These contour maps reveal the distributions of the proteins, lipids and carbohydrates including the phospholipids, sugars and paramylon. We compare the images with the biochemistry for E. gracilis. We also present the IR images for two different cells, which were exposed to different culture conditions prior to the measurements. The overall trends observed for the two specimens are in qualitative agreement with the hypothesis that there was a significantly reduced concentration of nitrogen in the culture as a function of time. Importantly, this study demonstrates the potential to examine changes in the chemistry of living cells while modifying environmental stimuli.
Chlororespiration in Green Algae Isolated From Desert Crusts
Authors: Lewis L. A. , Cardon Z. G. , Tyser D. 
Published: March 2003

AbstractPhotosynthetic organisms enduring extreme temperatures, low water availability, or high light require photoprotective mechanisms to prevent sustained damage to photosynthetic machinery. Green microalgae living in desert crust communities of the south‐western US experience all these environmental stresses, yet photophysiological studies of green algae in the literature have focused on only a handful of common aquatic and marine species. We are examining the variation in green algal photoprotective mechanisms that is the result of natural selection acting independently in multiple lineages of highly diverse desert green algae (Chlorophyta) within the classes Chlorophyceae and Trebouxiophyceae. We have found that unusually extensive dark reduction of the plastoquinone pool is a prominent photophysiological feature among these desert algae; this reduction may be linked with enhanced chlororespiration. Recently, chlororespiration in higher plants has been linked through mutant analysis to control of the carotenoid synthetic pathway, heat stress, and starch metabolism among other pathways, though the function of chlororespiration remains controversial. Given that green algae and higher plants are monophyletic, analysis of potential chlororespiration in desert green algae may help decipher the evolution of the chlororespiratory process as well as its potential role in photoprotection in desert habitats.