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Glenn R. Guntenspergen

Publications and source records attributed to Glenn R. Guntenspergen.

At least 109 records · Page 6Linked to original sources
USGS2005

Salt tolerance underlies the cryptic invasion of North American salt marshes by an introduced haplotype of the common reed Phragmites australis (Poaceae)

A distinct, non-native haplotype of the common reed Phragmites australis has become invasive in Atlantic coastal Spartina marshes. We compared the salt tolerance and other growth characteristics of the invasive M haplotype with 2 native haplotypes (F and AC) in greenhouse experiments. The M haplotype retained 50% of its growth potential up to 0.4 M NaCl, whereas the F and AC haplotypes did not grow above 0.1 M NaCl. The M haplotype produced more shoots per gram of rhizome tissue and had higher relative growth rates than the native haplotypes on both freshwater and saline water treatments. The M haplotype also differed from the native haplotypes in shoot water content and the biometrics of shoots and rhizomes. The results offer an explanation for how the M haplotype is able to spread in coastal salt marshes and support the conclusion of DNA analyses that the M haplotype is a distinct ecotype of P. australis .

Marine Ecology Progress Series↗
USGS2004

Seasonal methane emissions by diffusion and ebullition from oligohaline marsh environments in coastal Louisiana

Methane is an important atmospheric greenhouse gas that is emitted from many natural and anthropogenic sources. In order to evaluate the global methane budget, precise data are needed from the diverse sources including coastal wetlands. Over 100 time-series determinations of methane emissions from an oligohaline wetland (brackish marsh) in coastal Louisiana show large variability during five seasonal sampling periods. Emission by both diffusion and ebullition (bubbles) was measured, however, neither of these emission modes were strongly dependent on either water depth or temperature (except in winter). Methane emission to static collectors placed over plants ( Scirpus olneyi and Spartina patens ) was not significantly different from shallow open water or mud. However, considerable heterogeneity in methane emissions and processes occurs even at a single site. Thus, establishing a reasonable estimate of the overall methane emission for a particular marsh environment and season requires multiple measurements at several sites. The average emissions for April, May, July, and September ranged from 31 to 54 mg/m2/h (744–1296 mg/m 2 /day). This can be separated into emissions from diffusion ranging from 8.3 to 20 mg/m 2 /h (18–50% of total) and emissions due to ebullition of 20–44 mg/m /h (50–82%). January emissions were much lower, amounting to 0.2 mg/m 2 /h (6 mg/m 2 /day), mainly by diffusion with only one episode of ebullition. Extrapolating these data to annual emissions gives total annual methane emissions of 203 g/m 2 /yr (61 g/m 2 /yr by diffusion and 142 g/m 2 /yr by ebullition).

Book chapter↗
USGS2003

An integrated analysis of the effects of past land use on forest herb colonization at the landscape scale

A framework that summarizes the direct and indirect effects of past land use on forest herb recolonization is proposed, and used to analyse the colonization patterns of forest understorey herbaceous species in a 360-ha mixed forest, grassland and arable landscape in the Dijle river valley (central Belgium). Fine-scale distribution maps were constructed for 14 species. The species were mapped in 15 946 forest plots and outside forests (along parcel margins) in 5188 plots. Forest stands varied in age between 1 and more than 224 years. Detailed land-use history data were combined with the species distribution maps to identify species-specific colonization sources and to calculate colonization distances. The six most frequent species were selected for more detailed statistical analysis. Logistic regression models indicated that species frequency in forest parcels was a function of secondary forest age, distance from the nearest colonization source and their interaction. Similar age and distance effects were found within hedgerows. In 199 forest stands, data about soils, canopy structure and the cover of competitive species were collected. The relative importance of habitat quality and spatio-temporal isolation for the colonization of the forest herb species was quantified using structural equation modelling (SEM), within the framework proposed for the effects of past land use. The results of the SEM indicate that, except for the better colonizing species, the measured habitat quality variables are of minor importance in explaining colonization patterns, compared with the combination of secondary forest age and distance from colonization sources. Our results suggest the existence of a two-stage colonization process in which diaspore availability determines the initial pattern, which is affected by environmental sorting at later stages.

Journal of Ecology↗
USGS2003

Differences in distribution of modified basins and ducks relative to roadside transects

Wetland basins in the Prairie Pothole Region of the U.S. are commonly modified by excavation (e.g., roadside ditches, stock dugouts), partial drainage (ditching), and diking. Differences in the distribution of modified wetlands may affect the predictive accuracy of waterfowl survey data if such wetlands are not distributed randomly in the landscape and if waterfowl are not distributed equally among them. We used data collected on thirty-eight 40-km2 plots in North Dakota to examine the distribution of modified basins relative to roadside transects and their use by five species of dabbling ducks in 1995. The 800-m-wide transects were subdivided into an inner 400-m transect, centered on the road, and the remaining outer transect area. We compared the distribution of modified and natural wetland basins among three sample areas: 1) the inner 400-m wide roadside transect area, 2) the outer transect area, and 3) the remaining area within the 40-km2 plot that was outside of the transects (outer plot). Duck use was compared between the two transect areas. The plots contained 20,582 basins, of which 88.5% were unmodified, 7.5% were excavated, 3.7% were partially drained, and 0.2% were diked. Nearly all excavated temporary (89%) and seasonal (90%) basins occurred in the inner transect area, reflecting the high proportion of basins that would be defined as roadside ditches. Excavated semipermanent basins were more evenly distributed among the outer plot and two transect widths; these basins often were dugouts but also included roadside ditches. Partially drained and diked basins also were fairly evenly distributed among the three sample areas. Semipermanent basins had greater use by mallards (Anas platyrhynchos) and northern pintails (A. acuta) when they were partially drained than when they were excavated or unmodified; pintails also had greater use of partially drained seasonal basins. Use of wetland basins by gadwall (A. strepera), blue-winged teal (A. discors), and northern shovelers (A. clypeata) did not differ among water regimes or modification. We found no evidence to indicate that duck numbers determined from standard 400-m-wide roadside transects were biased relative to the larger landscape. However, pond counts derived from such transects were biased. Correlations of duck numbers to pond counts that exclude ditches or temporary basins would poorly reflect the response of ducks to available water.

Wetlands↗
USGS2002

Indicators of wetland condition for the Prairie Pothole Region of the United States

We describe a study designed to evaluate the performance ofwetland condition indicators of the Prairie Pothole Region (PPR)of the north central United States. Basin and landscape scaleindicators were tested in 1992 and 1993 to determine theirability to discriminate between the influences of grasslanddominated and cropland dominated landscapes in the PPR. Pairedplots were selected from each of the major regions of the PPR.Among the landscape scale indicators tested, those most capableof distinguishing between the two landscapes were: 1) frequencyof drained wetland basins, 2) total length of drainage ditch perplot, 3) amount of exposed soil in the upland subject to erosion,4) indices of change in area of wetland covered by water, and5) number of breeding duck pairs. Basin scale indicators includingsoil phosphorus concentrations and invertebrate taxa richnessshowed some promise; however, plant species richness was the onlystatistically significant basin scale indicator distinguishinggrassland dominated from cropland dominated landscapes. Althoughour study found a number of promising candidate indicators, oneof our conclusions is that basin scale indicators present anumber of implementation problems, including: skill levelrequirements, site access denials, and recession of site accessby landowners. Alternatively, we suggest that the use oflandscape indicators based on remote sensing can be an effectivemeans of assessing wetland integrity.

Environmental Monitoring and Assessment↗
USGS2001

Duck populations as indicators of landscape condition in the Prairie Pothole Region

The Prairie Pothole Region of the northern Great Plains is an important region for waterfowl production because of the abundance of shallow wetlands. The ecological significance of the region and impacts from intensive agriculture prompted the U.S. Environmental Protection Agency to select it as one of the first areas for developing and evaluating ecological indicators of wetland condition. We examined hypothesized relations between indicators of landscape and wetland conditions and waterfowl abundance on 45 40 km2 study sites in North Dakota for 1995-96. Landscape condition was defined a priori as the ratio of cropland area to total upland area surrounding wetlands. Measures of waterfowl abundance included estimated numbers of breeding pairs (by species and total numbers) and , a species-specific correction factor which effectively adjusts breeding pair estimates for annual or area-related differences in pond size. Landscape indicators and waterfowl measures varied among regions. Results indicated that most areas in the Coteau region are of much higher quality for ducks than those in the Drift Plain, and areas in the Red River Valley are of the poorest quality for ducks. Regression models demonstrated the impact of agricultural development on breeding duck populations in the Prairie Pothole Region. The most consistent landscape indicators of waterfowl abundance were percent of cropland and grassland. Models were inconsistent among years and species. The potential biotic indicators of landscape and wetland condition examined here would be appropriate for temporal trend analyses, but because of inherent geographic variability would not be appropriate for single-year geographic trend analyses without more extensive evaluations to improve explanatory models

Environmental Monitoring and Assessment↗
USGS2000

Effects of roadside transect width on waterfowl and wetland estimates

Strip transects located along roads are commonly used to estimate waterfowl populations and characterize associated wetland habitat. We used data collected in May and early June, 1995, on forty-five 40-km 2 plots in North Dakota to evaluate bias of 800-m and 400-m wide roadside transects for sampling wetlands relative to a larger (40-km 2 ) scale and to compare duck abundance at the two widths. Densities of all basins combined and of seasonal basins considered alone were biased high for both transect widths, but mean bias did not differ from zero for temporary or semipermanent basins. Biases did not occur when excavated seasonal and temporary basins (i.e., road ditches) were excluded from the sample. Mean basin density was higher for the inner (400-m) transect width than for the outer transect width (area remaining of the 800-m transect, outside of center 400-m width) for all basins combined and for seasonal and temporary basins. We detected an area-related bias in the occurrence of basins in transects: smaller basins (0.08–1.6 ha) were over-represented in transect samples by 2.9–6.5%, and larger basins (≥11 ha) were under-represented in 800-m transects by 7.3% and in 400-m transects by 16.3%. We compared the distribution of ducks relative to water conditions in the inner and outer transect widths to evaluate whether they were affected by proximity to the road. Mallards ( Anas platyrhynchos L.), northern pintails ( A. acuta L.), and gadwall ( A. strepera L.) responded to water conditions equally in the inner and outer transect widths, but northern shovelers ( A. clypeata L.) and blue-winged teal ( A. discors L.) responded more strongly to wetlands on the inner than the outer transect width, indicating that estimates of these species would be higher from a 400-m wide transect than from an 800-m wide transect. Differences in an adjustment index, used to account for the portion of basin obscured from view, were highly variable between inner and outer transect widths but did not indicate that use of wider transects was hampered by visibility. Biases of transect sampling need to be carefully considered when extrapolating wetland basin or duck densities from transects to larger landscape scales.

Wetlands↗
USGS1999

Hydrogeomorphic factors and ecosystem responses in coastal wetlands of the Great Lakes

Gauging the impact of manipulative activities, such as rehabilitation or management, on wetlands requires having a notion of the unmanipulated condition as a reference. And understanding of the reference condition requires knowledge of dominant factors influencing ecosystem processes and biological communities. In this paper, we focus on natural physical factors (conditions and processes) that drive coastal wetland ecosystems of the Laurentian Great Lakes. Great Lakes coastal wetlands develop under conditions of large-lake hydrology and disturbance imposed at a hiearchy of spatial and temporal scales and contain biotic communities adapted to unstable and unpredictable conditions. Coastal wetlands are configured along a continuum of hydrogeomorphic types: open coastal wetlands, drowned river mouth and flooded delta wetlands, and protected wetlands, each developing distinct ecosystem propertics and biotic communities. Hydrogeomorphic factors associated with the lake and watershed operate at a hierarchy of scales: a) local and short-term (seiches and ice action), b) watershed / lakewide / annual (seasonal water-level change), and c) larger or year-to-year and longer (regional and/or greater than one-year). Other physical factors include the unique water quality features of each lake. The aim of this paper is to provide scientists and managers with a framework for considering regional and site-specific geomorphometry and a hierarchy of physical processes in planning management and conservation projects.

Great Lakes↗
USGS1998

Vulnerability of coastal wetlands in the Southeastern United States: climate change research results, 1992-97

As part of the USGCRP research framework on coastal lands and ecosystems, the Biological Resources Division of the U.S. Geological Survey (National Wetlands Research Center) entered into partnership with Rice University, Louisiana State University, Duke University, Clemson University, University of Southwestern Louisiana, University of Georgia, and the Virginia Institute of Marine Studies (University of Virginia ) to (1) document the current state vulnerability of coastal ecosystems including an assessment of past changes in land cover, (2) develop an understanding of the processes which underlie these changes, and (3) predict the extent of future alterations to these habitats and the consequences for the sustainability of the resource and land base. This document summarized the initial findings of our collaborative efforts. Overall, the studies exemplify an integrated approach addressing questions at the species, community, and landscape levels of organization and focusing on factors related to hydroperiod, sea-level rise, disturbance events, and coastal marsh submergence.

Biological Science Report↗
USGS1995

Disturbance and recovery of the Louisiana coastal marsh landscape from the impacts of Hurricane Andrew

The impact of Hurricane Andrew on the Louisiana coastal landscape and the initial recovery of wetland plant communities was determined from extensive surveys of a large geographic region of coastal marsh near Atchafalaya Bay and intensive studies of an oligohaline marsh on Otter Bayou. Wind and water movements associated with the hurricane resulted in the formation of compressed marsh, thick sediment deposits, wrack deposition, areas of salt burning, and scour. No sites were entirely without some impact. Sediments were deposited over large areas of coastal marsh. Marsh sites near Atchafalaya Bay had the thickest post-storm accumulations documented, up to 16 cm on average, while inland marsh sites accumulated lesser amounts of sediments. The nature of the sediment deposited on the marsh surface varied with location relative to the path of the storm and sources of sediment. Lateral compression resulted in surface relief 5-10 times greater than normal surface relief. Plant cover quickly recovered in all hurricane impact types except for scour areas and areas of thick wrack accumulation. Shifts in species dominance occurred in laterally compressed areas and are related to increased elevations. These findings suggest that hurricanes result in a variety of impacts in coastal Louisiana marshes and that the heterogeneity of the coastal landscape contributes to the magnitude and distribution of these impacts.

Louisiana↗
USGS1993

The examination of a competition matrix for transitivity and intransitive loops

Recent examinations of competition matrices for transitivity (species A > species B > species C) have used techniques that can be subject to certain biases. First, recent theoretical and empirical analyses have shown that traditional measures of competitive performance are biased in favor of the larger species. It is argued that this size bias has the potential to bias analyses of transitivity. Second, analytical techniques used to test matrices for transitivity can be shown to be insensitive to the presence of intransitive loops. Techniques are presented for exploring both these types of erros and these techniques are illustrated using the results from a six-species study of marsh plants. In addition, two published studies are partially reanalyzed using a technique designed to detect intransitivities. Results for both the new data set as well as for the published data sets fail to reveal intransitivities. For the marsh plant study, the size bias associated with traditional measures of competitive success did not bias in favor of transitivity. We conclude (1) that the studies examined do not possess intransitive loops and (2) care must be taken in order to avoid biased analyses if intransitive loops are to be detected.

Oikos↗
USGS1992

Size bias in traditional analyses of substitutive competition experiments

The objective of this study was to examine the claim that traditional measures of competitive performance in substitutive experiments are biased towards larger plants. Results from a three-year diallele experiment of 6 marsh plant species were analyzed using both Relative Yields (a traditional analysis) and the Relative Efficiency Index (a recently proposed analysis presumed to be size-independent). In adddition, a mechanistic model of competition was used to explore the behavior of both methods of estimating competitive performance. Results from the three-year experiment showed that Relative Yields (RYs) were correlated with the initial sizes of plants for the first two years but not the third. By the third year, RYs were highly correlated with Relative Efficiency Index values (REIs) suggesting that the effects of initial size were eventually overcome. Model results showed that RYs are inherently biased in favor of larger plants during the early phases of competition while REIs are not. Further, model analysis confirmed that the size bias associated with RYs declines with increasing duration of the experiment. It is concluded that current generalizations about the relationship between plant size and competitive ability may be biased by the procedures used to analyze competition experiments.

Oecologia↗
USGS1991

Effects of site, landscape features, and fire regime on vegetation patterns in presettlement southern Wisconsin

The presettlement tree cover (1831–33) of 3 townships in a southern Wisconsin landscape was analyzed using original survey records. Four forest types were identified: closed forest, open forest, savanna, and prairie. Comparisons of vegetation types and landscape pattern were made between the east and west sides of the Pecatonica River, which bisects the landscape and could have acted as a natural fire barrier. West of the river, presettlement tree species richness and diversity were lower and trees were smaller in diameter and less dense than to the east. The major vegetation types to the west were prairie (42% of landscape) and savanna (40%), both fire-susceptible types. Prairie was more common on gentle slopes than on other landforms. To the east, the landscape was 70% forested (closed plus open forest). Here, prairie was more frequent on steep dry sites. These vegetation differences, including the contrasting landscape placement of prairie, are attributed to distinct site characteristics and to disturbance (fire) regimes, with the west likely having more frequent fires. In terms of the four vegetation types, the east landscape was more homogeneous, being dominated by closed forest (50%). West of the Pecatonica River, the landscape was more heterogeneous because of the high proportion of both prairie and savanna; however, in terms of flammability of vegetation, the west was essentially homogeneous (82% prairie plus savanna).

Wiscsonsin↗