Upland Edge Research Articles

Riparian Groundwater Nitrogen (N) Isotopes Reveal Human Imprints of Dams and Road Salt Salinization

AbstractGroundwater nitrate‐N isotopes (δ15N‐) have been used to infer the effects of natural and anthropogenic change on N cycle processes in the environment. Here we report unexpected changes in groundwater δ15N‐ for riparian zones affected by relict milldams and road salt salinization. Contrary to natural, undammed conditions, groundwater δ15N‐ values declined from the upland edge through the riparian zone and were lowest near the stream. Groundwater δ15N‐ values increased for low electron donor (dissolved organic carbon) to acceptor ratios but decreased beyond a change point in ratios. Groundwater δ15N‐ values were particularly low for the riparian milldam site subjected to road‐salt salinization. We attributed these N isotopic trends to suppression of denitrification, occurrence of dissimilatory nitrate reduction to ammonium (DNRA), and/or effects of road salt salinization. Groundwater δ15N‐ can provide valuable insights into process mechanisms and can serve as “imprints” of anthropogenic activities and legacies.

The role of temperate treed swamps as a carbon sink in southwestern Nova Scotia

Forested wetlands may represent important ecosystems for mitigating climate change effects through carbon (C) sequestration because of their slow decomposition and C storage by trees. Despite this potential importance, few studies have acknowledged the role of temperate treed swamps in the C cycle. In southwestern Nova Scotia, Canada, we examined the role of treed swamps in the soil C cycle by determining C inputs through litterfall, assessing decomposition rates and soil C pools, and quantifying C outputs through soil greenhouse gas (GHG) emissions. The treed swamps were found to represent large supplies of C inputs through litterfall to the forest floor. The swamp soils had substantially greater C stores than the swamp–upland edge or upland soils. We found growing season C inputs via litterfall to exceed C outputs via GHG emissions in the swamps by a factor of about 2.5. Our findings indicate that temperate treed swamps can remain a C sink even if soil GHG emissions were to double, supporting conservation efforts to preserve temperate treed swamps as a measure to mitigate climate change.

Herbivory patterns along the intertidal gradient of Juncus roemerianus salt marshes

Grasshopper herbivory can vary substantially among locations within a salt marsh or among marshes, but its variability along the marsh intertidal gradient (extending from the shoreline to the upland fringing forest) is not well reported. Previous papers have shown that grasshopper herbivory may affect nutrient processes in salt marsh ecosystems, but how such effects are tied up to the intensity of herbivory and how they vary spatially is poorly known. To help address these gaps, we evaluated whether grasshopper herbivory intensity and herbivore abundance together with other plant characteristics (such as total leaf length, plant live and dead biomass, plant nutrient content and plant nutrient standing stocks) varied along the intertidal gradient of two black needlerush marshes in the Northern Gulf of Mexico. Our results show that in one marsh grazing intensity decreased from the shoreline to the forest tree line, but in the other there was similar grazing intensity across the entire intertidal gradient. None of the measured plant characteristics followed the differences in herbivory found along the intertidal gradient and between salt marshes. We also found that, in the salt marsh with decreasing herbivory towards the upland edge, the combination of herbivory, plant nutrient content and plant nutrient standing stocks suggest two different functional zones along the intertidal gradient, one of nutrient availability and recycling near the shoreline and another one of nutrient inmobilization near the upland fringing forest. In concert, the results suggest that grasshopper herbivory intensity may vary along the intertidal gradient in some marshes, but not in others. In turn, spatial differences in herbivory along the intertidal gradient, if they occur, may influence nutrient processes, such as recycling and storage, leading to associated spatial differences in nutrient dynamics in the salt marsh.

Analysis of Sediments in the North-East Morainic Upland Edge Zone in the Vicinity of Piaski Pomorskie (West Pomerania, NW Poland)

Abstract the aim of this article is the description of lithofacies characteristics of sediments forming the north-east part of the morainic upland edge zone in the vicinity of Piaski Pomorskie (west Pomerania). the paper undertake also an attempt to reconstruct paleogeographical conditions of the formation of moranic uppland edge. The diversification of glaciofluvial and fluvial processes during the phase of stagnation and recession of uppervistulian ice-sheet in the vicinity of Piaski Pomorskie (western Pomerania) led to the formation of a morainic upland edge distinctly marked in morphology The edge zone separates the undulating moraine plateau from a lower situated Dębnica River Valley. This area is mostly formed by fine-grained sands with occasional layers of a coarser fraction of gravel and coarse- and medium-grained sands. The observed type of low-angle cross-stratification and trough cross-stratification indicates the dominance of diversified energy depositional environment with considerable power of water as transporting medium. the research area was formed at the front of the ice-sheet, which receded from the nearby reach of the Pomeranian Phase of the weichselian glaciation.

Distribution of elements in soil catenas developed in ice-dammed lake and in morainic landscapes in NE Poland

The research was carried out on a soil catena sequence, in three sections of river valleys: the Liwna and Guber rivers flowing through landscapes shaped by ice-dammed lakes on Sepopol Lowland, and the Łyna river in the morainic landscape of Olsztyn Lakeland. Along transects, from the upland edge towards the river bed, soil exposures were made, soil samples were collected, and the soil reaction, cation exchange capacity, content of organic carbon and total content of Ca, Fe, Mg, K, P, Na, Mn, Zn and Cu were analyzed. The soils of the landscape of ice-dammed lake origin contained more elements than the ones in the morainic landscape. In the catena, the highest cation exchange capacity and the highest content of macroand microelements were determined in Histosols and Fluvisols. Among the studied Fluvisols, the highest content of Ca (19.5 g kg-1), Mg (12.60 g kg-1), Fe (41.92 g kg-1), Mn (691.38 mg kg-1) was found in the soils of the Guber catena, and the highest content of K (13.00 g kg-1), Na (0.60 g kg-1), P (3.20 g kg-1), Cu (55.90 mg kg-1), Zn (271.46 mg kg-1) was in the soils of the Liwna catena. The amounts of the elements (except Fe and Mn) were statistically positively significantly correlated with the amount of organic carbon as well as the silt fraction 0.05-0.002 mm (all elements) and clay fraction <0.002 mm (Ca, K, Na, Fe, Mn). Fluvisols and Histosols in river valleys, owing to their high accumulation capacity, play a very important role in the circulation of elements and strengthen the resistance of landscapes of ice-dammed lake origin and morainic hills to human activity.

Macro‐Tidal Salt Marsh Ecosystem Response to Culvert Expansion

The purpose of this paper was to examine the vegetative, sedimentary, nekton and hydrologic conditions pre‐restoration and the initial 2 years post‐restoration at a partially restricted macro‐tidal salt marsh site. Replacement of the culvert increased tidal flow by 88%. This was instrumental in altering the geomorphology of the site, facilitating the creation of new salt marsh pannes, expansion of existing pannes in the mid and high marsh zones, and expansion of the tidal creek network by incorporating relict agricultural ditches. In addition, the increase in area flooded resulted in a significant increase in nekton use, fulfilling the mandate of a federal habitat compensation program to increase and improve the overall availability and accessibility of fish habitat. The restoration of a more natural hydrological regime also resulted in the die‐off of freshwater and terrestrial vegetation along the upland edge of the marsh. Two years post‐restoration, Salicornia europea (glasswort) and Atriplex glabriuscula (marsh orache), were observed growing in these die‐back areas. Similar changes in the vegetation community structure were not observed at the reference site; however, the latter did contain higher species richness. This study represents the first comprehensive, quantitative analysis of ecological response to culvert replacement in a hypertidal ecosystem. These data will contribute to the development of long‐term data sets of pre‐ and post‐restoration, and reference marsh conditions to determine if a marsh is proceeding as expected, and to help with models that are aimed at predicting the response of marshes to tidal restoration at the upper end of the tidal spectrum.

Paleogene basalts prove early uplift of Victoria's Eastern Uplands

Profiles of five Paleogene rivers reconstructed from basalts that flowed down them show a complex landscape. All five flow fields are in Victoria's Eastern Uplands, two in the Baw Baw region in the southwest and three in the Nunniong–Deddick region in the east. Three flow fields (Toorojil, Aberthomson, Timbuchan) originate on high plateaus (<1000 m), from which they descend steadily via deeply incised valleys to lowland settings of below 200 m. Local topography at the edge of the upland plateaus shows Paleogene basalt lying between 650 and 900 m below adjacent mountain peaks, proving that the Paleogene streams were deeply incised. Two additional Paleogene (Eocene, ∼38–42 Ma) basalt fields in the Nunniong–Deddick region (Butrindal and Bondick) indicate that the Eocene Snowy River valley's base was overlooked by mountains up to 800–1050 m higher. In the Baw Baw region, the Paleogene northern edge of the Gippsland Plains is marked by an upland front at which Paleogene basalts debouch onto and spread over pre-basaltic alluvial fans. Pliocene alluvial fans overlying the basalt debouch from the same positions, showing that there has been no significant Neogene shift of the upland's edge. The Paleogene landscape contained all major geomorphic elements visible today: high plateaus bordered by steep escarpments that were breached by deep valleys that descended to dissected lowlands, debouching onto alluvial fans of the Gippsland Plain. The Paleogene landscape is best viewed as a snapshot taken during the prolonged evolution of the landscape. The uplift must therefore be considerably older, and is tied to the onset of major sedimentation into the receiving basins of the Southern Rift System at 93 Ma (Cenomanian), also recorded as a regional cooling event in apatite fission-track ages.

Holocene Environmental History and Evolution of a Tidal Salt Marsh in San Francisco Bay, California

Analyses of three sediment cores collected from a tidal salt marsh located on the western edge of San Pablo Bay in the San Francisco Bay estuary have produced long-term records of late Holocene marsh development. The records from these cores include a suite of elements, organic carbon content, fossil seeds, pollen, and stable carbon isotopes. The stratigraphy indicates fresher water conditions than present between 3400 and 2000 cal YBP. A tidal marsh became established at China Camp after about 2000 cal YBP; between 2000 cal YBP and approximately 700 cal YBP, conditions in the estuary were apparently more saline and variable. This interval was terminated by at least three or possibly five flood events, as evidenced by coarse clastic materials most likely washed down from the surrounding uplands. These floods represent high rainfall events, possibly El Niño years, and occurred during the late Medieval Climatic Anomaly. Greater plant diversity and pollen from some species with low salt tolerance are found in a core collected near the upland edge of the marsh and date to about 200 years ago, suggesting fresher conditions than today. Over the past 50 years, the diversity of marsh vegetation has decreased, and salt tolerant plants (especially Salicornia virginica) have become the dominant species. These changes are likely a result of the impacts of water diversions and upstream dams in the San Francisco Bay watershed.

HOW WELL CAN WE MODEL NUMBERS AND PRODUCTIVITY OF SALTMARSH SHARP-TAILED SPARROWS (AMMODRAMUS CAUDACUTUS) USING HABITAT FEATURES?

Abstract Habitat models are often used to describe species distributions, but they need to be tested to evaluate their predictive performance. We investigated the importance of model evaluation in a study of habitat selection by Saltmarsh Sharp-tailed Sparrows (Ammodramus caudacutus), a species of conservation concern in eastern North America. We estimated the number of birds, nests, and fledglings produced in thirty 1-ha study plots spread across multiple marshes and used an information-theoretic approach to select among explanatory habitat models. Model performance was evaluated using both the original data set and data from another 30 plots from the same set of marshes. Our models indicate that both female and male Saltmarsh Sharp-tailed Sparrows increase in abundance as one moves away from the marsh's upland edge and in areas where there is deep thatch and uniform vegetation height. In contrast to the results for adult birds, number of nests and production of fledglings were positively associated with...

Impacts of Seawalls on Saltmarsh Plant Communities in the Great Bay Estuary, New Hampshire USA

Seawalls are often built along naturally dynamic coastlines, including the upland edge of salt marshes, in order to prevent erosion or to extend properties seaward. The impacts of seawalls on fringing salt marshes were studied at five pairs of walled and natural marshes in the Great Bay Estuary of New Hampshire, USA. Marsh plant species and communities showed no difference in front of walls when compared with similar elevations at paired controls. However, seawalls eliminated the vegetative transition zone at the upper border. Not only did the plant community of the transition zone have high plant diversity relative to the low marsh, but it varied greatly from site to site in the estuary. The effects of seawall presence on other marsh processes, including sediment movement, wrack accumulation, groundwater flow, and vegetation distribution and growth, were examined. Although no statistically significant effects of seawalls were found, variation in the indicators of these processes were largely controlled by wave exposure, site-specific geomorphology and land use, and distance of the sampling station from the upland. Trends indicated there was more sediment movement close to seawalls at high energy sites and less fine grain sediment near seawalls. Both trends are consistent with an increase in energy from wave reflection. The distribution of seawalls bordering salt marshes was mapped for Great and Little Bays and their rivers. Throughout the study area, 3.54% of the marshes were bounded by shoreline armoring (5876 m of seawalls along 165.8 km of marsh shoreline). Localized areas with high population densities had up to 43% of marshes bounded by seawalls. Coastal managers should consider limiting seawall construction to preserve plant diversity at the upper borders of salt marshes and prevent marsh habitat loss due to transgression associated with sea level rise.

Principles of planning and establishment of buffer zones

Good management of the uplands is essential and effective buffer zones along the streams draining the basin will complete the task of water quality protection. Most basin drainage moves through the riparian zones of first- and second-order headwaters streams. It is important to have continuous buffers on both sides of these streams. For larger streams, protect the flood plains. Several zones of buffer vegetation are most effective. A narrow grass strip at the upland edge traps suspended particulates and phosphorus. A wider zone of woody vegetation traps nitrate, and both cools and provides natural organic matter to the receiving waters. Contour the buffer surface to avoid concentrated storm flows and periodically remove sediment berms that develop. For a completely degraded riparian zone, it is essential to provide soils of the right porosity and organic carbon content. Sub-soils need to be permeable and to have a reasonable groundwater retention time. High organic carbon is required to develop a low redox potential. Provide short-term protection from erosion. Only add native species. Sometimes, exotic plants get established and must be eradicated. Fence livestock out. Control excessive activity by wild ungulates, voles, and beaver.

Mid- to late-Holocene vegetation history of Greater Exmoor, UK: estimating the spatial extent of human-induced vegetation change

This paper presents the results from three pollen profiles from a group of small spring mire sites on the southern edge of Exmoor in south west England. The size and topography of these sites allow detailed local landscape histories around each site to be reconstructed which broadly cover the mid- to late-Holocene. Comparison of the individual local landscape histories demonstrates the scale of spatial variation in vegetation around the upland edge, and facilitates understanding of human-landscape interactions from the early Neolithic onward. In the early Neolithic significant short-term woodland disturbance is recorded around the upland fringe, including clearance of oak-hazel-elm woodland, suggesting that the shift from Mesolithic to Neolithic is not marked by a gradual environmental transition. Following this, there is clear evidence of Neolithic management of upland heath using fire, presumably for the management of upland grazing. Woodland clearances are recorded throughout the later Prehistoric period; however, the use of multiple profiling suggests that woodland clearance is spatially discrete, even within an area of 4 km2. Pastoral land use is dominant around the uplands until around 900–1,000 a.d., and there is no discernible Roman or post-Roman period impact in the vegetation, suggesting cultural stability from the late Iron Age to the early Medieval period. By 1,100 a.d., there is a shift to mixed arable-pastoral farming which appears to continue well into the post-Medieval period.

Seed-bank and vegetation development in a created tidal freshwater wetland on the Delaware River, Trenton, New Jersey, USA

The initial stages of seed-bank and vegetation development were documented in a newly created tidal freshwater wetland where donor soils were not applied. The 32.3-ha site adjacent to the Delaware River in New Jersey, USA was completed in stages from November 1993 to November 1994. Objectives of the study were to determine characteristics of the seed bank and vegetation and to monitor spatial and temporal changes. The study was carried out from 1995 to 1999 using three sites (North, East, and South Marshes) and three elevation locations (1 m from a tidal channel, midpoint, and 1 m from the upland edge). Development of the seed bank and vegetation demonstrated tremendous colonization potential derived from regional and local sources. Colonization and complete plant cover occurred within one year, and subsequent changes were rapid. Individual species behaved uniquely regarding colonization time, duration, and decline in both the seed bank and vegetation. Large seed banks of some species were present even after decline in the vegetation. Overall, the seed bank was large, small-seeded and persistent, and diverse. A total of 177 species occurred in soil seed bank and 92 in field vegetation samples, with 72 contributing to cover. Seedbank densities (mean±SE/m2) ranged from 450±152 to 394,600±29,950. Species richness (species/ sample) ranged from 3.3±1.2 to 32.3±1.8. Density and species richness were clearly reduced by inundation and were lowest in channel edge samples and in the first year (1995). Cover species richness ranged from 1.6±0.2 to 7.3±0.6 per quadrat. Complexity of the vegetation increased over time, with lowest diversity along the channels. The 1995 site differences, with greatest densities and species richness in the East Marsh, could be related to site history (timing of construction). Species similarity between the seed bank and vegetation ranged from 11 to 53% and showed no site, location, or temporal pattern. However, similarity between sites of the seed bank and vegetation increased from 1995 to 1998. Several New Jersey State rare or threatened species, as well as invasive species, were present. Results indicated that it is ecologically feasible to create a wetland adjacent to a tidal freshwater river without use of donor soil and that transplantation had not been necessary.

Methane and Carbon Dioxide Flux from a Macrotidal Salt Marsh, Bay of Fundy, New Brunswick

Fluxes of methane (CH4) and carbon dioxide (CO2) to the atmosphere at 52 sites within a salt marsh were measured by a dark static chamber technique from mid July to mid September. Mean CH4 fluxes ranged from 0.2 mg m−2 d−1 to 11.0 mg m−2 d−1, with an overall average of 1.6 mg m−2 d−1. Flux of CH4 was inversely correlated (r2=0.23, p = 0.001) with salinity of the upper porewater at the site, suggesting the dominant role of SO42− in inhibiting methanogenesis in salt-marsh sediments. The combination of salinity and water table position was able to explain only 29% of the variance in CH4 emission. Mean soil flux of CO2 ranged from 0.3 g m−2 d−1 to 3.7 g m−2 d−1, with an overall average of 2.5 g m−2 d−1; it was correlated with aboveground biomass (positive, r2=0.38, p = 0.001) and position of the water table (negative, r2 = 0.55, p = 0.001). The combination of biomass and water table position accounted for 63% of the variance in CO2 flux. There were high variations in gas flux within the six plant communities. The sequences were CH4: upland edge > panne > pool > middle marsh > low marsh > high marsh, and CO2: middle marsh > low marsh > upland edge > high marsh > panne > pool. Compared to other salt-marsh systems, this Bay of Fundy marsh emits small amounts of CH4 and CO2.

Intertidal distribution, population dynamics and production of the amphipod Uhlorchestia spartinophila in a Georgia, USA, salt marsh

The talitrid amphipod Uhlorchestia spartinophila Bousfield and Heard occurs in close association with the smooth cordgrass Spartina alterniflora Loisel in salt marshes along the U.S. Atlantic coast. In order to assess its potential as a prey resource for secondary consumers, we followed the population and production dynamics of this amphipod from 3 November 1990 to 2 October 1991 in a salt marsh on Sapelo Island, Georgia. Semimonthly samples were taken along an intertidal transect, which extended from a vegetated creekbank levee landward 140 m to a site near the upland edge of the marsh. Amphipod densities ranged from 9 to 826 indm-2 and were greatest in the levee and high marsh habitats at opposite ends of the transect. The highest densities occurred in March to May and the lowest in November and December. Specific growth rates, which ranged from 0.001 to 0.024 mm mm-1 d-1 length and 0.003 to 0.068 mg mg-1 d-1 AFDW (ash-free dry weight), were least in winter and decreased with increasing amphipod size. Although some reproduction occurred year-round, most of the population's reproductive output was from January to May, when adults had the greatest size-specific mass. Sex ratio usually favored females, which were larger than males. Minimum adult female size was 5.4 mm total length (TL). Broods included from 1 to 28 eggs or young and increased with increasing body size, averaging 7.4 young for an average-size female of 7.6 mm TL. Annual production, which ranged from 0.769 to 1.444 g AFDW m-2, was least in the low marsh and greatest in the levee habitat. Production:biomass ratios were 15.4 to 17.3 in different habitats. Such high turnover rates, together with the population's broad intertidal distribution, suggest a greater contribution to trophic dynamics than is implied by the relatively low standing stock biomass of U. spartinophila in this marsh system.

Effects of neighbors on growth and mortality of mangrove seedlings in Florida, U.S.A.

Changes in height and mortality rates of red mangrove (Rhizophora mangle), black mangrove (Avicennia germinans), and white mangrove (Laguncularia racemosa) seedlings were measured in three field stands for 45 months. Differences between stands and the effects of size and distance of neighboring trees on individual growth rates were examined. Trees in a ditechside stand demonstrated higher growth rates than those near the upland edge, which in turn, grew faster than those in the high marsh proper. Mortality rates for red, black, and white mangroves were 9.6%, 4.6%, and 3.2% per year, respectively, whereas height increment rates ranged from 28.5–131.3 cm per year. Moderate salinities and lack of interference from mature trees are considered partially responsible for the relatively low mortality and high growth rates observed. The only consistent effects of neighborns on changes in height of subject trees were positive. This result is attributed to shared environmental conditions between neighboring trees.

Physiography and vegetation zonation of shallow emergent marshes in southwestern Florida

Twenty-four fresh marsh-wet prairie wetland sites in southwestern Florida were studied with respect to vegetation zonation, substrate characteristics, and morphometry. Six major wetland zones were identified. TheHypericum zone occupied the shallowest position (closest to the upland edge) and was confined to sandy substrates. ThePanicum-Rhynchospora zone typically followed downslope and was also associated with sandy substrates. TheMixed Emergent,Cladium,Cephalanthus andFraxinus-Salix zones all occurred on organic soils in wetland interiors. In addition to depth and substrate type, other important determinants of zone composition included fire and disturbance due to feral hog rooting and cattle grazing.

Patterns in the utilization of the intertidal salt marsh by larvae and juveniles of Fundulus heteroclitus (Linnaeus) and Fundulus luciae (Baird)

Larval and juvenile fishes were collected at low tide from the surface of an intertidal salt marsh on Sapelo Island, Georgia every 6 days from 25 May through 20 December 1982. Larval fishes were present in shallow puddles of tidal water on the marsh from the beginning of the sampling period until the end of October. Juveniles were present throughout the year. Fundulus heteroclitus (Linnaeus) and F. luciae (Baird) accounted for 96.3% (67.0% and 29.3%, respectively) of the 4355 fishes collected. These fishes exhibited synchronous, temporal pulses in larval abundance, suggesting that reproduction was discontinuous and controlled by the same factor(s) in both species. Larval F. heteroclitus inhabited aquatic micro-habitats near the upland edge of the intertidal marsh, but as the larvae grew to juvenile size (≈ 10 mm standard length) they moved to lower elevations near a tidal creek. Large juveniles and adults of F. heteroclitus infrequently occurred in the samples, presumably because they leave the intertidal marsh as the tide ebbs. F. luciae were rarely found in low marsh areas, but all age classes (including adults) occurred at higher elevations, supporting previous suggestions that this species prefers high marsh habitats. The vegetated, intertidal salt marsh appears to be the principal nursery habitat for both of these cyprinodontid species.

A Note on the Relation of Size to Ecological Value of Some Wetlands

Marshes located on the Mayo Peninsula between the South and Rhode rivers, Maryland, were measured to determine acreage per tract, total upland and seaward edge lengths. For these marshes, 54% of the total area is associated with tracts of less than 5 acres. Of total upland edge length, 68% is along tracts less than 5 acres, while 72% of seaward edge length is associated with these smaller tracts. Comparison of edge length to area ratios shows that tracts of 1 acre or less have significantly higher edge length than tracts of 5 acres or more. While this should be extrapolated to other geographic regions with care, the findings suggest that regulatory agencies revise wetland management principles to include greater protection and enhanced survival of small tracts.