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In Louisiana, salt marshes are being created in an effort to offset the large loss of such habitat that has occurred over the last 50 yr. Primary productivity is an important function and indicator of success for salt marsh creation and restoration projects. The aim of this study was to determine whether the aboveground and belowground productivity of the dominant salt marsh grassSpartina alterniflora in created marshes in southwest Louisiana began to approximate productivity levels in natural marshes, over time. Net annual aboveground primary productivity (NAPP) was measured by a harvest technique, while the ingrowth core method was used to estimate net annual belowground primary productivity (NBPP). NAPP levels were similar to those found in other, Louisiana salt marshes, while NBPP levels were similar to or higher than the reported range forS. alterniflora studied along the Atlantic and Gulf of Mexico coasts. NAPP tended to decrease as the created marshes aged, but the levels in the oldest, 19 year old, created marsh were still well above values measured in the, natural marshes. It was estimated that it would take 35 yr after marsh creation for NAPP in the created marshes to become equivalent to that in natural marshes. NBPP in the created marshes became equivalent to levels found in the natural marshes after 6–8 yr, but then belowground production increased with marsh age, reaching an asymptote that surpassed natural marsh levels. Equivalency in primary productivity has not been reached in these marshes. Elevation also affected productivity, as higher elevational sites with greater topographic heterogeneity had significantly lower aboveground and belowground biomass levels than those with elevations closer to mean sea level. This underscores the need to construct marshes so that their mean elevation and degree of topographic heterogeneity are similar to natural marshes. 相似文献
3.
Net primary production was measured in three characteristic salt marshes of the Ebre delta: anArthrocnemum macrostachyum salt marsh,A. macrostachyum-Sarcocornia fruticosa mixed salt marsh andS. fruticosa salt marsh. Above-ground and belowground biomass were harvested every 3 mo for 1 yr. Surface litter was also collected from each plot. Aboveground biomass was estimated from an indirect non-destructive method, based on the relationship between standing biomass and height of the vegetation. Decomposition of aboveground and belowground components was studied by the disappearance of plant material from litter bags in theS. fruticosa plot. Net primary production (aboveground and belowground) was calculated using the Smalley method. Standing biomass, litter, and primary production increased as soil salinity decreased. The annual average total aboveground plus belowground biomass was 872 g m−2 in theA. macrostachyum marsh, 1,198 g m−2 in theA. macrostachyum-S. fruticosa mixed marsh, and 3,766 g m−2 in theS. fruticosa biomass (aboveground plus belowground) was 226, 445, and 1,094 g m−2, respectively. Total aboveground plus below-ground net primary production was 240, 1,172, and 1,531 g m−2 yr−1. There was an exponential loss of weight during decomposition. Woody stems and roots, the most recalcitrant material, had 70% and 83% of the original material remaining after one year. Only 20–22% of leafy stem weight remained after one year. When results from the Mediterranean are compared to other salt marshes dominated by shrubbyChenopodiaceae in Mediterranean-type climates, a number of similarities emerge. There are similar zonation patterns, with elevation and maximum aboveground biomass and primary production occurring in the middle marsh. This is probably because of stress produced by waterlogging in the low marsh and by hypersalinity in the upper marsh. 相似文献
4.
Because tall cordgrass (Spartina foliosa) is needed for nesting by the endangered light-footed, clapper rail, managers of constructed salt marshes in southern California are proposing large-scale nitrogen fertilization to improve cordgrass growth. How this might affect an existing infestation of scale insects (Haliaspis spartina) and the degree of damage these insects cause to their cordgrass hosts was unknown. We explored the effects of timing and duration of fertilization onHaliaspis damage to cordgrass, as well as the timing ofHaliaspis dispersal, in a constructed marsh at Sweetwater Marsh National Wildlife Refuge in San Diego Bay, California. Fertilization did not result in increasedHaliaspis abundance. After a large dispersal pulse in late May,Haliaspis establishment in the long-term fertilized plots was greater than in the controls; however, this trend reversed in August, when many more stems in the control plots were infested with large numbers ofHaliaspis. Since adultHaliaspis cannot leave a feeding site, losses of individuals in the fertilized plots were apparently due to mortality, perhaps resulting from mechanical or chemical changes in the fertilized plants or increased predation. Late in the growing season, plots fertilized with 10 applications of urea over 20 wk had the lowest meanHaliaspis abundance. Plots fertilized only in March, April, June, or August did not differ from controls in meanHaliaspis abundance.Haliaspis was never abundant in the fertilized or control plots in the adjacent natural marsh. This study suggests that fertilization, of constructed salt marshes in San Diego Bay may proceed without concern that furtherHaliaspis outbreaks will be facilitated. 相似文献
5.
Nitrogen inputs restructure ecosystems and can interact with other agents of ecological change and potentially intensify them.
To examine the effects of nitrogen combined with those of elevation and competition, in 2005 we mapped vegetation and elevation
within experimental plots that have been fertilized since 1970 in Great Sippewissett salt marsh, Cape Cod, MA, USA and compared
the resulting effects on marsh vegetation. Decadal-scale chronic nutrient enrichment forced changes in cover and spatial distribution
of different species. With increasing enrichment, there was a shift in species cover primarily involving loss of Spartina alterniflora and an increase in Distichlis spicata. Percent cover of near monocultures increased with nitrogen fertilization, owing mainly to the proliferation of D. spicata. The experimental fertilization prompted a shift from the short form of S. alterniflora to taller forms, hence increasing above-ground biomass, where this species managed to remain. Chronic enrichment increased
upper and lower limits of the elevation range within which certain species occurred. The shift to increased cover of D. spicata was also associated with faster accretion of the marsh surface where this species was dominant, but not where S. alterniflora was dominant. Interactions among nutrient supply, elevation, and competition altered the direction of competitive success
among different species of marsh plants, and forced changes in the spatial distribution and composition of the salt marsh
plant communities. The results imply that there will be parallel changes in New England salt marshes owing to the widespread
eutrophication of coastal waters and the increasing sea level rise. Knowing the mechanisms structuring marsh vegetative cover,
and their role in modification of salt marsh accretion, may provide background with which to manage maintenance of affected
coastal wetlands. 相似文献
6.
Analyses of organic content, pollen, and the carbon-isotopic composition of a 3.5-m sediment core collected from a subsided
tidal marsh located in South San Francisco Bay, California, have provided a 500-yr record of sediment accretion and vegetation
change before, during, and after a rapid 1 m increase in sea level. Core chronology was established using14C dating of fossil plant material, the first appearance of pollen types produced by plants not native to California, and changes
in lead concentrations coincident with anthropogenic contamination. Prior to the mid 19th century, rates of sediment accretion
were between 1 and 4 mm yr−1; sediment accretion accelerated to an average of 22 mm yr−1 following the initiation of subsidence. Changes in tidal marsh vegetation also accompanied this depositional change. Vegetation
shifted from a high to low marsh assemblage, as indicated by a larger percentage of grass pollen, rhizomes ofSpartina foliosa, and a strong C4 signal. Between 1980 and 2001, Triangle marsh again developed high marsh vegetation, as indicated by higher percentages of
the Amaranthaceane pollen type, seed deposition, includingSalicornia spp., and more negative carbon isotopic ratios. 相似文献
7.
Sarah C. Crosby Angus Angermeyer Jennifer M. Adler Mark D. Bertness Linda A. Deegan Nathaniel Sibinga Heather M. Leslie 《Estuaries and Coasts》2017,40(1):213-223
To predict the impacts of climate change, a better understanding is needed of the foundation species that build and maintain biogenic ecosystems. Spartina alterniflora Loisel (smooth cordgrass) is the dominant salt marsh-building plant along the US Atlantic coast. It maintains salt marsh elevation relative to sea level by the accumulation of aboveground biomass, which promotes sediment deposition and belowground biomass, which accretes as peat. Peat accumulation is particularly important in elevation maintenance at high latitudes where sediment supply tends to be limited. Latitudinal variation in S. alterniflora growth was quantified in eight salt marshes from Massachusetts to South Carolina. The hypothesis that allocation to aboveground and belowground biomass is phenotypically plastic was tested with transplant experiments among a subset of salt marshes along this gradient. Reciprocal transplants revealed that northern S. alterniflora decreased allocation to belowground biomass when grown in the south. Some northern plants also died when moved south, suggesting that northern S. alterniflora may be stressed by future warming. Southern plants that were moved north showed phenotypic plasticity in biomass allocation, but no mortality. Belowground biomass also decomposed more quickly in southern marshes. Our results suggest that warming will lead northern S. alterniflora to decrease belowground allocation and that belowground biomass will decompose more quickly, thus decreasing peat accumulation. Gradual temperature increases may allow for adaptation and acclimation, but our results suggest that warming will lower the ability of salt marshes to withstand sea-level rise. 相似文献
8.
Vertical accretion of impounded marsh and adjacent natural marsh at four sites in southwestern Louisiana was estimated in 1994 by determining the depth of a stratum containing137Cs deposited in 1963. With relative marsh elevation, soil bulk density, organic matter content, and organic and mineral matter accumulation rates were used to describe soil formation. Three sites were impounded in 1956 and one site in 1951. Impounded marshes had lower marsh surface elevation than natural marshes because of hydrologic isolation from tidal sediment subsidies and substrate oxidation during forced drying. The elevation of natural marshes ranged from 12 cm to 42 cm higher than the elevation of the impounded marshes in 1963 and from 20 cm to 32 cm higher in 1994. Vertical accretion between 1963 and 1994 ranged from 9 cm to 28 cm in impounded marsh and from 15 cm to 21.5 cm in natural marsh. Only in impounded marsh that remained permanently flooded was accretion greater than in natural marsh. 相似文献
9.
The monthly variations of below- and aboveground biomass of Spartina alterniflora were documented for a south Louisiana salt marsh from March 2004 to March 2005, and in March 2006 and 2007. The annual production rate above- and belowground was 1821 and 11,676 g m?2, respectively (Smalley method), and the annual production rate per biomass belowground was 10.7 g dry weight?1, which are highs along the latitudinal distributions of the plant’s range. The average root + rhizome/shoot ratio (R&R/S) was 2.6:1, which is lower than the R&R/S ratios of 4 to 5.1 reported for Spartina sp. marshes in the northeastern US. The belowground biomass increased from July to September and fluctuated between October and November, after which it declined until February when the growing season began. The belowground biomass was dominated by rhizomes, which declined precipitously in spring and then rose to a seasonal high in the month before declining again as the late summer rise in inflorescence began. Over half of the root biomass in a 30-cm soil profile was in the upper 10 cm, and in the 10- to 20-cm profile for rhizomes. The maximum March biomass above- and belowground was four to five times that of the minimum biomass over the four sampling years. The net standing stock (NSS) of N and P in live biomass aboveground compared to that in the belowground biomass was about 1.7 times higher and equal, respectively, but the NSS of N and P for the live + dead biomass was about six times higher belowground. The average nitrogen/phosphorous molar ratios of 16:1 aboveground is in agreement with the often tested N limitation of biomass accumulation aboveground, whereas the 37:1 belowground ratio suggests that there is an influence of P on R&R foraging for P belowground. Some implications for management and restoration are, in part, that salt marshes should be evaluated and examined using information on the plant’s physiology and production both below- and aboveground. 相似文献
10.
This paper examines how perennial Aster tripolium and annual Salicornia procumbens salt marshes alter the biomass, density, taxon diversity, and community structure of benthic macrofauna, and also examines
the role of elevation, sediment grain size, plant cover, and marsh age. Core samples were collected on a fixed grid on an
intertidal flat in the Westerschelde estuary (51.4° N, 4.1° E) over 5 years (2004–2008) of salt marsh development. In unvegetated
areas, macrobenthic biomass, density, and taxon diversity were highest when elevation was highest, benthic diatoms were most
abundant, and sediment median grain size was smallest. In contrast, in salt marsh areas, macrobenthic biomass and taxon diversity
increased with median grain size, while the effects of elevation and diatom abundance on macrobenthic biomass, density, and
diversity were not significant. In fine sediments, macrofaunal community structure in the salt marsh was particularly affected;
common polychaetes such as Nereis diversicolor, Heteromastus filiformis, and Pygospio elegans had low abundance and oligochaetes had high abundance. Marsh age had a negative influence on the density of macrofauna, and
A. tripolium stands had lower macrofaunal densities than the younger S. procumbens stands. There were no significant effects of marsh age, plant cover, and vegetation type on macrobenthic biomass, taxon diversity,
and community structure. The results highlight that ecosystem engineering effects of salt marsh plants on macrofauna are conditional.
Organic enrichment of the sediment and mechanical hindering of macrofaunal activity by plant roots are proposed as plausible
mechanisms for the influence of the salt marsh plants on macrofauna. 相似文献
11.
Spatial distribution patterns ofScirpus validus were studied in tidal marshes of the lower Savannah River. The hypothesis that changes in spatial pattern forS. validus would accompany differences in environmental parameters was tested by sampling densities and biomass along environmental gradients of salinity and elevation. Coefficients of dispersion were calculated forS. validus and used to compare spatial patterns among freshwater, midly oligohaline, strongly oligohaline, and mesohaline tidal marshes. Results indicated significantly greater clumping ofS. validus in mesohaline marsh than in freshwater marsh. Only the mildly oligohaline site supported a random population ofS. validus, while the strongly oligohaline marsh supported a uniform spatial distribution. Spatial pattern and relative importance ofS. validus, as well as composition of co-occurring species, changed significantly with changing salinity. The relations between changes in relative importance ofS. validus and differences in soil organic matter and elevation were also significant. 相似文献
12.
Anammox bacteria are widespread in the marine environment, but studies of anammox in marshes and other wetlands are still
scarce. In this study, the role of anammox in nitrogen removal from marsh sediments was surveyed in four vegetation types
characteristic of New England marshes and in unvegetated tidal creeks. The sites spanned a salinity gradient from 0 to 20 psu.
The impact of nitrogen loading on the role of anammox in marsh sediments was studied in a marsh fertilization experiment and
in marshes with high nitrogen loading entering through ground water. In all locations, nitrogen removal through anammox was
low compared to denitrification, with anammox accounting for less than 3% of the total N2 production. The highest relative importance of anammox was found in the sediments of freshwater-dominated marshes, where
anammox approached 3%, whereas anammox was of lesser importance in saline marsh sediments. Increased nitrogen loading, in
the form of nitrate from natural or artificial sources, did not impact the relative importance of anammox, which remained
low in all the nitrogen enriched locations (<1%). 相似文献
13.
Joy B. Zedler 《Estuaries and Coasts》1983,6(4):346-355
Heavy rainfall in 1978 and 1980 caused flooding of southern California salt marshes. Examination of three marshes demonstrated a broad range of freshwater effects which correlated with the degree of change in soil salinity. At Tijuana Estuary (1980), a short-term reduction in the salinity of normally hypersaline soils was followed by a 40% increase in the August biomass of Spartina foliosa. At Los Penasquitos Lagoon (1978), a longer period of brackish water influence was followed by a 160% increase in August biomass of Salicornia virginica. At the San Diego River (1980), flood flows were augmented by major reservoir discharge. Continuous freshwater flow leached most of the marsh soil salts and caused replacement of halophytes by freshwater marsh species. The first two cases probably fell within the normal range of flooding events, even though the hydrology of both watersheds has been modified. The vegetation response was functional; productivity increased but there was no major change in species composition. As expected, vegetation rapidly returned to preflood conditions. However, the long-term freshwater flow in the Dan Diego River was unnatural. Floral composition changed as soils were leached of salts. Recovery following the return of saline soils has been slow because many native halophytes are not good colonizers. The system's resilience is limited, and modification of natural stream discharge can cause permanent changes in coastal wetlands. 相似文献
14.
The responses of Spartina alterniflora above- and belowground biomass to various combinations of N, P, and Fe were documented in a 1-year field experiment in a
Louisiana salt marsh. Five levels of N additions to 0.25 m2 plots resulted in 18% to 138% more live aboveground biomass compared to the control plots and higher stem densities, but
had no effect on the amount of live belowground biomass (roots and rhizomes; R&R). There was no change in the aboveground
biomass when P or Fe was added as part of a factorial experiment of +P, +N, and +Fe additions, but there was a 40% to 60%
decrease in the live belowground biomass, which reduced the average R&R:S ratio by 50%. The addition of various combinations
of nutrients had a significant affect on the belowground biomass indicating that the addition of P, not N, eased the need
for root foraging activity. The end-of-the-growing-season N:P molar ratios in the live above- and belowground tissues of the
control plot was 16.4 and 32.7, respectively. The relative size of the belowground standing stocks of N and P was higher than
in the aboveground live tissues, but shifted downwards to about half that in fertilized plots. We conclude that the aboveground
biomass was directly related to N availability, but not P, and that the accumulation of belowground biomass was not limited
by N. We suggest that the reduction in belowground biomass with increased P availability, and the lower absolute and relative
belowground standing stocks of P as plant tissue N:P ratios increased, is related to competition with soil microbes for P.
One implication for wetland management and restoration is that eutrophication may be detrimental to long-term salt marsh maintenance
and development, especially in organic-rich wetland soils. 相似文献
15.
Susan L. Williams Albert Carranza Jennifer Kunzelman Seema Datta Kathryn M. Kuivila 《Estuaries and Coasts》2009,32(1):146-157
Early indicators of salt marsh plant stress are needed to detect stress before it is manifested as changes in biomass and
coverage. We explored a variety of leaf-level spectral reflectance and fluorescence variables as indicators of stress in response
to the herbicide diuron. Diuron, a Photosystem II inhibitor, is heavily used in areas adjacent to estuaries, but its ecological
effects are just beginning to be recognized. In a greenhouse experiment, we exposed Spartina foliosa, the native cordgrass in California salt marshes, to two levels of diuron. After plant exposure to diuron for 28 days, all
spectral reflectance indices and virtually all fluorescence parameters indicated reduced pigment and photosynthetic function,
verified as reduced CO2 assimilation. Diuron exposure was not evident, however, in plant morphometry, indicating that reflectance and fluorescence
were effective indicators of sub-lethal diuron exposure. Several indices (spectral reflectance index ARI and fluorescence
parameters EQY, Fo, and maximum rETR) were sensitive to diuron concentration. In field trials, most of the indices as well
as biomass, % cover, and canopy height varied predictably and significantly across a pesticide gradient. In the field, ARI
and Fo regressed most significantly and strongly with pesticide levels. The responses of ARI and Fo in both the laboratory
and the field make these indices promising as sensitive, rapid, non-destructive indicators of responses of S. foliosa to herbicides in the field. These techniques are employed in remote sensing and could potentially provide a link between
landscapes of stressed vegetation and the causative stressor(s), which is crucial for effective regulation of pollution. 相似文献
16.
High nitrogen (N) loading rates received by coastal bays can have deleterious effects on aquatic ecosystems. Salt marshes
can intercept land-based N through seasonal plant uptake, denitrification, and burial. Salt marshes fringing Delaware’s Inland
Bays are characterized by different plant species occurring in close proximity. To evaluate N pool retention and loss for
the dominant plant species, we measured seasonal N concentration and pool size, N resorption efficiency, loss during decomposition,
and soil N. Seasonal variation in N pools and fluxes differed among species. Seasonal differences in the total N pools of
the herbaceous species were largely influenced by belowground fine root and dead macro-organic matter fluxes. N production
rate estimates ranged from 18 g N m−2 year−1 aboveground for the high marsh shrub to 40.8 g N m−2 year−1 above- and belowground for the high marsh rush illustrating the importance of incorporating species-specific dynamics into
ecosystem N budgets. 相似文献
17.
The purpose of this study was to determine how vertical accretion rates in marshes vary through the millennia. Peat cores
were collected in remnant and drained marshes in the Sacramento–San Joaquin Delta of California. Cubic smooth spline regression
models were used to construct age–depth models and accretion histories for three remnant marshes. Estimated vertical accretion
rates at these sites range from 0.03 to 0.49 cm year−1. The mean contribution of organic matter to soil volume at the remnant marsh sites is generally stable (4.73% to 6.94%),
whereas the mean contribution of inorganic matter to soil volume has greater temporal variability (1.40% to 7.92%). The hydrogeomorphic
position of each marsh largely determines the inorganic content of peat. Currently, the remnant marshes are keeping pace with
sea level rise, but this balance may shift for at least one of the sites under future sea level rise scenarios. 相似文献
18.
Shifting nutrient limitation and eutrophication effects in marsh vegetation across estuarine salinity gradients 总被引：1，自引：0，他引：1
Caitlin Mullan Crain 《Estuaries and Coasts》2007,30(1):26-34
In light of widespread coastal eutrophication, identifying which nutrients limit vegetation and the community consequences
when limitation is relaxed is critical to maintaining the health of estuarine marshes. Studies in temperate salt marshes have
generally identified nitrogen (N) as the primary limiting nutrient for marsh vegetation, but the limiting nutrient in low
salinity tidal marshes is unknown. I use a 3-yr nutrient addition experiment in mid elevation,Spartina patens dominated marshes that vary in salinity along two estuaries in southern Maine to examine variation in nutrient effects. Nutrient
limitation shifted across estuarine salinity gradients; salt and brackish marsh vegetation was N limited, while oligohaline
marsh vegetation was co-limited by N and phosphorus (P). Plant tissue analysis ofS. patens showed plants in the highest salinity marshes had the greatest percent N, despite N limitation, suggesting that N limitation
in salt marshes is partially driven by a high demand for N to aid in salinity tolerance. Fertilization had little effect on
species composition in monospecificS. patents stands of salt and brackish marshes, but N+P treatments in species-rich oligohaline marshes significantly altered community
composition, favoring dominance by high aboveground producing plants. Eutrophication by both N and P has the potential to
greatly reduce the characteristic high diversity of oligohaline marshes. Inputs of both nutrients in coastal watersheds must
be managed to protect the diversity and functioning of the full range of estuarine marshes. 相似文献
19.
Karen L. Hunter Dewayne A. Fox Lori M. Brown Kenneth W. Able 《Estuaries and Coasts》2006,29(3):487-498
Modification of brackish marshes by nonindigenousPhragmites australis has occurred across a broad geographical area in eastern North America. Among its effects on marsh processes,Phragmites may be increasingly unfavorable to marsh surface fishes as its invasion progresses within an estuary. We assessed the effect
of thePhragmites invasion on resident marsh surface fishes by examining the population response ofFundulus heteroclitus (mummichog, 5–48 mm TL) andF. luciae (spotfin killifish, 5–41 mm TL) to four distinct invasion stages in three estuaries of the U.S. mid Atlantic region (New
Jersey, Delaware, and Maryland). We documented precipitous declines in mean catch per unit effort ofF. heteroclitus in pit traps from natural marsh (51.6), through initial (33.8), early (12.3), and late invasion stages (2.4) across all sites.
A similar pattern was documented forF. luciae, with mean catch per unit effort in pit traps declining from natural marsh (48.9), through initial (39.1), early (9.3), and
late invasion stages (2.7). Population structure of both species also changed somewhat across invasion stages such that we
collected a narrower size range of individuals of both species from late invasion stages. Patterns suggest that as thePhragmites invasion progresses, there is a decline in habitat function for larval and juvenileF. heteroclitus and an increased risk of extirpation ofF. luciae from brackish marshes along the east coast of the U.S. 相似文献
20.
Aboveground production and tissue element composition of Spartina alterniflora were compared in bareier island marshes of different age off the Eastern Shore of Virginia. The marshes were also characterized by physical and chemical parameters of the substrate. The results suggest that sediment nutrient stock do not directly control the spatial pattern of element content or production of S. alterniflora between these marshes. Elevated salinity likely limits the nitrogen uptake capability of S. alterniflora in the high marsh, which, in turn, controls leaf tissue nitrogen content of plants within individual sites. Low substrate redox potential may control the spatial pattern of nitrogen uptake between the different-age marsh sites, loading to more favorable growing conditions at the low stations of the young marsh sites where values of tissue nitrogen and production are highest. Tissue phosphorus did not differ between, or within the marsh sites. The result of a fertilization experiment suggest that nitrogen, and not phosphorus, is the primary limiting nutrient in this sytem. This indicates that nutrient limitation and other stresses work in conjunction to control tissue element content and macrophyte production at these marsh sites. Spatial variability of factors that control leaf tissue nitrogen and production is likely related to topography and grain size of an individual marsh, which is a function of marsh age. Most studies in different-age marshes have compared transplanted marshes to older, natural marshes. This work is one of few studies comparing developing and mature natural, marshes on barrier islands. 相似文献