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1.
Several management techniques are effective in controlling Lepidium latifolium (perennial pepperweed) in rangelands and hay meadows; however, this invader’s rapid spread into sensitive aquatic habitats
throughout the western US calls for alternative control strategies. To evaluate control methods for use in tidal marshes of
San Francisco Estuary, we tested chemical, mechanical, and biological methods in field and greenhouse experiments. In a field
experiment in three brackish marshes spanning the estuary, application of the herbicide glyphosate to re-growth of L. latifolium following hand-removal reduced L. latifolium cover by an average of 80% after 2 years and led to a 60% increase in native vegetation cover. Glyphosate alone was less
effective at reducing L. latifolium cover (20% decrease) and increasing native cover (34% increase). Preliminary tests of a potential biological control, a native
parasitic plant, were not successful, thus plots intended for field trials were instead used to test the newly approved herbicide
imazapyr, which showed promise in controlling L. latifolium. An additional greenhouse experiment found large reductions in stem lengths with either glyphosate following clipping or
imazapyr with or without clipping, all significantly more so than glyphosate alone. We conclude that an integrated management
approach of applying glyphosate following mechanical removal can be effective at reducing L. latifolium cover and allowing recovery of native tidal marsh plants, providing a useful solution for controlling smaller, accessible
infestations of the invader. Our preliminary tests of imazapyr suggest that it may be very effective at controlling L. latifolium in tidal marshes, although further assessment of non-target effects and native plant recovery are needed to evaluate its
relative merit. 相似文献
2.
Large amounts of resources have gone into wetland mitigation in recent years; however, it is still unclear whether wetland
function is being replaced along with wetland area. Litter decomposition is linked to numerous wetland functions. In this
study, we measured plant litter decomposition potential over 12 months in 8 created and 8 reference wetlands located in the
Allegheny Mountains of West Virginia, USA. Broadleaf cattail ( Typha
latifolia L.) litter bags were placed in each wetland and collected at 3 month intervals. Linear decomposition rate constants and percent
mass remaining were similar between wetland types (created and reference) and among Cowardin classifications (palustrine:
unconsolidated bottom, aquatic bed, emergent, and scrub/shrub). Created wetland age was not correlated with decomposition
potential. Our study found that created wetlands had similar litter decomposition potential as reference wetlands indicating
that similar processes are likely acting upon litter decomposition within both natural and created wetlands. 相似文献
3.
Habitat restoration is an integral feature of wildlife conservation. However, funding and opportunities for habitat restoration are limited, and therefore, it is useful for targeted restoration to provide positive outcomes for non‐target species. Here, we investigate the possibility of habitat creation and management benefitting two threatened wetland specialists: the Green and Golden Bell Frog ( Litoria aurea) and the Large‐footed Myotis ( Myotis macropus). This study involved two components: (i) assessing co‐occurrence patterns of these species in a wetland complex created for the Green and Golden Bell Frog ( n = 9) using counts, and (ii) comparing foraging activity of Large‐footed Myotis in wetlands with low and high aquatic vegetation ( n = 6 and 7, respectively) using echolocation metres. Since Large‐footed Myotis possesses a unique foraging behaviour of trawling for aquatic prey, we hypothesised that foraging activity of this species would be higher in wetlands with low aquatic vegetation coverage. Additionally, we provide observations of its potential prey items. We identified one created wetland where both species were found in relatively high numbers, and this wetland had a permanent hydrology, was free of the introduced fish Gambusia ( Gambusia holbrooki) and had low aquatic vegetation coverage. We also found that Myotis feeding activity was significantly higher in low aquatic vegetation coverage wetlands ( x? = 65.72 ± 27.56 SE) compared to high ( x? = 0.33 ± 0.33 SE, P = 0.0000). Although this is a preliminary study, it seems likely that Green and Golden Bell Fro g and Large‐footed Myotis would gain mutual benefit from wetlands that are constructed to be permanent, that are Gambusia free, low in aquatic vegetation coverage, and are located in close to suitable roosting habitat for Large‐footed Myotis. We encourage adaptive aquatic vegetation removal for Green and Golden Bell frog as this may have benefits for Large‐footed Myotis. The evidence suggests that the former may be a suitable umbrella species for the latter. 相似文献
4.
Freshwater wetlands are a key component of the global carbon cycle. Wet–dry tropics wetlands function as wet-season carbon sinks and dry-season carbon sources with low aquatic metabolism controlled by predictably seasonal, yet magnitude-variable flow regimes and inundation patterns. However, these dynamics have not been adequately quantified in Australia’s relatively unmodified wet–dry tropics freshwater wetlands. A baseline understanding is required before analysis of land-use or climate change impacts on these aquatic ecosystems can occur. This study characterises geomorphology and sedimentology within a seasonally connected wet–dry tropics freshwater wetland system at Kings Plains, Queensland, Australia, and quantifies soil carbon stocks and wet- and dry-season aquatic metabolism. Soil carbon stocks derived from loss-on-ignition on samples to 1 m depth were 51.5?±?7.8 kg C m?2, higher than other wet–dry tropics wetlands globally, with potential for long-term retention at greater depths. Gross primary productivity of phytoplankton (GPP) and planktonic respiration (PR) measured through biological oxygen demand bottle experiments in the water column of sediment inundated under laboratory conditions show overall low GPP and PR in both wet- and dry-season samples (all wetland samples were heterotrophic with GPP/PR?<?1). Despite the short-term dominance of aquatic respiration processes leading to net release of carbon in the water column under these conditions, there is appreciable long-term storage of carbon in sediment in the Kings Plains wetlands. This demonstrates the importance of wet–dry-tropics wetland systems as hotspots of carbon sequestration, locally, regionally and globally, and consideration should be given to their conservation and management in this context. 相似文献
5.
Wetland restoration is used to compensate for historic and ongoing wetland losses. We compared bird community composition in 24 restored wetlands and 36 natural wetlands in the Parkland region of Alberta. Natural wetlands ranged in exposure to agricultural activity and were binned into three classes (low, medium, and high disturbance). Although the abundance and average species richness of birds were similar between restored and natural wetlands (analysis of variance: p > 0.22), the avian community composition differed significantly among wetland types (multiresponse permutation procedure [MRPP]: A = 0.05, p < 0.001). The avifauna using restored wetlands was distinct from the avifauna using natural wetlands spanning a range of disturbance levels ( A = 0.02–0.06; p ≤ 0.006). Notably, restored wetlands were surrounded by less shrub/forest cover and more open water than low‐disturbance, natural wetlands. The majority (58%) of species using the surveyed wetlands were not classified as wetland‐dependent. Interestingly, if only wetland‐dependent species are considered, the avifauna using restored wetlands is no longer distinctive (MRPP: A < 0.01, p = 0.187), although the abundance of wetland‐dependent birds was marginally higher in restored wetlands ( n = 24) than in low‐disturbance, natural wetlands ( n = 10; Tukey's honestly significant difference test: p = 0.041). Overall, restored wetlands had reduced beta diversity compared to natural wetlands, regardless of whether the avifauna were restricted to wetland‐dependent species or considered comprehensively. This draws into question the legitimacy of the assumption that restoration can fully offset continued losses of natural wetlands. 相似文献
6.
Lepidium latifolium is an aggressive plant species that is invading both wetlands and uplands across a wide range of salinities. This study examined
how salinity and moisture gradients influence the potential for invasion by L. latifolium. Three sites in the San Francisco Bay Delta with varying salinity and moisture levels were chosen as research sites. These
sites corresponded to a dry (18.32%) freshwater (3.88‰) site, a wet (40.53%) brackish (23.16‰) site, and a moderately wet
(38.33%) saline (32.33‰) site. Our results showed that inflorescence number and height were unaffected by salinity or soil
moisture. Seed production was significantly affected by salinity ( P = 0.0297) and moisture levels ( P = 0.0004). Seed production at the high salinity site was reduced by 29% from the freshwater site. Seed production at the
wettest site had an 87% reduction from the driest site. Seed viability was also reduced by both salinity ( P < 0.0001) and soil moisture ( P < 0.0001). Viability at the highest salinity site was reduced by 49% from freshwater sites and was reduced by 8% from the
wettest to driest sites. Mean seed dispersal distance was 0.23 m greater at the freshwater site, which was not statistically
significant ( P = 0.1815). The deleterious effects of salinity and moisture resulted in reduced L. latifolium densities in high salinity and moisture locations, but only at the highest salinity site. With increased seed production
and viability, drier freshwater sites experience greater propagule pressure, resulting in an increased invasion potential.
Therefore, variability along salinity and soil moisture gradients serve as useful metrics for prioritizing control and eradication
efforts of L. latifolium. 相似文献
7.
Wetlands in Uganda experience different forms of human pressure ranging from drainage for agriculture and industrial development
to over harvesting of wetland products. In order to develop sustainable management tools for wetland ecosystems in Uganda
and the Lake Victoria Region, water quality analyses were carried out in a rural undisturbed (pristine) wetland (Nabugabo
wetland in Masaka) and two urban wetlands that are experiencing human and urban development pressure (the Nakivubo wetland
in Kampala and Kirinya wetland in Jinja). The former wetland forms the main inflow into Lake Nabugabo while the other two
border the northern shore of Lake Victoria, Uganda. Nabugabo wetland buffers Lake Nabugabo against surface runoff from the
catchment, while Nakivubo and Kirinya wetlands provides a water treatment function for wastewater from Kampala City and Jinja
town respectively, in addition to buffering Lake Victoria against surface runoff. Water quality was assessed in all the wetland
sites, and in addition nutrient content and storage was investigated in the main plant species (papyrus, Phragmites, Miscanthidium and cocoyam) in Nakivubo and Kirinya wetlands. A pilot experiment was also carried out to assess the wastewater treatment
potential of both the papyrus vegetation and an important agricultural crop Colocasia esculenta (cocoyam). Low electrical conductivity, ammonium–nitrogen and ortho-phosphate concentrations were recorded at the inflow
into Nabugabo wetland (41.5 μS/cm; 0.91 mg/l and 0.42 mg/l respectively) compared to the Nakivubo and Kirinya wetlands (335 μS/cm;
31.68 mg/l and 2.83 mg/l and 502 μS/cm; 10 mg/l and 1.87 mg/l respectively). The papyrus vegetation had higher biomass in
Nakivubo and Kirinya wetlands (6.7 kg DW m −2; 7.2 kg DW m −2 respectively), followed by Phragmites (6.5, 6.7), cocoyams (6.4, 6.6) and Miscanthidium (4.0, 4.2). The papyrus vegetation also exhibited a higher wastewater treatment potential than the agricultural crop (cocoyam)
during the pilot experiment (maximum removal degree of ammonium–nitrogen being 95% and 67% for papyrus and yams). It was concluded
that urbanisation pressure reduces natural wetland functioning either through the discharge of wastewater effluent or the
degradation of natural wetland vegetation. It is recommended that wetland vegetation be restored to enhance wetland ecosystem
functioning and for wetlands that are not yet under agricultural pressure, efforts should be made to halt any future encroachment. 相似文献
8.
The development of bioindicators for wetlands, especially ephemerally hydrated depressional and isolated wetlands, can be problematic because of seasonal changes in hydrology and target indicator organism biology. To determine if benthic diatoms could be used as a multi-season biological indicator of wetland condition in isolated forested wetlands of Florida, USA, 11 wetlands were sampled twice during a 5-month period, once when dry, then again when hydrated. Sites sampled when dry had significantly higher diatom taxa richness at genus and species levels. Non-metric multidimensional scaling and multiple response permutation process analyses resulted in no obvious or significant wet/dry grouping of species or genus level abundance data. Five of seven diatom metrics of the Florida Wetland Condition Index (FWCI) for depressional forested wetlands were significantly linearly correlated ( p < 0.05), while only one of seven metrics (a dissolved oxygen indicator) had a significantly different mean in paired t-test analyses. The final FWCI was significantly correlated (Pearson's r = 0.85, p < 0.001) between wet and dry sites, and no difference was found in mean FWCI score between wet and dry sites ( t = −1.98, p = 0.076), suggesting that with additional research, benthic diatoms may be used to monitor and assess wetland condition regardless of season or site hydrologic conditions. 相似文献
9.
We assessed the extent and characteristics of geographically isolated wetlands (i.e., wetlands completely surrounded by upland)
in a series of watersheds in the urban northeast US. We applied a previously developed index of urbanization to a sample of
10 watersheds selected at random from a set of 30 watersheds whose boundaries lay within the borders of Rhode Island, USA.
The index of urbanization in our sample watersheds ranged over more than an order of magnitude and increased with increasing
amount of urban land use in the watersheds ( r
2 = 0.51, F = 8.22, P = 0.02). The density of isolated wetlands in the watersheds averaged 1.93 ± 0.21 wetlands km −2 and comprised 38.2 ± 1.77% of all wetlands. Isolated wetlands were smaller than those connected to other waters (non-isolated),
and accounted for 6.01–16.5% of the total wetland area in the watersheds. The area of isolated wetlands as a percent of all
wetland area significantly increased with increasing watershed urbanization ( r
2 = 0.62, F = 12.9, P = 0.007). Isolated wetlands were predominantly deciduous forested wetlands, and urban land cover in the 50 m buffer surrounding
isolated wetlands was significantly higher than in the 50 m surrounding non-isolated wetlands. The proportion of urban land
cover was greater in a 150 than a 50 m buffer surrounding the wetlands. Our results suggest that an increase in the index
of urbanization of 50 will result in 7% of the watershed’s wetlands being lost from federal protection. These findings indicate
that the process of urbanization, along with accompanying habitat fragmentation, may result in an increase in the vulnerability
of wetlands to loss and degradation and therefore has implications for the management and conservation of geographically isolated
wetlands. 相似文献
10.
We evaluated the side-effects of insecticides, herbicides and fungicides on adults of the egg parasitoid Telenomus remus (Nixon) under laboratory conditions. The protocol was adapted from that proposed by the Pesticides and Beneficial Organisms
Working Group of the International Organization for Biological Control (IOBC) for Trichogramma cacoeciae (Marchal). Chlorpyrifos, acephate, beta-cyfluthrin + imidacloprid, spinosad, and pyrethroids were harmful to the parasitoid,
whereas methoxyfenozide, diflubenzuron, and flufenoxuron had no effect. Of the herbicides examined, only glyphosate + imazethapyr
and 2,4- D amine were classified as harmless on the first and second days of parasitism; paraquat was the most harmful. Other herbicides
were harmless on the first day of parasitism, but caused various levels of reduction of T. remus parasitism on the second day. The fungicides were harmless or only slightly harmful. 相似文献
11.
Libellula angelina is an endangered dragonfly species that is native to East Asia. Recently, their population has become severely reduced through habitat loss. To protect L. angelina populations, we need to understand which factors determine their distribution and how their potential habitats will change in the future. In this study, the habitat preference of L. angelina was identified through field surveys, and the potential distribution of L. angelina and the impact of integrated climate–land cover changes were simulated using the MaxEnt model. Furthermore, the wetland loss scenario was applied to areas where the current trend in wetland loss will continue in the future. The field survey identified that L. angelina prefers small inland wetlands: permanent freshwater, ponds; permanent rivers, ponds; irrigated land; and estuarine waters. From the MaxEnt results, altitude was the variable with the greatest contribution and distance from wetlands was the most unique variable. MaxEnt described the geographic pattern of occurrences under the current climate well, with few areas requiring any further survey. In the future projection, the potential habitat area was increased by up to 48.8% and 30.6% in the 2050s and 2080s, respectively. However, potential habitat loss was expected if wetlands continue to decline as they have done in the last 20 years. The wetland loss scenario resulted in potential habitat losses of 1.9%–2.3% and 4.5%–6.1% in the 2050s and 2080s, respectively. Therefore, to protect L. angelina populations we must minimize the loss of current populations, secure wetlands and strengthen the connectivity between wetlands. 相似文献
12.
Habitat loss and degradation are leading causes of biodiversity declines, therefore assessing the capacity of created mitigation wetlands to replace habitat for wildlife has become a management priority. We used single season occupancy models to compare the occurrence of larvae of four species of pond‐breeding amphibians in wetlands created for mitigation, wetlands impacted by road construction, and unimpacted reference wetlands along a highway corridor in the Greater Yellowstone Ecosystem, United States. Created wetlands were shallow and had less aquatic vegetation and surface area than impacted and reference wetlands. Occupancy of barred tiger salamander ( Ambystoma mavortium) and boreal chorus frog ( Pseudacris maculata) larvae was similar across wetland types, whereas boreal toads ( Anaxyrus boreas) occurred more often in created wetlands than reference and impacted wetlands. However, the majority of created wetlands (>80%) dried partially or completely before amphibian metamorphosis occurred in both years of our study, resulting in heavy mortality of larvae and, we suspect, little to no recruitment. Columbia spotted frogs ( Rana luteiventris), which require emergent vegetation that is not common in newly created wetlands, occurred commonly in impacted and reference wetlands but were found in only one created wetland. Our results show that shallow created wetlands with little aquatic vegetation may be attractive breeding areas for some amphibians, but may result in high mortality and little recruitment if they fail to hold water for the entire larval period. 相似文献
13.
North American prairie pothole wetlands are known to be important carbon stores. As a result there is interest in using wetland
restoration and conservation programs to mitigate the effects of increasing greenhouse gas concentration in the atmosphere.
However, the same conditions which cause these systems to accumulate organic carbon also produce the conditions under which
methanogenesis can occur. As a result prairie pothole wetlands are potential hotspots for methane emissions. We examined change
in soil organic carbon density as well as emissions of methane and nitrous oxide in newly restored, long-term restored, and
reference wetlands across the Canadian prairies to determine the net GHG mitigation potential associated with wetland restoration.
Our results indicate that methane emissions from seasonal, semi-permanent, and permanent prairie pothole wetlands are quite
high while nitrous oxide emissions from these sites are fairly low. Increases in soil organic carbon between newly restored
and long-term restored wetlands supports the conclusion that restored wetlands sequester organic carbon. Assuming a sequestration
duration of 33 years and a return to historical SOC densities we estimate a mean annual sequestration rate for restored wetlands
of 2.7 Mg C ha −1year −1 or 9.9 Mg CO 2 eq. ha −1 year −1. Even after accounting for increased CH 4 emissions associated with restoration our research indicates that wetland restoration would sequester approximately 3.25 Mg
CO 2 eq. ha −1year −1. This research indicates that widescale restoration of seasonal, semi-permanent, and permanent wetlands in the Canadian prairies
could help mitigate GHG emissions in the near term until a more viable long-term solution to increasing atmospheric concentrations
of GHGs can be found. 相似文献
14.
Nitrogen in wastewater degrades aquifer and surface water quality. To protect water quality in the United States, nitrogen discharge standards are strict: typically 1.0 mg/L NH 4-N for discharge to surface water and 10 mg/L total nitrogen (TN) for discharge to soil. Passive constructed wetland treatment systems cannot meet the nitrification standards discussed in this paper, using loading rates commonly considered to be cost-effective based on economic conditions in North America. Although partial nitrification can be achieved with some vertically or intermittently loaded, subsurface flow (SSF) wetlands, complete nitrification cannot be achieved in these passive wetland treatment systems. Engineered wetlands (EWs) use mechanical power inputs via pumping of air or water to nitrify wastewater, and have evolved in large part to nitrify wastewater. The design energy requirements for these power inputs have yet to be described in the wetland treatment literature. Our paper investigates the energy and area requirements of three wetland technologies: aerated subsurface flow, tidal flow, and pulse-fed wetland treatment, compared to a mechanical activated-sludge treatment system. 相似文献
15.
It is hypothesized that perennial freshwater tidal wetland habitat exports inorganic and organic material needed to support
the estuarine food web and to create favorable habitat for aquatic organisms in San Francisco Estuary. It is also hypothesized
that most of the material flux in this river-dominated region is controlled by river flow. The production and export of material
by Liberty Island were measured and compared using discrete monthly and continuous (15 min) measurements of a suite of inorganic
and organic materials and flow between 2004 and 2005. Seasonal material flux was estimated from monthly discrete data for
inorganic nutrients, suspended solids and salts, organic carbon and nitrogen and phytoplankton and zooplankton group carbon
and chlorophyll a and pheophytin pigment. Estimates of material flux from monthly values were compared with measured daily material flux values
for chlorophyll a concentration, salt and suspended solids obtained from continuous measurements (15 min) using YSI water quality sondes. Phytoplankton
carbon produced within the wetland was estimated by in situ primary productivity. Most inorganic and organic materials were
exported from the wetland on an annual basis, but the magnitude and direction varied seasonally. Dissolved inorganic nutrients
such as nitrate, soluble phosphorus, total phosphorus and silica as well as total suspended solids were exported in the summer
while total and dissolved organic carbon were exported in the winter. Salts like chloride and bromide were exported in the
fall. Chlorophyll a and pheophytin were exported in the fall and associated with diatom and cyanobacteria carbon. Mesozooplankton carbon was
dominated by calanoid copepods and exported most of the year except summer. Continuous sampling revealed high hourly and daily
variation in chlorophyll a, salt and total suspended solids flux due to high frequency changes in concentration and tidal flow. In fact, tidal flow
rather than river discharge was responsible for 90% or more of the material flux of the wetland. These studies indicate that
freshwater tidal wetlands can be a source of inorganic and organic material but the export of material is highly variable
spatially and temporally, varies most closely with tidal flow and requires high frequency measurements of both tidal flow
and material concentration for accurate estimates. 相似文献
16.
Summary The effect of graded concentrations of four common ricefield herbicides (Arozin, Butachlor, Alachlor, 2,4- D) on diazotrophic growth, macromolecular contents, heterocyst frequency and tolerance potentials of Ca-alginate immobilized diazotrophic cyanobacterial isolates Nostoc punctiforme, N. calcicola, Anabaena variabilis, Gloeocapsasp., Aphanocapsa sp. and laboratory strain N. muscorum ISU ( Anabaena ATCC 27893) was studied and compared with free-living cultures. Cyanobacterial isolates showed progressive inhibition of growth with increasing dosage of herbicides in both free and immobilized states. There were significant differences in the relative toxicity of the four herbicides. Arozin proved to be more growth toxic in comparison to Alachlor, Butachlor and 2,4- D. Growth performance of the immobilized cyanobacterial isolates under herbicide stress showed a similar diazotrophic growth pattern to free cells with no difference in lethal and sub-lethal dosages. However, at lethal concentrations of herbicides, the immobilized cells exhibited prolonged survivability of 14–16 days as compared to their free-living counterparts (8–12 days). The decline in growth, macromolecular contents and heterocyst frequency was found to be similar in both the states in graded dosages of herbicides. Of the test organisms, A. variabilis showed maximum natural tolerance towards all the four herbicides tested. Evidently immobilization by Ca-alginate seems to provide protection to the diazotrophic cyanobacterial inoculants to a certain extent against the growth-toxic action of herbicides. 相似文献
17.
This paper summarizes the importance of climate on tropical wetlands. Regional hydrology and carbon dynamics in many of these
wetlands could shift with dramatic changes in these major carbon storages if the inter-tropical convergence zone (ITCZ) were
to change in its annual patterns. The importance of seasonal pulsing hydrology on many tropical wetlands, which can be caused
by watershed activities, orographic features, or monsoonal pulses from the ITCZ, is illustrated by both annual and 30-year
patterns of hydrology in the Okavango Delta in southern Africa. Current studies on carbon biogeochemistry in Central America
are attempting to determine the rates of carbon sequestration in tropical wetlands compared to temperate wetlands and the
effects of hydrologic conditions on methane generation in these wetlands. Using the same field and lab techniques, we estimated
that a humid tropical wetland in Costa Rica accumulated 255 g C m −2 year −1 in the past 42 years, 80% more than a similar temperate wetland in Ohio that accumulated 142 g C m −2 year −1 over the same period. Methane emissions averaged 1,080 mg-C m −2 day −1 in a seasonally pulsed wetland in western Costa Rica, a rate higher than methane emission rates measured over the same period
from humid tropic wetlands in eastern Costa Rica (120–278 mg-C m −2 day −1). Tropical wetlands are often tuned to seasonal pulses of water caused by the seasonal movement of the ITCZ and are the most
likely to be have higher fire frequency and changed methane emissions and carbon oxidation if the ITCZ were to change even
slightly. 相似文献
18.
Wetlands are large carbon pools and play important roles in global carbon cycles as natural carbon sinks. This study analyzes the variation of total soil carbon with depth in two temperate (Ohio) and three tropical (humid and dry) wetlands in Costa Rica and compares their total soil C pool to determine C accumulation in wetland soils. The temperate wetlands had significantly greater ( P < 0.01) C pools (17.6 kg C m −2) than did the wetlands located in tropical climates (9.7 kg C m −2) in the top 24 cm of soil. Carbon profiles showed a rapid decrease of concentrations with soil depth in the tropical sites, whereas in the temperate wetlands they tended to increase with depth, up to a maximum at 18–24 cm, after which they started decreasing. The two wetlands in Ohio had about ten times the mean total C concentration of adjacent upland soils ( e.g., 161 g C kg −1 were measured in a central Ohio isolated forested wetland, and 17 g C kg −1 in an adjacent upland site), and their soil C pools were significantly higher ( P < 0.01). Among the five wetland study sites, three main wetland types were identified – isolated forested, riverine flow-through, and slow-flow slough. In the top 24 cm of soil, isolated forested wetlands had the greatest pool (10.8 kg C m −2), significantly higher ( P < 0.05) than the other two types (7.9 kg C m −2 in the riverine flow-though wetlands and 8.0 kg C m −2 in a slowly flowing slough), indicating that the type of organic matter entering into the system and the type of wetland may be key factors in defining its soil C pool. A riverine flow-through wetland in Ohio showed a significantly higher C pool ( P < 0.05) in the permanently flooded location (18.5 kg C m −2) than in the edge location with fluctuating hydrology, where the soil is intermittently flooded (14.6 kg C m −2). 相似文献
19.
Mass loading and outflow phosphorus (P) relationships were investigated for four stormwater treatment area (STA) wetlands in south Florida. These systems, ranging in size from 350 to 2670 ha, were constructed by the South Florida Water Management District (SFWMD) for Everglades restoration, and approaches currently are being investigated for optimizing their design and management. We analyzed 2–7 years of P removal data from 10 independent STA process trains using system classifications based on dominant vegetation type, which was either emergent aquatic vegetation (EAV) or submerged aquatic vegetation (SAV), and prior land use, which was either recently farmed (RF) or historic wetland (HW). We found that a 1–2 year history of mass loading rates (MLR) at or below ∼1.3 g P/m 2/year in STA process trains provided a high likelihood of achieving outflow total P (TP) concentrations less than ∼30 μg/L. Statistical analyses revealed that P removal performance of SAV and EAV-HW systems was generally superior to that of EAV-RF systems. These performance differences were corroborated with data from seven other non-STA Florida-based treatment wetlands. Furthermore, in the subset of SAV and continuously flooded EAV-HW data with P MLRs at or below ∼2 g/m 2/year, outflow P concentrations were consistently between 10 and 20 μg/L, mass removal efficiencies were consistently above 85%, and the wetlands demonstrated a substantial resilience to small-to-moderate pulsed inflow P loads. Despite 16 occurrences in these full-scale STA data of annual flow-weighted mean outflow P concentrations between 10 and 20 μg/L, no significant MLR–P relationships were identified for targeting specific P concentrations in this range. 相似文献
20.
The flux of materials across ecosystem boundaries has significant effects on recipient systems. Because of edge effects, seasonal
wetlands in upland forest are good systems to explore these linkages. The purpose of this study was to examine flux of coarse
particulate organic matter as litter fall into seasonal wetlands in Minnesota, and the relationship of this flux to development
of mosquitoes ( Aedes aegypti). We hypothesized that litter flux into seasonal wetlands was dominated by upland plant litter that was lower quality and
slower to breakdown than wetland litter, and that development rate of mosquitoes reared on upland litter was less than those
reared on wetland litter. Of total litter fall into the wetlands, 71% originated in upland forest. Carbon to nitrogen ratios
differed between upland litter (mostly sugar maple ( Acer saccharum) and trembling aspen ( Populus tremuloides) leaves) and wetland litter (mostly black ash ( Fraxinus nirgra) leaves), averaging 63.9 and 47.7, respectively over two years. Breakdown rate of black ash leaves was faster than upland
leaves ( k (day −1) = 0.00329 and 0.00156, respectively), based on the average between wetland margins and centers. Development of mosquito
larvae fed black ash leaves was faster than larvae fed upland leaves. Our results demonstrate linkages between upland forests
and seasonal wetlands through litter fall. The abundance of upland litter in the wetlands may influence litter breakdown and
carbon assimilation by invertebrates. Wetlands receiving high amounts of upland versus wetland litter may be lower quality
habitats for invertebrates that depend on detrital pools for their development. 相似文献
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