Growth Of Phragmites Research Articles

Seasonal Phragmites australis classification in Long Point National Wildlife Area wetlands using a remotely piloted aircraft system and random forest machine learning

This study produced a high-accuracy remotely piloted aircraft system (RPAS) imagery classification method for identifying the invasive reed Phragmites australis ( Cav.) Trin. Ex Steud subsp. australis using random forest (RF) machine learning. RPAS imagery was collected in the spring and fall of 2019 using a fixed-wing RPAS equipped with a visible spectrum camera (eBee X, S.O.D.A. 3D; senseFly) in Long Point, Ontario, Canada. Imagery was used to produce separate early and late season classifications and a bi-temporal classification which used imagery from both dates. The overall accuracy achieved for each was 97%, 96%, and 91%, respectively. Digital surface models (DSMs) were the most important variable for identifying Phragmites in all classifications due to their greater height when compared to surrounding herbaceous vegetation. The bi-temporal classification, which utilized change in DSM value during the growing season, resulted in an estimated 47.8% new growth of Phragmites and appeared to capture sparse growth better than traditional classification differencing alone. This study highlights the promising use of high-resolution DSMs produced from RPAS imagery to classify invasive Phragmites and monitor within-year patch expansions.

Combination of biochar and AMF promotes phosphorus utilization by stimulating rhizosphere microbial co-occurrence networks and lipid metabolites of Phragmites

Agricultural biochar and arbuscular mycorrhizal fungi were used to promote the growth of Phragmites in the structural damaged and nutritional imbalanced littoral zone soils. Wheat straw biochar played a significant role in improving soil porosity and supplementing available phosphorus to 79.20 ± 3.20 mg/kg, compared with CK at 17.50 ± 0.88 mg/kg. The addition of Diversispora versiformis improved the plant net photosynthetic rate reaching up to 25.66 ± 0.65 μmol·m−2·s−1, which was 36.60 % higher than CK. The combination of biochar and fungi contributed to the whole plant dry weight biomass of 32.30 % and 234.00 % higher than the single biochar or AMF amendment groups, respectively. Meanwhile, the analysis of microbial co-occurrence networks showed the most relevant networks node species were mainly Talaromyces, Chaetomiacea and Gemmatimonadetes etc. Root lipid metabolite of Glycerophospholines further proved that phosphorus utilization was also enhanced endogenously in the rhizosphere soil. These results indicate that the combination of biochar and arbuscular mycorrhizal fungi play synergic role in enhancing phosphorus utilization endogenously and exogenously.

Monitoring an ungagged coastal marsh to analyze the salinity interaction of the marsh with Lake Erie.

Phragmites growth in a marsh watershed due to increased salinity has been a crucial issue across the world. The objective of this study was to investigate the salinity movement in the ungagged Mentor Marsh of Ohio, USA, where the salinity had increased due to a number of potential sources causing a decline in the native vegetation and leading to the increased invasive phragmites growth. In this study, we conducted a detailed bathymetric survey and established several monitoring stations to record hourly environmental data in Mentor Marsh. Since Mentor Marsh has a complex hydrologic characteristic, which interacts with Lake Erie due to the backwater effect, a hydrodynamic model, Environmental Fluid Dynamic Code (EFDC +), was developed to simulate the western Mentor Marsh wetland's salinity distribution. We evaluated the model performance by comparing water level, temperature, and salinity using statistical measures for a duration from December 2019 to March 2020. The model was calibrated using the measured time-series data of water temperatures, water levels, and water salinity from monitoring stations in the western basin. The model performance for salinity calibration (R2 = 0.82, RMSE = 0.041, and Pbias = - 1.05%) and validation (R2 = 0.84, RMSE = 0.066, and Pbias = - 2.05%) was good. In the next step, the calibrated model was utilized to investigate the salinity distributions under different inflow and lake level rise conditions. Our analysis suggested that during high-flow conditions, the advection of the saline water from Marsh Creek was vigorous in comparison to the diffusion of salinity mixing by tidal influence pushing the salinity towards Mentor Marsh and resulting in the lower salinity distribution within the model domain. Similarly, when the lake level rise occurred, the model predicted a significant decrease in the salinity of Mentor Marsh near Lake Erie. The average decrease of salinity from the salinity during the base run was - 45.8% near Lake Erie, - 29.7% at the junction of Mentor Marina and Mentor Marsh, - 21.2% in Mentor Marsh, and - 4.4% in Marsh Creek. The analysis further suggested that under high-flow conditions from Marsh Creek, the salinity moved towards Mentor Marsh, especially when lake level rise conditions were considered. This is mainly because the high water level of Lake Erie pushed March Creek towards Mentor Marsh. However, the salinity moved towards Lake Erie from Marsh Creek during low-flow conditions. Presumably, the phragmites growth in the western section seems to be due to the road salt used in winter for deicing purposes.

Positive interactions occur between Phragmites australis lineages across short term experimental nutrient regimes

Land use changes and greater nitrogen input into waterways have facilitated the spread of an invasive Eurasian lineage of Phragmites australis across North America. Its establishment has led to decreases in wetland plant diversity, and displacement of a native American Phragmites lineage considered to be a low-nutrient specialist. We hypothesized that carbon-rich amendments that reduced nitrogen availability would competitively favor the native lineage and nitrogen additions would favor the invasive lineage. In the greenhouse we assessed competitive interactions between native and invasive lineages following sawdust (low nitrogen) and urea (high nitrogen) additions by measuring total biomass, chlorophyll fluorescence and evaluating biomass allocation. Sawdust additions did not limit invasive Phragmites growth, while urea increased aboveground biomass of both lineages. Unexpectedly, mixtures of native and invasive Phragmites produced more above and belowground biomass than monocultures. Our findings suggest that at the level examined in this study, carbon additions would not be an effective management tool to control invasive Phragmites or restore the native North American lineage, but that facilitation between native and invasive lineages could promote their coexistence across a range of nutrient availability. Our results also provide limited evidence that displacement of native Phragmites could be due to other factors such as disturbance rather than competitive exclusion.

Phytoremediation for co-contaminated soils of cadmium and pyrene using Phragmites australis (common reed)

Soil contamination is currently the most severe problem as it poses a toxicological impact on human health and ecosystems. A greenhouse experiment was carried out to investigate the effect of 20 and 40 mg kg−1 of cadmium (Cd) or 50 and 100 mg kg−1 of pyrene (PYR) and the combined effect of Cd-PYR on the growth of Phragmites australis together with the uptake and accumulation of Cd as well as removal of PYR. Results demonstrated that the single or co- contaminants of Cd and PYR did not affect plant growth relative to control treatments, except low Cd and high PYR treatment, which showed a significant increase in 91% biomass compared to the control. However, under the joint effect of Cd-PYR, P. australis was unwilling to uptake and translocate Cd, and bioconcentration factor (BCF) and translocation factor (TrF) values were less than one. The removal rate of PYR in the soils and soil enzymes was negatively impacted at the elevated Cd level in the soil. Our study shows that P. australis may have the potential for phytostabilization but cannot be useful for phytoextraction.

The effects of biochar and dredged sediments on soil structure and fertility promote the growth, photosynthetic and rhizosphere microbial diversity of Phragmites communis (Cav.) Trin. ex Steud

The improvement of urban river revetment soil is conducive to promote the growth of pioneer plants which can accelerate the restoration of ecosystems. How to effectively amend soil structure and composition to provide a suitable soil rhizosphere for rapid plant expansion is essential to be solved in the study. Biochar and lake dredged sediments were used to amend an urban river bank soil, where compaction and lack of mineral nutrition hindered the growth of Phragmites. The study found that the addition of 50% mass of dredged sediments combined with 5% mass of straw biochar increased the plant height maximum growth rate, tiller number per unit area, and root biomass by 32.93%, 29.62%, and 41.39%, respectively. The reason for these positive effects on plant growth mainly involved the improvement of rhizosphere soil properties. Addition of biochar increased porosity and available phosphorus content while dredged sediments increased soil organic carbon, thereby increasing the underground unit total phosphorus content of Phragmites by 18.18%. An increase of the Alpha diversity index of rhizosphere microorganisms (8.18%) and the decrease in infection rate of arbuscular mycorrhizal fungi (23.61%) also proved that the rapid expansion of Phragmites was improved owing to changes of the soil physicochemical properties. The combination of biochar and dredged sediments realized synergistic improvement of soil physical structure and increase of nutrient content, which helped promote the growth and expansion of the underground part of Phragmites. This cost-effective method can be feasible used for improvement of urban river revetment ecosystem.

Can nutrient enrichment influence the invasion of Phragmites australis?

Plant invasion and nutrient enrichment because of anthropogenic landscape modifications seriously threaten native plant community diversity in aquatic and wetland ecosystems. It is poorly understood, however, whether these two disturbances interact with the functional identity of recipient native plants to drive community change. We performed combined studies in the fields and greenhouse to examine whether nutrient enrichment may trigger the invasion of Phragmites australis in wetlands through competitive advantage over native Melaleuca ericifolia. Chemical characterizations of rhizosphere water were distinguished in two different nutrient enriched wetlands associated with and without Phragmites over the seasons. Significant changes in rhizosphere water were observed in invaded area compared to uninvaded area at both sites. High nitrogen (NO3−), phosphorous (PO43−), dissolved organic carbon, phenolics contents, with low pH were found in invaded areas compared to uninvaded areas. Total biomass of Phragmites was positively regressed with rhizosphere water nitrogen (NO3−) and phosphorous (PO43−) content. Nutrient addition significantly enhanced the growth and competitive ability of Phragmites over Melaleuca. In contrast, Melaleuca was significantly less competitive than Phragmites. There was a significantly positive correlation between the growth of Phragmites grown alone and its competitive ability. The findings in greenhouse studies coupled with characteristics of Phragmites and its' rhizosphere chemistry in the nutrient enriched fields suggest that nutrient enrichment may enhance Phragmites invasion through correspondingly increasing growth and maintaining inherent competitive advantages of Phragmites. Nutrient management could limit the vigorous growth of Phragmites in wetlands and thereby reduce invasion through competitive advantages over natives, which might have important management implications for wetland managers.

Functional Role of Bacteria from Invasive Phragmites australis in Promotion of Host Growth.

We hypothesize that bacterial endophytes may enhance the competitiveness and invasiveness of Phragmites australis. To evaluate this hypothesis, endophytic bacteria were isolated from P. australis. The majority of the shoot meristem isolates represent species from phyla Firmicutes, Proteobacteria, and Actinobacteria. We chose one species from each phylum to characterize further and to conduct growth promotion experiments in Phragmites. Bacteria tested include Bacillus amyloliquefaciens A9a, Achromobacter spanius B1, and Microbacterium oxydans B2. Isolates were characterized for known growth promotional traits, including indole acetic acid (IAA) production, secretion of hydrolytic enzymes, phosphate solubilization, and antibiosis activity. Potentially defensive antimicrobial lipopeptides were assayed for through application of co-culturing experiments and mass spectrometer analysis. B. amyloliquefaciens A9a and M. oxydans B2 produced IAA. B. amyloliquefaciens A9a secreted antifungal lipopeptides. Capability to promote growth of P. australis under low nitrogen conditions was evaluated in greenhouse experiments. All three isolates were found to increase the growth of P. australis under low soil nitrogen conditions and showed increased absorption of isotopic nitrogen into plants. This suggests that the Phragmites microbes we evaluated most likely promote growth of Phragmites by enhanced scavenging of nitrogenous compounds from the rhizosphere and transfer to host roots. Collectively, our results support the hypothesis that endophytic bacteria play a role in enhancing growth of P. australis in natural populations. Gaining a better understanding of the precise contributions and mechanisms of endophytes in enabling P. australis to develop high densities rapidly could lead to new symbiosis-based strategies for management and control of the host.

Diversity of fungal endophytes in non-native Phragmites australis in the Great Lakes

Plant–microbial interactions may play a key role in plant invasions. One common microbial interaction takes place between plants and fungal endophytes when fungi asymptomatically colonize host plant tissues. The objectives of this study were to isolate and sequence fungal endophytes colonizing non-native Phragmites australis in the Great Lakes region to evaluate variation in endophyte community composition among three host tissue types and three geographical regions. We collected entire ramets from multiple clones and populations, surface sterilized plant tissues, and plated replicate tissue samples from leaves, stems, and rhizomes on corn meal agar plates to culture and isolate fungal endophytes. Isolates were then subjected to Sanger sequencing of the ITS region of the nuclear ribosomal DNA. Sequences were compared to fungal databases to define operational taxonomic units (OTUs) that were analyzed statistically for community composition. In total, we obtained 173 endophyte isolates corresponding to 55 OTUs, 39 of which were isolated only a single time. The most common OTU corresponded most closely to Sarocladium strictum and comprised 25 % of all fungal isolates. More OTUs were found in stem tissues, but endophyte diversity was greatest in rhizome tissues. PERMANOVA analyses indicated significant differences in endophyte communities among tissue types, geographical regions, and the interaction between those factors, but no differences among individual ramets were detected. The functional role of the isolated endophytes is not yet known, but one genus isolated here (Stagonospora) has been reported to enhance Phragmites growth. Understanding the diversity and functions of Phragmites endophytes may provide targets for control measures based on disrupting host plant/endophyte interactions.

Effect of dikes on the distribution and characteristics of Phragmites australis in temperate intertidal wetlands located in the South Sea of Korea

We investigated the Korean Phragmites australis (haplotype P) distribution patterns and their association with environmental factors in estuaries with (Goseong) and without (Guman) a dike. The intertidal wetland of the Guman River Estuary has a flooding duration of 25% to 68% (average 40%), a range common to Phragmites habitats around the world. Porewater salinity in the Phragmites habitat of the Guman varied with the tides. Salinity of the overlying water influenced the salinity of pore-water only if flooding was above a certain height (overlying water depth of about 30 cm). High salinity was frequently observed in overlying water and pore-water of the Guman but the Phragmites may be able to survive with periodic exposure to freshwater, which relieves high salinity stresses. However, Phragmites experienced limited growth in some regions where flooding frequency was high but freshwater influence was low. Continuous measurement (two weeks) of pore-water salinity suggests that the salinity near the Phragmites rhizosphere is determined by the balance between the tidal and freshwater influences. Phragmites in the Goseong River Estuary was found at elevations about 100 cm lower than in the Guman and Phragmites growth was larger in the Goseong than in the Guman. We hypothesized that lower flooding duration and pore-water salinity, resulting from dike construction, allowed Phragmites to expand into lower elevation areas in the Goseong. The current study demonstrates the effects of coastal developments involving salinity structure and flooding duration changes on Phragmites distribution.

Performance evaluation of the electrolysis process for waste sludge stabilization in decentralization practices

This study was undertaken to evaluate the potential use of electrolysis process for waste sludge stabilization in decentralization practices by focusing on the operating parameters such as sludge composition, detention time, and electric voltage. The laboratory batch scale results show that the sludge extracted from a packed bed biofilm reactor can reach the minimum concentration of 659 mg/L volatile suspended solids (VSS) merely within 5 h detention time at an applied voltage of 2 V, whereas the most identical level is obtained from activated sludge by 7 h with 3.6 V. The soluble COD in the supernatant phase of the former process would be increased to 297 mg/L by means of 27% VSS reduction. The economical pre-estimation indicates that electrolysis is more sustainable if stand as a preconditioning stage of biological digestion by 70% capital and operating cost reduction. This configuration can also cause occupying 54% lesser footprint area of aerobic digestion with total average reduction of 56% VSS within 77 h. The biological assay on digested product was also determined with reference to the growth of Phragmites sp. plant. This study recommends the electrolysis-pretreated conditioning waste sludge followed by aerobic digestion incorporating with attached growth biological systems as a valuable process in decentralization.

Response of wetland vegetation to the post-1986 decrease in Lake St. Clair water levels: Seed-bank emergence and beginnings of the Phragmites australis invasion

Water-level fluctuations are critical for maintaining the diversity and resultant habitat value of wetland plant communities in the Laurentian Great Lakes. However, activation of the seed bank can also provide an opportunity for invasive species to displace native species, as occurred when common reed, Phragmites australis, expanded across many wetlands after lake levels receded following highs in 1997. Timing of the invasion process is not clear, however, as Phragmites propagules had to be present to exploit the exposed soils. A data set from Dickinson Island on the St. Clair River delta collected in 1988–1991, 1996 during a previous lake-level decline was analyzed to document prior Phragmites growth, as well as overall seed-bank response. Above-ground biomass was determined for all plants each year in randomly placed quadrats in a 5-ha area exposed when lake levels decreased by 0.65m from 1986 to 1988. A total of 38 taxa were identified in 1988, but the number decreased, along with biomass of many species, as canopy-dominating Typha angustifolia and Phragmites increased in later years. Although Phragmites did not expand greatly until after the decline from the 1997 high, it likely inoculated the area with viable seed during the previous low. Because post-1997 lake levels were lower than those post-1986, they exposed a greater area for Phragmites colonization from seed; lake levels also remained low for a longer time. Differences in bathymetry below the 1986 and 1997 lake-level elevations likely played a role in greater post-1997 spatial expansion of Phragmites at other sites in the Great Lakes also. The next high lake level will likely be required to displace Phragmites, but the effect will be temporary.

莫莫格湿地芦苇对水盐变化的生理生态响应

Understanding the eco-physiological response characteristics of Phragmites australis to water-salt condition is the key of determining the threshold of wetland ecological water requirement,in order to supply a feasible method for calculating the wetland ecological water requirement and scientific base for wetland restoration.By field investigation of Phragmites australis in Momoge wetland,we analyzed the relationship between eco-physiological characteristics of Phragmites australis and water-salt gradient with method of redundancy analysis(RDA) by using CANOCO software in Version 4.5.The results showed that the combination of three environmental factors including water depth,Na+ and HCO-3,explained 54.7% of the variation of eco-physiological responses of Phragmites australis,suggesting that the three environmental factors led to great changes in eco-physiological responses of Phragmites australis.Water depth was the key environmental factor influencing the growth of Phragmites australis.There was a significant positive correlationship between water depth and the eco-physiological characteristics including plant height,biomass,chlorophyll content,maximum photosynthesis efficient(FV/FM) and maximum photosynthesis performance index(PIABS).There was no significant correlationship between Na+/HCO-3 and the characteristics of Phragmites australis.The results suggested that it is the key point in the process of wetland restoration in mild or moderate saline-alkaline wetland to consider the influence of water depth on the growth of Phragmites australis,and secondly consider the effect of Na+/HCO-3,and determining the ecological water depth and fulfilling the ecological water requirement.

Can Plant Competition and Diversity Reduce the Growth and Survival of Exotic Phragmites australis Invading a Tidal Marsh?

The rapid proliferation of Phragmites australis in North America has challenged resource managers to curb its expansion and reduce the loss of functional tidal marsh. We investigated whether native plant competition could reduce the ability of Phragmites to invade a tidal marsh, and if plant diversity (species richness, evenness, and composition) altered the competitive outcome. Immature Phragmites shoots and four native halophytes were transplanted to small but dense field plots (~1,200 shoots m−2) comprising three community structure types (Phragmites alone, Phragmites + 1 native species, and Phragmites + 4 native species). Interspecific competition significantly reduced Phragmites aboveground biomass, shoot length production, density, and survival by approximately 60%. Additionally, plots planted with greater native diversity contained Phragmites with the lowest growth and survival, potentially indicating diversity-enhanced resource competition. Competition consistently reduced the growth of Phragmites even under favorable conditions: lack of strong tidal flooding stresses as well as elevated nutrient pools.

Phytotoxicity of chlorinated benzenes to Typha angustifolia and Phragmites communis

Healthy growth of plants is a prerequisite for successful application of phytoremediation technologies. Typha angustifolia and Phragmites communis are common wetland plants and have shown potential for phytoremediation of hexachlorobenzene (HCB). However, the lack of phytotoxicity data impedes their application in field sites. This study investigated the phytotoxicity of HCB, and its two metabolites: 1,3,5-trichlorobenzene (1,3,5-TCB) and 1,4-dichlorobenzene (1,4-DCB) to Typha and the phytotoxicity of 1,3,5-TCB to Phragmites. The phytotoxicity of 1,3,5-TCB is species-dependent, with Typha demonstrating significantly higher tolerance than Phragmites. The concentration of 1,3,5-TCB causing zero growth of Phragmites was determined to be 1575 mg TCB/kg dry sediment. The concentration has to be doubled to completely inhibit the growth of Typha. Adverse effects of chlorinated benzenes in sediments on Typha increased with decreasing chlorine atoms. The concentrations causing zero growth of Typha are 5765 mg HCB/kg dry soil, 3157 mg 1,3,5-TCB/kg dry soil, and 1325 mg 1,4-DCB/kg dry soil. The higher toxicity of 1,4-DCB than 1,3,5-TCB and HCB in sediment was ascribed to its higher availability and easiness to be taken up by plants. The conclusion was supported by both growth rate calculations and plant height measurements. (c) 2008 Wiley Periodicals, Inc. Environ Toxicol, 2009.

Response of Phragmites to environmental parameters associated with treatments

This multi-year study evaluated the response of invasive Phragmites australis to changes in pore water geochemistry associated with tidal enhancement, alone or in combination with other prescribed management regimes used by the US Fish and Wildlife Service. A pilot study was conducted prior to the treatment experiment that showed a negative correlation between the growth of Phragmites and cation concentrations in a transitional vegetation zone. In the targeted 535- acre brackish-water impoundment (East Pool) where Phragmites dominated, the soil water chemistry was changed by introducing tidal salt

Experimental Phragmites control through enhanced sediment sulfur cycling

Additions of sulfate or sulfur (S o), with and without carbon amendments, were made to large cores vegetated with Phragmites collected from a brackish N.J. marsh. Impairment of Phragmites growth from various carbon and sulfur additions was monitored over 1 yr. Initial increase in porewater sulfide was inhibited by sediment sulfide sequestration capacity concentrated in more inorganic surface layers which required millimolar sulfide inputs before concentrations rose to biologically significant levels. Even with sulfate concentrations sufficient to support sulfate reduction, sorption and reoxidation kept sulfide levels <250 μM in surface layers. Either dextrose or sulfate additions resulted in small increases in porewater sulfide levels (<120 μM), primarily at depth (22.5 cm). Carbon plus sulfate additions resulted in large, sustained enhancement of dissolved sulfide (∼1500 μM) throughout the sediment column. Elevated sulfide levels alone or in concert with porewater salinities greater than 20 ppt, did not kill emergent Phragmites although evapotranspiration and regrowth, indicated ‘stress’. Sulfide levels were limited by sulfate and/or biologically available carbon. Determination of adequate sulfate dose also requires an initial measurement of the sulfide sequestration capacity of the sediments to allow adequate sulfate availability to support porewater sulfide levels sufficient to cause plant stress.

Phragmites australis expansion in Delaware Bay salt marshes

Phragmites australis, widespread in tidal marshes of the eastern coast of North America, spreads primarily by the growth of surface runners and underground rhizomes. The distribution of Phragmites, based on maps from aerial photography on Estuary Enhancement Program (EEP) sites of Public Service Enterprise Group (PSEG), was investigated before and after marsh restoration. Initial establishment of Phragmites occurred around 1950 near riverfronts or creek mouths and proceeded upstream. Phragmites expanded to creek bank berms, the tidal/upland edge as well as central marsh plains. Phragmites growth may be characterized into periods of (1) initial establishment, (2) unrestricted expansion, (3) restricted expansion (restricted by open water-creeks, upland borders, or other colonies of Phragmites), and (4) monospecific marsh plains of Phragmites. Intrinsic rate of increase and increase in percent coverage measures for Phragmites growth on the EEP sites are comparable to those of other studies, although some EEP site values are much higher. Describing Phragmites expansion in these terms does not account for the actual distribution and pattern of Phragmites colonies as constrained by tidal creeks and upland boundaries. Therefore, an approach to estimate the actual rate of linear (or “radial”) expansion of Phragmites colonies was developed using standard GIS functions by having colonies represented by an equivalent ellipse having the same area and “diameter” as the colony or polygon. This perimeter expansion rate (PER) appears to estimate the actual growth rate of an advancing front of Phragmites as observed in the field from site maps of Phragmites coverage. This approach, as well as a GIS simulation of Phragmites colony growth, can be used to estimate the density of growing Phragmites rhizome buds (potential for regrowth) following management efforts.

Monitoring the change of Phragmites distribution using satellite data

Walpole Island in southern Ontario has extensive cattail marsh. In recent years, however, an invasive species (Phragmites) is fast spreading in this area and is affecting the ecosystems and wildlife habitat. In this research, a series of optical satellite images, including Landsat thematic mapper (TM), Satellite pour l'Observation de la Terre (SPOT), and Indian Remote Sensing Satellite (IRS), were used to monitor the recent growth of Phragmites and locate the areas subject to the highest rate of loss of cattail. The post-classification comparison method was applied for change detection. The change-detection accuracy is highly dependent on the accuracy of the classification of the images involved in the process. To improve the results, classification was performed on the combination of spectral bands and textural features. Employing a texture analysis technique, a RADARSAT image was used to resolve the effect of cloud cover on the classification result of the Landsat image. Maps showing the change of Phragmites distribution were created for different years. The change maps showed areas experiencing the highest rate of change in the study area. This work shows that remote sensing can provide important information for wetland vegetation changes.

Hydrologic and chemical control of Phragmites growth in tidal marshes of SW Connecticut, USA

We compared hydrology and porewater chemistry along transects in 3 tidal marshes vegetated by Spartina alterniflora and by the invasive species Phragmites australis. Relative to the Phragmites zone, the S. alterniflora zone occurred at lower tidal elevations in all 3 marshes and was characterized by greater depth of flooding and shorter periods of water-table drawdown below the soil surface. Penetration by Phragmites into the S. alterniflora zone appeared to be limited by exten- sive soil saturation at the leading edge of Phragmites growth. This mixed-species zone occurred at the intersection of the low-tide groundwater table with the soil surface and was characterized by sig- nificantly higher concentrations of porewater sulfide (739 ± 63 µM) relative to the monospecific Phragmites zone (335 ± 63 µM). Dissolved ammonium and phosphate concentrations were also sig- nificantly lower in the Phragmites zone relative to S. alterniflora and mixed-species zones of vegeta- tion. Discriminant analysis of the measured hydrologic and chemical variables identified depth of flooding, flooding frequency and duration, and sulfide concentration, as the most significant vari- ables distinguishing Phragmites stands along the estuarine salinity gradient. Together, these results indicate a greater flooding tolerance by Phragmites in marshes where porewater sulfide and salinity are lower. From a hydrologic and chemical perspective, opportunities for Phragmites invasion and expansion should be greater in oligohaline and mesohaline tidal marshes relative to polyhaline habitats. To control the growth of Phragmites in tidal marshes of management concern, both the feasibility and need for methods that increase flooding depth, frequency, salinity and/or sulfide concentrations should be considered.