The invasion of Phragmites australis (common reed) into Spartina alterniflora (cordgrass) salt marshes along the northeastern coast of the United States has recently been of concern. Numerous studies have evaluated the effects of P. australis on marsh nekton and infauna, but its effects on the distribution of stem-dwelling epifaunal communities has not been investigated previously. Standing living and dead plants of both species were collected periodically during three growing seasons (2000–2002) from brackish and salt marshes in New Jersey and Long Island, and the abundance, composition, and diversity of epifaunal communities associated with the stems of the two plant species were compared. Spartina alterniflora, particularly dead S. alterniflora, supported a higher density of animals than P. australis in 12 of the 19 samplings. When communities on standing live and dead stem were considered separately, higher abundances were found on dead S. alterniflora stems. Nematodes and harpacticoid copepods were the dominant taxa, with mites, annelids, and insects comprising minor components. Taxon-specific abundances tended to be higher on S. alterniflora stems, and community diversity was generally greater on this species as well. Between-site and between-year variation was observed. Relative to data recorded from sub-tropical salt marshes, the epifaunal communities in our samples were less abundant and diverse. Differences in the epiphytic communities associated with the two species, along with differences in stem structure, may explain why S. alterniflora stems support more epifaunal animals than P. australis stems overall.

Rhodamine-WT and LiCl were compared for their suitability as hydraulic tracers in wetlands. Using outdoor mesocosms, we found lithium to be more conservative than rhodamine-WT when initial concentrations were 4.9 to 64 μg/L for rhodamine-WT and 28–516 μg/L for Li (1:6 to 1:8 (wt/wt) ratio of rhodamine-WT to Li ). At higher initial concentrations (i.e., 100 μg/L for rhodamine-WT and 1000 μg/L for Li ), both tracers returned more than 95% of the injected amount in submerged aquatic vegetation-dominated mesocosms; rhodamine-WT was returned at only 74–75% in cattail-dominated mesocosms. Batch studies using different sediment substrates exposed to direct sunlight and shade indicated that Li was less affected by adsorption and microbial processes than was rhodamine-WT at low initial tracer concentrations of each (4.9 and 19.4 μg/L for rhodamine-WT and 28 and 106 μg/L for Li ). Both rhodamine-WT and Li desorb back to the water column in small amounts. The extent of adsorption losses by rhodamine-WT depended on the organic matter content of the sediment and the extent of photolysis. Even though rhodamine-WT was not as stable as LiCl at initial concentrations less than 60 μg/L, the reduction in the recoveries did not affect the accuracy of key hydraulic parameters (hydraulic retention time, dispersion, tanks-in-series, and wetland dispersion numbers) derived from the method of moments analysis as long as a discernible concentration-time response still existed. This is because the tracer losses were approximately zero-order and irreversible.

Floodplain pond distribution, density, and diversity were investigated along the active river corridor of the Tagliamento River in northeastern Italy, the last major semi-natural river in Central Europe. Along the corridor, ponds peaked in bar- and island-braided floodplains but were absent in constrained sections. Within the main study area, a 1.0-km² large braided floodplain, the number of ponds containing water ranged between 18 and 39 depending on the water level in the main channel. Thermal properties and water-level fluctuations were the most important variables determining pond characteristics and heterogeneity. Results from a PCA on environmental variables distinguished four groups of ponds distributed along a hydrologic and thermal gradient. Parafluvial ponds are short-lived, discrete, aquatic “islands” within the floodplain matrix. They are expected to contribute disproportionately to aquatic biodiversity; however, they are very sensitive landscape elements that disappear as a consequence of river regulation, wood removal, and flow control.

Managed impoundments, a form of structural marsh management, have been used to enhance plant production in the rapidly-eroding marshes of coastal Louisiana, USA, yet few studies have quantified their effects by measuring plant production before and after impoundment construction. We tested the effects of structural marsh management on the annual aboveground production and plant stand structure (stem density and stem height) of Spartina patens and Schoenoplectus americanus by collecting measurements before and after the construction of two shallow impoundments. We manipulated the water level in each impoundment by adjusting a single flap-gated culvert fitted with a variable crest weir. Because nutria herbivory also seemed to have a strong influence on plant production in these marshes, we tested the effects of nutria herbivory on the annual aboveground production and plant stand structure of both plant species by collecting data from fenced (ungrazed) and unfenced (grazed) plots located in both managed and unmanaged areas. There were no significant differences in Spartina annual production, stem density, and stem height between managed and unmanaged areas, and Schoenoplectus annual production, stem density, and stem height were greater in unmanaged marsh, indicating that the management method used in this study was not effective in promoting plant production in the rapidly-eroding, brackish, deltaic marshes of coastal Louisiana. Nutria herbivory dramatically reduced the annual aboveground production, stem density, and stem height of Schoenoplectus, a preferred forage species, and thus altered the structure of the mixed species stand. Herbivory had no significant effect on the annual aboveground production and stem density of Spartina. In the absence of herbivory, the stem height of Spartina increased significantly and coincided with significant increases in the stem density and height of Schoenoplectus. The changes in plant stand structure caused by nutria herbivory may facilitate marsh erosion and ultimately contribute to wetland loss.

Wetland mitigation banking is the practice of creating, restoring, enhancing, or preserving large, off-site wetlands to compensate for authorized impacts to natural wetlands. By 2002, there were 219 active mitigation banks in the United States, encompassing 50,000 hectares in 29 states. This study is the first systematic analysis of the ecological quality of these ecosystems; the objective is to determine if mitigation banks are successfully supporting native wetland vegetation and if success differs by mitigation method (created, restored, or enhanced), geomorphic class, age, or area. I obtained monitoring reports from 45 randomly selected mitigation bank wetlands in 21 states to evaluate three measures of ecological status: the prevalence of wetland vegetation, the pervasiveness of non-native species, and plant species richness. Sites range from less than one ha to over 560 ha and include 17 created wetlands, 19 restored wetlands, and 9 enhanced wetlands. Prevalence Index scores (PI; 1.0 for obligate wetland vegetation to 5.0 for upland vegetation) do not differ by wetland area but are significantly lower in created wetlands and significantly decrease from one- and two-year-old created wetlands (PI=2.37±0.15; mean±SE) to those five to seven years old (PI=1.96±0.12). Created and restored wetlands support 12.4 and 12.2 species per 10 m² respectively, nearly four times more than the 3.2 species in 10 m² of enhanced wetland. This is in part attributable to a greater incidence of non-native species in created and restored wetlands. The vegetative cover in created mitigation bank wetlands is 18.9±2.8 percent non-native–statistically similar to that of restored (17.6±2.9) but significantly greater than that of enhanced systems (8.7±2.7). Within mitigation methods, there are clear differences among geomorphic and vegetation classes. Depressional systems with a single vegetation class support highly hydrophytic, highly non-native communities with low species richness, while restored and enhanced riverine systems have a greater prevalence of native species. For mitigation bank wetlands in this study, the prevalence of wetland vegetation, the representation of native species, and the plant community homogeneity increase with age, indicating a period of self-organization and a potential trend toward vegetative equivalence with natural wetlands.

We studied from 1998 to 2003 the fine-scale vegetation dynamics of an abandoned vacuum-mined bog located in southern Québec in which cotton-grass (Eriophorum vaginatum) has become dominant. A water table no deeper than 30–40 cm below the soil surface combined with a volumetric peat water content >70% in the surface peat layer favored the increase in cotton-grass cover in abandoned peat fields. In one of the two peat fields that was monitored, the density of living tussocks was 30,750/ha in 1998. The density decreased constantly to reach 25,900/ha in 2002, a 16% decrease. The expansion of cotton-grass cover was mainly the result of the growth of established tussocks following a rise of the water table. The strong relationship between cotton-grass cover and water table suggests that the latter could be used as a predictor for cotton-grass cover change in mined bogs. The present study does not provide evidence that cotton-grass facilitates the establishment of moss species. At the study site, moss establishment was more highly associated with particular hydrologic characteristics (volumetric peat water content ≥85%) than with the presence of a dense cotton-grass cover. The use of cotton-grass to facilitate the establishment of Sphagnum colonies in mined peatlands is questionable, particularly where other efficient restoration techniques are available.

Despite concern about the conservation status of amphibians in western North America, few field studies have documented occurrence patterns of amphibians relative to potential stressors. We surveyed wetland fauna in Oregon's Willamette Valley and used an information theoretic approach (AIC) to rank the associations between native amphibian breeding occurrence and wetland characteristics, non-native aquatic predators, and landscape characteristics in a mixed urban-agricultural landscape. Best predictors varied among the five native amphibians and were generally consistent with life history differences. Pacific tree frog (Pseudacris regilla) and long-toed salamander (Ambystoma macrodactylum) occurrence was best predicted by the absence of non-native fish. Northern red-legged frog (Rana a. aurora) and northwestern salamander (Ambystoma gracile) were most strongly related to wetland vegetative characteristics. The occurrence of rough-skinned newts (Taricha granulosa), a migratory species that makes extensive use of terrestrial habitats, was best predicted by greater forest cover within 1 km. The absence of non-native fish was a strong predictor of occurrence for four of the five native species. In contrast, amphibians were not strongly related to native fish presence. We found little evidence supporting negative effects of the presence of breeding populations of bullfrog (Rana catesbeiana) on any native species. Only the two Ambystoma salamanders were associated with wetland permanence. Northwestern salamanders (which usually have a multi-year larval stage) were associated with permanent waters, while long-toed salamanders were associated with temporary wetlands. Although all the species make some use of upland habitats, only one (rough-skinned newt) was strongly associated with surrounding landscape conditions. Instead, our analysis suggests that within-wetland characteristics best predict amphibian occurrence in this region. We recommend that wetland preservation and mitigation efforts concentrate on sites lacking non-native fish for the conservation of native amphibians in the Willamette Valley and other western lowlands.

The coastal plain of northern Belize consists of relatively undisturbed freshwater marshes that are strongly phosphorus-limited and characterized by monodominant stands or mixtures of emergent macrophytes. In order to assess the impact of agricultural activities on the nutrient dynamics and plant species composition in adjacent wetlands, we sampled along transects in 40 marshes—20 located downslope from agricultural fields and 20 bordered by scrub or broadleaf forest. Soil, water, and plant tissue samples were collected for nutrient analyses, and plant species composition was recorded at points along transects during both the wet and dry seasons. Marshes downslope from agricultural activity had significantly greater percent cover of Typha domingensis, a competitive dominant in the system (20% vs. 6%) and significantly more soil phosphorus (128–144 μg*cm⁻³) than marshes bordered by forest (70–98 μg*cm⁻³). Plant tissue P content was positively correlated with soil P content but not with soil N for Typha (r=0.55) and Eleocharis spp. (r=0.72). Canonical Correspondence Analysis (CCA) identified soil P as the variable most strongly affecting Typha abundance. Abundance of species common to unimpacted marshes (Eleocharis spp., Cladium jamaicense) was negatively correlated with soil P. Further intensification of agriculture in this region may result in expansion of T. domingensis, as has occurred in the Florida Everglades.

We studied the influence of hydroperiod on the composition and richness of the zooplankton community in 19 freshwater temporary ponds of the Doñana National Park (SW Spain) at different spatial and temporal scales. The study ponds were assigned to three hydroperiod categories (long, intermediate, and short) according to previous hydrologic records. During the study period (October 1996–September 1998), wet phases ranged from 56% to 100% of the study period in the five long-hydroperiod ponds, from 25% to 47% in the 10 intermediate-hydroperiod ponds, and from 5% to 21% in the four short-hydroperiod ponds. A total of 56 crustacean species (27 cladocerans, 11 cyclopoids, 5 diaptomids, 1 harpacticoid, 1 notostracan, 1 anostracan, 1 diplostracan) and 47 rotifer taxa were identified from the 19 ponds. Most zooplankton taxa were widely distributed in the ponds. However, Dapnia longispina was restricted to the long-hydroperiod ponds and Metacyclops minutus to the short-hydroperiod ponds. There was a significant (P<0.01) positive correlation between the number of zooplankton taxa collected in each pond over the entire study period (or cumulative richness) and the pond wet-phase length (r= 0.790 for crustaceans and r=0.862 for rotifers, log-transformed data). However, single collection richness (or number of taxa registered in each pond at each sampling date) was not significantly different among hydroperiod categories (Kruskal-Wallis test, P>0.05) for either crustaceans or rotifers. On average, single collection richness represented between 30% and 48% of the cumulative richness, and this percentage was significantly lower in the long- than in the short-hydroperiod ponds (Mann-Whitney tests) for crustaceans (P<0.05) and rotifers (P<0.01). Our data showed that the effect of hydrologic variability on zooplankton taxon richness depended on the temporal scale of observation; it was weakly affected at a momentary scale and strongly affected in the long-term. A longer hydroperiod implied more chance for change in these fluctuating environments.

We studied the distribution and abundance of Nile tilapia, Oreochromis niloticus near two aquaculture facilities for two years in coastal wetlands in southeastern Mississippi, USA. In 280 collections, we represented 29 families, 65 taxa, and 86,415 fishes with a variety of gear types. Oreochromis niloticus ranked sixth in abundance overall and ranked second among those stations sampled in the Pascagoula River watershed and sixteenth among Coastal River stations. Water temperature downstream from the facility effluents was always warmer than ambient, and at the Pascagoula River facility, it never dropped below 15.1°C over the three years examined. Thus, normal environmental conditions, the presence of the downstream thermal refuge, and the generally low salinity of the bayous of our region all combine to provide a quality environment for continued survival of released fish. Furthermore, O. niloticus seem to spawn year-round, and fish as small as 79.9 mm TL were found to carry mature eggs, suggesting that, if they are born early in the season, they could reproduce during their first summer of life. Further spread of O. niloticus and introduction of new species are expected as aquaculture expands. The philosophy that allows the escape or release of non-indigenous taxa into our present landscape, justified by the belief that species will not survive or become established, is fallible.

Salt marshes offer a valuable opportunity to study the effects of environment on the clonal growth of species able to live throughout a wide vertical range on the tidal frame. Spartina densiflora is a species native to South America that is invading marshes in SW Europe, NW Africa, and SW North America, where its populations are found from low to high topographic elevations, altering the composition of plant communities. The aim of this study was to increase our knowledge regarding the competitive ability of S. densiflora, analyzing its clonal growth and its ramet demography during 25 months in two expanding populations at a low and a high marsh. Four clonal characteristics were recorded in both populations: (1) dense occupation of available space inside tussocks; (2) lack of a dormant period and high tiller production rates and growth; (3) evidence of physiological integration between ramets; and (4) high rates of sexual reproduction. Furthermore, S. densiflora developed different strategies of clonal growth in contrasting habitats. Tussocks in the low marsh had lower tiller longevity and higher tiller density, natality, and mortality rates, showing faster ramet turnover than in the high marsh. These clonal growth traits would facilitate S. densiflora persistence under the effects of catastrophic events. Spartina densiflora clonal growth traits indicate strong adaptability to different environmental conditions and strong competitive ability, since its tiller dynamics enable it to invade occupied space, and it effectively colonizes new safe-sites by sexual reproduction. These observations help us to understand how this invader has become the most abundant plant in many estuaries of the SW Iberian Peninsula.

Wetland destruction has plagued the U.S. for decades, but the need to compensate for these losses has only been embraced within the last 20 years. Because so many compensatory mitigation wetlands have been created, there is a need to assess the function of these valuable ecosystems relative to natural wetlands. The goal of this study was to evaluate the functional equivalency of mitigation wetlands in West Virginia in supporting hydrophytic plant communities. A series of nested quadrats was used to compare plant community structure among eleven mitigation and four naturally occurring reference wetlands. For all species combined, mean total percent cover across all sampling quadrats per wetland was similar between mitigation and reference wetlands. Species richness, evenness, and diversity were greater in mitigation than in reference wetlands. Mean weighted averages of plant communities calculated using cover values and wetland indicator status were similar between mitigation and reference wetlands. There were, however, major differences in species composition. Mitigation sites tended to have more pioneer species, non-native dominants, and species with relatively lower conservation quality. Ordination analyses suggested that compositional differences become smaller as mitigation sites age. Both mitigation and natural wetlands met criteria for hydrophytic vegetation according to the 1987 U.S. Army Corps of Engineers Wetland Delineation Manual. These data suggest that the mitigation wetlands investigated in this study adequately support hydrophytic vegetation and appear to be developing vegetation similar to reference standards.

We analyzed the transverse pattern of vegetation along a reach of the Fremont River in Capitol Reef National Park, Utah, USA using models that support both delineation of wetland extent and projection of the changes in wetland area resulting from upstream hydrologic alteration. We linked stage-discharge relations developed by a hydraulic model to a flow-duration curve derived from the flow history in order to calculate the inundation duration of 361 plots (0.5 × 2 m). Logistic regression was used to relate plant species occurrence in plots to inundation duration. A weighted average of the wetland indicator values of species was used to characterize plots as Aquatic, Wetland, Transitional, or Upland. Finally, we assessed how alterations in the flow duration curve would change the relative widths of these four zones. The wetland indicator values of species and the wetland prevalence index scores of plots were strongly correlated with inundation duration. Our results support the concept that plants classified as wetland species typically occur on sites inundated at least two weeks every two years. The portion of the riparian zone along the high-gradient study reach of the Fremont River that satisfied the vegetation criterion for a regulatory wetland was narrow (2 m wide). Both the unvegetated Aquatic zone (7.8 m) and the Transitional zone (8 m) were substantially wider. The Transitional zone included the maxima of several species and was, therefore, not merely a combination of elements of the Wetland and Upland zones. Multiplicative increases or decreases in streamflow regime produced a wetter, or drier, bottomland vegetation, respectively. Systematic reductions in flow variability reduced the width of both the Wetland and Transitional zones and increased the width of the Upland zone. Our approach is widely applicable to inform water management decisions involving changes in flow regime.

Greenhouse studies using soil-plant plugs extracted from a Spartina patens marsh receiving diverted Mississippi River water shows that lowering of salinity and increased nutrient input associated with freshwater reintroduction into Louisiana estuaries will enhance nutrient uptake and biomass production of wiregrass (Spartina patens). Biomass production doubled in response to the addition of 10g N m⁻². A salinity-nutrient interaction was shown. Plants grown in fertilized treatments at 0 ppt had significantly greater biomass production than plants grown under fertilized treatment and 8 ppt salinity. However, a significantly greater amount of biomass was measured in both fertilized treatments (0 and 8 ppt) as compared to control. Lowering of salinity alone also stimulated plant growth. Results demonstrated that proposed reintroduction of Mississippi River water into Spartina patens marshes of Breton Sound should enhance plant growth and improve marsh stability.

The practice of wetland mitigation has come into question during the past decade because the relative capacity of the mitigated wetlands to perform normal wetland functions is mostly unknown. In this study, we wanted to determine whether soil microbial communities were significantly different in early successional mitigated wetlands (<10 years) (ES) compared to late successional bottomland hardwood forest wetlands (LS) due to differences in soil properties, such as carbon quality and storage and water-holding capacity. Carbon storage in litter and soil was 1.5 times greater in LS wetlands than ES wetlands. Soil water-holding capacity was significantly greater in LS wetlands and was related to soil organic C content (r²=0.87, p-value=0.0007). Gravimetric water content was a moderately strong predictor of microbial respiration (r²=0.55–0.61, p-value=0.001–0.0004) and microbial biomass (r²=0.70, p-value=0.0019). Anaerobic microbial groups were enriched in soils from LS wetlands in both the dry and wet seasons, which suggested that LS soils were wetter for longer periods of the year than ES soils. The capacity of these wetlands to support anaerobic microbial processes depends on soil water retention characteristics, which were dictated by organic matter content. As an integrator of microbial growth conditions in soils, determination of microbial community composition by phospholipid fatty acid (PLFA) analysis may be an important new tool for monitoring successional development of compensatory mitigation wetlands.

Understanding the hydrologic patterns in vast wetland ecosystems has proven to be a difficult task. Most of the world's wetland ecosystems are not adequately monitored for water level, flow, or discharge, and where these are monitored, gauges are usually located on the largest rivers or lakes and canals rather than in the seasonally flooded areas. Even those wetlands that have the most extensive networks of gauges are not sufficiently covered to understand the finer-scale spatial dynamics of hydrologic condition. However, high-density in situ monitoring of stage, flow, and discharge of vast wetland complexes would be prohibitively expensive, even in a region such as south Florida, USA where considerable resources are devoted to water management. Several techniques are presented that were developed to use Synthetic Aperture Radar (SAR) satellite imagery to remotely detect, monitor, and map regional scale spatial and temporal changes in wetland hydrology. This study shows that SAR imagery can be used to create inundation maps of relative soil moisture and flooding in non-woody wetlands. A comparison of in situ water-level data collected from 1997 to 1999 at 12 test sites to SAR imagery revealed that relative backscatter within a site does vary in a linear fashion with changes in water levels. Using SAR imagery collected between 1997 and 1999, inundation maps were created at approximately bi-monthly periods for the south Florida region. This time series of inundation/soil moisture maps (1997–1999) reveals the spatial and temporal variation in degree of flooding in the Greater Everglades, which is information previously unavailable from ground-based observations alone. In addition, hydroperiod maps were created based on a temporal series of 14 months of SAR imagery.

In the Adirondack region of northern New York, USA, Alnus incana ssp. rugosa and Myrica gale often dominate wetland shrub communities and fix nitrogen in symbiosis with actinomycetes of the genus Frankia. The objective of this study was to examine the contribution of these shrubs to the N economies of whole wetlands in the Adirondacks where N has been considered a potential pollutant and contributor to low acid-neutralizing capacity, and where N deposition may reduce rates of nitrogen fixation in actinorhizal plants. Nitrogen chemistry of plant foliage was examined, and density and foliar biomass of nitrogen fixing shrubs were estimated in plots or belt transects in six shrub wetlands near atmospheric deposition monitoring stations in order to estimate the fraction of N derived from fixation in A. incana ssp. rugosa and M. gale tissues. Lake-inlet-wetlands were dominated by alder that derives ≥85% foliar N from fixation, but M. gale was most abundant in lake outlet wetlands and seemed to rely less on fixed N, although results for Myrica were more uncertain. Substantial N is therefore added to lake inlet systems dominated by alder (7–18 kg ha⁻¹ yr⁻¹), while N fixed from M. gale does not appear to exceed 3 kg ha⁻¹ yr⁻¹, except in localized patches at smaller spatial scales. Similarity in δ¹⁵N between non-fixing field shrubs and reference values for fixed N at some sites suggests that fixed N is being recycled in the plant community. Wet atmospheric N deposition is 3–6 kg ha⁻¹ yr⁻¹ and does not decrease N fixation substantially in alder. Overall, shrubs in wetlands dominated by these actinorhizal N₂—fixing plants are not taking up substantial quantities of anthropogenic N, suggesting that nitrogen is processed microbially or transferred along with some fixed N to downstream ecosystems.

This study examined chironomid responses to the flooding of ten drained experimental marshes in Delta Marsh, Manitoba, Canada. Emergence traps were used to monitor chironomid emergence from three vegetation types (Symphyotrichum ciliatum, Scolochloa festucacea, and Schoenoplectus tabernaemontani) flooded at two water depths (shallow: 20–40 cm, deep: 50–70 cm) over a four-year period. The greatest number (7,651 m⁻² yr⁻¹) and biomass (20.3 g m⁻² yr⁻¹) of chironomids emerged from Schoenoplectus-deep sites in the fourth year of flooding. Numbers, biomass, and size classes of emerging chironomids were similar over the four years from the Symphyotrichum habitat. However, chironomid emergence from Scolochloa and Schoenoplectus habitats was dominated initially by the smallest size class but shifted steadily toward production of much larger species over the four-year experiment. The production of chironomids as a potential food resource for waterfowl was high from the Symphyotrichum habitat during all four years of flooding, but emergence from the Scolochloa and Schoenoplectus habitats did not reach comparable levels until the third or fourth year.

Herbaceous species comprise most of the floristic diversity in semi-arid region riparian zones, yet little is known about their response to river flooding. We compared cover, richness, and distribution of six functional groups of herbaceous plants after a large fall flood (pre- vs. post-flood year comparison) and after small monsoon floods and rains (dry vs. wet season contrast), and compared richness across a longitudinal (upstream-downstream) gradient of flood intensity. Herbaceous cover and richness increased significantly (p≤0.05, ANOVA) from the pre-flood to post-flood year and from the dry to wet season. Overall, the post-flood increases in richness and cover were related to the combined effects of disturbance (as indicated by strong increases of annual plants) and increased water availability (as indicated by response patterns of hydric perennials and other functional groups). All annuals showed strong increases in richness and cover in the year following the large fall flood, with hydric annuals increasing in richness by 43%, mesic annuals by 52%, and xeric annuals by 75%. Hydric perennials had a small net increase in richness following the large flood, reflecting a positive response to increased flow permanence, countered by low richness at sites with very high flood intensity (total stream power). Mesic and xeric perennials did not change significantly in richness from the pre- to post-flood year. However, across the spatial flood intensity gradient, the richness response pattern of the annuals and perennials alike peaked at intermediate levels of disturbance. In response to seasonal rains and moderate flooding, hydric perennials did not change in abundance, reflecting their primary association with shallow ground water and perennial stream base flows, but mesic perennials increased in cover and xeric perennials increased in both cover and richness. All three annual groups increased in cover and richness and in distribution across the flood plain following the summer monsoon floods and rains: hydric annuals had peak cover in inundated zones, suggesting positive response to river flooding, while xeric annuals peaked in cover above inundation zones, suggesting positive response to increased rainfall; mesic annuals had intermediate patterns. During the dry season, in contrast, annuals had low richness and cover and were restricted to low elevation fluvial surfaces adjacent to the stream channel and/or underlain by shallow ground water. Overall, both disturbance and increased moisture conditions caused by floods, as well as moisture from seasonal rains, contribute to increased richness and cover of herbaceous plants within the flood plain of the San Pedro River.

I assessed the relationship between ostracod occurrence and ecological variables in the Yumrukaya reedbeds (Bolu, Turkey), describing how differences in water conditions affected the composition of ostracod assemblages in this small freshwater wetland. Between May 2000 and July 2002, seven ostracod taxa (Cypridopsis vidua, Ilyocypris bradyi, I. gibba, Heterocypris incongruens, Eucypris virens, Candona neglecta, Pseudocandona sp.) were collected. All the ostracods had cosmopolitan characteristics, with broad ranges of tolerance to the variations in ecological variables and the capacity to either resist desiccation or to recolonize newly flooded habitats. The number of ostracods found in Yumrukaya reedbeds was about 50% lower than the average number of ostracods in similar sized habitats of Turkey. The Unweighted Pair Group Mean Averages (UPGMA) clustering analysis based on presence/absence data displayed three groups of ostracods and suggested that cosmopolitan species might have similar life cycles and ecological preferences. Correlation analyses indicated that salinity and percent oxygen saturation were significantly associated with species richness.

In this work, we propose a new tagging technique to evaluate NAPP in Scirpus giganteus (bulrush), a species commonly found in freshwater marshes of South America. Through this method, a total mean NAPP of 1514.12 ± 305.11 g m⁻² year⁻¹ (C.V.= 20%) was obtained by a combination of tagging and harvesting entire mats. A maximum living biomass of 1063.60 ± 362.06 g m⁻² (C.V.= 34%) was registered in February (late summer), which would be the estimation of the total annual NAPP using the traditional peak standing crop method and gives an underestimation of NAPP because it neither considers mortality before the peak biomass is attained, nor does it include any production after peak. As there are no statistically significant changes in the mean living biomass on different sampling dates (df=9, F=2.22, p>0.10), which is an expected situation in a species that grows through the whole year, methods based on changes in living and dead biomass are difficult to apply. The proposed tagging method gives an estimate of NAPP for a species on which more widely used procedures cannot be applied. Moreover, the tagging technique may be applicable for a great number of emergent wetland plants showing similar growth forms.