Days Of Inundation Research Articles

The interaction between N, P in the overlying water of the reservoir Water-level fluctuation zone and submerged decomposition of Cynodon dactylon

During the process of inundation in the Water-level fluctuation zone(WLFZ), the N and P content in the overlying water will vary due to the release of soil nutrients, directly impacting the decomposition process of plants. However, current research on the effects of such water changes on plant decomposition is insufficient, hindering an accurate assessment of its impact on water environments. This study simulated changes in water quality during inundation and designed 8 types of water with different initial nutrient levels. Taking the typical WLFZ plant, Cynodon dactylon, as the subject, the decomposition and dynamic changes of N and P in these water bodies were studied. The results showed that inundation significantly increased the N and P content in the water, and the initial forms of N and P significantly affected the release of plant decomposition during inundation. Moreover, the release of PN and PP from the soil stimulated the activity of aquatic microorganisms, enhancing the self-purification capacity of the water body, and leading to a decrease in N and P content in the water body after 60 days of inundation. This study reveals the impact of N and P released from WLFZ soil on plant decomposition and the concentrations of N and P in the overlying water. providing critical insights into WLFZ ecosystem management.

Can germination strategies help to understand regional co‐occurrence of two morphologically conserved congeneric macrophytes?

Abstract In variable environments the production of dormant life stages can help organisms to avoid periods that are unsuitable for growth and reproduction, and different species may rely on different cues to break dormancy. However, it is still unclear to what extent variation in germination strategies can help to explain variation in the distributions of related species and contribute to adaptive radiation. Using standardised laboratory germination trials, we demonstrated the existence of both inter‐ and intraspecific variation in germination strategies in two congeneric species of submerged macrophytes that occur in a dynamic wetland system characterised by strong variation in salinity and hydro‐regime. The ditch grass Ruppia maritima L. typically lives in temporary waterbodies, where it assures high seed set through a short life cycle, early flowering and self‐pollination. Its congeneric Ruppia spiralis L. ex Dumortier grows in (semi‐)permanent waterbodies where it can have a perennial life cycle. Populations are presumed to be maintained mainly through clonal growth, and seed production is lower than in R. maritima. We hypothesised that salt and temperature are two important germination cues in these ecosystems that can explain the observed differences in distribution patterns between these two species. We exposed seeds of both species in a full factorial designed experiment to four different salinities (0‰, 7‰, 14‰ and 21‰) and two different temperature regimes (17 and 24°C, simulating spring and summer temperatures, respectively). The experiment was repeated over three consecutive inundation cycles (30 days of inundation, followed by 30 days of drought). During the third cycle, all seeds were inundated with fresh water, as salinity might constraint germination in species that rely on fresh water for germination. We found that the R. maritima seeds had overall low germination success. The freshwater inundation caused rapid germination in seeds that previously were in a high‐salinity treatment. In R. spiralis, which inhabits more permanent habitats of variable salinity, we detected a more complex response, involving two germination peaks. These two contrasting germination strategies observed within R. spiralis could target spring or summertime growing periods respectively. We believe that the observed variation in germination strategies is an important element in ecological differentiation in the morphologically conserved genus Ruppia and may have contributed to past and ongoing speciation.

Application of Intermittent Irrigation to Improve Growth and Yield of Various Rice Varieties (Oryza sativa L.)

Intermittent irrigation can save water use in rice cultivation, which is essential, especially during the dry season. This study aims to improve the physiology of the growth and yield of rice in various varieties by applying intermittent irrigation. The research was conducted from February to June 2019 in the experimental field of the Faculty of Agriculture, Universitas Muhammadiyah Yogyakarta. The research used a factorial experimental method 3 x 4 strip plots arranged in a Completely Randomized Block Design with three replications. The factor I rice varieties consist of Cempo Merah, Inpari 23, Sintanur, and Inpari 42. Factor II is the irrigation system consisting of continuous flooding, ten days of inundation, five days of drying, seven days of inundation, and three days of drying. There is an interaction between types of irrigation and rice varieties on the number of tillers. In Ten-day watering five-day drying, Sintanur and Inpari 42 variety produce more tillers than Inpari 23. On Seven days watering five-day drying, the Inpari 42 variety produces more tillers than Inpari 23. There are the differences in the responses of various rice varieties to the Specific Leaf Weight and yield. Specific Leaf Weight rice Cempo Merah varieties are higher than, Inpari 23, Sintanur and Inpari 42. Rice yield of Inpari 42 variety is higher than Cempo Merah, Inpari 23, and Sintanur varieties. Roots with watering seven days watering, three days of drying is longer than Ten-day watering five-day drying. Roots with watering Ten-day watering five-day drying is longer than conventional.

Developing a multivariable lookup table function for estimating flood damages of rice crop in Vietnam using a secondary research approach

It is increasingly important to evaluate the economic flood damage toward agricultural crops to further improve decision-making and mitigate flood impacts in developing countries. In this study, we derive a multivariable lookup table function for estimating flood damages to rice crops based on a secondary research approach, which involves collecting and integrating fragmented secondary information sources of rice damage caused by inundation and event data observed in southern rural areas of the Ca River Basin, Central Vietnam. The derived lookup table function includes the effects of the rice growth stages on the damage caused, in addition to flooding parameters such as inundation level and inundation duration. This indicates that the rice crops are generally the most vulnerable and robust to inundation in the ripening and the reproductive stages. The yield loss in the ripening stage dramatically increases from 50% to 90% when the complete inundation lasts 5–8 days. Even after 7 days of 75% inundation, the yield hardly decreased at the reproductive stage and was reduced by almost half for 7 days of complete inundation. Four–five days of complete inundation at the ripening and vegetation stages are likely to cause almost the same damage to rice crops as that caused by 7 days of inundation at the reproductive stage. Utilization of the function to estimate rice damage in four flood events reveals that the derived multivariable function captures flood damages well and outperforms the univariable damage functions for the target area.

The response of local rice varieties with intermittent irrigation with microclimate factors

Intermittent irrigation is a method carried out for irrigation efficiency in rice farming. This study aims to discover the effect of local rice varieties and types of irrigation and their interaction on rice microclimate factors. The study was conducted with an experimental method of factorial 3 × 4 strip plot design with a Randomized Completely Block Design (RCBD) with 3 replications. Type of irrigation consisted of 3 levels: conventional irrigation, irrigation ten days inundated five days dry, and irrigation seven days inundated three days dry. Rice varieties comprised four groups: Rojolele, Pandan Wangi, Mentik Wangi, and Ciherang. The results showed that the Pandan Wangi rice variety with seven days of inundation in 3 dry days had higher temperatures above the canopy. During the initial vegetative, irrigation ten days inundated five days dry and seven days inundated three days dry had higher soil temperatures above the surface than conventional irrigation. When flowering, irrigation seven days inundated three days dry has a soil temperature-depth of 15 cm higher than conventional irrigation and irrigation ten days inundated five days dry. The microclimate condition was expected to be useful concerning plant physiology, pests, diseases, and rice weeds and their control.

Soil Conditions Following Hydrologic Restoration in Cypress Dome Wetlands

Soil characteristics and decomposition rates were investigated in 12 geographically isolated wetlands (cypress domes) across a gradient of hydrologic alteration (altered, marginally altered and least altered sites) seven years after passive recovery from historic groundwater withdrawals. Above- and belowground decomposition rates were determined in transition (seasonally flooded) and outer deep (semi-permanently) hydrologic zones. Flood duration, frequency, redox conditions, pH, and soil organic matter were measured to potentially explain patterns across the alteration gradient. Despite the reduction in groundwater withdrawals, altered sites exhibited fewer days of inundation in transition and outer deep zones compared to marginally altered and least altered wetlands. Over a 56 week period, altered wetlands displayed greater decomposition in the aboveground outer deep zone (73.3 ± 4.0% mass remaining) and in the belowground transition zone (62.0 ± 4.5% mass remaining) compared to marginally and least altered sites. Analyses indicated that marginally altered wetlands were more comparable to least altered wetlands however differences in altered wetland soils (including decomposition) persist. Although wetland hydrology has been partially restored, additional time and/or further site augmentation may be needed for altered sites to be functionally equivalent to least altered wetlands and in some cases (e.g., excessive subsidence) the degree of past alteration may limit restoration potential.

Trophic relay and prey switching – A stomach contents and calorimetric investigation of an ambassid fish and their saltmarsh prey

Trophic relay is an ecological model that involves the movement of biomass and energy from vegetation, such as saltmarshes, within estuaries to the open sea via a series of predator-prey relationships. Any potential for trophic relay is therefore affected by water movements within an estuary and by the ability of a predator to “switch” prey in response to fluctuating abundances of those prey. Saltmarsh-dwelling grapsid crabs, which feed on saltmarsh-derived detritus and microphytobenthos, release zoeae into ebbing tides that inundate saltmarshes during spring-tide cycles within tidally-dominated estuaries, such as Brisbane Water Estuary, therefore providing an opportunity to examine whether prey-switching and/or trophic relay may occur in fish that feed on those zoeae (such as the highly abundant estuarine ambassid, Ambassis jacksoniensis). This model was examined by sampling A. jacksoniensis near saltmarshes in a large, temperate south-eastern Australian estuary during flood and ebb tides on days of saltmarsh inundation and non-inundation over four spring-tide events in 2012. Stomach fullnesses of A. jacksoniensis were generally highest during ebb tides on days of saltmarsh inundation, implying that feeding was most marked at these times. Caridean decapods dominated diets during flood tides and on days of no saltmarsh inundation, while crab zoeae dominated diets during ebb tides and on days of inundation, suggesting that, when saltmarsh-derived zoeae became abundant, A. jacksoniensis switched to feeding on those prey. Three potential zooplankton prey (calanoid copepods, caridean decapods and crab zoeae) did not differ calorimetrically, indicating that switching of prey by A. jacksoniensis is not directly related to their preying on energetically greater prey, but reflects opportunistic feeding on more abundant and/or less elusive prey. As A. jacksoniensis is able to switch prey from estuarine caridean decapods to saltmarsh-derived crab zoeae, this very abundant ambassid would be well-placed to promote any trophic relay, via further water movements or other predator-prey relationships, to the adjacent marine environment.

Nitrate leaching from short-hydroperiod floodplain soils

Abstract. Numerous studies have shown the importance of riparian zones to reduce nitrate (NO3−) contamination coming from adjacent agricultural land. Much less is known about nitrogen (N) transformations and nitrate fluxes in riparian soils with short hydroperiods (1–3 days of inundation) and there is no study that could show whether these soils are a N sink or source. Within a restored section of the Thur River in NE Switzerland, we measured nitrate concentrations in soil solutions as an indicator of the net nitrate production. Samples were collected along a quasi-successional gradient from frequently inundated gravel bars to an alluvial forest, at three different depths (10, 50 and 100 cm) over a one-year period. Along this gradient we quantified N input (atmospheric deposition and sedimentation) and N output (leaching) to create a nitrogen balance and assess the risk of nitrate leaching from the unsaturated soil to the groundwater. Overall, the main factor explaining the differences in nitrate concentrations was the field capacity (FC). In subsoils with high FCs and VWC near FC, high nitrate concentrations were observed, often exceeding the Swiss and EU groundwater quality criterions of 400 and 800 μmol L−1, respectively. High sedimentation rates of river-derived nitrogen led to apparent N retention up to 200 kg N ha−1 yr−1 in the frequently inundated zones. By contrast, in the mature alluvial forest, nitrate leaching exceeded total N input most of the time. As a result of the large soil N pools, high amounts of nitrate were produced by nitrification and up to 94 kg N-NO3− ha−1 yr−1 were leached into the groundwater. Thus, during flooding when water fluxes are high, nitrate from soils can contribute up to 11% to the total nitrate load in groundwater.

Estimation of structural vulnerability for flooding using geospatial tools in the rural area of Orissa, India

Vulnerability assessment of natural disasters is a crucial input for risk assessment and management. In the light of increasing frequency of disasters, societies must become more disaster resilient. This research tries to contribute to this aim. For risk assessment, insight is needed into the hazard, the elements at risk and their vulnerabilities. This study focused on the estimation of structural vulnerability due to flood for a number of structural elements at risk in the rural area of Orissa, India (Kendrapara), using a community-based approach together with geospatial analysis tools. Sixty-three households were interviewed about the 2003 floods in 11 villages and 166 elements at risk (buildings) were identified. Two main structural types were identified in the study area, and their vulnerability curves were made by plotting the relationships between flood depth and vulnerability for each structural type. The vulnerability ranges from 0 (no damage) to 1 (collapse/total damage). Structural type-1 is characterized by mud wall/floor material and a roof of paddy straw, and structural type-2 is characterized by reinforced cement concrete (RCC) walls/floor and a RCC roof. The results indicate that structural type-1 is most vulnerable for flooding. Besides flood depth, flood duration is also of major importance. Houses from structural type-1 were totally collapsed after 3 days of inundation. Damage of the houses of structural type-2 began after 10 days of inundation.

Do changes in flood pulse duration disturb soil carbon dioxide emissions in semi-arid floodplains?

In semi-arid floodplains the average times between floods have been cited to drive metabolic and biogeochemical responses during the subsequent flooding pulse. However, the interaction effects of flood pulse duration and the length of time between floods on the carbon budget are not well understood. Using field experiments, flood pulses—dry cycles were simulated (SF plots—short flood/dry cycles: 15 flood days + 7 dry + 15 flood and LF plots—long flood/dry cycles: 21 flood + 14 dry + 21 flood) in a semi-arid floodplain in Central Spain, in order to study the effects on soil CO2 emissions. Differences on soil water content among SF, LF and control plots were statistically significant throughout the experiment (p < 0.01). Soil CO2 emission rates during drying time were significantly related with the duration of previous flooding and inter-flooding intervals (R2 = 0.52–0.64, p = 0.03). During the first stage of desiccation, the high soil water content appears to limit aerobic metabolism. Soil respiration rates similar to those of control plots measurements occurred 1–2 weeks later. Then, soil respiration increased to a maximum rate which was delayed 5–8 weeks, as high soil water content limited microbial activity. While more than 7 days of inundation promoted denitrification, organic nutrients supplied by flood water increased 1% soil respiration during drying. Differences between SF and LF plots in soil CO2 emissions only appeared after floodplain soil had been subjected to two consecutive flood-dry cycles; 70 days after the second inundation ended, CO2 fluxes achieved similar values in all treatments. Daily soil CO2 emission rates during the entire study period (117 days) were comparable, independently of the flood duration and the time between floods (75.76 ± 1.59 and 77.94 ± 0.45 mmol CO2 m−2 day−1, in SF and LF, respectively). Flood disturbance affects site-specific microbial processes, but only during very short time periods. The mechanism by which soil microbial communities cope or adapt to new conditions needs to be reassessed in future research in order to determine the long-term effects of hydrological changes in the soil carbon balance of semi-arid floodplains.

Short-term response of nutrients, carbon and planktonic microbial communities to floodplain wetland inundation

Environmental flows were released to the Macquarie Marshes (~210,000 ha) in north-west NSW of Australia between October and December 2005, inundating an estimated 24,600 ha of floodplain area. According to the flood pulse concept, the marsh floodplains would have stored large amounts of nutrients and carbon during dry antecedent conditions, which would be released into the overlaying flood water. Field studies were conducted in mid-December 2005 at two sites, one on open floodplain woodland with a sparse canopy of River Red Gum and ground cover dominated by saltbushes and the other on open floodplain with black roly-poly. At each site, nutrients, dissolved organic carbon (DOC), planktonic bacteria and phytoplankton were monitored daily for a 6-day period from the overlaying water of a floodplain inundated by the environmental water release. Those in mesocosms deployed in situ, containing marsh floodplain sediments that had been inundated artificially, were also monitored. The mesocosm results from both the sites showed that release of nitrogen was rapid, attaining mean concentrations of total nitrogen of 3.7–14.8 mg l−1, followed by more gradual increases in total phosphorus (mean concentrations 0.6–0.8 mg l−1) and DOC (26.1–50.2 mg l−1) within the 6-day experiment; planktonic microbial communities developed concomitantly with the increasing concentrations of nutrients and DOC, attaining mean densities of (6.0–6.9) × 106 cells ml−1 of planktonic bacteria and (80.7–81.4) × 103 cells ml−1 of phytoplankton; and for each site the overall measured condition of the mesocosm tended to approach that of the Marshes, over the course of the 6-day experiment. The present study (both observational and experimental) demonstrates that the floodplain sediments in the Marshes, which have been exposed to dry antecedent conditions, release nutrients and carbon to the overlaying flood water following inundation. These resources are thought to have been stored during the dry antecedent phase in accord with the flood pulse concept. Based on the mesocosm experiment, the released nutrients and carbon are in turn most likely to be used by microbial components, such as bacteria and algae, which develop within days of inundation of the floodplain sediments. Thus, environmental flow release provides potential for floodplains to attain a series of ecological responses including initial release of inorganic nutrients and dissolved organic matter and increase in planktonic bacteria and phytoplankton.

Changes in soil chemical properties with flooding: A field laboratory approach

Phenolic compounds, which can affect the availability of soil nitrogen (N) for plants, may accumulate in the soil under flooded conditions. The objective of this study was to determine if short-duration floods (i.e., 3 vs. 5 weeks) with varying flow rates (i.e., stagnant vs. flowing) would affect soil inorganic-N or polyphenolic content under field conditions. Our study site was an outdoor research facility used for evaluating flood tolerance of various plant species. Flood conditions (i.e., timing, depth, duration, and flow rate) at this facility can be manipulated making it ideal for a field-based investigation of the effects of flooding on soil chemical and environmental properties. Four flood treatments (non-flooded control, 3-week-flowing flood, 5-week-flowing flood, and 5-week stagnant flood) were implemented in May–June, 2005. Soil redox potential, pH, temperature, volumetric water content and dissolved oxygen were monitored over the course of the flood treatments with automated sensors. Pre- and post-flood soil samples were collected and analyzed for inorganic-N content, total N, total organic C, and total soluble polyphenolics. Sensor data revealed a decrease in redox potentials and dissolved oxygen with flooding; however, differences between flood treatments were not significant. Both 5-week flood treatments developed anaerobic soil conditions within 12 days of inundation; anaerobic conditions were maintained for these treatments until dry-down. Soil conditions in the 3-week-flowing treatment remained generally in the suboxic range. Significant differences in soil temperature, volumetric water content and pH were not observed. Flooding affected soil inorganic-N in that NO 3–N decreased under 5-week flood treatments and increased under 3-week-flowing and control treatments. Losses in soil NO 3–N were nearly 4 times greater for the 5-week-stagnant treatment than the 5-week-flowing treatment. Trends included all flood treatments (including the control) showing increases in soil NH 4–N and most flood treatments (all except the 5-week-flowing) showing decreases in soil polyphenolic content. Changes in soil NH 4–N and polyphenolics, as well as TN, TOC and C:N ratio with flooding were not significant. Short-duration floods in this facility, therefore, did not result in the accumulation of polyphenolics in the soil. Other changes in soil chemistry, such as TN and TOC were minimal and not significant despite development of anaerobic soil conditions.

The effect of flooding on the exchange of the volatile C&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-compounds ethanol, acetaldehyde and acetic acid between leaves of Amazonian floodplain tree species and the atmosphere

Abstract. The effect of root inundation on the leaf emissions of ethanol, acetaldehyde and acetic acid in relation to assimilation and transpiration was investigated with 2–3 years old tree seedlings of four Amazonian floodplain species by applying dynamic cuvette systems under greenhouse conditions. Emissions were monitored over a period of several days of inundation using a combination of Proton Transfer Reaction Mass Spectrometry (PTR-MS) and conventional techniques (HPLC, ion chromatography). Under non-flooded conditions, none of the species exhibited measurable emissions of any of the compounds, but rather low deposition of acetaldehyde and acetic acid was observed instead. Tree species specific variations in deposition velocities were largely due to variations in stomatal conductance. Flooding of the roots resulted in leaf emissions of ethanol and acetaldehyde by all species, while emissions of acetic acid were only observed from the species exhibiting the highest ethanol and acetaldehyde emission rates. All three compounds showed a similar diurnal emission profile, each displaying an emission burst in the morning, followed by a decline in the evening. This concurrent behavior supports the conclusion, that all three compounds emitted by the leaves are derived from ethanol produced in the roots by alcoholic fermentation, transported to the leaves with the transpiration stream and finally partly converted to acetaldehyde and acetic acid by enzymatic processes. Co-emissions and peaking in the early morning suggest that root ethanol, after transportation with the transpiration stream to the leaves and enzymatic oxidation to acetaldehyde and acetate, is the metabolic precursor for all compounds emitted, though we can not totally exclude other production pathways. Emission rates substantially varied among tree species, with maxima differing by up to two orders of magnitude (25–1700 nmol m−2 min−1 for ethanol and 5–500 nmol m−2 min−1 for acetaldehyde). Acetic acid emissions reached 12 nmol m−2 min−1. The observed differences in emission rates between the tree species are discussed with respect to their root adaptive strategies to tolerate long term flooding, providing an indirect line of evidence that the root ethanol production is a major factor determining the foliar emissions. Species which develop morphological root structures allowing for enhanced root aeration produced less ethanol and showed much lower emissions compared to species which lack gas transporting systems, and respond to flooding with substantially enhanced fermentation rates and a non-trivial loss of carbon to the atmosphere. The pronounced differences in the relative emissions of ethanol to acetaldehyde and acetic acid between the tree species indicate that not only the ethanol production in the roots but also the metabolic conversion in the leaf is an important factor determining the release of these compounds to the atmosphere.

Vegetation along hydrologic, edaphic, and geochemical gradients in a high-elevation poor fen in Canaan Valley, West Virginia

Wetland plant community composition and pattern are regulated by a host of abiotic/environmental gradients and biotic factors. We used multivariate analyses to classify wetland plant communities and determine the relation of hydrologic, edaphic, and geochemical gradients on community composition and spatial distribution among 18 vegetation, hydrology, and soil sampling points in Abe Run, a botanically unique poor fen in northeastern West Virginia. We also examined the interactions of disturbance with the physical environment and species composition. A total of 179 vascular plant species were identified from sample plots. Vegetative composition and structure, dominant soil texture, and hydrology lacked the distinct concentric zonation of northern peatlands; instead, all were patchy and varied considerably over short distances. Graminoid-forb meadows with primarily silt-loam mineral horizons, greater depth to groundwater, and fewer days of inundation characterized the lower reaches of the wetland. These plots were more acidic, with absent or shallow O horizons, and lower concentrations of soil base cations (Ca, Mg, K). In the upper reaches of the wetland, mixed herb-shrub-tree dominated communities were structurally and compositionally more complex; here, organic horizons were much more prominent, peat depth ranged from 80 to 100 cm, and the average depth to water table was 10 cm less than for wells in the lower reaches of the wetland. Plots from upper transects (3–6) tended to have more shrub and tree cover, and higher concentrations of soil base cations. Much of the variability among plots in the upper and lower reaches of the wetland are consistent with beaver inundation of a large portion of the wetland during the 1980s. Multiple-response permutation procedures verified the difference (P < 0.0001) between vegetation of plots in the lower and upper reaches of the watershed. Because fens are connected to groundwater, these habitats are particularly vulnerable to disturbances, particularly those that alter existing land use and land cover. Minimization of disturbances in the surrounding watershed, controls on an excessive deer population, removal of exotic, non-native species, and control on foot traffic are all integral to maintaining the integrity of this high-value wetland.

Effect of inundation duration on Salix gracilistyla density and size on a gravel bar

To clarify the effects of inundation on the establishment of Salix gracilistyla trees, the relationship between total inundation duration and the distribution and size of trees was examined on a gravel bar along the Miya River in central Japan. The density of S. gracilistyla was low at both low and high elevations on the gravel bar, but high at middle elevations. The density increased with up to 165 days of inundation and declined gradually with more than 165 days of inundation. Density had a negative effect on crown area, whereas inundation duration had a positive effect. At lower elevations, growth limitation of S. gracilistyla is mainly caused by inundation stress, whereas at higher elevations it seems to be primarily due to drought stress, although it depends on the total duration of inundation in a year (TDIY). Consequently, the density is highest at middle elevations where trees do not become too large. These results suggest that inundation duration is one factor determining the density of S. gracilistyla trees, which in turn affects the size of each tree.

Natural history, distribution, and management of Lepidium latifolium (Brassicaceae) in New England

Abstract Lepidium latifolium (perennial pepperweed) is an herbaceous perennial, native to Europe and western Asia, that is now well established at many locations in Massachusetts and Connecticut. This species is considered a major invasive species in the western United States and appears likely to become invasive in the east if left unchecked. We showed that the distribution is greater than previously documented in New England and that populations appear to be expanding. Individuals of the species can produce thousands of seeds and we found that these seeds are tolerant to many days of inundation by salt water so that dispersal by tidal and river currents is likely. In addition, populations can expand at least 2 m/yr from growth by rhizomes, and densities exceeded 50 shoots/m2 in some areas. We identified 17 species of plants that are likely impacted by the expanding populations and 23 families of arthropods associated with L. latifolium in some of these areas. In wetland habitats, repeated pulling of sho...

Rapid Nitrate Loss and Denitrification in a Temperate River Floodplain

Nitrogen (N) pollution is a problem in many large temperate zone rivers, and N retention in river channels is often small in these systems. To determine the potential for floodplains to act as N sinks during overbank flooding, we combined monitoring, denitrification assays, and experi- mental nitrate (NO3 � -N) additions to determine how the amount and form of N changed during flooding and the processes responsible for these changes in the Wisconsin River floodplain (USA). Spring flooding increased N concentrations in the floodplain to levels equal to the river. As dis- charge declined and connectivity between the river and floodplain was disrupted, total dissolved N decreased over 75% from 1.41 mg l � 1 , equivalent to source water in the Wisconsin River on 14 April 2001, to 0.34 mg l � 1 on 22 April 2001. Simultaneously NO3 � -N was attenuated almost 100% from 1.09 to 60%) of NO3 � -N mass loss was not attributable to hydrologic losses or conversion to other forms of N, suggesting that denitrification was likely responsible for most of the NO3 � -N disap- pearance. Floodplain capacity to decrease the dominant fraction of river borne N within days of inundation demonstrates that the Wisconsin River floodplain was an active N sink, that denitri- fication often drives N losses, and that enhancing connections between rivers and their floodplains may enhance overall retention and reduce N exports from large basins.

599 Flooding Effects on Stomatal Conductance and Leaf Color Vary among Genotypes of Red and Freeman Maples

We compared two putative Freeman maples [`Jeffersred', (Autumn Blaze ®) and `Indian Summer'] and five red maples [`Franksred' (Red Sunset ®), `Autumn Flame', `PNI 0268' (October Glory®), `Fairview Flame', and unnamed selection 59904] for effects of flooding on stomatal conductance. A method for quantifying changes in leaf color that occurred on flooded plants also was developed. Potted plants grown from rooted cuttings in a greenhouse were subjected to 75 days of root-zone inundation (flood treatment) or were irrigated frequently (control treatment). Across genotypes, stomatal conductance of flooded plants initially increased by about 20% and then fell to and was sustained below 50 mmol·s–1·m–2. Stomatal conductance of flooded plants of `Indian Summer' decreased to 20 mmo·s–1·m–2 after 8 days of inundation, and two of three flooded `Indian Summer' plants died during treatment. Other genotypes required at least twice this time to display a similar reduction in stomatal conductance, indicating `Indian Summer' may be particularly flood sensitive. Intensities of red, green, and blue color at a consistent interveinal position were analyzed with Visilog software by using scanned leaf images of the youngest fully expanded leaf of each plant in both treatments. A genotype × irrigation interaction existed for the ratio of green to red intensity. This method provided numerical data that corresponded well to differences among genotypes we observed visually. For example, while flooding did not alter the color of `Autumn Flame' leaves, the ratio of green to red was three times greater for controls of Autumn Blaze® than for the flooded plants of this cultivar.

Survival of Immersion and Anoxia by Larval Tiger Beetles, Cicindela togata

Abstract The sedentary terrestrial larvae of the tiger beetle, Cicindela togata, inhabit areas that are often flooded for days or weeks. We tested the ability of these larvae to survive immersion and anoxia. Maximum survival time of immersed, anoxic C. togata was 6 days at 25 C. Time to 50% mortality (LT50) in these conditions was 85.9 ± 23.5 h. Survival times were more than eight times longer than those of similarly treated larvae of Tenebrio molitor (LT50 10.1 ± 3.2 h). Similar or somewhat longer survival times were observed in larvae of C. togata exposed to an anoxic nitrogen atmosphere (LT50 102 ± 31 h) and of T. molitor (LT5014.4 ± 6.5 h). At 10 C, LT50 of C. togata in anoxic atmospheres exceeded 10 days. Tiger beetle larvae are physiologically capable of surviving several days of inundation during floods without mechanisms to prevent burrow flooding. By entering a quiescent state, C. togata larvae survive much longer periods of anoxia than has been previously reported for terrestrial insect larvae.

Flooding frequency and invertebrate emergence from dry floodplain sediments of the river murray, Australia

AbstractRegulation of lowland rivers often alienates large areas of the floodplain, altering the natural regime of flooding frequency, duration, and magnitude. The extent to which such changes alter the productivity of river‐floodplain ecosystems and the contribution of aquatic invertebrates emerging from dry floodplain sediments is unknown. To examine this in a section of the River Murray in South Australia, fourteen replicate sods of dry sediment collected from four areas of the floodplain that had experienced different average flood recurrence frequencies (annually, 1 in 7, 1 in 11, and 1 in 22 years) were inundated in the laboratory, simulating flooding. Invertebrates emerging from the dry sediments were sampled with replacement 1, 2, 3, 7, 10, 14, 21, and 28 days after inundation, enabling comparisons of temporal changes in faunal composition and biomass. The greatest biomass and numbers of invertebrates emerged from annually‐flooded sods whereas sediments usually flooded once in 22 years yielded only protozoans. Large numbers of cladocerans and rotifers were recorded within two days of inundation whereas ostracods were not numerous until two weeks later. Heterogeneity in faunal composition and biomass among replicates probably reflected patchiness in microtopography and resting stage settlement, and variable hatching ‘strategies’. Although experimental conditions rapidly diverged from the natural situation over time because of the unrealistic constraints of enclosure, results suggest a potentially significant contribution by emergent invertebrates to the newly‐inundated floodplain foodweb. Reducing floodplain inundation frequency through regulation and flood mitigation probably severely reduces this reserve, removing a food resource for young fish and other predators.