Stands Of Emergent Vegetation Research Articles

Relationships Between Shoreline Development and Nest Site Selection by Black Crappie and Largemouth Bass

AbstractTo evaluate potential effects of lakeshore development on nest site selection, we compared locations of black crappie Pomoxis nigromaculatus and largemouth bass Micropterus salmoides nests in three Minnesota lakes with available habitat in the littoral and riparian zones and the presence or absence of developed shoreline. We used binomial logistic regression to determine how the frequency of nest sites varied among lakes and with the presence or absence of five habitat variables. Black crappies in all three lakes were more likely to nest adjacent to undeveloped shoreline. Black crappies were also more likely to nest in stands of emergent vegetation, particularly hardstem bulrush Scirpus acutus. Largemouth bass were more likely to nest near undeveloped shoreline but were less dependent on hardstem bulrush. Shoreline development has the potential to alter nest site selection by largemouth bass and, particularly, by black crappies.

The river‐bed: a dynamic store for plant propagules?

AbstractThis paper investigates temporal variations in the abundance, species composition and richness, and spatial distribution of plant propagules stored on river‐beds.Samples of the surface layers of river‐bed sediments were obtained from two reaches of the River Frome, Dorset, UK, and one reach of the River Tern, Shropshire, UK. Samples were taken from the same bed locations on four occasions spaced at approximately four monthly intervals. Following greenhouse germination trials, 11 384 viable propagules of 105 species were identified in 192 channel bed samples. On average, 32% of the species found in the propagule samples were not present in the channel and riparian vegetation. Most of these additional species were wetland and terrestrial rather than aquatic species. The number of species and density of propagules stored on the river‐bed varied through time and between reaches. These findings indicate that the channel bed is a dynamic store for viable propagules, including a large proportion of species that are not found locally. These propagules are available for redistribution across river‐banks and floodplains during high river flows.Propagules were preferentially stored within particular bed habitats. On the Tern, the most retentive habitats were close to the channel margins and adjacent to riparian vegetation and trees. On the Frome, stands of emergent vegetation along the channel margin were the most retentive habitat, and were also associated with trapping of finer sediment and organic matter. This habitat provides an aggrading environment at the bank toe that could potentially offer germination sites for the non‐aquatic propagules that are stored. Germination and growth of wetland and terrestrial plants during bank profile aggradation and lateral extension would provide root reinforcement and flow resistance across the changing bank profile. The preferential accumulation of sediment and species‐rich propagules around stands of marginal emergent vegetation is indicative of a subtle coupling of geomorphological and ecological systems. Copyright © 2007 John Wiley & Sons, Ltd.

Experimental Study of Bed Load Transport through Emergent Vegetation

Vegetation is an important agent in fluvial geomorphology and sedimentary processes, through its influence on the local hydraulics that determine sediment transport. Within stands of emergent vegetation, bed shear is substantially reduced through the absorption of momentum by drag on the stems. This stimulates deposition of sediment and reduces capacity for bed load transport. The effect of emergent vegetation on hydraulic parameters (including equilibrium bed gradient, flow depth, and velocity) and on bed load transport rate has been investigated experimentally for one sediment size, stem diameter, and stem spacing. Bed load transport rate was found to be closely related to bed-shear stress, which must be estimated by partitioning total flow resistance between stem drag and bed shear.

Effects of vegetation management in constructed wetland treatment cells on water quality and mosquito production

The impact of three vegetation management strategies on wetland treatment function and mosquito production was assessed in eight free water surface wetland test cells in southern California during 1998–1999. The effectiveness of the strategies to limit bulrush Schoenoplectus californicus culm density within the cells was also investigated. Removing accumulated emergent biomass and physically limiting the area in which vegetation could reestablish, significantly improved the ammonia–nitrogen removal efficiency of the wetland cells, which received an ammonia-dominated municipal wastewater effluent (average loading rate=9.88 kg/ha per day NH 4-N). We determined that interspersing open water with emergent vegetation is critical for maintaining the wetland's treatment capability, particularly for systems high in NH 4-N. Burning aboveground plant parts and thinning rhizomes only temporarily curtailed vegetation proliferation in shallow zones, whereas creating hummocks surrounded by deeper water successfully restricted the emergent vegetation to the shallower hummock areas. Since the hummock configuration kept open water areas interspersed throughout the stands of emergent vegetation, the strategy was also effective in reducing mosquito production. Decreasing vegetation biomass reduced mosquito refuge areas while increasing mosquito predator habitat. Therefore, the combined goals of water quality improvement and mosquito management were achieved by managing the spatial pattern of emergent vegetation to mimic an early successional growth stage, i.e. actively growing plants interspersed with open water.

Effects of Muskrat (Ondatra zibethicus) Lodge Construction on Invertebrate Communities in a Great Lakes Coastal Wetland

Abstract Muskrat (Ondatra zibethicus) herbivory and lodge construction create open water areas in stands of emergent vegetation. This study examined how aquatic invertebrates are affected by changes in the physical structure of plant stands created by muskrats. We compared density, species composition and functional feeding groups of benthic macroinvertebrate communities and abiotic conditions in open water areas at muskrat lodges and in adjacent cattail stands. Although total numbers of macroinvertebrates were not affected by muskrat activities, communities at muskrat lodges were less diverse than in cattail stands. Gathering collectors such as chironomid midges that feed on fine particulate organic matter were the dominant trophic group; these were significantly more abundant at muskrat lodges than in cattail stands. Scrapers, such as gammarid scuds that feed on periphyton, were also abundant; these were significantly more abundant in cattail stands than at muskrat lodges. Water temperature, dissolved o...

Coastal wetland insect communities along a trophic gradient in Green Bay, Lake Michigan

Insects of Great Lakes coastal wetlands have received little attention in spite of their importance in food webs and sensitivity to anthropogenic stressors. We characterized insect communities from four coastal wetlands that spanned the length of a trophic gradient in Green Bay during spring and summer of 1995. We sampled flying insects using sticky traps in dense emergent, sparse emergent, and open water—submergent vegetation zones within each wetland and estimated numerical abundance, biomass (mg dry weight) and taxonomic composition. We found that insect abundance and biomass were distributed differently among vegetation zones within wetlands along the gradient during both spring and summer. Insect abundance was highest at oligotrophic Portage Marsh during spring and lowest in wetlands toward the lower (southern), eutrophic end of the bay. Biomass did not differ consistently along the trophic gradient but increased with increasing emergent vegetation cover in 3 of 4 wetlands during both seasons. Ordination revealed distinct gradients in community structure on both regional (i.e., upper, middle, and lower Green Bay) and local (vegetation zones within wetlands) scales. Wetlands sorted in order of trophic status during both seasons, primarily due to abundant small Chironomidae, such as trophic-sensitiveHeterotrissocladius changi, in middle and upper bay wetlands. Chironomidae also were a dominant component of open water-submergent assemblages in all wetlands. Lower bay wetlands were characterized by fewer but larger Chironomidae (e.g.,Chironomus spp.), as well as Ceratopogonidac, Calliphoridae, and Ephydridae, which were most abundant in stands of emergent vegetation. Our results suggest that eutrophy in the lower bay may contribute to relatively poor foraging conditions for insectivorous fish and young waterfowl during spring, and they demonstrate the utility of using insect communities to assess environmental degradation, such as excessive nutrient loading, in coastal wetlands of the Great Lakes.

Spatial and diel availability of flying insects as potential duckling food in prairie wetlands

We examined spatial and diel availability of flying insects that are a critical food resource to young ducklings. We sampled insects in three native prairie wetlands on the Woodworth Study Area of south-central North Dakota. Insects were sampled with floating sticky traps within emergent macrophyte, edge, and open water microhabitat zones. Sampling took place from 12 June to 4 July 1995, a period that coincided with peak dabbling duck (Anas spp.) hatching in this region. Our sticky trans collected 28,527 insects and spiders totaling at least 32 families and 150 species. Chironomidae (Diptera) was the most abundant group, constituting 60% of the total insect count and 32.9% of the biomass (mg dry weight). Mixed-model ANOVA showed that a population of similar undisturbed wetlands may show differences in insect availability when considering both time and space, primarily due to differences in community structure among sites. In spite of these significant random effects, interactions between or among the fixed date, zone, and trap-height effects significantly influenced insect availability. Insects stratified near the water surface in open water areas on all dates except during cool, rainy weather (28 June); on this date, insects were virtually absent from open water. Vertical stratification of insects was less prevalent within and at the edge of stands of emergent vegetation, although most insects were present in the emergent zone near the water surface during inclement weather. ANOVA models from our diel study showed that a significant diel pattern in insect availability existed among zones, but this interaction also depended upon trap-height (chironomid biomass) or date (chironomid counts and biomass). Generally, more insect numbers and biomass were captured in and along stands of emergent macrophytes during the day but chiefly in open water near the surface at night. This diel-zone effect was especially apparent for large chironomids, which were essentially absent during daylight but abundant in open water and edge zones during night. Daytime chironomids were small and predominantly trapped in stands of emergent vegetation. Our results are consistent with previously documented brood foraging behavior and may indicate a trade-off between low energy foraging in the open at night and potentially safer but less productive foraging in stands of emergent vegetation during the day.

Effects of Prolonged Flooding on Nektonic Invertebrates in Small Diked Marshes

This study examined the response by nektonic invertebrates to prolonged flooding of a series of experimental marshes in the Delta Marsh in south-central Manitoba. Prior to flooding, nektonic invertebrate densities, biomass, and numbers of taxa were at their highest levels during midsummer in open-water sites with dense submersed vegetation; during the same period, nekton levels within the experimental marshes were minimum in stands of emergent vegetation. These differences appear to be related to available habitat structure and dissolved oxygen concentrations. Flooding to 1 m above normal eliminated the submersed vegetation and existing emergent vegetation. This resulted in a single large input of litter at the time of flooding with little or no subsequent input during flooding. The herbivore–detritivore functional group reached high levels early in the first year of flooding and remained high until late in the second year of flooding. The predator–parasite group did not exhibit a similar increase following flooding. Changes in the amount of plant litter available as both food and habitat affected these changes in the nekton following flooding. Wind-induced water currents also probably had an effect on nekton distributions during the flooding period.

Niche Overlap and Habitat Use by Sympatric Duck Broods in Eastern Washington

We evaluated niche overlap and habitat use among duck broods on Turnbull National Wildlife Refuge (Turnbull NWR). During summer of 1983 and 1984, 485 observations were recorded in 46 days. Data were gathered on 320 feeding broods of 9 species along 12 niche dimensions. Mean niche overlap values ranged from 0.62 to 0.94 for 36 possible species pairs. The greatest niche separation occurred on hatching date and feeding depth dimensions. Gadwall (Anas strepera) and teal (A. discors and A. cyanoptera) broods were ecologically very similar. Both had sharp mid-season hatching peaks and fed over dense beds of submerged macrophytes. Five species of diving duck broods tended to feed in deeper water and over areas with sparse submerged macrophytes. Among diving ducks, bufflehead (Bucephala albeola) broods were ecologically distinct, feeding over sparse vegetation often far from land. Mallard (A. platyrhynchos) broods were ecologically isolated from other dabbling ducks. They fed in shallow water within stands of emergent vegetation. The niche for ring-necked duck (Aythya collaris) broods was most similar to dabbling ducks, but also showed similarities with other divers. J. WILDL. MANAGE. 52(1):95-103 Studies dealing with brood-rearing ecology often emphasize macrohabitat (Stoudt 1971, Mack and Flake 1980, Swanson et al. 1984). Multi-dimensional studies of niche and niche overlap by sympatric duck broods are lacking. However, several studies have reported temporal segregation for both adult ducks and broods. Nilsson (1970) observed species of diving ducks segregating their feeding activities by diurnal and nocturnal partitioning. Morning and evening feeding peaks have been documented for broods of various species (Hochbaum 1944, Chura 1963, Ringelman and Flake 1980). Ringelman and Flake (1980) reported some temporal differences in feeding activity between blue-winged teal and mallards in age classes I and II. Differences in hatching dates among sympatric duck species are well documented (Hochbaum 1944, Hines 1977, Toft et al. 1984). Koskimies and Lahti (1964) reported differences in low temperature tolerances for several species of ducklings. Dietary overlap has been reported for sympatric species of ducklings, especially neonates (Collias and Collias 1963, Bengtson 1971, Sugden 1973). Among older ducklings, overlap is reduced as species become morphologically (Nudds and Bowlby 1984, Nudds and Kaminski 1984) and behaviorally specialized (Collias and Collias 1963, Sugden 1973). Sugden (1973) suggested dietary overlap in ducklings may not represent competition because substantial overlap occurred only among very young broods. Collias and Collias (1963) reported that ducklings of different species tended to specialize on different invertebrates. Our study examined microhabitat use by duck broods. Our objectives were to describe quantitatively species-specific use for several spatial and temporal niche dimensions and measure niche overlap between and among species for these dimensions. We use the term brood to refer to ducklings within a accompanied by an adult hen. Thus, when we refer to habitat use we recognize that in some cases the brood-rearing hen may have selected the site. Our study was funded by the Turnbull Laboratory for Ecological Studies, Eastern Washi gton University. We are grateful to refuge personnel for their cooperation and use of equipment. Appreciation is extended to R. L. Carr and R. A. Soltero for advice and encouragement. We acknowledge J. R. Rees, R. B. Pharness, and J. R. Alldredge for their helpful suggestions. We thank D. C. Douglas, P. J. DuBowy, R. M. Kaminski, J. A. Mueth, L. W. Ratti, K. P. Reese, J. K. Ringelman, J. J. Rotella, M. W. Weller, and L. G. Sugden for careful review of the manuscript.

Survey of 13 Polk County, Florida Lakes for Mosquito (Diptera: Culicidae) and Midge (Diptera: Chironomidae) Production

A survey was conducted at 30 sites in 13 lakes in Polk County, Florida to: (1) determine the extent of mosquito and midge production in the lake sites, (2) define more precisely some of the environmental factors that influence mosquito and midge densities, and (3) determine if the physical appearance of a site would enable accurate estimates of the mosquito and midge production potential. Although the emphasis of this survey was on Coquillettidia perturbans (Walker), data were collected on the mosquitoes Anopheles, Culex, Mansonia, and Uranotaenia and the chironomid midge Glyptotendipes paripes Edwards. Results of previous studies in marshes indicate that higher numbers of Coquillettidia larvae are found in sites with (1) dense stands of emergent vegetation, (2) substrates characterized by a thick layer of detritus, (3) water depths less than 1 m, and (4) dense stands of shoreline vegetation. Production in sites with these characteristics was found to be greater than previously realized. Estimates of Coquillettidia production made at the beginning of the study were found to be correct in 20 of the 30 instances. Production potentials that were over- or under-estimated were due primarily to changes in trap locations (due to fluctuating water levels) in which dramatic changes in habitat conditions occurred. It appears that, with only cursory observation, an accurate estimate of a site's potential for mosquito and midge production can be made.

Benthic Sampling for Waterfowl Foods in Emergent Vegetation

Foods selected by dabbling ducks (Anatinae) on breeding grounds have recently been investigated to define the ecological and physiological factors that influence waterfowl production (Drobney and Fredrickson 1979, Swanson et al. 1979, Reinecke and Owen 1980). One of the major obstacles encountered in feeding ecology studies of breeding dabbling ducks has been a lack of quantitative sampling gear that will function in the seasonally flooded aquatic habitats attractive to dabbling ducks. Standard grab samplers such as the Ekman, Petersen, and Ponar will not function in highly vegetated substrates, and considerable effort is required to penetrate this type of substrate with a standard core sampler. Sampling benthic organisms in dense stands of emergent vegetation requires specialized equipment capable of rapid and deep penetration of the substrate. Greater penetration is required to compensate for the binding effect of dense root masses and rhizomes that can remove

Germination and Planting Experiments on Soft-Stem and Hard-Stem Bulrush

with the primary purpose of revegetating large open water areas with stands of emergent vegetation (Harris, 1957). As a part of this program, a considerable amount of soft-stem bulrush (Scirpus validus Vahl.) and a lesser amount of hard-stem bulrush (S. actus Muhl) seed was broadcast onto newly exposed mud flats by an airplane during midand late June. Although bulrush development was widespread on the mud flats, careful examination failed to reveal any important differences in the amount of development between seeded and unseeded areas, and it was thought that the seeding operation had made little if any contribution to the establishment of these stands. These observations led to a number of germination and seeding experiments which comprise the present report. Previous germination tests of these two species have not been carried out in connection with field operations such as experimental seeding, large scale machine harvesting, or extensive planting. Oborn (1938) subjected hard-stem bulrush seed to many different storage conditions and obtained moderate germination only with seed which had been stored under water in darkness at