Cattail Litter Research Articles

TROPHIC INTERACTIONS AMONG DETRITUS, BENTHIC MIDGES, AND PREDATORY FISH IN A FRESHWATER MARSH

I conducted field experiments in a western New York marsh to quantify concurrently the impacts of resource limitation and predation on benthic midge populations (Chironomus plumosus, Chironomus tentans, and Glyptotendipes barbipes). Biomass of cattail litter (Typha sp.), numbers of small insectivorous fish (primarily juvenile carp, Cyprinus carpio, and to a lesser extent juvenile brown bullhead, Ictalurus nebulosus), or numbers of large fish (primarily adult brown bullhead, which will consume both midges and small fish) were manipulated in mesh-walled mesocosms (1.5 × 1.5 × 1.2 m). Using core sampling, midge population responses to manipulations were monitored from early May through late August. Trophic responses of marsh midges to resources and predation changed temporally over the summer. In June, neither resource limitation nor predation by fish significantly influenced midge numbers. In July, after juvenile carp and brown bullhead first became abundant from the spawn, these small insectivorous fish significantly reduced midge larval densities. At that time, midge densities still did not respond to variable detritus supplies. By August, both predation by small fish and available supplies of cattail litter significantly affected midge numbers. Because midges did not respond to a nonnutritive mimic of cattail litter, it suggests that resource limitation of midge abundance was nutritionally based. Feeding by large adult bullhead had no apparent direct or indirect influence on midge densities in any month. Small fish largely disappeared from the study habitats by August, but populations of midge larvae did not rebound because they had stopped breeding for that year. This study supports emerging concepts on the integrated influences of top-down and bottom-up trophic interaction on food web function. Predation and resource limitation were simultaneously influencing midge abundance. Results also emphasize how life history phenologies of predators and prey can contribute to temporal variation in food web structure and function.

Effects of sediment load on various stages in the life and death of cattail (Typha × glauca)

We examined the effects of burial by sediment on seed germination, seedling survival, growth of adults, and litter decomposition of cattail (Typha × glauca). Seed germination and seedling survival were studied in the greenhouse, while adult plant growth and litter decomposition were studied outdoors in 3-m-diameter experimental tanks (mesocosms) at the Iowa State University Experimental Wetlands Complex near Ames, IA. The effect of burial on litter decomposition was also examined in the field at the Des Plaines River Wetlands Demonstration Project near Wadsworth, IL. Seed germination was decreased by 60–90% when sediment loads of 0.2 to 0.4 cm were applied to the surface of the soil. Seedling survivorship increased with increasing age and size of seedlings and decreased as sediment load increased from 0.2 to 1.0 cm. Sediment loads of 0, 1, 2, or 4 cm had no effect on adult plant density, number of leaves produced per plant, or leaf photosynthetic characteristics of plants grown in the mesocosms. Burial by sediment led to an initial decline in rate of cattail litter decay, for two months, but thereafter, rates for buried and unburied litter were similar. Small amounts of sediment had large effects on seed germination and growth of small seedlings, but adult plants and litter decomposition were largely unaffected by sediment.

Responses by macroinvertebrates to cattail litter quality and timing of litter submergence in a Northern Prairie Marsh

An experiment was conducted in the Delta Marsh in south-central Manitoba to assess the effects of initial litter quality, duration of litter submergence, and season of submergence on invertebrate abundance and biomass. Samples of two types of hybrid cattail (Typha glauca) litter were added to the marsh throughout the spring and summer and subsequently collected at monthly intervals. Green cattail litter gathered during the preflowering stage contained higher levels of N and P than senesced litter collected from the same stand later in the year. Although the green litter contained higher nutrient levels throughout the season, there was no preference by invertebrates between the two litter types provided. There was a tendency for higher invertebrate densities, especially collectorfilterers, to be associated with litter that had been submersed longer. Examination of seasonal patterns of invertebrate functional group abundance showed scrapers with early spring peaks in abundance and biomass. Shredder populations were at peak levels slightly later in the season than scrapers. As the season progressed, shredder and scraper populations declined to relatively low levels. Collector-filterers and predators dominated the invertebrate fauna during August and September.