The presence of viable seed in 24 substrate samples from Eagle Lake, a marsh in north-central Iowa, was tested by placing subsamples of each sample under 2 environmental conditions. One set of subsamples was placed underwater (submersed treatment). Seeds of 20 species germinated and grew in this treatment. On the average, there were 8.3 species/sample. The 2nd set of subsamples was kept moist, simulating conditions on an exposed mud flat (drawdown treatment). In the drawdown treatment, on the average, seeds of 12.9 species germinated/sample. Altogether seeds of 40 species germinated in this treatment of which only 24% were also found in the submersed treatment. By combining the results from the 2 treatments, the seed banks in the 6 vegetation types studied were estimated to range from 21,445 to 42,615 seeds/m2 on the average in the upper 5 cm of soil. Field studies at Eagle Lake (1974) and Goose Lake (1976), when these marshes had no standing water, revealed that the most abundant species whose seeds germinated on exposed mud flats were the same as the most abundant species in the experimental drawdown samples from Eagle Lake. In 1975, when Eagle Lake had standing water again, the submersed and floating species that were found were the same as those found in the experimental submersed samples from Eagle Lake. The seed-bank results and vegetation sampling reveal that there are 3 types of species present in prairie marsh seed banks: emergent species (Typha, Scirpus, Sparganium, Sagittaria) germinate on exposed mud flats or in very shallow water; submersed and free-floating species (Lemna, Spirodela, Ceratophyllum, Naias, Potamogeton) whose dormant seeds or turions can survive on exposed mud flats for a year and which germinate when there is standing water; and mud-flat species (Bidens, Cyperus, Polygonum and Rumex) which are ephemerals whose seeds can only germinate on exposed mud flats during periods when no standing water exists in the marsh because of drought or water level manipulation. When the marsh refloods, these species are eliminated from the visible marsh flora. Primarily because of the fluctuating water levels and muskrat damage, prairie marshes have cyclical changes in their vegetation during which mud-flat, emergent, or submersed and free-floating species replace each other as the dominant type of species in a marsh. Abstract. The presence of viable seed in 24 substrate samples from Eagle Lake, a marsh in northcentral Iowa, was tested by placing subsamples of each sample under 2 environmental conditions. One set of subsamples was placed underwater (submersed treatment). Seeds of 20 species germinated and grew in this treatment. On the average, there were 8.3 species/sample. The 2nd set of subsamples was kept moist, simulating conditions on an exposed mud flat (drawdown treatment). In the drawdown treatment, on the average, seeds of 12.9 species germinated/sample. Altogether seeds of 40 species germinated in this treatment of which only 24% were also found in the submersed treatment. By combi...

A qualitative model of succession in freshwater wetlands is proposed, based on the life history features of the species involved. Three key life history traits can be used to characterize wetland species: life-span, propagule longevity, and propagule establishment requirements. By combining these three life history traits, 12 basic wetland life history types are recognized. For each life history type, the future state (presence only in the form of propagules in the seed bank, presence as adult plants, or complete absence) of each species type in a wetland can be predicted if environmental conditions change. Most of the information needed to apply this model to a particular wetland can be obtained by an examination of a wetland's seed bank. Several examples of succesion in North American and African wetlands are presented to illustrate the application of the model.

Thousands of wetland restorations have been done in the glaciated mid‐continent of the United States. Wetlands in this region revegetate by natural recolonization after hydrology is restored. The floristic composition of the vegetation and seed banks of 10 restored wetlands in northern Iowa were compared to those of 10 adjacent natural wetlands to test the hypothesis that communities rapidly develop through natural recolonization. Restoration programs in the prairie pothole region assume that the efficient‐community hypothesis is true: all plant species that can become established and survive under the environmental conditions found at a site will eventually be found growing there and/or will be found in its seed bank. Three years after restoration, natural wetlands had a mean of 46 species compared to 27 species for restored wetlands. Some guilds of species have significantly fewer (e.g., sedge meadow) or more (e.g., submersed aquatics) species in restored than natural wetlands. The distribution and abundance of most species at different elevations were significantly different in natural and restored wetlands. The seed banks of restored wetlands contained fewer species and fewer seeds than those of natural wetlands. There were, however, some similarities between the vegetation of restored and natural wetlands. Emergent species richness in restored wetlands was generally similar to that in natural wetlands, although there were fewer shallow emergent species in restored wetlands. The seed banks of restored wetlands, however, were not similar to those of natural wetlands in composition, mean species richness, or mean total seed density. Submersed aquatic, wet prairie, and sedge meadow species were not present in the seed banks of restored wetlands. These patterns of recolonization seem related to dispersal ability, indicating the efficient‐community hypothesis cannot be completely accepted as a basis for restorations in the prairie pothole region.

The Florida Everglades is an oligotrophic wetland system with tree islands as one of its most prominent landscape features. Total soil phosphorus concentrations on tree islands can be 6 to 100 times greater than phosphorus levels in the surrounding marshes and sloughs, making tree islands nutrient hotspots. Several mechanisms are believed to redistribute phosphorus to tree islands: subsurface water flows generated by evapotranspiration of trees, higher deposition rates of dry fallout, deposition of guano by birds and other animals, groundwater upwelling, and bedrock mineralization by tree exudates. A conceptual model is proposed, in which the focused redistribution of limiting nutrients, especially phosphorus, onto tree islands controls their maintenance and expansion. Because of increased primary production and peat accretion rates, the redistribution of phosphorus can result in an increase in both tree island elevation and size. Human changes to hydrology have greatly decreased the number and size of tree islands in parts of the Everglades. The proposed model suggests that the preservation of existing tree islands, and ultimately of the Everglades landscape, requires the maintenance of these phosphorus redistribution mechanisms.

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