Robert L. Simpson

Ecology of Soil Seed Banks

Examines factors influencing seed-bank dynamics and the variety of patterns found among different species. Topics include: the relationship of seed banks to vegetation dynamics; processes that influence inputs and losses from seed banks; and the role and importance of seed banks in vegetable types.

The Ecology of Freshwater Tidal Wetlands

ties of less than one percent, but insufficient flow to dampen upstream tidal movement. Odum et al. (1979) conservatively estimate that there are 500,0001,000,000 ha of freshwater tidal wetlands along the Atlantic and Gulf Coasts, of which 100,000-140,000 ha are in New Jersey. Almost all of the major East Coast cities from Trenton, NJ, to Richmond, VA, are near freshwater tidal wetlands. Consequently, these wetlands are greatly affected by human activities. Our discussion of the structure, function, and value of freshwater tidal wetlands is based on studies of three Delaware River wetlands: the Hamilton Marsh near Trenton, NJ, Woodbury Creek Marsh south of Camden, NJ, and Tinicum Marsh near Philadelphia, PA. In freshwater tidal wetlands the major system components-producers, consumers, detritus, sediment, and nutrients-are coupled by biological and physical processes that transfer materials and energy (Figure 1). Materials, such as organic matter, nutrients, heavy metals, and sediment, enter freshwater tidal wetlands from sources including the atmosphere, tides, point-source effluents, non-point-source runoff, groundwater, and consumer immigration. Outputs are via the atmosphere, tides, and consumer emigration. Along the urbanized upper Delaware River estuary, tidal waters provide the most important inputs, although point-source effluent and non-point-source runoff may locally contribute significant quantities of nutrients and heavy metals (Walton and Patrick 1973). Wetland function is ultimately controlled by climate, but hydrologic parameters such as duration and frequency of inundation, and the velocity and source of the water determine the physical and chemical properties of wetland substrates (Gosselink and Turner 1978). In turn, substrate characteristics dictate specific ecosystem responses, including primary production, species diversity, decomposition, and uptake and release of nutrients.

The relationship between aboveground and belowground biomass of freshwater tidal wetland macrophytes

Abstract Aboveground and belowground biomass relationships of 15 annual and perennial freshwater tidal wetland macrophytes were examined. The data showed that regression equations may be used with confidence to estimate belowground biomass from aboveground biomass for most species. The linear regression model was suitable except for one species which had a large belowground component and for which the exponential model was more appropriate. Belowground: aboveground biomass ratios were significantly different for the 8 annual species examined. At peak biomass, all annuals allocated less than one third of the total net annual production into belowground structures. They exhibited distinct seasonal patterns of biomass allocation with more biomass incorporated into belowground components during the early part of the growing season. Perennial species exhibited 4 patterns of biomass allocation with Peltandra virginica (L.) Kunth having a significantly greater mean belowground: aboveground biomass ratio than other perennials. Factors that may control biomass allocation patterns include depth of rooting and life history strategies.

Growth, Mortality, and Biomass Partitioning in Freshwater Tidal Wetland Populations of Wild Rice (Zizania aquatica var. aquatica)

WHIGHAMI, D., and R. SIMPSON. (Biol. Dept., Rider Coll., Lawreniceville, New Jersey, 08648). Growtth, mortality, aiid bioiiiass partitioiiliig in freshlwater tidal wetland populatioiis of wild lice (Zizania aquatica var. aqutatica). Bull. Toirey Bot. Club 104: 347-351. 1977.-Wild rice is a common aniiual in Delawaare River tidal wetlands. Net productioln wvas as high as 20.9 g m-2 day-1 amid varied seasonially. The lowest productioii rates occurred duriiig the seedling phenophase ancd the highest followed seedling establishmenit. On a percenitage basis, more biomass was allocated inito root productioii during the seedling phemiophase. Populationi mortality was coiistanit betweeni May and early August.

The Distribution of Seeds, Seedlings, and Established Plants of Arrow Arum (Peltandra virginica (L.) Kunth) in a Freshwater Tidal Wetland

WHIGHAM, D.,1 R. SIMPSON,2 and M. LECK.2 (1 Chesapeake Bay Center for Eiivironmeiital Studies, Smithsonian Inst., P.O. Box 28, Edgewater, MD 21037 and 2 Biol. Dept., Rider Coll., Lawrenceville, NJ 08648). The distribution of seeds, seedlings, and established plants of arrow arum (Peltandra virginica (L.) Kunth) in a freshwater tidal wetland. Bull. Torrey Bot. Club 106: 193-199. 1979.-Arrow arumn is a widely distributed perennial in Delaware River freshwater tidal wetlands. The disjunct distribution of established arrow arum plants and the rather cosmopolitan distribution of seeds within the Hamilton Marsh freshwater tidal wetland suggests that factors which determine where seedlings become established are most important in colitrolling its population structure. Established plants were absent and seed mortality was high on stream banks, which suggests that water velocity may limit seedling establishment. The almost complete absence of arrow arum from all but the littoral fringe of ponds suggests that light is also an important factor in limiting the establishment of seedlings. Buried seed studies showed that the seeds were distributed throughout the wetland, but that densities were greatest on the high marsh. Allelopathy may be an imnportant factor in controlling seed germination.

Freshwater Wetlands: Ecological Processes and Management Potential.

Freshwater wetlands: ecological processes and management potential , Freshwater wetlands: ecological processes and management potential , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی