Mary Allessio Leck

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.

Germination of macrophytes from a Delaware River tidal freshwater wetland

LECK, M. A. (Biology Department, Rider University, Lawrenceville, NJ 08648). Germination of macrophytes from a Delaware River tidal freshwater wetland. Bull. Torrey Bot. Club 123: 48-67. 1996. The effects of burial and soil moisture (seeds were on the surface, or buried at 1 and 5 cm with drained, saturated, or flooded water levels), inundation (Petri dishes, and open and closed jars), and storage (-0 and -100% RH), as well as of light and various temperature regimes, were examined. Focus was on ten species (Amaranthus cannabinus (L.) Sauer, Ambrosia trifida L., Bidens laevis (L.) BSP, Impatiens capensis Meerb., Peltandra virginica (L.) Schott. & Endl., Phalaris arundinacea L., Pilea pumila (L.) A. Gray, Polvgonum arifblium L., Polygonum punctatum Elliott, and Sagittaria latifolia Willd.); five others were also considered to a limited extent (Alisma subcordatum Raf., Carex lurida Wahlenb., Cicuta maculata L., Cuscuta gronovii Willd., and Pontederia cordata L.). Species varied in their germination responses. Those with the same seed bank strategy (transient or persistent) had different dormancy mechanisms although seeds with persistent seed banks required temperatures >50C and germination for most was enhanced by light. Responises to burial and moisture level showed that larger seeded species were able to germinate from greater depth, but germination was greater in drained samples. There were three types of responses to inundation: (1) requirement for at least modest amounts of oxygen, (2) requirement for hypoxic conditions, and (3) those having good germination regardless of inundation regime. Seed bank losses and relatively short seed bank longevity could be accounted for by germination following afterripening, adverse effects of prolonged inundation, failed gerrnination (e.g., germination at depths that preclude the seedling from reaching the surface), and predation. Differences between the seed characteristics of species of this and those of other wetlands relate to the transient nature of the seed bank and to wetland hydrology. Variable responses to drying have implications for wetland restoration projects.

Seed-bank and vegetation development in a created tidal freshwater wetland on the Delaware River, Trenton, New Jersey, USA

The initial stages of seed-bank and vegetation development were documented in a newly created tidal freshwater wetland where donor soils were not applied. The 32.3-ha site adjacent to the Delaware River in New Jersey, USA was completed in stages from November 1993 to November 1994. Objectives of the study were to determine characteristics of the seed bank and vegetation and to monitor spatial and temporal changes. The study was carried out from 1995 to 1999 using three sites (North, East, and South Marshes) and three elevation locations (1 m from a tidal channel, midpoint, and 1 m from the upland edge). Development of the seed bank and vegetation demonstrated tremendous colonization potential derived from regional and local sources. Colonization and complete plant cover occurred within one year, and subsequent changes were rapid. Individual species behaved uniquely regarding colonization time, duration, and decline in both the seed bank and vegetation. Large seed banks of some species were present even after decline in the vegetation. Overall, the seed bank was large, small-seeded and persistent, and diverse. A total of 177 species occurred in soil seed bank and 92 in field vegetation samples, with 72 contributing to cover. Seedbank densities (mean 6 SE/m2) ranged from 450 6 152 to 394,600 6 29,950. Species richness (species/ sample) ranged from 3.3 6 1.2 to 32.3 6 1.8. Density and species richness were clearly reduced by inundation and were lowest in channel edge samples and in the first year (1995). Cover species richness ranged from 1.6 6 0.2 to 7.3 6 0.6 per quadrat. Complexity of the vegetation increased over time, with lowest diversity along the channels. The 1995 site differences, with greatest densities and species richness in the East Marsh, could be related to site history (timing of construction). Species similarity between the seed bank and vegetation ranged from 11 to 53 % and showed no site, location, or temporal pattern. However, similarity between sites of the seed bank and vegetation increased from 1995 to 1998. Several New Jersey State rare or threatened species, as well as invasive species, were present. Results indicated that it is ecologically feasible to create a wetland adjacent to a tidal freshwater river without use of donor soil and that transplantation had not been necessary.The initial stages of seed-bank and vegetation development were documented in a newly created tidal freshwater wetland where donor soils were not applied. The 32.3-ha site adjacent to the Delaware River in New Jersey, USA was completed in stages from November 1993 to November 1994. Objectives of the study were to determine characteristics of the seed bank and vegetation and to monitor spatial and temporal changes. The study was carried out from 1995 to 1999 using three sites (North, East, and South Marshes) and three elevation locations (1 m from a tidal channel, midpoint, and 1 m from the upland edge). Development of the seed bank and vegetation demonstrated tremendous colonization potential derived from regional and local sources. Colonization and complete plant cover occurred within one year, and subsequent changes were rapid. Individual species behaved uniquely regarding colonization time, duration, and decline in both the seed bank and vegetation. Large seed banks of some species were present even after decline in the vegetation. Overall, the seed bank was large, small-seeded and persistent, and diverse. A total of 177 species occurred in soil seed bank and 92 in field vegetation samples, with 72 contributing to cover. Seedbank densities (mean±SE/m2) ranged from 450±152 to 394,600±29,950. Species richness (species/ sample) ranged from 3.3±1.2 to 32.3±1.8. Density and species richness were clearly reduced by inundation and were lowest in channel edge samples and in the first year (1995). Cover species richness ranged from 1.6±0.2 to 7.3±0.6 per quadrat. Complexity of the vegetation increased over time, with lowest diversity along the channels. The 1995 site differences, with greatest densities and species richness in the East Marsh, could be related to site history (timing of construction). Species similarity between the seed bank and vegetation ranged from 11 to 53% and showed no site, location, or temporal pattern. However, similarity between sites of the seed bank and vegetation increased from 1995 to 1998. Several New Jersey State rare or threatened species, as well as invasive species, were present. Results indicated that it is ecologically feasible to create a wetland adjacent to a tidal freshwater river without use of donor soil and that transplantation had not been necessary.

A ten-year seed bank study of old field succession in central New Jersey

LECK, M. A. (Biology Department, Rider University, Lawrenceville NJ, 08648) AND C. F LECK (Graduate Program in Ecology and Evolution, Cook College, Rutgers University, New Brunswick, NJ, 08903). A ten-year seed bank study of old field succession in central New Jersey. J. Torrey Bot. Soc. 125:11-32. 1998.-Seed bank and vegetation dynamics of a newly abandoned agricultural field were studied for a decade (1984-1994). Seed bank densities ranged from 3540 m-2 (yr 1) to 50,182 m-2 (yr 3), and species richness from 26 (yr 1) to 39 species (yr 7). Over the decade 55 taxa occurred in seed bank samples and 61 species in field quadrats. (The entire 15 ha field had 181 species of which only 67 were added after the first year. Four other species occurred only in seed bank samples). Of the 55 seed bank taxa, 15 made up 81 to 95% of the seed bank; of these, the most common were Aster pilosus, Conyza canadensis, Juncus spp., Lobelia inflata, Setaria faberi, and Veronica peregrina, which were 72% of the total. Densities of individual species varied significantly over the decade and with depth (0-3, 3-6, and 6-9 cm). Elimination of seed rain using exclosures maintained for one year caused a significant decrease in both seed bank density and species richness. Comparisons of seed bank species composition with the field vegetation showed divergence after the first year. Patterns of species importance (relative frequency) in the seed bank and in the vegetation varied over time. Importance of particular growth forms also varied with stage: in the seed bank the proportion of annual and perennial species remained similar, while in the vegetation, annual species declined as perennial and woody species increased. Exotic species were an important component of the seed bank (29.0 + 0.9%), vegetation (26.4 + 1.2%), and combined flora (37.7 + 3.1%). Seed bank dynamics and vegetation dynamics of early old field species were not similar, nor did seed bank patterns and life history strategies appear related.

Tidal freshwater wetland zonation: seed and seedling dynamics

Abstract Zonation patterns of seed rain (input), persistent seed bank (seeds persisting for 1 year or longer), field seedlings, and seed production were studied in a New Jersey tidal freshwater wetland along transects extending from a tidal stream bank 30 m into the high marsh. Species diversity was highest along the stream channel and lowest at the farthest high marsh sites. Seed rain and persistent seed bank densities were similar across the transect. Although species composition varied considerably among life history categories, generally field seedlings mirrored the species composition of the seed rain. Seed rain, seed bank, seedlings observed in the field, and seed production patterns varied between species, across sites for a species, and between years. Sites varied in the proportion of estimated seed production represented as seedlings either in greenhouse (5–99%) or field (2–24%) samples. Tidal transport influenced dispersal of seeds and the persistent seed bank.

GERMINATION IN BARROW, ALASKA, TUNDRA SOIL CORES

Soil cores, collected at Barrow, Alaska, in 1972, were frozen for 6 yr and then placed in a growth chamber or greenhouse. Chrysosplenium tetrandrum (Saxifragaceae) seedlings, 204.8 m-2 in the growth chamber and 39.2 m-2 in the greenhouse, were recorded. Distribution of seeds was patchy with 25 of 36 surface (0 to 8 cm) cores yielding no seedlings. No seedlings appeared in subsurface (8 to 16 cm) cores. In addition to these seedlings, six species of mosses, fruiting bodies of two species of fungi, and several algae were observed. Germination of C. tetrandrum seeds collected from growth chamber plants showed

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.

Vascular plants of a Delaware River tidal freshwater wetland and adjacent terrestrial areas: Seed bank and vegetation comparisons of reference and constructed marshes and annotated species list1

Abstract Leck, M. A. (Dept. Biol., Rider Univ., Lawrenceville, NJ 08648) and C. F. Leck (Dept. Ecol. & Evol. Biol., Cook College, Rutgers Univ., New Brunswick, NJ 08901). Vascular plants of a Delaware River tidal freshwater wetland and adjacent terrestrial areas: Seed bank and vegetation comparisons of reference and constructed marshes and annotated species list. J. Torrey Bot. Soc. 132: 323–354. 2005.—Constructed wetland soil samples contained many more species with densities > 100 seeds / m2 than reference marsh ones (102 vs. 28); constructed wetland densities for many species were considerably higher and richness (species / sample) were > 2× greater than the reference marsh. Of the total 218 seed bank species, 60 were common to both and 34 occurred only in reference marsh samples. Numbers of cover species were similar, but composition differed. Invasive species, notably Lythrum salicaria, Phalaris arundinacea, and Phragmites australis, were more important in constructed wetland soil samples and vegetation. Non-native species comprised 9 % and 13 % of the reference marsh and constructed wetland seed bank species and 8 % and 12 % of the cover species, respectively. Variable dispersal patterns and in situ seed production contributed to these differences. Over the entire study area (wetlands and adjacent terrestrial areas) we recorded 875 species, representing 141 families, more than doubling the number observed in a 1988 report. The families having the most species were Asteraceae (103 species), Poaceae (100), and Cyperaceae (83). The largest genera were Carex (46) and Polygonum (19); seven other genera also had ≥ 10 species. Nine species were pseudo-viviparous, producing plantlets on inflorescences. Non-native species comprised 27 % of the total flora. Overall there were 37 NJ rare / endangered species for the entire area; 11 occurred only in the constructed wetland with constructed wetland soil samples containing more than the reference marsh samples (8 vs. 1). Available lists from 1824, 1887, and 1964/65 and five species known only from herbarium specimens indicate that several species have been extirpated since the 19th C. Anthropogenic influences continue to have impact on diversity.

Germination ecology of Bidens laevis (Asteraceae) from a tidal freshwater wetland1

LECK, M. A. (Department of Biology, Rider College, Lawrenceville, NJ 08648-3599), C. C. BASKIN AND J. M. BAsKiN (School of Biological Sciences, University of Kentucky, Lexington, KY 40506-0225). Germination ecology of Bidens laevis (Asteraceae) from a tidal freshwater wetland. Bull. Torrey Bot. Club 121: 230-239. 1994.-Eight or more weeks of cold stratification (5?C) were required to break dormancy in achenes of Bidens laevis (L.) BSP from a tidal freshwater wetland. When achenes began to come out of dormancy, they germinated to 50% first at 35/20?C, and then with additional stratification the minimum temperature for 50% germination decreased to 1 5/6?C. Germination of stratified achenes was inhibited by darkness and was completely prevented by hypoxia (inundation in closedjars). Seeds inundated in openjars and those in Petri dishes, however, germinated to > 80%. Germination declined sharply with depth of burial (0, 1, and 5 cm). Moisture regime (drained, saturated, and inundated) also significantly affected germination, but afterripening condition (cold greenhouse or 5?C) altered the effect. Interaction between depth of burial and moisture regime was significant (P 1 yr) following winter afterripening of achenes in the field.