JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. The importance of hydrochory, or seed dispersal by water, to the regeneration of Taxodium distichum (bald cypress) and Nyssa aquatica (water tupelo) was examined in a forested floodplain of the Savannah River in South Carolina. Seedfall and dispersal by water were quantified for 2 yr using floating seed traps. Water depth, surface velocity, and flow direction were monitored over the same period.Seedfall for bald cypress and water tupelo occurred primarily from early fall throughout the winter, when water levels were rising in the swamp. Extended buoyancy periods for newly released seeds and fruits (bald cypress: 42 + 37 d; water tupelo: 85 ? 36 d) prolonged dispersal for both species. Flowing water transported experimentally released seeds long distances, but in a uniform direction, and concentrated them nonrandomly against logs, trees, knees, and other emergent substrates. An examination of the soil seed banks in five microsite types supported the results of the seed transport study. Lowest woody seed densities occurred in the open areas, and highest seed densities occurred in sediments adjacent to emergent substrates such as logs. Additionally, elevated water levels of 1-2 m caused by short-term, high-discharge floods scoured seeds of Nyssa sylvatica var. biflora, Quercus spp., Liquidambar styraciflua, Pinus taeda, and other species from adjacent bottomland hardwood communities and transported them into the bald cypress-water tupelo forest.We conclude that elevated water levels, which occur during late fall when seeds are released, influence the distribution of bald cypress and water tupelo seeds and their availability for recruitment. Short-term, deeper floods may also be important for seed transport among bottomland hardwood communities that are spatially separated or differ in species composition.

It has been hypothesized that periodically flooded forests have higher rates of aboveground net primary production than upland forests and near‐continuously flooded forests, but a competing hypothesis holds that the benefits of periodic inputs of nutrients and water may be diminished by stresses associated with anaerobic soils or drought. To test these hypotheses, we measured groundwater table depths and aboveground productivity in floodplain forests of South Carolina and Louisiana. We established paired plots on locally dry, intermediate, and wet topographic positions across three hydrologic transects in each state. These plots encompassed upland hardwood, bottomland hardwood, and cypress swamp forests. Measurements of leaf litterfall, wood production, and groundwater table depth were made in 1987 and 1988. We then used mean growing‐season water depth (MWD) to group the plots into three classes: wet (>0 cm), intermediate (0 to −60 cm), and dry (<−60 cm). Aboveground net primary production (NPP) on wet plots (2‐yr mean ± 1 sd = 675 ± 271 g·m−2·yr−1) was significantly lower than on intermediate and dry plots (P ≤ 0.02). There was no significant difference between intermediate and dry plots (107 ± 189 and 1038 ± 91) g·m−2·yr−1, respectively). In addition, aboveground NPP on intermediate plots was not significantly different from 22 temperate upland forests in the literature. Combining our data with data from the literature, we found that aboveground NPP on wet plots was negatively related to MWD with a slope of −5 g·m−2·yr−1·cm−1. On sites with evidence of hydrologic disturbance (>25% dead stems) the slope of this line was 5 times greater (−24 g·m−2·yr−1·cm−1). We conclude that the subsidy–stress hypothesis does not adequately describe patterns of NPP across Southeastern U.S. floodplain forests. Conditions of periodic flooding and flowing water do not often lead to high rates of productivity compared with upland forests. However, extensive flooding is nearly always a significant stress on forest productivity, particularly when the flooding regime has been recently perturbed through levee construction or impoundment. Our data support a more complex interaction between subsidy and stress factors.

Between 1987 and 1990, we estimated seedfall and recorded age, growth, and survival of 10 933 tree and vine seedlings growing in the understories of four bottomland hardwood forests in South Carolina. The forests differed in flood frequency, soils, and vegetation structure but had a number of woody plant species in common.Several demographic processes were consistent for all four forests as well as for floodplain forests described in other published studies. Smaller seeded species had larger numbers of seeds dispersed, germinants, and established seedlings. Seed size, however, was not clearly related to seedling survival. Published rankings of shade and flood tolerances were also unrelated to survival, at least during the first growing season after germination. Seedling survival rates were least during the first growing season and greater in subsequent years. Within a growing season, early germinants had greater survival. For some species, survival was negatively related to basal area of neighboring conspecific adult trees.Some aspects of the regeneration process were more site specific. Within species, seedfall densities relative to adult tree abundance differed across forests by an order of magnitude.First-year seedling mortality rates were significantly affected by site and site x species interactions. Mortality in subsequent years was also significantly affected by site. Although the role of flooding in site-specific mortality was not clear, small elevation changes within flooded sites were correlated with changes in germination and survival for some species.

Hurricane Hugo caused much damage to the old-growth forests of the Congaree Swamp National Monument, but most of the damage to trees >20 cm dbh consisted of crown breakage and defoliation. Serious damage (>25% of crown lost, snapped trunk, or uprooted) was more common in mixed bottomland forest (49% of trees seriously damaged) than in adjacent sloughs dominated by Taxodiumdistichum (L.) L.C. Rich, and Nyssaaquatica L. (19% of trees seriously damaged). Of the trees >20 cm dbh, about 12% were uprooted in the bottomland forest, whereas only 2% were uprooted in sloughs. The storm reduced diversity in sloughs because most trees of species characteristic of better drained sites, and especially those rooted on nurse logs and other unstable elevated microsites, were uprooted. Dynamics of the entire forest were greatly influenced by the capacity of most tree species to recover vegetatively after suffering even severe crown and stem damage. Trees with resprouted crowns, however, were particularly likely to be broken, presumably owing to the presence of stem rots and architecturally unsound branching patterns.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. We compared growth and biomass allocation patterns of Lonicerajaponica, an invasive vine in the southeastern United States, and its native congener, L. sempervirens, among three herbivory treatments. Growth and biomass variables were calculated at nine harvest dates across 14 mo under no herbivory, insect herbivory, and mammal and insect herbivory. In the absence of herbivory, L. sempervirens accumulated greater biomass and had higher growth rates than L. japonica. Lonicera sempervirens, however, experienced more herbivore damage than L. japonica, particularly due to the combined effects of insect and mammal herbivory. Total biomass accumulation and greater allocation to leaves and stems indicate a compensatory response to herbivory by L. japonica. These attributes in response to herbivory coupled with lower herbivory in its new range compared to L. sempervirens could give L. japonica a substantial advantage over its native congener.