Hydrochory and Regeneration in A Bald Cypress‐Water Tupelo Swamp Forest

Abstract

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.

Interannual variation in rainfall, drought stress and seedling mortality may mediate monodominance in tropical flooded forests

“…In temperate fioodplain forests, seedling density and survival were greater in elevated microsites (Jones et al 1994). Similarly, seed deposition and germination of temperate bottomland and tropical swamp species was greater in elevated sites such as stumps, logs or mounded soils than in depressions (Schneider and Sharitz 1988;Imbert et al 2000). These observations suggest that debris accumulation, sediment deposition, erosion or any other processes that change elevation, if only by centimeters, may have substantial effects on the plant community.…”

“…Finally, hydrochory, the common mode of seed dispersal for many SFF species, may be advantageous in habitats that experience seasonal flooding as floating seeds are deposited in elevated sites (Schneider and Sharitz 1988;Williamson and Costa 2000). Nevertheless, hydrochory could also reduce establishment success as prolonged flotation might hinder germination and survival through anoxic conditions and depletion of seed reserves (Lopez 2001).…”

Wind and Water Dispersal of Wetland Plants Across Fragmented Landscapes

“…The importance of hydrochory as a vector in wetland habitats was also demonstrated for a forested floodplain in USA by Schneider and Sharitz (1988), who found that 10-100 times as many cypress seeds and tupelo fruits were transported into each plot by water as by wind dispersal alone. Similarly, Jansson and others (2005) showed that along a Swedish river, 36-58% more species colonized flooded plots (subjected to hydrochory) than unflooded plots that were only subjected to anemochory and zoochory.…”

“…It should be noted that both temporal and permanent seed capture probability parameters were not species-specific in our hydrochorous dispersal model. Seed size or shape might affect deposition probability (see Schneider and Sharitz 1988), and therefore dispersal experiments with different seed types should be performed to improve parameterization. Furthermore, considering the sensitivity of modelled dispersal to permanent capture probability, a reliable way to assess this parameter should be found.…”

Consequences of propagule dispersal and river fragmentation for riparian plant community diversity and turnover

“…Levine (2003) noted that most patches along a river in California were colonized by propagules from sources within only 100 m upstream. Structurally complex rivers (such as the Vindel River) are efficient at trapping water-dispersed seeds along hydraulically complex reaches and areas with many emergent objects (e.g., cobbles and plant stems; Schneider and Sharitz 1988, Nilsson et al 1991b, Merritt and Wohl 2002, Gurnell et al 2007). Areas of high propagule trapping efficiency have been associated with more species-rich plant communities both in simulations (Merritt and Wohl 2002) and in field experiments (Andersson et al 2000b).…”