Marianne K. Burke

MIXOTROPHY AND NITROGEN UPTAKE BY PFIESTERIA PISCICIDA (DINOPHYCEAE)

The nutritional versatility of dinoflagellates is a complicating factor in identifying potential links between nutrient enrichment and the proliferation of harmful algal blooms. For example, although dinoflagellates associated with harmful algal blooms (e.g. red tides) are generally considered to be phototrophic and use inorganic nutrients such as nitrate or phosphate, many of these species also have pronounced heterotrophic capabilities either as osmotrophs or phagotrophs. Recently, the widespread occurrence of the heterotrophic toxic dinoflagellate, Pfiesteria piscicida Steidinger et Burkholder, has been documented in turbid estuarine waters. Pfiesteria piscicida has a relatively proficient grazing ability, but also has an ability to function as a phototroph by acquiring chloroplasts from algal prey, a process termed kleptoplastidy. We tested the ability of kleptoplastidic P. piscicida to take up 15N‐labeled NH, NO, urea, or glutamate. The photosynthetic activity of these cultures was verified, in part, by use of the fluorochrome, primulin, which indicated a positive relationship between photosynthetic starch production and growth irradiance. All four N substrates were taken up by P. piscicida, and the highest uptake rates were in the range cited for phytoplankton and were similar to N uptake estimates for phagotrophic P. piscicida. The demonstration of direct nutrient acquisition by kleptoplastidic P. piscicida suggests that the response of the dinoflagellate to nutrient enrichment is complex, and that the specific pathway of nutrient stimulation (e.g. indirect stimulation through enhancement of phytoplankton prey abundance vs. direct stimulation by saprotrophic nutrient uptake) may depend on P. piscicida’s nutritional state (phagotrophy vs. phototrophy).

Fine Root Productivity and Dynamics on a Forested Floodplain in South Carolina

The highly dynamic, fine root component of forested wetland ecoi&g fine root dynamics is a challenging endeavor in any system, but the dilficulties are particularly evident in forested floodplains where frequent hydrologic fluctuations directly influence fine root dynamics. Fine root (53 mm) biomass, production, and turnover were estimated for three soils exhibiting different drainage patterns within a mixedoak community on the Coosawhatchie River floodplain, Jasper County, South Carolina. Within a 45cm-deep vertical profile, 74% of total fine root biomass was restricted to the upper 15 cm of the soil surface. Fine root biomass decreased as the soil became less well drained (e.g., tine root biomass in well-drained soil > intermediately drained soil > poorly drained soil). Fine root productivity was measured for 1 yr using minirhiitrons and in situ screens. Both methods suggested higher fine root production in better drained soils but showed frequent fluctuations in fine root growth and mortality, suggesting the need for frequent sampling at short intervals (e.g., monthly) to accurately assess fine root growth and turnover. Fine root production, estimated with in situ screens, was 1.5, l-g, and 0.9 Mg ha-’ yr-’ in the well-drained, intermediately drained, and poorly drained soils, respectively. Results from minirhizotrons indicated (hat fine roots in well-drained soils grew to greater depths while fine roots in poorly drained soils were restricted to surface soils. Minimizotrons also revealed that the distribution of fine roots among morphological dasses changed between well-drained and poorly drained soils. P WETLAND ECOSYSTEMS has been the focus of numerous studies. Most commonly, productivity is estimated using aboveground parameters such as litterfall and stemwood production (B&son et al., 1980; Conner and Day, 1992; Conner et al., 1993; Conner, 1994; Megonigal et al., 1997). Many investigators have acknowledged, however, that failure to include belowground data will seriously underestimate forest ecosystem productivity (Vogt et al., 1986a; Day and Megonigal, 1993). It has been suggested that fine root production accounts for up to 75% of total net primary production (NPP) in some forests (Nadelhoffer and Raich, 1992). Similar to aboveground foliage, large amounts of fine roots die annually and can contribute a quantity of litter similar in magnitude to foliar litter (McClaugherty et al., 1984). Fine root dynamics, therefore, represent a significant source of energy and nutrient flow through forested systems, particularly for those TerreU T. Baker III, College of Agriculture and Home Economics, New Mexico State Univ., Box 30003, MSC 3AE, Las Cruces, NM 88003-8003; William H. Conner, Baruch Forest Science Institute, P.O. Box 596, Georgetown, SC 29442; B. Graeme Lockaby, School of Forestry, Auburn Univ., 108 M.W. Smith Hall, Auburn, AL 36849. 5418; John A. Stanturf, USDA-Forest Service, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneville, MS 38776; Marianne K. Burke, USDA-Forest Service, Southern Research Station Center for Forested Wetlands Research, 2730 Savannah Hwy., Charleston, SC 29414. Received 11 Mar. 1999. *Corresponding author (ttbaker@

Finding a “Disappearing” Nontimber Forest Resource: Using Grounded Visualization to Explore Urbanization Impacts on Sweetgrass Basketmaking in Greater Mt. Pleasant, South Carolina∗

Despite growing interest in urbanization and its social and ecological impacts on formerly rural areas, empirical research remains limited. Extant studies largely focus either on issues of social exclusion and enclosure or ecological change. This article uses the case of sweetgrass basketmaking in Mt. Pleasant, South Carolina, to explore the implications of urbanization, including gentrification, for the distribution and accessibility of sweetgrass, an economically important nontimber forest product (NTFP) for historically African American communities, in this rapidly growing area. We explore the usefulness of grounded visualization for research efforts that are examining the existence of “fringe ecologies” associated with NTFP. Our findings highlight the importance of integrated qualitative and quantitative analyses for revealing the complex social and ecological changes that accompany both urbanization and rural gentrification.

Vegetation, soil, and flooding relationships in a blackwater floodplain forest

Hydroperiod is considered the primary determinant of plant species distribution in temperate floodplain forests, but most studies have focused on alluvial (sediment-laden) river systems. Few studies have evaluated plant community relationships in blackwater river systems of the South Atlantic Coastal Plain of North America. In this study, we characterzied the soils, hydroperiod, and vegetation communities and evaluated relationships between the physical and chemical environment and plant community structure on the floodplain of the Coosawhatchie River, a blackwater river in South Carolina, USA. The soils were similar to previous descriptions of blackwater floodplain soils but had greater soil N and P availability, substantially greater clay content, and lower soil silt content than was previously reported for other blackwater river floodplains. Results of a cluster analysis showed there were five forest communities on the site, and both short-term (4 years) and long-term (50 years) flooding records documented a flooding gradient: water tupelo community > swamp tupelo > laurel oak = overcup oak > mixed oak. The long-term hydrologic record showed that the floodplain has flooded less frequently from 1994 to present than in previous decades. Detrended correspondence analysis of environmental and relative basal area values showed that 27% of the variation in overstory community structure could be explained by the first two axes; however, fitting the species distributions to the DCA axes using Gaussian regression explained 67% of the variation. Axes were correlated with elevation (flooding intensity) and soil characteristics related to rooting volume and cation nutrient availability. Our study suggests that flooding is the major factor affecting community structure, but soil characteristics also may be factors in community structure in blackwater systems.

Community Participation in Preservation of Lowcountry South Carolina Sweetgrass (Muhlenbergia filipes [M. A. Curtis] J. Pinson and W. Batson) Basketry

Sweetgrass (Muhlenbergia filipes [M. A. Curtis] J. Pinson and W. Batson) is a coastal, nontimber forest resource ranging from North Carolina southwestward to Texas. The plant has special cultural and economic importance in coastal South Carolina, where the local Gullah community uses this resource in a form of coiled basketry. The plant is becoming increasingly unavailable to basket makers, however, because of habitat destruction, habitat limitation, and private ownership of the resource. This study examines stakeholder involvement in and perceptions of past and current sweetgrass management. Twenty-three interviews were conducted with Charleston, South Carolina area basket makers and were analyzed for emergent themes using content analysis, a technique permitting objective analysis of text. Survey respondents identified residential development as a major cause of sweetgrass inaccessibility and indicated that purchasing raw materials has become standard practice. Furthermore, respondents indicated several potential solutions to the problem and expressed their willingness to contribute time to management efforts.

Soil incorporation of logging residue affects fine-root and mycorrhizal root-tip dynamics of young loblolly pine clones

Loblolly pine (Pinus taeda L.) plantations cover a large geographic area of the southeastern USA and supply a large proportion of the nations wood products. Research on management strategies designed to maximize wood production while also optimizing nutrient use efficiency and soil C sequestration is needed. We used minirhizotrons to quantify the effects of incorporating logging residues into soil on fine-root standing crop, production and mortality, and mycorrhizal root tips in young loblolly pine clones of contrasting ideotypes. Clone 93 is known to allocate more C to stem growth, while clone 32 allocates less C to stems and more to leaves. The relative allocation by these clones to support fine-root turnover is unknown. Clone 32 exhibited 37% more fine-root mortality than clone 93, which was mainly the result of a greater standing crop of fine roots. Fine-root standing crop in plots amended with logging residue was initially higher than control plots, but 2.5 years after planting, standing crop in control plots had exceeded that in mulched plots. Production of mycorrhizal root tips, on the other hand, was initially higher in control than mulched plots, but during the last 9 months of the study, mycorrhizal tip production was greater in mulched than control plots, especially for clone 93. As expected, turnover rate of fine roots was greater in surface soil (0-25 cm) compared with deeper (25-50 cm) soil and for small roots (< 0.4 mm diameter) compared with larger fine roots (0.4-2.0 mm diameter). Rates of fine-root turnover were similar in both clones. Organic matter additions reduced survivorship of individual roots and increased turnover rates of fine-root populations. Results indicate that management decisions should be tailored to fit the growth and allocation patterns of available clones.

Predicting Hydrology in Wetlands Designed for Coastal Stormwater Management

Detention ponds are currently accepted as stormwater best management practices (BMPs) in coastal South Carolina. These ponds are typical catch basins for stormwater piped directly from impervious surfaces in many residential and resort areas. Nutrients often concentrate in the ponds and contribute to eutrophication within the ponds and downgradient estuaries. A supplementary BMP is proposed that would augment nutrient attenuation in these urbanized watersheds and subsequently reduce the potential for nutrients to enter adjacent estuaries. A created wetland was designed to border an existing detention pond on Kiawah Island, SC, providing a vegetated buffer with increased retention time for stormwater flows from upland residential and recreational uses toward ecologically sensitive receiving estuarine waters. The overall objective of the project was to determine the feasibility of a created wetland as a retrofit option. The unique design incorporates aspects of both subsurface and surface-flow constructed wetlands for processing nutrient-enriched stormwater and groundwater, focusing on encouraging denitrification for the reduction of nitrate fluxes into the detention pond. For hydrologic evaluation, a continuous water balance model was developed using STELLA® software to determine the hydrologic capacity and stormwater management potential of two selected wetland designs. This paper describes the evaluation process and assesses the design concept in terms of stormwater management.