John Porter Co-P.I._____________________________
Herman Shugart Co-P.I. _____________________________
Department of Environmental Sciences
University of Virginia
Charlottesville, VA 22903
Long-Term Ecological Research on Landscape Development and Ecological Processes in a Tide-Dominated Barrier-Lagoon Complex: LTER II
NSF DEB 92-11772; $1,241,406; September 1, 1992 to October 31, 1994.
From January 1993 through the present, 31 journal articles have appeared in print,14 are in press (1994 citations) and 13 are under review (1994 citations). VCR PIs have contributed 15 book chapters in print and 4 in press and 2 books which offer synthesis of research and theory at the site and also support intersite and network initiatives. Twelve theses and dissertations were completed.
Disturbance Studies -- Large-scale, long-term research at the VCR focuses on the causes and effects of ecosystem disturbance and change. For example, we derived estimates of the wave energies of 1447 coastal storms since 1942 (Dolan and Davis 1993) and analyzed the impact of these storms on island dynamics (Fenster and Dolan 1994). Studies at the VCR showed a reversal in the shoreline dynamics (erosion and accretion) beginning around 1969; based on this indication, the same type of data was studied for the 1500 km of barrier island coast between New Jersey and Florid. It was discovered that, in the late 1960s a reversal of erosion and accretion patterns is evident for the entire Atlantic seaboard. This observation has direct importance to national programs like Federal Flood Insurance.
We also studied the role of disturbance on vegetation zonation along the coastal strand. We calculated the occurrence probabilities of 100 barrier island plant species across the historical storm disturbance gradient (Fahrig et al 1993) and concluded that disturbance due to coastal storms explains vegetation zonation. Salt spray is not needed to explain this zonation. Foyle (1994), Foyle and Oertel (1994), Oertel and Kraft (1993) and Oertel et al. (1993) charted the drainage patterns of VCR lagoons and showed their continuity with paleochannels on the continental shelf. These finding stimulated a new model for the origin of the lagoon and marshes of mid-Atlantic barrier islands (Oertel and Kraft 1993).
Geographical Information Systems -- We completed the GIS framework for the annual VCR colonial bird nesting survey and have included the 1993 GPS geo-referenced bird survey is in this system. In the long-term we will track changes in utilization of the landscape by colonial birds. In addition, we have mapped land cover and changes in land cover for the VCR using TM satellite imagery. This GIS cooperation will directly aid the Nature Conservancy in conservation and management activities. We installed a NASA sun photometer to better correct satellite imagery for atmospheric effects; completed our first study of spectral reflectance of barrier island plants (Carter and Young 1993); and demonstrated the utility of TM, Spot and aerial photography for analysis for vegetation change (Porter and Callahan 1994). In the Spring of 1994 we negotiated a partnership with Northampton County, Virginia to assist in the development of their county planning Geographic Information System GIS. UVa and the VCR LTER will develop the natural and cultural history GIS layers. With this agreement we will directly contribute our research findings to the local planning authorities. LTER capabilities in GIS provide a direct route to science application and public education.
Biogeographic Surveys -- Habitat composition and utilization at this large spatial scale remain strong research areas. Biogeographic surveys of island vegetation, lagoonal fish (Yozzo 1994), marcoalgae (Monti 1993), and insular small mammal populations (Porter and Dueser 1994) were completed in late 1993. Tissue samples were collected for allozyme analysis of small mammals on 11 islands; and analysis of blood samples to test for the presence of Hantavirus were negative (Moncrief, pers. comm.). Forys and Dueser (1993) documented movements of rice rats (Oryzomys palustris) between Crescent and Parramore Islands, all of which originated on the smaller island. We found that rats dispersing between islands comprise a statistically random subset of the resident population with respect to age and sex, unlike overland dispersers which are predominantly juveniles. Our biogeographic surveys are conducted on a campaign basis, with expected surveys at intervals of 3-5 years.
Through extensive surveys we have established the relationship between perched freshwater reserves and local land elevation across scales from microtopographic variations on marsh surfaces to the scale of dune/swale systems. In this framework, coastal storms transport sand and elevate land surface levels, thereby permitting higher fresh water-table elevations (Stasavich and Hmieleski 1993). A Bucknell REU working at the VCR found, in support of the overwwas theory that over 90% of the beach sand washed inland by storm events remains in place on the island; only 10% of the sand returns to the beach by winds (Cohn 1993; Clark 1993). This discovery pertains to a long standing debate in the geosciences over the role of overwash in westward island migrations due to sea level rise. In areas of Hog Island where storm overwash disturbance is frequent, clonal growth forms dominate (Fahrig et al. 1993). Both ocean side flooding due to storm surge and lagoon side flooding due to wind tides result in salinity stresses on terrestrial island vegetation. Young et al. (1994) established the salinity tolerances of individual plant species. These studies highlight the sensitivity of the VCR ecosystem to subtle changes in the relative elevations of the land surface and the fresh/salt water interface.
Productivity and Organic Matter Accumulation -- Along the gradient from low to high marsh, root decay is not affected by sediment physico-chemical differences, although root production is much greater in the mid-marsh zone perhaps due to tidal inundation conditions. Differences in organic matter accumulation between high and low marsh areas are thus due to differences in root production rather than root decomposition (Blum 1993). Although position in the marsh and sediment pore water chemistry has little effect on root decay, Juncus roots decay two times faster than Spartina roots. This difference is consistent with the difference in the starting C:N ratios of 37:1 and 47:1 for Juncus and Spartina, respectively. Regardless of the type of organic matter (i.e., Juncus or Spartina) or location in the marsh, the vast majority of below ground organic matter is old and recalcitrant (Christian et al. 1993).
Development and Succession in Marshes -- The marsh area of the fringing marshes of the mainland has increased by 8% over 50 years, primarily because of upland encroachment (Kastler 1993) due to sea level rise. Increases in marsh extent at the expense of terrestrial "upland" vegetation is also recorded on the barrier islands form 1949 to the present with a 25 m wide zone mapped. This zone was in 1949 a Myrica shrub thicket and now is a high marsh. Due to ea level rise, the lagoons are encroaching landward at a rate of 0.5 m / yr. Lead dating of the sediments indicate a sediment accretion rate of 2 mm per year on the mainland fringe marshes (Kastler 1993). Analysis of the clay mineralogy of these marsh sediments indicate that this marsh developed on top of upland soils similar to those found in neighboring agricultural and forested areas (Robinson 1993). Textural and mineralogical analysis of inorganic sediments from throughout the VCR revealed that each physiographic area (i.e., mainland, marsh surface, channel bottom) has a distinct sedimentological signature (Oura 1993; Robinson 1993). Regions of elevated paleotopography are identified as drowned uplands through the presence of kaolinite and vermiculite (similar to mainland soils) sampled in meter-deep cores. Preliminary 210Pb dating of sediment cores suggests that sedimentation rates in the VCR system are 1.0-2.2 mm/yr (Kastler 1993); major storm horizons are easily identified within the shallow cores (Kastler 1993; Robinson 1993).
Nutrient Cycling and Succession -- The rate of succession in salt marshes as evidenced by geochemical development of marsh sediments was found to be extremely rapid. Extractable ammonium and porewater ammonium and phosphate in the surface layers of young salt marshes (10-13 years) are nearly identical to those in marshes >100 years old, indicating a more rapid chemical maturation than previously determined (Osgood and Zieman 1993a,b; 1994). Marshes less than 2 years old were found to have sediment geochemistry similar to the older marshes.
At the Mainland Marsh Site and in other VCR tidal creeks, the rate of carbon cycling by bacteria is much lower than in nearby creeks of Chesapeake Bay despite high concentrations of inorganic N and P. The high inorganic nutrient pools combined with the low levels of bacterial productivity indicate that bacterial production is not limited by N or P and that the amount of carbon moving through the bacterial loop is low relative to Chesapeake Bay tidal creeks on the Delmarva Peninsula.
Agricultural Impacts on VCR Lagoons and Marshes --Preliminary nutrient analyses of round water in shallow wells along the mainland marsh fringe indicate that nitrate concentrations are higher on the creek side of the field than on the marsh side (mean NO3- = 260 uM/L and 3 uM/L, respectively). Ammonium concentrations are greater on the marsh side of the field than on the creek side (mean NH4+ = 35 uM/L and 8 uM/L, respectively). The junction between mainland agriculture environments and the interfacing fringing marshes is a boundary between nitrate and ammonium based nitrogen economies. Given the long agricultural history of the site, the maintenance of sharp biogeochemical ecotones implies very low horizontal hydraulic conductivities and little direct agricultural impacts on the lagoons of the VCR.
We are approaching the end of 2 years of our renewed water quality/ nutrient monitoring program. Island and mainland creeks appears largely light limited rather than nutrient limited. While nutrient concentrations are higher than what would be expected off-shore, they are not so high as to indicate major cultural eutrophication.
Long-Term Experiments -- Three long-term experiments were installed during 1992 and 1993. These experiments are designed to modify the relative levels of the land, the fresh water table and the lagoon waters. In our marsh-surface lowering experiment, sections of the marshes were lowered 15 cm to mimic a sea level change in excess of upward accretion of the marsh surface. Results from the first year indicate changing the level of the marsh relative to sea level, that biomass, stem density and stem heights all increased as a result of the relative increase in lagoon elevations.
A second long-term experiment, installed in June 1993, involves a solar powered pump to lower the local fresh-water table by 1 to 3 mm d-1. Using well fields, we have determined that we can monitor mm changes in the terrestrial fresh-water table resulting from semi-diurnal tides, spring-neap tidal cycles, daily evapotranspiration and rainfall input. Terrestrial ecosystems embedded in marine waters and saline sediments are tidal ecosystems in that the astronomical and wind tides cause fresh ground water to move upward into the root zone of the vegetation thus putting freshwater resources on a tidal time-table. And, we have, for the first time, achieved a direct measured daily community wide rates of evapotranspiration at the mm level of resolution.
The hydrology and water chemistry of isolated fresh-water sand masses perched on a saline-to-hypersaline marshes was initiated during the past year. We completed intensive surveys of the topography, vegetation and water salinity. The extent and salinity of the fresh-water reserves beneath the sand masses was determined to 1 ppm precision over a depth of 5.5 meters where salinity reaches maximum value of 26 ppt. The fresh water lens of these terrestrial features also extends roughly one meter laterally beyond the topographic margin of the terrestrial part of the landscape studied. Salt tolerant shrubs occupy this zone.
We designed, constructed, tested and implemented the inundation experiment at Brownsville, Phillips Creek marsh. Experimental plots are flooded with every high tide, whereas normally they are only flooded during spring tides. Disturbed and undisturbed control plots are paired with each experimental plot. First data from this experiment will be obtained in the summer of 1994.
INTERSITE, MODELING AND SYNTHETIC STUDIES
Our theoretical, synthesis and modeling papers focus on the ecosystem response to global climate change (Shugart 1993a, b; Shugart and Soloman 1993, Smith and Shugart 1993; Soloman and Shugart 1993; Davis et al. 1994; Hayden 1994a, b, c; Shao et al. 1994a, b); succession in terrestrial and upland ecosystems (Friend et al. 1993; Fahrig et al 1993 and 1994; Lauenroth et al. 1993; Shao et al. 1993, 1994a, b); and on the structure and dynamics of coastal and pelagic ecosystems (Oertel 1993a, b, 1994, Oertel et al. 1994a, b, c; Christian 1994). We have also participated directly in providing published overviews of integrating regional models of ecosystems with social systems (Hayden 1994a) and of long-term data needs for long-term studies and modeling efforts (Hayden 1994 b).
Our studies of marsh dynamics at the landscape level have lead us to propose a conceptual model of sea-level induced transition from terrestrial forest to estuary (Brinson et al. 1994). Important components of this model include self-maintaining properties and state changes due to disturbance or exposure to acute stress. The mechanisms responsible for maintenance and transition along the gradient from lagoon to upland are unique for each zone within the marsh. For example, the position of the upland-high marsh transition depends upon the slope of the marsh surface and the distance from a tidal creek. Along steep marsh surface slopes, elevation is the primary factor influencing the position of the transition, while along very gentle slopes distance from the nearest tidal creek is most important
Between 1992 and the present we have graduated 11 students with advanced degrees (8 MS and 3 Ph.D.) who have received part or all of their support from the VCR LTER core grant. We currently have 13 MS students and 5 Ph.D. students conducting research at the site. Thirteen of the published papers reported on in the results of prior NSF support involved graduate students. In addition, we had 4 REU students during the 1992 field season and following semester, and 5 REU students in 1993. In 1994 we have 5 REU students supported on Supplement Grant and 3 additional REUs supported on the core grant. Three of the four 1992 students are now in Graduate School and the fourth is applying to Graduate School. All of the 1993 REU students have plans to enter graduate school. We supported 4 additional undergraduate students in 1993 and they also have plans for graduate school.
Blum, L.K. 1993. Spartina alterniflora root dynamics in a Virginia marsh. Marine Ecol. Prog. Series.102:169-178.
Brinson, M.M., R.R. Christian, and L.K. Blum 1994. Multiple states in the sea-level induced transition from forest to estuary. Estuaries. In Review.
Bulger, A., B.P. Hayden, M.A. Monaco and J. McCormick-Ray 1993. Biologically-based estuarine salinity zones derived from a multivariate analysis. Estuaries. 16(2):311-322.
Carter, G.A. and D.R. Young 1994. Foliar spectral reflectance and plant stress on a barrier island. Internat. J. Plant Sciences. In Review
Christian, R.R. 1994. Aggregation and disaggregation of microbial food webs. Microbial Ecol. (In Review)
Clark, C.J. 1993. Comparison of storm characteristics and their relation to barrier island overwash, Eastern shore of Virginia.Undergraduate thesis. Bucknell University Lewisberg, Pa.
Cohn, M. 1993. The relative role of geomorphic processes in the storm recovery of washover sites on the Virginia barrier islands.Undergraduate thesis. Bucknell University, Lewisberg, Pa.
Conn, C.E. and F.P. Day 1993a. Belowground biomass patterns on a coastal barrier island in Virginia. Bull. Torrey Bot. Club 120: 121-127.
Conn, C.E. and F.P. Day 1993b. Environmental influences on belowground decomposition rates along a barrier island chronosequence. Bull. Ecol. Soc. Amer. 74(2):198.
Davis, R.E., B.P. Hayden, D.A. Gay and W.L. Phillips. 1994. The Atlantic subtropical anticyclone. J. Climate. In Review.
Day, F.P.1993. Plant response to nitrogen fertilization on a barrier island dune chronosequence. Bull. Ecol. Soc. Amer. 74(2):210.
Fahrig, L., D.P. Coffin, W.K. Lauenroth and H.H. Shugart. 1994. The advantage of long-distance clonal spreading in highly disturbed habitats. Evolutionary Ecology. In Press.
Fahrig, L., B. Hayden and R. Dolan 1993. Distribution of barrier island plants in relation to overwash disturbance: A test of life history theory. J. Coastal Research. 9(2):403-412.
Fenster, M. and R. Dolan 1994. Large-scale reversals in shoreline trends along the U.S. mid-Atlantic Coast. Geology 22:543-546.
Forys, E.A. and R.D. Dueser 1993. Inter-island movements of rice rats (Oryzomys palustris). American Midland Naturalist 130:408-412.
Foyle, A.M. and G.F. Oertel 1994. Seismic stratigraphy and coastal drainage in the Quaternary section of the southern Delmarva Peninsula, VA, USA. Sedimentary Geology. In Press.
Foyle, A.M. 1994. Quaternary seismic stratigraphy of the inner continental shelf, southern Delmarva Peninsula, Va. Ph.D. thesis. Old Dominion University, Norfolk, Va.
Friend, A.D., H.H. Shugart and S.W. Running 1993. A physiology-based model of forest dynamics. Ecology. 74:792-797.
Halama, K.J. and R.D. Dueser. 1994. Of mice and habitats: Tests for density-dependent habitat selection. Oikos. In Press.
Hayden, B.P. 1994. "Outsider" Overview of Biological Models. In P.Groffman and G. Likens (eds.) Integrated Regional Models: Interactions between humans and their environment. Chapman and Hall. In Press.
Hayden, B.P. 1994. Global biosphere data base requirements for GCMs. In W. K. Michener, S. Stafford and J. W. Brunt (eds.) Environmental Information Management. Taylor and Francis, N. Y. In Press.
Hayden, B.P. 1994. Feedbacks between the biosphere and the atmosphere. Ecological Applications. In Review.
Harvey, J.W. 1993. Measurement of variation in soil solute tracer concentration across a range of effective pore sizes. Water Resources Res. 29(6):1831-1837.
Harvey, J.W. and W.K. Nuttle 1994. Fluxes of water and solute in a coastal wetland sediment, 1: The contribution of regional groundwater discharge. Journal of Hydrology. In Review.
Hmieleski, J. I. 1994. Position of the Brackish Marsh-Upland Transition as a Function of Elevation and Slope at the Virginia Coast Reserve, LTER. MS thesis. East Carolina University, Greenville, N.C.
Hoelscher, J.R., W.K. Nuttle and J.W. Harvey 1993. Comment on "Calibration and use of pressure transducers in soil hydrology." Hydrol. Proc.7:205-211.
Johnson, S.R. and D.R. Young 1994. Factors contributing to the decline of Pinus taeda on a Virginia barrier islands. Bull. Torrey Bot. Club. In Press.
Kastler, J.A. 1993. Sedimentation and landscape evolution of Virginia salt marshes. MS thesis. University of Virginia, Charlottesville, Va.
Kowalski, K.A. 1993. Influence of stratigraphy and bathymetry on erosion rates, Virginia Barrier Islands.Undergraduate thesis. Bucknell University, Lewisberg, PA.
Lakshmi, B. and F.P. Day 1993. Nitrogen availability along a community chronosequence on Hog Island, a VCR LTER site. Bull. Ecol. Soc. Amer. 74(2):321.
Lauenroth, W.K., D.L. Urban, D.P. Coffin, W.J. Parton, H H. Shugart, T.B. Kirchner and T.M. Smith. 1993. Modeling vegetation structure-ecosystem process interactions across sites and biomes. Ecological Modeling 67:49-80.
MacMillin, K.M. 1993. Bacterial dynamics in tidal marsh creeks of the Eastern Shore of Virginia. MS thesis. University of Virginia, Charlottesville, Va.
Moorhead, K.K and M.M. Brinson 1994. Response of wetlands to rising sea level in the lower coastal plain of North Carolina. Ecological Applications. In Press.
Monti, M. M. 1993. Distribution, abundance and productivity of intertidal macroalgae on the Eastern Shore of Virginia. MS thesis. University of Virginia, Charlottesville, Va.
Nuttle, W. K. and J. W. Harvey. 1994. Fluxes of water and solute in a coastal wetland sediment, 2: The contribution of regional groundwater discharge. Journal of Hydrology. In Review.
Nuttle, W.K. and H.F. Hemond 1994. Salt marsh hydrology: implications for biogeochemical fluxes to the atmosphere and estuaries. Global Biogeochem. Cycles. In Press.
Oertel, G.F. 1994. Paleographic and morphostratigraphic studies at the barrier island Long-Term Ecological Research site. In Press.
Oertel, G.F. and J.C. Kraft 1993. New Jersey and Delmarva barrier islands. In R.E. Davis (ed.) Geology of Coastal Barrier Systems. Springer-Verlag.
Oertel, G.F., J.C. Kraft, M.S. Kearnery and H.J. Woo 1993. A rational theory for barrier lagoon development. SEPM: Special Publication #48. Quaternary Coasts of the United States: Marine and Lacustrine Systems.
Oertel, G.F. and H.J. Woo 1994. Landscape classification and terminology for lagoon marsh. J. Coastal Research. In Press.
Oertel, G.F, H.J. Woo, M.S. Kearnery and A.M. Foyle 1994. Regressive to transgressive Quaternary deposits in a Delmarva coastal lagoon. Hog Island Bay, Virginia. AAPG Bull. In Press.
Oertel, G.F. and A.M. Foyle 1994. Drainage displacement and capture by sea-level fluctuation at the outer margin of the Chesapeake Bay seaway. SEPM Special Publication. In Press.
Osgood, D. and J.C. Zieman 1994. Factors controlling above-ground Spartina alterniflora production and tissue element composition in different aged barrier island marshes. Estuaries. In Press.
Osgood, D. and J.C. Zieman 1993a. A comparison of physical and chemical properties of substrate in different aged barrier island marshes. Estuaries.16(4):815-826.
Osgood, D. and J.C. Zieman 1993b. Spatial and temporal patterns of substrate physicochemical parameters in different-aged barrier island marshes. Estuarine, Coastal and Shelf Sci. 37:421-436.
Oura, S. 1993. Clay mineralogy of suspended sediments of the Eastern Shore marshes. Undergraduate thesis, University of Virginia, Charlottesville, Va.
Porter, J.H. and J.L. Dooley, Jr. 1993. Animal dispersal patterns: a reassessment of simple mathematical models. Ecology 74:2436-2443.
Porter, J.P. and J.T. Callahan. 1994. Ecological assessment using remotely-sensed data: a comparison of image sources. Landscape Ecology. In Review.
Porter, J.P. and J.T. Callahan. 1994. Circumventing a dilemma: historical approaches to data sharing. In W. K. Michener, S. Stafford and J. W. Brunt (eds.) Environmental Information Management. Taylor and Francis, N. Y. In Press.
Robinson S.E. 1993. Clay mineralogy and sediment texture of environments in a barrier island - lagoon system. MS thesis. University of Virginia, Charlottesville, Va.
Semones, S.W. and D.R. Young. 1994. Possible VAM association in barrier island populations of Myrica cerifera. Mycorrhizae. In Press.
Shao, G. J.H. Porter and H.H. Shugart. 1993. Shrub thicket dynamics on hog Island, Virginia. [Computer Generated Maps] p. 48 in Arc/Info Maps 1992. Environmental Systems Research Institute, Inc., Redlands California.
Shao, G., H.H. Shugart and D.R. Young. 1994a. Simulation of transpiration sensitivity to environmental changes for shrub (Myrica cerifera) thickets on a Virginia barrier island. Ecological Modelling. In Press.
Shao, G., D.R. Young, J.H. Porter and H.H. Shugart. 1994b. Spatial expansion of shrub thickets on barrier islands of Virginia. Landscape Ecology. In Review.
Shugart, H.H. 1993a. Vegetation and Climate. In S.H. Schneider (ed.), Encyclopedia of Climate and Weather. Simon and Schuster, New York.
Shugart, H. H. 1993b. Global Change. (pp. 2-21). In: A. M. Solomon and H. H. Shugart (eds.) Vegetation Dynamics and Global Change. Chapman and Hall, New York.
Shugart, H.H. and A.M. Soloman. 1993. Concluding Comments (pp. 323-324). In A. M. Solomon and H.H. Shugart (eds.). Vegetation Dynamics and Global Change. Chapman and Hall, New York.
Smith, T.M. and H.H. Shugart. 1993. Transient response of terrestrial carbon storage to a perturbed climate. Nature 361:523-526.
Stasavich, L.E. and J.I. Hmieleski 1993. Salinity changes in sediments of a barrier island and mainland marsh following an extratropical storm at the Virginia Coast Reserve/LTER. pp. 891-893. in M.C. Landin (ed.). Wetlands: Proceedings of the 13th Annual Conference of the Society of Wetland Scientists, New Orleans, LA.
Solomon, A.M. and H.H. Shugart 1993. Vegetation Dynamics and Global Change. Chapman and Hall, NY. 338 pp.
Stevenson, M. and F.P. Day 1993. Fine root production along a chronosequence of barrier island communities. Bull. Ecol. Soc. Amer. 74(2):444.
Weber, E.P. and F. Day 1993. The effect of nitrogen fertilization on the phenology of roots in a barrier island dune ecosystem: a minirhizotron analysis. Bull. Ecol. Soc. Amer. 74(2):481.
Young, D.R., D.L. Erickson, and S.W. Semones 1994. Salinity and small-scale distribution of three common shrubs on a Virginia barrier island. Canadian J. Botany. In Review.
Young, D.R., G. Shao and M.M. Brinson 1994. The impact of the October 1991 Northeaster Storm on barrier island shrub thickets (Myrica cerifra). J. Coastal Research.
Young, D. R., G. Shao and J. H. Porter 1994. Temporal and spatial growth dynamics of barrier island shrub thickets. American Journal of Botany. In Review.
Yozzo, D.J., A. Mannino and D.E. Smith 1994. Mid-summer abundance of larval and juvenile finfish and decapods on the surface of fringing mainland and back-barrier marshes, Virginia Coast Reserve. In Review.