ANNUAL PROGRESS REPORT VCR/LTER MAY 1991 Herman H. Shugart, P.I. __________________________ Linda K. Blum, Co-P.I. __________________________ Department of Environmental Sciences Clark Hall University of Virginia Charlottesville, Virginia 22903 TABLE OF CONTENTS ADMINISTRATIVE OVERVIEW.......1 Personnel Changes............................................................................1 Site Reviews.................................................................................1 SCIENTIFIC OVERVIEW.............................................2 Primary Production...........................................................................2 Organic Matter Accumulation..................................................................4 Disturbance..................................................................................5 Nutrient Inputs, Transformations, and Movements............6 Trophic Structure............................................................................7 Modeling and GIS.............................................................................8 Data Management..............................................................................9 Network Activities...........................................................................9 APPENDICES......................................................11 PUBLICATIONS....................................................12 PRESENTATIONS...................................................13 ADMINISTRATIVE OVERVIEW Personnel Changes The past year at the Virginia Coast Reserve/Long Term Ecological Research Site has proven to be quite challenging. We have undergone significant changes in the administration of the VCR due to the loss of two of the original principal scientists. Raymond Dueser, the VCR's principal investigator for the first three years of the project, left the University of Virginia in May, 1990. William Odum then took over as principal investigator in June, 1990. He served as principal investigator until his death in April of 1991. Subsequently, Hank Shugart was designated as the principal investigator of the VCR/LTER. Linda Blum will serve as co-PI. The administrative duties of project will be shared by Hank and Linda. We have been fortunate to be able to add a half-time field instrumentation expert to our staff. David Krovetz joined the project in April. His responsibilities include change-over of our meteorological and tide monitoring effort to real-time data acquisition, calibration of the monitoring equipment, and trouble-shooting. Dave has had a tremendous amount of experience in this area through his involvement with the National Park Service and EPA projects on mountain cloud chemistry in the Shenandoah National Park. As a result of Dave's efforts, data acquisition from the field monitoring equipment has already become much more reliable, and transfer of those data to the data archives has become much more efficient and rapid. Dr. Guofan Shao, who is on the faculty of the Chinese Academy of Science's Institute of Applied Ecology, joined the VCR/LTER project in March and will be working with us for one year. Prior to joining the VCR/LTER, Shao worked at the Changbai Shan Biosphere Reserve, one of the Republic of China's LTER sites, on forest dynamics. Shao has had extensive experience in applying data collected using ARC/INFO and GIS systems to forest dynamics models. Shao is focusing on adapting the data collection techniques that he has used for trees to study and model shrub dynamics on Hog Island. Site Reviews This year the VCR/LTER scientists met with our advisory committee in the spring and had an NSF review team visit late in the summer. Both of these activities were quite productive and eventually resulted in several changes in the scientific organizational structure of the VCR/LTER. Because the VCR is a large and complex landscape and because system state transition events are frequent and widespread, we have chosen to focus most of our field monitoring and experimentation upon several state transition sites. To accomplish this more effectively and maximize interaction between researchers, we have divided our effort into three working groups: the terrestrial team, the water team, and the GIS/modeling team. Connection between the groups is maintained by a number of individuals who are members of more than one group (e.g. Zieman who serves on both the water and modeling groups) and a few individuals who are members of all groups (e.g. Shugart). This organization should allow us to better understand the details of major state changes caused by climate change, sea level rise, storms, ecological succession, and human activities and it should serve to facilitate coordination and cooperation across the broad areas represented by the groups. Each of the working groups met this spring for a day-long workshop. The terrestrial team includes those who are concerned with sites which lie above mean high tide. They are studying the major transects across Hog Island along with several locations on the mainland. Particular emphasis is placed on recently overwashed and flattened dunes and on vegetated dunes which have not flooded for decades. This group has identified the role of the island's subsurface, water-table aquifer as a key element of the barrier island function both because it influences the composition, distribution and productivity of the patchy terrestrial vegetation and because it provides an important link to sub-tidal processes (studied by the water team). The water team is focusing on transects from the island to the mainland which cut across the "dynamic edge" spanning the land-sea interface from the sub-tidal mud flats and marshes to adjacent salt-stressed wetland and low-lying terrestrial ecosystems. This group is particularly interested in changes in surface elevation, porewater chemistry, nutrient cycling, vascular plant composition, decomposition and other parameters which accompany both short and long-term changes in sea level. The modeling/GIS team is responsible for monitoring and studying system state changes on a much larger scale, including all of the VCR and, even in some cases, selected island-lagoon systems along the U.S. Atlantic east coast. Emphasis is placed upon the temporal and spatial characteristic of system state changes which can be identified from remotely sensed data, analyzed with GIS techniques and simulation models. Examples include changes in distribution and size of terrestrial vegetation patches, marshes, beaches, dune fields, overwash fans, inlets, mudflats, etc. from the mid nineteenth century to the present. SCIENTIFIC OVERVIEW During the past year we have continued to invest most of our efforts into the five core areas and to establish a paleogeographic record of the barrier island complex. We expect that our activities will continue to focus on identification of the factors controlling the ecological processes of this system and the interaction between the ecological and highly dynamic physical processes of the VCR through the summer 1992. The working groups are contributing to the core monitoring program in each of the habitat types studied. The objectives of each working group are to examine the core areas with methods appropriate for the specific ecosystem and to identify the controlling influences on the ecological processes. We have made good progress especially in the areas of primary productivity, organic matter accumulation, and disturbance. Progress in the area of nutrient inputs and movements has been much more difficult as a result of the extremely complex water circulation patterns in the lagoons and the complex hydrologic interactions between mainland, marsh, marsh creeks, and islands. However, we have identified key questions that should allow us to address the area of nutrient inputs/movements. We are initiating several new projects this field season which should increase our understanding of the trophic structure of the system. Primary Production Primary production measurements made by the terrestrial group have focused on Myrica cerifera. Both above- and belowground measurements are being made. Seasonal variations in photosynthesis and water relations parameters have been quantified for myrtle. There is little variation in maximum values for net CO2 assimilation (32 amol CO2 m-2 s-1), stomatal conductance to water vapor diffusion (9.5 mm s-1), and maximum xylem pressure potential (-0.7 MPa). Midday minimum xylem pressure often is less than -1.5 MPa. Data from the field and measurements on glasshouse plants indicated that stomatal opening and photosynthesis are sensitive to plant moisture stress (<-0.8 MPa) and the leaf-to-air humidity deficit (>1.5kPa). Using meteorological data and derived photosynthetic responses, predictions indicated that M. cerifera photosynthesis would have been limited at the field site due to non-optimal air temperatures and humidity deficits on all but two days during the relatively dry summer of 1990. Even during the relatively wet summer of 1989 photosynthesis was limited on more than 90% of the days. It is fairly clear that productivity of M. cerifera on the islands of the VCR is continually held in check by sub-optimal temperatures and atmospheric humidity. Photosynthesis and production may be further reduced by periodic exposure to salinity pulses from storm overwash and salt spray. Information concerning M. cerifera belowground production and controls on production is not yet available. Plots were established in the fall of 1990 to monitor belowground production were established to coincide with the aboveground measurements. Several methods are being used to assess root production: sequential coring and two root ingrowth techniques. Minirhizotrons are presently being installed to monitor root dynamics in the myrica thickets. Several microenvironmental measurements are being gathered and will be examined for correlation root production and to allow for more complete elucidation of the nitrogen cycle and the influence of nitrogen on belowground production. The microenvironmental parameters being measured include nitrogen mineralization rates in fertilized and unfertilized plots, soil moisture content, ground water levels, pH, and soil temperatures. Salt marsh primary production is an area of focus for the water group. Spartina alterniflora above- and belowground production is being monitored in several marsh types. Aboveground production is being estimated on a series of permanent plots. The methodology, developed by Jim Morris at the North Inlet LTER site, utilizes length-weight relationships of permanently marked plants. Differences in aboveground production were observed between high and low regions of "young" marshes (relatively large grain sizes), 1287 g m-2 growing season-1 and 901 g m-2 growing season-1, respectively. Differences were also observed between "young" and "older" marshes (relatively smaller grain sizes). The older marsh sites were characterized by lower estimates of production (155 g m-2 growing season-1 and 145 g m-2 growing season-1 at the low and high marsh, respectively). Belowgound production measurements are available for "older" marshes where differences in production are observed with sediment depth (greatest production in the 0-10 cm and 10-20 cm regions, high and low marsh respectively) and between high (2143 g m-2 growing season-1) and low marsh (676 g m-2 growing season-1). Belowground production was similar during the two growing seasons monitored. Measurement of belowground production was begun in additional marshes this spring. Sediment pore-water chemistry is being monitored at all of the marsh productivity sites. Preliminary results suggest that morphology and primary production, both above- and belowground, are strongly affected by pore-water conditions, particularly salinity and hydrogen sulfide concentrations. Water-column primary productivity is being measured for phytoplankton and macroalgae. Phytoplankton production is being measured at the ends of the mainland to barrier island transect; Phillips Creek (mainland) and Cattleshed Creek (Hog Island). Samples are collected and incubated at two depths, 0.5 and 1.0 m. Water column production and respiration does not differ between these sites. Respiration values were similar at both depths. However, net production was lower in the deeper incubation. Nutrient amendments (ammonium, nitrate, and phosphate, individually and in combination) had no effect on net production or respiration. When simultaneous experiments were done in Hog Island Bay (high turbidity) and Chesapeake Bay (low turbidity), phytoplankton production and respiration values were much lower for the Hog Island Bay samples. The lack of a nutrient effect on production and respiration for Hog Island Bay samples and the results of the Hog Island Bay/Chesapeake Bay comparison may indicate that phytoplankton production in the barrier island system is not nutrient limited, but that light limitations controls water-column production. The ubiquity of intertidal macroalgae in the barrier island system lead us to study their distribution and production across Hog Island Bay. Ulva lactuca is the dominant species and persists throughout the year. There is a pattern of decreasing species richness and diversity in the progression from mean low water to mean high water levels on all of the marshes studied. There is also a seasonal change in the species represented: summer species are replaced by more cold tolerant species in the fall and winter. Production values are not yet available for the macroalgae. Qualitative observations this spring indicate a substantial increase in the biomass of U. lactuca in all of the Virginia barrier island-lagoon complex. An interesting question that derives from this work is the role of macroalgae in the transport of nutrients in the system, in particular from the water column to the marshes. In general, it appears that a major control on primary production in the VCR barrier island systems is water and its movement. In the case of island vegetation, the combined affect of humidity and soil moisture is central to understanding controls on production. In the marshes, evapotranspiration, infrequent tidal flooding, and low sediment porosity combine to yield high salinity and hydrogen sulfide concentrations that appear to have a significant impact on net primary production and the allocation of photosynthate above- and belowground. In the case of phytoplankton and macroalgae, water-column sediment loading is most likely to be the limiting factor on production by these organisms. Organic Matter Accumulation Patterns of organic matter accumulation will be effected by both the rate of primary production and the rate of decomposition. Thus, we have attempted to integrate the primary production and decomposition studies. In many cases the investigators are measuring both primary production and decomposition at the same locations. Litter bags are the primary method being used at the VCR for measurement of decomposition rates. Litter bag measurements are being made in the myrica thickets, and cordgrass (Spartina alterniflora) and black needlerush (Juncus roemerianus) marshes. Between marsh (barrier island fringe, lagoon, and mainland fringe) and high and low marsh comparisons are also being done. One high and low marsh comparison has been completed. The rates of decomposition were similar with depth in the sediment and in the high and low marshes. The most significant finding of this study was the very rapid decay rate. In all locations and at all depths, only 10% of the starting material remained after 1.5 years. Most studies of belowground decomposition have not shown such rapid decay. Typically, plant litter is either air- or oven-dried prior to preparing the litter bag. Litter used at the VCR was not dried and may account for the more rapid decay rate. An experiment to test this hypothesis was set out early this spring. Transplant experiments (J. roemerianus in S. alterniflora marsh and vice versa) to test the relative importance of starting material as compared to environmental conditions as controls on decay rates were also begun early this spring. An experiment to look at relative rates of decomposition, using a standard substrate (wooden dowels), across the transect will be started this summer. Alternative measurements of decay rates are being compared to the litter bag technique for several marsh locations. Wiegert and Evans clip plots were established this winter and are being sampled quarterly. In situ measurements of instantaneous decay indicators are also being measured including sediment respiration, heterotrophic microbial activity (mineralization of acetate and glucose), and bacterial growth rates. To examine the patterns of organic matter accumulation, soil/sediment organic matter concentrations were determined by collecting samples along the mainland to barrier island transect in each major plant class. Organic matter concentrations range from less than 0.05% (beach grass) to over 68% (Spartina patens) in the top 5 cm of soil/sediment. This summer the data will be entered into one of the VCR/LTER's data bases which is compatible with the GIS systems and overlays of the major vegetation classes will be used to create an organic matter map of Hog Island and the mainland to barrier island transect. Rates of soil genesis are known to be related to organic matter accumulation: younger soils are usually deficient in organic matter, and any organic matter is present at or near the soil surface. The soils of the uplands and marshes of the mainland and barrier islands of the VCR coastal lagoon complex were examined for differences in characteristics that could indicate the relative pedological ages. Two upland and two marsh pedons each were sampled and described for the mainland and island sites. On the barrier island, the soils were classified in order of increasing elevation as Fine-silty, mixed, thermic Typic Sulfaquents; Mixed, thermic Typic Psammaquents; and Sandy, thermic Aquic Udipsamments. On the mainland, the marsh soils were Sulfaquents and the slightly-elevated upland soils were Coarse- loamy, mixed, thermic Hapludults. The soils of the mainland have developed from accumulation of finer tidal sediment than abundantly found in the island soils. Tidal marsh soils accumulated more reduced sulfur than the upland soils, and all soils on the mainland held more reduced sulfur than did their island counterparts. Organic matter content in the mainland soils is higher and more uniformly distributed within the soil profile than in the island marsh soils. The pattern of sulfur and organic matter distribution in the soils suggests that the soils of the mainland are either older than those of the island, or are developing more rapidly. Given evidence that the geological age of the island marshes substantially exceeds that of the mainland marshes, the data support the assertion of more rapid pedogenesis in marsh soils near the mainland. From the preliminary decomposition work, it appears that organic matter accumulation in the marshes is controlled to a large degree by the rate of organic matter production. Decomposition is not affected by depth in the sediment nor by the hydrologic regime. The relative importance of the type of starting material and extremes of environmental conditions (i.e. xeric mainland soils compared to hydric marsh sediments) to organic matter accumulation is currently being investigated. Disturbance One of the interesting features of the VCR/LTER is the low- lying landscape which makes the site unusually attractive as a location to study the ecological effects of disturbance on several time scales from daily tidal variations and individual storms through longer term changes in precipitation and, ultimately eustatic sea level rise. Because of the short- and long-term importance of tidal fluctuations, we have put substantial effort into setting up a system of tide gages and water level monitoring equipment. While tropical storms are infrequent (several landfalls per 100 years), the magnitude of the disturbance is great. Collection of data concerning individual storm events has been completed from 1650 to the present and is an ongoing monitoring project. Overwash events occur on a more frequent basis (3-5 times per year) than tropical storms and are related to the occurrence of "northeasters". Overwash events can have a tremendous impact on the upland portions of the islands, moving tremendous volumes of sand and resulting in salt water intrusion into an islands fresh water lens. Monitoring of these washovers is also an ongoing process. The vegetation dynamics work on Hog Island has been organized to acknowledge that ecological observations made on the island must take into account the inherent mobility of the island substrate. Thus, the relationship between the rate of shoreline change and the rate of vegetation becomes an important comparison. South Hog Island is an erosion dominated coastline. There is a strong positive relationship between shoreline dynamics and vegetation occurrence (r2 = 0.91) for South Hog. Additionally, because of the low elevation and thus overwash potential, the influence of abiotic processes on the biotic processes is detectable. South Hog shows clear relationships between salinity, elevation, and standing crop. In contrast, North Hog Island is accreting sediment and the relationship between shoreline change and vegetation change breaks down (r2 = 0.14). On North Hog, which has not experienced any overwash for nearly 3 decades, the relationship between salinity and elevation is not clear and the coupling of salinity and standing crop breaks down. Because the disturbance regime on North Hog is much more infrequent than South Hog, biotic processes tend to dominate. The plants are not responding simply to moving substrate which allows for observable successional sequences on the north end of the island. Nutrient Inputs, Transformations, and Movements Continuing studies involve both translocation and transformations associated with the barrier islands, the island and mainland marshes, and the open waters between the land masses. Because few background data were available for the VCR/LTER, much initial effort was directed at evaluation of the overall nutrient status of the landscape elements. Monitoring nutrient concentrations (particularly nitrogen and phosphorous) permitted observations to be made and hypotheses to be generated. Monitoring continues, but we have entered the hypothesis testing stage as well. Standing stocks of nutrients have been assessed along the mainland to Hog Island transect. The focus of the work to date has been the marshes, marsh creeks, and lagoons. Inorganic nutrient standing stocks are generally much higher at the Phillips Creek site (mainland marsh) with maximum differences occurring during the summer period. There is an approximate 10- fold and 3-fold increase in nitrogen and phosphorus standing stock respectively between the mainland and barrier island sites. Ammonium concentrations in the mainland marshes (15 uM) were much greater than those in the ocean inlet (less than 1 uM). Nitrate values followed the same pattern, ranging from 10 -20 uM in open water, with peaks up to 50 uM in the mainland creeks. Phosphate values were also high near the mainland (about 5 uM) but less than 0.5 uM in the inlets. In situ rates of nitrification appear low compared to data for estuarine sediments in general, but differ by site at the VCR. The Cattle Shed site (barrier island marsh) appears to have higher rates than the Phillips Creek site. Denitrification measurements have proved problematic, however analytical techniques are presently being adapted for use at the VCR. A long-term (2 year) survey was completed to test the hypothesis that abundance (acridine orange direct counts), activity (turnover rate constant of radiolabeled acetate), and growth (tritiated thymidine incorporation into bacterial DNA) of bacteria were related to the position of the sampling sites in the salt marsh creek-ocean inlet gradient. Both abundance and activity generally decreased from the marshes to the open water, but were higher in the mainland marshes than in the marshes associated with the barrier islands. Expected seasonal variation was also observed. The bacterial parameters were positively associated with concentrations of nitrogen, phosphorous, and dissolved organic carbon in the water column. Comparison of these data with those obtained in a one-time survey of Chesapeake Bay marsh creeks indicate that although inorganic nutrient concentrations in the barrier-island lagoon are significantly higher than those in Chesapeake Bay, the bacterial abundance, activity, and growth rates are much lower. This suggests that nutrient cycles and controls on the cycles may be very different in the lagoon system as compared to Chesapeake Bay. We hypothesize that light limitations on phytoplankton production are responsible for the differences observed. Work is continuing this summer in an attempt to understand the controls on bacterial abundance, activity, and growth. Data from analysis of stable isotope ratios are consistent with the pool size and microbial data. In general the stable isotope ratios of similar species from the two areas were relatively close (+/- 1 ppt) in both carbon and nitrogen isotope ratios. However, a gradient definitely existed in particulate matter filtered from the water column, with samples from mainland creeks being isotopically lighter in both carbon and nitrogen than samples form Quinby Inlet (north end of Hog Island) and creeks on Hog Island. What proved to be unique was that the nitrogen isotope ratios from throughout the entire study site were isotopically heavier than any yet measured except those from Chesapeake Bay. These results may indicate a strong terrestrial input of nitrogen and that isotopic analysis of the fertilizer used by the Eastern Shore farmers and shellfish processing plant waste would prove useful in elucidating the seaside nitrogen sources. Experiments were done last summer on Hog Island to examine the relationship between the availability of nitrogen and phosphate to beach grass distribution and growth. Those data have not yet been analyzed. Some data were collected on atmospheric inputs of cations and anions on Hog Island. Those data are incomplete. Measures have been taken to insure a complete atmospheric input data set for the coming year. In addition, nitrogen mineralization measurements for soils in the myrica thickets are currently being done on a monthly basis and the response of myrica nodule nitrogen-fixation rates to salt stress are being measured in laboratory experiments. Nutrient movement between landscape elements at the VCR occurs via hydrologic transport of groundwater and general circulation of lagoon water. Tidal forces are hypothesized to be coupled to the position, salinity, and movement of the groundwater of the barrier islands. We have initiated a study to examine data on atmospheric exchanges (precipitation and evapotranspiration) and tidal forcing (water table fluctuations) in order to develop an understanding of the daily to seasonal controls of microenvironmental patterns that influence the availability of fresh and brackish water (as well as inorganic nutrients) to dune plants and barrier island fringe marsh vegetation. Initial data during a drawdown period (no rainfall) between September and October, 1990, indicate that the water table is quite dynamic; daily drawdown due to evapotranspiration ranged from 80 mm day-1 near an island pond to >100 mm day-1 in the high marsh. Damping of the drawdown near the pond was driven by recharge from the pond, while in the high marsh the higher potentiometric surfaces were represented by adjacent dunes and sea level itself. Qualitative nutrient transformation are probably not substantially different in the VCR/LTER than in other coastal lagoon landscapes. Translocations appears to be quite complex. Continued effort will be placed in tracing of nutrient movements within and between the landscape elements. Trophic Structure Trophic structure at the VCR/LTER is being examined for marsh and marsh creek organisms using stable isotopic signatures of primary producers and consumers. Carbon, nitrogen, and sulfur are utilized to trace food webs. Two questions have been addressed: 1) are there differences in stable isotope ratios of similar organisms between the mainland and the island marshes, and 2) is there a difference in the stable isotope ratio between a nitrogen-fixing and a non-fixing plant on the barrier island. Organisms sampled included the primary producers, Spartina alterniflora and Ulva lactuca; the filter-feeder, Geukensia; the deposit-feeders, Uca and Nasarrius; the omnivore, Palaemonetes; the carnivores, Caracharinus and Opsanus); and water-column particulate material. The stable isotope signatures of similar species from the mainland and barrier island were similar. This suggests similar trophic structure and little difference in the sources of inorganic nutrients for the primary producers. The spatial and temporal distribution of populations of small mammals has been and continues to be studied intensively. This project focuses on observing long-term temporal and spatial fluctuations in abundance. The project continued with additions of 1266 trap nights in July and August 1990, and 633 trap nights in early May 1991 to the data base. Both trapping sessions included existing transects T1, T2, T4, and T5 on Hog Island. On the northern transects (T1 and T2), the summer session yielded captures of Mus musculus (14 captures of 13 individuals) and Oryzomys palustris (82 captures of 45 individuals, two of which were tagged in previous trapping sessions). The spring session found decreased densities for both species (Mus, 4 captures of 4 individuals; and Oryzomys, 6 captures of 6 individuals). Densities were lowest on T2, with only a single capture of Mus recorded during the entire spring trapping session. The southern transects (T4 and T5), despite including only roughly one third as many traps as the northern transects, had comparable numbers of Mus during both trapping sessions (summer, 20 captures of 18 individuals; spring, 13 captures of 12 individuals). Oryzomys, while comprising the majority of captures during the summer (38 captures of 21 individuals), was in the minority during the spring trapping (2 captures of 2 individuals). Plans for the next year include adding information on the microhabitat of trapping stations to the database. Another small mammal project is investigating the effect of island isolation and small-mammal vagility on population stability and genetic variability. Small mammals are a potentially important trophic link in island communities and movements can play a critical role both in colonization and persistence of populations. Allozyme analysis on 108 individuals corroborated the evidence that individuals moving between islands constituted gene flow. Blood was analyzed for variability at 12 loci from individuals on Crescent, Parramore, and Revel Islands, as well as from a more isolated island and mainland site. Genetic variation was found at three of the loci: ADA, 6PGD, and SOD. Heterozygosity was lower for the most isolated population and for the smallest population. Gene flow appears to be the primary mechanism structuring the genetic composition of the island populations. Founder effects and genetic drift appear to be of secondary importance. A study documenting larval and juvenile fish community structure and habitat use of a barrier island and a mainland salt marsh was begun late this winter. It is hypothesized that juvenile and larval fish access and foraging/predator avoidance time on the marsh surface may be determined by geomorphologic and microtopographic features related to marsh developmental stage. Marshes which differ significantly in developmental stage may exhibit considerable disparity in habitat value. Bird populations and selection of nesting sites continues to be monitored on Hog, Cobb, and Little Cobb Islands. Nesting success (based on number of eggs hatching) was relatively unsuccessful for the past two summers as a result of inadequate nesting habitat and flooding of nests built just above the high water line by "northeasters". Additional information on trophic structure and bird habitat utilization will be the result of a project examining bird feeding habits on seed distribution. This project is planned for this summer. Modeling and GIS Work with Geographical Information Systems (GIS) made considerable progress this year particularly in the initiation of projects combining remote imagery, spatial statistics and geographical information systems. Callahan (NSF) and Porter developed a study that inspected the effect of differential resolution remote sensing sensors (aerial photography at 5 meter resolution, SPOT satellite data at 20 m resolution and Thematic Mapper satellite data at 30 meter resolution) to determine the effect of spatial resolution on vegetation classifications on Hog Island. The results of this study should result in at least two publications (one involving classification problems in barrier island vegetation and one involving the effects of resolution on appearance of pattern). The studies also interface with work developed by Cook and several other students to determine the fine scale pattern of grassland species along the beach front. This study involved determining the presences and absence of 4 different grass species at points 10 cm apart along a 1.5 km transect. Spatial semi-variance patterns for these species correlate well with species life history patterns (clonal species highly clumped, wind dispersed species much more evenly spaced) and imply that the dominance of one species or the other alters the spatial grain of the community and the interaction of the community with the spatial patterns of important physical processes). Analysis of these data are continuing and publications are in preparation. Shao has developed vegetation maps (at 2 meter resolution) for the spatial dynamics of Myrica from aerial photographs since 1942. This long term (50 year record of vegetation change at high spatial resolution for the entire north end of Hog Island is a unique data set (more so because it is spatial and digitized) and will be used to test a vegetation model modified from Rastetter's DUNE model. The high resolution maps indicate episodic as well as highly systematic and patterns changes in Myrica on Hog Island for the past 50 years. Data on the prior vegetation colonized by Myrica has been calculated from the overlay of vegetation maps from different years and this data is being inspected for ergodicity to see if the succession is Markovian. Data Management Data management activities are continuing. The most recent focus has been on processing the growing volume of data submitted to the database by VCR/LTER researchers. We continue to work on obtaining or developing good archival format for intersite communication of data that is machine and operating system independent. We have also been foraging links with the Computer Science Department. Anita Jones, chair of the department, and numerous students have attended presentations on scientific data management by the VCR/LTER Data Manager. Currently a computer science student is working with the VCR/LTER on developing a generalized language for checking the internal consistency of data sets. The VCR/LTER Data Manager also participated in an NSF- sponsored workshop on research data management at Kellogg Biological Station and is co-author of the chapter on computer systems. Network Activities The VCR/LTER is participating in the LTER Network decomposition experiment (LIDET). The network litter bags and wooden dowels were set out late this winter after extensive work to strengthen the litter bags and relabel the samples was done to insure that the bags would remain intact for at least several years in an estuarine system. The bags were installed at locations where VCR decomposition studies are being done. These sites include Crescent Island (rapidly accreting, young marsh), Chimney Pole marsh (old, perched lagoon marsh), barrier island fringe marsh (at the end of our vegetation transect, T2, on Hog Island), and Phillips Creek marsh (mainland marsh). NSF SGER funds were obtained for a comparative study at North Inlet LTER and the VCR/LTER of root decomposition/marsh organic matter accretion. The focus of this work is to examine relative rates of decomposition and root production (the difference equaling organic matter accumulation) in South Carolina marshes which are accreting to eroding and accreting marshes in Virginia. Litter bags are in the process of being prepared for placement and data collection (i.e., litter bag sampling) will begin in July. Investigators have been active in network related activities in the areas of climate and climate change. Activities include a paper on climate change and ecosystems dynamics at the VCR/LTER in 18000 BP for the LTER workshop on climate variability and Long-term ecological research, the establishment of an LTER Climate/Ecosystem bulletin board (in conjunction with d. Greenland), establishment of an LTER network data base with predictions of 4 US general circulation models outputs for double carbon dioxide, and work in establishing an LTER Paleoecolgy working group. APPENDICES PUBLICATIONS June 1, 1990 - May 1, 1991 Blum, L.K., and A.L. Mills. 1991. Microbial growth and activity during the initial stages (14 days) of seagrass decomposition. Mar. Ecol. Prog. Ser. 70:73-83. Bonan, G., and B. Hayden. 1990. Using a forest stand model to examine the ecological and climatic significance of the late-Quaternary pine-spruce pollen zone in Eastern Virginia, U.S.A. Quaternary Research 33:204-218. Bonan, G., and B. Hayden. 1990. Forest vegetation structure on the eastern shore of Virginia circa 18,000 B.P. Virginia J. Sci. 41:307-320. Bulger, A.J., M.G. McCormick-Ray, M.E. Monaco, D.M. Nelson, and B. Hayden. 1990. A proposed estuarine classification: analysis of species salinity ranges. Natl. Oceanic Atmosph. Adm., Natl. Ocean Service - Estuarine Living Marine Resources Project, pp. 28. Dolan, R., D.L. Inman, and B. Hayden. 1990. The Atlantic cast storm of March 1989. J. Coastal Res. 6:721-725. Garland, J., and A.L. Mills. In Press. Classification and characterization of heterotrophic microbial communities based on patterns of community-level sole carbon-source utilization. Appl. Environ. Microbiol. Hayden, B. 1990. Climate change and ecosystem dynamics at the Virginia Coast Reserve 18,000 B.P. during the last century, pp. 76-84. In Climate Variability and Ecosystem Response. Southeastern Forest Experiment Stat. Gen. Tech. Report SE- 65. Hayden, B.P., R.D. Dueser, J.T. Callahan, and H.H. Shugart. 1991. Long-term Research at the Virginia Coast Reserve. BioScience 41:310-318. Hoelscher, J.R., W.K. Nuttle, and J.W. Harvey. (accepted). Comment on "Calibration and use of pressure transducers in soil hydrology". Hydrolog. Proc. Michaels, P.J., D.E. Sappington, D.E. Stooksbury, and B. Hayden. 1990. Regional 500mb heights and U.S. 1000-500 mb thickness prior to the Radiosonde Era. J. Theoretical Appl. Climatol. 42:149-154. Porter, J.H., and R.D. Dueser. 1990. Selecting a body-mass criterion for measuring dispersal. J. Mammalogy 71:470-473. Porter, J.H., and J. Kennedy. 1991. Computer systems for data management. In G. Lauf and J. Gorentz (eds.) A report to the National Science Foundation. Shugart, H.H. 1990. Ecological models and the ecotone, pp. 23-36. In R.J. Naiman, and H. DeChampes (eds.) Ecology and Management of Aquatic Terrestrial Ecotones. Parthenon Publishing. Shugart, H.H. 1990. Using ecosystem models to assess potential consequences of global climatic change. Trends in Ecology and Evolution 5:303-307. Shugart, H.H. 1990. Modeling future changes of vegetation succes- sion, pp. 61-67. IN Symposium on Global Change Systems, American Meteorological Society, Boston, Massachusetts. Shugart, H.H., G.B. Bonan, D.L. Urban, W.K. Lauenroth, W.J. Parton, and G.M. Hornberger. 1991. Computer models and long-term ecological research, pp. 211-239. In P.R. Risser (ed.) Long-term Ecological Research and Global Change. SCOPE. John Wiley, London. Smith, T.M., H.H. Shugart, and G.B. Bonan. 1991. The use of models in predicting vegetation response to climate change. Advances in Ecological Research (in press). Urban, D.L., G.B. Bonan, T.M. Smith, and H.H. Shugart. 1991. Spatial applications of gap models. Forest Ecology and Management (in press). PRESENTATIONS Blum, L.K., and A.L. Mills. "The impact of sediment-generated dissolved organic carbon in water column oxygen demand." Amer Soc. Limnol. Oceanogr., Williamsburg, VA. Blum, L.K. "Spartina and Roots: What John Casey and Alex Haley neglected to mention." East Carolina University. Conn, C.E., and F.P. Day. "Belowground biomass allocation on a barrier island." Assoc. Southeastern Biologists, Baltimore, MD. Conn, C.E., and F.P. Day. "Belowground biomasss allocation alongh a barrier island transect." Ecological Soc. America, Snowbird, UT. Garland, J.L., and A.L. Mills. "Classification and characterization of microbial communities based on patterns of carbon source utilization." Ann. Meet. Am. Soc. Microbiol., Dallas, TX. Harvey, J.W. "Hydrological transport in wetland soils: the effect of macropores on solute exchange with surface water." USGS, Water Resources Div., Menlo Park, CA. Hayden, B. "Global Warming: What All Scientists Should Know." All Scientists Meeting of the Long-Term Research consortium of the National Science Foundation, Estes Park, CO. Hayden, B. "Global Warming: Coastal and Marine Implications." Virginia Institute of Marine Sciences, Glouster Point, VA. Hayden, B. "Storms, Waves, and Climate Change in a Warming World." Symposium: Towards a Realistic View of Global Change -- A Research Agenda, Phoenix, Arizona. Johnson, S.R., and D.R. Young. "Salt tolerance and the declining abundance of Pinus taeda on the Virginia barrier islands." Botanical Soc. Amer., Richmond, VA. Lagera, L.M., A.L. Mills, and L. K. Blum. "Comparison of nutrient distribution and bacterial activity on the Bay and seaside waters of Virginia's Eastern Shore." Ann. Meet. Am. Soc. Limnol. Oceanogr., Williamsburg, VA. Mills, A.L., L.K. Blum, and L. M. Lagera. "Distribution of bacterial abundance and activity in the Virginia Coastal Lagoon." Ann. Meet. Am. Soc. Limnol. Oceanogr., Williamsburg, VA. Porter, J.H., and J.L. Dooley. "Movement distributions: fact or artifact?" Ecological Soc. Amer., Snowbird, UT. Porter, J.H. "Small-mammal Dispersal: Social Causes and Population Consequences." Old Dominion University, Norfolk, VA. Porter, J.H. "Data Management at the Virginia Coast Reserve LTER." Computer Science Department, University of Virginia, Charlottesville, VA. Sande, E., and D.R. Young. "Effects of NaCl on the growth and nitrogen fixation characteristics of Myrica cerifera." Ecological Soc. Amer., Snowbird, UT. Sande, E., and D.R. Young. "Salt stress depression of growth and nitrogen fixation characteristices in Myrica cerifera." Botanical Soc. Amer., Richmond, VA. Shugart, H.H. "Modeling Future Changes of Vegetation Succession", 1990 American Meteorological Society Symposium on Global Change Systems, Anaheim, CA. Shugart, H.H. "Long-term Vegetation Change Models." Climate Systems Modeling Program, National Center for Atmospheric Research, Boulder, CO. Shugart, H.H. "Terrestrial Vegetation Response to Global Climate Change." 1990 Society of Automotive Engineers Government/Industry Meeting, EPA sponsored. Shugart, H.H. "Forest Dynamics Models at Serveral Spatial Scales." SCOPE: Sustainable Use of Land in Latin America, paper presented, Santiago, Chile. Shugart, H.H. "Modeling Forest Response to Climatic Change", TERRAVision Project, Battelle Pacific Northwest Laboratories. Shugart, H.H. "Global Warming: How do we know?", Environment 2000: Issues and Questions, Francis Marion College. Shugart, H.H. "Climate Change and Forest Dynamics." World Climate Conference, Geneva, Switzerland. Shugart, H.H. "Computer Modeling of Forest Ecosystems." Ecosystems Modeling Workshop, Ecosystems Center, Woods Hole Marine Biological Laboratory. Young, D.R. "Photosynthetic relations of the evergreen, actinorhizal shrub, Myrica cerifera." Ecological Soc. Amer., Snowbird, UT.