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Poster Abstracts: Gulf Coast Science Conference
1: Understanding Ecosystems
A Statistical Methodology for Conservation Science
James B. Grace, U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
It is little appreciated that the univariate model (e.g. ANOVA, multiple regression), which is the cornerstone of conventional approaches to the design of studies and analyses of data, is not well suited for the study of systems. Rather, conventional hypothesis testing methodology has been designed for studying individual processes and is not suited to evaluating hypotheses about complex systems. Structural equation modeling (SEM) is a method for addressing causal hypotheses about simultaneous interactions among the components of a system and, in contrast, is specifically designed for learning about systems using multivariate data. So that the potential utility of this methodology can be better realized, we are working towards development and application of a more complete set of tools for SEM for use in the ecological and conservation sciences. To accomplish this overall goal, three synergistic activities are being undertaken: (1) methodology development, (2) comprehensive applications to select conservation issues, and (3) exploratory applications. Here we demonstrate the utility of SEM for experimental studies relevant to the real world of complex, large-scale conservation science.
Contact Information: James Grace, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd, Lafayette, LA 70506; phone: 337 266 8632; email: gracej@usgs.gov
SELVA-MANGRO: Landscape Model for South Florida Mangrove Ecosystems
Thomas W. Doyle and Ken Krauss
U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
A landscape simulation model, SELVA-MANGRO, was developed for mangrove forests of south Florida to investigate the potential impacts of climate change on the quality and distribution of mangrove habitat. The SELVA-MANGRO model represents a hierarchically integrated landscape model that manages the exchange of system parameters up, down, and across scale between linked simulation models SELVA and MANGRO. SELVA is a Spatially Explicit Landscape Vegetation Analysis model that tracks predicted changes in the biotic and abiotic conditions of each land unit (1 sq ha) on an annual basis for the entire simulated landscape. The SELVA model administrates the spatial articulation of landscape units composed of habitat classifications (forest, marsh, aquatic) and any forcing functions that predict changes in hurricane activity, sea-level rise, and freshwater runoff. Intertidal forest units are then simulated with the MANGRO model based on unique sets of environmental factors and forest history. MANGRO is an individual (agent) based, spatially explicit stand simulation model constructed for mangrove forests of the neotropics. It is composed of a set of species-based functions for predicting the growth, establishment, and death of individual trees. MANGRO predicts the tree and gap replacement process of natural forest succession as influenced by stand structure and environmental conditions. SELVA-MANGRO has been used to evaluate the role of hurricane history and frequency on forest structure and composition and to predict mangrove migration upslope and displacement of freshwater habitats under rising sea levels projections from climate change.
Contact Information: Tom Doyle, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, Louisiana 70506; phone: 337-266-8647; fax: 337-266-8586; email: doylet@usgs.gov
The Vulnerability of Tidal Freshwater Forests of the Southern United States to Changing Climate and Rising Sea Level
Thomas W. Doyle, William H. Conner, and Kenneth W. Krauss
U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
Coastal forests along the Gulf of Mexico and south Atlantic are currently undergoing dieback and decline from increasing tidal inundation, saltwater intrusion, and altered freshwater flow attributed to global climate change and variability. Much of the impact on tidal freshwater swamps and maritime forest is within federal and state parks and refuges without any monitoring activity to document current and future land cover change. Baseline field research has been initiated to understand the process and pattern of forest dieback and habitat conversion that may be altering carbon flux and storage. Tidal freshwater swamps of the Gulf and Atlantic reaches are subject to different hydrogeomorphic settings, tidal amplitudes, drought and hurricane frequencies, subsidence rates, and streamflow volumes which, in part, account for varying degrees of salinity exposure and dieback conditions on a local and regional basis. Droughts and hurricanes are major natural factors that influence the extent and concentration of saltwater distribution that contributes to forest dieback in coastal zones. Field sites in eastern Louisiana show the impact of Hurricane Rita (2005) which inflicted a storm surge and salt pulse spanning hundreds of miles to the east of landfall. Field studies in South Carolina and Louisiana demonstrate that forest complexity and productivity are negatively correlated with residual interstitial soil salinities in these coastal cypress forests of the southern United States. Projected sea-level rise and changing climate is expected to accelerate the processes and extent of saltwater intrusion that will further impact freshwater swamp habitats and restoration efforts in the absence of adaptive coastal management.
Contact Information: Ken Krauss, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, Louisiana 70506; phone: 337-266-8882; fax: 337-266-8586; email: kkrauss@usgs.gov
Monitoring the Impact of a Hydrologic Restoration Project on Vegetation of the Ten Thousand Islands Region in Southwest Florida
Rebecca J. Howard, Richard H. Day, Ken W. Krauss, and Thomas W. Doyle
U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
The Ten Thousand Islands region of southwest Florida is characterized by a complex of mangrove forests and salt, brackish, and fresh marsh habitats that have been hydrologically modified since the 1940’s, leading to changes in vegetation community structure. At Ten Thousand Islands National Wildlife Refuge (TTI NWR), marsh habitat area has decreased while mangrove forest area has increased. This study documents more recent vegetation change resulting from the U.S. Army Corps of Engineers’ Picayune Strand Restoration Project (PSRP), which attempts to restore historical hydrologic regimes to the Ten Thousand Islands region. Three monitoring stations consisting of two permanent 50-m long transects were established in fall 2007 in each of three marsh types (fresh, brackish, and ecotone marsh) at TTI NWR; the nine stations had previously been equipped with continuous water-level recorders. Additional transects were established as controls at five sites outside the PSRP impact area. Species cover was estimated to the nearest 5% at six 0.5-m2 quadrats along each transect, as was number and height for woody species within a 100-m2 wide belt. Analysis using multi-response permutation procedures (MRPP) indicated separation between the three marsh types at TTI NWR (P = 0.00, A = 0.16). Three separate control groups were also identified by using MRPP (P = 0.00, A = 0.26). Indicator species analysis identified species associated with each of the six vegetation groups. Long-term monitoring will identify future shifts in plant community composition, providing information on the link between specific hydrologic characteristics and vegetation response.
Contact Information: Rebecca Howard, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd, Lafayette, LA 70506; phone: 337 266 8639; email: howardr@usgs.gov
Stress Tolerance in Eurasian versus U.S. Gulf of Mexico clones of Phragmites australis
Rebecca J. Howard1 and Steven E. Travis2
1 U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
2 University of New England, Biddeford, Maine
The competitive ability and stress tolerance of the Eurasian haplotype of Phragmites australis have been cited as probable causal factors in the expansion of this lineage in North American wetlands. To test this idea, we conducted greenhouse experiments measuring growth of P. australis individuals collected in Louisiana. We analyzed chloroplast DNA and found that the plants represented both the gulf coast (I) and Eurasian (M) haplotypes. Salinity, water depth and soil type were manipulated in two experiments, which included clones of both haplotypes. Growth was affected by all factors, and several interactions between factors were identified. Stem height of both I and M clones was significantly decreased in salinities of 10 and 18 psu compared to freshwater; no difference between haplotypes was evident. When grown in a commercial soil mix, M clone biomass was lower than that of I clones in stressful conditions (deeper water, higher salinity). However, M clones had greater stem density and height than I clones in organic and silt soils, but not in clay soils, regardless of salinity. The study suggests that growth of both haplotypes in response to interactive stressors is complex, and that invasiveness of the Eurasian haplotype may be related to soil characteristics.
Contact Information: Rebecca Howard, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd, Lafayette, LA 70506; phone: 337 266 8639; email: howardr@usgs.gov
Landscape-Scale Modeling for Bird-Habitat Relations: Science Support for the Gulf Coast Joint Venture
Wylie Barrow, Jr.1, Lori Randall1, James Grace1, William Vermillion2, Barry Wilson2, Robert Diehl3
1 USGS National Wetlands Research Center, Lafayette, Louisiana
2 Gulf Coast Joint Venture, Lafayette, Louisiana
3 University of Southern Mississippi, Hattiesburg, Mississippi
All migratory birds are designated as trust species in North America and are managed and protected by the Department of the Interior (DOI) as mandated in the Migratory Bird Treaty Act of 1972. There is now compelling evidence that the populations of many of these trust species have declined over the past forty years due to a variety of disruptions (e.g., habitat conversion, pollution, invasive species) occurring throughout their geographic range. Each year millions of landbirds migrate across or near the coast of the Gulf of Mexico moving between breeding and wintering grounds. During migration seasons, nearly all of the migratory landbird species of the Eastern United States, as well as some western species, stopover on the coastal plains along the northern and western Gulf of Mexico. Historically, these spatial dynamics of landfall were not a problem for migrants because forests and woodland patches were numerous and widespread. But during the past 300 years, human development, agriculture, and the spread of exotic/invasive plants have destroyed or degraded most coastal forest systems. The synergistic effects of these well-established population stresses and projected climate change present a daunting challenge to the Gulf Coast Joint Venture (GCJV), Department of Interior (DOI) land managers, and policy makers. The Gulf Coast Joint Venture is a regionally based, biologically driven, bird habitat conservation partnership of federal, state, and private organizations working within the coastal portions of Mississippi, Alabama, Louisiana, and Texas. To meet GCJV information needs to guide habitat conservation activities, we are using a combined Doppler radar, remote sensing, and structural equation modeling (SEM) approach to better understand bird habitat relations at multiple spatial and temporal scales (see Figure 1. for an example of radar data integrated with National Land Cover Data). By using SEM we can study path networks and understand the multiple processes controlling the system (Figure 2.). In particular, we will use SEM to assess the relative strength and the direct and indirect nature of the causal relations among geographic position, human development, habitat, and migrant landbird use.
Contact Information: Wylie Barrow, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd, Lafayette, LA 70506; phone: 337 266 8668; email: barroww@usgs.gov
Persistence and Implications of Storm Deposits From Hurricane Wilma in the Mangrove Forests Along the Southwest Coast of Everglades National Park, Florida USA
Gordon H. Anderson1, Karen M. Balentine2, Ginger Tiling2, and Thomas J. Smith III1
1 U.S. Geological Survey, Florida Integrated Science Center, St. Petersburg, Florida, USA
2 Jacobs Technology Inc., St. Petersburg, Florida, USA
On October 24, 2005, Hurricane Wilma made landfall on the southwest coast of Florida. A 3-5 m storm surge transported large volumes of fine-grained marine carbonate sediment from the Gulf of Mexico into the coastal mangrove forests and estuaries of Everglades National Park. There is evidence of hurricane storm deposits in the geologic record from previous storm events. However, the extent and thickness of Hurricane Wilma’s deposits may only be exceeded in recent history by Hurricane Donna (1960). We measured Wilma storm deposits every year since 2005 at sites along the Shark and Harney Rivers. We observed possible physical and biological factors which may contribute to the persistence or loss of storm related deposition. Immediately post-Wilma, we observed average storm sediment depths of 6.6 cm at downstream Shark River site (SH3) and 4.6 cm at Harney River mid-reach site (SH4). Storm sediments at SH3 decreased by 11% (5.9 cm) in 2006 and by 32% (4 cm) in 2007. Storm deposits at SH4 decreased initially by 30% (3.2 cm) in 2006, but increased slightly to (3.6 cm) in 2007, suggesting local remobilization of storm sediments. Storm deposit layers of varying thickness are found in the geologic record are indicative of their persistence in the coastal Everglades. Consequently, what physical and biological factors may influence storm sediment stabilization or erosion? In sediment loss, we hypothesized rainfall erosion remobilized sediment particles and transported them into surface drainage rills whereas, riverbank levees restricted and contained storm sediments in the forest. Important biological factors influencing storm sediment stabilization are: the post-storm mangrove rootlet growth into storm sediment which bound storm sediment to underlying peat sediment; the presence of ground cover vegetation and mangrove prop roots which reduced sediment re-suspension and mobilization; and, the reworking of storm sediment which incorporated the storm sediments into mangrove peat by crab bioturbation. The persistence of storm deposits along the tidal rivers of the southwest mangrove coast of the Everglades may have several important implications to the coastal Everglades ecosystem. Specifically, increased riverbank levee elevation may buffer the effects of sea-level rise, and reduce tidal-flooding frequencies. This may increase forest water residence time by restricting local overland flow and tidal outflow into the estuaries. Reduced flooding frequency and impounded forest overland waters could alter nutrient and salt flux between the forest sediment and river, potentially influencing the local primary productivity of the forest.
Contact Information: Gordon Anderson, USGS-FISC Everglades Field Station, 40001 SR 9336, Homestead, FL 33034, USA, Phone 305-242-7891, Fax 305-242-7836, Email: gordon_anderson@usgs.gov
Coastal Forests and Migratory Birds: Broad-Scale Response of Landbird Migration to the Impacts of Hurricanes.
Wylie Barrow, Jr., Stephen Faulkner, Brady Couvillion, Robert Diehl, Lori Randall, Robert Dobbs, Clint Jeske, and Tommy Michot
U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
Many species of landbirds that breed in North America migrate over the western Atlantic Ocean or the Gulf of Mexico to winter in the West Indies, Central America, or South America. Because the continent-wide pattern of migration concentrates these migrants in relation to ecological barriers, such as the Gulf of Mexico, forests of the river deltas along the northern Gulf of Mexico have been identified as stopover sites or staging areas of special concern to migratory landbirds. These coastal forests serve as habitat that migrating landbirds use to rest and replenish energy reserves before continuing migration. Autumn bird migration (August-October) coincides with the peak of hurricane season in the Gulf of Mexico, and hurricanes are known to frequently occur where high densities of migrating birds are staging prior to gulf crossings. At a broad-scale, we tested the hypothesis that historic preference by migrants for bottomland hardwoods habitat was altered after Katrina’s passage because the hurricane caused disproportionate damage to bottomland hardwoods. As a consequence, we predicted migrants either 1) shifted their stopover distribution toward non-bottomland hardwood habitat (the less favored mixed pine uplands) or 2) avoided the entire landscape altogether. Response of migrant birds stopping over in the Pearl River bottomland hardwoods just after Katrina’s landfall and up to several weeks after hurricane passage was to increase their use of the surrounding less-disturbed, pine-dominated woodlands. About five weeks after Katrina, much of the surviving forest canopy in the Pearl River bottoms began to resprout new foliage, and we observed a corresponding increase in migrant use of the bottomland hardwoods. These redistributions could be related to changes in vegetation structure or loss of food and foraging substrates. Results from our research after Hurricane Rita suggest that reduction in food resources is an important factor in driving broad redistributions of migrants stopping over in hurricane-altered landscapes.
Contact Information: Wylie Barrow, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd, Lafayette, LA 70506; phone: 337 266 8668; email: barroww@usgs.gov
Marsh to Mangroves: Consequences of Habitat Change in Louisiana Estuaries
Richard H. Day1, Chris J. Wells1, Thomas W. Doyle1, Thomas C. Michot1, Lawrence R. Handley1, Brian J. Milan2,and Richard F. Shaw2
1 U.S. Geological Survey, National Wetlands Research Center, Lafayette, Louisiana
2 Coastal Fisheries Institute, Louisiana State University, Baton Rouge, Louisiana
Black mangrove (Avicennia germinans L.) is the most cold-hardy mangrove species bordering the Gulf of Mexico and the only one that persists along the coast of Louisiana, where mangroves reach their northernmost extent. Avicennia at Fourchon, Louisiana, has historically been characterized as a low shrub because of periodic diebacks caused by recurring freezes. Recovery after a hard freeze is by basal sprouting and seedling recruitment from propagules. After almost 20 years without a hard freeze (since December 1989), mangrove stands at the Fourchon site have reached tree stature (over 4m) and are expanding rapidly. Black mangrove replacement of salt marsh is especially evident in areas of recent Spartina alterniflora L. dieback. Growth of individual mangroves has been monitored in recent years and increases in height and diameter are evident. Areal coverage of mangrove habitat has been increasing significantly based on analysis of historic aerial photography. Conversion of marsh to mangrove affects the source of the estuarine detrital food chain and availability of fisheries nursery/refugia habitat. Statistically significant differences in species assemblages of fish have been observed at the mangrove/water edge versus the marsh/water edge. This research suggests that periodicity of freezes could augment major changes in vegetation and faunal communities of Louisiana estuaries.
Contact Information: Richard H. Day, U.S. Geological Survey, National Wetlands Research Center, 700 Cajundome Blvd., Lafayette, Louisiana 70506; phone: 337-266-8557; fax: 337-266-8586; email: dayr@usgs.gov
Winter Roost Sites of Western Burrowing Owls in Coastal Texas
Marc C. Woodin1, Mary Kay Skoruppa1, Damon Williford2, and Jennifer L Keppers2
1 United States Geological Survey, Texas Gulf Coast Field Research Station, Corpus Christi, Texas
2 Department of Life Sciences, Texas A&M University-Corpus Christi, Corpus Christi, Texas
Coastal Texas provides a diversity of habitats, including estuaries, lagoons, tidal flats, grasslands, and wooded riparian corridors, that are important to hundreds of bird species. These habitats offer refuge to endangered species (e.g., whooping cranes, piping plovers, and Attwater’s prairie chickens), provide critical stopover habitat for coastal and trans-gulf migrants, and are the final destination of migrants arriving on their winter ranges in coastal Texas. From 1999-2004, we investigated the winter ecology of western burrowing owls, a declining subspecies which winters in grasslands and farmlands of the Texas coastal plains and on barrier islands. Our objectives were to: 1) describe winter roost sites, 2) examine selection of artificial burrows, and 3) determine extent of roost site fidelity. We located owl roosts by presence of feathers, feces, regurgitated pellets, and flushing of roosting owls. For each roost site, we assigned habitat type (grassland, farmland, woodland, barrier island); roost site type (culvert, natural burrow, other); and measured diameter of openings. Of 46 roost sites we located, 40 (87%) were in agricultural areas. Three were in grasslands, and three were on barrier islands. Thirty-four (74%) were at culverts, whereas only five were natural burrows. Mean diameter of openings was 22 ± 1.5 cm (SE). To determine burrowing owl use of artificial burrows, we installed 72 artificial burrows of polyethylene tubes (18 at each of four different sites) in southern Texas: 1) in grasslands at Naval Air Station-Kingsville, Naval Auxiliary Landing Field Orange Grove, and at Welder Wildlife Foundation near Sinton, and 2) in vegetated dunes on Mustang Island. All burrows were 2.4 m long and covered with soil. At each site, three clusters of six tubes each, all in an east/west orientation, were installed. Each cluster of six artificial burrows had two tubes of each of three sizes (15-, 20-, and 25-cm diameters). We monitored owl use for two winters. Burrowing owls occupied burrows at the barrier island site and the Orange Grove site. Burrowing owls preferred (46 of 58 detections) small-diameter burrows (P = 0.05). To examine roost site fidelity, we trapped and banded 15 burrowing owls, which we monitored during subsequent winters. Of the 15 owls, 8 (53%) returned the next winter, and three (20%) for the third winter, to the same roost site at which they were banded.
Contact Information: Marc Woodin, U.S. Geological Survey, Corpus Christi, TX 78412; phone: 361 985 6266; email: marc_woodin@usgs.gov
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