B11B-0139 0800h
Heavy Metal Contamination and Salt Efflorescence Associated With Decorative Landscaping Rocks, Las Vegas, Nevada: The Need for Regulations
Las Vegas, Nevada is one of the fastest growing cities in the United States. Faced with water restrictions, decorative rock xeroscaping has become a very popular form of landscaping. Currently, there are no regulations controlling the geochemistry of the decorative rocks that can be used for these purposes. In this study, we examined three sites containing two different decorative rock products. The landscaping rocks, underlying soil, and surface salt crusts were analyzed to determine their mineralogy and chemistry. Methods of analysis include scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP), thin section analysis, and laser particle size analysis (LPSA). Preliminary results indicate the presence of halite (NaCl), bloedite (Na$_{2}$Mg(SO$_{4}$)$_{2}$ 4H$_{2}$O), a hydrated magnesium sulfate, and possibly copper sulfate and copper chloride mineral phases in the surface salt crusts. Both copper minerals are regarded as hazardous substances by the Occupational Safety and Health Administration (OSHA) and the Environmental Protection Agency (EPA); these agencies have established minimum exposure limits for human contact with these substances. Copper sulfate and copper chloride are not naturally occurring minerals in the soils of the Las Vegas Valley, and analyses indicate that their formation may be attributed to the mineralogy of the decorative landscaping rocks. Further testing is needed to characterize this potential health hazard; however the preliminary results of this study demonstrate the need for regulations controlling the geochemistry of decorative rocks used for urban landscaping.
B11B-0140 0800h
Fire quality and gas chemical property of Indonesian biomass burning
Indonesian forest fire caused not only by natural climate condition but also by human activities are great concerning for South East Asian countries on both environment problem and socio-economic matter. In this report, fire quality and chemical properties emitted from various types of biomass burning in this region are focused on. Our obtained fire quality datum sets on fire temperature and trace gas concentrations by several times of fire experiment in Sumatra and Kalimantan through 1999 to 2001 are compared previous this kind of reports mainly based on IPCC report. Emission ratio of CO and CH4 per CO2 (CO/CO2 and CH4 / CO2 are almost fitted by Modified Combustion Efficiency (MCE) which was defined by Yokelson et al., although fire categories are significantly different in vegetation types and fire temperatures, On the other hand, emission factor of N2O, CH3Br, CH3I, and CH3Cl are not clearly fitted by MCE value.
B11B-0141 0800h
The ENSO-fire Dynamic in Insular Southeast Asia
We examined the spatiotemporal patterns of fire in insular Southeast Asia from July 1996-December 2001 using a set of consistent, nighttime fire observations provided by the Along Track Scanning Radiometer (ATSR) sensor. Monthly ATSR fire counts were analyzed relative to georeferenced climatic and land-cover data from a variety of sources. We found that fires were strongly correlated with Southern Oscillation Index (SOI) (r = -0.75) and Nino 3.4 index (r = 0.72) in forested land-cover types within the equatorial belt (-5.5 to 5.5 degrees). Cross-correlation analysis revealed that detrended SOI was modestly correlated (r = 0.42) with detrended monthly fire count with a positive lag of four months. However, our analysis also revealed that fire counts reached their maximum six months before the absolute maximum of SOI. Annual sums of SOI and fire counts revealed linearity for annual SOI sum less than zero. Overall, the results suggest that ENSO indices may have limited predictive utility at a monthly time scale, but that temporal aggregation and additional fire observations may enhance our capacity to forecast fires in different cover types based on ENSO data.
http://www.as.miami.edu/geography
B11B-0142 0800h
Landscape Change Priorities at the U.S.Geological Survey, 2005-2015
In February 2004 the U.S. Geological Survey (USGS) convened a Science Planning Team with a charge to create a succinct strategy to define, organize, manage, and expand the scientific activities of the Geography Discipline over the next 10 years (2005-2015). Over the ensuing months the Team has held listening sessions in five cities, meeting with 150 scientists and science managers from inside and outside the USGS to gain understanding of the strategic science issues and opportunities for the Geography Discipline. In a draft of the science plan the Science Planning Team has identified 10 priority science goals in three areas of societal interest: landscape change, the societal impacts of landscape change, especially related to hazards, environment, and natural resources, and the development, management, and access to geospatial information. Landscape change is a primary focus of the strategy and includes goals to (1) describe and understand the status of the nation's land surface and how is it changing; (2) describe and understand the local, regional, national, and global drivers of change; (3) predict the likely landscape changes over the next 20-50 years; and (4) describe and understand the consequences of landscape change on human and environmental systems. The critical steps identified to realize these goals are: development of a land use history of North America; development of periodic assessments of land cover responses associated with regional to global drivers, including economic globalization; development of a local to regional-scale land cover forecasting capability; and assessment of biodiversity and habitat consequences associated with landscape changes at the boundaries between human settlements and less developed areas. In most cases successful outcomes associated with these actions will require collaboration with scientists from the USGS, other government agencies, universities, and non-governmental organizations. As part of the implementation of the plan, a USGS Land Cover Institute is proposed that would include a strong focus on landscape change and the addition of at least 20 doctoral-level researchers. The final plan is expected to be released in January 2005.
http://nc.water.usgs.gov/geog_spt/
B11B-0143 0800h
Tropical Forest Protection, Uncertainty, and the Environmental Integrity of Carbon Mitigation Policies
Tropical forests are estimated to release approximately 1.7 PgC per year as a result of deforestation. Avoiding tropical deforestation could potentially play a significant role over the next 50 years if not longer. Many policy makers and negotiators are skeptical of our ability to reduce deforestation effectively. They fear that if credits for avoided deforestation are allowed to replace fossil fuel emission reductions for compliance with Kyoto, the environment will suffer because the credits will not reflect truly additional carbon storage. This paper considers the nature of the uncertainties involved in estimating carbon stocks and predicting deforestation. We build an empirically based, stochastic, model that combines data from field ecology, GIS data from satellite imagery, economic analysis and ecological process modeling to simulate the effects of these uncertainties on the environmental integrity of credits for avoided deforestation. We find that land use change, and hence additionality of carbon is extremely hard to predict accurately and errors in the numbers of credits given for avoiding deforestation are likely to be very large. We also find that errors in estimation of carbon storage could be large and could have significant impacts. We find that in Costa Rica, nearly 42 percent of all the loss of environmental integrity that would arise from poor carbon estimates arises in one life zone, Tropical Wet. This suggests that research effort might be focused in this life zone.
B11B-0144 0800h
A Simple and Effective Image Normalization Method to Monitor Boreal Forest Change in a Siberian Burn Chronosequence across Sensors and across Time
Satellite data offer unique perspectives for monitoring and quantifying land cover change, however, the radiometric consistency among co-located multi-temporal images is difficult to maintain due to variations in sensors and atmosphere. To detect accurate landscape change using multi-temporal images, we developed a new relative radiometric normalization scheme: the temporally invariant cluster (TIC) method. Image data were acquired on 9 June 1990 (Landsat 4), 20 June 2000, and 26 August 2001 (Landsat 7) for analyses over boreal forests near the Siberian city of Krasnoyarsk. Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), and Reduced Simple Ratio (RSR) were investigated in the normalization study. The temporally invariant cluster (TIC) centers were identified through a point density map of the base image and the target image and a normalization regression line was created through all TIC centers. The target image digital data were then converted using the regression function so that the two images could be compared using the resulting common radiometric scale. We found that EVI was very sensitive to vegetation structure and could thus be used to separate conifer forests from deciduous forests and grass/crop lands. NDVI was a very effective vegetation index to reduce the influence of shadow, while EVI was very sensitive to shadowing. After normalization, correlations of NDVI and EVI with field collected total Leaf Area Index (LAI) data in 2000 and 2001 were significantly improved; the r-square values in these regressions increased from 0.49 to 0.69 and from 0.46 to 0.61, respectively. An EVI cancellation effect where EVI was positively related to understory greenness but negatively related to forest canopy coverage was evident across a post fire chronosequence. These findings indicate that the TIC method provides a simple, effective and repeatable method to create radiometrically comparable data sets for remote detection of landscape change. Compared with some previous relative normalization methods, this new method can avoid subjective selection of a normalization regression line. It does not require high level programming and statistical analyses, yet remains sensitive to landscape changes occurring over seasonal and inter-annual time scales. In addition, the TIC method maintains sensitivity to subtle changes in vegetation phenology and enables normalization even when invariant features are rare.
B11B-0145 0800h
Impacts of Land Use on Wetland Vegetation in the Eastern United States: Timing and Scale
The timing and scale of vegetation change are dependent on the resilience of the ecosystem to land use change that alters hydrologic response and sediment transport. Using palynological methods, we examine the impacts of land use change in 2 distinct ecosystems (the subtropical Florida Everglades and the temperate Roanoke River floodplain) in the Eastern United States. Twentieth century water management strategies have modified the hydrology within the Florida Everglades resulting in varying degrees of vegetation changes depending on community type and location within the greater Everglades ecosystem. Analysis of pollen assemblages from herbaceous wetland communities such as sawgrass ridges, open water sloughs, and marl prairies, show rapid vegetation change in response to both increases and decreases in hydrology. However, evaluations of these wetland environments over longer time periods (centuries to millennia) and through natural alterations to hydroperiod (like Medieval Warm Period) demonstrated the ability of the vegetation to recover within a few decades. Tree-island communities, composed of flood-intolerant, woody vegetation, are largely resistant to decreases in hydroperiod. They are, however, less tolerant to sustained increases (greater than 5 years) in water levels, with no seasonal drying, resulting in long-term degradation. Tree-island pollen assemblages indicate rapid changes in vegetation composition when subjected to prolonged hydroperiod (essentially drowning the tree islands). Pollen assemblages from the Roanoke River floodplain provide a perspective on the impacts of colonial land clearance, altered sedimentation, and changes in flooding regimes on forested wetland vegetation. After land clearance, organic to mineral sediments covered organic floodplain soils. Palynological evidence suggests a change towards less flood tolerant communities in areas of greatest sedimentation. These results demonstrate the rapid response of wetland plant communities to alterations in hydrology and sedimentation as a result of land use changes. Comparisons of modern records with paleoecological records provide a tool to evaluate the scale and timing of wetland vegetation response to land use change.
B11B-0146 0800h
Effects of Urbanization on the Condition of Streams in the Piedmont of North Carolina: Responses of Benthic Macroinvertebrate Assemblages
The effects of urbanization on the physical, chemical, and biological characteristics of streams in the North Carolina Piedmont were investigated as part of the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program. Over 1,200 candidate basins (2-3rd order streams) were identified using a 30-m digital elevation model. A multimetric urban intensity index (UII) derived from population, infrastructure, land use, land cover, and socioeconomic factors was used to characterize the degree of urbanization in each basin. Candidate basins were grouped together based on natural features (e.g., ecoregion, elevation, relief, and soil characteristics) and a subset of 30 basins was selected for study on the basis of uniformity in natural features, representation of the urban gradient (i.e., low to high UII), and accessibility. Biological (fish, benthic macroinvertebrates, and algae), physical (stream stage, temperature, and habitat), and chemical (nutrients, pesticides, and major ions) characteristics were measured in each stream and related to changes in the UII. Biological responses were assessed using multivariate (i.e., assemblage ordinations) and multimetric (i.e., assemblage metrics) methods. The relations between invertebrate responses, the UII, and characteristics of urbanization are described in this paper. These relations were examined using correlations and regressions. Invertebrate assemblages exhibited strong responses to the UII based on ordination site scores (Y = -0.013X + 1.613, R$^{2}$ = 0.78, P $<$ 0.001) and assemblage metrics (e.g., EPT richness Y = -0.165X + 17.004, R$^{2}$ = 0.78, P $<$ 0.001 and richness-based tolerance Y= 0.013X + 5.047, R$^{2}$ = 0.75, P $<$ 0.001). The relations between invertebrate responses and UII were linear and did not show any initial resistance to urbanization. Response rates in the North Carolina Piedmont were similar to response rates reported for the Boston, MA (ordination -0.016, EPT richness -0.268, tolerance 0.015), Birmingham, AL (ordination -0.017, EPT richness -0.168, tolerance 0.015), and Salt Lake City, UT (ordination -0.012, EPT richness -0.169, tolerance 0.021) metropolitan areas based on previous NAWQA Program urban gradient studies. The characteristics of urbanization most strongly associated with degradation of invertebrate assemblages were road density, percentage of population in urban areas, density of households, percentage of basin in developed lands, percentage of basin in urban/recreational grasses, percentage of stream buffer in urban land cover, percentage of homes with utility-supplied natural gas, and density of toxic-release inventory sites. Characteristics associated with high-quality invertebrate assemblages were percentage of basin in forest, percentage of basin in agricultural grasslands, percentage of stream buffers in forest, percentage of stream buffers in agricultural grasses, percentage of homes fueled with bottled gas, and percentage of owner-occupied homes. These driving factors were similar to the factors that were important in NAWQA Program urban gradient studies conducted in Boston, Birmingham, and Salt Lake City indicating a strong commonality in urban effects across the US.
http://nc.water.usgs.gov/albe/General/ulug/index.html
B11B-0147 0800h
Evidence for a significant urbanization effect on climate in China
China has experienced rapid urbanization and dramatic economic growth since its reform process started in late 1978. In this article, we present evidence for a significant urbanization effect on climate based on analysis of impacts of land-use changes on surface temperature in southeast China, where rapid urbanization has occurred. Our estimated warming of mean surface temperature of 0.05\deg C per decade attributable to urbanization is much larger than previous estimates for other periods and locations. The spatial pattern and magnitude of our estimate are consistent with those of urbanization characterized by changes in the percentage of urban population and in satellite-measured greenness.
B11B-0148 0800h
Trajectories of Vegetation Change Under Controlled Land-use in Sudanian West Africa
Land cover dynamics in Sudanian West African savannas are complex functions of climate variability, human migration, and increasingly intensive land-uses. The Nouhao Valley Project land management area in southeast Burkina Faso provides a large-scale natural experiment (2000 km$^{-2}$) in which pastoral and agricultural land-uses are controlled in demarcated, contiguous zones. Abandoned more than 20 years, the Nouhao Valley was resettled by plan in 1984, after the eradication of Onchocerciasis (River Blindness). Pastoralists and agriculturalists were allocated and now occupy separate Project lands; adjacent areas are mixed use (control). Quantitative satellite analyses at the regional and landscape scale reveal that policy-driven land-uses significantly alter the long-term trajectory of riparian cover in a pattern distinct from climatic regional variability. Local patterns of land-use change are overprinted on climatic variability. Trends of primary productivity, derived from the AVHRR instrument, show that while the greater region has recovered gradually after the early 1980s droughts (10 g C m$^{-2}$ y$^{-2}$ in the control area), the pastoral region of the Nouhao Valley experienced relatively enhanced growth (19 g C m$^{-2}$ y$^{-2}$). A multi-temporal spectral mixture analysis of five Landsat TM scenes, spanning the period 1984-2002, indicate that the broad increase in green vegetation abundance is similar in open savannas across all land-use types, but highly contrasted in forest galleries and riparian areas. Trajectories of green vegetation areal abundance reveal that open savanna (20-60% tree and shrub) increased by an average of 5-10% from 1984-2002 over all land-uses; forests became more vegetated by 20-30% in pastoral areas, but only 7-10% in the agriculture and control areas. Large areas in the agricultural region experienced wide-spread loss of riparian forests. The sharp contrast between the land-cover dynamics of pastoral and agricultural land-uses is significant in savanna ecosystem services management. This remote sensing approach focuses future ground-based studies towards precise drivers of change in savanna riparian areas; differentiating the degree of forest loss, riparian growth, or shrub encroachment is critical to understanding long-term sustainability.
http://porter.geo.brown.edu/~jfisher/
B11B-0149 0800h
Urbanization, Forest Vulnerability and Resource Land Loss in the Chesapeake Bay Watershed
The contemporary pattern of urban development in industrialized countries is increasingly taking the form of low density, decentralized residential and commercial development. In the Chesapeake Bay watershed, which is located within the mid-Atlantic region of the United States, dispersed development patterns have been linked to habitat fragmentation and declining water quality. Our objectives were to document how this urbanization process has expanded throughout the watershed and to explore how lands comprising the natural resource base, particularly forests, have been replaced by a matrix of the built environment. We accomplished this by mapping impervious surface cover (houses, roads, etc) across the ~168,000 km2 area using a time series of satellite imagery. We calculated metrics of land use change and used these to estimate the loss of resource lands across the region. We conservatively estimate that 334 km2 of forest, 888 km2 of agriculture and 2 km2 of wetlands have been converted to impervious surfaces between 1990 and 2000. We also used the time series to calibrate a spatial model of urban land use change, and forecasted future development patterns in Maryland out to 2030 under different policy scenarios. Using Maryland Department of Natural Resources' (DNR) Strategic Forest Lands Assessment (SFLA), which evaluates forest resources in terms of their economic and ecologic value, and Maryland's Green Infrastructure, which identifies ecologically valuable patches of contiguous forests and wetlands, we evaluated the vulnerability of natural resources in Maryland. Threats associated with loss and fragmentation were identified.
http://www.whrc.org
B11B-0150 0800h
Effects of Urban Development on Water-Quality in the Piedmont of North Carolina-- The NAWQA Urban Land-Use Gradient Study
A study of urban basins located in the Piedmont of North Carolina is underway as part of the U. S. Geological Survey National Water-Quality Assessment (NAWQA) to determine the relation between level of urban development and water quality. Data were collected from 30 basins on water chemistry (nutrient, pesticide, and ion concentrations), geomorphic and habitat characteristics, hydrologic stage, discharge, water temperature, pH, dissolved-oxygen concentration, specific conductance, benthic algae, invertebrate communities, and fish communities. Collection frequency for water chemistry ranged from 2 samples (at 20 sites) to 6 samples (at 10 sites). Biological data were collected in each basin twice. Investigation of the effects of urbanization on water quality must control for the effects of natural factors, while varying the degree of urbanization between study basins. A regional framework was used to control variability in natural factors that influence water-quality. The urban intensity in each basin was measured by using an index to integrate information on human influences. The Urban Index includes information about land cover, infrastructure, population, and socioeconomic characteristics. Sites were selected to represent the full gradient of undeveloped to fully urbanized basins. A preliminary review of the stream water-chemistry data indicates distinct relations between ionic composition and the Urban Index. Mean specific conductance was positively correlated with the Urban Index (Spearman correlation coefficient (r) = 0.77; 95-percent confidence limits (95CL) 0.61 - 0.93; probability (pr) $<$0.0001; N=30). Specific conductance ranged from 56 microsiemens (uS) at the least developed site to 607 uS at the most developed site. Dissolved sulfate (r=0.74; 95CL 0.57 - 0.91; pr $<$0.0001) and chloride (r=0.71; 95CL 0.52 - 0.90; pr $<$0.0001) were also positively correlated with the Urban Index. Sulfate ranged from 2.3 to 66 milligrams per liter (mg/L), and chloride ranged from 3.5 to 96 mg/L. Urban sources of sulfate include domestic sewage and emissions from the combustion of automotive and diesel fuels. Sources of chloride include sewage and road salting. pH was positively correlated with the Urban Index (r=0.60; 95CL 0.38 - 0.84; pr= 0.0005) with a range from 6.5 at the least urban site to 7.5 at the most urban site. The increase in pH may be due in part to conversion of organic forest soils to less acidic soils of urban lawns. The overall trend of increasing total dissolved nitrogen (r=0.46; 95CL 0.12 - 0.80; pr=0.0103) and nitrite plus nitrate (r=0.46; 95CL 0.09 - 0.83; pr=0.0109) concentrations, with increasing Urban Index may reflect sources such as sewage and lawn fertilizer use in the more urban basins. However, some of the least urban basins also had elevated nitrogen concentrations reflecting possible agricultural influences such as fertilizer use and animal waste. Total nitrogen concentration ranged from 0.31 to 14 mg/L. Unit-area stream discharge during low-flow periods was negatively correlated with the Urban Index (r= -0.56; 95CL -0.74 - -0.37; pr=0.0014). Reduced discharge with greater urban development may be a result of reduced infiltration caused by impervious surfaces. Unit discharge ranged from 0.47 to 2.27 cubic feet per second per square mile of drainage area.
http://nc.water.usgs.gov/albe/General/ulug/index.html
B11B-0151 0800h
Trace Elemental Analyses of Suspended Sediments in the San Francisco Estuary and its Tidal Marshes
This research evaluates the trace elemental compositions of inorganic sediments in the San Francisco Bay estuary marshes over space and time. These sediments create and maintain the tidal marshes that surround the Sand Francisco Bay, yet a thorough analysis of the sources of these sediments remains understudied. Determining the sources of sediments is of interest because current mitigation and restoration projects around the Bay must consider whether the sediment supply will be sufficient for projects, or if opening diked wetlands to tidal flow will result in salt water intrusion further up-estuary (into the Delta). Results of trace element analyses of suspended sediments that pass through the Sacramento-San Joaquin Delta (the Delta) are compared with those of local watershed tributaries. Differences in bedrock lithology can be seen in the varying trace elemental concentrations; for example, K, Nd, Sm, Rb and Sr concentrations are significantly lower in the Sacramento river sediments than those of the San Joaquin river and can be used to differentiate further the Delta input. Results from marsh surface samples throughout the North Bay and preliminary results from 4 1-m long sediment cores collected along a transect of the Novato creek marsh (NCM) reflect local versus Delta sediment source patterns. The suspended sediment samples from the Sacramento and San Joaquin rivers and from local creeks reflect the end members of the sediment supply for local marshes. The marsh surface samples represent the most recent period (last few years or so) and reflect the extent of Delta influence into the estuary. Finally, the cores collected from the Novato creek marsh provide details on the gradient of dominant source supply (i.e., are the sediments well inland predominantly from the local watershed and how far does that influence extend downstream), as well as a history of how the sediment supply conditions have changed, comparing pre-Gold Rush and agriculture era (before about 150 years) to post.
B11B-0152 0800h
MONITORING THE PHILIPPINE FOREST COVER CHANGE USING NDVI PRODUCTS OF REMOTE SENSING DATA
The Philippines has one of the world's fastest disappearing forest cover, which is being lost to natural processes and landscape-modifying human activities. Currently, forested landscape covers 24% (i.e., 7.2 million hectares) of the Philippines' total land area, of which only 800,000 hectares are considered as old-growth forests. Occasionally, volcanic activities and earthquakes cause large-scale impacts on the forest cover, but the systematic reduction of the country's forest has been sustained through unregulated logging operations and other human-induced landscape modification. Reforestation and watershed protection have become important public policy programs as forest denudation is linked to recent devastating landslides, debris flows and flashfloods. However, many watershed areas that are at risk to deforestation are hardly accessible to ground-based monitoring. A spaced-based monitoring system facilitates an efficient and timely response to changes in the quality and extent of the Philippine forest cover. This monitoring system relies in the generation of Normalized Difference Vegetation Index (NDVI) products from the red and infrared bands of remote sensing data, which correlates with the amount of chlorophyll in the vegetation. Given the existing forest classification maps, non-forested regions are masked in the data analysis, so that only forest-related changes in the vegetation are shown in the NDVI image difference products. A combination of two MODIS-bearing satellites, i.e., Terra and Aqua, acquire high temporal and moderate spatial resolution data, enabling the countrywide detection of vegetation changes within a certain observation period. MODIS data are calibrated for setting the pixel quality thresholds, which minimize the artifact of clouds and haze in the analysis. Areas showing dramatic changes are further investigated using higher resolution data, such as ASTER and Landsat 7 ETM. Sequential NDVI products of remote sensing data provide improved spatial information for the assessment of a natural disaster, warning of potential hazardous situations, detection of illegal forest-clearing activities and management of the reforestation effort.
B11B-0153 0800h
Human Influence on the Carbon Cycle in Secondary Tropical Forests
Recently it has been proposed that reforestation of tropical pasture lands may be an effective way to sequester CO2, but the effects of re-forestation on the soil C pool are not well known. In an attempt to gain a better understanding of the soil C dynamics during the process of tropical forest re-growth, soil samples were collected from active pasture and 10, 30, and 80 year-old secondary forest, in the Cayey region of Puerto Rico. We are conducting a long term incubation experiment to determine the effects of future climate change and atmospheric N deposition on soil CO2 effluxes and the relative importance of pasture or forest source C in soil C losses. Pasture soils exhibited the highest rates of soil respiration, followed by the secondary forests, which tracked closely under all treatments except N addition. There were few effects of added N on CO2 effluxes; the 80 year-old forest showed the lowest rates of soil CO2 efflux under N additions. In contrast, CO2 fluxes were consistently higher in soils at elevated temperature relative to the controls. In the re-growing forests, C-13 isotope data reveal that warming also increased the proportion of C3 derived C as opposed to C4 (i.e., old pasture) derived-C in respiration. After two months of incubations, no effect of warming on 13-CO2 was seen in pasture sites. Our results indicate that soil C pools in re-growing tropical forests are highly sensitive to temperature, but soil C losses do not appear to be responsive to added N.
B11B-0154 0800h
Landscape and Vegetative Influences on Mercury in Forest Litter at Acadia National Park
Litterfall, or leaves and other matter that falls from the forest canopy to the forest floor, is a predominant vector of mercury (Hg) deposition to forested watersheds. Leaves, the primary component of litterfall, primarily accumulate atmospheric Hg by diffusive vapor exchange through stomata. Vegetative and non-vegetative factors dictate Hg accumulation in foliage. This research examines the influence that factors such as vegetation type, aspect, elevation and canopy coverage have on the concentration of total-Hg in litterfall in two study watersheds in Acadia National Park (ANP), Maine, U.S.A. Litterfall was measured at 39 sites, spanning 14 months, in paired gauged watersheds with ongoing Hg monitoring. Initial results suggest that the annual flux of Hg in litterfall exceeds the magnitude of other input vectors of wet or dry deposited Hg by a factor of two. Vegetation type influenced mass of litter (mean \pm SD), which was greater at deciduous sites (12.2 g/mo \pm 10.8) than at coniferous sites (5.7 g/mo \pm 3.8). The annual flux of Hg in litterfall will be quantified and compared to Hg in wet-only precipitation and throughfall. Litterfall Hg flux will be compared for each landscape and vegetation factor to test the hypothesis that the quantity of litterfall ultimately controls the flux of litterfall Hg.
B11B-0155 0800h
Understanding the contributions of the biophysical and the human built environments on avian biodiversity
Ecological theory suggests that the potential for biodiversity varies across the continent as determined by biophysical factors. Ecosystem energy, for example, sets an upper limit on species richness. Intensive human land use is now widespread over North America and likely reduces biodiversity below the biophysical potential. The goal of this study is to understand the contributions of the biophysical environment and the human built environment in structuring bird biodiversity across North America and to concurrently evaluate the use of MODIS land products to test these hypotheses. The study is designed to greatly improve our understanding of biodiversity potential across the continent, quantify how land use has altered biodiversity from this potential, and to prioritize places within and among physiographic ecoregions in conservation importance. Preliminary results for the US Pacific Northwest indicate that the MODIS land surface products explained between 38% and 48% of the variation in land bird Shannon's diversity. The best multivariate model from these factors included mean and variation in net primary productivity and normalized difference vegetation index. This model explained 58% of the variation in Shannon diversity. When climate variables were added to the candidate models, the best model explained 64% of the variation. This pilot analysis demonstrates that MODIS products are significant predictors of bird diversity, and will add substantially to our ability to quantify patterns of association with biophysical factors. Additionally, recently developed land use change data will allow analyses of human land use impacts to understand its role. The study will rigorously test current and new scientific theory on controls on biodiversity, evaluate the utility of eight MODIS and AMSR-E products for understanding and mapping avian biodiversity at regional to continental scales, provide the first maps of biodiversity potential across the continent and the first quantitative assessment of how land use modifies biodiversity from this natural potential, and finally provide land mangers tools for prioritization of conservation valuable lands.
B11B-0156 0800h
Assessing the effect of human-induced land degradation on ecosystem function in the former homelands of South Africa
The communal homelands in north-eastern South Africa, created during the apartheid-era, are widely regarded as severely degraded as a result of human utilization. The impacts of degradation on net primary production (NPP) were studied using a time-series (1985 to 2003) of Advanced Very High Resolution Radiometer (AVHRR) NDVI and modeled NPP data for degraded rangelands identified by the National Land Cover (using Landsat TM imagery) and non-degraded rangelands within the same land capability units (LCUs). The NPP of degraded areas was significantly lower than in non-degraded parts of most of the LCUs and the difference between degraded and non-degraded areas did not diminish in years with high rainfall, although NPP in degraded areas in wet years exceeded that of non-degraded areas in drier years. Thus degraded areas had the same resilience as non-degraded areas. The Rain-Use Efficiency (RUE) of degraded areas (NPP per unit rainfall) was also consistently lower than non-degraded areas. The persistence of the effect on the NPP indicated that the degradation is stable at the time scale of 18 years. These results indicate that, while there has not been a catastrophic reduction in ecosystem function within the former homelands, degradation results in a stable state with reduced productivity and RUE. The results highlight the importance of multi-temporal analyses of ecosystem function to understanding land degradation and illustrate how long time-series of terrestrial data might be used in a national land degradation monitoring system.
B11B-0157 0800h
Microbial Community Structure Responses to Long-Term Acid-Mine Drainage Contamination in a Coastal Salt Marsh
Constructed wetlands for in situ bioremediation of metals and acid mine drainage (AMD) require the activity of sulfate-reducing bacteria (SRB) to sequester dissolved metals into metal-sulfide precipitates (e.g. Webb et al. 1998). Factors such as low pH and high dissolved [Cu] will constrain the growth of SRB (Sani et al. 2001). Unintentional stimulation of the growth of sulfuric acid-generating microbes, such as Thiomicrospira, would also decrease bioremediation efficiency. Few studies of natural wetlands under long-term forcing by AMD and metals have been performed. We characterized the microbial diversity, mineralogy and geochemistry of a contaminated salt marsh at the Richmond Field Station along the East San Francisco Bay. For over 50 years, this marsh has received pH$\sim$2, metal-rich groundwaters from near-surface pyrite tailings and paint and explosives manufacturers. Sediment cores (30-40 cm long) were taken from contaminated sites with pH $\sim$2 and $\sim$8. Whole-sediment analyses showed As, Cd, Cu, Se, Zn, and Pb are present at 100s of ppm (URS Corp. 2001). ICP-AES analyses of pore waters showed 10-50 ppb As. All cores contained fine-grained black muds and exhibited a noticeable sulfide odor. Transmission electron microscope studies of marsh sediments support the sequestration of metals into aggregates of nanocrystalline sulfides. Isotopic analyses of pore-water sulfate taken at several depths within cores of AMD pool (SMR-1) and tidal slough sediments (SM148-1) at pHs 2-3 and 7-8, respectively, all yielded significant negative $\delta$34S values (-25 to -35 $\permil$) consistent with bacterial sulfate reduction. However, values of the upper 10 cm of SMR-1 are roughly 10 $\permil$ heavier than seawater and support a significant contribution of dissolved sulfate from direct oxidation of pyrite tailings. 16S gene clone libraries revealed significantly different microbial community structures in cores SMR-1 and SM148-1. Roughly 40% of the library from SMR-1 consisted of {\it Thiomicrospira denitrificans} (22%) and several other bacteria capable of oxidizing reduced sulfur species (18%). SRB were present (15%), however, and probably reflect contributions from core depths at which acidity is attenuated by tidal flushing. In contrast, SM148-1 contained $\sim$25% SRB, and aero- and halo-tolerant SRB were enriched from this core by cultivation. The dominance of {\it Thiomicrospira} and other sulfur-/sulfide-oxidizing bacteria, in combination with isotopic results, showed microbially-mediated pyrite oxidation in SMR-1. In contrast, {\it Desulfobacterium} spp. dominated the community in SM148-1 and reduced dissolved metals to near or below EPA action levels. References: Webb et al. 1998, J. Appl. Microbio., 84, 240-248; Sani et al. 2001, Applied Env. Microbio., 67, 4765-4772; URS Corp. 2001, Report 51.09967067.00.