Robert Stallard

General: I am interested in the earth-surface environment and how it changes on human and geologic time scales. Currently, I focus on the study of climate and land-use changes and how these affect processes that control the composition and dispersal of dissolved and solid phases in rivers and trace gases in the atmosphere. I work for the US Geological Survey - Water Resources Discipline- National Research Program as Project Chief of the Sediment-Water Chemistry in Large Rivers Project. I am a Research Scientist at both the Institute of Arctic and Alpine Research at the University of Colorado, Boulder and the Smithsonian Tropical Research Institute in the Republic of Panama. I am a graduate faculty advisor at the Department of Geological Sciences of the University of Colorado, Boulder, and at the Department of Geological Sciences of the University of Oregon, Eugene. In all venues, I seek collaborations and student advisees. In addition, I employ students in my laboratories on the East Campus of the University of Colorado and Barro Colorado Island in the Republic of Panamá.

Recent research efforts: focused on areas: (1) global-scale process research involving biogeochemistry and geomorphology with a focus on terrestrial sedimentation and the carbon cycle, (2) research related to the Luquillo USGS Water, Energy, and Biogeochemical Budget (WEBB) Project in eastern Puerto Rico and parallel work in Panama, (3) biogeochemical implications of event-type processes at the hillslope to small-watershed scale, focusing on fire-flood sequences and landslides, (4) biogeochemical implications of glacial erosion, (5) the life cycle of the giant Amazon water lily, (6) intercomparison of soils, nutrients, and plants in forest-dynamics research plots of the global tropics, and (7) the Neotropical amphibian die-off
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Education: 1970-1974, Massachusetts Institute of Technology, B.S. Earth and Planetary Sciences, emphasis in Planetary Physics and Chemistry. 1975-1980, Massachusetts Institute of Technology - Woods Hole Oceanographic Institution Joint Program in Oceanography, Ph.D., emphasis in Chemical Oceanography, with a thesis entitled "Major Element Geochemistry of the Amazon River System." 1980-1981, USGS-GD-Office of Marine Geology, Woods Hole, MA, National Research Council Post Doctoral Fellowship, research project on clay mineralogy.

Professional Experience: 1981-1987: Assistant Professor, Department of Geological and Geophysical Sciences, Princeton University. Research in low-temperature geochemistry, emphasizing relating geomorphic and biologic processes to the chemistry of solid and dissolved phases in rivers and soils. 1987-present: Hydrologist (Research Biogeochemist), USGS-WRD-National Research Program. Project chief, Sediment-Water Geochemistry in Large River Systems. Research on geomorphic and biogeochemical processes that control the chemistry of solid and dissolved phases in rivers, including the effects of land-use change. 1998-present: Research Scientist, Institute for Arctic and Alpine Research (INSTAAR), University of Colorado, Boulder, CO. 1997-present: Research Associate, Smithsonian Tropical Research Institute (STRI), Balboa, Republic of Panama.

Research: Biogeochemistry and physics of weathering, erosion, transport, and deposition involving natural and human-influenced landscapes. Rivers sculpt the landscape, nourish ecosystems and agriculture, and convey erosion products and human wastes to depositional sites or to the ocean. We imperfectly understand how the compositions of river-borne materials are controlled, because these materials are affected by a complex ensemble of highly linked chemical, biological, and physical processes. In developed river systems, human activities greatly increase the complexity. Changes in land use are particularly important, because these affect not only the composition of river-borne materials but also the exchange of trace gases with the atmosphere. The problem is to develop comprehensive and integrated descriptions of these processes in a form that is useful to researchers in many disciplines. This work combines both field and theoretical studies using the tools of geology, biogeochemistry, geography, hydrology, and more.

I am currently pursuing several areas of investigation: (1) Can we develop general physically and biologically based models of the processes that generate the dissolved and particulate load in rivers and trace substances in the atmosphere? (2) How do various phases chemically partition during transport in rivers and estuaries? (3) What are the dispersal pathways of river-borne substances through rivers and estuaries into the coastal environment? (4) How do human activities, particularly land-use change, affect environments being examined? (5) How do we use rivers to integrate phenomena at local spatial scales up to continental scales? (6) Can we formulate provenance models to reconstruct past geologic environments?

My work on river systems follows a basic design. I identify key phenomena by combining simple biogeochemical-process models with models of hillslope and fluvial transport. Models are then interpreted considering knowledge of the watershed obtained from diverse sources. For an entire river system I assemble chemical, geological, geomorphic, biological, and demographic data. This combines field work with analysis of available maps and public-domain data bases. Phenomena that are especially important in controlling the composition of phases containing the important crustal, nutrient, atmospheric, and indicator elements (Al, B, Be, C, Ca, Cl, F, Fe, Ge, H, K, Mg, Mn, N, Na, O, P, S, Si, Sr, Ti, Zr) are identified to provide the conceptual framework for solving specific research objectives. Solid, dissolved, and gas phases are considered. As part of these investigations, I undertake field surveys, design sampling and analytical procedures, and create computer tools to manipulate and model data. Where necessary, smaller-scale field or laboratory studies are formulated to aid data interpretation.

At the global scale, I am modeling terrestrial sedimentation and biogeochemical cycles. This involves integration of data from my studies with information from innumerable standard and grey-literature sources. Recent developments in database design--especially Geographic Information Systems (GIS)--and hillslope hydrologic models have increased the sophistication of this endeavor. Presently, I am exploring the possibilities of linking satellite data and digital topography into geochemical models using GIS.

Much of my current research focuses on the biogeochemical and geomorphic effects of global-scale environmental, climate, and land-use change in tropical and temperate environments. Temperate settings are the part of the Earth that has experienced the greatest effects of land-use change, while the tropics are now undergoing especially rapid growth involving a typically impoverished population. In this context, I have pioneered the study of the effects of land-use change on a regional scale, and have led the USGS in initiating programs in this arena. Since 1990, I have organized and am leading two large, interlinked, multidisciplinary studies concerned with the land-use change. The first project is part of the USGS Water, Energy, and Biogeochemical Budgets (WEBB) Project in eastern Puerto Rico that is also officially linked to parallel work in central Panama. The second program took several years to develop, starting in early 1993, and is now an Inter-Divisional research program now called the Mississippi Basin Carbon Project (MBCP). In addition to design and implementation of these projects, I have had to prepare substantial new theoretical infrastructure needed to interpret data (Larsen and others, 1992; Stallard, 1995a,b, 1998; Brown and others, 1995, 1998). In 1999, I started collaboration with Robert Meade and others in an examination of the life cycle of the giant Amazon water lily, Victoria amazonica (formerly Vitoria regia) as a charismatic-plant metaphor for the understanding of natural and human processes affecting the Amazon River floodplain (várzea). Most resently, I have worked with collaborators in tropical biology to obtain National Science foundation funding (1) to initiate a cross-site compapison of the interactions of hydrology, soils, nutrients, and plants the forest-dynamics research plots of the Center for Tropical Forest Science in Panamá, Ecuador, Brazil, Malaysia, Thailand, and Sri Lanka, and (2) to establish a research network to study the Neotropical amphibian die-off. This is called RANA ("Research and Analysis network for Neotropical Amphibians" or "Red de Análisis sobre anfibios Neotropicales Amenazados").

Recent Research Efforts (to find out more, click on effort):

• Global-scale process research involving biogeochemistry and geomorphology with a focus on terrestrial sedimentation and the carbon cycle.
• Luquillo USGS Water, Energy, and Biogeochemical Budget (WEBB) Project in eastern Puerto Rico and parallel work in Panama.
• Biogeochemical implications of event-type processes at the hillslope to small-watershed scale, focusing on fire-flood sequences and landslides.
• Biogeochemical implications of glacial erosion.
• The life cycle of the giant Amazon water lily.
• Intercomparison of soils, nutrients, and plants in forest-dynamics research plots of the global tropics.
• The Neotropical amphibian die-off (RANA)
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