Robert F Stallard
Robert Stallard has been at the USGS since 1987 and is now a Scientist Emeritus in the Hydro-Eco Interactions Branch of the Earth Systems Processing Division of the USGS Water Resources Mission Area.
Robert Stallard has been at the USGS since 1987 and is now a Scientist Emeritus in the Hydro-Eco Interactions Branch of the Earth Systems Processing Division of the Water Mission Area. He studies how land-cover and climate change affect water movement through soils, weathering, and erosion, and how these, in turn, affect the composition and dispersal of dissolved and solid phases in rivers and trace gases in the atmosphere. Areas of expertise include surface-water hydrology, major element and nutrient biogeochemistry, soil formation and sediment genesis, vegetation-landscape interaction, carbon-cycle characterization on land and in the ocean, and assessment of land-use and climate change. His work has included the study of natural and human-altered landscapes, in the Americas, Southeast Asia, and Africa, including large parts of the Amazon, Orinoco, Mississippi, and Panama Canal Basins and eastern Puerto Rico.
Most of his current efforts are committed to a multi-catchment investigations designed to distinguish the roles of vegetation, climate, and land-cover change and to put this in a hydrologic and biogeochemical framework as well as to examine ecosystem costs and services focusing on water, carbon, and biodiversity. Two projects currently consume most of his USGS time: (1) Work related to the Luquillo USGS Water, Energy, and Biogeochemical Budget (WEBB) Project in eastern Puerto Rico and parallel work in Panama, which has as a goal the comprehensive assessment of catchment hydrology and biogeochemistry in a hydrologically energetic landscapes. (2) The Agua Salud Project in the Central Panama Canal Basin examines the manifold effects of different styles of reforestation as compared to mature forested and deforested catchments. The project started in 2008 and involves 13 small watersheds with different land covers.
EDUCATION
- National Research Council Post-Doctoral Fellowship: 1981, At the U.S. Geological Survey - Office of Marine Geology, Woods Hole, MA. Clay mineralogy of the Amazon River system.
- Ph.D., Chemical Oceanography: 1980, Massachusetts Institute of Technology - Woods Hole Oceanographic Institution Joint Program in Oceanography. Ph.D. thesis entitled "Major Element Geochemistry of the Amazon River System."
- B.S., Earth & Planetary Sciences: 1974, Massachusetts Institute of Technology. Emphasis in Planetary Physics and Chemistry.
Science and Products
A unified assessment of hydrological and biogeochemical responses in research watersheds in Eastern Puerto Rico using runoff-concentration relations
Effect of land cover and use on dry season river runoff, runoff efficiency, and peak storm runoff in the seasonal tropics of Central Panama
How old is the Isthmus of Panama?
Hydrology and climate of four watersheds in eastern Puerto Rico: Chapter C in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Weathering processes in the Rio Icacos and Rio Mameyes watersheds in Eastern Puerto Rico: Chapter I in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Physiography, geology, and land cover of four watersheds in eastern Puerto Rico: Chapter A in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Weathering, landscape equilibrium, and carbon in four watersheds in eastern Puerto Rico: Chapter H in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Land use, population dynamics, and land-cover change in eastern Puerto Rico: Chapter B in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Effects of earthworms on slopewash, surface runoff, and fine-litter transport on a humid-tropical forested hillslope in eastern Puerto Rico: Chapter G in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Landslides and sediment budgets in four watersheds in eastern Puerto Rico: Chapter F in Water quality and landscape processes of four watersheds in eastern Puerto Rico
The low-latitude regions of the Earth are undergoing profound, rapid landscape change as forests are converted to agriculture to support growing population. Understanding the effects of these land-use changes requires analysis of watershed-scale geomorphic processes to better inform and manage this usually disorganized process. The investigation of hillslope erosion and the development of sediment
Atmospheric inputs to watersheds of the Luquillo Mountains in eastern Puerto Rico: Chapter D in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Water quality and mass transport in four watersheds in eastern Puerto Rico: Chapter E in Water quality and landscape processes of four watersheds in eastern Puerto Rico
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A unified assessment of hydrological and biogeochemical responses in research watersheds in Eastern Puerto Rico using runoff-concentration relations
An examination of the relation between runoff rate, R, and concentration, C, of twelve major constituents in four small watersheds in eastern Puerto Rico demonstrates a consistent pattern of responses. For solutes that are not substantially bioactive (alkalinity, silica, calcium, magnesium, sodium, and chloride), the log(R)–log(C) relation is almost linear and can be described as a weighted averagAuthorsRobert F. Stallard, Sheila F. MurphyEffect of land cover and use on dry season river runoff, runoff efficiency, and peak storm runoff in the seasonal tropics of Central Panama
A paired catchment methodology was used with more than 3 years of data to test whether forests increase base flow in the dry season, despite reduced annual runoff caused by evapotranspiration (the “sponge-effect hypothesis”), and whether forests reduce maximum runoff rates and totals during storms. The three study catchments were: a 142.3 ha old secondary forest, a 175.6 ha mosaic of mixed age forAuthorsFred L. Ogden, Trey D. Crouch, Robert F. Stallard, Jefferson S. HallHow old is the Isthmus of Panama?
The Standard Model of the formation of the Isthmus of Panama proposes that final closure occurred at 4–3 Ma. The model is based on evidence from studies of marine stratigraphy, fossil sequences, divergent molecular phylogenies, the timing of the Great American Biological Interchange (GABI), and proxies for marine paleosalinity, paleobathymetry, productivity, and paleotemperatures. The new model usAuthorsAnthony G Coates, Robert F. StallardHydrology and climate of four watersheds in eastern Puerto Rico: Chapter C in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Puerto Rico lies directly in the path of the easterly trade winds, which deliver steady rainfall to the mountains and steer tropical wave systems toward the island. Hurricanes and tropical storms derived from these tropical waves differ in frequency and intensity, contributing to substantial interannual variation in precipitation and stream discharge. Puerto Rico's steep topography and small waterAuthorsSheila F. Murphy, Robert F. StallardWeathering processes in the Rio Icacos and Rio Mameyes watersheds in Eastern Puerto Rico: Chapter I in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Streams draining watersheds of the two dominant lithologies (quartz diorite and volcaniclastic rock) in the Luquillo Experimental Forest of eastern Puerto Rico have very high fluxes of bedrock weathering products. The Río Blanco quartz diorite in the Icacos watershed and the Fajardo volcaniclastic rocks in the Mameyes watershed have some of the fastest documented rates of chemical weathering of siAuthorsHeather L. Buss, Arthur F. WhitePhysiography, geology, and land cover of four watersheds in eastern Puerto Rico: Chapter A in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Four watersheds with differing geology and land cover in eastern Puerto Rico have been studied on a long-term basis by the U.S. Geological Survey to evaluate water, energy, and biogeochemical budgets. These watersheds are typical of tropical, island-arc settings found in many parts of the world. Two watersheds are located on coarse-grained granitic rocks that weather to quartz- and clay-rich, sandAuthorsSheila F. Murphy, Robert F. Stallard, Matthew C. Larsen, William A. GouldWeathering, landscape equilibrium, and carbon in four watersheds in eastern Puerto Rico: Chapter H in Water quality and landscape processes of four watersheds in eastern Puerto Rico
The U.S. Geological Survey's Water, Energy, and Biogeochemical Budgets (WEBB) program research in eastern Puerto Rico involves a double pair-wise comparison of four montane river basins, two on granitic bedrock and two on fine-grained volcaniclastic bedrock; for each rock type, one is forested and the other is developed. A confounding factor in this comparison is that the developed watersheds areAuthorsRobert F. StallardLand use, population dynamics, and land-cover change in eastern Puerto Rico: Chapter B in Water quality and landscape processes of four watersheds in eastern Puerto Rico
We assessed current and historic land use and land cover in the Luquillo Mountains and surrounding area in eastern Puerto Rico, including four small subwatersheds that are study watersheds of the U.S. Geological Survey's Water, Energy, and Biogeochemical Budgets (WEBB) program. This region occupies an area of 1,616 square kilometers, about 18 percent of the total land in Puerto Rico. Closed forestAuthorsWilliam A. Gould, Sebastián Martinuzzi, Isabel K. Pares-Ramos, Sheila F. Murphy, Robert F. StallardEffects of earthworms on slopewash, surface runoff, and fine-litter transport on a humid-tropical forested hillslope in eastern Puerto Rico: Chapter G in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Rainfall, slopewash (the erosion of soil particles), surface runoff, and fine-litter transport were measured in tropical wet forest on a hillslope in the Luquillo Experimental Forest, Puerto Rico, from February 1998 until April 2000. Slopewash data were collected using Gerlach troughs at eight plots, each 2 square meters in area. Earthworms were excluded by electroshocking from four randomly selecAuthorsMatthew C. Larsen, Zhigang Liu Liu, Xiaoming ZouLandslides and sediment budgets in four watersheds in eastern Puerto Rico: Chapter F in Water quality and landscape processes of four watersheds in eastern Puerto Rico
The low-latitude regions of the Earth are undergoing profound, rapid landscape change as forests are converted to agriculture to support growing population. Understanding the effects of these land-use changes requires analysis of watershed-scale geomorphic processes to better inform and manage this usually disorganized process. The investigation of hillslope erosion and the development of sediment
AuthorsMatthew C. LarsenAtmospheric inputs to watersheds of the Luquillo Mountains in eastern Puerto Rico: Chapter D in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Twenty years of precipitation-chemistry data from the National Atmospheric Deposition Program site at El Verde, Puerto Rico, demonstrate that three major sources control the composition of solutes in rain in eastern Puerto Rico. In order of importance, these sources are marine salts, temperate contamination from the Northern Hemisphere, and Sahara Desert dust. Marine salts are a source of roughlyAuthorsRobert F. StallardWater quality and mass transport in four watersheds in eastern Puerto Rico: Chapter E in Water quality and landscape processes of four watersheds in eastern Puerto Rico
Water quality of four small watersheds in eastern Puerto Rico has been monitored since 1991 as part of the U.S. Geological Survey's Water, Energy, and Biogeochemical Budgets program. These watersheds represent a montane, humid-tropical environment and differ in geology and land cover. Two watersheds are located on granitic rocks, and two are located on volcaniclastic rock. For each bedrock type, oAuthorsRobert F. Stallard, Sheila F. Murphy