Publications

Old-growth forests have traditionally been considered negligible as carbon sinks because carbon uptake has been thought to be balanced by respiration. We show that the top 20-centimeter soil layer in preserved old-growth forests in southern China accumulated atmospheric carbon at an unexpectedly high average rate of 0.61 megagrams of carbon hectare-1 year-1 from 1979 to 2003. This study suggests t

Increasingly, data from multiple sensors are used to gain a more complete understanding of land surface processes at a variety of scales. Although higher-level products (e.g., vegetation cover, albedo, surface temperature) derived from different sensors can be validated independently, the degree to which these sensors and their products can be compared to one another is vastly improved if their re

The Landsat suite of satellites has collected the longest continuous archive of multispectral data of any land-observing space program. From the Landsat program's inception in 1972 to the present, the Earth science user community has benefited from a historical record of remotely sensed data. However, little attention has been paid to ensuring that the data are calibrated and comparable from missi

We examine the carbon balance of North American wetlands by reviewing and synthesizing the published literature and soil databases. North American wetlands contain about 220 Pg C, most of which is in peat. They are a small to moderate carbon sink of about 49 Tg C yr-1, although the uncertainty around this estimate is greater than 100%, with the largest unknown being the role of carbon sequestratio

Urbanization has become the dominant form of landscape disturbance in parts of the United States. Small streams in the Piedmont region of the eastern United States support high densities of salamanders and are often the first habitats to be affected by landscape-altering factors such as urbanization. We used US Geological Survey land cover data from 1972 to 2000 and a relation between stream salam

Data from multiple sensors must be used together to gain a more complete understanding of land surface processes at a variety of scales. Although higher-level products derived from different sensors (e.g., vegetation cover, albedo, surface temperature) can be validated independently, the degree to which these sensors and their products can be compared to one another is vastly improved if their rel

NASA’s Experimental Advanced Airborne Research Lidar (EAARL) is a raster-scanning, waveform-resolving, green-wavelength (532 nm) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor records the time history of the return waveform within a small footprint (20 cm diameter) for each laser pulse, enabling characterization of vegetation cano

This paper discusses US Air Force, US Army, US Navy, and NASA demonstrations based around the Virtual Mission Operations Center (VMOC) and its application in fielding a Multi Mission Satellite Operations Center (MMSOC) designed to integrate small satellites into the inherently tiered system environment of operations. The intent is to begin standardizing the spacecraft to ground interfaces needed t

Leveling surveys across Medicine Lake volcano (MLV) have documented subsidence that is centered on the summit caldera and decays symmetrically on the flanks of the edifice. Possible mechanisms for this deformation include fluid withdrawal from a subsurface reservoir, cooling/crystallization of subsurface magma, loading by the volcano and dense intrusions, and crustal thinning due to tectonic exten

The 10-km-wide caldera of the historically active Aniakchak volcano, Alaska, subsides ∼13 mm/yr, based on data from 19 European Remote Sensing Satellite (ERS-1 and ERS-2) interferometric synthetic aperture radar (InSAR) images from 1992 through 2002. The pattern of subsidence does not reflect the distribution of pyroclastic deposits from the last eruption in 1931 and therefore is not related to co

Interferometric synthetic aperture radar (InSAR) imagery documents the consistent subsidence, during the interval 1992–1999, of a pyroclastic flow deposit (PFD) emplaced during the 1986 eruption of Augustine Volcano, Alaska. We construct finite element models (FEMs) that simulate thermoelastic contraction of the PFD to account for the observed subsidence. Three-dimensional problem domains of the F

Shishaldin Volcano, a large, frequently active basaltic-andesite volcano located on Unimak Island in the Aleutian Arc of Alaska, had a minor eruption in 1995–1996 and a VEI 3 sub-Plinian basaltic eruption in 1999. We used 21 synthetic aperture radar images acquired by ERS-1, ERS-2, JERS-1, and RADARSAT-1 satellites to construct 12 coherent interferograms that span most of the 1993–2003 time interv