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Ana M. B. Nunes and John O. Roads

features such as the South American low-level jet (SALLJ), which is characterized by an increase of the horizontal wind speed at lower-troposphere levels along the eastern part of the Andes. Transport of moisture from the Amazon region toward the southern part of South America, and moisture carried out from the Amazon basin, often condenses and precipitates in the region of the SALLJ convergence, producing explosive mesoscale convective complexes downstream of the low-level jet core, with a maximum of

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Edson E. Sano, Laerte G. Ferreira, and Alfredo R. Huete

-use mapping and monitoring is the relatively strong soil roughness and soil moisture effects on the backscattered energy from leaves, stalks, and trunks. Moran et al. ( Moran et al. 2002 ) also pointed out the unavailability of commercial, inexpensive ground- or aircraft-based SAR systems to understand the relations between radar images and biophysical properties of land surface. Such systems would be very important to understand the actual effects of roughness and moisture in decreasing the SAR

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Michael Keller, Ruth Varner, Jadson D. Dias, Hudson Silva, Patrick Crill, Raimundo Cosme de Oliveira Jr., and Gregory P. Asner

) practice. Soil–atmosphere exchange of carbon dioxide (CO 2 ), nitric oxide (NO), nitrous oxide (N 2 O), and methane (CH 4 ) is controlled by complex biogeochemical processes ( Conrad 1996 ). Tropical forests have high rates of biological productivity and rapid decomposition rates of organic matter because of abundant solar radiation, high temperature, and heavy precipitation. High nitrogen availability coupled with high moisture content makes tropical forest soils especially likely to emit N 2 O and NO

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Ted R. Feldpausch, Susan J. Riha, Erick C. M. Fernandes, and Elisa V. Wandelli

impoverishment in the pasture soils affects species composition of the regenerating secondary forest (SF); ( Vieira et al. 1994 ), and seedling establishment can be impeded because of herbivory and soil moisture stress ( Nepstad et al. 1996 ). The development of roots suckers and sprouts from stumps may be an important source of stem development in young fallows ( Kammesheidt 1998 ). The effect of land use on regrowth remains controversial. Some intensively used pastures develop biomass more slowly compared

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Lydia P. Olander, Mercedes M. Bustamante, Gregory P. Asner, Everaldo Telles, Zayra Prado, and Plínio B. Camargo

, such as roads and logging decks, and can persist for over a decade ( Congdon and Herbohn 1993 ; McNabb et al. 1997 ). These disturbed areas often have higher soil moisture, increased available nitrogen (N) and cations, but declines in total soil C, N, and P ( Congdon and Herbohn 1993 ; Ivo et al. 1996 ; McNabb et al. 1997 ). McNabb et al. (McNabb et al. 1997 ) found that changes in soil bulk density and soil nutrients were still detectable 16 yr after selective logging. They suggested that

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Cuizhen Wang, Jiaguo Qi, and Mark Cochrane

intensive computation. It is thus very time consuming to apply the model with multiple Landsat images to assess the forest degradation in large areas in the Amazon region. Another drawback of using linear mixture model in spectral domain is the internal and external effects to the reflectance. Although surface reflectance is primarily a function of the dominance of green vegetation, it also varies with moisture conditions and structures of both vegetation and soil. The influence of some external factors

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Andrew J. Elmore, Gregory P. Asner, and R. Flint Hughes

using linear regression. Precipitation plays an important role in determining the productivity of grasslands through inputs to soil moisture and through the release of nutrients ( Burke et al. 1998 ). To investigate the influence of precipitation timing on PV, NPV, and substrate cover in the MODIS time series, we acquired and processed monthly precipitation data from the National Oceanic Atmospheric Administration for 23 sites across the dry side of Hawaii. Land-cover values (PV, NPV, and substrate

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Wilfrid Schroeder, Jeffrey T. Morisette, Ivan Csiszar, Louis Giglio, Douglas Morton, and Christopher O. Justice

the time of day when most information loss occurs over a certain region. Consequently, biases from this effect vary over space and time and among sensors. Varying fuel loads encountered over different biomes also impact fire characteristics and, thereby, influence detection probability. Fire intensity and duration will depend on the type of biomass (plant physiology, community structure, moisture content) that is found to prevail over a biome class. As a result, woody vegetation structures may

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Gregory P. Asner, David E. Knapp, Amanda N. Cooper, Mercedes M. C. Bustamante, and Lydia P. Olander

materials found throughout Brazilian cerrado and Amazon ecosystems, with statistical variability well defined and deemed viable for end-member bundling ( Asner et al. 2004a ). The bare substrate spectra have been collected across a diverse range of soil types, surface organic matter levels, and moisture conditions. Spectral collections for NPV have included surface litter, senescent grasslands, deforestation residues (slash), and other dry-carbon constituents from a wide range of species and

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