Search Results

You are looking at 1 - 9 of 9 items for :

  • Seasonal effects x
  • Large-Scale Biosphere-Atmosphere (LBA) Experiment x
  • All content x
Clear All
Edson E. Sano, Laerte G. Ferreira, and Alfredo R. Huete

soybean and corn). Nowadays, cerrado is the main agricultural province in Brazil and is the country’s most severely threatened biome, requiring a prompt, continuous, and precise mapping and monitoring. To date, the majority of the studies related to the cerrado’s seasonal and land-cover monitoring have been based on optical remote sensing technology. França and Setzer ( França and Setzer 1998 ) as well as Mantovani and Pereira ( Mantovani and Pereira 1998 ) focused on the use of Advanced Very High

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

the wet and dry seasons regardless of soil type. There was a trend of decreasing CH 4 fluxes with decreasing WFPS, but the correlation was weak and insignificant ( Figure 3b ) regardless of soil type. Both seasonal and soil effects were significant in the analysis of variance ( p < 0.05) and there was no significant interaction. On the clay Oxisol, in the wet season methane production dominated consumption, and the average CH 4 flux combining 2000 and 2001 was 0.5 mg CH 4 m −2 day −1 ( Table

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

typically lasting into the spring of the following year. The relationship between these PV “peaks” and the NPV and substrate time series is shown in Figure 7 , but also in a calculation of the seasonal cycle (averaged for 2000–04) ( Figure 8 ). Seasonal increases in PV fraction were associated with a decrease in NPV and substrate fraction as the new growth covered dead plant litter from the previous year and covered exposed substrate. Coincident with the annual PV peak, NPV began to increase and

Full access
Tomas F. Domingues, Joseph A. Berry, Luiz A. Martinelli, Jean P. H. B. Ometto, and James R. Ehleringer

change among ecosystems, the understanding of such changes is of fundamental importance for the correct parameterization of a process-based model. The lack of effects of season observed for the relationships presented in this work indicates little or no acclimation of gas exchange plant physiological parameters occurs over the dry (or wet) season. Therefore, observed seasonal variations in NEE may be better explained by variations in climatic conditions or ecosystem-level respiration, rather than

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

Atmospheric Correction Now (ACORN) algorithm for hyperspectral data (ImSpec, Inc., Pasadena, California), and convolved to six Landsat ETM+ optical channels. These green vegetation spectra thus inherently included the variable effects of intra- and intercrown shadowing, which are prevalent in tropical forests ( Gastellu-Etchegorry et al. 1999 ). In Amazonia, shade fractions average 25% cover in humid tropical forests, but the variance is high with standard deviations of 12% or more ( Asner and Warner 2003

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

basal area by diameter classes and growth form for 10 forests regenerating from abandoned pastures on oxisols in an udic soil moisture regime to complement published studies on oxisols and ultisols in the seasonally drier ustic soil moisture regime in eastern Amazônia. 2. Methods 2.1. Study areas The study was conducted at three fazendas (cattle ranches) spanning approximately 26 km along the federal road BR-174 from Manaus to Boa Vista: Fazenda Rodão (km 46), the Brazilian Agricultural Research

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

1. Introduction Biomass burning plays an important role in various aspects of the global climate system, largely because of the effects of trace gas emissions from biomass combustion and the resulting changes to the radiation and energy budget ( Crutzen and Andreae 1990 ; Lenoble 1991 ; Artaxo et al. 1998 ; Eck et al. 1998 ; Ross and Hobbs 1998 ). Of the total number of fire events observed every year, most occur in the Tropics ( Hao and Liu 1994 ; Dwyer et al. 2000 ), due to the

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

. Nutrients in the bole wood of the mature harvest trees vary across the Amazon, nutrients in rainfall may also be affected by large-scale regional forcings, but more localized and seasonal burning may have a large effect. This variability in inputs and outputs makes generalization of sustainable harvest intensity difficult. Logging is likely to cause subtle changes in soil structure and nutrient dynamics that are detectable both immediately after logging and for years to come. However, these changes do

Full access
Douglas C. Morton, Ruth S. DeFries, Yosio E. Shimabukuro, Liana O. Anderson, Fernando Del Bon Espírito-Santo, Matthew Hansen, and Mark Carroll

-date image differencing method, but the NDVI difference was only calculated for areas where the 2002 NDVI < 0.8 to reduce the analysis area and minimize false detections that are a result of seasonal variations in forest phenology. The 2002 NDVI threshold acts as a second forest mask in this method. Values that exceeded the mean difference plus 0.5, 1, or 2 standard deviations of the mean difference were classified as deforestation. Image differences and single 2002 image thresholds were run separately

Full access