Skip to main content. Log In Sign Up. Ecosistemas de la cuenca del Orinoco colombiano. Global Change Biology 16, —, doi: Savannas, which cover approximately million ha in South America, play a major role in the global carbon cycle. They are affected by human pressures and global climate change.
Using satellite data, this study quantifies vegetation burning in the Colombian Llanos savannas for the period —, and analyzes how fire spatial pattern, frequency and extent vary with ecosystem type, land tenure and rainfall. Burned area is highly variable, with 3. However, during the — period near of 3. Compared with the average 8—10 years of fire return time for the tropics and subtropics, these savannas burn twice as often.
Fires predominate in the well-drained high plain savannas, lowest figures occurring along the Andean foothills, in forested areas and in pasture and croplands. Annual proportion burned varies with land tenure, being highest in National Parks.
This study Cuenca del orinoco yahoo dating the first complete regional map of fire disturbance in a South American savanna. This detailed regional data provides a unique opportunity for increasing the accuracy of global carbon emission calculations. Savanna fires are a contributing to global ecological change Foley et al.
Factors driving land cover dynamics such as fire et al. With global ; Grace et al. Humans have used fire to warming some of these factors will change due to the develop roads, establish crop areas, eliminate grass expected temperature increases and longer droughts in and other types of nondesirable vegetation, eliminate this biome.
A funda- playing in the world food supply Brannstrom et al. In the Brazilian savannas burning frequency sions is the lack of spatially explicit regional analyses increased due to more intensive management of the that can be included in calculations, under the wide native grasslands for cattle grazing Coutinho,range of biophysical and management conditions in while in areas of intensive agriculture and improved savannas.
In Colombia there has been an increasing grate GIS databases that can capture the heterogeneity expansion of the agricultural front into the savannas of of natural factors and management, rather than look to the Llanos during the last 30 years.
Such human pres- providing more detailed field data. In their study of the sures are driving big changes in the ecological processes global characterization of fire regimes Chuvieco et al.
The cially in mesic savannas with mean annual rainfall Llanos of Colombia and Venezuela is an important mm Sankaran et al. The Llanos exhibit high fire frequencies Tansey change savannas could potentially help with carbon et al. This controlled by management options. We address the variability of the burning However, carbon accounting still relies too much on patterns using the best available satellite data for the global average figures with few regional studies.
Emis- period of — A specific aim was to establish the sions from fires can vary significantly due to local and extent, recurrence and area patterns in relation to bio- regional differences in ecosystem type, biomass and physical and management factors, such as rainfall, combustion efficiencies Van Der Werf et al. The Cuenca del orinoco yahoo dating landscapes are composed of flat to rolling plains and comprise three major geomorpholo- gic units: Annual rainfall varies between and ally flooded savannas in the lower parts close to the River mm in an east—west gradient.
The dry season runs Meta, which run northeast into Venezuelan Apure region.