Resumo

PEREZ GARCIA, Carlos Alejandro; LOPEZ BLANCO, Jorge  e  VELA CORREA, Gilberto. Relief influence on properties of a soil disturbed by a wildfire in El Pelado volcano, Central Mexico. Invest. Geog [online]. 2009, n.69, pp.7-20. ISSN 2448-7279.

The alteration of the physical and chemical soil-properties in non-burnt areas (NBA) and burnt-areas (BA) are two important characteristics for the development of soil and vegetation regarding to the three contrasting slope portions. A soil-sampling with a directed-strategy of burnt and not burned areas in a micro catchment was carried out considering three slope positions in the relief: a) Channel stream, b) Backslope, and c) Summit. The soils from the non-burnt areas were taken starting from a reference point under the same relief conditions, for what the soil samples from non-burnt areas came from a transect with six sampling-sites, while the burnt-soils had three transects with fifteen sampling-sites. The results obtained show that the bulk density increased on the summit and the channel-stream as a combustion product of the organic matter (OM) in the BA soils in comparison with the NBA soils, affecting soil structure and diminishing the total soil porosity. The biggest amount of soil aggregates was in the channel stream, prevailing the microaggregates and mesoaggregates. The soils have shown a slight decreasing in the pH in the channel stream and summit areas. There was an increment of Ca²⁺, Mg²⁺ y K⁺, which indicates that one of the immediate wildfire effect was to liberate the mineral elements that become more abundant and they stimulate the plant-growing. The CIC diminished on the summit but it increased lightly in the backslope and the channel, which it is attributable to the impact of the OM combustion that accelerated the mineralization process and it favored the transfer and deposit of clays and humic complexes in the backslope and channel. The phosphorus presented a slight decreasing regarding to the NBA soils, being located the biggest quantity of this nutriment in the backslope and channel portions. The channel and the backslope were the slope portions that presented bigger differences attributable to that the wildfire has a bigger intensity and duration, causing larger alterations in the physical and chemical soil properties, while in the summit area the differences were smaller, because they are considered more stable places.

Palavras-chave : Wildfire; soil; slope portions; physical and chemical soil-properties; El Pelado; Central Mexico.

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