Geoecological drivers of cerrado heterogeneity and 13C natural abundance in oxisols after land-use change

Revista Brasileira de Ciência do Solo

Henry Neufeldt¹ 

[1] ,University of East Anglia Tyndall Institute for Climate Change Research Norwich,United Kingdom

关键词: Cerrado formations;    13C natural abundance;    waterlogging;    Oxisol;    soil fertility;    land-use change;    formações de cerrados;    abundância natural de 13C;    hidromorfia;    Latossólos;    fertilidade do solo;    manejo do solo;   

DOI  :  10.1590/S0100-06832006000500015

来源: SciELO

【 摘 要 】

The 13C natural abundance technique was applied to study C dynamics after land-use change from native savanna to Brachiaria, Pinus, and Eucalyptus in differently textured Cerrado Oxisols. But due to differences in the d13C signatures of subsoils under native savanna and under introduced species, C substitution could only be calculated based on results of cultivated soils nearby. It was estimated that after 20 years, Pinus C had replaced only 5 % of the native C in the 0-1.2 m layer, in which substitution was restricted to the top 0.4 m. Conversely, after 12 years, Brachiaria had replaced 21 % of Cerrado C to a depth of 1.2 m, where substitution decreased only slightly throughout the entire profile. The high d13C values in the subsoils of the cultivated sites led to the hypothesis that the natural vegetation there had been grassland rather than Cerrado sensu stricto, in spite of the comparable soil and site characteristics and the proximity of the studied sites. The hypothesis was tested using aerial photographs of 1964, which showed that the cultivated sites were located on a desiccated runoff head. The vegetation shift to a grass-dominated savanna formation might therefore have occurred in response to waterlogging and reduced soil aeration. A simple model was developed thereof, which ascribes the different Cerrado formations mainly to the plant-available water content and soil aeration. Soil fertility is considered of minor significance only, since at the studied native savanna sites tree density was independent of soil texture or nutrient status.

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