Analizando mosaicos de bosques y pastizales: tres casos de estudio en el subtropico húmedo de Brasil
2009
Landscapes exhibiting complex mosaics of contrasting natural ecosystems, like forests and
grasslands, continue to evade a straightforward interpretation concerning the key drivers behind
the landscape mosaic. Our research shows that the high-level drivers of the land cover - land use
mosaics, characteristic of the basaltic tablelands of northern Rio Grande do Sul, Brazil, can be
identified based on analysis of the vegetation pattern in relation to geomorphic and pedogenetic
phenomena controlling water and nutrient supply, together with human action. The analysis is
implemented on two spatial scales: one regional, embracing a large portion of tablelands, and the
other at the landscape scale by selecting three contrasting sites. Natural grasslands (campos)
still extend over much of the highest plateaus, on young but nutrient-depleted inceptisols. While
on the lower altitudes campos over deep oxisols have been extensively replaced by cash crops. The
Araucaria angustifolia montane forest characterizes the higher tablelands, where it occurs in
habitats with a permanent water supply and out of the reach of the frequent grasslands fires.
Semideciduous forests occur on the lower plateaus, restricted to the wet conditions of the
bottomlands. In any case, the increasingly widespread human disturbance renders the natural pattern
fuzzy, but the close correspondence between more fertile habitats and forest occurrence suggests
that nutrient availability plays a key role. Nutrient availability, in turn, results from enhanced
rates of erosion wearing out the ancient peniplain and further developing the drainage system. A
conceptual model relating geomorphic, pedogenetic and human factors is proposed to explain the
original and actual vegetation mosaics.
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