Abstract

ORTUNO, Teresa; BECK, Stephan  and  SARMIENTO, Lina. Plant succesional dynamics of long term fallow in the central Altiplano of Bolivia. Ecología en Bolivia [online]. 2006, vol.41, n.3, pp.40-70. ISSN 1605-2528.

Plant succesional dynamics in fallow plots in the Bolivian Altiplano has been studied, where peasants practice a long, sectorial fallow. The objective was to analyse the successional changes in species diversity, vertical structure of vegetation, abundance of different life forms. The results indicate that there have been little changes in richness and diversity, contrary to what has been reported for secondary successions, possibly due to the adaptation of selected species to the harsh conditions of climate, restricted soil conditions and the anthropogenic influence. This trend can also be related to the great abundance of annual plants, which have the capacity of colonizing rapidly the fallow plots, enabling the existence of a high number of species from the start of succession; these annuals occasionally and opportunistically also settle the older plots. Furthermore, many of the species present a very broad tolerance range, which indicates that after they have colonised a plot, they can stay there for a long time. The vertical structure of vegetation showed a dominance of a herbal layer of 0-5 cm in all plots. It was possible to identify serial trends with annuals like Erodium cicutarium, Tagetes multiflora, Tarasa tenella and Bromus catharticus in the first years of fallow. Till 6 years of fallow we recorded a constant increase of perennial grasses like Stipa ichu and Nassella spp. and some evergreen resinous shrubs; later on we noticed a non lineal increase till 10 to 20 years, depending on soil conditions, humidity, location and history of the plots. With increasing years of fallow the soil fertility (C, N, K, Mg, and Ca) recovered as shown by an analysis multivariable of 9 to 22 year/old plots in comparison to young fallows.

Keywords : Altiplano; Fallow; Succession; Indicator plants.

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