Effects of vegetation management on plant diversity in traditional irrigation systems

Acequias are historical community-operated water channels used for irrigating of traditional farming areas (vegas). They have been traditionally managed by local inhabitants, either by clearing weeds or by burning them in winter, in order to keep the channels clean of vegetation, thus avoiding their clogging. The impact of these cultural practices on vegetation has not still been studied. The aim of this paper is to show how traditional management influences floristic biodiversity in a traditional acequia in the vega of Granada (SE Spain). The acequia was treated following the traditional methodology used by farmers, being divided into areas that were burned, cleared, or left unchanged as control (January 2016). Afterwards, we collected soil samples and analyzed them in the lab to determine the treatment effects on soil properties. Vegetation was monitored in late spring 2016 in order to detect differences between treatments. Traditional management increased plant diversity, this effect being much more patent for the burning than for clearing treatment. Soil analyses revealed only slight differences in pH and CaCO₃ content, higher for the burning treatment. The increase in plant diversity found in areas treated by traditional management was due mainly to the reduction of competition, which promoted the emergence or increase of populations of non-dominant species. The results indicated that traditional management not only offers advantages to the farmers but also promotes plant diversity and ecosystem services.