Prosopis flexuosa effects on the spatial pattern of understory species and soil properties in the Monte desert (Argentina)

ROSSI, B.E.; VILLAGRA, P.E.

JOURNAL OF VEGETATION SCIENCE

Opulus Press

Año: 2003 vol. 14 p. 543 - 550

1100-9233

n arid zones dominant woody plants are capable ofcausing changes in microclimate and soil properties likely toaffect species composition, as well as the establishment andspatial distribution of plant species. In North American andEuropean deserts species richness appears to be higher underthe canopy of shrubs and trees, in contrast with Chilean desertswhere it seems to be lower. Since Prosopis flexuosa (Fabaceae,Mimosoideae) is the most conspicuous tree in the centralMonte desert, Argentina, we analysed the effect of this specieson the composition and abundance of the shrub and herba-ceous layers and on soil properties. We considered twomesohabitats: ‘under P. flexuosa canopy’ and ‘intercanopyareas’. In addition, we analysed the differences between twomicrohabitats under canopies: ‘northern part of the canopy’and ‘southern part of the canopy’. Results indicate that speciescomposition and soil properties are affected by bothmesohabitats and microhabitats. We found a higher number ofshrubs under canopies, whereas that of grasses and perennialforbs increased in intercanopy areas. Concentrations of or-ganic matter, nitrogen, potassium and phosphorus, factorslimiting biological productivity in Monte desert soils, weresignificantly higher under than outside P. flexuosa canopies.Electrical conductivity and concentrations of Na+, Ca++, Mg++were higher in the northern than in the southern microhabitats.No differences in species richness, evenness or diversity werefound between mesohabitats or between microhabitats. Weconclude that P. flexuosa modifies the spatial pattern of plantspecies in the shrub and herbaceous layers and the chemicalconditions of the soil, generating spatial heterogeneity ondifferent scales.