Key sites for seedling emergence in degraded areas of the monte ecoregion of the Rio Negro Province, Argentina

Abstract

In disturbed shrublands of the Monte ecoregion in the Rio Negro province, herbaceous vegetation occurs in patches of high plant cover beneath shrubs, interspersed with patches of low cover between them, which leads to the existence of differential microsites in the environment. The protected understory in the shrub patches is occupied by other functional groups that conform this system: perennial grasses, annuals and biological crusts. The areas between the shrubs may be more or less degraded by grazing, and may exhibit physical impediments to the germination and establishment of seeds and to seedling emergence and survival, in the form of vesicular crusts that develop on the soil surface and contribute to desertification in those systems where they appear. The objective of our study was to relate the presence of seedlings in three microsites of the environment: a) beneath shrubs, and in the open spaces between them discriminated into b) flat and c) rough places, with different covers of the soil surface (biological crust, litter, perennial grasses and gravel), and with the presence and thickness of vesicular crusts, in a semi-arid shrubland of the south-eastern Monte ecoregion. We found that the presence of seedlings differed between the microsites and was related to the different soil cover in each microsite. In flat microsites, that presence was positively related with litter and biological crust covers and negatively related to vesicular crust thickness and gravel cover; in rough places we only found a positive influence of litter, and beneath shrubs, there were beneficial effects due to perennial grass cover and scarce negative effects due to vesicular crusts.