Micro-environmental conditions affect grass and shrub seedlingemergence in denuded areas of the arid Patagonian Monte, Argentina

Abstract

Harsh micro-environments in bare soil patches generated by disturbance may affect the emergence ofplant species in desert ecosystems. We evaluated the effects of litter addition on the emergence of peren-nial grass and evergreen shrub species under different conditions of UV radiation and soil water contentin disturbed patches of bare soil. We sowed seeds of perennial grasses (Nassella tenuis and Poa ligularis),and shrubs (Atriplex lampa, Larrea divaricata and Schinus johnstonii) in microcosms containing blocks ofupper soil (28 cm depth) subjected to different levels of three factors: litter (bare soil without litter cover,high quality litter cover from undisturbed plant patches, and low quality litter cover from disturbed plantpatches), UV radiation (near ambient and attenuated UV radiation), and soil water (5?15% and 15?25% ofvolumetric soil water content). The patterns of seedling emergence in relation to litter, UV radiation, andsoil water content varied among species independently of life form. Seedling emergence of all speciesincreased under exposure to UV radiation at all combinations of litter and soil water factors. High soilwater content had an important positive effect on the emergence of N. tenuis and L. divaricata in combi-nation with UV radiation and litter. In contrast, soil water content did not affect or affected negativelythe emergence P. ligularis and A. lampa in combination with litter and UV radiation. The emergence of S.johnstonii occurred only under exposure to UV radiation mostly at high soil water content, independentlyof litter levels. These results highlight the importance of the combined effects of the presence and typeof litter, soil water content, and UV radiation on seedling emergence of perennial grass and shrub speciesand consequently on the vegetation reestablishment processes at disturbed areas.