Unleached Prosopis litter inhibits germination but leached stimulates seedling growth of dry woodland species

Prosopis chilensis-Prosopis juliflora hybrid (hereinafter referred to as Prosopis species) invade riverine Acacia woodlands and replace indigenous Acacia tortilis through mechanism that are not yet well understood. Therefore, we tested the hypothesis that dense shade and allelopathic effects of Prosopis species may reduce the germination and growth of A. tortilis more strongly than that of Prosopis species through greenhouse studies. We first evaluated the germination of A.tortilis and Prosopis species seeds with increasing concentration of unleached and leached Acacia or Prosopis litter in soil. Subsequently, we evaluated the growth of A. tortilis and Prosopis species seedling in response to concentration of Acacia or Prosopis litter at different light intensity regimes. Unleached Prosopis litter inhibited germination of A. tortilis and Prosopis species seeds with increase in litter concentration in the soil. Leached Acacia or Prosopis litter had no effect on seed germination but enhanced growth and shoot nutrient concentrations of A. tortilis and Prosopis species seedlings. Growth response to light intensity treatments was similar in both A. tortilis and Prosopis species seedling. The findings suggest that the lack of A. tortilis seedlings under Prosopis canopies in nature may be partially explained by Prosopis litter allelopathy on A. tortilis seed germination.