Space variability of the seed bank in area of Caatinga in the Northeastern region of Brazil

Abstract

The seed bank in soil is one of the main long-term survival strategies of plant communities in the view of seasonality and irregularity of rainfall in arid and semiarid areas. Considering strong variation in seed bank richness and density in these environments, this study aims to evaluate the spatial variation of seed bank in an area of Caatinga, in northeastern Brazil, determining its floristic composition and germination density. The selected area was a temporary lagoon in the Cariri region of Paraíba state, with highly anthropized vegetation, due to various uses over time. At each cardinal point, taking the center of the lagoon as a reference, soil samples were taken from the seed bank. All material collected was distributed in plastic trays and irrigated daily. The determination of seed density in the soil bank was performed by the seedling emergence method and expressed in seeds m^-2. The flora of the Caatinga soil seed bank was represented in this study by 26 species and three morphospecies, distributed in 11 families and 26 genera, among them the Poaceae and Asteraceae families with the largest number of species. The main life form of the seed bank was herbaceous and the average density of the study area was 2,942 seeds.m^-2 (lagoon) and 3,826 seeds.m^-2 (in the surroundings) and after water stress was 732 seeds.m^-2 and 1,208 seeds.m^-2, in and around the lagoon areas, respectively. The area surrounding the lagoon has the highest plant density per m² and the highest diversity of species. In addition, the northern direction in both areas presented lower seed density.

Keywords:
Caatinga; Herbaceous stratum; Temporary lagoon; Species richness; Semiarid