Seed rain in and between vegetation patches in arid Patagonia, Argentina

Abstract

Seed rain has ecological consequences on plant community structure. This study was conducted in the Monte Austral Neuquino nearby the town of Picún Leufú, Province of Neuquén, Argentina, within an area of 15 km x 15 km (39º 20 32' S; 69º19 30' W). Studies were conducted at two sites, distant 1.5 km from one another. Vegetation is distributed on the soil surface as vegetation patches. Four superficial locations may be found in the soil of these patches: location 1, small dune accumulated under the lee; location 2, found at the edge of the small dune, and below the major grass canopies and tallest shrubs; location 3, located at the edge of the vegetation patch, and location 4 which includes the uncovered corridors among vegetation patches. Seed rain was measured by collecting seeds from traps located in the four study locations. Our working hypotheses were that (1) seeds of the study species arrive to all locations of the vegetation patches and the nude corridors among patches, and (2) the magnitude of the seed rain depends on time of the year. Larrea divaricata showed the greatest values in the corridors among vegetation patches and in the periphery of such patches. A similar pattern was found for S. neaei although this species dispersed seeds further from the mother plant. Atriplex lampa distributed seeds homogeneously in all four locations. Elymus erianthus only contributed 1 seed to the seed rain. Larrea divaricata showed a greater proportion of its total seed rain between December and March in all locations. Seed rain in A. lampa was almost permanent throughout the year while in S. neaei was concentrated in December and January, although it showed some seed rain until April.