Biotic and abiotic determinants modulate interactions between standing vegetation and soil seed bank across fine spatial scales

Abstract

Abstract Background and Aims Standing vegetation and soil seed banks are tightly related compartments in annual plant communities. However, little is known about how this relationship changes spatially and temporally and their dependence on abiotic and biotic factors. We investigated the similarity between both compartments under contrasting water availability conditions, perennials and biocrusts. Methods We established a field experiment in a Mediterranean annual plant community growing on gypsum soils. We evaluated the relationships between aboveground vegetation and soil seed bankover three years and along three spatial scales and tested the effects of water availability (irrigation), perennial vegetation and biocrust on both compartments. Results The soil seed bank was more similar to the standing vegetation closer to the third year, when seed bank was collected. The similarity between both compartments was higher at the large spatial scale (20 ´ 20 cm) but the modulatory effects of irrigation, perennial tussocks and biocrust were more evident at medium (10 ´ 10 cm) and fine scale (5 ´ 5 cm). The similarity increased with irrigation and was higher under perennial vegetation. The biocrust acted mainly as a barrier to the incorporation of seeds into the permanent seed bank. Conclusion Our findings suggest that abiotic and biotic factors had hierarchical effects on the similarity between the standing vegetation and soil seed bank compartments. Interannual shifts such as rainfall amount and frequency, were the main determinants but tussocks, biocrust, and irrigation modulated similarity, thereby showing that annual plant communities are driven by complex processes.