Edaphic and climatic control of macaúba palm seed bank dynamics

Abstract

The control of soil seed bank (SSB) dynamics is crucial to the ecologies of plant populations of many species, but has been little studied in tropical environments. The objectives of this work were to characterize the SSB of Acrocomia aculeata, an important neotropical oleaginous palm, and to define the influence of edaphic and climatic factors on its dynamics. Exposed and buried diaspores were collected in five areas of the Cerrado biome in central Brazil. Evaluations of the diaspores, young plants, and in vitro embryo cultures defined 26 indicators of SSB dynamics that were correlated with 19 physical-chemical attributes of the soil. Seedlings emergence was studied under greenhouse conditions during five years and the thermal control of germination was evaluated experimentally. A. aculeata forms persistent SSBs, with P being the main edaphic factor associated with seed input. High levels of Al and clay (associated with insect predation), organic matter (fungal contamination), and sand (bacterial contamination) contributed to negative outputs (embryo death). The maintenance of intact SSB embryos, however, is independent of edaphic factors. Wide thermal amplitudes in the winter associated with high temperatures in the spring promote overcoming dormancy and favor positive SSB outputs as well as the synchronization of seedling emergence at the beginning of rainy season. The high productivity of A. aculeata and its ability to maintain viable but dormant embryos in the soil contribute to controlling SSB dynamics, reproductive success, and its wide distribution.