A B S T R A C TIn semi-arid environments, the distribution of rainfall over time is decisive in emergence in a soil seed bank. The objective of this study was to evaluate the effect of rainfall events on the soil seed bank emergence of Caatinga species under high CO2 concentration. The experiment was carried out in an experimental area of Embrapa Semi-arid in a randomized complete block design, with subdivided plots. o C, at depths of 0.02 and 0.06 m, respectively. Seedling emergence started 56 days after sowing and four days after the first rains. After 154 days of the onset of the experiment, drip irrigation was performed. The greenhouse environment, regardless of the addition of CO2 or not, allowed higher emergence percentage of P. pyramidalis. The seeds of this species sowed on the soil surface only emerged when irrigation started. M. urundeuva seeds showed low germination even after irrigation.

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