Seed rain is critical for forest recovery, especially in abandoned lands that have been converted to agriculture. However, such a critical role depends on seed viability, which has been largely overlooked in most seed rain studies. We assessed the viability of seeds in the seed rain falling into 12 plots from a Brazilian tropical dry forest: six plots exposed to slash-and-burn agriculture (‘burned plots’ = 111 seeds from 10 species) and six located in forest stands (‘control plots’ = 5267 seeds from 23 species). Using the tetrazolium test, we found that only 767 of 5378 seeds (14%) from 16 species were viable, but surprisingly, seed viability was 2.2 times higher in burned plots than in control ones. This does not imply that forest regeneration through seed rain is more effective in burned plots, as very few seeds arrived at these plots. A functional analysis revealed that the higher seed viability in burned plots may be explained by the fact that these plots were dominated by relatively large, hard-coated (orthodox), and abiotically dispersed seeds, with some type of dormancy, as seeds with these functional trait attributes showed the highest viability. To accurately assess the importance of seed rain for forest regeneration we must consider seed viability, as it can be very low in some places, especially if dominated by species with relatively small, animal-dispersed and recalcitrant seeds lacking dormancy.

种子雨对于森林恢复至关重要，特别是在已转变为农业的废弃土地上。然而，这种关键作用取决于种子的活力，而这在大多数种子雨研究中很大程度上被忽视了。我们评估了落入巴西热带干燥森林 12 个地块的种子雨中种子的生存能力：其中 6 个地块采用刀耕火种农业（“烧毁地块”= 10 个物种的 111 颗种子），另外 6 个地块位于林分中（ “对照地块”= 23 个物种的 5267 颗种子）。使用四唑测试，我们发现来自 16 个物种的 5378 颗种子中只有 767 颗 (14%) 是有活力的，但令人惊讶的是，烧毁地块中的种子活力比对照地块高 2.2 倍。这并不意味着通过种子雨进行的森林再生在烧毁的土地上更有效，因为到达这些土地的种子很少。功能分析表明，烧毁地块中种子活力较高的原因可能是，这些地块以相对较大、硬质包衣（正统）和非生物分散的种子为主，具有某种类型的休眠状态，因为具有这些功能的种子特质属性显示出最高的生存能力。为了准确评估种子雨对森林再生的重要性，我们必须考虑种子的活力，因为在某些地方，种子的活力可能非常低，特别是当种子以相对较小、动物分散且缺乏休眠的顽抗种子的物种为主时。