Although direct tree seeding may be a potentially useful restoration practice, many biotic and abiotic barriers prevent seedling emergence and early development, reducing its success and applicability. To overcome these barriers, we undertook a field experiment to test the effects of using green manure and hydrogel alone, or in combination, on seedling performances of 14 native tree species that were planted by direct seeding in a deforested tropical seasonal forest area in southern Brazil and to examine how green manure affected the initial weed coverage in the study plots. We evaluated competing vegetation coverage and tree seedling emergence and early development for 2 years after sowing. Weed infestation was significantly higher in the experimental plots with no green manure; however, neither green manure nor hydrogel improved tree seedling emergence and early development at any time of measurement. Our results suggest that the use of green manure and hydrogel alone, or in combination, were not effective in guaranteeing direct seeding success; however, green manure can be an effective method to reduce weed infestation. Direct seeding techniques for tree species still need to be improved in order to restore tropical seasonal forests on a larger scale.

中文翻译：

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直接播种以恢复热带季节性森林：绿肥和水凝胶改良剂对树木性能和杂草侵染的影响

尽管直接播种可能是潜在的有用恢复方法，但许多生物和非生物屏障阻碍了幼苗的出现和早期发育，从而降低了其成功率和适用性。为了克服这些障碍，我们进行了田间试验，以测试单独使用绿肥和水凝胶或结合使用绿肥对14种原生树种的幼苗性能的影响，这些树种是通过直接播种在巴西南部一片森林砍伐的热带季节性森林地区种植的并研究绿肥如何影响研究区的初始杂草覆盖率。我们评估了播种后2年的竞争性植被覆盖率，树木幼苗的出苗和早期发育。在没有绿肥的实验田中，杂草的侵害显着增加。然而，在任何时间测量，绿肥和水凝胶都无法改善树木的出苗和早期发育。我们的结果表明，单独使用绿肥和水凝胶或组合使用绿肥不能有效保证直接播种成功。但是，绿肥可以成为减少杂草侵扰的有效方法。为了更大规模地恢复热带季节性森林，仍然需要改进树木种的直接播种技术。