Abstract Woody species play a key role in Stipa tenacissima steppes, they affect ecosystem functioning, facilitate establishment of other plants and increase plant richness. Among the mechanisms involved in facilitation, effect of litter on seed germination and seedling establishment is largely underexplored. We studied the properties of the litter layer under five woody species common in Stipa tenacissima steppes, and assessed its effect on the germination of seeds of two key species with contrasting ecological strategy and seed morphology (the perennial grass Brachypodium retusum and the resprouting shrub Pistacia lentiscus). Litter accumulation was highest under Quercus coccifera and Pinus halepensis, and lowest under Rhamnus lycioides. Pistacia lentiscus and Rosmarinus officinalis showed intermediate levels. Litter accumulation hampered germination, particularly when seeds were sown over the litter. Litter of all species but Rhamnus lycioides reduced germination when seeds were under the litter. Litter extracts had no effect on germination. The effect of litter was largely independent of seed type. Our results show that litter has an overall negative effect acting as a physical barrier for. Litter may influence the balance between facilitation and interference. Its relation with species traits and its impact on habitat heterogeneity and community assemblage deserves further attention.

中文翻译：

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垫料作为半干旱针茅草原发芽的过滤器

摘要 木本物种在针茅草原中发挥着关键作用，它们影响生态系统功能，促进其他植物的建立并增加植物丰富度。在参与促进的机制中，凋落物对种子萌发和幼苗建立的影响在很大程度上未被探索。我们研究了针茅草原常见的五种木本物种下凋落物层的特性，并评估了其对生态策略和种子形态不同的两个关键物种（多年生草 Brachypodium retusum 和重芽灌木 Pistacia lentiscus ）。凋落物积累在 Quercus coccifera 和 Pinus halepensis 下最高，在 Rhamnus lycioides 下最低。Pistacia lentiscus 和 Rosmarinus officinalis 显示中等水平。垫料堆积阻碍了发芽，特别是当种子撒在垫料上时。当种子在垫料下时，除 Rhamnus lycioides 外，所有物种的垫料都会减少发芽。凋落物提取物对发芽没有影响。凋落物的影响在很大程度上与种子类型无关。我们的结果表明，垃圾具有作为物理障碍的整体负面影响。垃圾可能会影响促进和干扰之间的平衡。它与物种性状的关系及其对生境异质性和群落组合的影响值得进一步关注。我们的结果表明，垃圾具有作为物理障碍的整体负面影响。垃圾可能会影响促进和干扰之间的平衡。它与物种性状的关系及其对生境异质性和群落组合的影响值得进一步关注。我们的结果表明，垃圾具有作为物理障碍的整体负面影响。垃圾可能会影响促进和干扰之间的平衡。它与物种性状的关系及其对生境异质性和群落组合的影响值得进一步关注。