Abstract Land use has changed the original composition of the natural grasslands in the dry pampas of central Argentina, to the detriment of palatable perennial grasses (PPG). Long-term elimination of anthropogenic disturbances has not been enough to effectively recover the PPG, which suggests that availability of seeds and/or habitats may be limiting their recruitment. Therefore, our objectives in a degraded grassland site were to assess: (1) the germinable soil seed bank and (2) changes in botanical composition after addition of PPG seed following canopy disturbance. In autumn 2015, we randomly selected 10-paired plots, measured the aboveground biomass and took soil samples to assess the germinable soil seed bank. Afterwards, we disturbed the resident vegetation in each paired plot and either added PPG seeds or left the plot without any seed addition as a control. We quantified the seedling density of seeded and spontaneous species in the spring of 2015 and 2016, and the aboveground biomass at the end of 2017. Annual grasses and forbs (AGFS) dominated the soil seed bank, while PPG and unpalatable perennial grasses (UPG) occurred at low seed density and richness. Addition of PPG seeds resulted in the successful establishment of one key seeded PPG (Poa ligularis). In the spring 2017, the aerial biomass of PPG was highest in the seeded plots, where P. ligularis accounted for 94%. Our results showed that PPG were poorly represented in the soil seed bank of the degraded grassland and that disturbance of the resident vegetation combined with PPG seed addition enabled successful recruitment of a key PPG. So, enhancement of the pastoral value of degraded dry pampas grasslands would be possible through disturbance of the resident vegetation and addition of PPG seed.

中文翻译：

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在阿根廷中部干旱的潘帕斯草原退化的原生草原中通过干扰和种子添加来增强可口的多年生草

摘要 土地利用改变了阿根廷中部干燥潘帕斯草原天然草原的原始组成，损害了可口的多年生草类 (PPG)。长期消除人为干扰并不足以有效恢复 PPG，这表明种子和/或栖息地的可用性可能会限制它们的补充。因此，我们在退化草地场地的目标是评估：（1）可发芽的土壤种子库和（2）在冠层干扰后添加 PPG 种子后植物成分的变化。2015 年秋季，我们随机选择了 10 对地块，测量了地上生物量并采集了土壤样品以评估可发芽土壤种子库。然后，我们扰乱了每个配对地块中的常驻植被，要么添加 PPG 种子，要么在不添加任何种子的情况下离开地块作为对照。我们量化了 2015 年和 2016 年春季种子和自发物种的幼苗密度，以及 2017 年底的地上生物量。一年生禾本科植物 (AGFS) 在土壤种子库中占主导地位，而 PPG 和难食多年生禾本科植物 (UPG)发生在低种子密度和丰富度。添加 PPG 种子导致成功建立一种关键种子 PPG（Poa ligularis）。2017年春季，种地中PPG的地上生物量最高，其中P. ligularis占94%。我们的结果表明，PPG 在退化草地的土壤种子库中的代表性很差，并且居民植被的干扰与 PPG 种子添加相结合，能够成功招募关键 PPG。因此，通过干扰常驻植被和添加 PPG 种子，可以提高退化的旱潘帕斯草原的牧区价值。