Permanent grassland soils can act as a sink for carbon and may therefore positively contribute to climate change mitigation and adaptation. We compared young (5–15 years since latest grassland renewal) with old (>20 years since latest grassland renewal) permanent grassland soils in terms of carbon stock, carbon sequestration, drought tolerance and flood resistance. The research was carried out on marine clay soil at 10 dairy farms with young and old permanent grassland. As hypothesized, the carbon stock was larger in old grassland (62 Mg C ha⁻¹) topsoil (0–10 cm) than in young grassland topsoil (51 Mg C ha⁻¹). The carbon sequestration rate was greater in young (on average 3.0 Mg C ha⁻¹ year⁻¹) compared with old grassland (1.6 Mg C ha⁻¹ year⁻¹) and determined by initial carbon stock. Regarding potential drought tolerance, we found larger soil moisture and soil organic matter (SOM) contents in old compared with young grassland topsoils. As hypothesized, the old grassland soils were more resistant to heavy rainfall as measured by water infiltration rate and macroporosity (at 20 cm depth) in comparison with the young grassland soils. In contrast to our hypothesis we did not find a difference in rooting between young and old permanent grassland, probably due to large variability in root biomass and root tip density. We conclude that old grasslands at dairy farms on clay soil can contribute more to the ecosystem services climate change mitigation and climate change adaptation than young grasslands. This study shows that under real farm conditions on a clay topsoil, carbon stock increases with grassland age and even after 30 years carbon saturation has not been reached. Further study is warranted to determine by how much extending grassland age can contribute to climate change mitigation and adaptation.

中文翻译：

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延长草地年龄以减缓和适应粘土的气候变化

永久性草原土壤可以作为碳汇，因此可能对减缓和适应气候变化做出积极贡献。我们在碳储量、碳固存、耐旱性和抗洪性方面比较了年轻（最近一次草地更新后 5-15 年）和老（最近一次草地更新后 > 20 年）永久性草地土壤。该研究是在 10 个奶牛场的海洋粘土土壤上进行的，这些奶牛场拥有年轻和古老的永久性草地。正如假设的那样，老草地（62 Mg C ha ^-1）表层土壤（0-10 cm）的碳储量大于年轻草地表层土壤（51 Mg C ha ^-1）。与老草地（^{1.6 Mg}  C ha^-1 年^-1) 并由初始碳储量确定。关于潜在的耐旱性，我们发现与年轻的草地表土相比，旧的土壤水分和土壤有机质（SOM）含量更高。正如假设的那样，与年轻的草地土壤相比，通过水入渗率和大孔隙率（20 cm 深度）测量，老草地土壤更能抵抗暴雨。与我们的假设相反，我们没有发现年轻和古老的永久性草地之间的生根差异，这可能是由于根生物量和根尖密度的巨大差异。我们得出结论，奶牛场在粘土上的老草地比年轻草地对生态系统服务气候变化缓解和气候变化适应的贡献更大。这项研究表明，在粘土表土上的真实农场条件下，碳储量随着草地年龄的增加而增加，甚至在 30 年后还没有达到碳饱和。有必要进一步研究以确定延长草原年龄在多大程度上有助于减缓和适应气候变化。