1. Land abandonment has been increasing in recent decades in Europe, usually accompanied by biodiversity decline. Whether livestock grazing and mowing can safeguard biodiversity across spatial scales in the long term is unclear.
2. Using a 48-year experiment in a salt marsh, we compared land abandonment (without grazing and mowing) and seven management regimes including cattle grazing, early season mowing, late season mowing, both early and late season mowing, and grazing plus each of the mowing regimes on plant diversity at the local and larger scales (i.e. aggregated local communities). Also, we compared their effects on community composition (both in identities and abundances) in time and space.
3. Under land abandonment, plant diversity declined in the local communities and this decline became more apparent at the larger scale, particularly for graminoids and halophytes. All management regimes, except for late season mowing, maintained plant diversity at these scales.
4. Local plant communities under all treatments underwent different successional trajectories, in the end, diverged from their initial state except for that under grazing (a cyclic succession). Year-to-year changes in local community composition remained at a similar level over time under land abandonment and grazing plus early season mowing while it changed under other treatments. Vegetation homogenized at the larger scale over time under land abandonment while vegetation remained heterogeneous under all management regimes.
5. Synthesis. Our experiment suggests that late season mowing may not be sustainable to conserve plant diversity in salt marshes. Other management regimes can maintain plant diversity across spatial scales and vegetation heterogeneity at the larger scale in the long term, but local community composition may change over time.

中文翻译：

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盐沼系统中放牧和割草对植物多样性和群落组成的长期跨尺度比较

1. 近几十年来，欧洲的土地遗弃一直在增加，通常伴随着生物多样性的下降。从长远来看，牲畜放牧和割草是否可以保护跨空间尺度的生物多样性尚不清楚。
2. 通过在盐沼中进行 48 年的试验，我们比较了土地废弃（不放牧和割草）和七种管理制度，包括放牧、早季割草、晚季割草、早晚割草以及放牧加每一种在当地和更大范围内（即聚集的当地社区）的植物多样性割草制度。此外，我们比较了它们在时间和空间上对社区组成（身份和丰度）的影响。
3. 在土地放弃下，当地社区的植物多样性下降，这种下降在更大范围内变得更加明显，特别是对于禾本科和盐生植物。除晚季割草外，所有管理制度都在这些规模上保持了植物多样性。
4. 所有处理下的当地植物群落经历了不同的演替轨迹，最终除了放牧（循环演替）外，都偏离了初始状态。随着时间的推移，在土地废弃和放牧加早季割草下，当地社区组成的逐年变化保持在相似的水平，而在其他处理下则发生了变化。随着时间的推移，在土地废弃的情况下，植被在更大范围内均质化，而在所有管理制度下，植被仍保持异质性。
5. 合成。我们的实验表明，晚季割草对于保护盐沼中的植物多样性可能是不可持续的。其他管理制度可以长期保持跨空间尺度的植物多样性和更大规模的植被异质性，但当地群落组成可能会随着时间的推移而发生变化。