1. Peat formation is a key carbon sequestration process in the terrestrial biosphere. In temperate fens, peat is mainly formed by below-ground biomass of vascular plants. Nutrient availability in temperate fens is naturally variable, and nowadays increasing due to atmospheric deposition, runoff from agriculture and mineralization of peat caused by drainage. To maintain or restore peat formation, it is important to understand how increased nutrient availability influences the main controls of peat formation, that is, below-ground biomass production and decomposition.
2. We investigated above- and below-ground biomass production and decomposition of five fen sedges (Carex spp.) grown under 12 different nutrient levels (realized with nitrogen amounts increasing exponentially across levels, with addition of phosphorous and potassium to ensure nitrogen limitation in each nutrient level) in a mesocosm experiment, designed to resemble a gradient of very low to very high nutrient availabilities in temperate fens. In addition, we measured nutrient stoichiometry in the biomass and related this to possible growth limitations and to root decomposition.
3. Our results indicate that higher biomass production at higher nutrient levels was not offset by an increase in decomposition. Increase of above- and below-ground biomass with higher nutrient levels was species-specific. Decomposition of standardized plant material in mesocosms was not dependent on the species growing in the mesocosms and showed only slight, if any, variation with differing nutrient levels. Decomposition of roots grown under different nutrient levels was mainly correlated with species identity and root lignin:cellulose ratio.
4. Our study suggests that the Carex spp. potentially peat-forming root biomass, here defined as the root biomass which is not decomposed during one growing season, increases with increasing nutrient levels: higher root biomass production is not counteracted by increasing decomposition during the growing season. Based on this pattern of positive mass balance in five common sedge species with differing growth characteristics, we propose that sedge communities establishing after rewetting have the potential for renewed peat formation regardless of the prevailing trophic level.

中文翻译：

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随着营养水平的增加，蕨类草的潜在泥炭形成生物量增加

1. 泥炭形成是陆地生物圈中一个关键的碳封存过程。在温带沼泽中，泥炭主要由维管植物的地下生物量形成。温带沼泽的养分供应量自然是可变的，现在由于大气沉积、农业径流和排水引起的泥炭矿化而增加。为了维持或恢复泥炭的形成，重要的是要了解增加的养分可用性如何影响泥炭形成的主要控制，即地下生物量的产生和分解。
2. 我们研究了在 12 种不同营养水平下生长的五种蕨类莎草 ( Carex spp.) 的地上和地下生物量生产和分解（实现了氮含量在不同水平上呈指数增加，添加磷和钾以确保每种营养素中的氮限制水平）在一个中观实验中，旨在类似于温带沼泽中非常低到非常高的营养可用性梯度。此外，我们测量了生物质中的养分化学计量，并将其与可能的生长限制和根分解相关联。
3. 我们的结果表明，在更高营养水平下更高的生物量产量并没有被分解的增加所抵消。具有较高营养水平的地上和地下生物量的增加具有物种特异性。中胚层中标准化植物材料的分解不依赖于中胚层中生长的物种，并且仅显示出轻微的（如果有的话）随不同营养水平的变化。在不同营养水平下生长的根的分解主要与物种身份和根木质素：纤维素比相关。
4. 我们的研究表明Carex spp。潜在形成泥炭的根生物量，这里定义为在一个生长季节内未分解的根生物量，随着养分水平的增加而增加：在生长季节增加分解不会抵消较高的根生物量产量。基于五种具有不同生长特征的常见莎草物种的这种正质量平衡模式，我们建议在再润湿后建立的莎草群落具有重新形成泥炭的潜力，而不管主要的营养水平如何。