Data from: Photosynthesis, growth, and decay traits in Sphagnum – a multispecies comparison

Peat mosses (Sphagnum) largely govern carbon sequestration in Northern Hemisphere peatlands. We investigated functional traits related to growth and decomposition in Sphagnum species. We tested the importance of environment and phylogeny in driving species traits and investigated trade-offs among them. We selected 15 globally important Sphagnum species, representing four sections (subgenera) and a range of peatland habitats. We measured rates of photosynthesis and decomposition in standard laboratory conditions as measures of innate growth and decay potential, and related this to realized growth, production, and decomposition in their natural habitats. In general, we found support for a trade-off between measures of growth and decomposition. However, the relationships are not strong, with r ranging between 0.24 and 0.45 for different measures of growth versus decomposition. Using photosynthetic rate to predict decomposition in standard conditions yielded R2 = 0.20. Habitat and section (phylogeny) affected the traits and the trade-offs. In a wet year, species from sections Cuspidata and Sphagnum had the highest production, but in a dry year, differences among species, sections, and habitats evened out. Cuspidata species in general produced easily decomposable litter, but their decay in the field was hampered, probably due to near-surface anoxia in their wet habitats. In a principal components analysis, PCA, photosynthetic capacity, production, and laboratory decomposition acted in the same direction. The species were imperfectly clustered according to vegetation type and phylogeny, so that some species clustered with others in the same section, whereas others clustered more clearly with others from similar vegetation types. Our study includes a wider range of species and habitats than previous trait analyses in Sphagnum and shows that while the previously described growth–decay trade-off exists, it is far from perfect. We therefore suggest that our species-specific trait measures offer opportunities for improvements of peatland ecosystem models. Innate qualities measured in laboratory conditions translate differently to field responses. Most dramatically, fast-growing species could only realize their potential in a wet year. The same species decompose fast in laboratory, but their decomposition was more retarded in the field than that of other species. These relationships are crucial for understanding the long-term dynamics of peatland communities.泥炭藓属（Sphagnum）植物在很大程度上主导了北半球泥炭地的碳固存（carbon sequestration）过程。本研究围绕泥炭藓物种的生长与分解相关功能性状（functional traits）展开调查，旨在探究环境与系统发育（phylogeny）对物种性状的调控作用，并解析物种间存在的性状权衡（trade-off）关系。 我们选取了15种全球分布的重要泥炭藓物种，涵盖4个组（亚属），并覆盖了多种泥炭地生境类型。我们在标准实验室条件（standard laboratory conditions）下测定了光合速率（photosynthesis rate）与分解速率（decomposition rate），以此作为物种固有生长与分解潜力的衡量指标，并将其与物种在自然生境（natural habitats）中的实际生长、生产力及分解情况进行关联分析。 总体而言，本研究证实了生长指标与分解指标间存在权衡关系，但二者的关联强度较弱：不同生长指标与分解指标间的相关系数r取值介于0.24至0.45之间。以光合速率为自变量预测实验室条件下的分解速率时，决定系数R²为0.20。 生境与组（系统发育背景）会对物种性状及性状权衡产生调控影响。在湿润年份，尖叶组（Cuspidata）与泥炭藓组（Sphagnum）的物种生产力最高；而在干旱年份，物种间、组间以及生境间的差异均趋于消失。 尖叶组（Cuspidata）的物种通常产生易分解的枯落物，但它们在野外的分解过程却受到抑制，这可能与其湿润生境中近地表缺氧的环境有关。 主成分分析（principal components analysis，PCA）结果显示，光合能力、生产力与实验室分解速率的变化方向一致。物种未能完全按照植被类型与系统发育进行聚类：部分物种与同组的其他物种聚为一类，而另一些物种则更倾向于与来自相似植被类型的物种聚类。 相较于此前针对泥炭藓的性状分析研究，本研究涵盖了更广范围的物种与生境类型。研究结果表明，尽管此前报道的生长-分解权衡关系确实存在，但该关联远非完美。因此，我们认为本研究获得的物种特异性性状数据可为泥炭地生态系统模型（peatland ecosystem models）的优化提供新的思路。 实验室条件下测定的固有性状与野外实际响应存在显著差异。最为突出的是，速生物种仅能在湿润年份实现其生长潜力。同一物种在实验室中分解速率较快，但在野外其分解过程受到的抑制程度却高于其他物种。这些关系对于理解泥炭地群落（peatland communities）的长期动态至关重要。