Sphagnan in Sphagnum-dominated peatlands: bioavailability and effects on organic matter stabilization

IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES Biogeochemistry Pub Date : 2024-04-10 DOI:10.1007/s10533-024-01134-2
Lauren Bryan, Rachel Shaw, Erik Schoonover, Alexis Koehl, Suzanne DeVries-Zimmerman, Michael Philben
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Abstract

The unique pectin-like carbohydrate “sphagnan” has been shown to protect organic matter from microbial decomposition in Sphagnum-dominated peatlands. However, the bioavailability of sphagnan has not been evaluated, and it is not known if it persists or continues to affect decomposition processes over the long timescales of peat formation. To address this, we assessed the connection between sphagnan content and organic matter decomposition rates in a temperate peatland near Fennville, MI, USA. We compared the effects of sphagnan over two timescales: (1) a short-term litter incubation assay using mosses from different peatland microtopographies; and (2) oxic and anoxic incubation assays of peat collected from multiple depths within the peat profile, reflecting a natural long-term decomposition continuum. On both timescales, we hypothesized that higher sphagnan content would be associated with lower decomposition rates, and that sphagnan would be selectively preserved compared to bulk C and other carbohydrates. The litter decomposition experiment supported both hypotheses, as higher sphagnan content was associated with lower mass loss, and sphagnan content increased due to selective preservation. In the peat, we observed weak but significant correlations between the relative abundance of sphagnan (as a fraction of total non-cellulosic sugars) and both aerobic and anaerobic respiration rates. This relationship was stronger in cores collected from hollow microtopographies than those from hummocks. However, there was not a significant relationship between respiration rates and the total (C-normalized) sphagnan content. Sphagnan content increased with depth in the peat profile, indicating selective preservation compared to bulk C. Additionally, we observed the accumulation of non-cellulosic glucose in the deep peat, likely derived from microbial exopolysaccharides. Together, these results indicate that sphagnan persists in the catotelm and continues to contribute to the long-term stabilization of organic matter in Sphagnum-rich peatlands, although the weak relationship with respiration indicates that its influence is relatively minor.

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以泥炭藓为主的泥炭地中的泥炭藓:生物利用率和对有机物稳定性的影响
研究表明,在以泥炭藓为主的泥炭地中,独特的果胶状碳水化合物 "斯帕格南 "可保护有机物不被微生物分解。然而,斯帕格南的生物利用率尚未得到评估,而且它是否会在泥炭形成的漫长时间尺度内持续或继续影响分解过程也不得而知。为了解决这个问题,我们在美国密歇根州芬维尔附近的温带泥炭地评估了泥炭酚含量与有机物分解率之间的联系。我们比较了斯帕格南在两个时间尺度上的影响:(1) 使用来自不同泥炭地微地形的苔藓进行短期枯落物培养试验;(2) 对从泥炭剖面内多个深度收集的泥炭进行缺氧和缺氧培养试验,以反映自然长期分解的连续性。在这两个时间尺度上,我们假设泥炭酚含量越高,分解率就越低,而且泥炭酚与大体积碳和其他碳水化合物相比会被选择性地保存下来。枯落物分解实验支持了这两个假设,因为较高的石炭酸含量与较低的质量损失有关,而石炭酸含量的增加则是由于选择性保存。在泥炭中,我们观察到泥炭酚的相对丰度(占非纤维素糖总量的一部分)与有氧和无氧呼吸速率之间存在微弱但显著的相关性。这种关系在中空微地形采集的岩芯中比在沼泽采集的岩芯中更为明显。不过,呼吸速率与岩屑总含量(C 归一化)之间的关系并不明显。此外,我们还观察到泥炭深处非纤维素葡萄糖的积累,这可能来自微生物外多糖。总之,这些结果表明,泥炭藻在泥炭层中持续存在,并继续为富含泥炭藻的泥炭地有机物的长期稳定做出贡献,尽管与呼吸作用的关系不大,表明其影响相对较小。
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来源期刊
Biogeochemistry
Biogeochemistry 环境科学-地球科学综合
CiteScore
7.10
自引率
5.00%
发文量
112
审稿时长
3.2 months
期刊介绍: Biogeochemistry publishes original and synthetic papers dealing with biotic controls on the chemistry of the environment, or with the geochemical control of the structure and function of ecosystems. Cycles are considered, either of individual elements or of specific classes of natural or anthropogenic compounds in ecosystems. Particular emphasis is given to coupled interactions of element cycles. The journal spans from the molecular to global scales to elucidate the mechanisms driving patterns in biogeochemical cycles through space and time. Studies on both natural and artificial ecosystems are published when they contribute to a general understanding of biogeochemistry.
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