Long-term fate of nitrogen fixation in Pleurozium schreberi Brid (Mit.) moss carpets in boreal forests
Long-term fate of nitrogen fixation in Pleurozium schreberi Brid (Mit.) moss carpets in boreal forests
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DOI：
10.1016/j.apsoil.2021.104215
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发表时间：
2021-09-09
影响因子：
4.8
通讯作者：
Arroniz-Crespo, Maria
中科院分区：
文献类型：
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作者：
DeLuca, Thomas H.;Zackrisson, Olle;Arroniz-Crespo, Maria
羽藓和相关的蓝藻作为一个重要的氮（N）的来源，在北方森林，然而，很少有研究有效地跟踪N2固定原位超过一年。本研究的目的是评估长期的命运N2固定在羽毛苔藓地毯在北方森林的北方瑞典。我们进行了为期7年的15N2（g）标记和跟踪实验，在北方森林与苔藓底层为主的PleuroziumschreberiBrid（Mitt）。有和没有苔藓存在的森林地面的中生态系统暴露于10%15N2（g）的大气5天后，苔藓，灌木，松树幼苗和O层的样品，在不同的时间间隔和分析三角洲15N。在第七年，将地块分割并燃烧，以评估火对释放苔藓氮的影响，以供苏格兰松（Pinus sylvestris L.）吸收。幼苗用15 N 2（g）处理的羽藓在标记后一个月高度富集15 N，随后在7年后下降到原始绿色组织中15 N富集的13%。没有可测量的15 N富集观察到在灌木或O地平线标记苔藓的存在下，直到超过五年后的标记实验。火可以释放苔藓氮，但我们没有观察到直接影响的松树幼苗吸收氮的火。这一长期的研究表明，N2固定的蓝藻在羽毛苔藓地毯保存在苔藓组织中的时间较长，并慢慢转移到森林土壤O层的苔藓组织分解，这表明苔藓N2固定是最重要的生态系统N源在长时间尺度。
Feather mosses and associated cyanobacteria serve as an important source of nitrogen (N) in boreal forests; however, few studies have effectively traced the N2 fixation in-situ for more than one year. The purpose of this study was to assess the long-term fate of N2 fixed in feather moss carpets in boreal forests of northern Sweden. We conducted a seven-year 15N2(g) labelling and tracing experiment in a boreal forest with a moss bottom layer dominated by Pleurozium schreberi Brid (Mitt). Mesocosms of forest floor with and without mosses present were exposed to a 10% 15N2(g) atmosphere for five days after which samples of moss, shrub, pine seedling and O horizon were taken at varied intervals and analysed for delta 15N. Plots were split and burned in year seven to assess the effect of fire on liberating moss N for uptake by Scots pine (Pinus sylvestris L.) seedlings. Feather mosses treated with 15N2(g) were highly enriched in 15N one month after labelling which subsequently declined after seven years to 13% of the original 15N enrichment in green tissue. No measurable 15N enrichment was observed in shrubs or the O horizon in the presence of labelled mosses until greater than five years after the labelling experiment. Fire can liberate moss N, but we did not observe a direct effect of fire on N uptake by pine seedlings. This long-term study indicates that N2 fixed by cyanobacteria in feather moss carpets is conserved in moss tissue for extended periods and slowly transferred to the forest soil O horizon as moss tissue decomposes suggesting that moss N2 fixation is most important as an ecosystem N source at long time scales.