Kazmi Fahad Ali, Mander Ülo, Khanongnuch Ramita, Öpik Maarja, Ranniku Reti, Soosaar Kaido, Masta Mohit, Tenhovirta Salla A M, Kasak Kuno, Ah-Peng Claudine, Espenberg Mikk
Department of Geography, University of Tartu, Tartu, 51003, Estonia.
Department of Botany, University of Tartu, Tartu, 50409, Estonia.
Environ Microbiome. 2025 May 19;20(1):54. doi: 10.1186/s40793-025-00718-1.
Cloud forests are unique yet understudied ecosystems regarding CH exchange despite their significance in carbon storage. We investigated CH fluxes in peat soil and tree stems of two tropical cloud forests on Réunion Island, one featuring Erica reunionensis and the second a mix of E. reunionensis and Alsophila glaucifolia. The study examined microbiomes across below-ground (soil) and above-ground (canopy soil, leaves, and stems) forest compartments. Metagenomics and qPCR analyses targeted key genes in methanogenesis and methanotrophy in soil and above-ground samples, alongside soil physicochemical measurements. CH fluxes from peat soil and tree stems were measured using gas chromatography and portable trace gas analyzers. Peat soil in both forests acted as a CH sink (- 23.8 ± 4.84 µg C m h) and CO source (55.5 ± 5.51 µg C m h), with higher CH uptake in sites dominated by endemic tree species E. reunionensis. In forest soils, a high abundance of n-DAMO 16 S rRNA gene (3.42 × 10 ± 7 × 10 copies/g dw) was associated with nitrate levels and higher rates of CH uptake and CO emissions. NC-10 bacteria (0.1-0.3%) were detected in only the Erica forest soil, verrucomicrobial methanotrophs (0.1-3.1%) only in the mixed forest soil, whereas alphaproteobacterial methanotrophs (0.1-3.3%) were present in all soils. Tree stems in both forests were weak sinks of CH (-0.94 ± 0.4 µg C m h). The canopy soil hosted verrucomicrobial methanotrophs (0.1-0.3%). The leaves in both forests exhibited metabolic potential for CH production, e.g., exhibiting high mcrA copy numbers (3.5 × 10 ± 2.3 × 10 copies/g dw). However, no CH-cycling functional genes were detected in the stem core samples. Tropical cloud forest peat soils showed high anaerobic methanotrophy via the n-DAMO process, while aerobic methanotrophs were abundant in canopy soils. Leaves hosted methanotrophs but predominantly methanogens. These results highlight the significant differences between canopy and soil microbiomes in the CH cycle, emphasizing the importance of above-ground microbiomes in forest CH gas budgets.
云雾森林是独特但研究不足的生态系统，尽管其在碳储存方面具有重要意义，但关于其CH交换的研究仍较少。我们调查了留尼汪岛上两片热带云雾森林泥炭土和树干中的CH通量，一片以留尼汪岛石南（Erica reunionensis）为特色，另一片是留尼汪岛石南和灰绿桫椤（Alsophila glaucifolia）的混合林。该研究检查了森林地下（土壤）和地上（冠层土壤、树叶和树干）不同部分的微生物群落。宏基因组学和qPCR分析针对土壤和地上样本中甲烷生成和甲烷氧化的关键基因，并同时进行土壤理化性质测量。使用气相色谱和便携式痕量气体分析仪测量泥炭土和树干中的CH通量。两片森林中的泥炭土均为CH汇（-23.8±4.84μg C m h）和CO源（55.5±5.51μg C m h），在以特有树种留尼汪岛石南为主的地点CH吸收量更高。在森林土壤中，高丰度的n-DAMO 16S rRNA基因（3.42×10±7×10拷贝/g干重）与硝酸盐水平以及更高的CH吸收和CO排放速率相关。仅在留尼汪岛石南森林土壤中检测到NC-10细菌（0.1-0.3%），仅在混合林土壤中检测到疣微菌甲烷氧化菌（0.1-3.1%），而所有土壤中均存在α变形菌甲烷氧化菌（0.1-3.3%）。两片森林中的树干都是较弱的CH汇（-0.94±0.4μg C m h）。冠层土壤中有疣微菌甲烷氧化菌（0.1-0.3%）。两片森林中的树叶都具有CH产生的代谢潜力，例如，表现出较高的mcrA拷贝数（3.5×10±2.3×10拷贝/g干重）。然而，在树干核心样本中未检测到CH循环功能基因。热带云雾森林泥炭土通过n-DAMO过程表现出较高的厌氧甲烷氧化作用，而冠层土壤中有丰富的好氧甲烷氧化菌。树叶中有甲烷氧化菌，但主要是产甲烷菌。这些结果突出了冠层和土壤微生物群落在CH循环中的显著差异，强调了地上微生物群落在森林CH气体收支中的重要性。
