Sirvi Autor "Kazmi, Fahad Ali" järgi

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Distinct microbial communities drive methane cycling in below- and above-ground compartments of tropical cloud forests growing on peat
(2025) 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
Cloud forests are unique yet understudied ecosystems regarding CH4 exchange despite their significance in carbon storage. We investigated CH4 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. CH4 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 CH4 sink (− 23.8 ± 4.84 µg C m− 2 h− 1) and CO2 source (55.5 ± 5.51 µg C m− 2 h− 1), with higher CH4 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 × 107 ± 7 × 106 copies/g dw) was associated with nitrate levels and higher rates of CH4 uptake and CO2 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 CH4 (-0.94 ± 0.4 µg C m− 2 h− 1). The canopy soil hosted verrucomicrobial methanotrophs (0.1–0.3%). The leaves in both forests exhibited metabolic potential for CH4 production, e.g., exhibiting high mcrA copy numbers (3.5 × 105 ± 2.3 × 105 copies/g dw). However, no CH4-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 CH4 cycle, emphasizing the importance of above-ground microbiomes in forest CH4 gas budgets.
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Nitrogen cycling genes abundance in soil and aboveground compartments of tropical peatland cloud forests and a wetland on Réunion Island
(Scientific Reports, 2025) Kazmi, Fahad Ali; Mander, Ülo; Ranniku, Reti; Öpik, Maarja; Püssa, Kersti; Soosaar, Kaido; Kasak, Kuno; Masta, Mohit; Ah-Peng, Claudine; Espenberg, Mikk
Peatland cloud forests, characterized by high altitude and humidity, are among the least-studied tropical ecosystems despite their significance for endemism and the bioavailable nitrogen (N) that can be emitted as N2O. While research has mainly focused on soil, the above-ground microbial N cycle remains largely unexplored. We quantified microbial N cycling genes across ecosystem compartments (soil, canopy soil, tree stems, and leaves) in relation to N2O and N2 fluxes and soil physicochemical properties in two peatland cloud forests and a wetland on Réunion Island. Complete denitrification minimized N2O emissions and increased N2 fluxes in wetland soils. In cloud forest soils, archaeal nitrification primarily produced nitrate (NO3–), while low pH potentially slowed denitrification, resulting in minimal N2O emissions. Soil N-fixers were more abundant in Erica reunionensis-dominated forests than in mixed forests. Tree stems varied between weak N2O sinks and sources, with fluxes unrelated to gene abundances in stems. High prokaryotic and fungal nirK gene abundance in forest canopy soil suggests potential for above-ground denitrification in wet conditions. nosZ-I genes found in forest canopy soil and leaves (E. reunionensis, Alsophila glaucifolia, and Typha domingensis) indicate that plants, including forest canopy, may play a significant role in the reduction of N2O.
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Springtime soil and tree stem greenhouse gas fluxes and the related soil microbiome pattern in a drained peatland forest
(2025) Ranniku, Reti; Kazmi, Fahad Ali; Espenberg, Mikk; Truupõld, Joosep; Escuer‑Gatius, Jordi; Mander, Ülo; Soosaar, Kaido
Spring can be a critical time of year for stem and soil methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions as soil freeze–thaw events can be hot moments of gas release. Greenhouse gas fluxes from soil, Downy birch (Betula pubescens) and Norway spruce (Picea abies) stems were quantified using chamber systems and gas analysers in spring 2023 in a northern drained peatland forest. Dissolved gas concentrations in birch sap and soil water, environmental parameters, soil chemistry, and functional gene abundances in the soil were determined. During spring, initially low soil and stem CH4, N2O, and CO2 emissions increased towards late April. Temperature emerged as the primary driver of soil and stem fluxes, alongside photosynthetically active radiation influencing stem fluxes. Soil hydrologic conditions had minimal short-term impact. No clear evidence linked stem CH4 emissions to birch sap gas concentrations, while relationships existed for CO2. Functional gene abundances of the N and CH4-cycles changed between measurement days. Potential for methanogenesis and complete denitrification was higher under elevated soil water content, shifting to methanotrophy and incomplete denitrification as the study progressed. However, our results highlight the need for further analysis of relationships between microbial cycles and GHG fluxes under different environmental conditions, including identifying soil microbial processes in soil layers where tree roots absorb water.
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The role of microbiome in CH₄ and N₂O fluxes in temperate and tropical peatland forests
(Tartu Ülikooli Kirjastus, 2025-08-18) Kazmi, Fahad Ali; Espenberg, Mikk, juhendaja; Mander, Ülo, juhendaja; Tartu Ülikool. Loodus ja täppisteaduste valdkond
Turbaalad aitavad kliimamuutust leevendada sidudes süsinikku. Soode kuivendamisel eraldub enam kasvuhoonegaase (KHG), nagu süsihappegaas (CO₂), dilämmastikoksiid (N₂O) ja metaan (CH₄), mis soodustavad globaalset kliimasoojenemist ja lõhuvad osoonikihti. Käesolev väitekiri keskendus nii parasvöötme (Eesti) kui troopilise piirkonna (Réunioni saar) soometsadele, et uurida mikroobikooslusi ja nendega seotud KHG voogude dünaamikat. Parasvöötme kuivendatud soometsas olid pikaajalised N₂O emissioonid seotud arhede, bakterite ja seentega, kes osalevad erinevates lämmastikuringe protsessides. N₂O emissioonid olid kõrgemad kevadise külmumise-sulamistsükli ajal. Kui külmunud pealmine mullakiht sulas, suurenes mittetäielik denitrifikatsioon, mille tulemusena tõusis N₂O emissioon. Ilmade soojenedes hakkas N₂O-d tarbivate mikroobide arvukus ületama N₂O tootjaid, mis viis emissioonide vähenemiseni. Samal ajal jäid kevadised mulla CH₄ vood madalaks, kuid puutüvedest hakkas enam CH₄ eralduma. See viitab CH₄ tootmisele sügavamates mullakihtides, mis transporditi mulla alumistest kihtidest juurte kaudu tüvedesse. Troopiliste soometsade mullast eraldus vähe N₂O-d, sest madal pH aeglustas N₂O-d tootvat mittetäielikku denitrifikatsiooni ning N₂O-d tarbivate mikroobide arvukus oli suur. Samas sidusid need mullad CH₄ ja domineerivaks protsessiks oli n-DAMO (nitraadist sõltuv anaeroobne CH₄ oksüdatsioon). Puude tüvedele kogunev lehevaris, surnud taimne materjal ja tolm ehk nn võramuld sisaldas samuti mikroorganisme, kes osalesid KHG vahetuses, viidates sellele, et puude võramuld osaleb aktiivselt biogeokeemilistes tsüklites. Lisaks leiti, et ka lehed sisaldasid mikroobe, kes toodavad CH₄ ja tarbivad N₂O-d. See uurimus toob esile mikroobide olulise, kuid sageli tähelepanuta jääva rolli soometsade KHG-de dünaamikas. Mikroobseid protsesse mõistes on võimalik parandada soometsade majandamist ja kaitset ning prognoosida paremini KHG emissioone nendest ökosüsteemidest.