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AbstractTropical peatlands are a significant carbon store and contribute to global carbon dioxide (CO2) and methane (CH4) emissions. Tropical peatlands are threatened by both land use and climate change, including the alteration of regional precipitation patterns, and the 3–4 °C predicted warming by 2100. Plant communities in tropical peatlands can regulate greenhouse gas (GHG) fluxes through labile carbon inputs, but the extent to which these inputs regulate the temperature response of CO2 and CH4 production in tropical peat remains unclear. We conducted an anoxic incubation experiment using three peat types of contrasting botanical origin to assess how carbon addition affects the temperature response (Q10) of CO2 and CH4 production. Peats from forested peatlands in Panama and Malaysia, and a converted oil palm and pineapple intercropping system in Malaysia, differed significantly in redox potential, total carbon and carbon: nitrogen ratio. The production of CO2 and CH4 varied significantly among peat types and increased with increasing temperature, with Q10s for both gases of 1.4. Carbon addition further increased gas fluxes, but did not influence the Q10 for CO2 or CH4 production or significantly affect the Q10 of either gas. These findings demonstrate that the production of CO2 and CH4 in tropical peat is sensitive to warming and varies among peat types, but that the effect of root inputs in altering Q10 appears to be limited.

AbstractTropical wetlands are not included in Earth system models, despite being an important source of methane (CH4) and contributing a large fraction of carbon dioxide (CO2) emissions from land use, land use change, and forestry in the tropics. This review identifies a remarkable lack of data on the carbon balance and gas fluxes from undisturbed tropical wetlands, which limits the ability of global change models to make accurate predictions about future climate. We show that the available data on in situ carbon gas fluxes in undisturbed forested tropical wetlands indicate marked spatial and temporal variability in CO2and CH4emissions, with exceptionally large fluxes in Southeast Asia and the Neotropics. By upscaling short‐term measurements, we calculate that approximately 90 ± 77 Tg CH4year−1and 4540 ± 1480 Tg CO2year−1are released from tropical wetlands globally. CH4fluxes are greater from mineral than organic soils, whereas CO2fluxes do not differ between soil types. The high CO2and CH4emissions are mirrored by high rates of net primary productivity and litter decay. Net ecosystem productivity was estimated to be greater in peat‐forming wetlands than on mineral soils, but the available data are insufficient to construct reliable carbon balances or estimate gas fluxes at regional scales. We conclude that there is an urgent need for systematic data on carbon dynamics in tropical wetlands to provide a robust understanding of how they differ from well‐studied northern wetlands and allow incorporation of tropical wetlands into global climate change models.

Peatlands are a critical carbon store comprising 30% of the Earth’s terrestrial soil carbon. Sphagnum mosses comprise up to 90% of peat in the northern hemisphere but impacts of climate change on Sphagnum mosses are poorly understood, limiting development of sustainable peatland management and restoration. This study investigates the effects of elevated atmospheric CO2 (eCO2) (800 ppm) and hydrology on the growth of Sphagnum fallax, Sphagnum capillifolium and Sphagnum papillosum and greenhouse gas fluxes from moss–peat mesocosms. Elevated CO2 levels increased Sphagnum height and dry weight but the magnitude of the response differed among species. The most responsive species, S. fallax, yielded the most biomass compared to S. papillosum and S. capillifolium. Water levels and the CO2 treatment were found to interact, with the highest water level (1 cm below the surface) seeing the largest increase in dry weight under eCO2 compared to ambient (400 ppm) concentrations. Initially, CO2 flux rates were similar between CO2 treatments. After week 9 there was a consistent three-fold increase of the CO2 sink strength under eCO2. At the end of the experiment, S. papillosum and S. fallax were greater sinks of CO2 than S. capillifolium and the − 7 cm water level treatment showed the strongest CO2 sink strength. The mesocosms were net sources of CH4 but the source strength varied with species, specifically S. fallax produced more CH4 than S. papillosum and S. capillifolium. Our findings demonstrate the importance of species selection on the outcomes of peatland restoration with regards to Sphagnum’s growth and GHG exchange.

Los ecosistemas de turberas tropicales son un componente importante del ciclo global del carbono y presentan una variedad de tipos de vegetación distintos, pero el alcance de los vínculos entre las especies de plantas contrastantes, la biogeoquímica de la turba y los flujos de gases de efecto invernadero sigue sin estar claro. Aquí evaluamos cómo la vegetación afecta la variación a pequeña escala de la dinámica del carbono de las turberas tropicales cuantificando las emisiones de gases de efecto invernadero in situ durante 1 mes utilizando la técnica de cámara cerrada y las propiedades de la materia orgánica de la turba utilizando la pirólisis Rock-Eval 6 dentro de las zonas de enraizamiento de las palmeras del dosel y los árboles de hoja perenne de hoja ancha. Los flujos medios de metano variaron de 0.56 a 1.2 mg m−2 h−1 y fueron significativamente mayores cerca de los tallos de las plantas. Además, el pH, que oscila entre 3,95 y 4,16, fue significativamente mayor más cerca de los tallos. Un modelo de tres piscinas de estabilidad térmica de la materia orgánica (piscinas lábiles, intermedias y pasivas) indicó una gran piscina lábil en turba superficial (35–42%), con reservas de carbono equivalentes de 2236–3065 g m−2. Los flujos de metano fueron impulsados por la disponibilidad general de sustrato en lugar de por cualquier depósito de carbono específico. No hay propiedades de turba correlacionadas con los flujos de dióxido de carbono, lo que sugiere un papel significativo para la respiración de la raíz, la descomposición aeróbica y/o la oxidación del metano. Estos resultados demuestran cómo el tipo de vegetación y los insumos, y las propiedades de la materia orgánica de la turba son determinantes importantes de la variación espacial a pequeña escala de los flujos de metano en las turberas tropicales que se ven afectadas por el cambio climático y de uso de la tierra. Les écosystèmes des tourbières tropicales sont une composante importante du cycle mondial du carbone et présentent une gamme de types de végétation distincts, mais l'étendue des liens entre les espèces végétales contrastées, la biogéochimie de la tourbe et les flux de gaz à effet de serre reste incertaine. Ici, nous avons évalué comment la végétation affecte la variation à petite échelle de la dynamique du carbone des tourbières tropicales en quantifiant les émissions de gaz à effet de serre in situ sur 1 mois en utilisant la technique à chambre fermée, et les propriétés de la matière organique de la tourbe en utilisant la pyrolyse Rock-Eval 6 dans les zones d'enracinement des palmiers à canopée et des arbres à feuilles persistantes à feuilles larges. Les flux moyens de méthane variaient de 0,56 à 1,2 mg m−2 h−1 et étaient significativement plus proches des tiges des plantes. De plus, le pH, allant de 3,95 à 4,16, était significativement plus proche des tiges. Un modèle à trois bassins de stabilité thermique de la matière organique (bassins labile, intermédiaire et passif) a indiqué un grand bassin labile dans la tourbe de surface (35–42%), avec des stocks de carbone équivalents de 2236-3065 g m−2. Les flux de méthane ont été déterminés par la disponibilité globale du substrat plutôt que par un pool de carbone spécifique. Aucune propriété de la tourbe n'est corrélée aux flux de dioxyde de carbone, ce qui suggère un rôle important pour la respiration racinaire, la décomposition aérobie et/ou l'oxydation du méthane. Ces résultats démontrent comment le type de végétation et les intrants, ainsi que les propriétés de la matière organique de la tourbe sont des déterminants importants de la variation spatiale à petite échelle des flux de méthane dans les tourbières tropicales qui sont affectées par le changement climatique et l'utilisation des terres. Tropical peatland ecosystems are a significant component of the global carbon cycle and feature a range of distinct vegetation types, but the extent of links between contrasting plant species, peat biogeochemistry and greenhouse gas fluxes remains unclear. Here we assessed how vegetation affects small scale variation of tropical peatland carbon dynamics by quantifying in situ greenhouse gas emissions over 1 month using the closed chamber technique, and peat organic matter properties using Rock-Eval 6 pyrolysis within the rooting zones of canopy palms and broadleaved evergreen trees. Mean methane fluxes ranged from 0.56 to 1.2 mg m−2 h−1 and were significantly greater closer to plant stems. In addition, pH, ranging from 3.95 to 4.16, was significantly greater closer to stems. A three pool model of organic matter thermal stability (labile, intermediate and passive pools) indicated a large labile pool in surface peat (35–42%), with equivalent carbon stocks of 2236–3065 g m−2. Methane fluxes were driven by overall substrate availability rather than any specific carbon pool. No peat properties correlated with carbon dioxide fluxes, suggesting a significant role for root respiration, aerobic decomposition and/or methane oxidation. These results demonstrate how vegetation type and inputs, and peat organic matter properties are important determinants of small scale spatial variation of methane fluxes in tropical peatlands that are affected by climate and land use change. تعد النظم الإيكولوجية لأراضي الخث الاستوائية مكونًا مهمًا في دورة الكربون العالمية وتتميز بمجموعة من أنواع النباتات المتميزة، لكن مدى الروابط بين أنواع النباتات المتناقضة والكيمياء الجيولوجية الحيوية للخث وتدفقات غازات الدفيئة لا يزال غير واضح. قمنا هنا بتقييم كيفية تأثير الغطاء النباتي على التباين صغير النطاق لديناميكيات الكربون في الأراضي الخثية الاستوائية من خلال قياس انبعاثات غازات الدفيئة في الموقع على مدى شهر واحد باستخدام تقنية الغرفة المغلقة، وخصائص المواد العضوية الخثية باستخدام الانحلال الحراري لـ Rock - Eval 6 داخل مناطق تجذير أشجار النخيل المظلية والأشجار دائمة الخضرة ذات الأوراق العريضة. تراوح متوسط تدفقات الميثان من 0.56 إلى 1.2 ملغ م -2 ساعة-1 وكانت أكبر بكثير بالقرب من سيقان النبات. بالإضافة إلى ذلك، كان الأس الهيدروجيني، الذي يتراوح من 3.95 إلى 4.16، أكبر بكثير من السيقان. أشار نموذج ثلاثي البرك للاستقرار الحراري للمواد العضوية (البرك العطوبة والمتوسطة والسلبية) إلى بركة عطوبة كبيرة في الخث السطحي (35-42 ٪)، بمخزونات كربون مكافئة تبلغ 2236-3065 جم م−2. كانت تدفقات الميثان مدفوعة بتوافر الركيزة بشكل عام بدلاً من أي تجمع كربون محدد. لا توجد خصائص خث مرتبطة بتدفقات ثاني أكسيد الكربون، مما يشير إلى دور مهم لتنفس الجذر، والتحلل الهوائي و/أو أكسدة الميثان. توضح هذه النتائج كيف أن نوع الغطاء النباتي والمدخلات، وخصائص المادة العضوية الخثية هي محددات مهمة للتغير المكاني صغير النطاق لتدفقات الميثان في الأراضي الخثية الاستوائية التي تتأثر بتغير المناخ واستخدام الأراضي.