Wetlands have a major influence on the global carbon cycle, with capacity to act as carbon ‘sinks’ or ‘sources’. The source-sink capacity of wetlands is governed by microbially-mediated biogeochemical processes, which are furthermore regulated by environmental conditions. With growing interest in nature-based climate solutions, policymakers and resource managers seek information on ways how wetlands can be managed to maximize carbon drawdown. Here, we explored how rehabilitation (i.e., fencing and grazing removal) influences greenhouse gas (GHG) emissions and soil biogeochemistry (microbial communities and soil quality) from semi-arid, rain-filled freshwater wetlands in south-eastern Australia. Specifically, we investigated the carbon and microbes response under major local environmental factors, such as vegetation type (graminoids vs eucalyptus tree) and seasonal hydroperiod (spring vs autumn), across wetlands that are currently used for grazing or cropping and those that have been under fencing rehabilitation for up to 20 years. We found that rehabilitation did not reduce CO₂ and CH₄ emissions, rather CH₄ flux rates were elevated when the wetlands were flooded (spring). Anaerobic conditions from spring waterlogged soils also increased microbial diversity by 2.6-fold, and influenced the relative abundance of putative methane oxidizers (Nitrososphaerales and Mixococcales) and methanogenic archaea (Methanomicrobia, Methanobacteria). Organic matter quality (measured as C:N ratio) was reduced by the removal of grazing pressure in eucalyptus-dominated sites only. Soil quality, influenced by vegetation type, also had a significant impact on relative abundance of putative nitrogen and carbon cyclers. Overall, our results suggest that fencing rehabilitation in semi-arid rain-filled wetlands had a minor impact on microbial dynamics and carbon processes, overshadowed by the influence of the water table and vegetation type. Focusing future research on spatial and temporal patterns of carbon and microbe rehabilitation responses will help managers devise the most effective rehabilitation practice within a particular geographical area.

湿地对全球碳循环具有重大影响，具有充当碳“汇”或“源”的能力。湿地的源汇能力是由微生物介导的生物地球化学过程控制的，而生物地球化学过程又受环境条件的调节。随着人们对基于自然的气候解决方案的兴趣日益浓厚，政策制定者和资源经理寻求有关如何管理湿地以最大限度地减少碳排放的信息。在这里，我们探索了恢复（即围栏和放牧清除）如何影响来自澳大利亚东南部半干旱，充满雨水的淡水湿地的温室气体（GHG）排放和土壤生物地球化学（微生物群落和土壤质量）。具体来说，我们调查了主要当地环境因素下的碳和微生物响应，例如目前用于放牧或耕种的湿地以及经过围栏恢复长达20年的湿地上的植被类型（类胡薄荷vs桉树）和季节性水周期（春季vs秋季）。我们发现，康复并不能减少二氧化碳₂和CH ₄排放，而不是CH ₄当湿地被洪水淹没（春季）时，通量率升高。春季涝渍土壤中的厌氧条件也使微生物多样性增加了2.6倍，并影响了假定的甲烷氧化剂（硝化球菌和混合球菌）和产甲烷的古细菌（甲烷菌，甲烷菌）的相对丰度。仅通过消除桉树占主导地位的地点的放牧压力，降低了有机质（以C：N比衡量）。土壤质量受植被类型的影响，对假定的氮和碳循环剂的相对丰度也有显着影响。总体而言，我们的结果表明，在半干旱，充满雨水的湿地进行栅栏恢复对微生物动力学和碳过程的影响较小，但受到地下水位和植被类型的影响而被遮盖。