High sulfate concentrations maintain low methane emissions at a constructed fen over the first seven years of ecosystem development

Establishing peat-forming plant communities: A comparison of wetland reclamation methods in Alberta's oil sands region

The Sandhill Wetland (SW) and Nikanotee Fen (NF) are two wetland research projects designed to test the viability of peatland reclamation in the Alberta oil sands post-mining landscape. To identify effective approaches for establishing peat-forming vegetation in reclaimed wetlands, we evaluated how plant introduction approaches and water level gradients influence species distribution, plant community development, and the establishment of bryophyte and peatland species richness and cover. Plant introduction approaches included seeding with a Carex aquatilis-dominated seed mix, planting C. aquatilis and Juncus balticus seedlings, and spreading a harvested moss layer transfer. Establishment was assessed 6 years after the introduction at SW and 5 years after the introduction at NF. In total, 51 species were introduced to the reclaimed wetlands, and 122 species were observed after 5 and 6 years. The most abundant species in both reclaimed wetlands was C. aquatilis, which produced dense canopies and occupied the largest water level range of observed plants. Introducing C. aquatilis also helped to exclude marsh plants such as Typha latifolia that has little to no peat accumulation potential. Juncus balticus persisted where the water table was lower and encouraged the formation of a diverse peatland community and facilitated bryophyte establishment. Various bryophytes colonized suitable areas, but the moss layer transfer increased the cover of desirable peat-forming mosses. Communities with the highest bryophyte and peatland species richness and cover (averaging 9 and 14 species, and 50%-160% cover respectively) occurred where the summer water level was between -10 and -40 cm. Outside this water level range, a marsh community of Typha latifolia dominated in standing water and a wet meadow upland community of Calamagrostis canadensis and woody species established where the water table was deeper. Overall, the two wetland reclamation projects demonstrated that establishing peat-forming vascular plants and bryophytes is possible, and community formation is dependent upon water level and plant introduction approaches. Future projects should aim to create microtopography with water tables within 40 cm of the surface and introduce vascular plants such as J. balticus that facilitate bryophyte establishment and support the development of a diverse peatland plant community.

Comparing the variations and influencing factors of CH4 emissions from paddies and wetlands under CO2 enrichment: A data synthesis in the last three decades

Understanding and quantifying the impact of elevated tropospheric carbon dioxide concentration (e [CO₂]) on methane (CH₄) globally is important for effectively assessing and mitigating climate warming. Paddies and wetlands are the two important sources of CH₄ emissions. Yet, a quantitative synthetic investigation of the effects of e [CO₂] on CH₄ emissions from paddies and wetlands on a global scale has not been conducted. Here, we conducted a meta-analysis of 488 observation cases from 40 studies to assess the long-term effects of e [CO₂] (ambient [CO₂]+ 53-400 μmol mol^-1) on CH₄ emissions and to identify the relevant key drivers. On aggregate, e [CO₂] increased CH₄ emissions by 25.7% (p < 0.05) from paddies but did not affect CH₄ emissions from wetlands (-3.29%; p > 0.05). The e [CO₂] effects on paddy CH₄ emissions were positively related to that on belowground biomass and soil-dissolved CH₄ content. However, these factors under e [CO₂] resulted in no significant change in CH₄ emissions in wetlands. Particularly, the e [CO₂]-induced abundance of methanogens increased in paddies but decreased in wetlands. In addition, tillering number of rice and water table levels affected e [CO₂]-induced CH₄ emissions in paddies and wetlands, respectively. On a global scale, CH₄ emissions changed from an increase (+0.13 and + 0.86 Pg CO₂-eq yr^-1) under short-term e [CO₂] into a decrease and no changes (-0.22 and + 0.03 Pg CO₂-eq yr^-1) under long-term e [CO₂] in paddies and wetlands, respectively. This suggested that e [CO₂]-induced CH₄ emissions from paddies and wetlands changed over time. Our results not only shed light on the different stimulative responses of CH₄ emissions to e [CO₂] from paddy and wetland ecosystems but also suggest that estimates of e [CO₂]-induced CH₄ emissions from global paddies and wetlands need to account for long-term changes in various regions.

Production in peatlands: Comparing ecosystem services of different land use options following conventional farming

Majority of Dutch peatlands are drained and used intensively as grasslands for dairy farming. This delivers high productivity but causes severe damage to ecosystem services supply. Peatland rewetting is the best way to reverse the damage, but high water levels do not fit with intensive dairy production. Paludiculture, defined as crop production under wet conditions, provides viable land use alternatives. However, performance of paludiculture is rarely compared to drainage-based agriculture. Here, we compared the performances of six land use options on peatland following a gradient of low, medium, and high water levels, including conventional and organic drainage-based dairy farming, low-input grasslands for grazing and mowing, and high-input paludiculture with reed and Sphagnum cultivation. For each land use option, we conducted environmental system analysis on model farm system defined by a literature based inventory analysis. The analysis used five ecosystem services as indicators of environmental impacts with a functional unit of 1-ha peat soil. Ecosystem services included biomass provisioning, climate, water, and nutrient regulation, and maintenance of habitat. Results showed that drainage-based dairy farming systems support high provisioning services but low regulation and maintenance services. Organic farming provides higher climate and nutrient regulation services than its conventional counterpart, but limited overall improvement due to the persistent drainage. Low-intensity grassland and paludiculture systems have high regulation and maintenance services value, but do not supply biomass provisioning comparable to the drainage-based systems. Without capitalizing the co-benefits of regulation and maintenance services, and accounting for the societal costs from ecosystem disservices including greenhouse gas emission and nitrogen pollution, it is not likely that the farmers will be incentivized to change the current farming system towards the wetter alternatives. Sustainable use of peatlands urges fundamental changes in land and water management along with the financial and policy support required.