Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, VIC, Australia.
Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Geelong, VIC, Australia.
J Environ Manage. 2020 Feb 15;256:109971. doi: 10.1016/j.jenvman.2019.109971. Epub 2019 Dec 16.
Wetland ecosystems have a disproportionally large influence on the global carbon cycle. They can act as carbon sinks or sources depending upon their location, type, and condition. Rehabilitation of wetlands is gaining popularity as a nature-based approach to helping mitigate climate change; however, few studies have empirically tested the carbon benefits of wetland restoration, especially in freshwater environments. Here we investigated the effects of passive rehabilitation (i.e. fencing and agricultural release) of 16 semi-arid rain-filled freshwater wetlands in southeastern Australia. Eight control sites were compared with older (>10 year) or newer (2-5 year) rehabilitated sites, dominated by graminoids or eucalypts. Carbon stocks (soils and plant biomass), and emissions (carbon dioxide - CO; and methane - CH) were sampled across three seasons, representing natural filling and drawdown, and soil microbial communities were sampled in spring. We found no significant difference in soil carbon or greenhouse gas emissions between rehabilitated and control sites, however, plant biomass was significantly higher in older rehabilitated sites. Wetland carbon stocks were 19.21 t C ha and 2.84 t C ha for soils (top 20 cm; n = 137) and plant biomass (n = 288), respectively. Hydrology was a strong driver of wetland greenhouse gas emissions. Diffusive fluxes (n = 356) averaged 117.63 mmol CO m d and 2.98 mmol CH m d when wet, and 124.01 mmol CO m d and -0.41 mmol CH m d when dry. Soil microbial community richness was nearly 2-fold higher during the wet phase than the dry phase, including relative increases in Nitrososphaerales, Myxococcales and Koribacteraceae and methanogens Methanobacteriales. Vegetation type significantly influenced soil carbon, aboveground carbon, and greenhouse gas emissions. Overall, our results suggest that passive rehabilitation of rain-filled wetlands, while valuable for biodiversity and habitat provisioning, is ineffective for increasing carbon gains within 20 years. Carbon offsetting opportunities may be better in systems with faster sediment accretion. Active rehabilitation methods, particularly that reinstate the natural hydrology of drained wetlands, should also be considered.
湿地生态系统对全球碳循环有不成比例的巨大影响。它们可以作为碳汇或碳源，具体取决于它们的位置、类型和条件。湿地恢复作为一种基于自然的帮助缓解气候变化的方法越来越受欢迎；然而，很少有研究实证检验湿地恢复的碳效益，特别是在淡水环境中。在这里，我们调查了澳大利亚东南部 16 个半干旱雨水填充淡水湿地被动恢复（即围栏和农业释放）的影响。将 8 个对照点与较老（> 10 年）或较新（2-5 年）的恢复点进行比较，这些恢复点以禾本科植物或桉树为主。在三个季节（代表自然填充和排空）中采样了碳储量（土壤和植物生物量）和排放（二氧化碳-CO 和甲烷-CH），并在春季采样了土壤微生物群落。我们没有发现恢复区和对照区之间土壤碳或温室气体排放有显著差异，但较老的恢复区的植物生物量明显更高。湿地碳储量为 19.21 t C ha 和 2.84 t C ha，分别为土壤（顶部 20 cm；n = 137）和植物生物量（n = 288）。水文是湿地温室气体排放的主要驱动因素。扩散通量（n = 356）在湿润时平均为 117.63 mmol CO m d 和 2.98 mmol CH m d，在干燥时平均为 124.01 mmol CO m d 和-0.41 mmol CH m d。土壤微生物群落丰富度在湿润期几乎是干燥期的两倍，包括硝化螺旋菌目、粘球菌目和 Koribacteraceae 和产甲烷菌 Methanobacteriales 的相对增加。植被类型对土壤碳、地上碳和温室气体排放有显著影响。总的来说，我们的结果表明，雨水填充湿地的被动恢复虽然对生物多样性和生境供应有价值，但在 20 年内对增加碳增益无效。在具有更快泥沙淤积的系统中，碳抵消机会可能更好。还应考虑主动恢复方法，特别是恢复排水湿地自然水文的方法。
