Valach Alex C, Kasak Kuno, Hemes Kyle S, Anthony Tyler L, Dronova Iryna, Taddeo Sophie, Silver Whendee L, Szutu Daphne, Verfaillie Joseph, Baldocchi Dennis D
Ecosystem Science Division, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, United States of America.
Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia.
PLoS One. 2021 Mar 25;16(3):e0248398. doi: 10.1371/journal.pone.0248398. eCollection 2021.
Inundated wetlands can potentially sequester substantial amounts of soil carbon (C) over the long-term because of slow decomposition and high primary productivity, particularly in climates with long growing seasons. Restoring such wetlands may provide one of several effective negative emission technologies to remove atmospheric CO2 and mitigate climate change. However, there remains considerable uncertainty whether these heterogeneous ecotones are consistent net C sinks and to what degree restoration and management methods affect C sequestration. Since wetland C dynamics are largely driven by climate, it is difficult to draw comparisons across regions. With many restored wetlands having different functional outcomes, we need to better understand the importance of site-specific conditions and how they change over time. We report on 21 site-years of C fluxes using eddy covariance measurements from five restored fresh to brackish wetlands in a Mediterranean climate. The wetlands ranged from 3 to 23 years after restoration and showed that several factors related to restoration methods and site conditions altered the magnitude of C sequestration by affecting vegetation cover and structure. Vegetation established within two years of re-flooding but followed different trajectories depending on design aspects, such as bathymetry-determined water levels, planting methods, and soil nutrients. A minimum of 55% vegetation cover was needed to become a net C sink, which most wetlands achieved once vegetation was established. Established wetlands had a high C sequestration efficiency (i.e. the ratio of net to gross ecosystem productivity) comparable to upland ecosystems but varied between years undergoing boom-bust growth cycles and C uptake strength was susceptible to disturbance events. We highlight the large C sequestration potential of productive inundated marshes, aided by restoration design and management targeted to maximise vegetation extent and minimise disturbance. These findings have important implications for wetland restoration, policy, and management practitioners.
由于分解缓慢且初级生产力高，尤其是在生长季节较长的气候条件下，被淹没的湿地有可能长期封存大量土壤碳。恢复此类湿地可能是几种有效的负排放技术之一，可用于去除大气中的二氧化碳并缓解气候变化。然而，这些异质生态交错带是否始终是净碳汇以及恢复和管理方法在多大程度上影响碳固存，仍存在相当大的不确定性。由于湿地碳动态在很大程度上受气候驱动，因此很难在不同地区之间进行比较。许多恢复的湿地具有不同的功能结果，我们需要更好地了解特定地点条件的重要性以及它们如何随时间变化。我们报告了在地中海气候下，对五个从淡水到微咸水恢复湿地进行涡度协方差测量得到的21个站点年的碳通量情况。这些湿地在恢复后3至23年不等，结果表明，与恢复方法和站点条件相关的几个因素通过影响植被覆盖和结构改变了碳固存的规模。植被在重新注水后的两年内就已建立，但根据设计方面的不同，如由水深测量确定的水位、种植方法和土壤养分，其发展轨迹有所不同。要成为净碳汇，植被覆盖率至少需要达到55%，大多数湿地在植被建立后就达到了这一水平。已建立的湿地具有与陆地生态系统相当的高碳固存效率（即净生态系统生产力与总生态系统生产力的比率），但在经历兴衰生长周期的年份之间有所不同，碳吸收强度容易受到干扰事件的影响。我们强调通过旨在最大限度扩大植被范围并最小化干扰的恢复设计和管理，生产性被淹没沼泽具有巨大的碳固存潜力。这些发现对湿地恢复、政策和管理从业者具有重要意义。
