Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
University of Chinese Academy of Sciences, Beijing, China.
Glob Chang Biol. 2024 Sep;30(9):e17495. doi: 10.1111/gcb.17495.
Drained wetlands are thought to be carbon (C) source hotspots, and rewetting is advocated to restore C storage in drained wetlands for climate change mitigation. However, current assessments of wetland C balance mainly focus on vertical fluxes between the land and atmosphere, frequently neglecting lateral carbon fluxes and land-use effects. Here, we conduct a global synthesis of 893 annual net ecosystem C balance (NECB) measures that include net ecosystem exchange of CO, along with C input via manure fertilization, and C removal through biomass harvest or hydrological exports of dissolved organic and inorganic carbon, across wetlands of different status and land uses. We find that elevating water table substantially reduces net ecosystem C losses, with the annual NECB decreasing from 2579 (95% interval: 1976 to 3214) kg C ha year in drained wetlands to -422 (-658 to -176) kg C ha year in natural wetlands, and to -934 (-1532 to -399) kg C ha year in rewetted wetlands globally. Climate, land-use history, and time since water table changes introduce variabilities, with drainage for (sub)tropical agriculture or forestry uses showing high annual C losses, while the net C losses from drained wetlands can continue to affect soil C pools for several decades. Rewetting all types of drained wetlands is needed, particularly for those formerly agriculture-used (sub)tropical wetlands where net ecosystem C losses can be largely reduced. Our findings suggest that elevating water table is an important initiative to reduce C losses in degraded wetlands, which could contribute to policy decisions for managing wetlands to enhance their C sequestration.
排干的湿地被认为是碳（C）源热点，主张重新湿地化以恢复排干湿地的碳储存，以减缓气候变化。然而，当前对湿地碳平衡的评估主要集中在陆地与大气之间的垂直通量上，经常忽略了侧向碳通量和土地利用效应。在这里，我们对 893 个年度净生态系统碳平衡（NECB）测量值进行了全球综合分析，这些测量值包括 CO 的净生态系统交换，以及通过粪肥施肥的碳输入，以及通过生物质收获或溶解有机和无机碳的水文输出去除碳，涵盖了不同状态和土地利用方式的湿地。我们发现，抬高地下水位可大大减少净生态系统的碳损失，使年 NECB 从排干湿地的 2579（95%置信区间：1976 至 3214）kg C ha 年降至自然湿地的-422（-658 至-176）kg C ha 年，以及全球范围内重新湿地化的湿地的-934（-1532 至-399）kg C ha 年。气候、土地利用历史和地下水位变化的时间引入了变异性，热带或亚热带农业或林业用途的排水导致每年碳损失较高，而排干湿地的净碳损失仍可能在几十年内继续影响土壤碳库。需要重新湿地化所有类型的排干湿地，特别是那些曾经用于农业的（亚热带）湿地，在这些湿地中，净生态系统碳损失可以大大减少。我们的研究结果表明，抬高地下水位是减少退化湿地碳损失的重要举措，这有助于为管理湿地以增强其碳固存做出政策决策。
