潮汐作用和干湿交替对盐沼湿地碳交换的影响机制研究进展

潮汐盐沼湿地具有高的碳积累速率和低的CH_4排放量,是地球上最密集的碳汇之一。同时,气候变暖和海平面上升可能使得盐沼湿地更迅速的捕获和埋藏大气中的CO_2,因此盐沼湿地的"蓝碳"在减缓气候变化方面扮演着重要角色。潮汐盐沼湿地与其他湿地类型最大的区别和最显著的特征是在周期性潮汐作用下出现淹没和暴露,同时伴随盐分表聚与淋洗的干湿交替,可能是控制盐沼湿地碳交换过程和碳收支平衡的关键因素。但是,当前潮汐水动力过程及其周期性干湿交替对盐沼湿地碳交换关键过程和碳汇形成机制的影响尚不十分清楚。另外,以往相关研究通常孤立地考虑垂直方向上CO_2或CH_4交换或横向方向上的可溶性有机碳(DOC)、可溶性无机碳(DIC)、颗粒有机碳(POC)交换通量对盐沼湿地碳平衡进行评估,显然不够准确。因此,为了精确评估和预测盐沼湿地蓝碳的吸存能力,必须系统研究潮汐不同阶段对盐沼湿地碳交换过程的影响;深入分析潮汐作用下盐沼湿地碳交换的微生物机制;关注潮汐水动力作用对盐沼湿地DOC、DIC和POC产生、释放以及向邻近水体输出的影响;阐明潮汐作用对盐沼湿地碳汇形成机制的影响;纳入潮汐水动力过程作为变量,建立盐沼湿地碳循环模型。

Effect of tidal action and drying-wetting cycles on carbon exchange in a salt marsh: progress and prospects

Tidal salt marshes have a high carbon accumulation rate and low CH₄ emissions, representing some of the most dense carbon sinks in the world. In addition, salt marshes are likely to capture and bury atmospheric CO₂ more quickly in the future due to climate warming and sea level rise. Therefore, the "blue carbon" in tidal salt marshes plays an important role in the global carbon cycle and in the mitigation of climate change. Unlike other wetland types, a salt marsh is subjected to periodic flooding and exposure by tides, which leads to the alternation of salt accumulation and leaching. Therefore, tidal flooding and the drying and wetting cycles induced by tides in a salt marsh have a profound impact on the carbon biogeochemical cycle and carbon balance. However, it is still not clear how carbon exchange and carbon sequestration in a salt marsh respond to tidal hydrodynamic processes and the drying and wetting cycles. Moreover, previous studies have generally considered the vertical exchange of CO₂ or CH₄ or the transverse exchange of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and particulate organic carbon (POC) in isolation to evaluate the carbon budget of tidal salt marshes, which in turn limits the accurate assessment of the carbon sequestration process. Therefore, to accurately estimate and predict the sequestration capacity of blue carbon in salt marshes, it is important to (1) analyze the effects of different stages of the tide on the key processes of carbon exchange; (2) clarify the microbial mechanism of carbon exchange in a salt marsh under tidal action; (3) explore the tidal hydrodynamic influence on the production, release, and leaching of DOC, DIC, and POC from salt marshes to the adjacent coastal water; (4) clarify the influence of tidal action on the mechanisms of carbon sequestration in a salt marsh; and (5) incorporate the tidal hydrodynamic process into the empirical models of salt marshes to accurately evaluate their carbon budget.