Modeling impacts of drought‐induced salinity intrusion on carbon dynamics in tidal freshwater forested wetlands
Modeling impacts of drought‐induced salinity intrusion on carbon dynamics in tidal freshwater forested wetlands
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模拟干旱引起的盐分入侵对潮汐淡水森林湿地碳动态的影响
DOI：
10.1002/eap.2700
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发表时间：
2022
影响因子：
5
通讯作者：
Ward, Eric J.
中科院分区：
文献类型：
--
作者：
Wang, Hongqing;Dai, Zhaohua;Trettin, Carl C.;Krauss, Ken W.;Noe, Gregory B.;Burton, Andrew J.;Stagg, Camille L.;Ward, Eric J.
潮汐淡水森林湿地（TFFW）提供了重要的生态系统服务，包括各种野生动物物种的重要栖息地和大气二氧化碳的重要碳汇。然而，在气候变化对一系列TFFW的碳通量和储量的大小和变异性的影响方面，仍然存在很大的不确定性。在这项研究中，我们建立了一个过程驱动的潮汐淡水湿地反硝化分解模型（TFW - DNDC），该模型集成了土壤盐度对植物生产力和土壤有机质分解的影响等新特征，以探索干旱诱导的盐水入侵在TFFW中的碳动态。Waccamaw河（美国）和萨凡纳河（美国）泛滥平原沿线的8个地点被选中，代表TFFW从健康到中度和高度盐影响森林，最终到低盐沼泽的转变。TFW - DNDC通过野外观测的年凋落物、茎生长、根系生长、土壤异养呼吸和土壤有机碳储量进行校准和验证。分析表明，由于干旱导致土壤孔隙水盐度升高和地下水位降低，TFFW的植物生产力和土壤固碳量可能发生实质性变化，但以依赖于模拟河流的交互方式发生变化。由于碳循环过程和环境驱动因素之间的非线性关系，这些响应是可变的。与正常条件相比，干旱条件下高度受盐影响的森林立地的植物生产力、植物呼吸、土壤有机碳固存率和储量显著下降。考虑到在未来气候变化和海平面上升的影响下，健康和中等盐影响的森林很有可能成为高度盐影响的森林，如果没有上坡迁移，TFFW很可能会失去其作为碳汇的能力。
Tidal freshwater forested wetlands (TFFW) provide critical ecosystem services including an essential habitat for a variety of wildlife species and significant carbon sinks for atmospheric carbon dioxide. However, large uncertainties remain concerning the impacts of climate change on the magnitude and variability of carbon fluxes and storage across a range of TFFW. In this study, we developed a process‐driven Tidal Freshwater Wetlands DeNitrification‐DeComposition model (TFW‐DNDC) that has integrated new features, such as soil salinity effects on plant productivity and soil organic matter decomposition to explore carbon dynamics in the TFFW in response to drought‐induced saltwater intrusion. Eight sites along the floodplains of the Waccamaw River (USA) and the Savannah River (USA) were selected to represent the TFFW transition from healthy to moderately and highly salt‐impacted forests, and eventually to oligohaline marshes. The TFW‐DNDC was calibrated and validated using field observed annual litterfall, stem growth, root growth, soil heterotrophic respiration, and soil organic carbon storage. Analyses indicate that plant productivity and soil carbon sequestration in TFFW could change substantially in response to increased soil pore water salinity and reduced soil water table due to drought, but in interactive ways dependent on the river simulated. These responses are variable due to nonlinear relationships between carbon cycling processes and environmental drivers. Plant productivity, plant respiration, soil organic carbon sequestration rate, and storage in the highly salt‐impacted forest sites decreased significantly under drought conditions compared with normal conditions. Considering the high likelihood of healthy and moderately salt‐impacted forests becoming highly salt‐impacted forests under future climate change and sea‐level rise, it is very likely that the TFFW will lose their capacity as carbon sinks without up‐slope migration.