The ability of wetlands to accrete organic matter in response to rising sea level is a key to landscape resilience, especially in light of reduced sediment availability consequent to dam construction and channelization. This study examined the degradation of cattail (Typha spp.) and tule (Schoenoplectus acutus) litters in restored wetlands through the lens of lignin, a major structural biopolymer in vascular plants with degradation characteristics very sensitive to oxic versus anoxic conditions. A series of litterbags were deployed during the first 10 years after flooding of Deep (55 cm) and Shallow (25 cm) restored wetlands. As emergent marsh vegetation spread through the maturing wetlands, anoxic conditions were more prevalent and overall degradation rates of litter in litterbags were lower. In later experiments in the maturing wetlands, lignin was progressively enriched in litter as evidenced by carbon-normalized yields (Λ8) that increased in tule starting materials from 6.3 to 7.1 mg 100 mgOC–1 to as high as 9.9 mg 100 mgOC–1, and in cattail starting materials from 5.9 to 7.0 mg 100 mgOC–1 to as high as 10.9 mg 100 mgOC–1. However, in an experiment initiated soon after the restored wetlands were constructed, Λ8 in tule litter decreased from 6.8 to 3.6 mg 100 mgOC–1, highlighting the prevalence of initial oxic conditions. With the exception of the early oxic conditions for tule, there was an overall trend of decreasing lignin acid-to-aldehyde ratios with litter degradation, which runs counter to most studies in the literature. We hypothesize that this reflects the utilization of more oxygen-rich lignin components as electron acceptors in redox reactions. No consistent differences were observed in degradation patterns between the Shallow and Deep wetlands. There were distinct differences in lignin degradation in cattail (more resistant) versus tule (less resistant), which indicates that although anoxia may be the dominant control on organic matter accretion in wetlands, specific types of vegetation in restored or constructed wetlands affects organic matter preservation, and hence accretion. Thus, selective management of predominant species in wetlands may prove important for the ability of wetlands to maintain emergent vegetation during sea level rise and to preserve the overall stability of wetland soils.

中文翻译：

---

植被与缺氧控制对恢复湿地植物凋落物降解的影响

湿地在海平面上升时吸积有机物的能力是景观恢复力的关键，特别是考虑到大坝建设和渠道化导致沉积物可用性减少。本研究通过木质素镜头检查了恢复湿地中香蒲 (Typha spp.) 和香蒲 (Schoenoplectus acutus) 凋落物的降解情况，木质素是维管植物中的一种主要结构生物聚合物，其降解特性对有氧和缺氧条件非常敏感。在深（55 厘米）和浅（25 厘米）恢复的湿地被洪水淹没后的前 10 年里，部署了一系列垃圾袋。随着新出现的沼泽植被通过成熟的湿地蔓延，缺氧条件更为普遍，垃圾袋中的垃圾总体降解率较低。在后来的成熟湿地实验中，木质素在凋落物中逐渐富集，如碳归一化产量 (Λ8) 所证明的那样，在 tule 起始材料中从 6.3 到 7.1 mg 100 mgOC-1 增加到高达 9.9 mg 100 mgOC-1，在香蒲起始材料中从 5.9 7.0 mg 100 mgOC-1 至 10.9 mg 100 mgOC-1。然而，在恢复湿地建成后不久开始的一项实验中，tule 凋落物中的 Λ8 从 6.8 降至 3.6 mg 100 mgOC–1，突出了初始含氧条件的普遍性。除了 tule 的早期好氧条件外，随着凋落物降解，木质素酸与醛的比率总体呈下降趋势，这与文献中的大多数研究背道而驰。我们假设这反映了在氧化还原反应中使用更多富氧木质素成分作为电子受体。浅层湿地和深层湿地之间的退化模式没有观察到一致的差异。香蒲（抗性较强）与香蒲（抗性较差）的木质素降解存在明显差异，这表明虽然缺氧可能是湿地有机质增加的主要控制因素，但恢复或人工湿地中特定类型的植被影响有机质保存，因此吸积。因此，对湿地中优势物种的选择性管理可能被证明对于湿地在海平面上升期间保持新兴植被的能力和保持湿地土壤的整体稳定性很重要。这表明虽然缺氧可能是湿地有机质增加的主要控制因素，但恢复或人工湿地中特定类型的植被会影响有机质的保存，从而影响有机质的增加。因此，对湿地中优势物种的选择性管理可能被证明对于湿地在海平面上升期间保持新兴植被的能力和保持湿地土壤的整体稳定性很重要。这表明虽然缺氧可能是湿地有机质增加的主要控制因素，但恢复或人工湿地中特定类型的植被会影响有机质的保存，从而影响有机质的增加。因此，对湿地中优势物种的选择性管理可能被证明对于湿地在海平面上升期间保持新兴植被的能力和保持湿地土壤的整体稳定性很重要。