Data from: Drivers of landscape evolution: multiple regimes and their influence on carbon sequestration in a sub-tropical peatland

Typically, restoration goals target a point in history, i.e., pre-human influence state, however, ecosystems are dynamic and restoration goals must consider the potential evolution of the system, along with primary causes of landscape degradation and the resultant resilience. Using the Everglades as a case study, known disturbances were linked to biogeochemical and vegetation patterns to compare the divergence of the anthropogenically impacted landscape from that expected during natural peatland evolution. Specifically, landscape soil biogeochemistry of ~ 1100 sites was examined in context of hydroperiod, spatial and temporal trends in water quality from the 1940′s through present, elevation, and vegetation communities. This provided a link between carbon (C) accumulation and the influence of anthropogenic alterations. The network of canals created to manage water resulted in a greater ratio of surface water to rainfall contribution to the water budget, restored connectivity of groundwater to surface water, and facilitated overdrainage and mineral and nutrient enrichment of the ecosystem, causing multiple regime shifts and evidence of C loss. This study suggests that restoration can promote the accumulation of minerotrophic peats, but it is difficult to recreate the trajectory towards the ombrotrophic peatland, one of the end members and most C rich portions of the ecosystem, given changes in source waters and connectivity. In addition, a comparison with the literature and paleoecological data confirmed that while phosphorus (P) and C accumulation are positively related, even relatively small increases in P content reduced the proportional C content of peat soils. Overall, this study highlights the need to consider the potential natural trajectories of landscape development, the multiple coexisting resultant regimes, and the importance of soil biogeochemical properties when establishing and prioritizing restoration goals. Given the resilience and feedback loops of the anthropogenically impacted areas, active management of these areas may be necessary if we are to restore the vegetation community composition and biogeochemical characteristics to those of natural regimes, however, some legacy effects will constrain future restoration efforts.

通常而言，生态修复目标多以历史特定节点为参照基准，例如人类活动影响前的原生生态状态。但生态系统本身处于动态演化之中，因此制定修复目标时，不仅需要考量系统的潜在演替过程，还需结合景观退化的核心诱因及其引发的生态弹性。本研究以大沼泽地（Everglades）为案例对象，将已识别的干扰因子与生物地球化学及植被格局进行关联分析，以此对比受人类活动干扰的景观与天然泥炭地自然演替下的预期状态之间的差异。具体而言，研究针对约1100个样点的景观土壤生物地球化学特征展开分析，同时结合水文周期、1940年代至今水质的时空变化趋势、海拔梯度以及植被群落特征进行综合考量，由此构建了碳（C）累积与人类活动改造影响之间的关联机制。为调控水资源而修建的运河网络，使得地表水在区域水量平衡中的占比相较于降雨补给更高；同时修复了地下水与地表水的天然连通性，却也加剧了生态系统的过度排水以及矿质与养分富集现象，进而引发了多重生态系统状态转变，并伴随碳流失的相关证据。本研究表明，生态修复可促进矿养泥炭（minerotrophic peat）的累积，但鉴于水源补给与水文连通性的改变，难以复刻向寡养泥炭地（ombrotrophic peatland）演替的轨迹——而寡养泥炭地正是该生态系统的核心终态类型之一，同时也是碳储量最高的区域。此外，通过与已有文献及古生态数据的对比验证，研究发现尽管磷（P）累积与碳累积呈正相关关系，但泥炭土壤中磷含量的小幅提升即可降低其碳占比。综上，本研究强调，在制定并排序修复目标优先级时，需充分考量景观自然演替的潜在轨迹、多重共存的生态系统状态，以及土壤生物地球化学特征的重要性。鉴于受人类活动影响区域的生态弹性与反馈环路特征，若要将植被群落组成与生物地球化学特征恢复至天然状态，需对这些区域实施主动管理；但部分遗留效应仍会制约未来的修复工作。