National Research Program, U.S. Geological Survey, Reston, Virginia 20192, USA.
Am Nat. 2010 Sep;176(3):E66-79. doi: 10.1086/655215.
Mechanisms reported to promote landscape self-organization cannot explain vegetation patterning oriented parallel to flow. Recent catastrophic shifts in Everglades landscape pattern and ecological function highlight the need to understand the feedbacks governing these ecosystems. We modeled feedback between vegetation, hydrology, and sediment transport on the basis of a decade of experimentation. Results from more than 100 simulations showed that flows just sufficient to redistribute sediment from sparsely vegetated sloughs to dense ridges were needed for an equilibrium patterned landscape oriented parallel to flow. Surprisingly, although vegetation heterogeneity typically conveys resilience, in wetlands governed by flow/sediment feedbacks it indicates metastability, whereby the landscape is prone to catastrophic shifts. Substantial increases or decreases in flow relative to the equilibrium condition caused an expansion of emergent vegetation and loss of open-water areas that was unlikely to revert upon restoration of the equilibrium hydrology. Understanding these feedbacks is critical in forecasting wetland responses to changing conditions and designing management strategies that optimize ecosystem services, such as carbon sequestration or habitat provision. Our model and new sensitivity analysis techniques address these issues and make it newly apparent that simply returning flow to predrainage conditions in the Everglades may not be sufficient to restore historic landscape patterns and processes.
据报道，有一些机制可以促进景观的自组织，但这些机制无法解释与水流方向平行的植被模式。最近大沼泽地景观格局和生态功能发生了灾难性的转变，这凸显了人们需要了解控制这些生态系统的反馈机制。我们基于十年的实验，对植被、水文学和泥沙输移之间的反馈进行了建模。超过 100 次模拟的结果表明，仅需要足以将沉积物从植被稀疏的低地沼泽重新分配到密集的脊地的水流，就可以形成与水流平行的、具有特定图案的平衡景观。令人惊讶的是，尽管植被异质性通常具有恢复力，但在受水流/泥沙反馈控制的湿地中，它表明处于亚稳状态，即景观容易发生灾难性转变。与平衡条件相比，水流的大量增加或减少会导致挺水植被的扩张和开阔水域的减少，而在恢复平衡水文学条件后，这种情况不太可能恢复。理解这些反馈机制对于预测湿地对变化条件的响应以及设计优化生态系统服务（如碳固存或栖息地提供）的管理策略至关重要。我们的模型和新的敏感性分析技术解决了这些问题，并且清楚地表明，仅仅将大沼泽地的水流恢复到排水前的条件，可能不足以恢复历史景观模式和过程。
