PNAS:草沼对海平面上升的恢复力

摘要 : 美国杜克大学Nicholas环境学院与Pratt工程学院一项研究发现，二氧化碳施肥效应可能增加沿海草沼的土壤堆积和沼泽对海平面上升的恢复力。

美国杜克大学Nicholas环境学院与Pratt工程学院一项研究发现，二氧化碳施肥效应可能增加沿海草沼的土壤堆积和沼泽对海平面上升的恢复力。海平面上升让沿海草沼濒临危险，但是草沼淹没率取决于无机沉积物沉积率和有机土壤形成率，人们对在二氧化碳增加和气候变化的情境下这些过程的变化的了解甚少。Marco Marani及其同事构建了一个草沼植被与形态的模型，它纳入了关于草沼植被对大气二氧化碳增加的响应的已发表的观测数据。这组作者发现，通过增加植物生产力，二氧化碳施肥可能通过增加地面以上的土壤堆积和地下有机土壤的生成从而增加草沼对海平面加速上升的恢复力。这组作者说，地下生产力的增加让有机土壤的生成加速，而地面以上的生产力的增加促进了悬浮的无机沉积物的捕获。在一些情况下，建模的草沼生产力增加让可能导致草沼淹没至多60%的海平面上升的极限值增加。此外，这组作者发现，二氧化碳对草沼的施肥效应表现出了高的空间变异，这提示对单点响应的研究可能对于阐明某些草沼过程有用，但是可能无法捕捉到草沼对气候变化的全尺度的响应。这些结果提示，草沼生态系统对海平面上升的恢复力可能比此前认为的更高。

原文链接：

Spatial response of coastal marshes to increased atmospheric CO2

原文摘要：

The elevation and extent of coastal marshes are dictated by the interplay between the rate of relative sea-level rise (RRSLR), surface accretion by inorganic sediment deposition, and organic soil production by plants. These accretion processes respond to changes in local and global forcings, such as sediment delivery to the coast, nutrient concentrations, and atmospheric CO2, but their relative importance for marsh resilience to increasing RRSLR remains unclear. In particular, marshes up-take atmospheric CO2 at high rates, thereby playing a major role in the global carbon cycle, but the morphologic expression of increasing atmospheric CO2 concentration, an imminent aspect of climate change, has not yet been isolated and quantified. Using the available observational literature and a spatially explicit ecomorphodynamic model, we explore marsh responses to increased atmospheric CO2, relative to changes in inorganic sediment availability and elevated nitrogen levels. We find that marsh vegetation response to foreseen elevated atmospheric CO2 is similar in magnitude to the response induced by a varying inorganic sediment concentration, and that it increases the threshold RRSLR initiating marsh submergence by up to 60% in the range of forcings explored. Furthermore, we find that marsh responses are inherently spatially dependent, and cannot be adequately captured through 0-dimensional representations of marsh dynamics. Our results imply that coastal marshes, and the major carbon sink they represent, are significantly more resilient to foreseen climatic changes than previously thought.

doi: 10.1073/PNAS.1516286112

作者：Katherine M. Ratliff

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