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首页> 外文期刊>Forest Ecology and Management >Threshold effects of flood duration on the vegetation and soils of the Upper Mississippi River floodplain, USA.
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Threshold effects of flood duration on the vegetation and soils of the Upper Mississippi River floodplain, USA.

机译：洪水持续时间对美国密西西比河上游漫滩的植被和土壤的阈值影响。

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摘要

Most large rivers have experienced major changes in hydrology and land use over the past century, with concomitant effects on sedimentation, nutrient cycling and biodiversity. To restore and/or enhance these ecosystems, managers need to know where their efforts are most likely to succeed under current hydrologic regimes as well as under potential future hydrologic regimes. We therefore examined changes in forest vegetation and soils across a hydrologic gradient, expressed as flood duration during the growing season, for 320 km of the Upper Mississippi River (UMR) floodplain. Soil texture was highly variable but trended toward finer grained sediments and >5% organic matter as flood duration increased from 0% to ~40% of the growing season. Beyond 40%, soil texture was exclusively silt plus clay with >5% organic matter. The diversity of both the understory and overstory tree communities was also highly variable at sites that flooded for <40% of the growing season. However, understory diversity decreased as flood duration increased from 0% to ~25% of the growing season and overstory diversity declined as flood duration increased from 0% to ~40% of the growing season. Diversity estimates for both strata were uniformly low at sites that flooded for longer than ~40% of the growing season. Beyond this point the proportional abundance of Acer saccharinum in the overstory exceeded 70%. Our results suggest that there is a threshold along the elevation gradient of this floodplain, corresponding with flood durations lasting ~40% of the growing season. At lower elevation sites, flooding exerts primary control over forest soils and vegetation, restricting the former to silt plus clay with higher organic matter and the latter to a few highly flood tolerant species. The existence of such thresholds have implications for management of floodplain soil nutrient dynamics and plant diversity under existing hydrologic regimes, more natural hydrologic regimes and more extreme hydrologic regimes that may result from climate change.
机译：在过去的一个世纪中，大多数大型河流的水文和土地利用都发生了重大变化，同时对沉积，养分循环和生物多样性产生了影响。为了恢复和/或增强这些生态系统，管理者需要知道在当前水文制度以及潜在的未来水文制度下其努力最有可能成功的地方。因此，我们检查了密西西比河上游（UMR）泛滥平原320公里处整个水文梯度中森林植被和土壤的变化，表示为生长期的洪水持续时间。土壤质地变化很大，但随着洪水持续时间从生长期的0％增加到〜40％，趋向于形成细颗粒状的沉积物和> 5％的有机物。超过40％的土壤质地仅为淤泥加粘土和有机物> 5％的土壤。在淹没生长季的40％的地点，林下树木和林上树木群落的多样性也高度不同。但是，随着洪水持续时间从生长期的0％增至〜25％，林下多样性降低;随着洪水持续时间从生长期的0％增至〜40％，林下多样性降低。在淹没时间超过生长期的40％的地点，两个地层的多样性估计均较低。超过这一点，在楼上的糖精的比例丰度超过70％。我们的结果表明，该洪泛区的海拔梯度上有一个阈值，对应于持续约40％生长季节的洪水持续时间。在海拔较低的地区，洪水主要控制森林土壤和植被，将前者限制为淤泥和有机质含量较高的粘土，而后者则限制为少数几个高度耐洪的物种。在现有水文制度，更多自然水文制度和气候变化可能导致的更多极端水文制度下，这些阈值的存在对洪泛区土壤养分动态和植物多样性的管理具有影响。

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