Ecological Impacts of an Extreme Flood: Implications for Changing Disturbance Regimes

Abstract

A common theme in climate change projections is that extreme flood events are likely to increase in frequency. This means that the ecohydrological impacts of floods on riparian vegetation are likely to shift in the future. We use the example of a large flood (>500 yr recurrence interval) in the North Fork River watershed in the Missouri Ozarks to assess the ecological impact of an extreme flood, recognizing that such events may become more common in the future. We sampled 514 living and dead trees within 38 quadrats across the valley bottoms of five tributaries. We found that over a quarter of trees >5 cm DBH were killed by the flood, with the greatest impact (>50% mortality) on depositional bars, but with notable mortality extending to terraces and even the valley walls. Small mature trees, lacking both the flexibility of saplings and the strength of larger trees, experienced high mortality, with those 15-20 cm DBH having the highest rate at 44.4%. Differential mortality among species altered the forest composition, with mature stems of blackgum, hornbeam, red cedar, river birch and shortleaf pine all losing more than 30%, while other common species like white ash and black walnut had no losses. Overall, this extreme event had a significant impact on the density and composition of the riparian forest, even on landforms typically unaffected by floods. This example suggests that as once-rare high-magnitude floods become more common, the composition and structure of temperate riparian forests are likely to change in response.

Department(s)

Geography, Geology, and Planning

Document Type

Conference Proceeding

Keywords

biogeochemical cycles, processes and modeling, biosphere/atmosphere interactionscarbon cycling, ecosystems

Publication Date

12-1-2019

Journal Title

2019 Fall Meeting of the American Geophysical Union

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