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Spatial and Temporal Patterns of Aquatic Biogeography in the Amazon

Erica Akiko Howard, SAGE, University of Wisconsin - Madison, eahoward@wisc.edu (Presenting)
Michael T. Coe, Woods Hole Research Center, mtcoe@whrc.org
Jonathan A. Foley, SAGE, University of Wisconsin - Madison, jfoley@wisc.edu
Marcos Heil Costa, The Federal University of Višosa, mhcosta@ufv.br

We combined a hydrological model (Terrestrial Hydrology Model with Biogeochemistry, THMB), remote sensing observations, and empirical data to identify the distribution of aquatic and wetland biogeographic types throughout the central Amazon basin. We calibrated monthly simulation results with remotely sensed observations of flooded area and extent of different wetland categories for high and low water periods over a 1.7 million km2 region of the central Amazon. Two additional dimensions of floodplain biogeography (river size and color) were added to provide insight into the geographic distribution of key ecosystem types and their flooding seasonality. Although the edaphic characteristics that control river color (e.g., black vs. white) are well known, the distribution of these types across the landscape has not been mapped, largely because of a lack of fine-scale maps of soil heterogeneity. We present a first attempt to categorize river color type based on existing maps of soils and geologic provinces and on river connectivity to upstream sediment sources. Model results reproduced regional differences in seasonal flood extent and timing north and south of the Amazon mainstem, reflecting the dominant climatic regimes. Black-water streams and medium-sized rivers, followed by large white-water rivers, were the most extensive types across the study region. However much of the black water was in areas likely to be influenced by white-water rivers while flooded. The monthly extent of flooded areas dominated by woody vegetation was consistently more strongly seasonal than non-woody areas. Also, the extent of flooding in muddy and semi-muddy rivers and floodplains tended to be more highly seasonal than in black- and clear-water areas. Regional flooding variability has disproportionate effects on different ecosystem types, suggesting that persistent, long-term changes to flooding regimes may have long-lasting consequences for floodplain vegetation, wildlife, and human residents.

Science Theme:  LC (Land Use and Land Cover Change)

Session:  3A: Carbon, Rivers, and Wetlands

Presentation Type:  Oral

Abstract ID: 105

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