Abstract ID: 632

Revealing hidden terra firme rainforest environments in Amazonia

The great spatial complexity of tropical rainforests in Amazonia has so far thwarted efforts to describe landscape and vegetation in a systematic and quantitative manner. Using the height above the nearest drainage terrain descriptor (HAND algorithm developed by our group) on SRTM DEM topographic data for terra firme areas, we were able to determine that the physical principle of relative soil water draining potential has a dominant role in controlling landscape processes and vegetation and is a robust predictor for the occurrence of soil water condition. The class-slicing HAND was run for a rectangular 18000 km2 area of terra firme forest to the West of Manaus. The terra firme terrain was quantitatively partitioned into four environment classes: largely waterlogged valley floors, with a water table typically at the surface or close to (25.6%), valley floor areas with shallow water tables (32.9%), slopes (11.1%) and plateaus (30.4%), both with deeper water tables. Overall, the lowlands with near surface or shallow water tables occupied 58.5% of the area, and the uplands with deeper water tables, still widely held as dominant environments, occupied only 41.5% of the area. Terra firme in Central Amazonia has extensive lowland swampy environments. Rainforest vegetation is very sensitive to soil water conditions, and as a result, complex spatial arrangements of heterogeneous communities occur. So far, large scale integrative studies in Amazonia, such as the estimation of basin-wide carbon budgets, have failed to take these limiting local environments into account. The accurate and quantitative capacity of the HAND descriptor to map terrain using only digital topography opens the way for the development of a comprehensive logical system to classify terrain. The classification of terrain can be especially useful for biodiversity studies and for the budgeting of stocks and fluxes of carbon, water and nutrients.

Session:  Feedbacks to Climate - Land cover, surface hydrology, and atmospheric feedbacks. (A)

Presentation Type:  Oral