Biome Context and Lotic Ecosystem Rates
Tuesday, 15 December 2015
Poster Hall (Moscone South)
The stream biome gradient concept suggests that the biome in which a stream is embedded influences stream community structure and key ecosystem functions including primary production, community respiration, and nutrient uptake. We measured these key processes with whole-stream reach methods and smaller-scale incubations in numerous locations within stream networks across two years as part of a project on scaling ecosystem rates. Measurements were repeated across 7 biomes (tropical forest, tropical savanna, temperate deciduous forest, temperate rain forest, tallgrass prairie, boreal forest, and tundra). We found strong effects of light on primary production within and among biomes as a function of variable canopy among reaches and biomes. Community respiration and ammonium uptake were decoupled from light relative to gross primary production. Ammonium uptake rarely exhibited saturation with elevated concentrations, regardless of background concentrations or biome. We hypothesize that even though biomes exhibit major differences in gross primary production, the overall variation in community respiration and ammonium uptake is similar across biomes because respiration and uptake depend on carbon irrespective if it is derived from allochthonous or autochthonous inputs. Respiration and uptake are expected to vary depending upon factors not as tightly connected to the biome a stream is embedded in.