Linking Heterotrophic Metabolism and Nutrient Uptake in Headwater Streams

Autotrophs and heterotrophs differ in their demand, acquisition and use of materials, but fundamentally nutrient demand is inherently linked to metabolism based on the stoichiometry of biochemical reactions. The differences between these two groups of organisms confound straightforward regression approaches to quantifying the relationship between nutrient demand and metabolism at an ecosystem level. We address how nutrient demand in headwater streams changes with shifts in organic matter supply and associated microbial activity by investigating these relationships in the predominantly heterotrophic conditions of a southern Appalachian stream. We measured litter input, organic matter standing crops, litter respiration rates and nitrate demand several times during the course of decomposition. There was a strong relationship between leaf standing crop and nitrate uptake efficiency across dates with maximal efficiency occurring when litter standing crops were highest. There was also an increase in nitrogen (N) uptake rate relative to respiration rates as breakdown progressed, which appears to be due to a shift in nutrient supply from the substrate to the water column associated with the depletion of labile, high quality organic matter in the substrate. It is our contention that streams establish a gradient of resource supply from particulate to dissolved sources that coincides with the movement of materials from terrestrial to marine systems.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Biology

Department dc:contributor.department

Biology

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

2007

Author dc:creator

• Gray, Travis Michael

Chair dc:contributor.committeechair

• Valett, H. Maurice

Committee members dc:contributor.committeemember

• Daniels, W. Lee
• Benfield, Ernest F.

• allochthonous organic matter
• ecosystem
• litter breakdown
• nitrate
• nutrient spiraling
• nutrient demand

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Dc Identifier Other

etd-08222007-152708

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/34703