Stoichiometric Investigation of the Relationship

between Ecosystem Metabolism and the Plant Community

November 12, 2010

Rachel L. Douglass

Ecological Stoichiometry• Investigates the balance of multiple chemical

substances involved in ecological interactions and processes• Carbon-C• Nitrogen-N• Phosphorus-P

• Used to increase mechanistic understanding of:• Trophic interactions• Population dynamics

Research Objectives• 1) To characterize overall ecosystem metabolism and

individual species stoichiometry at varying timescales

• 2)To examine consequences of species stoichiometry, abundance, and distribution on overall ecosystem metabolism

• 3) To measure across time, seasons, flooding episodes and locations to quantify relationship between plant tissue stoichiometry and stoichiometry of ecosystem metabolism

H1: Individual taxa possess unique C:N:P stoichiometric signatures; yet these signatures exhibit daily, seasonal and episodic variation.

• Plants within the mixing zone at the 2500 site of the Santa Fe River exhibit temporal changes to their stoichiometry on episodic time intervals related to the stage of the river.

Hypotheses

Hypotheses H1: Individual taxa possess unique C:N:P

stoichiometric signatures; yet these signatures exhibit daily, seasonal and episodic variation.

H2: There will be a direct quantifiable relationship between ecosystem metabolism stoichiometry and the stoichiometry of the primary producers within the system with the ability to partition overall ecosystem metabolism by producer groups.

Hypotheses H1: Individual taxa possess unique C:N:P

stoichiometric signatures; yet these signatures exhibit daily, seasonal and episodic variation.

H2: There will be a direct quantifiable relationship between ecosystem metabolism stoichiometry and the stoichiometry of the primary producers within the system with the ability to partition overall ecosystem metabolism by producer groups.

H3: Changes in species abundance and distribution lead to changing ecosystem metabolic stoichiometry and alter nutrient cycling efficiency within the system.

Field MethodsYear 1• In-situ nutrient sensors• Monitor DO, NO3

- and SRP concentrations• Field collection of vascular plant and algal species• Collection on a seasonal basis• Used to analyze specimens for C:N and C:P ratios

Year 2 (in addition to all Year 1 activities)•Mesocosm experiments•Collection before, during and after flooding episodes

Anticipated Results and Contributions• Quantification of the relationship between ecosystem

metabolism and the plant community• Information on patterns including

• Changing abundance and distribution of plant species • Nutrient cycling efficiency changes

• Model of ecosystem metabolic changes

Comments, Suggestions,

and Questions?