research project details
Project Title: Constructing Probability Surfaces of Ecological Changes in Coastal
Aquatic Systems Through Retrospective Analysis of Phragmites Australis Invasion and Expansion
Investigator(s): Denice
Wardrop, Mary
Easterling, and G.P. Patil
Sponsor: Environmental
Protection Agency
Objectives:
- Choose an aquatic ecosystem with clearly identified alternative states, and define a limited number of variables that are considered to be the driving factors in state changes;
- Establish the database of explanatory and response variables over both a spatial and temporal extent;
- Construct a probability surface of state changes over the n-dimensional space of selected explanatory variables;
- Describe thresholds in terms of the probability surface; and
- (5) Test the threshold surface with data from a second location.
Approach:
The identification of thresholds assumes two steps: identification of primary or explanatory variables controlling the transition between alternative stable states, and the identification of the band of conditions for which there is a high probability of a state change (i.e., thresholds). This project develops a conceptual model of Phragmites invasion and spread, and then constructs a probability surface that relates the set of explanatory variables to the shift in stable states. Any set of conditions (i.e., explanatory variables) can then be placed upon the probability surface, illuminating the proximity of threshold conditions and how “close” any given marsh is to a transtition to an alternative state.
Expected Results:
We will develop a unique analytical method, which involves constructing a probability surface, which can be used to identify thresholds for the transition of coastal marshes to dominance by Phragmites. Any set of conditions can then be placed on the probability surface, allowing the statistical model to be used in a predictive fashion. The method could be applied to a wie variety of aquatic ecosystems for which state changes occur over either a spatial and temporal extent, or both.