Ecosystems state space

Johnson, A.R. 1988a. Evaluating ecosystem response to toxicant stress a state space approach. In Aquatic Toxicology and Hazard Assessment, Vol. 10, ASTM STP 971. W.J. Adams, G.A. Chapman, and W.G. Landis, Eds. American Society for Testing and Materials, Philadelphia, PA, pp. 275-285. 

This work required a large amount of subsidiary R D in (1) hydrodynamic sediment-plant mesocosm design, replication, and monitoring, (2) synthetic and analytical chemistry, including the synthesis of commercially unavailable standards and development analytical approaches to detect minor differences in organic chemicals between time points and treatments and (3) sensor design, time series data acquisition and wavelet analysis of non-stationary series [6], and covariance structure modeling of mesocosm and ecosystem data [1]. Basic questions (e.g., what constitutes a true spatiotemporal replicate in a multivariate, multiply colinear system What is the minimum number of indicator variables needed to characterize the states of such a system and how often do they need to be sampled in space and time ) arose and had to... 

The results can be displayed by a plot of [Y] as a function of [X], A mathematical space with time-dependent variables plotted on the axis is called a phase space. If [Y] is plotted as a function of [X] for a constant value of [A], there a closed curve that is retraced over and over again as time passes, exhibiting periodic behavior. However, there are different curves for different initial states, but the oscillations predicted by the mechanism resemble the actual fluctuations in predator and prey populations in actual ecosystems. 

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