Graphical Modeling of Ecological Time Series Data

Graphical models offer a powerful tool for studying ecosystem function. Changes in relationships among extrinsic and intrinsic biological and environmental variables can be explored. We discuss the application of graphical modeling to ecological data and illustrate this with an example case study. Ecological datasets are characteristically small with few data points, covering only a short period of time, and with high seasonal variation. This high variation, along with the fact that the data sets are small, can present problems for graphical modeling. Despite this, in general, considerable insight into ecosystem function can be gained from the use of graphical modeling. In our case study we modelled the ecosystem relationship between mice and food abundance. In New Zealand cyclical waves in the mice population size within beech forest roughly correspond to periods after a heavy beech tree seeding year. One explanation for this cycle is that years of heavy beech seeding causes an increase in mouse population. Understanding the ecosystem relationship will help understand possible causal links. In this study we used data collected by the Orongorongo valley near Wellington betwee