Drs. Milne and Johnson will use the theory of phase transitions to study the origin, maintenance, and dynamics of broad-scale vegetation patterns in semiarid lands of New Mexico, USA. By definition, landscape phase transitions exhibit power-law behavior in the number of patches of woodland when the landscape changes from grassland to woodland. Two other characteristics, including the length of patches and the probability that a shrub resides in a continuous cluster of shrubs, also vary as powers of total woodland cover. Related power laws are predicted that describe the resilience of the system to disturbance. These studies will account for the effects of climatic teleconnection, elevation, slope aspect, soil texture, and land use. Models will be constructed to: (1) test that pinyon-juniper woodland ecotones exhibit characteristics of true phase transitions; (2) assess the equlibrium vs. nonequilibrium nature of ecotones. (3) investigate changes in vegetation patterns under possible climate change scenarios; and (4) use renormalization relations to express predictions of landscpae change at coarser levels of resolution. In summary, this project presents an approach for detecting ecological responses to environmental change. These investigators are leading scientists in the area of quantitative landscape ecology. Institutional facilities for conducting this research are outstanding.
