Linking plant disease risk and precipitation drivers: a dynamical systems framework.

Plant pathogens often respond sensitively to changes in their environmental conditions and consequently represent a potentially important ecological response to global change. Although several studies have considered the effects of increased temperature and CO(2) concentrations on plant pathogen risk, the effects of changing precipitation regimes have drawn less attention. Many classes of plant pathogen, however, are sensitive to changes in the water potential of their local environment. This study applied existing ecohydrological frameworks to connect precipitation, soil, and host properties with scenarios of pathogen risk, focusing on two water-sensitive pathogens: Phytophthora cinnamomi and Botryosphaeria doithidea. Simple models were developed to link the dynamics of these pathogens to water potentials. Model results demonstrated that the risk of host plants being colonized by the pathogens varied sensitively with soil and climate. The model was used to predict the distribution of Phytophthora in Western Australia and the severity of disease in horticultural blueberry trials with variable irrigation rates, illustrating potential applications of the framework. Extending the modeling framework to include spatial variation in hydrology, epidemic progression, and feedbacks between pathogens and soil moisture conditions may be needed to reproduce detailed spatial patterns of disease. At regional scales, the proposed modeling approach provides a tractable framework for coupling climatic drivers to ecosystem response while accounting for the probabilistic and variable nature of disease.