Pacific Southwest

Title: Modeling risk for SOD nationwide: what are the effects of model choice on risk prediction?

Author: Kelly, M.; Shaari, D.; Guo, Q.; Liu, D.

Date: 2006

Source: In: Frankel, Susan J.; Shea, Patrick J.; and Haverty, Michael I., tech. coords. Proceedings of the sudden oak death second science symposium: the state of our knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 333-344

Station ID: GTR-PSW-196

Description: Phytophthora ramorum has the potential to infect many forest types found throughout the United States. Efforts to model the potential habitat for P. ramorum and sudden oak death (SOD) are important for disease regulation and management. Yet, spatial models using identical data can have differing results. In this paper we examine the results from five types of models generated from common input parameters, and investigate model agreement for distribution of risk for P. ramorum. We examine five models: (1) Rule-based, (2) Logistic regression, (3) Classification and Regression Trees, (4) Genetic Algorithm modeling, and (5) Support Vector Machines. The models differed in terms of parametric and non-parametric requirements, necessity for presence/absence data, and whether or not the explanatory variables were determined a priori or revealed during the model process. Nationwide input data included vegetation/host (hardwood diversity and hardwood density), topography, and climate (e.g. precipitation, frost days, temperature, and many other layers). We developed a risk map for the conterminous United States in which probabilities for P. ramorum disease establishment were based not on one model, but on agreement between multiple models. The five models were consistent in their prediction of some SOD risk in coastal CA, OR and WA. All models predicted some risk in the northern foothills of the Sierra Nevada mountains in CA. Outside of the west coast, the combined models predicted highest risk for SOD in a east-west oriented band including eastern OK, central AR, TN, KY, northern MI, AL, GA and SC, parts of central NC, and eastern VA, DL and MD. The paper also discusses issues of input data accuracy, coverage, availability of nationwide host datasets, data scale, and model computational requirements. Although theoretical in nature, the results of this paper have practical and applied value for managers and regulators of this disease.

Keywords: geographic information systems, spatial modeling, sudden oak death

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Citation

Kelly, M.; Shaari, D.; Guo, Q.; Liu, D.  2006.  Modeling risk for SOD nationwide: what are the effects of model choice on risk prediction?.   In: Frankel, Susan J.; Shea, Patrick J.; and Haverty, Michael I., tech. coords. Proceedings of the sudden oak death second science symposium: the state of our knowledge. Gen. Tech. Rep. PSW-GTR-196. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture: 333-344.