Predicting pine mortality
News from Forest Research: February 2008
Pine Wilt Disease, caused by the pinewood nematode (PWN), kills huge numbers of pine trees every year in Japan, Korea and China. Forest Research and its European partners have now developed a new process-based model to simulate the relative risks of the disease throughout Europe.
PWN was first found in Portugal in 1999 and has slowly spread through the Setúbal region near Lisbon. The disease has a high mortality rate for pine species in Europe (e.g. Pinus pinaster and P. sylvestris), so it is essential to assess the potential risk in different areas in order to plan effective preventative measures.
In 2003 an EU-funded PHRAME project was launched to understand the disease and develop an improved pest risk analysis model to assess its impact. Although there is data on the disease from East Asia, the differences in climate conditions and tree species mean a process-based model was needed to evaluate its potential risk in Europe. The model simulates hydrology processes (e.g. rainfall interception, soil water movement, runoff, soil and canopy evaporation, and photosynthesis-coupled transpiration) for a forest stand of known structure, soil and climate. It simulates the process of tree wilting and has been used to evaluate risk from the disease in Portugal (Estacao Florestal Nacional) and Sweden (Plant Protection Service).
The maps below show predicted pine mortality to be low in Sweden, relatively high in Portugal, and higher still in Japan. The simulation showed similar results to observed field mortality data, giving confidence in the new model.
However, the current model only evaluates the mortality of a host tree, so while it can simulate the likelihood of a tree wilting in a specific location, it cannot evaluate the spread of the disease, nor the possibility of the pinewood nematode becoming established in the first place. Forest Research researchers are now working with Portuguese researchers to develop a vector-pathogen-plant model with which to address these two factors.