Predicting the severity of Cyclaneusma minus on Pinus radiata underTI Predicting the severity of Cyclaneusma minus on Pinus radiata under current climate in New Zealand

摘要

Despite being a damaging foliar disease of Pinus species, little research has characterized spatial variation in disease severity of Cyclaneusma needle cast at a macroscale. Using an extensive data set describing Cyclaneusma needle cast (S-sev) on plantation-grown Pinus radiata D. Don stands distributed widely across New Zealand, the objectives of this research were to (i) develop a regression model describing S-sev, (ii) use this model to identify key drivers of S-sev and their functional form and relative importance, and (iii) develop spatial predictions of S-sev for New Zealand P. radiata under current climate. Using an independent validation data set, the final model accounted for 73% of the variance in S-sev using four significant (P < 0.001) explanatory variables and an isotrophic exponential model to account for the spatial covariance in the data. S-sev was most sensitive to elevation followed by mean winter air temperature, mean relative humidity during July, and then stand age. S-sev increased to a maximum at mean winter air temperatures of between 7 and 9 degrees C before declining. Relationships between S-sev and all other variables were linear and positive. Spatial predictions of S-sev varied widely throughout New Zealand. Values of S-sev were highest in moderately warm, wet, and humid high-elevation environments located in the central North Island. In contrast, relatively low values of S-sev were predicted in drier eastern and southern regions of New Zealand.