A two-step mortality model for even-aged stands of Pinus radiata D. Don in Galicia (Northwestern Spain)

Abstract

A two-step mortality model for even-aged Pinus radiata stands in Galicia (Northwestern Spain) is presented. The model was developed using data from two inventories of a trial network involving 130 permanent plots. The model consists of two complementary equations. The first equation is a logistic function predicting the probability of complete survival depending on stems per hectare, age and relative spacing index. The second equation estimates the reduction in the number of stems that is observed in a stand where natural mortality occurs. Fourteen equations were fitted utilising the plots where trees died over the time period analyzed. Estimates from this second model are then reduced using three different stem number projection methods: a stochastic approach, a deterministic rule-based method and another deterministic approach that compares the probability of mortality using a threshold value. The values and signs of the parameters in both equations are consistent with existing experience about natural mortality of Pinus radiata in the region of Galicia.