Leaf Survival Analysis In A Shading Experiment Using Cox Proportional Hazards Model

Abstract

An experiment was set up to study adaptability of agroforest seedling to different light regimes. Leaves supported by selected axes were censused during the 18 months course of experiment. Duku (Lansium domesticum), durian (Durio zibethinus), rubber (Hevea brassiliensis), and pulai (Alstonia scholaris) seedlings were grown under different shading intensity 0%, 55%, 75% and 88%. KaplanMeier estimate of leaf survival function shows that all four species show the same general trend; higher survival time for lower light level, and higher survival time for plagiotropic axis leaves as opposed to orthotropic. Cox proportional hazards model is used to model the hazard function of the four agroforest species. It is concluded that for the four species, shading treatments significantly effect leaf life span. In general the 88% shade treatment leading to maximum life span.