Survival of Pinus pseudostrobus Lindl. plantations in terms of the production system and pre-conditioning in the nursery

Abstract

The survival of a Pinus pseudostrobus plantation was assessed as a result of the effect of the production system and pre-conditioning of the plants in the nursery; in addition, the mortality risk was analyzed in terms of its morphological quality. Plants produced under three systems were utilized: 1) one year on a polystyrene tray [1+0], 2) two years in a polyethylene bag [0+2], and 3) one year on a polystyrene tray plus one year in a polyethylene bag [1+1]. Previous to the plantation, during 45 days, the plants were subjected to pre-conditioning through modification of the watering regime; three different levels were applied: 1) low level, daily watering in the morning; 2) moderate level, watering until saturation every 9 days, and 3) high level, watering until saturation every 15 days. Two site conditions were selected in field: 1) 10 % slope with NE exposure and 55 % slope with SW exposure. The survival analysis was performed using the Kaplan-Meier method, and a proportional hazard regression was carried out in order to determine the mortality risk. 14 months after establishment, an average survival rate of 52.9 % was obtained, with a higher mortality during the first three months. Significant differences were found between production systems and between plantation sites, but not between pre-conditioning levels, although this generated different responses for each production system; a higher survival rate was reported among plants cultivated with the 0+2 system and subjected to a high pre-conditioning level. The diameter was the morphological variable most closely related to mortality risk in the plantation sites.