Shoot growth and phenology modelling of grafted Stone pine (Pinus pinea L.) in Inner Spain

Abstract

Shoot elongation, flowering phenology, branch thickening, needle and cone growth was monitored during four years in grafted stone pines in Inner Spain. The relevance of environmental influence on growth and flower regulation in Mediterranean stone pine as nut crop is stressed. Different models of thermal time compute were compared for characterizing phenostage onset, shoot and cone growth response to temperature. Non-linear regression models for relative length of preformed shoots and relative cone diameter were fitted in thermal-time scale. Shoot-growth timing was characterized by a common degree-day sum between years. Correlation of June rainfall with shoot length and flower bearing in the next year and with current needle and branch diameter growth was highly significant. Also, summer shoots and a second female flowering occurred occasionally in leader branches in dependence on June rainfall, but cone-setting failed due to the absence of pollen. Phenological model of the variation between years were consistent with observations in mature non-grafted stone pines.