Seed germination and seedling performance of Pinus pinaster Ait. populations from Coastal Central Portugal

Abstract

Natural regeneration is crucial to maintaining local adaptative genetic pools of Pinus pinaster Ait. forests and their restoration following disturbance events. After a wildfire, weak-serotinous maritime pine populations may only depend on the viability of seeds exposed to fire to recover. Subsequently, summer drought during the early stages of the pine seedlings may seriously jeopardize the success of natural regeneration and the productivity of natural exploitable forests. The main objectives of this work were 1) to determine and compare the seed germination rates of weak-serotinous maritime pine populations along a geographic gradient within the Coastal Center of Portugal and 2) to investigate the ability of non-selected natural regenerated pine seedlings to survive under water limitation conditions. To accomplish those aims, seeds were collected from 8 populations distributed along a 100 km geographical gradient and left to germinate for 2 months. The seedlings were submitted to a water limitation experiment for 3 weeks. Overall no relation was found between seed weight and germination rate, but different trends were observed amongst populations. No relation was found between seed traits and seedling growth. Under water limitation, results suggested differences in water use efficiency between populations, possibly justified by adaptation to specific site conditions.