Seed provenance and fire-related reproductive traits of Pinus pinaster in central Spain

Abstract

Disregarded for centuries, Mediterranean pine forests in Spain have been severely affected by human activities including fires and livestock grazing. As a consequence, reforestation programs were started by the late 1800s, albeit the origin of the seeds was not considered until the late 1960s. In July 2005, a large Pinus pinaster Ait. forest, located in Guadalajara (central Spain), burned down. In this area, we studied fire-related fitness traits in natural stands (zone N) and compared them to those of trees sown with seeds from foreign sources (zone S). Cone production per hectare in zone N doubled that found in zone S. In addition, zone N resulted in more saplings per hectare as well as more small trees bearing cones than zone S. In zone S, trees showed thicker crowns and less fructification resulting in open formations with low intraspecific competition. Whereas in the natural stands the average percentage of serotiny per tree was 32%, in the sown stands only one serotinous cone was found in seven unburned harvested trees. Compared with zone S, the presence of seedlings after springtime was almost nine times higher in zone N in spite of the damaging effects of logging and removal of burnt wood.