Natural post-fire dynamics and serotiny in 10-year-old Pinus halepensis Mill. stands along a geographic gradient

Abstract

In 1994, six large fires occurred along a climate gradient in Eastern Spain. Ten-year-old trees were selected in the plots established for each location affected by fire. Each selected tree was measured for height and trunk diameter, the number of female strobili and cones, and grouped into four types. A geographical gradient was determined to study growth by latitude and variations in reproductive characteristics. Height and diameter values decreased southwards with the exception of the lowest-density tree location, where trunk diameters were similar to those in northern locations. Strobilus and cone production were higher in lower tree density locations owing to intraspecific competition and higher availability of water, nutrients and light. Serotiny levels were highest in southern locations, although lower percentages were found in the southern locations with low tree density. The number of reproductive trees was higher with lower tree density. The reproductive phase was reached in the lowest tree density site (also low site quality) and nearly reached in the most northern locations (high tree density as well as high site quality). Results showed a geographical gradient based on growth and reproduction dynamics, where serotiny levels are higher in southern locations. Density was shown to be a significant factor influencing overall pine stand development.