Effects of post-fire silviculture practices on Pachyrhinus squamosus defoliation levels and growth of Pinus halepensis Mill.

Abstract

Pinus halepensis Mill. (Aleppo pine) forms dense and extensive stands after frequent fires in SE Spain. Due to the high densities reached by this species after fire, thinning is necessary. Two great fires occurred in SE Spain in August 1994 and natural regeneration stands of P. halepensis were managed in 1999 using several silvicultural treatments (thinning, pruning and scrubbing). The objective was to improve the stands quality and accelerate pine canopy growth. However, since a few years, damages produced by several defoliator species from Pachyrhinus genus (Coleoptera, Curculionidae) have been detected in young treated P. halepensis stands in Spain. To test the intensity of the P. squamosus attack, two post-fire localities submitted to different treatments were selected (Yeste and Calasparra, in SE Spain) corresponding to different climate conditions (dry and semiarid, respectively). Results showed that the most intense defoliation level was recorded in Yeste. Beetles preferentially ate needles from the previous growing season in both localities. Significant differences for defoliation percentage depending on silvicultural treatments were also recorded. Nutritional state of the needles for nitrogen, phosphorus and potassium was similar in both localities showing some relationship with silvicultural treatments. In general, the more intense the silvicultural treatment, the higher defoliation percentage was recorded. Growth pattern was similar in both study sites, reaching bring higher where treatments were more intense. Reduced needle and shoot growth was registered in Calasparra relative to Yeste.