Drought effect over the distribution and density of Dendroctonus mexicanus Hopkins, 1905 in temperate forest

Abstract

The temperate forests of Nuevo León are susceptible to the attack of Dendroctonus bark beetles, which are considered the most destructive insects in Mexican pine forests. These insects play an important role in forests; however at high densities they can alter some ecological processes. In this study, the infestations of Dendroctonus mexicanus are described according to the altitude at which the outbreaks occur, to the infested area, and to the temporary changes of these variables from 2008 to 2012. In addition, the relationship between the number of infested hectares and the standardized precipitation index is analyzed. From 2008 to 2012, 1 435.13 hectares were found to be infested. The infestations were located at an altitude between 1 176 and 3 010 masl, covering practically the entire distribution of the genus Pinus in the area. In the study period there was no evidence of an increase in the altitude at which the infestations occurred; however, an increase in the altitudinal range is observed. The high mortality caused by D. mexicanus to Pinus, regardless of the altitude at which they are found, is an indicator of the expansion of the regional altitudinal range of D. mexicanus after a dry year.