2021/06/09 by Broukhim, Mona, Early, Benjamin, Sanchez, Luis Orozco
#Pinus coulteri #Pinus jeffreyi #Pinus lambertiana #bark beetles #climate change
paper · doi:10.21973/n3rh3f
Pine species in the southern fringes of their range are experiencing changes related to climatic pressures which may in turn affect their susceptibility to bark beetle invasions. These environmental stressors can lead to changes in a pines ability to produce resin as a defensive measure. This study of Pinus jeffreyi, Pinus coulteri, and Pinus lambertiana aims to identify the species of most concern and the overall health of the pines in the San Jacinto Mountains. Pines were systematically sampled, and data was collected on various environmental conditions and stressors affecting each tree. Differences in each Pinus spp. resin flow rates were calculated and used to measure the trees’ ability to ward off a bark beetle invasion. An index was then created based on observed physical attributes to individual trees and used as a proxy of general health. Jeffrey pines (Pinus jeffreyi) were found to have the highest resin flow rate as well the highest index rating. Sugar pines (Pinus lambertiana) were found to have the lowest resin flow rate and lowest rating on the index. Slope was also found to be an accurate predictor of resin flow rate. Differences in resin flow rates and general health among Pinus spp. suggest that pines are handling shifting environmental conditions differently. Although Jeffrey pines are known to be drought tolerant, our results indicate that they are the pine species at most risk in the San Jacinto Mountains. Pine forests at their southern fringes must be monitored and managed more closely for bark beetle invasions and other stressors that could decimate these habitats. We propose not only cost-effective forest health monitoring methods, but also suggest appropriate land management practices.