Introduction: Basal area increment (BAI) is an indicator of forest productivity that
varies with tree age and site factors such as soil and climate.
Objective: To generate tree-ring width index (RWI) and BAI chronologies of Pinus
hartwegii Lindl., relate them to climatic variables, and study the variation in BAI at
different altitudes and aspects.
Materials and methods: Four observation sites were identified, combining
northwest (NW) and southwest (SW) aspects, as well as altitudes of 3 800 and 3
700 m. At each site, the temperature was recorded every four hours for 435 days
and 32 growth ring segments were collected using a Pressler´s increment borer.
Tree-ring width was measured and BAI was calculated; the correlation index
between these indicators and the climatic variables was Pearson’s correlation
Results and discussion: The RWI series from the four observation sites had an
intercorrelation of 0.33 (P < 0.01). Two low-growth periods were detected, one
between 1950 and 1960 and the other between 1990 and 2005. Site SO-3700 had
a different growth pattern, due to a second growth phase beginning in 1978,
possibly a benefit resulting from increased temperature. The previous autumn
temperature, spring temperature and April-September precipitation of the current
year explained the variation in BAI (P < 0.05).
Conclusion: The BAI of P. hartwegii could respond favorably to the predicted
increases in temperature at an altitude of 3 700 m with southwest aspect.