Climatic Influences on Basal Area Increment of Forests in a Mountainous Landscape

Aims: The aim of this work is to assess the influence of temperature (T) and precipitation (P) on Basal Area Increment (BAI) of Pinus cooperi in a mixed conifer forest ecosystem. We hypothesize that the sensitivity of annual tree growth to climate variables will increase with increasing elevation.
Study Design: The study area is located in "Las Rusias" mountain, in northwest Mexico. The sample design consisted of selection of three sites with different elevations: Low (L), Mid (M) and High (H), of representative stands of Pinus cooperi.
Place and Duration of Study: The field work was carried out in October 2011, whilst processing data was done at Lab in December 2011.
Methodology: Increment cores were collected from 3-10 trees at each site along the elevational gradient. Increment cores were extracted for each tree of Pinus cooperi at 1.3 m height using increment borers of 5 mm. Increment cores were processed using standard dendrochronological techniques. In order to determine the climatic response of the BAI chronology, BAI data was associated with climate records (1946-2010) from the nearby weather station.
Results: The bootstrapped procedure conducted between the BAI and climatic variables showed significant correlations for the study area. All correlation coefficient values ranged from -0.5 to 0.42 (p<0.05). The Pearson´s coefficients indicated that BAI has been driven largely by (P) and (T) along the gradient.
The relationships between BAI and P showed similar trends for the three elevations. P. cooperi BAI was positively correlated with precipitation during the previous winter.
Conclusion: The results showed that the hypothesis that sensitivity to rainfall and temperature will vary along the elevation gradient appears reasonable. These findings could be used to suggest strategies for forest management, however some stand dynamics factors should be considered as well.