Temporal variation of the resilience of Pinus durangensis Martínez to extreme climate events in northern México.

Abstract

Understanding, predicting, and quantifying the tree growth response o to extreme drought events is of great interest. The main objective of this study was to evaluate the temporal variation of the resilience of Pinus durangensis to extreme climatic events. 286 cross-sections of P. durangensis were analyzed using conventional dendrochronological techniques. In addition, total ring width, earlywood, and latewood chronologies were generated, spanning 296 years. The association between the tree-ring series and drought was analyzed through the Standardized Precipitation-Evapotranspiration Index (SPEI). The residual earlywood chronology showed the greatest association with the six-month cumulative SPEI for February-May (SPEI6FM). This allowed the reconstruction of 296 years of the SPEI6FM, where 18 % were classified as wet years, 16 % were dry, and 66 % presented average values. Subsequently, the radial growth of 200 cross-sections extracted at different heights from the stem of P. durangensis trees was analyzed and ring-width indices (RWI) were generated. Seven extreme drought events were identified and the annual radial growth before, during, and after each drought event was determined. Based on the RWI values, resistance, recovery, and resilience indices were calculated. The results indicated a significant correlation (p ≤ 0.05) between the annual radial increase and drought along the stem (0.56—0.80). The climatic sensitivity was higher in the lower part of the stem. The values of the resistance index ranged between 0.44 and 0.76 and were better expressed in the highest sections of the stem. Resilience indices changed over time. Regardless of the height of the tree trunk, recent extreme drought events have caused a lower resilience of the trees, indicating a decrease in their capacity for recovery. These results represent an advance in the understanding of the tree growth behavior along the stem, laying the foundations for future studies on this and other tree species in Mexico.