Growth ring components of Pinus hartwegii Lindl. at the altitudinal distribution limits in east-central Mexico

Introduction: Climate change will have a differential impact on mountain forest growth linked to elevation. Objective: To evaluate the interrelationships of growth ring components at altitudinal gradient limits of Pinus hartwegii Lindl. in three mountains of east-central Mexico. Materials and methods: We analyzed 295 tree samples from Cofre de Perote, Pico de Orizaba and Monte Tláloc corresponding to the period 1960-2017 with a total of 17 700 observations per variable (ring width and density [TRW, TRD], earlywood [EWW, EWD], latewood [LWW, LWD] and minimum and maximum density [MID, MAD]). Results and discussion: Growth parameters were higher at the lower limit (≈3 500 m). The correlation of TRW with EWW (r ≥ 0.95) and LWW (r ≥ 0.78) was significant (P < 0.05). TRD correlated with EWD (r ≥ 0.83) and MID (r ≥ 0.72), as well as EWD with MID (r ≥ 0.92) and LWD with MAD (r ≥ 0.92). At the upper limit (≈4 000 m), correlations of TRW, EWW and LWW with TRD, EWD and MID were negative (-0.3 ≥ r ≥ -0.8). This may be explained by lower temperatures and growth periods reducing the relative importance of latewood in ring width. Conclusions: The information provided contributes to understand the dynamics of P. h ar t we g ii xylogenesis in response to climate and possible implications for radial growth facing climate change.