It is well known that tree growth is strongly affected by climate at high elevations, but it is still unclear how climate variability influences the distribution of montane forest ecosystems, particularly tree line species. To advance knowledge in this field, we combined temporal (tree ring measurements) and spatial data (remotely sensed variables), to quantify how forests responded to climatic variability across altitudinal gradients in Central Mexico. Normalized difference vegetation index (NDVI), tree‐ring chronologies, and site‐level climatic data were used in a vegetation trend analysis of greenness and browning and to reconstruct canopy vigor for the last century. Although a common ring width chronology was developed, we found significant site‐dependent forest growth response, where young trees (<100 years) exhibited heterogeneous growth trends, without an altitudinal pattern. However, mature trees (100–200 years) showed a common growth decline during the middle twentieth century, regardless of their altitude. Annual maximum NDVI anomalies did not show a general greening effect at high‐elevations. The forest showed both greening and browning zones denoting spatial variability in tree vigor. Furthermore, temperature from the previous year had a positive effect on both NDVI and ring width index but negative at beginning of the growing season. The significant relationship between winter‐spring NDVI (December to March) and ring width index (r = 0.64, p < 0.05), was useful to reconstruct the canopy vigor for the last 151 years. Thus, the greening effect derived from NDVI should be carefully interpreted as a direct forest growth increase. These results highlight the potential of integrating remotely sensed and dendrochronological methods to improve predictions of forest ecosystem responses.

An interdisciplinary approach is needed for understanding tree physiology and forest biogeochemical cycles undergoing climate change and rising atmospheric CO₂. We combined tree ring time series, wood isotope signatures, remotely sensed variables, and climatic data to perform a spatiotemporal scaling analysis of tree physiology and high‐elevation forest responses to rising CO₂. The main question addressed is how tree physiological performance of dominant trees can be combined with satellite‐derived information of stand‐level productivity to understand how the landscape shapes the relationship between forest structure and function. Annually resolved tree ring carbon and oxygen isotopic ratios (δ¹³C and δ¹⁸O), carbon isotope discrimination from CO₂ to wood (Δ¹³C), and intrinsic water‐use efficiency (iWUE) of dominant Pinus hartwegii Lindl. trees were sampled and compared against stand‐level normalized difference vegetation index (NDVI) time series from 2000 to 2016. Linear mixed‐effects models tested the effects of elevation, aspect, and time. Carbon and oxygen isotope ratios were correlated with NDVI mainly for the previous fall‐winter season and for the beginning of the growing season. Wood δ¹³C decreased over time regardless of spatial position, whereas wood δ¹⁸O varied as a function of altitude and time. Although Δ¹³C did not vary with elevation, aspect, or time, a notable decline in Δ¹³C and peak in iWUE during a severe drought event was evident. Results highlight the link between remotely sensed data, tree ring isotopic composition, and tree physiology as the determining factors to determine spatiotemporal variability in dendroecological studies.

Understanding how trees respond to extreme events is important to predict how climate change will impact forests in the future. In this study, we report changes in radial growth and tree‐ring carbon (δ¹³C) and oxygen (δ¹⁸O) stable isotope ratios of Pseudotsuga menziesii (Douglas‐fir) in western Mexico. Tree growth was compared with δ¹³C and δ¹⁸O ratios recorded during dry and wet periods caused by El Niño‐Southern Oscillation since 1850. The three driest and three wettest events during the studied period caused tree growth decline of up to 50% followed by 6–10 years of slow recovery until baseline growth was regained. Wet events resulted in up to 17% growth increase, a positive effect that persisted for no more than 3–5 years. Stable isotope ratios recorded physiological adjustments that in some cases correlated significantly with tree growth. Excursions in tree‐ring Δ¹³C and δ¹⁸O isotope ratios suggest that trees cope with dry and wet periods with proportional but divergent adjustments in photosynthesis versus stomatal conductance. Notably, the intrinsic water‐use efficiency—that is, the ratio between carbon assimilation and water loss through transpiration—was positively correlated with tree basal growth only during dry periods. We found no significant correlations between growth and intrinsic water‐use efficiency during wet periods. Contrary to expectations, rising CO₂ levels over the past ~160 years did not affect tree growth response to precipitation variability.

Las especies forestales como Pseudotsuga menziesii (Mirb.) Franco son sensibles al clima y muestran anillos de crecimiento claramente definidos. La selección cuidadosa de árboles dominantes con fuste circular permite el análisis de tendencias de crecimiento arbóreo. En este estudio se utilizaron mediciones directas del incremento del área basal (IAB) para explicar las periodicidades biológicas y elaborar predicciones del crecimiento en el abeto Douglas-fir que crece en el oeste de México. Para eliminar el efecto de la edad en el crecimiento de los árboles se hizo un análisis en términos de la edad del cámbium. Los resultados mostraron correlación significativa (P < 0.05) entre IAB y la precipitación de enero a julio. Además, se encontraron periodicidades de 7, 21, 27 y 60 años en el crecimiento de los árboles; el periodo de 60 años fue determinante para la construcción de un modelo ARIMA (0,1,1) para realizar predicciones del IAB en las próximas décadas. Las proyecciones del crecimiento proponen una reducción del IAB en árboles maduros dominantes en las próximas décadas. Dicha reducción es un resultado inesperado, debido a que el IAB en árboles dominantes permanece constante hasta una edad biológica de senescencia. Los resultados concuerdan con una tendencia general de reducción en el crecimiento en otros bosques del mundo debido a estrés hídrico, lo cual sugiere que la variabilidad climática futura puede empeorar la condición de salud del abeto Douglas-fir de los bosques del norte de México.

Ongoing climate variability strongly affects high-elevation forests, influencing the wood formation process (e.g., xylogenesis). Furthermore, spatio-temporal studies to establish links of wood properties and tree performance are needed. Using linear mixed-effects models, empirical cumulative distribution functions, and spatial analysis, we explore time trends and space connections of wood density of Pinus hartwegii Lindl. to remotely sensed variables (Moderate Resolution Imaging Spectro-radiometer MODIS-derived) in two high-elevation forests in México, Tláloc (TLA) and Jocotitlán (JOC) Mountains. Results indicated that elevation and cambial age effects are important factors explaining wood density variation. Minimum earlywood—MID, average—AVE, and maximum latewood density—MXD were statistically similar between mountains (p > 0.05), but TLA showed a significant increase in MID over time with higher values after 1950. Wood density values and spatial correlations were site-dependent with TLA exhibiting the highest correlations between MXD and the Normalized Difference Vegetation Index (NDVI) of the spring season (r = 0.59, p < 0.05). Overall, correlations to remotely sensed information were positive with MXD, negative for MID and divergent for AVE. Historical temperature defines MID along the elevation gradient, while MXD was related to soil moisture only at low-elevation sites where soils are deeper. We found that two high-elevation forests, 115 km away from each other, with similar climate, soil, and vegetation, behaved differently regarding their xylogenesis, indicating the potential of using the link between wood micro-density and remotely sensed information to understand forest response to climate change effects.