Research Highlights: Analyzing the contrasting ecological gradients makes it easier to understand the influence of climate on carbon accumulation. Background and Objectives: The increasing climatic variability has implications for vegetation, impacting on its ecological functions, among which carbon accumulation stands out. In the present study, we used climate-dendrochronology relationships to evaluate carbon accumulation in two conifer species that grow in contrasting humidity sites: Pinus strobiformis Engelm (mesic sites) and Pinus leiophylla var. chihuahuana (Engelm.) Shaw (arid sites). Materials and Methods: Using a dendrochronological approach, we estimated the correlation of biomass and carbon accumulation of each species with some climatic variables (temperature, precipitation, and a drought index) and generated a linear mixed model. Results: The response in carbon accumulation between species with respect to climate was significantly different. P. strobiformis showed a positive correlation with the climatic variables analyzed, while in P. leiophylla the correlation was negative, except with precipitation. Conclusions: These results show that forests in both mesic and arid sites are prone to climate changes, although their responses are different, impacting the productivity and carbon cycles of forest ecosystems.

We studied the correspondence between historical series of tree-ring width (TRW) and the normalized difference vegetation index (NDVI, i.e., greenness index) values acquired monthly over an entire year by unmanned aerial vehicles. Dendrochronological techniques revealed differentiated responses between species and seasonality. Pinus engelmannii Carrière and Juniperus deppeana Steudel were affected by warm temperatures (TMAX) during the winter prior to growth and benefited from precipitation (PP) during the seasons prior to the spring period. The standardized precipitation–evapotranspiration index (SPEI) confirmed the high sensitivity of P. engelmannii to drought (r = 0.7 SPEI). Quercus grisea Liebm. presented a positive association with PP at the beginning and end of its growth season. Monthly NDVI data at the individual tree level in the three species (NDVI ~0.37–0.48) statistically confirmed the temporal differences. Q. grisea showed a drastic decrease during the dry season (NDVI = 0.1) that had no impact on drought sensitivity in the same period, according to the climate-TRW relationship. We conclude that a relationship is plausible between the crown greenness index and radial growth, although more extended temporal windows of the NDVI should be explored. Differences in susceptibility to drought found among the species would presumably have implications for the composition of these forests under drought scenarios.

Despite recurring episodes of fire exacerbated by climate change, post-fire dynamics in trees remain to be fully understood. In a mixed forest in northern Mexico that experiences frequent fires, we aimed to determine how tree growth responds to surface fire by examining earlywood (EW) and latewood (LW) responsiveness, as well as their connection with canopy activity, using UAV-acquired NDVI data. We compared EW and LW growth from mini cores of burned and unburned trees (n = 100) across four species, correlating this with NDVI data from 33 UAV monthly flights at the individual tree level from 2021 to 2023. Our results identified Quercus durifolia Seemen as the species that presented the highest growth following exposure to surface fire. Arbutus arizonica (A. Gray) Sarg. was the species most affected by fire in terms of EW production immediately after burning but showed benefits in subsequent summers. Juniperus deppeana Steud. demonstrated adaptive plasticity by responding more quickly to fire, with notable growth in EW. Pinus engelmannii Carrière responded in 2023, and its NDVI was associated to the least extent with seasonal growth. Thus, there is an evident seasonal response in trees subjected to low-intensity fire, which can act to shape the stand habitat. However, there is a divergence in response between broadleaf and evergreen species that could be attributed to fire-adaptive traits and hydraulic strategies. Although combining the tree-ring data with the NDVI served to improve our understanding of the effects of fire, further research is required.

Severe drought events have raised concerns regarding their effects on the phenological cycles of forest species. This study evaluates the correspondence between in situ phenophases and those detected by an unmanned aerial vehicle (UAV) in tree species coexisting within a mixed forest, with particular attention to their relationship with climatic variables. Based on 12 consecutive monthly field observations, we compared phenological developments with UAV-derived normalized difference vegetation index (NDVI) values, which were then correlated with environmental variables. The analysis revealed a convergence of inflection points and seasonal phenological shifts, likely driven by climatic factors, although distinct patterns emerged between coniferous and broadleaf species. Photoperiod (PP), vapor pressure deficit (VPD), maximum temperature (TMAX), and, to a lesser extent, precipitation (P) were the primary environmental variables influencing NDVI results, used here as a proxy for phenology. Photothermal conditions revealed seasonal asynchrony in NDVI responses between coniferous and broadleaf species, exerting a positive influence on conifers during summer, while having a negative impact on broadleaf species in spring. Validation of in situ observations with UAV-derived data demonstrated a biological correlation between canopy dynamics and NDVI values, supporting its use as a proxy for detecting phenophases at the level of individual trees.