What Are Contemporary Mexican Conifers Telling Us? A Perspective Offered from Tree Rings Linked to Climate and the NDVI along a Spatial Gradient

Abstract

Forest structure and composition have changed rapidly worldwide, presenting tendencies towards an increasing proportion of younger trees. From chronologies of tree-ring indices (TRI) and the reconstruction of the basal area increment (BAI), a dendroecological study was conducted from the perspective of the radial growth of twelve contemporary conifer species in a highly diverse region of the planet. From an elevational perspective, the TRI were associated with climate and the NDVI, while the BAI was also modeled as a potential proxy for forest productivity. Climate affects the species differently according to elevation: at 1900 m asl, Pinus caribaea, P. oocarpa and P. jeffreyi presented the lowest sensitivities to climate and drought. For their part, species occupying the intermediate part of the gradient (1901–3000 m asl), such as P. engelmannii, P. patula, P. johannis and P. maximartinezii, were very sensitive to maximum temperature (TMax), precipitation (PP) and drought during the winter–spring period. Finally, of the species distributed on the upper part of the gradient (>3000 m asl), only Abies religiosa was associated with TMax and drought; Juniperus deppeana, A. hickelii and P. hartwegii did not seem to be vulnerable to drought. Complementarily, we found significant differences in the BAI as a function of elevation, with the sites at 1001–1500 m asl presenting higher BAI. The results suggest that the growth in these forests is impacted by droughts and follows a distinct spatial pattern, with greater restriction found in mid-elevation forests. Consistent implications are also observed in BAI trends. For its part, the NDVI demonstrated a decreasing tendency in greenness from south to north, although no elevation pattern was evident. The combined proxies utilized here produced parameters that improve our understanding of forest growth and should be considered in vegetation dynamics models in order to reduce their uncertainty in the face of climate vulnerability. These forests must be sustainably managed, and it is therefore crucial to determine the influence of ecological variables on their growth.

Reconstruction of NDVI based on Larix gmelinii tree-rings during June–September 1759–2021

“…The signal-to-noise ratios of all three elevation chronologies were high, and were enhanced for elevations between 14.664 and 33.645. This demonstrates that the availability of climate information contained in the larch tree ring variation increased with the elevation, as did the quality (Pompa-García et al, 2022). The overall representativeness of the three samples from high to low elevation were 0.971, 0.950, and 0.936, all of which are greater than 0.85.…”

“…However, the relationship between tree rings and NDVI is very different due to the differences in local conditions. For example, Pompa-García et al (2022) found that the relationship between the tree ring chronology of Mexican coniferous species and NDVI did not vary with altitude, however, differences were observed for latitudes changing from south to north, and the relationship gradually weakened toward the north. But Wen et al (2022) found that the correlation between the tree ring width of Picea schrenkiana and NDVI in the Tianshan Mountains decreased with increasing altitude, with gradually decreasing trend from the west to east in longitude.…”

Rates of Stemwood Carbon Accumulation Are Linked to Hydroclimate Variability in Mexican Conifers

“…The combined effect of rainfall and high temperatures at the beginning of the growing season may stress trees through the negative impact of elevated evapotranspiration rates [50,51]. The effects of increased temperatures with severe precipitation deficits have caused forest dieback and tree mortality due to high transpiration rates and hydraulic failure [1].…”

Vegetation Index Research on the Basis of Tree-Ring Data: Current Status and Prospects

“…Treering parameters have been widely used in both small-scale climate response studies and large-scale reconstruction studies for their various advantages, including their ability to yield accurate date information, their high continuity and temporal resolution, their wide availability, and the ease with which several copies of tree rings can be obtained [8,9]. The main advantages of NDVI data on the basis of remote sensing satellite data are the ease with which these data can be acquired, their wide coverage, and their temporal resolution, which permits vegetation growth to be detected over larger areas [10][11][12]. However, the collection of remote sensing vegetation index data has a short history.…”