TITLE:
Piecewise Regression Analysis of Bioclimatic Thresholds in Aboveground Carbon Density of Mexican Temperate Forests
AUTHORS:
Paola Judith Marín García, Jorge Méndez González, Juan Abel Nájera Luna, Librado Sosa Díaz, Andrés Flores
KEYWORDS:
Aboveground Biomass, Bioclimatic, Carbon Density, Thresholds, Vulnerability
JOURNAL NAME:
American Journal of Climate Change,
Vol.15 No.1,
March
6,
2026
ABSTRACT: The accelerating effects of climate change on Mexico’s temperate forests highlight the need for a precise and comprehensive assessment of ecosystem vulnerability. This study quantified how carbon density in aboveground biomass (cdAGB) in key forest species responds to bioclimatic gradients. Twelve taxa from the genera Pinus and Quercus, comprising six pine and six oak species, were assessed using data from the National Forest and Soil Inventory (2015-2020) together with 19 climatic variables. The analytical framework integrated Bayesian correlation analysis, Random Forest, and piecewise regression to identify inflection points or thresholds (ψ) characterizing the relationship between cdAGB and the bioclimatic predictors. Critical thresholds were identified in nine of the twelve species. Temperature-derived predictors exhibited the highest explanatory power. Davies test results showed that cdAGB in five of the studied species (three Pinus and two Quercus) exhibited significant bioclimatic thresholds characterized by abrupt declines within the central range of the predictor gradient (30th - 60th percentiles) Quercus showed a higher proportion of vulnerable sites (>60%) than Pinus (30.3% - 40.8%), and vulnerability probability followed complex, nonlinear spatial patterns structured mainly by latitude and longitude rather than elevation. Collectively, the results confirm a non-linear climate cdAGB relationship and underscore the importance of detecting ecological thresholds to refine projections of forest responses and optimize conservation strategies.