Non-structural carbohydrates’ (NSCs) allocation pattern is closely related to environmental factors, plant metabolism, and xylem function. At the same time, we know little about whole-tree NSC allocation patterns in different seasons, especially the high-elevation species which suffer from environmental stress. We examined the concentration of NSCs in various parts of Faxon fir trees (needles, branches, trunks, and roots) at five elevations (2800 m, 3000 m, 3200 m, 3400 m, and 3600 m) over four months (July 2019, October 2019, January 2020, and April 2020). The goal was to understand how NSC allocation patterns vary by location and time in high-elevation species and what factors contribute to these variations. The results showed that the needles had the highest concentration, followed by roots, branches, and trunks. The NSC concentration was highest in January 2020 and lowest in July 2019. The total non-structural carbohydrates (TNSCs) and soluble sugar concentrations of roots and needles were substantially higher in the cold (non-growing season) than in the warm (growing season) season. At different elevations, the soluble sugar concentrations in the needles and trunks remained the highest and lowest, respectively. Branches and roots’ soluble sugar concentrations alternated and varied with the seasons at all elevations. Many factors, such as climate, morphological traits, and carbon content, affected the spatial and temporal patterns of non-structural carbohydrates, with temperature, plant moisture conditions, and carbon content being the main driving factors. Various factors’ interaction mainly influenced NSCs’ spatial and temporal patterns. Non-structural carbohydrates significantly improve the resistance of Faxon fir trees’ terminal organs in adverse environments.

The main research content of the field of ecological stoichiometry is the energy of various chemical elements and the interaction between organisms and the environment throughout ecological processes. Nitrogen and phosphorus are the main elements required for the growth and development of plants and these also form the constituent basis of biological organisms. Both elements interact and jointly regulate the growth and development of plants, and their element ratios are an indication of the nutrient utilization rate and nutrient limitation status of plants. Previous research developed a general biogeography model of the stoichiometric relationship between nitrogen and phosphorus in plant leaves on a global scale. Further, it was shown that the relative rate of nitrogen uptake by leaves was lower than that of phosphorus, and the scaling exponent of nitrogen and phosphorus was 2/3. However, it is not clear how the stoichiometric values of nitrogen and phosphorus, especially their scaling exponents, change in the leaves of Chinese woody plants in response to changing environmental conditions. Therefore, data sets of leaf nitrogen and phosphorus concentrations, and nitrogen to phosphorus ratios in Chinese woody plants were compiled and classified according to different life forms. The overall average concentrations of nitrogen and phosphorus in leaves were 20.77 ± 8.12 mg g^-1 and 1.58 ± 1.00 mg g^-1, respectively. The contents of nitrogen and phosphorus in leaves of deciduous plants were significantly higher than those of evergreen plants. In leaves, life form is the main driving factor of nitrogen content, and mean annual temperature is the main driving factor of phosphorus content; soil available nitrogen is the main driving factor of the nitrogen to phosphorus ratio. These values can be used for comparison with other studies. In addition, the scale index was found to be significantly different among different life forms. The scaling exponents of N-P of woody plants of different life forms, such as trees, shrubs, evergreen, deciduous, and coniferous plants are 0.67, 0.72, 0.63, 0.72, and 0.66, respectively. The N-P scaling exponent of shrubs was higher than that of trees, and that of deciduous plants was higher than that of evergreen plants. These results suggest that the internal attributes of different life forms, the growth rate related to phosphorus, and the relative nutrient availability of soil are the reasons for the unsteady relationship between nitrogen and phosphorus in leaves.

Abies fargesii var. faxoniana, an endemic evergreen conifer of ecological and economic importance in China's montane regions, faces escalating threats from anthropogenic climate change. This study integrates paleoecological reconstruction and future climate scenarios to (1) decipher the species’ climate-distribution relationships, (2) identify critical bioclimatic thresholds, and (3) predict range shifts under warming scenarios. Using 60 georeferenced occurrence records and 19 bioclimatic variables, we developed a Maximum Entropy (MaxEnt) model with exceptional predictive accuracy (AUC = 0.997). The species’ potential distribution was reconstructed for four key periods: last glacial maximum (LGM, 22 kyr BP), mid-holocene (6 kyr BP), current era, and future scenarios (RCP 2.6 and 8.5 for 2050s/2070s) through ArcGIS-based spatial analysis. Key findings revealed that contrary to expected post-glacial migration patterns, the Sichuan Basin served as a Pleistocene microrefugium, with stable, suitable habitats (≥0.6 probability) maintaining 83.7% continuity since the LGM. Current optimal habitats concentrate in Sichuan (48.2%), Gansu (31.5%), and Shaanxi (17.3%), exhibiting <5% fluctuation since Mid-Holocene. Projected range reductions of 12.4% (RCP2.6) and 18.7% (RCP8.5) by the 2070s, primarily through elevational compression rather than latitudinal shifts. Thermal thresholds (Bio1, Bio7) explained 64.3% of distribution variance, interacting with precipitation extremes (Bio18-19) to define ecological amplitude.