Dataset DOI: 10.5061/dryad.4xgxd25nv

Description of the data and file structure

This dataset contains the processed data supporting the main analyses of the study, including climatic variables for trend analysis, NDVI data (1999–2022) and their temporal changes, vegetation line elevation estimates, and summary statistics across six study regions. These data underpin the assessment of vegetation dynamics and their relationship with climate variability presented in the manuscript.

Files and variables

File: Dataset_CSV.zip

Description: 

This dataset comprises four structured data files containing the processed outputs used to generate the main figures and analyses presented in the manuscript. The files are organized by data type and analytical purpose, as described below.

Data 1: Climate data (SD, SKT, TP)
This file contains annual climatic variables derived from the ERA5 reanalysis dataset for the period 1999-2022. The original data (hourly or monthly resolution) were aggregated to annual values to produce the following variables: total precipitation (TP, mm/year), mean annual skin temperature (SKT, °C), and winter snow depth (SD, cm). These variables were used to quantify long-term climate trends across the study regions.

• hydro_year: Hydrological year, defined from November of the previous calendar year to October of the current year
• year: Calendar year, defined from January to December of the current calendar year
• annual_min: Annual minimum value of SKT (°C) or SD (cm) within each year
• annual_max: Annual maximum value of SKT (°C) or SD (cm) within each year
• annual_mean: Annual mean value of SKT (°C) or SD (cm) within each year
• annual_total_precipitation: Total precipitation (mm) accumulated over each year

Data 2: NDVI trends data
This file contains pixel-level NDVI values and derived trend metrics for randomly sampled pixels within each study region. NDVI values were extracted from processed Landsat imagery, using annual composites representing the maximum NDVI for each year from 1999 to 2022.

Pixel-level variables:

• start_NDVI: NDVI value in 1999, representing baseline vegetation conditions
• elevation: Elevation of the pixel location (m)
• slope: Linear regression coefficient representing the temporal trend in NDVI (1999-2022)
• p_value: Statistical significance of the NDVI trend

In addition to pixel-level data, this file includes aggregated statistics summarising vegetation change within elevation bands for each study region:

• elevation_band_median: Median elevation of each band (100 m intervals from 4000 to 6000 m.a.s.l.)
• n_sig_greening pixels: Number of pixels showing a statistically significant positive NDVI trend
• n_sig_browning pixels: Number of pixels showing a statistically significant negative NDVI trend
• n_other pixels: Number of pixels with non-significant NDVI trends
• n_total pixels: Total number of pixels within each elevation band
• greening percentage: Proportion of pixels with significant greening trends within each elevation band (%)
• browning percentage: Proportion of pixels with significant browning trends within each elevation band (%)

Data 3: Vegetation line data
This file provides annual estimates of vegetation line elevation (m) derived using the Triangle method applied in this study. These values represent the upper boundary of vegetation distribution and are used to assess elevational shifts over time.

• vegetation line elevation: Elevation of the upper boundary of continuous vegetation cover for each year (m.a.s.l.)

Data 4: Summary data
This file integrates key variables from the above datasets at the regional scale, including SKT, TP, SD, vegetation line elevation, and the proportions of greening and browning pixels. Annual rates of change were calculated for SKT, TP, SD, and vegetation line elevation, and are presented alongside vegetation change metrics to facilitate comparative and integrative analyses.

• annual_changing_rate: Slope of the linear regression model representing the temporal trend (1999-2022) for each variable, including SKT (°C/year), TP (mm/year), SD (cm/year), and vegetation line elevation (m/year).

Data relationships and usage
The four datasets are linked by study region and year (1999–2022), enabling combined analyses of climate variability, vegetation dynamics, and elevational shifts. Users can reproduce the main results of the study by integrating the climate variables (Data 1), NDVI trends (Data 2), and vegetation line estimates (Data 3), with Data 4 providing a synthesized overview for cross-variable comparison.

All variables are provided in standard units as defined in the manuscript. Missing values, where present, are indicated as NA. Abbreviations used in the dataset include NDVI (Normalized Difference Vegetation Index), SKT (skin temperature), TP (total precipitation), and SD (snow depth).