# Subarctic Vegetation under the Mixed Warming and Air Pollution Influence
## 2 Materials and Methods
### Eco-Climate Variables  
We analyzed GI dependence on the air and soil temperature, soil moisture, precipitation, terrestrial water storage (or EWTA), and the volume of SO\({}_{2}\) emissions. Air and soil temperature, precipitation, and soil moisture were obtained from the ERA5-Land database (1951-2022; [[https://cds.climate.copernicus.eu/cdsapp#](https://cds.climate.copernicus.eu/cdsapp#)]([https://cds.climate.copernicus.eu/cdsapp#](https://cds.climate.copernicus.eu/cdsapp#))!/dataset/reanalysis-era5-land-monthly-means?tab=overview, accessed on 6 February 2023; spatial resolution of 0.1\({}^{\circ}\)\(\times\) 0.1\({}^{\circ}\) or 9 km; accessed on 15 October 2022). Soil temperature and moisture  
Figure 4: Maps of air (**a**) and soil (**b**) temperature trends (May–September; 2001–2021) (\(p>0.1\)). Water bodies are indicated by light blue. Black lines show the terrain’s elevation isolines.  
values refer to the topsoil layer (0-7 cm). Soil moisture is measured as a volumetric fraction of water (m\({}^{3}\) m\({}^{-3}\)) ([[https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation](https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation)]([https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation](https://confluence.ecmwf.int/display/CKB/ERA5-Land%3A+data+documentation)); accessed on 6 February 2023). Terrestrial water storage is the product of satellite gravimetric measurements, with an on-ground resolution of 1\({}^{\circ}\)\(\times\) 1\({}^{\circ}\). EWTA is characteristic of the moisture regime and represents total terrestrial water storage in cm units [23]. EWTA values were obtained from the NASA-JPL database ([[https://podaac-opendap.jpl.nasa.gov/opendap/hyrax/allData/tellus/L3](https://podaac-opendap.jpl.nasa.gov/opendap/hyrax/allData/tellus/L3)]([https://podaac-opendap.jpl.nasa.gov/opendap/hyrax/allData/tellus/L3](https://podaac-opendap.jpl.nasa.gov/opendap/hyrax/allData/tellus/L3)), accessed on 6 February 2023). The volumes of SO\({}_{2}\) emissions were obtained from published data [5; 6; 24]. The data of sulfur dioxide transfer were obtained from the ESA Copernicus Sentinel-5P Mapping Portal [25]. We also generated the wind rose for the study area based on the daily wind direction dataset obtained from the nearest weather stations (69.33\({}^{\circ}\) N/87.95\({}^{\circ}\) E and 69.33\({}^{\circ}\) N/88.25\({}^{\circ}\) E). In the analysis of GI dependence on sulfur dioxide emissions and climate variables, we used data from 1993 because it coincided with reliable SO\({}_{2}\) data and with the beginning of the current warming.  
We used gross (GPP) and net (NPP) primary productivity and normalized vegetation index (NDVI) to estimate the trends of vegetation cover productivity. GPP values (C kg/ha), calculated based on summer 8-day GPP composites, were obtained from the Terra/MODIS product MOD17A2H version 6.0 ([[https://lpdaac.usgs.gov/products/mod17a2](https://lpdaac.usgs.gov/products/mod17a2) hv006]([https://lpdaac.usgs.gov/products/mod17a2](https://lpdaac.usgs.gov/products/mod17a2) hv006); spatial resolution 500 m; accessed on 15 October 2022) [26]. NPP annual values (C kg/ha) were extracted from the Terra/MODIS product MOD17A3 HGF version 6.0 ([[https://lpdaac.usgs.gov/products/mod17a3](https://lpdaac.usgs.gov/products/mod17a3) hgfv006]([https://lpdaac.usgs.gov/products/mod17a3](https://lpdaac.usgs.gov/products/mod17a3) hgfv006); spatial resolution 500 m; accessed on 15 October 2022) [27]. NDVI (16-day composites) was obtained from the Terra/MODIS product MOD13Q1 ([[https://lpdaac.usgs.gov/products/mod13q1v006](https://lpdaac.usgs.gov/products/mod13q1v006)]([https://lpdaac.usgs.gov/products/mod13q1v006](https://lpdaac.usgs.gov/products/mod13q1v006)); spatial resolution 250 m; accessed on 15 October 2022). We created mosaics of GPP, NPP, and NDVI composites. We then calculated raster datasets of median values for each year. Datasets were used to generate maps of the GPP, NPP, and NDVI mean values and trends for the 2001-2022 time interval.