# Subarctic Vegetation under the Mixed Warming and Air Pollution Influence
## 1 Introduction  
The high warning rate in the Arctic has lead to increased fire rate, permafrost melting, and consequent changes in vegetation productivity and species composition [1; 2; 3]. Within the Siberian Arctic, warming is combined with air pollution caused by smelters located in the Norilsk industrial region. In that region, the subarctic vegetation has experienced the chronic influence of pollutants (mostly sulfur dioxide) over the past 70 years. The scale and consequences of the pollution impact on the subarctic landscapes is a unique phenomenon both within and beyond the Arctic Circle. Norilsk is the world's largest northern city, located 300 km beyond the Arctic Circle (Figure 1). Norilsk's industry provided its first metallurgy products (nickel, copper, cobalt, and platinoids) in 1942. By the end of the 1980s, Norilsk's metallurgy and mining had developed rapidly [4]. In addition to the first nickel and copper plants, a huge plant, named Nadezhda, was constructed in 1979. Nadezhda's emissions were transferred over a longdistance due to its high (250 m) smokestack, located at an elevation of c. 200 m. The smokestacks of copper and nickel plants are shorter (c. 180 m), and they are usually located on the plains. Sulfur dioxide output reached its maximum in 1985 (c. 2.5 M t). At present, emission volume has decreased to c. 1.5 M t due to technological improvements and closure of the nickel plant in 2016 y [5]. Nowadays, Norilsk industry provides, alongside nickel and copper, gold, silver, platinoids (palladium, osmium, iridium, rhodium, and ruthenium), selenium, tellurium, and sulfur [4]. Although that production is in demand worldwide, sulfur and nitrogen oxides and heavy metal pollutants are harmfully influencing subarctic larch-dominant forests and ground-cover communities (mostly moss and lichen), which have experienced decline and mortality since the 1950s [6; 7; 8; 9; 10; 11]. The scale of vegetation disturbances is much larger than in similar areas near the Sudbury industry (Canada) [12], and Monchegorsk, Karabash, and Revda (Russia) [6; 13; 14; 15; 16]. Previous studies of the \"Norilsk phenomenon\" were focused on the pollution-driven temporal dynamics and scale of larch tree growth and vegetation cover mortality [7; 8; 9; 10; 17]. However, those studies did not consider woody species growth dependence on the climate variables or, in a broader aspect, vegetation growth and productivity in the warming subarctic climate. Meanwhile, in a recent paper [11], it was shown that warming led to an increasing trend of larch growth and vegetation productivity within the polluted territories near to Norilsk. The issue of combined pollutions and the influence climate warming on the trees' vigor is still unclear [18]. Thus, [PERSON] et al. [19] hypothesized that warming may increase trees' sensitivity to pollutants because, in warm and rainy climates at low latitudes, trees are more sensitive to pollutants. However, trees at Arctic latitudes are inhibited by a harsh environment, i.e., low air and soil temperatures and short growth period. Current warming has led to a growth increase of the woody species, including permafrost-dominant Larix species [3; 11]. We suggest that more vigorous trees will be less vulnerable to the harsh environment, including air pollutants. We suggest that warming will increase tree growth and decrease tree vulnerability to the habitat's stresses, including pollutants. We hypothesize that climate change at high latitudes might mitigate the influence of adverse emissions on typical subarctic trees (larch, _Larix sibirica_ [PERSON]; spruce, _Picea obovata_ [PERSON]; and birch, _Betula pendula_ [PERSON]) and bush species. We also suggest that warming may lead to increased tree growth and increasing trends of the vegetation cover gross (GPP) and net (NPP) primary productivity. We aim to analyze  
Figure 1: (**a**) The study area. The background: green shows NDVI index mean values (2001–2022); yellow-brown colors show elevations. (**b**) Airborne view of the emissions plum.