# Pollution and Climatic Influence on Trees in the Siberian Arctic Wetlands
###### Abstract  
Siberian Arctic wetlands located within the planetary \"warming hotspot\" experience pronounced climate-driven vegetation cover changes. Together with warming, wetlands, which are located within the influence of Norilsk copper and nickel industry (69.35\({}^{\circ}\) N, 88.12\({}^{\circ}\) E), have been strongly influenced by industrial pollutions (sulfur dioxide mostly) since the 1940s. In addition, petroleum products release occurred in 2020 that potentially influenced vegetation vigor. We studied the combined effect of climate warming and pollution on the larch (_Laris [PERSON]_) and shrubs\" (_Salix_ spp. and alder, _Duschkia fruticosa_) growth. Using satellite data (MODIS and Sentinel) processing, we mapped wetlands within the study area. We used on-ground survey, and applied dendrochronology, climate variables, and emissions rate analysis. We sampled woods (kerns) and, based on the tree ring analysis, generated trees and shrubs growth index (GI) chronologies. We analyzed the influence of the SO\({}_{2}\) emissions and eco-climate variables (air temperatures, precipitation, soil moisture, and drought index SPEI) on the larch and shrubs GI. We mapped GPP and NPP (gross and net primary productivity) and vegetation index NDVI and temporal trends of these indexes based on the MODIS-derived products. We found that chronic SO\({}_{2}\) influence led to larch trees GI decrease that was followed by tree mortality, which was observed until the end of 1990. Since the beginning of the 2000s, the GI of larch and shrubs has increased, which is correlated with elevated air and soil temperature and growth season prolongation, whereas excessive soil moisture negatively influenced GI. Together with that, increasing trends of vegetation indexes (GPP, NPP, and NDVI) were observed on the part of wetland within the zone of former trees' heavy damage and mortality. The trends began mostly in 2003-2005 and were caused by emissions volume decrease and warming, together with resistant species' (willows, graminoids, bushes, and birch) growth and invasion. We suggested that increasing productivity trends might partly be attributed to nitrogen fertilization caused by NOx emissions. Finally, we found that diesel fuel spill which happened in 2020 caused no influence on the larch, whereas some aquatic species (masses mostly) were damaged. air pollution; arctic wetlands; climate-driven trees growth; larch growth; pollution-driven tree mortality; Siberia; emission +
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the polluted zone was caused by the Norilsk industry region. Chronical emissions (sulfur dioxide mostly) have influenced the wetland vegetation, including sparse and open forests, since the 1940s. This is a unique combination of the technogenic and climatic influence on the wetland vegetation within the completely circumpolar zone and beyond. Norilsk city, one of the five most northward world cities, is located 300 km beyond the Polar Circle within the permafrost area of the Taymyr peninsula (Figure 1). Norilsk industry began in 1935 with the construction of nickel and copper plants. Firstly, concentrates of copper and nickel were obtained in 1939. Refined nickel, copper, cobalt, and platinoids production took place in 1942-1944. Since then, metallurgy and mining have rapidly continued to expand until the end of the 1980s [4]. Nadezhda, a huge third plant, started to work in 1979-1981. In 1985, Nadezhda production reached its planned volumes. Emissions from Nadezhda smelter are transferred over long distances due to high (250 m) smelter located on the plateau with elevation c. 200 m. The heights of the copper and nickel smokestacks are about 180 m and they are located in the lowlands. The Norilsk industry's maximal production reached its maxima in 1989. However, in 1991, production decreased twice with minimum values in 1993. Nowadays, Norilsk industry provides, alongside nickel and copper, gold, silver, platinoids (palladium, osmium, iridium, rhodium, and ruthenium), selenium, tellurium, and sulfur [4]. Figure 1: Study area location.