Abstract
The Arctic tundra is one of the few biomes that have remained relatively untouched by the direct impact of economic activities. As the Arctic is warming almost four times faster than the global average (Chylek et al., 2022; Rantanen et al., 2022), pressure on the tundra is increasing, complicating efforts to conserve its ecosystems (Ernakovich et al., 2014; Niskanen et al., 2019; Reji Chacko et al., 2023). Plant diversity is a key component of the Arctic tundra as it forms the basis of ecosystem functioning. Plant diversity changes lead to cascading effects throughout the entire ecosystem, and also influence the global climate, primarily via the carbon and energy cycles (Heijmans et al., 2022; Loranty et al., 2014; Oehri et al., 2022). The importance of protecting plant diversity is recognized by Arctic countries through the Arctic Council, and conservation is facilitated by the Conservation of Arctic Flora and Fauna (CAFF) (Barry et al., 2020). About half of the Arctic tundra is located in Russia, a country where independent research is facing serious challenges. In the Russian Arctic climate change and economic expansion are putting pressure on the ecosystems and thus, weakening their ability to maintain plant diversity (Khapugin et al., 2020; Telyatnikov & Pristyazhuk, 2014; Yu et al., 2011). With half of the tundra being located in Russia, pan-arctic conservation strategies need to include the Russian territories in order to maintain the intactness of this biome, even though directly influencing the Russian government's conservation decisions may be difficult given the current political context. The successful development of these strategies requires a thorough scientific understanding of the ecosystems and their functioning informed by up-to-date data on the processes affecting the Russian Arctic tundra and its plant diversity, currently largely missing. Observations on plant diversity in the Russian Arctic have been scattered and mostly not accessible for a comprehensive pan-Arctic analysis. Therefore, in Chapter 1, we translated, standardized and digitized 4785 geobotanical plots collected in the Russian Arctic from 1927 to 2022 and presented them as the Russian Arctic Vegetation Archive (AVA-RU), now available to the international community. The plots document over 1770 plant and lichen species and subspecies, their habitats, and information on the vertical and horizontal structure of vegetation. Climate is changing fast and human activities are expanding across the Arctic, however, our understanding of how they shape tundra species richness is limited. Therefore, in Chapter 2, we utilized AVA-RU data to examine the relative impacts of environmental and anthropogenic factors on community-level plant species richness and its distribution in the Western Siberian Arctic – one of the Arctic regions most affected by anthropogenic pressure. The results reveal an increase in species richness from South-West to North-East, driven mainly by climatic factors, instead of the commonly expected decrease from South to North along the latitudinal gradient. We show that paleoclimatic factors exhibit higher predictive power (up to 21% of explained deviance) even when compared to modern climate, indicating a lasting impact of past climate on tundra vegetation. We suggest that while species richness distribution is mostly driven by environmental factors, a targeted study is needed to assess the human impact. We also show that existing protected areas cover only a fraction of the most species-rich areas. As the Arctic changes, areas with the most extreme climate are likely the most vulnerable to warming. Documenting their diversity and biomass becomes crucial for establishing a baseline to monitor future changes. Therefore, in Chapter 3, we assessed plant and lichen species richness, turnover and biomass, as well as their spatial distribution, in polar deserts — the northernmost biome on Earth. While we only identified 129 species within the 19 surveys, there is a major difference in species richness distribution and turnover. Particularly, 40% of the detected species were found exclusively in a single plot. We also showed that biomass varies widely across the sites, with its maximum on Vize Island, where the mean biomass is comparable to Arctic tundra levels. Overall, my thesis supports the stewardship of Arctic plant diversity in Russia with new baseline data and applications, with the overarching goal of informing and enhancing conservation strategies at both the national and pan-Arctic levels.
Zemlianskii, Vitalii