# Siberian Pine and Larch Response to Warming-Drying Climate in the Southern Boundary of Their Range
## 1 Introduction  
Climate-driven changes in trees' growth rate, vigor, mortality, and habitat changes were documented throughout the boreal biome [1; 2; 3; 4]. The mortality of stands formed by conifers has been spreading over an area of several million ha in North America [5; 6; 7; 8] and [9; 10]. Wide-spread spruce (_Picea abies_ L.) mortality occurred in Germany [11], Slovakia [12], and the southern part of European Russia [13]. The main causes of mortality in those areas are considered to be multi-year low precipitation and root-zone drying [2; 14; 15]. Alongside conifer, hardwood species also experienced negative consequences of warming. Thus, _Betula_ sp. growth reduction and mortality were documented within the forest-steppe ecotone, potentially leading to the conversion of these areas into steppe in the future [16]. A large-scale productivity decline of aspen (_Populus tremuloides_ Michx.) has recently been documented throughout the United States and Canada as a result of drought and insect outbreaks [17]. In Central Europe, beech (_Fagus sylatica_ L.) has strongly suffered from the exceptional 2018 drought and subsequent dry years [18; 19]. The influence of increasing aridity is distinct for the different species. Thus, drought-resistant deciduous larch (_Larix_ spp.) increased its range by infilling and shifting its distributions northward, although larch recession and thinning were more common in southern regions [20; 21; 22]. On the contrary, precipitation-sensitive \"dark needle conifers\" (i.e., Siberian pine, fir, and spruce) experienced a decrease in the growth rate and increased mortality in the southern low-elevations. However, those species are migrating uphill and to the northern habitat of larch [23]. An increased rate of tree mortality has been observed since the end of 1990s, and it has coincided with a warming increase (or \"restart\") and consequent drought events increase in the 21 st century. That restart of air temperature has been documented at the local as well as on the global scales (i.e., [[https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/global/time-series/nhem/land/5/9/1950-2024](https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/global/time-series/nhem/land/5/9/1950-2024)]([https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/global/time-series/nhem/land/5/9/1950-2024](https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/global/time-series/nhem/land/5/9/1950-2024)), accessed on 15 September 2023). Meanwhile, in moisture-sufficient habitats (e.g., northern wetlands and alpine ecotone), the warming restart led to a strong increase in trees' growth as well as vegetation primary productivity (both GPP and NPP) [21]. The warming climate also stimulated the expanding of trees' range into high-elevation mountains and northward [20; 24; 25]. Alongside with warming climate, CO\({}_{2}\) fertilization also positively influenced trees' growth [26]. Trees' response to warming is also mediated by relief features. Thus, increased mortality of Siberian pine is mostly observed on steep sunlit southern slopes and in shallow soils with a low water capacity [23]. Moreover, even the drought-resistant larch has experienced water stress on southern slopes [20; 22; 23]. Trees with distinct ecological niches should respond to warming differently. The comparative analysis of such species is essential for predicting climate-driven consequences of climate change on the species' growth, health, and ranges. We suggest that those consequences will be primarily manifested within (1) overlapping parts of species' ranges and (2) within the edges of species' ranges. In this paper, we consider the comparative influence of warming on the growth rate of two main taiga species, namely larch (_Larix__sibirica_ [PERSON]), a deciduous drought-resistant conifer, and the moisture-sensitive evergreen Siberian pine (_Pinus sibirica_ [PERSON]). Among Siberian trees, larch species are the leaders in cold and drought resistance.