ISSN 1995-4255, Contemporary Problems of Ecology, 2017, Vol. 10, No. 5, pp. 476–487. © Pleiades Publishing, Ltd., 2017. Original Russian Text © A.V. Demina, L.V. Belokopytova, S.G. Andreev, T.V. Kostyakova, E.A. Babushkina, 2017, published in Sibirskii Ekologicheskii Zhurnal, 2017, No. 5, pp. 553–566. Radial Increment Dynamics of Scots Pine (Pinus sylvestris L.) as an Indicator of Hydrothermal Regime of the Western Transbaikalia Forest Steppe A. V. Deminaa, *, L. V. Belokopytovaa, S. G. Andreevb, T. V. Kostyakovaa, and E. A. Babushkinaa aKhakasia Technical Institute, Siberian Federal University, Abakan, 655017 Russia bBaikal Institute of Nature Management, Ulan-Ude, 670047 Buryatia, Russia *e-mail: [email protected] Received January 20, 2017; in final form, March 28, 2017 Abstract⎯The radial increment of Scots pine growing in the forest-steppe zone of Western Transbaikalia at five sites is studied. For each site, additional samples are collected, which allows us to increase reliability and build two regional chronologies. An analysis of chronology correlations with monthly temperatures, precip- itation, and Selyaninov hydrothermal coefficient is carried out. The analysis of 10-day moving climatic series makes it possible to clarify the periods of climate impact on the increment: the main limitation of pine incre- ment in the region is observed by moisture supply, including conditions during previous (from late July to late September) and current (May to mid-July) vegetative seasons. Fluctuations of 23–35 years in the dynamics of climatic factors and radial increment of the pine are found. Keywords: radial increment, Scots pine (Pinus sylvestris), temperature, precipitation, Selyaninov hydrother- mal coefficient, Western Transbaikalia, forest steppe DOI: 10.1134/S1995425517050031 INTRODUCTION erson et al., 2001; Batima et al., 2005; Dulamsuren et al., 2010). In these conditions, studies of climate The continental temperate zone of Central Asia is and its influence on forest ecosystems of Central Asia influenced by rather harsh climatic conditions, a lack at the regional scale are of high significance. One such of moisture during the vegetative season, and low tem- region is Western Transbaikalia. It is characterized by peratures (Dulamsuren et al., 2009, 2014). Low tem- a developed forest-steppe ecotone and a low extent of peratures limit tree growth in the highlands and deter- dendroecological study. In 1999, in this region data on mine position of the upper tree line (Jacoby et al., radial increment of the Scots pine (Pinus sylvestris L.) 1996). At the same time, the high annual variability in and the analysis of its responce to regional climatic precipitation leads to an alternation of relatively wet and hydrological fluctuations were obtained (Andreev periods and droughts, limiting the dispersal of woody et al., 1999, 2001a, 2001b; Andreev, 2000). We used plants and their growth in valleys and plains of Central generalized chronology of the radial increment in pine Asia, i.e., in the forest-steppe ecotone (Dulamsuren et trees reflecting regional variability of growth for al., 2009; Fang et al., 2010). This leads to the vulnera- broad basin of the river Selenga, but a detailed anal- bility of forest-steppe ecosystems to fluctuations in the ysis of influence of local natural and climatic condi- moisture regime during the vegetative season as a tions on local chronologies remained beyond the result of reduced rainfall, as wel as raised evaporation scope of the work. and transpiration due to increasing temperature. An In this regard, we set following goals: improve the increase in the frequency and intensity of drought is statistical reliability of the results and increase the recorded in many regions of Asia within current cli- comparison period of the chronologies of radial incre- matic changes, which explains the migration of the ment with instrumental climatic data by increasing the forest-steppe ecotone in latitudinal and altitudinal sample size (number of measured series of the radial directions (Yatagai and Yasunari, 1995; Dai and Tren- increment per plot), evaluate peculiarities of the berth, 1998; Gunin et al., 1999; Tarasov et al., 2006, increment response to climate factors in the last 2007; Dulamsuren et al., 2014). 20 years by a new sample, examine the spatial In contrast to the global positive trend of tempera- response of the combined chronologies on driving cli- ture, rainfall displays significant spatial variability, matic factors with monthly and 10-day resolution, and especially in regions with complex terrains (e.g., Ped- assess the capabilities of these chronologies for detect- 476 RADIAL INCREMENT DYNAMICS OF SCOTS PINE 477 SSelenginskelenginsk KamenskKamensk BBRN07PRN07P (b) 90 30 (a) 51.951.9°N P Ulan-Ude 108.2108.2°E T ZarechnyiZarechnyi ZZaigraevoaigraevo 20 SSosnovyiosnovyi BBoror 60 C UUlan-Udelan-Ude HTC ° KEY15KEY15 51.851.8°N ZGR15ZGR15 ° ° 10 51.751.7 N 107.6107.6°E 51.851.8 N 30 107.2107.2°E 108.3108.3°E KKEY06PEY06P 0 51.751.7°N KuitunKuitun 0 107.2107.2°E 2 –10 r e JJargalantaargalanta v i R Temperature, Precipitation, mm Precipitation, 1 –20 a g n HTC e GusinoozerskGusinoozersk l e 0 BBaratyaraty SelengaS River –30 GusinoeGusinoe OOzerozero 123456789101112 NovoselenginskNovoselenginsk AH6 TsolgaTsolga HUH15HUH15 CCLG25PLG25P Mukhoshibir’Mukhoshibir’ 90 P 30 50.950.9°N BBRG24PRG24P 51.051.0°N SharaldaiSharaldai Kyakhta ° T 106.1106.1 E 50.950.9°N PodlopatkiPodlopatki 107.1107.1°E 106.1106.1°E HTC 20 HHUR15UR15 PPDL15DL15 MMaletaaleta 60 C 50.750.7°N 50.950.9°N ° 106.5106.5°E 107.1107.1°E 10 30 JJidaida ZAG02PZAG02P 50.750.7°N BuiBui 0 106.5106.5°E BBichuraichura OOkino-Klyuchikino-Klyuchi MMalyialyi 0 KunaleiKunalei 2 –10 Temperature, Temperature, NaushkiNaushki mm Precipitation, 1 –20 KyakhtaKyakhta DendrochronologicalDendrochronological sstationstations iinn 22015015 HTC 50.450.4°N AltanbulagAltanbulag Meteorological stations 0 –30 SukhbaatarSukhbaatar106.4106.4°E BolshayaBolshaya KudraKudra DendrochronologicalDendrochronological sstationstations iinn 11999999 123456789101112 Fig. 1. Study area (a) and climatograms of meteostations Ulan-Ude and Kyakhta (b). Diamonds are climatic stations, triangles are dendrochronological stations in 1999, and circles are dendrochronological stations in 2015. ing long-term fluctuations of moistening in the stud- cover does not exceed 10–15 cm. This leads to the ied region. deep freezing of soil and grounds. The study area is in the zone of insular distribution of the permafrost. To assess the influence of climate on the dynamics MATERIALS AND METHODS of tree growth, we used monthly and daily climatic data Materials for dendroecological studies were col- on the surface air temperature and precipitation from lected in the forest steppe of the Selenga middle meteorological stations Ulan-Ude (1886–2015) and mountains of Western Transbaikalia (Fig. 1a). Kyakhta (1895–2015) (Fig. 1b), as well as moving According to climatic zonation, the study area is in the decadal series calculated by them. Values of the Selyani- temperate continental forest belt of the southwestern nov hydrothermal coefficient (HTC) were calculated subarea of the East Siberian area (Alisov, 1956; Suvo- from May to September by decades and by months and rova et al., 2005). The continental character of the cli- were averaged to obtain seasonal values (Selyaninov, mate is characterized by large daily and annual ampli- 1937). The dynamics of the HTC was compared with tudes of temperatures with severe winters and fairly the SPEI index of dryness for the period from August to July, averaged by geographic coordinates 51.5–52° N hot summers and a small amount and uneven spatio- ° ° ° temporal distribution of precipitation (Zhukov, 1960; 107–108.5 E and 50.5–51 N 106–107.5 E (covering Fadeeva, 1963). The mean annual air temperature is the areas of material collecting) for Ulan-Ude and negative everywhere. The region is characterized by Kyakhta, respectively (https://climexp. knmi.nl, Trouet long (5.5 months) and dry winters, with a mean Janu- and Oldenborgh, 2013). ary temperature of –25.4°C. Winter starts from the Monthly temperature data of Ulan-Ude and middle of October, with steady snow cover in hollows Kyakhta stations show a high correlation among them- appearing after the onset of soil freezing. The amount selves: during the warm period (April–October) r = of winter precipitation falling into hollows from 0.78–0.92; in winter (November–March) r = 0.83– December to February is small (from 10 to 12 mm), and 0.91. Correlations of monthly data for precipitation are the snow falls mainly in the first half of winter. Some much lower: in the warm season r = 0.21–0.45; in open flat areas and slopes remain snowless during the winter r = 0.02–0.24; and for decadal precipitation winter due to the blowing snow by wind and, in gen- amounts correlation between stations is r = 0.20–0.60 eral, even taking into account the accumulation of and r = –0.08–0.36 in warm and cold periods, respec- snow on the bottoms of hollows, the height of the snow tively. Therefore, the temperature field in the study CONTEMPORARY PROBLEMS OF ECOLOGY Vol. 10 No. 5 2017 478 DEMINA et al. Table 1. Localization and description of dendroclimatic stations Code Geographic coordinates, Brief characterization No. of the site elevation above sea level, m, localization of vegetation and growing site 1ZGR51.8° N 108.3° E, 600 m Western gentle slope: 1°–2°. Pine forest on sands. Western slope of Khudanskiy Ridge, Ilka River Different-aged. h ~ 20 m, valley, eastern part of village Zaigraevo Ø ~ 50–60 cm. Dwarf shrubs: 5%, herbaceous cover: 5%. Traces of numerous fires. 2KEY51.7° N 107.2° E, 700 m. Western slope: 20°. Dead cover–lichen pine for- Ivolginskii Raion, 1.5 km south of village est. Different-aged. h ~ 22–24 m, Ø ~ up to 40 Klyuchi cm. No dwarf shrubs, herbaceous cover: 15% (dry cereals), moss and lichen cover: 5% (to 40% in the depression of dry discharge).