The forest tree mechanism to response to atmospheric drought and soil is poorly known, especially in relation to carbon allocation, how the trees modified their architecture above and below ground in response to variations in climate conditions. Pinus sylvestris var. mongolica is the most extensive conifer as it can be spread throughout Eurasia as on the western Mediterranean to the Russian Far East. Such huge distribution includes a wide array of climates, with the severe and frequent summer drought of southern Iberian Peninsula and extremely cold winters of north eastern Siberia [1]. World climate conditions are placing greater pressure on forests ecosystems from almost all over the globe [2]. In case of Scots pine, growth can be endorsed by increased temperature in northern and upper areas where production is basically cold-limited [3] [4]. However, there is most evidence that indicates Scots pine growth is also influenced in cold constrained sited due to aggravated soil moisture deficit which linked to increasing demand for evapotranspiration or decreased in precipitation during growing season [5] [6]. Such contrasting influence of minimum temperature and drought brings uncertainty about productivity and vigor of species throughout the range and specifically in cold-dry environment [7], besides other dry environments, particularly warmer areas of Mediterranean, where scots pine also subjected to winter and warm climate [8].

In this consideration, the comparison of low temperature (i.e., Siberian forest-steppe) and warm climate (i.e., Mediterranean mountains) has a simultaneous effect on Scots pine growth which is of particular interest to predict the climate change influences on conifer species [9]. A variety of range of methodological approaches are used to determine tree growth climate relations, but dendroclimatological techniques are valuable in determining long term variations in forest productivity in perspective of climate relationship with variables like precipitations and warmer temperature [10].

Mongolian Scots pine (Pinus sylvestris var. mongolica), an environmental diversity of Scots pine, is naturally dispersed in the Daxing’anling mountains of China (>50˚10_ - 53˚33_N, 121˚11_ - 127˚10_E), in Honghuaerji of the Hulunbeier sandy plains of China (47˚35_ - 48˚36_N, 118˚58_ - 120˚32_E) and parts of Russia and Mongolia (46˚30_ - 53˚59_N, 118˚00_ - 130˚08_E) (Zhu et al., 2008; Zheng et al., 2012). As of its strong nature and ability to tolerate dry environment, so in 1950 it is first time introduced to condense wind speed and increase sand fixation in the Zhanggutai region, the south east sandy land. So, it becomes the most important specie for reforestation in north east China [11] [12]. Tree rings are widely used to evaluate the climate variation effects on forests [13]. Most dendrochronological studies focus on radial growth patterns to infer the long-term variations in tree performance. There is a remarkable expansion in desertification across Mongolia due to climate warming at global scale, and it has potential influence on Mongolian environmental health and economy conditions in current years. So Mongolian government has applied reforestation plans. Pinus sylvestris L. mongolica has a significant role in ecology and Mongolian economy [14] [15].

The objective of this study was to measure the climate influence on long term changes in tree radial growth, to investigate tree survival in drought conditions, and to check the influence of diurnal temperature and potential vapor pressure effects on tree growth. It is anticipated that the results of this study might be useful for management of forest plantation with respect to growth conditions of Pinus Sylvestris L. mongolica.

When building up a large chronology it is most important to reminisce the fluctuation in growth with the climate conditions in chronology when large area being summarized by different growing conditions. The Daxing’an mountains tree chronologies along 3-elevations have various ranging gradients, its highest peak range 2035-meters. It was formed about 200 - 145 million years ago. The site information is given in Table 1. Figure 2 indicates the spatiotemporal variations and drought patterns in Daxing’an mountains and north inner Mongolia. The relevant chronology and statistic information’s are listed in Table 2. Figure 3 represents the tree growth of Pinus Sylvestris var. mongolica from 1901-2016. We clearly observed variations in growth trends there is a significant increase in growth 1920-1930 and then decline in curve 2^nd growth increase interval from 1991-2001. Figure 4 represents the growth trend of Pinus Sylvestrisvar. mongolica. We divide it into 3-periods 1921-1952, 1953-1984, 1985-2016. There is an obvious increase in growth trend during 1925 in Mg site in Figure 4(A) and

1952 period at Nm site in Figure 4(C). During 1975-1980 increasing trend of growth for MG and Kyh in Figure 4 (B) but decline in growth trend at Nm site.

Figure 5 we explain the scatter plot with diurnal temperature of summer and winter seasons and we use growth trends to indicate the growth rate at 3-sites.

Letter a’ and c’ represents the significance level between groups.

There is an obvious difference at Kyh site between winter and summer season and growth trends in summer season there is growth trend first remain stable then start to decline but in winter season there is an obvious increase in growth. at Mg site also increase in trend in winter diurnal temperature. at Nm site its growth remains stable in winter season. In Figure 6, we measured diameter at breast height along elevation latitude at 3-sites Mg, Kyh, Nm.

Scots pine is an under the effects of drought stress and considered to be a drought tolerant, so it is thought to be a main climate limiting factors which reduce its growth in semi humid and semi-arid regions such as in Mongolian Plateau Daxing’an Mountains [21] [22] [23]. In previous studies, it also suggests that radial growth of scots pine is influenced by humidity, precipitation in these regions, and most of dendroclimatic studies based on reconstruction of hydroclimatic history [21] [24]. In these areas’ radial growth for growing season mostly in July-September as in Figure 1. On the other hand, a significant increase in radial growth of non-growing season due to temperature also observed. It is probable protect of dormant buds in winter high temperature from frost damage [25]. The positive growth response with spring temperature could be due to early snow melting process, which supply the early spring water, and eventual tree growth rate stimulated [26] [27]. This infrequent drought response relatively due to humid climate and might be northern study site, where positive effect is strongly greater than negative effect [28]. Similar drought response also visible in most of reconstruction studies in Qilian Mountains (Sun and Liu, 2013) and also same case of drought stress in western Tian Shan Mountain, China [29].

Scots pine usually has usually typical drought response patterns, it shows positive response to precipitation and negative response to temperature increasing [21] [22]. Actually, this typical response to drought patterns also found in other drought or wetness tree ring analysis in other studies [30] [31]. In this study correlation between tree ring index and diurnal (Maximum-Minimum) temperature it clearly indicates that summer temperature shows negative or decline in growth response and winter temperature indicates the positive growth response in Figure 4. A significant positive growth response in winter temperature supported moisture as the main limiting factor for Pinus Sylvestris growth. The climate (drought) response also observed in Dahurian larch a most important conifer specie in this area [32]. Late summer temperature influence on nutrient storage capacity which affects the sprouting in next spring. This alternatively affects the growing ratio of sprouting and tree ring dimeter in next year’s [33]. The results of the analysis revealed that Pinus Sylvestris revealed the consistent increase in growth pattern in moist conditions. These relationships recommended that specific drivers which affect variation in dry-wet conditions in Daxing’an mountains. Among these differences the most prominent differences in Daxing’an mountain in central Mongolia. Similar studies were investigated by [34] which reported that different patterns of dry and wet conditions under global warming using models and observations. [35] found that increase in moisture related to quick warming. Though the reasons for divergence should be further studied, it might be associated to the diverse response to phase shift [36] [37].

Drought severity conditions most obvious during 1920-1930 in Daxing’an Mountains rather than other areas. In addition, most of growth series indicates that Daxing’an Mountain has gotten more warm and wet since the late 1970s. This is not only the case of Daxing’an Mountain especially in all transit zones. Our results may be not accurate due to in-adequate spatiotemporal distribution of tree ring data collection in this area. Overall, drought inconsistency in Daxing’an mountains and its consequential affects on surrounding areas due to climate oscillations of the Atlantic and Pacific oceans (e.g., AMO, NAO, PDO, and SNAO ENSO). These climate oscillations at large scale occur due to variations in Asian monsoon and lead to dry and wet fluctuations in the Daxing’an mountains.

This work was supported by the National Key Research and Development Program of China (2016YFA0600800), the National Natural Science Foundation of China (41877426), the Fundamental Research Funds for the Central Universities (2572019CP15), and the Open Fund of Ecological-Meteorological Innovation Laboratory of China Meteorological Administration (stqx2018zd02). We thank Jinsheng Han, Zhenjing Sun and Zecheng Chen for their help in sampling. We also thank the staff of the sampled Forestry Bureaus for their assistance in the field.

The authors declare no conflicts of interest regarding the publication of this paper.

Yasmeen, S., Perveen, F. and Ullah, I. (2019) Climate Factors of Vapour Pressure and Diurnal Temperature Influenced on Radial Growth of Scots Pine in Northeastern Mongolia. Open Journal of Ecology, 9, 401-412. https://doi.org/10.4236/oje.2019.99026