The five Central Asian states are closely interlinked by sharing the rivers Syr Darya, Amu Darya and other transboundary rivers. Water-rich countries, Tajikistan and Kyrgyzstan located upstream, rely to a large extent on hydropower for energy production. Water-poor countries, Kazakhstan, Uzbekistan and Turkmenistan, located downstream, use the water for agricultural land. Most of the water in the region is generated in upstream mountain areas. Climatic and soil conditions in Kazakhstan are unfavourable for the growth of trees and shrubs over most of its territory. This is the reason for the formation of forests in the country, especially in the desert, in the form of narrow intermittent strips along rivers. For the country with limited forest resources, it is important to preserve the existing forests in the arid regions of Kazakhstan. Riparian afforestation in the arid and dry southern and south-eastern regions of the country and the conservation, improvement and regeneration of all riparian forests is a very important issue in the forestry sector, with riparian forests being poorly studied.
Given the great importance and diversity of riverine forests in the country's forestry sector, special attention should be paid to studying their characteristics in order to improve the productivity, the composition and longevity of these trees. The republic's riparian forests naturally serve as protective water belts that protect, regulate and store water. Undoubtedly, they have an impact on the climatic conditions of the areas where they are located, improving the microclimate, increasing the humidity and reducing the strength of dry hot winds. It also reduces water evaporation and contributes to the conservation and purity of the river's water resources. Compared to mountain forests, riparian forests have a significant impact on the local microclimate [11]. Riparian forest vegetation on the riverbanks strengthens the banks of the river and protects them from erosion, slowing down the river flow, especially during strong spring floods. At the same time, it reduces the strength of summer winds, decreases evaporation of excess water and reduces dryness. Many valuable species of animals and birds find favourable conditions for survival in riparian forests. The amount of riparian forests in Kazakhstan is relatively small. As 70% of the country is arid and dry, the number of rivers and lakes is extremely small. Their water volume is also very low. Due to the limited water resources of many of the country's rivers, there are no riparian forests on their banks, or they occur as small scattered islands or small areas with narrow strips. The main reason for the loss of riparian forests is the reduction of rivers and lakes. A reduction in the amount of river water, in turn, affects groundwater and disrupts the balance. Excessive use of water resources for cultivation of crops, human needs (hydropower, daily use). Anthropogenic factors disrupt the centuries-old natural balance of forests. At the same time, the volume of riparian forests is decreasing as a result of human activities such as the mass cutting of trees and shrubs for firewood, fires, mass ploughing and irregular cultivation of agricultural lands along riverbanks, cattle grazing and haymaking. The cutting of riparian forests continues. Therefore, an issue of conservation and restoration of riparian forests in all river valleys is currently being addressed. In general, the species composition of riparian forests in Kazakhstan is very small and poor. It should be noted that the composition of riparian forests consists mainly of representatives of the families Salicaceae and Eleagnaceae [11].
The nature of Kazakhstan is attractive because of its uniqueness and diversity of landscapes. Every corner has its own characteristics. As for the Almaty region, it covers all natural zones of the country, from sandy flat deserts to high mountain peaks and permafrost. There are specially formed and preserved relict trees among the varied landscapes. There are species of trees that grew naturally in this area before the Ice Age, and have survived ever since, and one can only imagine them. This tree species grows only under natural conditions on the banks of the Charyn River – Fraxinus sogdiana bunge, a Sogdian ash tree. There are many names for this species of ash (Sogdian, water-loving, river ash, Charyn, Syr Darya, Turkestan). In the wild, the Sogdian ash is found only along the Charyn River in the Almaty region of the Republic of Kazakhstan, i.e. in the lower reaches of the river below the canyons.
At the area where the fraxinus sogdiana is located, the canyons narrow and move away from the river. In other parts of the country, the species does not grow at all. This species of chagan grows from the headwaters of the mountainous Temirlik River, which flows into the Charyn River and originates from the Ketpen Ranges, to the sand dunes at the confluence of the Charyn and Ili Rivers. This is a distance of about 40 km. Due to its moisture-loving nature, this tree species cannot grow on the sandy soils of arid regions. Sogdian ash trees along the Ili River are not found at all. This species does not grow in the canyons of the upper Charyn River. Fraxinus sogdiana, which grows in the river valleys of the Karatau ranges, is not the first high-altitude stratum of this species. This species of ash is not found in other parts of the world. Fraxinus sogdiana is on the verge of extinction [12]. The geographical distance from the nearest chagan type to the Karatau Ranges is 750 km. The Sogdian ash forest on the Charyn River is a geographically isolated species. In terms of its geographical landscape, the canyon is located in a deep hollow in the desert-steppe zone, where the plants growing here form an isolated population. Due to the influence of the Charyn River, the humidity in the forest increases and there are no severe frosts here [13]. Although Sogdian ash forests have been planted on Terrace-2 since 1939, the area under cultivation is less than 30%. This is due to the fact that these seedlings will dry out quickly if they do not receive regular moistening. As its name suggests, this tree cannot survive without water. Other species of ash cannot compare to the fraxinus sogdiana in terms of moisture-loving properties. In the steppe zone of southern Ukraine and Russia, the Pennsylvanian ash is much more widely planted than the common ash, let alone the Sogdian ash, as it is more drought-resistant. It is very popular because of its good form and resistance to disease (including industrial gassing) [14].
Currently, no afforestation of fraxinus sogdiana trees is taking place in the Charyn State National Nature Park. Conceptually, all the forest protection strips created are in a neglected state, no maintenance work is carried out, and this is one of the main activities for growing sustainable, long-lasting plantations. Other necessary forestry measures are also not implemented, which has an immediate impact on the condition of the plantations. If these plantations are allowed to die today, it will cost more to restore them than to maintain them. For the Charyn grove, the lack of land improvement works is due to the fact that since the construction of the Moynak Hydroelectric Power Station (HPS), there has been a shortage of irrigation water due to a decrease in water volume. At the same time, canals built during the Soviet era are now covered with earth and stones and are unusable. If the republic's authorities do not pay attention to the restoration of these canals and ditches, the national park administration alone will not be able to cope with it, either financially or physically. Therefore, the study of natural regeneration of fraxinus sogdiana is considered an essential way of conserving riparian forests and is of high practical significance. Tugai is considered an "oasis" located in the arid-desert zone of the republic, and its preservation is an urgent task not only for the national park staff, but also for foresters throughout the country [11]. Although ash seeds ripen in August-September, they are unevenly distributed. In some years, the seed material is stored on the tree for a year and then flies off into the lowlands the following year due to strong winds. Spring melted snow and river water are stored in the lowlands for several days to weeks. After the water has dried up, well-restored shoots of fraxinus sogdiana grow in the lowlands. Such trees usually have a high growth rate [15]. Fraxinus sogdian is also resistant to soil salinity, e.g. it can grow in soils with sulphate and chloride salts.
Based on the methods described in the "main research stage" section of the Materials and Methods chapter, the practical part of the study was carried out. After counting the number of seedlings and young shoots in each calculation area, these were added up, the mathematical average for the age groups was determined and recalculated to 1.0 ha. The calculation of 1 ha of natural regeneration in the reference area is made using the following formula:
$$\text{N}=\frac{\text{n}\times 10000}{\text{Р}}$$
1
where N is the number of seedlings and young shoots per 1 ha; n is the number of seedlings and young shoots on all survey plots; the area of all survey plots is P2 m2. Thus, according to the "Regulations for the taxation of forests in Kazakhstan" the state of natural regeneration in forests with a reference area is determined by the calculation method. The result of the calculation is shown in Table 1:
Table 1
Assessment scale for natural regeneration of fraxinus sogdian on the Charyn forest estate (number of reliable seedlings) thousand pcs / ha
|
Assessment of natural regeneration
|
Age groups of undergrowth
(years)
|
Total number of young shoots aged 11–15 years
|
|
2–5
|
6–10
|
11–15
|
|
Good
|
3,0 or more
|
2,0 or more
|
1.0 or more
|
3.0 or more
|
|
Satisfactory
|
1.5-3.0
|
1.0–2.0
|
0.5-1.0
|
1.5-3.0
|
|
Bad
|
1.5 or more
|
1.0 or more
|
0.5 or more
|
1.5 or more
|
To determine the total number of young shoots, the following correction factor was used:
a) for the age group of 2–5 years – 0.3;
b) for the age group of 6–10 years – 0.5;
c) for the age group of 11–15 years – 1.0.
According to the seed and seedling evaluation methodology of V. Kapper, evaluation of fruiting is carried out on a temporary reference plot of 0.1–0.5 ha (the number of trees on the reference plot does not exceed 100) [9]. According to the results of the 2020 assessment, when visually inspecting seed yield along the Charyn River, the level corresponded to a six-point scale of O.G. Kapper, the seeds were very poor and sparse, with some trees giving seedlings in the open air. This leads to the presumption that natural regeneration will be low next year due to the small number of seeds this year. And last year, 2019, the seed level was high, corresponding to a score of 4 on the Kapper scale. Thanks to this, natural regeneration yielded good results in 2021. But the main factor affecting natural regeneration is changes in water levels in the Charyn River. Water levels in the Charyn River have been low this year due to the drought. The peculiarities of forest growth and development in the forests on the Charyn River bank have been reflected in the studies of many scholars [9; 11; 13; 15]. Many of them noted that the condition of the forests and the nature of their changes were clearly influenced by the hydrological regime of the Charyn River. Due to the construction of the Moynak hydroelectric power station, the growth and development of trees and shrubs in the forest will undergo numerous changes. Changes in water supply play a key role in the natural regeneration of the fraxinus sogdian tree.
Table 2
Assessment of natural regeneration of fraxinus sogdian on the bank of the Charyn River (number of germinating seedlings) at the rate of 1 thousand. Pcs. Per 1 ha.
|
No. of the monitoring plot
|
No. of the plot being assessed
|
Plot area, m2
|
Number of germinating shoots depending on tree age
|
Total number in the study area, thousand pcs.
|
Total number of young shoots aged 11–15 years, thousand pcs.
|
|
2–5 years
|
6–10
years
|
11–15
years
|
|
1
|
5
|
4.0
|
3.02
|
2.05
|
1.02
|
6.09
|
3.04
|
|
2
|
23
|
3.0
|
2.04
|
1.45
|
0.72
|
4.21
|
2.11
|
|
3
|
43
|
5.2
|
1.31
|
0.71
|
0.43
|
2.45
|
1.22
|
|
4
|
6
|
4.3
|
3.05
|
2.11
|
1.04
|
6.2
|
3.10
|
|
5
|
24
|
4.0
|
2.10
|
1.56
|
0.81
|
4.47
|
2.23
|
|
6
|
46
|
3.0
|
1.42
|
0.78
|
0.48
|
2.68
|
1.34
|
In the course of the study, the authors divided the grove into three parts: the lower part of the grove, the middle part and the upper one. To read Table 2, it should be noted that in the lower part of the grove there were monitoring plots No. 1 and No. 4 where natural regeneration showed good results. From the calculated data in the Table, one can see that there are 3.040 seedlings per ha of naturally regenerated viable seedlings in control plot No. 1 and 3.100 seedlings in control plot No. 4, respectively. The middle part of the grove has worse indicators than those for the lower part. In this case the data obtained is that there are 2.110 seedlings per ha of naturally regenerated viable seedlings in control plot No. 2 and 2.230 seedlings in control plot No. 5, respectively. In the upper part of the grove, natural regeneration rates are very low and here, there are only 1.220 seedlings per ha in control plot No. 3 and 1.340 seedlings per ha in control plot No. 6, respectively. The results of the field studies were compared with the data from the Sogdian ash tree natural regeneration assessment scale. The comparative analysis reveals that the natural regeneration of monitoring sites No. 1 and No. 4 can be assessed as "good", while the natural regeneration of monitoring sites No. 2 and No. 5 can be assessed as "satisfactory" and the natural regeneration of monitoring sites No. 3 and No. 6 – as "poor".
The main threats to the natural regeneration of ash trees and the preservation of current tree stands include the reduction and degradation of forest ecosystem diversity, increasing economic market activity, drought and desertification, together with increasing risks of forest fires. For partially or totally endangered trees in Kazakhstan, the status of existing genetic reserves is clarified annually and measures are taken to maintain the conservation regime in these areas [12]. All in situ conservation objects are under state control. The direct protection of species is carried out by government agencies. To reduce the destruction risks of fraxinus sogdian, continuous monitoring of its condition is necessary.
The research data described in the book "High altitude flora and vegetation of Kazakhstan and the effects of climate change" [16] indicate that the vegetation of mountain systems has undergone reconstruction. The decrease in the values of SAVI (soil-adjusted vegetation index) is probably due to the aridisation of ecosystems, leading to a decrease in the number of some species, a decrease in the percentage ratio of vegetation cover to biomass. Rare, endemic and endangered plants, as well as plants and biocenoses with a small range appear to be particularly vulnerable to the adverse effects of climate change against a background of general xerophytisation of the vegetation cover. Analysing these results and conclusions in relation to the subject of the study, the authors reaffirm the imperative need to maintain water balance (irrigation systems and canals) to preserve the relic grove of Sogdian ash trees in the Charyn River valley.
Today, the republic uses traditional methods of plant propagation – seed and vegetative propagation. However, these methods have very serious drawbacks. For most species, and above all for tree species, the problem of reproduction, despite intensive scientific research in this area, remains to be solved. The development and introduction into the forestry of the Republic of Kazakhstan of fundamentally new methods and techniques of propagating deciduous and coniferous tree species, shrubs and flowers, based on modern methods of agricultural biotechnology, is of great importance in the successful solution of these directions. The measures to provide forest cultivation works with planting material with improved hereditary qualities and continuation of works on formation of a permanent forest seed base are carried out by the Republican State Enterprise "Republican Forest Selection Centre" [17]. Genetic and biotechnological enhancement of species is a scientific breakthrough that has made it possible to preserve endangered species and improve their viability and quality characteristics. Genome-wide detection of candidate genes for functional traits within a species usually involves sequencing large samples of phenotyped individuals or linkage analysis across several generations. Sometimes a more effective approach may be to identify genes by detecting amino acid residues shared by species possessing the trait. For common ash and Pennsylvanian ash trees, similar studies are carried out in order to increase resistance to ash borer [18].
For the purposes of the study, it is also worth highlighting the prospects of working on the artificial breeding of fraxinus sogdian trees with greater drought tolerance. Furthermore, obtaining more viable seedlings in large numbers will enable them to be planted in the territory of the Charyn Nature Reserve and possibly in other areas. The emerald ash borer, Agrilus planipennis, native to East Asia, is an invasive pest of ash trees in North America and European Russia. This quarantine species poses a threat to ash trees across Europe. A survey in ten regions of European Russia in 2019–2020 showed that the emerald ash borer has spread faster and further than previously thought. New infested areas were found for the first time in St Petersburg (110–120 km from the EU border: Estonia, Finland) and in the Astrakhan region (50 km from the border with Kazakhstan). It is possible that new enclaves may appear in cities in Eastern Europe and Kazakhstan, far from the current known range. All previously known infestations in the European part of Russia occurred on green ash (Fraxinus pennsylvanica), which was introduced from North America, and individual trees of European ash (F. excelsior) [19]. But it is possible that, over time, this parasite species will also invade local species as new areas are developed and food becomes scarce. The borer has a significant impact on the condition of current tree stands, and weakened trees produce poor quality seeds, which will negatively affect the level of natural regeneration. To address the problem of biological protection of ash trees against borers, three species of parasitic insects have been studied and started to be produced in the USA [20]. Moreover, ash tree mortality caused by Hymenoscyphus fraxineus is currently an acute problem in Europe. Among the possible routes of invasion of the fungus into Europe from its natural range in easternmost Asia, movement along the inextricable Eurasian ash species habitat chain cannot be ignored. In Estonia, a species of ash tree, Fraxinus sogdiana, naturally growing in Central Asia, was found to be susceptible to H. Fraxineus [21; 22]. Thus, for Sogdian ash trees, the development of prevention and protection methods against species-specific entomoparasites and fungi is also relevant.
Continuing to talk about the possibilities of genetics, interspecific hybridisation can take advantage of heterosis and most widely combine dual parental traits and is an effective strategy for improving species and stress-resistant cross-pollinated tree selection. Species of Fraxinus L. are important for landscaping, sawn timber and woody plantations. For instance, China has solved the problems of poor cold adaptation associated with the introduction of Fraxinus sogdiana to Maoershan (Heilongjiang Province, north-eastern China), improved the pest resistance of Fraxinus mandshurica, and also took advantage of the characteristics of F. mandshurica and F. sogdiana by performing their interspecific hybridisation [23].