RESEARCH METHODOLOGY

3.3.1 RESEARCH AREA

We conducted our study in Zauralsky (Trans-Ural) hilly piedmont province (Russia, the Middle Urals): between 57°00'-57°10'N and 60°10'-60°30'E.

This province includes foothills, which consist of alternating meridional low mountains and ridges with wide, intermountain elongated low lands, in which there are large lakes surrounded by moors (Kolesnikov et al., 1973). The mountains have altitudes of 200-500 m a.s.l. The mountains have soft contours, blunt and broad peaks, while the slopes are long and flat. The climate is moderately cold and humid. The main factors of soil formation in the Urals are mountainous terrain, continental climate, both for ancient and young forming soils, which, combined with a great diversity of vegetation, alters soil characteristics. Mountain soils are characterized by relatively small depth, light mechanical composition (dominated by light and medium loam), different degrees of skeleton (skeletal soil), going up with decreasing soil depth. In the soil distribution of Zauralsky (Trans-Ural) hilly piedmont province of the Middle Urals the dependence on the terrain is clearly visible. The tops and upper thirds of steeper slopes, where the thickness of alluvial soil deposits is least of all, are occupied by shallow, underdeveloped soil with a high degree of skeleton and relatively light texture. Brown nonpod- zolized and podzolized soils are confined to the middle and lower thirds of the gentle slopes. Flat-topped low ridges, gentle slopes, and well-drained downward slopes are occupied with sod-pale-yellow-podzolic soil, which differs in thickness of the soil profile and the degree of podzolization. The soil of smoother slopes, intermountain depressions, and the lows are often characterized by greater depth and moderate skeleton (Ivanova et al., 2000; Ivanova and Zolotova, 2011, 2013).

3.3.2 RESEARCH OBJECTS

All major mountain habitats are included in our study. We climbed to the most-capped mountains. The steep and gentle slopes of the northern, southern, eastern and western exposure were investigated by us. Swamp forests and marshes were not left unattended by us. All forest types were investigated. It is diverse pine and spruce forests.

3.3.3 SAMPLING PROCEDURES

The number of trees on the plot was not less than 200 (Forest Communities Study Methods, 2002). All the trees on the sampling plot were counted; their diameter and height were also measured. The age by the annual rings was identified. Tapes 4 x 20 m were laid for the study of young generations of woody plants. For characteristic shrubs, the projective cover was defined. A total of 10-20 accounting sites with the size of 1 m2 were used to study the productivity of the herbaceous layer. The herbs were cut with scissors near the soil itself and were separated by species, then we dried the samples in a drying cabinet at 105° C to constant weight (absolutely diy). Dried samples were weighed to an accuracy of 0.01 g. We used the calculation method to estimate the biomass of woody plants (Iziumsky, 1972; Usoltsev, 1997). The biomass of needles and leaves is calculated using regression equations, which are obtained taking into account the physiology (pipe model) (Usoltsev, 1997).

3.3.4 DATA ANALYSIS

Ordination charts are constructed using detrended correspondence analysis (DCA). For the numerical analysis of community data, R package vegan [version 2.15.1 (2012-06-22)] (Oksanen, 2006) was used.

RESULTS AND DISCUSSION

  • 3.4.1 IMPACT OF CLIMATIC FACTORS ON FOREST VEGETATION OF URAL MOUNTAINS
  • 3.4.1.1 IMPACT OF CLIMATIC FACTORS ON FOREST BIODIVERSITY

As a result of multiple studies, we described the vegetation of the study area. The data obtained characterize all the main forest types and reflect the diversity of plant communities. Geographic-genetic forest typology was used as the basis for the classification of the obtained descriptions of vegetation (Ivanova and Zolotova, 2014). The analysis showed that the greatest differences in the species structure of forests are associated with a change in the edificator. Two large groups (pine forest and spruce forest) are clearly seen in Figure 3.2.

Various dark coniferous forests are located in Figure 3.2. Forest type No. 11 is waterlogged spmce forests with Siberian pine. This type of forest is spread around lakes, rivers, and swamps. Soil waterlogging can be considered a common occurrence throughout the growing season. The abundance of sphagnum moss is considered a diagnostic feature of this type of dark coniferous forest. The increased diversity of swamp species also distinguishes these forests.

DCA ordination of Trans-Ural hilly piedmont province forests of Ural Mountains

FIGURE 3.2 DCA ordination of Trans-Ural hilly piedmont province forests of Ural Mountains: 1-11, number of forest types.

Dark coniferous forests with a strongly developed grassy layer (forest type number 10) grow in close proximity to the marshes on powerful well- watered soils. Soil is waterlogged at the beginning of the growing season. Herbs form an intensely developed closed tier.

Spruce forests with Oxalis acetosella (forest type number 9) are found at the foot of the mountains, where the slopes are long and very gentle. Deep loamy soils are a characteristic feature of these spruce forests. Moisture conditions can be considered close to optimal; only after melting snow a brief overmoistening is noted.

Pine forests with multispecies herbaceous layer (forest type number 7) grow on the deep and rich soils. A total of 25-30 species of herbs is 1 m2.

Marked 1-6 and 8 forest types formed one group (Fig. 3.2). These forest types are confined to the slopes of different exposure and steepness. The grassy tier under their canopy has a small number of species, the tier is rarely dense and its biomass is much less than in the forest types discussed above.

We conducted a special research to answer the question: what caused the formation of so many different forest communities. The analysis included the study of climatic and soil factors. E. Zolotova (Zolotova, 2013; Ivanova and Zolotova, 2015) has identified factor values on environmental scales (Fig. 3.3). We can judge the strength of a particular factor by its length. According to Figure 3.3, soil factors (nitrogen content) are associated with the axis 1 DCA. The second axis DCA is associated with the climate. Factors listed below are of great importance in the formation of forests. These factors can be interpreted as the main factor determining the type of vegetation.

Effect of climatic factors on the forest differentiation of Ural Mountains

FIGURE 3.3 Effect of climatic factors on the forest differentiation of Ural Mountains: the numbers—number of forest types, HD—moistening, TM—temperature, NT—nitrogen.

3.4.1.2 CHANGE OF VEGETATION IN THE HOLOCENE

To understand the modern dynamics of vegetation, it is useful to consider changes in the Holocene. In former times, the climate of the Urals experienced repeated cyclical fluctuations, sometimes it was much cooler (which led to glaciation), sometimes it was much warmer than at present. These fluctuations were the reasons for serious changes in the species composition and appearance of plant communities (Panova, 2001; Panova et al., 2003; Antipina et al., 2014). The three periods that are the least similar to each other are described in detail for the Ural Mountains (Panova and Antipina, 2016).

  • 3.4.2 IMPACT OF TIMBER HARVESTING AND FIRES ON FOREST VEGETATION OF URAL MOUNTAINS
  • 3.4.2.1 PATTERNS OF REFORESTATION AFTER TIMBER HARVESTING AND FIRES

We studied the natural reforestation in open habitats. The intensity of reforestation has features depending on the disturbance and habitats. We have noticed that the renewal of pine proceeds better on forest burns (Fig. 3.4). However, the intensity of the renewal of Pinus sylvestris decreases rapidly with increasing soil thickness, both after harvest and after fires. Optimal environmental conditions for the emergence of new generations of pines are marked on soils with a thickness of 10-30 cm. About 100-300 thousand copies per hectare are counted in these conditions after fires. The abundance of new generations of pine on deep soils is small both after harvest and after fires.

Effect of soil capacity on the abundance of young growth of Pinus sylvesths in the Ural Mountains

FIGURE 3.4 Effect of soil capacity on the abundance of young growth of Pinus sylvesths in the Ural Mountains: (1) abundance of young growth of Pinus sylvestris after fires, (2) abundance of young growth of Pinus sylvestris after harvesting.

It is also interesting to consider the relationship between different woody species after harvesting and wildfires. Birch is the main competitor for pine. Pine renews better than birch after wildfires. Young growth of Pi nits sylvestris after fires prevails over the young growth of birch on shallow soil (Fig. 3.5). The critical soil capacity (when the number of pine and birch equal) is 65-70 cm. The predominance of young growth of Finns sylvestris after the harvest is possible only in very shallow soils. The critical thickness of soils is 10-20 cm (Fig. 3.6). Therefore, the reforestation after harvesting and wildfires occur differently in different habitats (forest types). Pine forests are restored well both after fires and after felling only on mountain peaks and steep slopes with small gravelly soils. The middle parts of the slopes with gravelly soils of medium capacity are favorable for the restoration of coniferous forests after wildfires. However, harvesting contributes to the spread of secondary birch forests. A rapidly growing birch depresses juvenile pine trees under these habitats on clear cutting. The natural restoration of coniferous forests in the lower parts of slopes with deep soils is difficult. Artificial reforestation is necessary in these growing conditions.

Effect of soil capacity on the abundance of young growth of pine and birch after wildfires in the Ural Mountains

FIGURE 3.5 Effect of soil capacity on the abundance of young growth of pine and birch after wildfires in the Ural Mountains: (1) abundance of young growth of Punts sylvestris, (2) abundance of young growth of Betula pubescens Ehrh. and B. pendula Roth.

Effect of soil capacity on the abundance of young growth of pine and birch after harvesting in the Ural Mountains

FIGURE 3.6 Effect of soil capacity on the abundance of young growth of pine and birch after harvesting in the Ural Mountains: (1) abundance of young growth of Finns sylvestris, (2) abundance of young growth of Betula pubescens Ehrh. and B. pendula Roth.

3.4.2.2 COMPARISON OF PRODUCTIVITY AND DIVERSITY OF HERBACEOUS SPECIES IN FORESTS AND CLEAR CUTTING

The lower parts of the slopes with deep soils, which provide a stable regime of moisture supply, are characterized by a complex and diverse vegetation dynamics. Forests dominated by Siberian spruce are recognized as indigenous ecosystems in the area (Fig. 3.7). The fire centers practically do not meet in these conditions. However, harvesting leads to an extreme variety of derived ecosystems. Great changes affect all tiers of forest vegetation. The grassy layer reacts first to external disturbances. The exploration included the dark coniferous forest and two variants of birch forests (with thick spruce undergrowth and rare spruce undergrowth). Also studied was the meadow hayfields. The forest was cut down 67 years ago.

Ural dark coniferous forest, under the canopy of which is dominated by a continuous cover of Oxalis acetosella

FIGURE 3.7 Ural dark coniferous forest, under the canopy of which is dominated by a continuous cover of Oxalis acetosella.

The main data on the structure of the studied communities are given in Table 3.1. The forest disturbances studied changed to a greater degree the productivity of plant species. Changes of each species are specific (Table 3.2).

The plant species that dominated the climax spruce were most severely affected after the disturbances. The opposite trend was revealed for some plant species that were found in the spruce forest in small quantities (Table 3.2).

In order to understand the mechanisms of change, we investigated the age structure of the Siberian spruce populations. Studies have shown that a generation over 67 years old prevailed. Thus, a new generation of Siberian spruce appeared in the dark coniferous forest and young trees were able to survive during the felling. The study of the vitality of the renewal of Siberian spruce showed that almost all young specimens have a good vertical growth. Thus, the younger generations of coniferous plants, which were preserved in the process of logging, determined the direction of reforestation.

TABLE 3.1 Studied Plant Communities Formed After Clear Cutting in One Type of Climax Forest.

Sign

Dark coniferous forest

Spruce-birch

forest

Birch

forest

Forest

meadow

Characteristics of the tree layer

Average, maximum age of trees, years

180,220

65,67

65,67

Average height, m Characteristics of the soil

26.3

24.2

20.4

Litter thickness, cm

3.9

2.1

2.2

1.9

Average soil depth, cm

120-130

93-97

145-155

93-105

Yung generations of Picea obovata

Number, thousand copies/ha

+

4.02

0.51

+

Predominant height, m

0.12-0.49

4.7-9.9

1.9-6.9

-

Yung generations of Pimis sylvesths

Number, thousand copies/ha

-

-

-

+

Predominant height, m

-

-

-

0.09-0.33

Characteristics of herb

Diversity

24

22

45

57

Average height, cm

6.9

6.9

48.5

60.1

Aboveground biomass (g'in2 in absolutely dry state)/

Variation coefficient, %

  • 17.7
  • 33.23
  • 4.4
  • 66.21
  • 100.9
  • 7.03
  • 280.6
  • 7.72

To summarize, logging leads to the emergence of a multitude of plant communities within one climax forest. Recovery shifts come at varying speeds. The convergence of the structure of secondary and climax ecosystems occurs slowly. The results of this research are fundamental to understanding the evolution of modem ecosystems under anthropogenic impact and climate change.

 
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