Vital state of plantings along Karl Liebknecht Street in Yoshkar-Ola

Mukhametova Svetlana Valeryevna ORCID: 0000-0001-7892-6450 PhD in Agriculture Associate Professor; Department of Horticultural Engineering, Botany and Dendrology; Volga State University of Technology 424000, Russia, Republic of Mari El, Yoshkar-Ola, Lenin Square, 3, room 245 MuhametovaSV@volgatech.net Other publications by this author     Kurnenkova Irina Pavlovna PhD in Agriculture Associate Professor; Department of Ecology, Soil Science and Environmental Management; Volga State Technological University 3 Lenin Square, room 302, Yoshkar-Ola, Mari El Republic, 424000, Russia KurninkovaIP@volgatech.net Other publications by this author

Ignatova Ol'ga Ivanovna Master's degree; Department of Horticultural Engineering, Botany and Dendrology; Volga State Technological University Master of Industrial Training; Mari Forestry College 424000, Russia, Republic of Mari El, Yoshkar-Ola, Lenin Square, 3, room 245 ignatovaoi32@icloud.com

Introduction. The city's road network is a source of noise, dust, and exhaust fumes. Street greening is a means of improving the urban environment and is of great ecological importance. Trees and shrubs improve microclimatic conditions, regulate the gas composition of the air, protect residential areas from noise, and emit phytoncides that inhibit the growth and development of microorganisms. In addition, green spaces decorate the streets, complement the architecture of buildings and structures, and help to create an attractive appearance of the city ^[1]. However, anthropogenic stress in an urban environment can lead to a violation of the morphological and biological characteristics of plants, which leads to a decrease in their vital condition, deterioration of decorative effect and decrease in the stability of plantings in general, and the development of foci of pathogens and pests. Improving the maintenance conditions of green spaces, including the demolition of overstocked, wind-blown and diseased trees, is becoming increasingly important ^[2]. Improper and untimely care of plantings affects the vital condition of woody and shrubby vegetation ^[3].

Ordinary outdoor plantings are strongly depressed by soil compaction with violation of water-air, salt and temperature conditions, depletion of nutrients, contamination with lead and other substances such as sulfur dioxide, nitrogen oxide, carbon monoxide, hydrocarbons, etc. Photosynthesis is reduced due to the smaller surface area of the assimilation apparatus, respiration is increased, there is a lack of soil moisture, accompanied by increased dryness of the air and overheating of the dusty foliage ^[4]. The correct choice of woody plants for landscaping is closely related to the study of their biological characteristics. With proper application, it is possible to create plantings that fully fulfill their protective and aesthetic functions ^[5]. The ability of a green infrastructure to benefit depends on the choice of plant species and their combinations ^[6]. The introduction of maximum species diversity is one of the solutions contributing to the optimization of the urban green space system ^[7]. One of the main tasks to increase the sustainability of woody plants in the urban environment is to carry out surveillance measures, but in many cities, monitoring of the sanitary condition of green spaces is practically not carried out ^[5]. Thus, assessing the viability of urban plantings is an urgent task.

The city of Yoshkar-Ola is a multifunctional city, the ecological situation in its districts is heterogeneous and depends on emissions from stationary sources of pollution and, in many respects, motor transport ^[8]. One of the main streets of regional importance is Karl Liebknecht Street, which is located in the left–bank part of the city, has a meridional direction, with a length of about 3 km. This street is one of the important transport lines of the city and is characterized by a high anthropogenic load. Thus, in 2016 Karl Liebknecht Street became one of the city streets with the maximum concentration of carbon dioxide in the atmospheric air (0.04% vol.d.), the maximum value of the radioactive background (0.14–0.15 µSv/h, within the natural background) and a high concentration of sulfur dioxide (0.03 mg/m3, does not exceed MPC 0.5 mg/m3) ^[8]. Thus, the study of the sanitary condition of the street plantings is relevant. Previously, we analyzed the assortment of woody plants growing on this street ^[9].

The purpose of this study is to analyze the vital condition of woody plants growing along K. Liebknecht Street in the landscaping strips along the roadway.

Research methodology. The study was conducted in August 2024. The sanitary condition was assessed on a 5-point scale given in the Rules of Sanitary Safety in Forests (2020): 1 – healthy (without signs of weakening), 2 – weakened, 3 – severely weakened, 4 – shrinking, 5 – dead. For each species/genus, the coefficient of its condition was calculated as the arithmetic mean of the plant scores of this taxon. The coefficient of the condition of the plantings of the street as a whole (KO) is calculated as the arithmetic mean of the coefficients of the condition of individual species / genera of trees. When assessing the condition of plantings, the following scale was used: Co < 1.5 – healthy plantings, without signs of weakening; 1.51 – 2.5 – weakened; 2.51 – 3.5 – severely weakened; 3.51 – 4.5 – shrinking; > 4.5 – dead plantings ^{[10, 11]}.

Research results and discussion. The number of plants by category of vital condition is shown in Table 1. The main part of the plants (922 specimens, 87%) belongs to the second category, i.e. it is characterized by a weakened state. The category of severely weakened plantings includes 9% of plants, drying out – 1%, dead – 3%. Not a single plant was classified as healthy in the first category, as all showed signs of weakening, the presence of diseases and pests. In general, the living condition of the plantings along K. Liebknecht Street is assessed as weakened, which indicates a good environmental situation at this facility.

Table 1 – The vital condition of woody plants along Karl Liebknecht Street

Note: * – running meters of the hedge. When combined with the number of copies, 1 square meter of hedge is conditionally accepted as 1 copy.

Among the examined plants, birch trees have the lowest coefficient of health (2.6 – severely weakened), which is due to the presence of 14 dead specimens among 141 existing plants. Dry trees in street plantings are unacceptable and must be removed to prevent various emergencies, but unfortunately this does not always happen not only in our city ^[3]. Without taking into account the shrunken trees, the condition coefficient of birch is 2.1, i.e. the remaining living specimens are characterized by a weakened state. The most common damage to birch trunks is twig holes in various stages of development, which were formed as a result of the cutting of large branches (Figure 1a). 66 birch trees, which makes up 47% of their total number, have dead wood formed as a result of mechanical action (Figure 2). According to our observations, such damage occurs due to injury to trunks by vehicles, including in winter when clearing snow from the territory, as well as improper compliance with pruning technology, when bark breaks or branches break. A comparison of the category of plant condition with the presence of dried fruits on them showed that among 87 specimens. The second category has 27 copies of this trunk defect. (31 %), among 39 copies. the third category – 29 copies (74 %), among 14 copies. fifth category – 10 copies. (71 %). First of all, large dry trees are more dangerous, which not only are the site of infection pathogens, but also violate the mechanical strength of the trunk, lead to severe plant oppression up to death. According to researchers ^[12], birch can be susceptible to wind and windbreak, which is caused by the development of root and stem rot, and indirect signs of rot, along with dry wood, are frost cracks, structural anomalies, etc. In our study, 8 individuals had Various growths were found on birch trees (6%), and frost and thunderstorm cracks were found in 20 specimens (14%) (Figures 1b, 1b).

It is important to note that of the 141 copies available throughout the street. birch trees 90 pieces. They are being pruned because they are located near power lines (Figure 3). Such forced pruning not only spoils the appearance of trees, but also reduces their sanitary condition. It is known that white-trunked birches are valued for their high, slender crown with long, falling branches, and heavy pruning distorts this shape, changes its structure and aesthetics, causes curvature and unnatural thickening of the branches, gives an unnatural appearance to the tree, reducing its decorative value. In the pruning area, twigs and trunk hollows, tobacco knots, closed and open shoots, growths form, multi-tops form, rot develops from wood-destroying fungi, and branches shrink. Large wounds do not heal and dry out for a long time, fungal spores quickly penetrate through them, and wood is easy to rot. The presence of shrunken trees on the surveyed street indicates that birch trees do not respond well to heavy pruning (Figure 4). The way out of this situation is seen in the future replacement of shrinking birch plantations placed under wires with other, shorter species. But it is impossible to completely abandon the use of birch trees on the streets, because without them the plantings "darken". So it is necessary to carefully approach the choice of planting sites for such large plants as birches, so that they can fully display their decorative and environmental-improving qualities.

a b c

Figure 1 – Damage to birch trunks: a) the initial stage of a knotty hollow; b) an outgrowth; c) a frost crack with fruit bodies of saprotrophic fungi

a b c

Figure 2 – dryness on birch trunks caused by the mechanical action of vehicles: a) traces of the vital activity of stem pests, basal hollow, core rot, visible twisting of the wood; b) the beginning of core rot, c) small size, does not cause severe oppression of the tree.

a b c

Figure 3 – Consequences of birch pruning: a) sap flow, drying of part of the branches; b) drying of the main part of the crown; c) the onset of core rot, traces of vital activity of stem pests by large-scale cutting

a b

Figure 4 – Dead birch specimens: a) shrinkage as a result of pruning; b) through hollow along the entire length of the trunk

The worst condition on K. Liebknecht Street is characterized by mountain ash, the condition coefficient is 2.5. Among the trunk defects on mountain ash, 16 specimens have dryness, 15 specimens have signs of cortical necrosis. Many authors in their works ^{[4, 13, 14]} indicate that necrotic cancerous diseases of trunks and branches play a significant role in the weakening and drying of rowan trees. Among them, biscognioxium (nummularium) necrosis is the most common and most dangerous in urban conditions. The causative agent of the disease is the marsupial fungus Biscogniauxia repanda (Fr.) Kuntze. Insufficient resistance of rowan trees to drought, atmospheric pollution, salinization, and excessive soil moisture contributes to a decrease in resistance to this disease. Trunk injuries also contribute to the spread of the pathogen. Biscognioxium necrosis affects plants of different ages, but with increasing age and, accordingly, the diameter of the trunk, the level of damage increases significantly ^[13]. And since there are 24 mountain ash trees among the 53 available on the surveyed site. they are still young plants, 0.5–1.7 m high, they are in the "risk group" for necrosis. The leaves of mountain ash are marked by sucking (aphids), leaf-gnawing, mining and skeletonizing insects, crown rust, and infectious spotting. According to the researchers ^[15], pests and pathogens of leaves lead to physiological and morphological disorders, a decrease in the pigment content of the assimilation apparatus.

The coefficient of state 2.4 is characterized by representatives of the genus Maple (K. ash-leaved and K. holly-leaved) and the Apple tree genus (Ya. domashnaya and Ya. berry). Leaf-gnawing and sucking insects, infectious (in K. ashen-leaved) and non-infectious spotting, powdery mildew are noted on maple leaves, dryness, growths, gnarled hollows, and open shoots on trunks. There are 8 maples among 28 specimens. (29%) are classified as severely weakened. Almost all of them have withers (up to 3 m long, 50% of the trunk circumference), and the presence of trunk hollows, closed seedlings, growths, stem pests, and fruit bodies of tinder plants is also noted (Figure 5). 1 K tree is classified as shrinking. ash-leaved without a top, although with growing water shoots in the lower part of the trunk, there are 50% of dry branches in the crown of the tree, there is a fruit body of common tinder (Fomes fomentarius (L.) Fr.) on the trunk.

a in b

Figure 5 – Defects in maple trunks: a) numerous growths in the lower part of the trunks. ash-leaved;b) dryness and closed sprouting on K. ash-leaved trees caused by a broken trunk; c) extensive dryness on K. holly with traces of stem pests

Apple tree plants are affected by leaf–gnawing, mining and sucking insects (aphids, cicadas), carpophages (apple moth), the presence of sooty fungi (Fumago vagans Pers., black leaves), non-infectious spotting, gnarled hollows on trunks, and dry leaves. Among the apple trees, there are 3 dead specimens, which led to a decrease in the coefficient value, and without taking them into account, the value of this indicator is 2.1, which indicates that the remaining plants are characterized by a generally weakened state. The dead specimens, old deadwood, grow outside private buildings near shrubby thickets, which is probably why they "escaped" the attention of the organization serving the street. Among 33 copies. Only 4 apple trees (12%) are classified as severely weakened. They show damage such as dead wood, twig and trunk hollows, and the presence of stem pests.

The largest number of trees (206 specimens) on the surveyed street is represented by a small-leaved linden. 73 specimens (35%) are pruned. Of the defects on linden trunks (Figure 6), the most common are knotty hollows, which occur in more than half of the trees, and there are also closed (23 specimens, 11%) and open (15 specimens, 7%) seedlings, deadwood (13 specimens, 6%), V-shaped forks (13 specimens, 6 %), trunk hollows (8 specimens, 4 %), growths (3 specimens, 1.5 %), frost cracks (2 specimens, 1 %). Many plants have water shoots, especially at the base of the trunk, as this species has a good shoot-forming ability. Of the available linden trees, 161 (78%) are classified as weakened plants. The severely weakened category includes 30 copies (15%), of which 9 copies. The presence of dried trees and open seedlings up to 5 m long was noted, 6 specimens of stem pests, 2 specimens of fruit bodies of fungi. A tree affected by common yarrow has a recorded trunk inclination of 45°, i.e. it poses a risk of loss of stability and threat of falling. There are also 18 specimens among the plants of this third category. they are young plantings with a height of 1.0–2.0 m, which are weakened by the lack of irrigation. Some of the young plantings (7 specimens, 3%) are classified as drying, 8 specimens. (4%) have already died. It is obvious that the survival rate of young plantings directly depends on the timely implementation of the necessary agrotechnical measures, especially ensuring adequate watering. In general, the value of the linden condition coefficient was 2.3. The linden leaf apparatus is damaged by sucking (aphids), leaf-gnawing, mining and skeletonizing insects, gall mites (including felt mites), there is non-infectious spotting and sooty fungi. Scabbing is observed on young plants.

a b c

Figure 6 – Damage on small-leaved linden: a) a trunk hollow in an open shoot with traces of the vital activity of stem pests; b) a split trunk in a thunderstorm; c) a trunk hollow after breaking the main trunk and the growth of stepsons

Among the 19 copies. 3 poplars (16%) were characterized as severely weakened. Both existing plants of T. tremens have withers and are damaged by stem pests. Also included in this category of condition is 1 specimen of balsamic, which also has a dryness. The so-called "Soviet Pyramidal" is represented by young plantings 0.7–2.0 m high, their leaves are affected by rust, damaged by leaf-gnawing and sucking insects. The leaves of T. balsamicus are damaged by the poplar mining moth moth (Phyllonorycter populifoliella Treitschke). This pest is widespread in urban areas of our country ^{[16, 17]}.

Among the representatives of the Plum genus, which, according to modern nomenclature, also includes cherry trees and cherries, the vast majority of plants are classified as weakened, with only 1 specimen. Common bird cherry is characterized as severely weakened. On the trunk of this tree there are fruit bodies of Schizophyllum commune (Schizophyllum commune Fr.), 2 dry leaves, leaf–gnawing and sucking insects (aphids), non-infectious spotting.

In general, the presence of deadwood was noted in 127 specimens of trees, which is 25% of the number of 513 deciduous trees in the surveyed territory. This defect appears as a result of injury to tree trunks and poses a danger of violating the integrity of the trunk integuments, being a place of penetration of fungal spores into plant tissues with the subsequent development of rot. Mechanical damage is found everywhere on plants, which indicates the careless attitude of many residents of the city towards the plants around them.

The shrubs on the surveyed street are generally in good condition. Only 1 copy. Viburnum vulgaris and 2 copies . Rosehips are classified as severely oppressed. The better vital condition of the shrubs is probably due to their faster renewability and unpretentiousness. Powdery mildew and aphids are noted on the karagan shrub and tree, chlorosis and infectious spots on the viburnum viburnum, common lilac, white svidina, chubushniki – aphids and leaf–eating, rosehip – aphids, cicadas, sooty mushrooms, non-infectious spotting. In general, among arthropod pests, sucking insects represented by various types of aphids are the most common on the surveyed plants. This pattern is also observed in other cities ^[15].

Attention should be paid to the problem of heavy pruning of urban plantings. Many authors ^{[3, 19]} note that the vital condition of woody plants decreases significantly after deep pruning, which affects the ecological, sanitary, hygienic and decorative qualities of trees. It is known ^[20] that radical pruning leads to accelerated tree death. A significant reduction in the crown of the tree leads to a decrease in the mass and surface area of the leaves, which leads to a reduction in assimilation, transpiration and respiration, and disruption of water and energy metabolism. Every pruning is a stress for the tree, every wound is a gateway to infection with pathogens. Except in some cases, a change in the shape of the crown leads to its deformation and weakening. The work affecting the crown of the tree must be carried out by qualified specialists who can determine the amount of work needed to minimize the stress of the tree. After radical pruning of the crown or roots, the tree gradually dies, energy reserves are depleted, and the weakened tree becomes an easy prey for fungal and bacterial infections and insect attacks. The tree spends energy on protection from phytophages and fungi, which exacerbates its shortage. This pattern is called the "death spiral" ^[20].

Thus, the plantings of the landscaping strips along K. Liebnecht Street are characterized by a weakened state of life. The main part of the plants (87%) belongs to the second category of sanitary condition. 28 dead specimens (3%) were found, they must be removed and replaced with new plants. In general, the living condition of the studied plantings is assessed as weakened, which indicates a good ecological situation on K. Liebknecht Street. The most frequent damages to tree trunks are gnarled hollows and deadwood, various types of aphids are most widespread on the leaf apparatus. A negative, but still unavoidable fact is the forced pruning of birch trees located under power lines, it negatively affects the vital condition of plants and reduces decorative effect. Rowan plantations are severely weakened, and the condition of maples, apple trees, and lime trees is slightly better. The shrubs on the surveyed street are generally in better condition than the trees. The mechanical damage that occurs indicates the careless attitude of many residents of the city towards the plants around them. It is necessary to carry out agrotechnical measures for the care of plantings to increase their viability.