Velikoanadolsky forest area is the first artificially created massif in the Steppe on the territory of present-day Ukraine. More than 170 years of experience in afforestation of the Steppe gives grounds to consider Ukraine the homeland of steppe afforestation. Summing up the forest management activities in the forests of the Velikoanadolsky forest area during this period is important in view of the prospects for the establishment and formation of forests in the Steppe zone in the future. The aim of the study is to investigate the history of the creation and cultivation of oak (Quercus robur L.) forests in Velikoanadolsky forest area and to evaluate their productivity and current state; to determine the ways of their reproduction.
Materials and Methods
The health condition and forest mensuration characteristics were analyzed using the database of the production association «Ukrderzhlisproekt» and sample plots established in the forest area. The plots establishment, field data collection and analysis were carried out according to methods commonly used in forestry, forest inventory and statistics.
The history of the creation and development of Velikoanadolsky forest area passed through eight stages from the period of the garden method by V. E. Von Graff, the application of dense plantations by L. G. Bark and the “normal” type plantations with 50 % of Ulmaceae to the stages of the development of tree-shrub and tree-shadow types of plantations and fundamental plant reconstruction. The forest stands of Velikoanadolsky forest area have environmental, scientific, historical and cultural significance. They fulfill important climate-regulating functions. The influence of the forest stands on the microclimate of the territory is evident in the decrease in the accumulated positive monthly temperatures (by an average of 5 %) and in the average many-year mean temperatures during the growing season (by 6 %) on the territory of the area compared with the open steppe. The share of precipitation during the period of intensive growth of plants in the forest area is greater. As of 2016, it was 35 % over 28 % in open areas.
The forest fund of Velikoanadolsky forest area is represented mainly by oak stands (86 % of the area) the vast majority of which are artificial ones. The oak stands are mostly mixed; the proportion of pure forest stands is 28 %. In the mixed stands, the associate species are European ash (Fraxinus excelsior L.), Norway maple (Acer platanoides L.) and field maple (Acer campestre L.). The proportion of oak in young stands is 50–60 % and gradually increases to 70–75 % in 70–100-year-old stands.
The age structure of the oak stands of Velikoanadolsky forest area is unbalanced. Among artificial stands, the stands of approaching maturity are the most prevalent. The oak plantations have a simplified vertical structure; they do not have a second layer composed of accessory species. The unbalanced age structure and the gradual aging of the oak stands of the forest area negatively affect the annual quantities of carbon sequestration and therefore their climate-regulating functions.
The health of the oak stands of the forest area is deteriorating as a result of natural and anthropogenic factors. The health condition index (Ic) of pure artificial stands is 1.65–2.40 at the age of 60–100 years and is 2.5–2.75 for the stands over the age of 100 years. Oak coppice stands, regardless of the composition, are very weakened from the age of 70–80 years (Ic is 2.5–3.0). In pure oak stands, the trees of the 1st–2nd Kraft classes fall within the category of dead standing trees, along with the natural mortality of lighter trees. This significantly increases the stock of dead standing trees and negatively affects the merchantable structure of the stands. The mixed stands are more resistant to adverse environmental factors than pure ones. The negative effects due to the intensification of the oak plantations drying and their disturbance during the last 10–15 years have led to an increase in the intensity of selective sanitation felling from 3–7 % in 1974–1996 to 19–25 % in 2007–2013 due to the accumulation of significant amount of dead standing trees. Selective sanitary felling eliminates the consequences, not the causes of oak dying, and only temporarily improves the sanitary state of the stands.
The natural advance regeneration is absent, bad or insufficient in 75 % of the oak stands. The available natural advance reproduction is predominantly represented by the advance growth of Acer platanoides and Fraxinus excelsior. The proportion of Quercus robur is insignificant (less than 1 %). The self-seeding of oak dies, being unable to compete with the advance growth of the associate species and understory trees. The advance growth is arranged to sites with sufficient sunlight and without dense ground vegetation.
Forest plantations of Velikoanadolsky forest area fulfill important climate-regulating functions and are of great economic importance. The positive influence of forest plantations on the area microclimate is evident in lowering the air temperature, increasing the humidity and annual precipitation and mitigating the negative impact of climate change.
The oak stands of forest area have a simplified structure, which determines the decreased resilience to adverse environmental factors. The coppice and pure artificial stands undergo the weakening processes to a greater degree than mixed ones. There is a need for relevant forestry activities aimed at optimizing the age structure of the forest fund of Velykanadolsky forest area. To regenerate valuable oak forests, it is advisable to introduce regeneration felling in combination with other activities.
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