Soil factors of resistance of spruce forest.

Spruce (Picea abies (L.) H. Karst.) is one of the major coniferous species represented in Moscow region. It grows on loam or clay loam soils and it is sensitive to soil moisture. The drought of 2010 adversely affected spruce forest. Weak spruce is further highly influenced by various pathogens and pests, among which the most aggressive is bark beetle (Ips Typographus L.). Many researchers have investigated the role of climatic fluctuations in respect of the development of pathogens; however, soil and hydrological factors are often out of the focus. The aim of our work was to study the soil factors affecting the state and resistance of spruce stands. The object of the study was spruce stands of the Moscow educational-experimental forest unit. Forest inventory data in combination with satellite imagery in a GIS environment allowed us to discover a plot with alive resistant spruce surrounded by dead spruce stands of the same age. During field surveys, we investigated soil in both alive and died spruce plots. The study showed that alive spruce forest has developed on soil with specific alternation of horizons of different texture (contains sand layer of varying thickness, underlain by loam horizons). The surrounding soils with dead spruce do not have such a sandy layer. The combination of layers with different texture support accumulation of soil moisture. This moisture, which is trapped by capillary forces in the small pore layer of the soil. Most probably, the ability of soil to store more water has allowed spruce to survive during the drought. We plan to continue our research and investigate more plots with alive spruce stands, to prove our hypothesis.