Climate Effect on the Enzymatic Activity of Northern Caucasian Forest Soils

This work considers the influence of climatic factors on the enzymatic activity of different zonal soils of the Northwestern Caucasus-brown forest soils, gray forest soils, and gray forest-steppe soils. A correlation analysis of the relationship strength between climatic parameters and the soil enzymatic activity (catalase, dehydrogenase, invertase, peroxidase, and polyphenol oxidase) has been carried out. The following climatic parameters are used: the average annual temperature, the average monthly temperatures of January and July, the average annual temperature range, the average annual precipitation, and the amount of precipitation during the growing season, as well as indices and coefficients reflecting the combined effects of climatic factors (the Ivanov-Vysotsky humidification coefficient, de Martonne's aridity index, and Gorchinsky index of continentality). A close correlation between the activities of catalase and peroxidase and all the climatic indicators has been established. The dehydrogenase activity depends on the humidity indicators, while the invertase activity, on the contrary, depends to a greater extent on temperature indicators of the climate. The activity of polyphenol oxidase in the upper soil horizons is not affected by the climate; however, the total activity of the entire profile closely depends on it. The values of the biological state integral indicator (BSII) in the soil profile decrease with an increase in precipitation and decrease in temperature. The climate affects not only the upper soil horizons, which are directly exposed to the environment, but the entire soil profile.