Climatic gradients of biological properties of zonal soils of natural lands

Abstract

It has been found that climatic conditions affect the biological properties of soils on which their fertility and sustainability depends. Most studies on the impact of climate change on soil properties are based on the results of model experiments, which focus on changes in one, rarely two factors. In these experiments the direct influence of climatic factors on soil properties is traced, but in natural conditions the climate has not only direct influence, but also indirect, influencing other factors. Therefore, it is very important to study the response of soils to climate change in the geographical aspect. This knowledge will allow us to make more accurate predictions of soil fertility, sustainability, quality and health under possible climate change. Two transects crossing the North Caucasus in latitudinal and meridian directions have been investigated. The first transect is latitudinal one, its general direction is from west to east, it is 800 km long, passes through plains, dry plains and semi-deserts and reflects the increasing continentality of the climate from west to east. The second transect is meridional, which is 1000 km long, crosses the plains, forest-steppe, deciduous and coniferous forests as well as mountain meadows in a north–south direction. It reflects climate changes during the transition from plain natural zones to the mountainous zones of the Caucasus Mountains. The patterns of dependence of biological properties were revealed for Chernozems, Kastanozems, Calcisols, Phaeozem, Cambisols, Leptosols zonal soils of the North Caucasus: the number of fungi and bacteria, activity of catalase (CA), dehydrogenase (DH), polyphenol oxidase (PPO), peroxidase (PO) and invertase (IN), soil organic carbon (SOC) content versus climatic parameters (temperature, precipitation, climatic indices and coefficients). The factors limiting biota and biological activity of soils have been identified. The maximum dependence of their biological parameters is typical for extreme climatic conditions. The highest correlation of biological parameters of soils was noted with the annual precipitation and temperature amplitude. The maximum values of the total biological activity, taking into account the entire soil profile, were noted in warm and sufficiently humid climatic conditions, where deep Haplic Chernozem Pachic are formed. When the moisture conditions change, both towards aridization and humidization, the total biological activity of soils decreases, which is calculated for the entire thickness of the soil to the rock. SOC is an accumulative indicator of biological activity, therefore it most closely correlates with most of the studied climatic indicators. Among soil enzymes, a close dependence on climatic parameters was established for CA. IN, DH, PPO and PO have more complex non-linear relationships with climatic conditions.