Assessment of Provisioning Ecosystem Services of Irrigated Salt-Affected Soils in Ukraine

Irrigated, withdrawn from irrigation, and nonirrigated areas with southern chernozems (Calcic Chernozems) and dark chestnut soils (Haplic Kastanozems) of different degrees of natural and irrigation-induced salinity and solonetzicity were examined within the Ingulets irrigation system in Kherson and Nikolaev oblasts with the aim to assess provisioning ecosystem services of salt-affected soils in Ukraine. The suggested system is based on the results of the eco-agromeliorative assessment of land for pilot areas and takes into account susceptibility of the ecosystem services of salt-affected and solonetzic soils to different kinds of reclamation. In most cases, the soils of nonirrigated areas were characterized by the satisfactory eco-agromeliorative status, and the soils irrigated by sprinkling and withdrawn from irrigation had the good or satisfactory status depending on the depth and salinity of the groundwater. The soils subjected to drip irrigation were in the unfavorable state because of noncompliance with recommended irrigation technologies. Irrigation with slightly saline water caused changes in the structure of soil microbial cenoses and disturbance of the optimal ratios between different groups of microorganisms. In these soils and in the soils withdrawn from irrigation because of the development of secondary salinization and alkalization, the numbers of major trophic groups of microorganisms (eutrophic and oligotrophic bacteria and actinomycetes) and the total soil enzymatic activity decreased. The assessment of susceptibility of the ecosystem services of salt-affected soils to reclamation impacts (chemical amelioration and deep meliorative plowing) demonstrated certain positive changes in the efficiency of soil ecosystem services, such as the productive capacity, the habitat of species, the storage pool for carbon, and the nitrogen fixation capacity. An expert ten-grade scale to assess the productive ecosystem services of salt-affected soils in Ukraine has been developed. It is based on eight characteristics. According to this scale, the areas with the good state of the soils are virtually absent in the examined territory; the satisfactory state has been assigned to 14 surveyed areas; and the unsatisfactory state, to one area with a shallow depth of saline groundwater. This approach provides for a more efficient use of the provisioning functions of salt-affected soils owing to differentiation of reclamation impacts on them and their adaptation to the functioning of biological systems.