Impacts of hydrological conditions on the activities of soil enzymes in temperate floodplain forest sites

Abstract

Context: The development and survival of floodplain forests are dependent on the occurrence of seasonal flooding that provides soil moisture and nutrient availability suitable for the development of soil microorganisms, which are the main sources of soil enzymes involved in the decomposition and mineralisation of soil organic matter. Aims: We compared the soil enzyme activities of a floodplain forest in the Lower Vistula Valley, Poland, cut off for 80 years from the river by artificial embankment, and of two other floodplain forests located in close vicinity and subjected to seasonal flooding. We hypothesised that inhibiting the inflow of the river water to the floodplain forest will alter the soil water and mineral conditions, decreasing the activity of extracellular soil enzymes. Methods: Enzyme activity, soil moisture content, and pH were monitored for 3 years in the upper soil level (0-30 cm). The activities of soil β-glucosidase, acid phosphatase, alkaline phosphatase, and nonspecific dehydrogenase were determined by spectrophotometry. Key results: Inhibition of floods decreased soil moisture, the concentrations of carbon, nitrogen, and phosphorus, as well as the activity of soil enzymes. Conclusions: Forest site and soil depth, but not season, had significant effects on soil chemical and biological features. Soil enzyme activities were significantly positively correlated with soil moisture and the levels of total and organic carbon, total nitrogen, and available phosphorus, as well as the carbon/nitrogen ratio. Implications: This information is essential for the protection and restoration of riverine habitats destroyed by human activity.