Enzyme activity as an indicator of the ecological stateof alluvial soils (on the example of the zeya river)
A. V. MARTYNOV1, O. A. PILETSKAYA2
1Institute of Geology and Nature Management, Far East Branch,Russian Academy of Sciences, Blagoveshchensk, Russia
2Far Eastern State Agrarian University, Blagoveshchensk, Russia
Keywords: alluvial soils, floodplains, enzymes, phosphatase, urease, catalase, peroxidase, polyphenol oxidase, flow regulation, Zeya hydroelectric power plant
Abstract
Regulation of river flow due to the construction of hydroelectric power plants and dams leads to a significant transformation of floodplain ecosystems and their components downstream. One of the ways to assess the ecological state of natural landscapes is to determine the enzymatic activity. At the same time, there is undeservedly little data in the world literature on the activity of enzymes in floodplain landscapes, not only disturbed but also natural. This fact is associated with difficulties in the study of floodplain areas, highly dynamic natural objects with a strong variation of properties and parameters in space and time. With this work, we partially fill this gap by showing whether the activity of enzymes can be used to assess the ecological state of floodplain soils with long-term regulation of river flow. As an example, the Zeya River has been regulated by the Zeya hydroelectric power station since 1975. We determined the activity of enzymes (phosphatases, ureases, catalases, polyphenol oxidases and peroxidases) in five types of floodplain landscapes: meadow on the riverine floodplain; meadow, arable land and forest on the central floodplain; swamp in the near-red depression. High activity of phosphatase (max. up to 10 mg/g), and low activity of urease (max. up to 0.55 mg/g) and catalase (max. up to 0.55 g/cm3) were found. The activity of polyphenol oxidase (max. up to 85 mg/100 g) and peroxidase (max. up to 290 mg/100 g) expressed through the humus accumulation coefficient (max. 41 %) indicates the average level of soil fertility of the floodplain. The diversity of enzymes was evaluated using the Pielow index and geometric mean. It was determined that under conditions of long-term regulation, the best indicators of enzymatic activity are characteristic of soils under floodplain forest, the minimum - for arable soils. A single soil parameter that would reliably affect all enzymes has not been identified. Phosphatase, urease and catalase exhibit significant positive relationships with H & Al. Strong positive relationships of catalase with organic matter and negative with pH. The data obtained allow us to state that long-term regulation of river flow leads to a decrease in the activity and diversity of enzymes.
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