Rate of Fen-Peat Soil Subsidence Near Drainage Ditches (Central Poland)

Ryszard Oleszczuk,Janusz Urbański,Jan Jadczyszyn,Ewelina Zając

doi:10.3390/land10121287

Abstract

This study analyzed design depths (to), post-subsidence depths (t), shallowing magnitudes (d = to − t) and ratio values (d/t) of 12 drainage ditches in a fragment of the drained Solec fen-peat (central Poland) over a period of 47 years between 1967 and 2014. A significant decrease of the designed depth of the ditches to was shown, from the average designed value of 0.97 m to their average depth after subsidence, t = 0.71 m. The ratio (d/t) of 0.41, which is associated with the degree of organic matter decomposition, indicated medium degree of peat decomposition. The average values of bank and bottom subsidence of the ditches during the analyzed period, 1967–2014, were 0.43 m and 0.17 m, respectively. The values of the average annual rate of land surface subsidence in the vicinity of the ditches were varied and within the range of 0.09 cm year−1 to 1.70 cm year−1, with an average of 0.92 cm year−1. Two linear empirical equations were proposed to calculate the amount of subsidence and the average annual rate of subsidence of peat soil surface near the drainage ditch route, based on the knowledge of the initial thickness of the peat deposit. The results of calculations using the equations proposed by the authors were compared with calculations of the same parameters using 10 equations published in the literature. The results obtained using the proposed equations were mostly larger than those calculated with literature-published equations.

Highlights

In excessively humid areas, the high groundwater table and low air content in the soil are conducive to the formation of peat soils, which are characterized by a high organic carbon content
The change in air–water relations that accompanies the drainage of peatlands has caused the initiation of mucking and mineralization processes in organic matter, and the conversion of organic forms of nitrogen into mineral compounds and emission of greenhouse gases, such as carbon dioxide and nitrous oxide, into the atmosphere [7,8,9]
Based on the ordinates of the banks and bottom of the ditches at each hectometer, it was found that the design depth of the ditches was within

Summary

Introduction

In excessively humid areas (e.g., river valleys), the high groundwater table and low air content in the soil are conducive to the formation of peat soils, which are characterized by a high organic carbon content. Are peat soils, 1.6% are sited peat soils, and 6.1% are moorsh soils [5] These areas, used by many disciplines (including agriculture, horticulture, and forestry), have been drained in numerous cases [6]. This has resulted in the interruption of the existing organic matter accumulation process due to incomplete decomposition under conditions of very high humidity and lack of air access. In their natural state, these soils absorb carbon dioxide as a result of the assimilation and photosynthesis processes of the vegetation living in these areas. The change in air–water relations that accompanies the drainage of peatlands has caused the initiation of mucking and mineralization processes in organic matter, and the conversion of organic forms of nitrogen into mineral compounds and emission of greenhouse gases, such as carbon dioxide and nitrous oxide, into the atmosphere [7,8,9]

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Results

Discussion

Conclusion