REGRESSION MODELS OF AERATION CONDITIONS OF FOREST DRAINED SOILS IN SOUTHERN TAIGA SUBZONE OF WESTERN SIBERIA
T. T. Efremova, S. P. Efremov, A. F. Avrova
Krasnoyarsk Science Centre of the Siberian Branch of Russian Academy of Science, V. N. Sukachev Institute of Forest, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, Russian Federation
Keywords: pine forests, mesotrophic peat soils, air capacity, oxygen in soil air, redox potential, linear model, parabolic function, regression residues, approximation accuracy
Abstract
The drained peat soils were studied (Drainic Hemic Histosols). The drained area of the mesotrophic swamp is occupied by young pine forests ( Pinus sylvestris L.) - sedge-sphagnum, reed, and mixed-grass-nettle at interchannel lanes of 94, 47, and 25 m, respectively. The average annual level of swamp waters - 23.2 ± 9.9, 42 ± 11 and 70.2 ± 16.0 cm characterizes the conditions of weak, moderate and intensive drainage. During May-October of three years, environmental indicators characterizing the aerophysical properties and volume humidity of soils were studied. In the ranked series of volume humidity, the 81-100 % class dominated in conditions of weak drainage, 20-60 % - moderate, and < 20-40 % - intensive drainage. In soils with moderate and intensive drainage, good aeration conditions prevailed (air capacity 21-90 %), the oxygen content in the aeration pores corresponded to atmospheric, and the class of redox potential, characterizing intensive oxidative processes, prevailed. In weakly drained soils, variants of good air capacity and to varying degrees of unsatisfactory (< 10-20 %) were equally common. The oxygen content of the soil air in 18 % of the relative frequencies dropped to 11-16 %. Against the background of mainly oxidative processes, weak reducing (300-400 mV) were observed in 9 % of the frequencies. In order to quick predict the air properties of peat soils when planning measures of drainage in peat lands, paired adequate models of the relationship between aerophysical parameters and volumetric humidity by the type of linear function and a quadratic parabola were constructed. According to the linear regression coefficients, an increase in humidity by 1 % is accompanied by a decrease in air capacity by 0.91 %. The points of extremum (maximum) of the parabolic function of volume humidity - 35.9 % and oxygen of soil air - 20.6 %, corresponding to atmospheric content, are calculated. The critical points of a maximum humidity of 42.9 % and a redox potential of 619 mV characterize the intensive development of oxidative processes. Based on the constructed model, a range of volume humidity of 65-80 % is predicted, which ensures a moderate course of oxidative reactions (redox potential 500-600 mV), preventing accelerated (unproductive) «combustion» of peat deposits. The range of application of regression equations is 8 (13) - 97 (93) % of the volume humidity.
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