FRACTAL PARAMETERS OF PORE SURFACES AS DERIVED FROM MICROMORPHOLOGICAL DATA - EFFECT OF LONG-TERM MANAGEMENT-PRACTICES

Differences between soils in their porosity need to be quantified to d iagnose changes related to management practices or to pedogenesis. Mic romorphological data give abundant information on soil pore arrangemen t whereas fractal geometry presents tools to quantify irregular and ru gged boundaries characteristic to soil pores. The objective of this wo rk was (a) to verify applicability of the fractal scaling to irregular pore outlines revealed on soil thin sections, and (b) to test the cap ability of fractal parameters to reflect an influence of management pr actices on soil porosity. We sampled Comly silty loam soil in plots wh ere nitrogen was supplied from conventional fertilizer sources, manure , legumes, and in uncultivated plots under grasses where no nitrogen h as been supplied. Using slit-island technique, we have shown that frac tal scaling was applicable to soil pore outlines revealed on thin sect ions, Piecewise-linear log-log relationships were found between pore a rea and pore perimeter. Small pores with areas less than 10(-9) m(-2) had fractal dimension D-1 between 1.06 and 1.12. Pores with areas exce eding 10(-9) m(2) had fractal dimension D-1 between 1.42 and 1.51. The boundary between two ranges corresponded to the boundary between vugh y and rounded pores. Pores with rugged fractal outlines represent 15-3 0% of total pore number and provide 86-98% of the total visible pore a rea. Management practices affected only the number and the area of lar ge elongated pores. Value of D-2 was larger in samples from the legume plots than in samples from other plots.