Morphological characteristics of cracks in soil with and without vegetation cover

Abstract

An assertive understanding of cracks in expansive soils makes their typification a challenge, especially in field conditions. Seeking to overcome such difficulty, digital images have been used to estimate the fractal geometry of surface cracks in soils with and without vegetation in a semi-arid environment. This study was carried out in a cross-section along the main course of a first-order watershed in the Centro Sul region, Ceará State (Brazil). Two treatments comprised soil with and without vegetation cover. Experimental plots were installed to represent the upper, middle, and lower parts of the watershed studied (vegetated and non-vegetated), with an area of 1 m2 and spaced 2 m apart. The following morphometric characteristics of cracks were monitored and evaluated during 38 days, namely: area, weighted average between crack area and its perimeter, weighted average of the fractal dimension area of the cracks, connectivity between cracks and soil moisture. In the soil with and without vegetation, intensity of cracks in the soil had a significant correlation (p ≤ 0.01) with the perimeter, fractal area and crack connection. The intensity of cracks between covered and uncovered plots showed a significant difference (p ≤ 0.01), only in the lower part of the watershed. The middle stretch had higher sand content and differed statistically from the lower stretch for intensity of cracks in the soil. Vegetation influenced the correlation between cracks intensity and their connection, influencing their morphology in the sandy stretch.