Changes in vegetation and soil properties along a slope on overgrazed and eroded rangelands

Rangelands, generally located on steep semi-arid zones, have a special importance in resource management. Continued overgrazing and erosion cause range degradation by altering plant communities and soil properties. The objective of this study was to determine changes in vegetation and soil properties along a slope on overgrazed and moderately eroded rangelands. Four study sites with three landscape positions: summit, backslope and footslope, were selected. In each position, botanical composition, canopy coverage, rangeland quality degree, and some important surface soil properties such as texture, bulk density, moisture content, organic matter content, CaCO3 content and plant available-P content, were determined. The frequency of grasses in botanical composition varied from 39.5% to 84.0%, and on the average, the frequency was lowest at summit and highest at footslope positions. The frequency of legumes at summit positions was lower than those of the other positions in two range sites. The amount of canopy coverage changed between 19.6% and 45.2%. The highest amounts were obtained in footslopes and the lowest amounts were in summits. The degree of range quality varied between 3.2 and 5.5. Based on the overall means of the four sites, there were no significant differences among the positions regarding range quality degree, but it was generally lowest at summit positions. Clay content of surface samples was lowest at backslopes in all sites. But, there were no significant differences in clay contents of the summit and footslope positions. Changes in soil bulk density showed a significant trend along the slopes, and it was generally higher in backslope and footslope than that of summit position. Soil moisture content at time of sampling and organic matter content was generally higher at footslope positions than those of backslope and summit. While the amount of plant available-P was the lowest at backslope positions of the range sites, CaCO3 content of soil was lowest at footslopes in all sites. (C) 2003 Elsevier Science Ltd. All rights reserved.