Deforestation effects on soil properties and erosion: a case study in the central Rif, Morocco

Abstract

In the Central Rif in the north of Morocco, forest ecosystems have suffered a very sharp decline in favor of crops. Deforestation followed by cultivation illustrates the important environmental, economic and social roles of forests. The objective of this work is to assess the impact of deforestation on soil properties and erosion in the southern Central Rif. The loss of fertility of cleared soils was assessed using physico-chemical analyses after 2, 8 and 20 years of cultivation. A manual rainfall simulation was used to assess the impact of cultivation on the hydrodynamic behavior of the soil. The results show that the conversion of forests into agricultural areas has multiple consequences on the natural system. The general trend of soil texture elements after cultivation shows a significant increase in sand content, and a decrease in clay and silt content. Soil erodibility measured by USLE-K factor increased 3.5 times in the cultivated soil for 20 yrs. compared to the forest soil. Subsequent tillage of cultivated land increases bulk density and fragments large aggregates into smaller ones. Cultivation for 8 and 20 yr decreased SOM by 41 and 82% respectively. Total Nitrogen decreased by 45%, acidity increased by 0.8 unit after 20 years of cultivation. Conversion of natural forest to agricultural land significantly increases soil erosion. The erosion rate becomes higher in the cultivated the 8 and 20 yr cultivation, with an average of 219.60 ± 19.3 and 989.17 ± 68.4 g m-2 h-1 respectively. This degradation hinders agricultural productivity, leading farmers to abandon the land and seek new plots at the expense of forests to meet their agricultural land needs.