Impacts of land use/cover change on soil properties in the Mediterranean region of northwestern Jordan

Abstract

This study was carried out to evaluate the effects of deforestation on physical and chemical properties of soils under native forest in the Mediterranean region of northwestern Jordan. Land use/cover maps of 1953, 1978 and 2002 were interpreted and analysed within GIS to quantify the shift from forest to rainfed cultivation. Six sites were sampled in a non-changed forest and in cultivated fields, three for each. Different soil properties of texture, bulk density, organic matter, total nitrogen, pH, cation exchange capacity (CEC), phosphorous and potassium were analysed. Results showed that many forests were changed into cultivated lands at a rate more than the reforestation. Subsequently, adverse effects on the studied physical and chemical properties were observed. The most affected properties were particle size distribution, bulk density of surface soil and subsoil. Organic matter and CEC decreased in cultivated soil as compared to the forest soil. Cultivated soils were found to exhibit a significantly lower status in physical and chemical soil properties as compared to forest soils. This general decline in the soil physical and chemical properties, in turn, contributed to soil erosion, reduction of soil fertility and land degradation.There is an urgent need to improve soil quality by developing sustainable land use practices to reduce the rate of soil degradation and to ensure long-term sustainability of the farming system in the study area and in similar biophysical settings.

The effects of land use types and soil depth on soil properties of Agedit watershed, Northwest Ethiopia

“…An increase in the level of SOM in the forest could have been the result of accumulation of plant residues in the upper few centimeters soil depth and their lower rate of decomposition and disturbances (Khresat et al, 2008 andSaikeh et al, 1998). Conversely, the decline in SOM contents in the cultivated land could be attributed to the effect of continuous cultivation that aggravates organic matter oxidation and insufficient inputs of organic substrates from the farming system due to residue removal and zero crop rotation.…”

“…The amount, rate and intensity of land use changes are mainly considerable in developing countries (Rao and Pant, 2001).The outcomes of these changes are deterioration of soil physicochemical properties, increased soil erosion or soil compaction (Rao and Pant, 2001) and land degradation (Woldeamlak Bewket and Stroosnijder, 2003;Khresat et al, 2008). As a result, cultivated soils in different parts of the tropics are now below their potential levels.…”

“…Despite the general understanding of the impacts of land use change as hazards to agricultural productivity, very few studies have been done to quantify the extent, rate and process of soil fertility depletion under different land use and management practices in Ethiopia (Eyasu Elias, 2002 (Islam and Weil, 2000;Chen and Li, 2003;Khresat et al, 2008). …”

Interrelationships of Land Use/Cover Change and Topography with Soil Acidity and Salinity as Indicators of Land Degradation

“…The large values of soil EC at lower depth in contrast to the lesser values of EC and lower values of pH in the topsoil under Woodland LULC type may be attributable to microclimate of forest flora which may have increased organic matter and soil microflora especially at surface layer [43,47]. As demonstrated by the biplot of CCA (Figure 5b) CTI and Past_C have somewhat closer association with ECdeep which is logical in the sense that soluble salts would have leached to the lower depths.…”

“…However, Woodland consistency was found to have lower topsoil EC compared with the same values under other LULCs whereas in the case of the subsoil, Woodland has slightly higher EC compared to others. This is probably due to increased leaching of salts from the topsoil to the lower soil layers under forest, and/or due to preponderance of soil organic matter and hence higher microbial activity under forest soils compared to cultivated soils [16,43]. In the case of the layer just below the surface layer, there was no definite trend in EC across different LULC categories (Table 3).…”