Prosopis juliflora is one of the suitable tree species used as vegetation cover for sand dunes fixation. The objectives of this study were to determine the effect of P. juliflora afforestation and its canopy coverage classes on soil carbon (C) stock and nutrient status in sand dunes after 22 years since afforestation. We hypothesized that increasing the canopy coverage would result in higher soil C stocks and nutrient content. We selected two 10-ha afforested sand dunes with 25-50% and more than 75% canopy coverage, respectively, and a 10-ha non-afforested dune (control). At each site, 15 soil samples were taken at two depths (0-5 cm and 5-50 cm). The results indicated a strong increase in the topsoil C stock (from 0.54 to 4.49 tC ha -1 in control and afforested sites, respectively), while a lower change in subsoil C stock was detected (3.0 and 4.6 tC ha -1 in control and afforested sites, respectively). Although, different canopy classes resulted in no significant differences in soil C stock, significant differences were observed for all the soil physico-chemical properties that were studied.

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This study was done to evaluate the effect of afforestation in sand dunes at the vicinity of Shush, because of the importance of soil protection and wind erosion in sand dunes, also sand dunes afforestation as an effective and long lasting fixation mechanism. The study site was covered by petroleum mulch about 20 years ago and afforested by Prosopis juliflora. To study the effects of afforestation on sand dunes, two 10 ha afforested sites (25-50 and 75-100 percent canopy coverage) and control were selected. In each of studied site 15 plots were established and soil physiochemical properties were determined. Our result indicated that afforestation caused soil texture to change from sandy to sandy-loam. Also, soil phosphorus, potassium, organic carbon and nitrogen increased in 0-5 cm soil depth by afforestation that could be because of nutrient absorption from soil depth and returning to the surface by litter fall compared to the control. This study revealed that 25-50 percent canopy coverage resulted in better soil physiochemical properties compared to control site. In conclusion, sand dunes afforestation not only resulted in sand dunes fixation but also soil fertility and long lasting fixation.