[Comparative study of water erosion of some soil types (forests , burnt forests , planted soil)in Lattakia]

Abstract:The phenomenon of water erosion is one of the most important types of soil degradation; this phenomenon has been accelerated as a result of human activities such as removing forests and cultivating them (especially the areas that have been burned), intensive tillage , overgrazing , cultivation of steep slopes. All of the above reasons lead to major agricultural, environmental and economic consequences on the site itself as well as the possibility of the access of these effects inside the surrounding environments. This phenomenon has been studied in a specific part of the coastal region , which is characterized by a completely dry summer with no rainfall followed by heavy rain with different frequency, it has been applied in three locations with varying soil types and slopes ( 25, 32 , 45%) including three systems (forests, burned forests, planted soils ). Twenty four 24 cases of rainfall events were recorded, those events caused both runoff and soil erosion during 2011-2012. The data and rates of soil erosion and runoff have been collected using experimental plot fields (4m2) , under natural conditions. High rates of erosion were observed in the planted soil, about ( 12-19) times comparing to what it used to be under system of the forest, with a rate between (4.5 - 6) times in the system of the burned forests compared to the system of the forest. These high rates are primarily due to the characteristics of the site such as the sloping degree, exhibition, soil texture and its physical, chemical and biological characteristics as well as those concerning the fire and its effects on the soil on each site. The largest amount of soil erosion was recorded in a specific site named 'Ain-Zarga with 121.83 t/ha/year in the planted soil versus 47.83 tonnes / ha / year in the burned forest area and 10.14 t/ha/year of natural forest which is characterized by an overwhelming sparse vegetation of Pinus brutia. When estimating the proportion of sand, silt and clay in the eroded soil taken from the study sites during the season 2011/2012, the clay particles proved to drift the most in Al-Hamraa' and Al-Sabaheya sites, whereas it was the sand grains that drifted the most in 'Ain- Alzarqa because of the high proportion of sand in the original soil. 62 The loss of soil was accompanied by the loss of organic matter. The amounts of drifted organic matter taken from the study sites under the agricultural system ranged from (0.2 - 2.6) t/ha/year, and from the burned forest (0.38 - 1.1) t/ ha / year depending on the different characteristics of the sites, soil type and its content of organic matter and therefore usability of erosion. Not only did the phenomenon of drift include the loss of the components of soil and nutrients, but also the loss of large amounts of rainfall as a runoff on the surface of the soil. Thus, the average coefficient of runoff was recorded with the largest value of 53.2% of the total amount of precipitation during the season of study and with a slope degree (45%) at the site of 'Ain-Zarqa in the planted soil compared with 29% in the system of the burned forest and 13.8 % in the forest system.