تاثيرپذيري خصوصيات فيزيكي-شيميايي، فرسايش پذيري خاك و توليد رسوب از تغيير كاربري جنگل به ديم زار

The effect of land use change from forest to rain-fed farms on soil physico-chemical characteristics, erodibility and sediment yield

ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي ﺟﻨﮕﻞ ﻫﺎ داراي ﭘﯿﺎﻣﺪﻫﺎي ﻣﺘﻌﺪدي از ﺟﻤﻠﻪ ﺗﺸﺪﯾﺪ وﻗﻮع ﺳﯿﻞ، ﻓﺮﺳﺎﯾﺶ، رﺳﻮب و ﮔﺮد و ﻏﺒﺎر اﺳﺖ. ﺑﻪ ﻫﻤﯿﻦ ﻣﻨﻈﻮر، ﭘﮋوﻫﺶ ﺣﺎﺿﺮ ﺑﺎ ﻫﺪف ﺑﺮرﺳﯽ ﺗﺎﺛﯿﺮات ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي ﺟﻨﮕﻞ ﻫﺎي زاﮔﺮس ﺑﺮ ﻓﺮﺳﺎﯾﺶ ﭘﺬﯾﺮي و رﺳﻮب زاﯾﯽ از ﻃﺮﯾﻖ ﮐﺎﻫﺶ ﮐﯿﻔﯿﺖ ﺧﺎك در ﺑﺨﺸﯽ از ﺟﻨﮕﻞ ﻫﺎي اﺳﺘﺎن ﮐﺮﻣﺎﻧﺸﺎه اﻧﺠﺎم ﺷﺪ. در اﯾﻦ راﺳﺘﺎ، اﺑﺘﺪا دو ﻣﺤﺪوده ﺟﻨﮕﻠﯽ و دﯾﻢزار ﻣﺠﺎور آن ﮐﻪ ﻃﯽ 10 ﺳﺎل اﺧﯿﺮ ﺑﺮ اﺛﺮ ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي ﺟﻨﮕﻞ ﺣﺎﺻﻞ ﺷﺪه ﺑﻮد، اﻧﺘﺨﺎب و 35 ﻧﻤﻮﻧﻪ ﺧﺎك از ﻻﯾﻪ ﺳﻄﺤﯽ )ﺻﻔﺮ ﺗﺎ 20 ﺳﺎﻧﺘﯽ ﻣﺘﺮ( از ﻫﺮ دو ﮐﺎرﺑﺮي ﺑﺮداﺷﺖ ﺷﺪ. ﺳﭙﺲ، آزﻣﺎﯾﺶ ﻫﺎي ﻓﯿﺰﯾﮑﯽ و ﺷﯿﻤﯿﺎﯾﯽ روي ﻧﻤﻮﻧﻪ ﻫﺎي ﺧﺎك اﻧﺠﺎم ﮔﺮﻓﺖ. در ﻣﺮﺣﻠﻪ ﺑﻌﺪي، ﻣﯿﺰان ﻓﺮﺳﺎﯾﺶ ﭘﺬﯾﺮي ﺧﺎك ﻣﺤﺎﺳﺒﻪ و ﻣﯿﺰان ﺗﻮﻟﯿﺪ رﺳﻮب ﻫﺮ دو ﮐﺎرﺑﺮي ﺑﺎ اﺳﺘﻔﺎده از ﺑﺎران ﺳﺎز ﻗﺎﺑﻞ ﺣﻤﻞ در ﺻﺤﺮا اﻧﺪازه ﮔﯿﺮي ﺷﺪ. ﻧﺘﺎﯾﺞ اﯾﻦ ﺑﺮرﺳﯽ ﻧﺸﺎن داد ﮐﻪ ﺷﺶ وﯾﮋﮔﯽ ﻣﻬﻢ و ﮐﻠﯿﺪي ﺧﺎك، ﺷﺎﻣﻞ ﭘﺎﯾﺪاري ﺧﺎك داﻧﻪ ﻫﺎ، وزن ﻣﺨﺼﻮص ﻇﺎﻫﺮي، ﮐﺮﺑﻦ آﻟﯽ، ازت ﮐﻞ، ﭘﺘﺎﺳﯿﻢ و ﻇﺮﻓﯿﺖ ﺗﺒﺎدل ﮐﺎﺗﯿﻮﻧﯽ از ﻧﻮع ﮐﺎرﺑﺮي زﻣﯿﻦ، ﺗﺎﺛﯿﺮ ﻣﻌﻨﯽ داري )0/05

Forest and land use change has many negative consequences including increased flooding, erosion, sedimentation and dust storms. The aim of the research was thus to investigate the effects of land use change in Zagros forests on erodibility and sedimentation via soil quality reduction in some forests of Kermanshah Province, Iran. In order to achieve this aim, in the first step, afforest area and its adjacent rain-fed farm (which is developed during recent 10 years a result of forest land change), were selected and 35 soil samples were collected from the surface layer (0-20 cm). Then, the physico-chemical analyses were done on the soil samples. In the next step, soil erodibility factor was calculated and sediment yield was assessed using portable rainfall simulator. The results showed that six key properties of soil including soil aggregate stability, bulk density, organic carbon, total nitrogen, total absorbable potassium and cation exchange capacity were significantly (p<0.05) influenced by land use type. Additionally, in all tested samples, the total clay and silt content was about 80%, which resulted in the formation of soil with heavy texture. Subsequently soil erodibility factor (K) and sediment yield intensity in rain-fed farm was found significantly (P<0.05) higher than those of forest. According to the results and the role of Zagros forest ecosystem on water harvesting, aquifer recharge, flood and dust control, the current trend of changing forest landuse to arable lands accompanying improper tillage practice, crops residue burning and heavy machinery traffic in nearby rain-fed farms, cause accelerating global warming, increasing runoff coefficient and evaporation as well as water scarcity in future.