اثرات تبديل جنگل به زراعت چوب بر بازپخش خاك با استفاده از راديونوكلوئيد سزيم137

Effects of conversion of forest land to Plantation on soil redistribution using cesium 137

روش اﯾﻦ ﭘﮋوﻫﺶ، ﺑﺮ اﺳﺎس ﻣﻄﺎﻟﻌﺎت ﻣﯿﺪاﻧﯽ و آزﻣﺎﯾﺸﮕﺎﻫﯽ ﺗﻨﻈﯿﻢ ﺷﺪه اﺳﺖ. در اﯾﻦ ﺗﺤﻘﯿﻖ، ﺑﺮاي ﻧﺨﺴﺘﯿﻦ ﺑﺎر اﺛﺮات ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي ﺟﻨﮕﻠﯽ ﺑﻪ ﺑﺎﻏﺎت در ﻣﯿﺰان ﺑﺎزﭘﺨﺶ ﺧﺎك ﻣﻨﺎﻃﻖ ﭘﺎﯾﯿﻦﺑﻨﺪ ﺟﻨﮕﻞﻫﺎي ﻫﯿﺮﮐﺎﻧﯽ ﮔﯿﻼن ﺑﺎ اﺳﺘﻔﺎده از روش رادﯾﻮﻧﻮﮐﻠﻮﺋﯿﺪ ﻣﺤﺎﺳﺒﻪ ﺷﺪه اﺳﺖ. در اﯾﻦ ﺷﯿﻮه، ذﺧﯿﺮه ﺳﺰﯾﻢ 137 اﯾﻦ ﻣﻨﺎﻃﻖ ﺑﺎ ﻣﻨﻄﻘﻪ ﻣﺮﺟﻊ ﻣﻘﺎﯾﺴﻪ ﺷﺪه اﺳﺖ. در ﻣﺤﻞ ﻣﺮﺟﻊ، ﺗﻌﺪاد 11 ﻧﻤﻮﻧﻪ ﻣﻐﺰه ﺧﺎك و در ﺗﺮاﻧﺴﮑﺖ ﻣﻌﺮف ﮐﺎرﺑﺮي زراﻋﺖ ﭼﻮب ﺗﻌﺪاد ﻫﻔﺖ ﻧﻤﻮﻧﻪ ﻣﻐﺰه ﺧﺎك ﺑﻪ ﻋﻤﻖ 25 ﺳﺎﻧﺘﯽﻣﺘﺮ ﺑﺮاﺑﺮ ﺑﺎ ﺿﺨﺎﻣﺖ ﺑﻪﻫﻢرﯾﺨﺘﮕﯽ ﺧﺎك در ﺣﯿﻦ ﺟﻨﮕﻞزداﯾﯽ، از ﺑﺎﻻي داﻣﻨﻪ ﺗﺎ ﻣﺤﻞ دره ﺑﺮاﺳﺎس ﻋﻮارض ﺗﻮﭘﻮﮔﺮاﻓﯽ ﺑﺮداﺷﺘﻪ ﺷﺪ. ﻧﻤﻮﻧﻪﻫﺎ ﭘﺲ از آﻣﺎدهﺳﺎزي، ﻣﻄﺎﺑﻖ اﺳﺘﺎﻧﺪارد آژاﻧﺲ ﺑﯿﻦ اﻟﻤﻠﻠﯽ اﻧﺮژي اﺗﻤﯽ در ﻇﺮوف ﻣﺨﺼﻮص دﺳﺘﮕﺎه ﻃﯿﻒﺳﻨﺞ ﮔﺎﻣﺎ ﺑﺴﺘﻪﺑﻨﺪي و ﻣﻮﺟﻮدي رادﯾﻮﻧﻮﮐﻠﻮﺋﯿﺪ ﺳﺰﯾﻢ 137 ﮐﻠﯿﻪ ﻧﻤﻮﻧﻪﻫﺎ ﺑﺮ ﻣﻘﯿﺎس ﺑﮑﺮل ﺑﺮ ﮐﯿﻠﻮﮔﺮم ﺳﻨﺠﯿﺪه ﺷﺪ. ﺑﺮاﺳﺎس ﻧﺘﺎﯾﺞ ﺑﻪدﺳﺖ آﻣﺪه، ذﺧﯿﺮه رادﯾﻮﻧﻮﮐﻠﻮﺋﯿﺪ ﺳﺰﯾﻢ 137 در ﻣﺤﻞ ﻣﺮﺟﻊ ﺑﺎ ﻟﺤﺎظ ﮐﺮدن ﺳﻄﺢ ﻧﻤﻮﻧﻪﺑﺮداري 5894/1 ﺑﮑﺮل ﺑﺮ ﻣﺘﺮﻣﺮﺑﻊ ﺑﻪدﺳﺖ آﻣﺪ. در ﭘﮋوﻫﺶ ﺣﺎﺿﺮ، ﻧﺮخ ﺑﺎزﭘﺨﺶ ﺧﺎك در ﻃﻮل ﺗﺮاﻧﺴﮑﺖ ﻣﻌﺮف ﺑﺎ اﺳﺘﻔﺎده از ﻣﺪلﻫﺎي ﺗﺒﺪﯾﻞ ﺗﻨﺎﺳﺒﯽ و ﺗﻮازن ﺟﺮﻣﯽ I و II ﺑﻪﺗﺮﺗﯿﺐ 22/72 ،18/70 و 18/64 ﺗﻦ در ﻫﮑﺘﺎر در ﺳﺎل ﺑﺮآورد ﺷﺪ. اﯾﻦ ﻣﻘﺎدﯾﺮ ﺑﺮاي ﺷﯿﺐ 10-20 درﺻﺪ و ﺗﺎج ﭘﻮﺷﺶ ﺗﻨﮏ 25 درﺻﺪ و ﺧﺎك ﻟﻮﻣﯽ-رﺳﯽ ﺗﺤﺖ ﺑﺎرش 1000 ﻣﯿﻠﯽﻣﺘﺮ ﺑﻪدﺳﺖ آﻣﺪه اﺳﺖ. اﯾﻦ ﭘﮋوﻫﺶ، ﻣﺪل ﺗﻮازن ﺟﺮﻣﯽ II را ﺑﺮاي ﺑﺮآورد ﻓﺮﺳﺎﯾﺶ در ﻣﻨﺎﻃﻖ ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي داده ﺷﺪه ﺗﻮﺻﯿﻪ ﮐﺮده، ﻧﺘﯿﺠﻪ ﮔﺮﻓﺖ ﮐﻪ ﺗﻐﯿﯿﺮ ﮐﺎرﺑﺮي اراﺿﯽ ﺟﻨﮕﻠﯽ ﺑﻪ زراﻋﺖ ﭼﻮب ﺑﻪدﻟﯿﻞ ﺗﻘﻠﯿﻞ ﺳﻄﺢ ﭘﻮﺷﺶ ﻃﻮﻻﻧﯽ ﺧﺎك و ﻣﺪﯾﺮﯾﺖ ﺑﺎغ در اﺛﺮ از ﺑﯿﻦ ﺑﺮدن دﯾﮕﺮ ﻧﻬﺎلﻫﺎ و ﭘﻮﺷﺶ ﻋﻠﻔﯽ، ﻣﻮﺟﺐ اﻓﺰاﯾﺶ ﻧﺮخ ﻓﺮﺳﺎﯾﺶ ﺧﺎك ﺳﻄﺤﯽ ﻣﯽﺷﻮد. اﯾﻦ ﻓﺮاﯾﻨﺪ ﺑﺮاي ﺳﺎلﻫﺎي ﻃﻮﻻﻧﯽ ﺑﺎﻋﺚ ﺑﺮﻗﺮاري ﻧﺮخ ﻓﺮﺳﺎﯾﺸﯽ ﺑﺎﻻ و ﻫﺪر رﻓﺖ 0/1 ﺳﺎﻧﺘﯽﻣﺘﺮ ﺧﺎك در ﺳﺎل ﺷﺪه اﺳﺖ.

The method employed in this study was based on experimental research and field study. In this method, the stored radiocesium of the forest region which was supposed to be converted into Poplar plantation has been compared with the stored radiocesium of the reference region. 11 core samples were taken from reference region and then 7 core samples were selected from the transect which was a part of Poplar plantation that were taken by topographic characteristics in a depth of 25 centimeters, Having prepared the core samples according to the IAEA, they were packaged into the special Gama spectrometer containers. After that the amount of radiocesium of all samples has been measured by Bq kg-1 scale. The findings revealed that the amount of radiocesium in reference region was computed as 5894.1. Bq m-2 y-1. In the present study, soil loss rate during transect was estimated using proportional conversion models and mass balance I and II of 18.70, 22.72 and 18.64 ton / ha, respectively. These values were obtained for slope of 10-20%, canopy cover of 25% and clay loam soil under 1000 mm precipitation. This study recommended mass balance model II for estimation of erosion in changed land use areas and concluded that forest land use change to plantation due to reduction of long soil cover and plantation management by removing other seedlings and herbaceous cover increased the rate of soil erosion occurs. This process for many years has caused the erosion rate to exceed and has caused the loss of 0.1 cm of soil per year.