تأثير پوشش لاشبرگ و مازاد مقطوعات بر مقدار رواناب و رسوب در ترانشه هاي خاكبرداري و خاكريزي جاده هاي جنگلي

Effects of litter cover and residuals on runoff and sediment in the cut slope and fill slope of forest roads

اﺣﺪاث ﺟﺎدهﻫﺎي ﺟﻨﮕﻠﯽ ﯾﮑﯽ از ﻋﻮاﻣﻞ ﻧﺎﭘﺎﯾﺪاري داﻣﻨﻪﻫﺎي ﺷﯿﺒﺪار اﺳﺖ ﮐﻪ ﺳﺒﺐ ﻓﺮﺳﺎﯾﺶ ﺧﺎك و آﺛﺎر ﻧﺎﺷﯽ از آن ﻣﯽﺷﻮد. ﻫﺪف اﯾﻦ ﭘﮋوﻫﺶ، ﺑﺮرﺳﯽ ﺗﺄﺛﯿﺮ ﭘﻮﺷﺶ ﻻﺷﺒﺮگ و ﻣﺎزاد ﻣﻘﻄﻮﻋﺎت ﺑﺮ ﻣﻘﺪار رواﻧﺎب و رﺳﻮب در ﺗﺮاﻧﺸﻪﻫﺎي ﺧـﺎﮐﺒﺮداري و ﺧﺎﮐﺮﯾﺰي ﺟﺎدهﻫﺎي ﺟﻨﮕﻠﯽ در ﺟﻨﮕﻞﻫﺎي اﺳﺘﺎن ﮔﯿﻼن ﺑﻮد. ﺑﺪﯾﻦ ﻣﻨﻈﻮر ﭼﻬﺎر ﺗﺮاﻧﺸﮥ ﺧﺎﮐﺒﺮداري و ﺧـﺎﮐﺮﯾﺰي اﻧﺘﺨـﺎب و در ﻫﺮ ﺗﺮاﻧﺸﻪ، ﭼﻬﺎر ﭘﻼت 2 ﻣﺘﺮﻣﺮﺑﻌﯽ ﺷﺎﻣﻞ ﺑﺪون ﭘﻮﺷﺶ )ﻃﺒﻘﮥ 1(، ﭘﻮﺷﺶ 30 درﺻﺪ )ﻃﺒﻘﮥ 2(، ﭘﻮﺷﺶ 60 درﺻﺪ )ﻃﺒﻘﮥ 3( و ﭘﻮﺷﺶ 90 درﺻﺪ )ﻃﺒﻘﮥ 4( و ﺑﺎ ﺷﯿﺐ ﺛﺎﺑﺖ 30 درﺻﺪ ﺑﺮداﺷﺖ ﺷﺪ. اﻧﺪازهﮔﯿﺮي ﻧﻤﻮﻧﻪﻫﺎ ﭘﺲ از ﻫﺮ ﺑﺎر ﺑﺎرش ﺑﺎ ﺷﺪت ﺗﻘﺮﯾﺒﯽ 80 ﻣﯿﻠﯽﻣﺘﺮ در ﺳﺎﻋﺖ اﻧﺠﺎم ﮔﺮﻓﺖ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﻣﯿﺎﻧﮕﯿﻦ رواﻧﺎب ﺗﻮﻟﯿﺪي در ﺗﺮاﻧﺸﮥ ﺧﺎﮐﺒﺮداري در ﭘﻼتﻫﺎي ﺑﺎ ﭘﻮﺷﺶ ﺻﻔﺮ )ﮐﻨﺘﺮل(، 30، 60 و 90 درﺻﺪ ﺑﻪﺗﺮﺗﯿﺐ 759/3، 748/6، 372/6 و 196/0 ﻣﯿﻠﯽﻟﯿﺘﺮ در ﻣﺘـﺮ ﻣﺮﺑـﻊ، در ﺗﺮاﻧﺸـﮥ ﺧـﺎﮐﺮﯾﺰي ﺑﻪﺗﺮﺗﯿﺐ 216/6، 156/6، 77/1 و 69/5 ﻣﯿﻠﯽﻟﯿﺘﺮ در ﻣﺘﺮﻣﺮﺑﻊ و ﻣﯿﺎﻧﮕﯿﻦ رﺳـﻮب در ﺗﺮاﻧﺸـﮥ ﺧـﺎﮐﺒﺮداري در ﻃﺒﻘـﺎت ﻣﺨﺘﻠـﻒ ﺑﻪﺗﺮﺗﯿﺐ 1/08، 0/96، 0/13 و 0/07 ﮔﺮم در ﻟﯿﺘﺮ و در ﺗﺮاﻧﺸﮥ ﺧـﺎﮐﺮﯾﺰي ﺑـﻪﺗﺮﺗﯿﺐ 1/51، 1/06، 0/27 و 0/08 ﮔـﺮم در ﻟﯿﺘـﺮ ﺑﺮآورد ﺷﺪ. ﻧﺘﺎﯾﺞ ﺗﺠﺰﯾﮥ وارﯾﺎﻧﺲ ﻧﺸﺎن داد ﮐﻪ اﺧﺘﻼف ﻣﻌﻨﯽداري ﺑـﯿﻦ ﻣﻘـﺪار رواﻧـﺎب و رﺳـﻮب اﯾﺠﺎدﺷـﺪه در ﺷـﺪتﻫﺎي ﻣﺨﺘﻠﻒ ﭘﻮﺷﺶ ﻻﺷﺒﺮگ و ﻣﺎزاد ﻣﻘﻄﻮﻋﺎت وﺟﻮد دارد )0/05

One of the causes of instability of sloping hillsides is the construction of forest roads, which leads to soil erosion and its effects. The purpose of this study was to study the effects of litter cover and residuals on runoff and sediment in the cut slope and fill slope of forest roads in the forests of Guilan province. For this purpose, four cut slopes and fill slope were selected and in each of them, four plots (2 m2) with four litter cover and residuals including without cover, 30%, 60% and 90% and with a fixed slope of 30% was measured. Samples were measured after each rainfall with an approximate intensity of 80 mm/h. The results showed that the mean of runoff in the cut slope were 759.3, 748.6, 372.6 and 196 ml/m2, in the fill slope were 216.6, 156.6, 77.1 and 69.5 ml/m2, respectively. Mean of sediment in the cut slope were 1.08, 0.96, 0.13 and 0.07 g/l, in the fill slope were 1.51, 1.06, 0.27 and 0.08 g/l, respectively. The results of analysis of variance showed that there was a significant difference between the amount of runoff and sediment created in the litter cover and residuals classes (P<0.05). The mean of runoff produced in the cut slope was significantly (P<0.05) higher than their mean in the fill slope in all cover percentages. Results of the study showed that litter cover and residuals had a significant effect on reducing runoff and sediment in forests roads.