تاﺛﯿﺮ ﭘﻮﺷﺶ ﮔﯿـﺎﻫﯽ ﺑﺮ ﻣﯿﺰان رواﻧﺎب و ﺗﻮﻟﯿﺪ رﺳﻮب در ﻣﻘﯿﺎس ﭘﻼت درﺣﻮزة آﺑﺨﯿﺰ ﺟﻨﮕﻞ ﺧﯿﺮود

The effects of vegetation cover on runoff and sediment yield in plot scale of Kheyrud Forest Watershed

ﺑﻬﺮهﺑﺮداري ﺣﻮزهﻫﺎي آﺑﺨﯿﺰ ﺟﻨﮕﻠﯽ ﯾﮑﯽ از ﻣﻮاردي اﺳــﺖ ﮐﻪ ﺑﺎﻋﺚ ﺗﻐﯿﯿﺮ ﺧﺼــﻮﺻــﯿﺎت ﻫﯿﺪروﻟﻮژﯾﮏ ﺟﻨﮕﻞ ﻣﯽﺷــﻮد. ﻟﮑﻦ ﭘﯿﺎﻣﺪﻫﺎي ﻫﯿﺪروﻟﻮژﯾﮏ ﻧﺎﺷﯽ از ﺑﻬﺮهﺑﺮداري ﺣﻮزهﻫﺎي آﺑﺨﯿﺰ ﺟﻨﮕﻠﯽ ﮐﻢﺗﺮ ﺑﺮرﺳﯽ ﺷﺪه اﺳﺖ. ﺑﺮ اﯾﻦ اﺳﺎس در ﺗﺤﻘﯿﻖ ﺣﺎﺿﺮ اﻗﺪام ﺑﻪ ﺑﺮرﺳﯽ ﺗﺄﺛﯿﺮ ﺗﻐﯿﯿﺮ ﭘﻮﺷـــﺶ ﮔﯿﺎﻫﯽ در اﺛﺮ ﺑﻬﺮهﺑﺮداري ﺟﻨﮕﻞ، ﺑﺮ ﻣﺆﻟﻔﻪﻫﺎي ﻫﯿﺪروﻟﻮژي در ﻣﻘﯿﺎس ﭘﻼتﻫﺎي دو ﻣﺘﺮ ﻣﺮﺑﻌﯽ و در ﻗﺎﻟﺐ ﭼﻬﺎر ﺗﮑﺮار ﻣﺒﺘﻨﯽ ﺑﺮ ﺑﺎرﻧﺪﮔﯽﻫﺎي ﻃﺒﯿﻌﯽ ﺑﻪ وﻗﻮع ﭘﯿﻮ ﺳﺘﻪ از آذر 1393 ﺗﺎ آذر 1394) ﻃﯽ ﯾﮑ ﺴﺎل( در ﺑﺨﺶ ﮔﺮازﺑﻦ ﺟﻨﮕﻞ آﻣﻮز ﺷﯽ و ﭘﮋوﻫ ﺸﯽ ﺧﯿﺮود، ﺷﺪه ا ﺳﺖ. ﺑﻪﻃﻮري ﮐﻪ ﺑﻌﺪ از ﻫﺮ واﻗﻌﻪ، ﺑﻌﺪ از ﻗﺮاﺋﺖ ﻣﻘﺪار ﺑﺎرش از ﺑﺎران ﺳﻨﺞ ﻧ ﺼﺐ ﺷﺪه در ﻣﻨﻄﻘﻪ، ﻣﯿﺰان رواﻧﺎب و ﻣﯿﺰان ر ﺳﻮب ﺑﻪد ﺳﺖ آﻣﺪ. ﻧﺘﺎﯾﺞ ﺗﺤﻘﯿﻖ ﺑﯿﺎنﮔﺮ ﺗﺄﺛﯿﺮ ﻣﻌﻨﯽدار (0/01≤P) ﺗﻐﯿﯿﺮ ﭘﻮ ﺷﺶ ﮔﯿﺎﻫﯽ در اﺛﺮ ﺑﻬﺮهﺑﺮداري، ﺑﺮ ﻣﯿﺰان رواﻧﺎب و ر ﺳﻮب اﺳﺖ وﻟﯽ ﺗﺄﺛﯿﺮ ﻃﺒﻘﮥ ﺷﯿﺐ ﺑﺮ ﻣﯿﺰان رواﻧﺎب و رﺳﻮب ﻣﻌﻨﯽدار ﻧﯿﺴﺖ. ﮐﻤﺘﺮﯾﻦ ﻣﯿﺰان رواﻧﺎب و رﺳﻮب ﺑﻪ ﺗﺮﺗﯿﺐ در ﻣﻨﻄﻘﮥ ﺷﺎﻫﺪ(ﺑﺪون ﺑﻬﺮهﺑﺮداري) 372/331 ﺳﯽ ﺳﯽ و 0/08 ﮔﺮم ﺑﺮ ﻣﺘﺮﻣﺮﺑﻊ و ﻣﻨﻄﻘﮥ ﺑﻬﺮهﺑﺮداري ﺷﺪه ﺑﻪ روش ﺗﮏ ﮔﺰﯾﻨﯽ 878/96 ﺳﯽ ﺳﯽ و 0/17 ﮔﺮم ﺑﺮﻣﺘﺮﻣﺮﺑﻊ و ﺑﯿ ﺸﺘﺮﯾﻦ ﻣﯿﺰان ﺗﻮﻟﯿﺪ رواﻧﺎب و ر ﺳﻮب ﻣﺮﺑﻮط ﺑﻪ ﻣ ﺴﯿﺮ ﭼﻮﺑﮑ ﺸﯽ ا ﺳﺖ ﮐﻪ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﻪ ﻣﯿﺰان 2290/70 ﺳﯽ ﺳﯽ و 1/2 ﮔﺮم ﺑﺮ ﻣﺘﺮﻣﺮﺑﻊ ﻣﯽﺑﺎﺷﺪ. ﻫﻤﭽﻨﯿﻦ رواﺑﻂ رﮔﺮﺳﯿﻮﻧﯽ ﺑﯿﻦ ﻣﯿﺰان ﺑﺎرﻧﺪﮔﯽ، ﺗﻮﻟﯿﺪ رواﻧﺎب و رﺳﻮب ﻧﺸﺎن داد ﮐﻪ راﺑﻄﮥ ﻣﺜﺒﺖ و ﻣﻌﻨﯽداري ﺑﯿﻦ ﺑﺎرﻧﺪﮔﯽ و رواﻧﺎب و رﺳﻮب وﺟﻮد دارد و ﺑﺎ اﻓﺰاﯾﺶ ﺑﺎرﻧﺪﮔﯽ، ﻣﯿﺰان رواﻧﺎب و رﺳﻮب اﻓﺰاﯾﺶ ﻣﯽﯾﺎﺑﺪ.

Land cover is also important factor for protecting the soil against erosion. A fully forested watershed experiences relatively little surface erosion, but timber harvest alters the canopy cover, exposing the soil to water and wind. Forests provide the maximum amount of soil protection. Reduction of vegetative cover by forest harvesting generally increases the average surface runoff volume and sediment While, the hydrologic response of forest harvesting has been rarely considered. Towards this attempt, the present study has been conducted to investigate the effect of vegetation cover on hydrological components in plot scale (2m*1m) with four replicates in tow slope scale (0-20%, 20-40%) in Kheyrud Forest of Iran during December 2014 until December 2015. The rain depth was measured by using a rain gauge installed in the study area. The runoff volume and sediment yield were also measured through field data collection and lab analyses by weighting and decantation methods. The results of the study showed significant effects of vegetation cover (P ≤0.01) on runoff volume and sediment yield. Natural forest without harvesting, forest with selective harvesting treatments exhibited the lowest amounts of runoff and sediments, with averages of 372.31, 878.96 cc, and 0.08, 0.17 gr m-2 respectively, in comparison to other treatments. Linear regression among mentioned parameters (precipitation, runoff, and sediment) were determined. The results show that there were significant correlation and linear regression among precipitation, runoff and sediment.