ارزيابي تغييرات كاربري اراضي در حوضه آبخيز رودخانه تجن با تكيه بر سنجه هاي سيماي سرزمين

Assessment of Land Changes in Tajan River Watershed with Emphasis on Landscape Metrics

ﻣﻘﺪﻣﻪ: ﺗﻐﯿﯿﺮات ﮐﺎرﺑﺮي اراﺿﯽ و ﺗﺨﺮﯾﺐ ﭘﻮﺷﺶ ﻫﺎي ﻃﺒﯿﻌﯽ ﺳﺒﺐ اﺧﺘﻼل در اﮐﻮﺳﯿﺴﺘﻢ و ﮐﺎﻫﺶ ﺗﻨﻮع زﯾﺴﺘﯽ ﻣﯽ ﺷﻮد. ﮐﺎﻫﺶ ﺟﻨﮕﻞﻫﺎي ﻫﯿﺮﮐﺎﻧﯽ ، ﻣﺘﻌﻠﻖ ﺑﻪ دوره ژوراﺳﯿﮏ از ارزشﻣﻨﺪﺗﺮﯾﻦ ﺟﻨﮕﻞﻫﺎي ﺟﻬﺎن، ﯾﮑﯽ از ﻣﻬﻢﺗﺮﯾﻦ ﻣﺸﮑﻼت در ﺳﺎلﻫﺎي اﺧﯿﺮ اﺳﺖ. روش ﺗﺤﻘﯿﻖ: در ﭘﮋوﻫﺶ ﺣﺎﺿﺮ ﺑﺎ اﺳﺘﻔﺎده از ﺗﺼﺎوﯾﺮ ﻣﺎﻫﻮاره اي ﺑﻪ ﺑﺮرﺳﯽ ﺗﻐﯿﯿﺮات ﮐﺎرﺑﺮي اراﺿﯽ و ﺗﺠﺰﯾﻪ وﺗﺤﻠﯿﻞ ﺳﯿﻤﺎي ﺳﺮزﻣﯿﻦ در دوره ﻫﺎي زﻣﺎﻧﯽ ﻣﺨﺘﻠﻒ، ﺷﺎﻣﻞ ﺳﺎل ﻫﺎي 1984، 2001 و 2010 ﭘﺮداﺧﺘﻪ ﺷﺪ. ﺟﻬﺖ ﺑﺮرﺳﯽ ﭼﮕﻮﻧﮕﯽ روﻧﺪ ﺗﻐﯿﯿﺮات ﮐﺎرﺑﺮي و ﺳﯿﻤﺎي ﺳﺮزﻣﯿﻦ در اﻓﻖ زﻣﺎﻧﯽ آﯾﻨﺪه از ﻣﺪل ﺳﺎز ﺗﻐﯿﯿﺮ ﺳﺮزﻣﯿﻦ )LCM( اﺳﺘﻔﺎده ﺷﺪ. ﺳﻨﺠﻪ ﻫﺎي ﺳﯿﻤﺎي ﺳﺮزﻣﯿﻦ در ﻧﺮم اﻓﺰار FRAGSTATS 4/2 اﺳﺘﺨﺮاج ﺷﺪﻧﺪ. ﻧﺘﺎﯾﺞ و ﺑﺤﺚ: ﻧﺘﺎﯾﺞ ﻧﺸﺎن ﻣﯽ دﻫﺪ ﮐﻪ ﺟﻨﮕﻞ، ﮐﺎرﺑﺮي ﻏﺎﻟﺐ )72 درﺻﺪ از ﻣﺴﺎﺣﺖ ﻣﻨﻄﻘﻪ در ﺳﺎل 1984 و 46 درﺻﺪ در ﺳﺎل 2040( در ﻣﻨﻄﻘﻪ ﻣﻮردﻣﻄﺎﻟﻌﻪ اﺳﺖ. در ﺳﺎل 1984 ﻣﺴﺎﺣﺖ ﺟﻨﮕﻞ ﻫﺎ 8/4 ﺑﺮاﺑﺮ ﮐﺎرﺑﺮي ﮐﺸﺎورزي ﺑﻮد و اﯾﻦ ﻣﯿﺰان ﺑﻪ 1/8 ﺑﺮاﺑﺮ در ﺳﺎل 2040 ﺧﻮاﻫﺪ رﺳﯿﺪ. ﺷﺎﺧﺺ ﺑﺰركﺗﺮﯾﻦ ﻟﮑﻪ )LPI( ﻧﺸﺎن داد اراﺿﯽ ﺟﻨﮕﻠﯽ ﭘﻮﺷﺶ ﻏﺎﻟﺐ در ﮐﻞ دوره اﺳﺖ. ﻫﻢﭼﻨﯿﻦ ﺷﺎﺧﺺ ﻧﺰدﯾﮑﯽ )PROX( در ﮐﺎرﺑﺮي ﮐﺸﺎورزي و ﻣﺮﺗﻊ در دوره 2010-1984 روﻧﺪ اﻓﺰاﯾﺸﯽ داﺷﺘﻪ و اﯾﻦ ﻣﯿﺰان در ﺳﺎل 2040 اﻓﺰاﯾﺶ ﺑﯿﺶﺗﺮي ﺧﻮاﻫﺪ ﯾﺎﻓﺖ. ﻫﻢﭼﻨﯿﻦ اﻓﺰاﯾﺶ ﺳﻨﺠﻪ ﺗﺮاﮐﻢ ﺣﺎﺷﯿﻪ )ED( در ﻃﯽ دوره آﯾﻨﺪه در ﻫﺮ ﺳﻪ ﮐﺎرﺑﺮي ﻣﺮﺗﻊ، ﺟﻨﮕﻞ و ﮐﺸﺎورزي ﻧﺸﺎن ﻣﯽدﻫﺪ ﮐﻪ ﺣﻮﺿﻪ ﺗﺠﻦ ﺧﯿﻠﯽ ﻣﺘﻔﺎوت ﺗﺮ از ﺣﺎل ﺣﺎﺿﺮ ﺧﻮاﻫﺪ ﺷﺪ . اﯾﻦ ﻧﺘﺎﯾﺞ ﻣﯽ ﺗﻮاﻧﻨﺪ دﯾﺪﮔﺎه ﻫﺎﯾﯽ در ﺟﻬﺖ اوﻟﻮﯾﺖ ﺑﻨﺪي ﺗﺼﻤﯿﻤﺎت ﻣﻠﯽ و ﻣﻨﻄﻘﻪاي ﺑﺎ ﻫﺪف ﮐﺎﻫﺶ ﺗﺨﺮﯾﺐ ﺟﻨﮕﻞﻫﺎ در اﺧﺘﯿﺎر ﻣﺪﯾﺮان ﻗﺮار دﻫﺪ.

Introduction: Land cover and its configuration in the landscape are crucial components in the provision of biodiversity and ecosystem services. Hyrcanian forests have a long history (arising in the Jurassic Period) and are among the world's most valuable forests; the decline in the Hyrcanian forests is one of the most serious problems of recent years. Material & Method: This study aims at comparing multi-temporal land use and landscape pattern analysis using satellite images from 1984, 2001 and 2010. Land use and spatial structures were predicted for future time horizons in the Tajan Watershed by land change modeler (LCM). Also, the landscape patterns were calculated by FRAGSTATS 4.2. Result & Discussion: The results show that forest was the dominant land cover (72% of area in 1984 and 46% in 2040) in the study area. The total area of forest was 8/4 times higher than the agriculture land cover in 1984 and 1.8 times in 2040. The Largest patch Index (LPI) shows forest lands as dominant cover in the whole period. Also proximity index (PROX) in agriculture and pasture land use increase during 1984 to 2040. The Edge density (ED) will increase in the future for three land uses. The edge density will increase at forest land use from 2010 to 2040. An informed vision on past, present and future forest area dynamics may help guide and prioritize international decisions aimed at reducing forest loss.