تدوین راهبردهای پایداری زیرساخت‎های سبز شهری با استفاده از ارزیابی تغییرات سیمای سرزمین (مطالعه موردی: منطقه دو کلان‌شهر تهران)

توسعه افسارگسیخته کالبدی - فضایی شهرها، باعث تغییر پوشش اراضی و ازدست‌رفتن انسجام زیرساخت‎های سبز می‎شود. همواره در شهرها این خطر وجود دارد که پایداری این زیرساخت‎ها در مقایسه با توسعه شهری نادیده گرفته شود. این زیرساخت‎ها (اراضی رودکناری، باغ‎ها، پارک‎های شهری، سبز راه‌های دست کاشت و اراضی بایر) با حضور در درون و پیرامون شهرها، می‎توانند خدمات اکوسیستمی بی‎شماری را عرضه نمایند که در صورت ازدست‌رفتن غیرقابل‌جایگزین خواهند بود. به‌این‌ترتیب، شناخت روند تغییرپذیری به‌منظور هدایت برنامه‎ریزی و مدیریت سیمای سرزمین شهری ضروری است. هدف این پژوهش، ارزیابی و پیش‎بینی تغییرات پوشش اراضی، سنجش تغییرات ساختار سیمای سرزمین و سپس پیشنهاد راهبردهای پایداری زیرساخت‎های سبز به‌منظور هدایت مدیریت سیمای سرزمین در منطقه دو کلان‌شهر تهران است. این منطقه از گذشته به دلیل گذر دو رود - دره درکه و فرحزاد موقعیت ممتازی نیز داشته است. در این پژوهش به‌منظور تهیه نقشه‎ پوشش‎های مختلف اراضی، از تصاویر ماهواره‎ای سال‎های 1986، 2000 و 2016 و نرم‎افزار idrisi استفاده شده است. همچنین برای پیش‎بینی پوشش اراضی سال 2032، زنجیره مارکوف و همان نرم‎افزار به کار گرفته شده است. بر اساس هدف این پژوهش، سه‌طبقه فضای سبز، فضای باز و فضای انسان‎ساخت موردنظر بوده و دوطبقه فضای سبز و فضای باز به‌عنوان زیرساخت سبز تلقی شده است. همچنین به‌منظور تحلیل تغییرات ساختاری، از محاسبه سنجه‎های np، mps، mpar، contig، mesh، split، lp، pland و division در نرم‎افزار fragstats استفاده شده است. در مجموع طی سال‎های 1986 تا 2016، به ترتیب حدود 617 هکتار از اراضی سبز و 1100 هکتار از اراضی باز به اراضی انسان‎ساخت تبدیل شده‎اند. باتوجه‌به یافته‎ها که بیانگر جایگزین‌شدن گسترده زیرساخت‎های سبز توسط اراضی ساخته شده و ازدست‌رفتن انسجام آن‎ها است، راهبردهایی بر اساس پنج اصل اکولوژی سیمای سرزمین پیشنهاد شده است.

formulating sustainability strategies for urban green infrastructures by using the landscape changes assessment (tehran metropolitan district 2)

unbridled physical-spatial development of cities causes changes in land cover and loss of coherence of green infrastructure. one hazard in cities is that the sustainability of these infrastructures is neglected in comparison to urban development. the presence of these infrastructures (riverside lands, gardens, urban parks, agricultural greens, and wastelands) in and around cities can provide countless ecosystem services that would be irreplaceable if lost. in this way, it is necessary to know the process of urban landscape changing to guide planning and management. this research aimed to evaluate and predict the changes in land cover, measure the changes in the landscape structure, and then propose green infrastructure sustainability strategies to guide the landscape management in district 2 in the tehran metropolitan. this region always had a privileged position due to the crossing of two river valleys (darakeh and farahzad). in this research, satellite images of1986, 2000, and 2016 years were used to prepare maps of different land covers by idrisi software. also, the ca-markov chain was used to predict land cover for 2032 year. according to the purpose, three classes (green space, open space, and man-made space) were considered. green and open spaces are green infrastructures. also, for analysing the structural changes, it has been calculated landscape metrics (np, mps, mpar, contig, mesh, split, lp, pland, and division) by fragstats software. in total, during the years 1986 to 2016 years, respectively about 617 ha of green lands and 1100 ha of open lands have turned into man-made lands. according to the results that show the widespread replacement of green infrastructures by man-made lands and the loss of their integrity, strategies based on the five principles of landscape ecology have been proposed.extended abstract1-introductionby being present in and around cities, green infrastructures (riparian lands, gardens, urban parks, cultivated greenways, and open lands) can offer countless ecosystem services that will be irreplaceable if lost. there are still no guidelines or laws for this relatively new concept at the global level or even at the national level. therefore, it is necessary to explain the alternative and requirements of maintaining, organizing, and improving the integrity state of green infrastructures for the stakeholders and decision-makers of the landscape at the local level. undoubtedly, the result of developing man-made land use can be seen at a very high speed compared to the effects of management measures for supporting green infrastructure. so, there is always a risk in cities about the protection of these infrastructures will be neglected compared to the development of other land uses (especially housing and roads). in this way, it is necessary to know the process of urban landscape change to guide green infrastructure planning and management with an emphasis on the strong theoretical foundations of landscape ecology and the principles related to the relationship between structure and function in the landscape matrix. this research aimed to evaluate and predict the changes in land cover, measure the changes in the landscape structure, and then propose green infrastructure sustainability strategies in order to guide the landscape management in district 2 in the tehran metropolitan. this region always had a privileged position due to the presence of two river valleys (darakeh and farahzad) and also proximity to the alborz mountain range. also, this area includes other significant natural and semi-natural elements such as hills, large and small urban parks, and gardens which are the reasons for choosing this area for study2-materials and methodsin this research, satellite images of 1986, 2000, and 2016 years were used to prepare maps of different land covers. these satellite images have been classified using training samples and the supervised classification method and the maximum likelihood algorithm using idrisi software. also, this software and land cover maps of 2000 and 2016 years have been used to predict land cover changes for 2032 year. in this regard, the simulation has been done with the ca-markov chain method and is based on the matrix of the probability of conversion of land uses to each other. in addition, the automatic cells method has been used to locate the predicted land cover. according to the purpose of this research, three levels of green space, open space, and man-made space are intended, and two levels of green space and open space are considered green infrastructure. also, the basis of the analysis of structural changes in this research is the land cover maps that are used at the class level by fragstats software for the measurements of the number of patches (np), men patch size (mps), mean perimeter to area ratio (mpar), mean contiguity index. (contig), effective mesh size (mesh), perforation (split), largest patch (lp), percentage of landscape (pland), and division (d) have been calculated.3- results and discussionin total, during the years 1986 to 2016 years, respectively about 617 ha of green lands and 1100 ha of open lands have turned into man-made lands. it is predicted that about 150 ha of green land will be converted into man-made land, while only about 60 ha will be added to the former green space in 2032. results show the widespread replacement of green infrastructures by man-made lands and the loss of their integrity, fifteen strategies are presented in five categories of landscape ecology principles, including 1) preserving and strengthening the size of patches, 2) preserving and strengthening the connection of patches and corridors, 3) strengthening the shape of patches, and 4) preserving the natural pattern of the river valleys and their edges and 5) preserving the natural buffer of the river valleys against disturbing factors. the method and principles used in this research can play an effective role in establishing a monitoring system and controlling the changes in the landscape structure for the sustainability of urban green infrastructures, improving their ecological functions and the quality of urban life.4- conclusionthe planning of urban green infrastructure requires such evaluations of the state of the landscape structure and its future prediction. the development of strategies and framework of future management measures to correct and improve the state of the natural and semi-natural landscapes could be based on the proposed principles and suggested strategies of this research.