تأثیر اندازة همسایگی بر متغیرهای مرفومتریک و رابطة آن‌ها با پوشش گیاهی در سه زیر حوزة آبخیز متفاوت از منظر ژئومرفولوژیکی و اقلیمی در جنوب غرب ایران

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتری گروه خاکشناسی دانشکده کشاورزی دانشگاه شهید چمران اهواز اهواز ایران

2 استادیار گروه خاکشناسی، دانشکده کشاورزی، دانشگاه شهید چمران اهواز، ایران

چکیده

هدف این پژوهش بررسی اهمیت مقیاس همسایگی در مدل‌سازی رابطة پوشش گیاهی و متغیرهای مرفومتریک به کمک الگوریتم درخت رگرسیونی و طبقه‌بندی (CART) در جنوب غرب ایران است. برای این هدف، شاخص پوشش گیاهی اصلاح شده (MSAVI2) از یک تصویر لندست 8 محاسبه گردید و استخراج هشت متغیر مرفومتریک با به‌کارگیری روش Wood در چهار مقیاس همسایگی (90×90، 150×150، 210×210 و 270×270 متر) از یک مدل رقومی ارتفاع  SRTM با وضوح مکانی 30 متر انجام پذیرفت. نتایج آزمون کروسکال - والیس تأیید کرد که در برخی از زیر حوزه‌های آبخیز تغییر مقیاس همسایگی می‌تواند تأثیری معنادار بر گرادیان شیب، انحنای پروفیل، سطح ویژة آبخیز، عامل LS و شاخص خیسی توپوگرافیک بگذارد. نتایج این مطالعه نشان داد که در هر زیر حوزة آبخیز متغیرهای مرفومتریک متفاوتی با توزیع مکانی شاخص MSAVI2 بیش‌ترین ارتباط را دارند و مقدار ضریب همبستگی اسپیرمن بین آن‌ها به میزان کمی تحت‌تأثیر مقیاس همسایگی می‌باشد. مدل‌های CART مبتنی بر شاخص MSAVI2 و متغیرهای مرفومتریک محاسبه شده در مقیاس همسایگی 270×270 متر به ترتیب با میزان ضریب کاپای 55/0 و 78/0 دارای بهترین عملکرد در طبقه‌بندی تیپ‌های گیاهی بودند. ارتفاع هموار شده که کم‌ترین تأثیر را از مقیاس همسایگی دارد، به‌عنوان مهم‌ترین پیش‌بینی‌کننده در مدل CART شناسایی شد ولی افزایش مقیاس همسایگی منجر به بیشتر شدن اهمیت دیگر متغیرهای مرفومتریک به‌ویژه گرادیان شیب در طبقه‌بندی تیپ‌های گیاهی و نهایتاً ارتقاء دقّت مدل CART گردید. نتایج کلی این پژوهش بیانگر آن می‌باشد که کاربرد آنالیز چند مقیاسی ژئومرفومتریک باتوجه‌به ژئومرفولوژی منطقة مطالعاتی می‌تواند عملکرد مدل‌های پیش‌بینی مرتبط با پوشش گیاهی را به میزان مناسبی افزایش دهد. 

کلیدواژه‌ها


عنوان مقاله [English]

Effect of Neighborhood Size on Morphometric Variables and Their Relationship with Vegetation Cover within Three Geomorphologically and Climatically Different Sub-Watersheds in Southwest Iran

نویسندگان [English]

  • Javad Khanifar 1
  • Ataallah Khademalrasoul 2
1 Department of soil science, ّFaculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran.
2 Assistant Professor of Soil Science Department, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran
چکیده [English]

The aim of this research was to study the importance of the neighborhood scale in modeling the relationship between vegetation cover and morphometric variables using the classification and regression trees algorithm (CART) in southwestern of Iran. For this purpose, the second Modified Soil-Adjusted Vegetation Index (MSAVI2) was calculated from a Landsat 8 image, and eight morphometric variables were derived using the Wood method in four neighborhood scales (90×90, 150×150, 210×210, and 270×270 m) from a 30 m SRTM digital elevation model. The results of the Kruskal-Wallis test confirmed that in some sub-watersheds, neighborhood-scale change can have a significant effect on slope gradient, profile curvature, specific catchment area, LS factor, and topographic wetness index. The results showed that in each sub-watershed different morphometric variables are most related to the spatial distribution of the MSAVI2 index and the value of the Spearman correlation coefficient between them is slightly affected by the neighborhood scale. CART models based on the MSAVI2 index and 270×270 m morphometric variables with a kappa coefficient of 0.55 and 0.78, respectively, had the best performance in classifying vegetation types. The elevation smoothed, which is the least affected by the neighborhood scale, was recognized as the most important predictor in the CART model. However upscaling led to the increasing importance of other morphometric variables, especially slope gradient, in classifying vegetation types and finally improving the accuracy of the CART model. Overall, the present results indicate that the application of multi-scale geomorphometric analysis with respect to the geomorphology of the study area can improve the performance of prediction models related to vegetation cover to an appropriate extent.

کلیدواژه‌ها [English]

  • vegetation cover
  • geomorphometry
  • neighborhood scale
  • Classification and Regression Trees (CART)
Abdi, H., Heshmati, G. A. and Mostafalou, H. (2013). The study and comparison of the vegetation at elevation gradient in two medium and cold steppe zones in northeastern part of Golestan province. Plant Ecosystem Conservation, 1 (2), 59-70. (In Farsi)
Albani, M., Klinkenberg, B., Andison, D. W. and Kimmins, J. P. (2004). The choice of window size in approximating topographic surfaces from digital elevation models. International Journal of Geographical Information Science, 18(6), 577-593.
A-Xing, Z., Burt, J. E., Smith, M., Rongxun, W. and Jing, G. (2008) The impact of neighborhood size on terrain derivatives and digital soil mapping. In Zhou, Q., Lees, B. and Tang, G. A. (Eds.), Advances in digital terrain analysis. (pp. 333-348). Springer, Berlin, Heidelberg.
Azarnivand, H. (1992). Investigation of vegetation cover and soil in relation to geomorphological units in Damghan. In: Proceedings of the seminar on the study of desert areas issues of Iran, Volume 1, Desert Research Center of Iran. (In Farsi)
Evans, I. S. (1979). Statistical characterization of altitude matrices by computer. An integrated system of terrain analysis and slope mapping. The final report on grant DA-ERO-591-73-G0040. Durham, UK: University of Durham.
Fattahi, B., Aghabeigi Amin, S., Ildoromi, A., Maleki, M.,  Hasani, J. and Sabetpour, T. (2009). Investigation of some environmental factors effective on Astragalus gossypinus in Zagros mountainous rangelands (case study: Geleh Bor rangelands of Hamadan Province). Journal of Rangeland, 3(2), 203-216. (In Farsi)
Florinsky, I. (2016) Digital terrain analysis in soil science and geology (Second ed.), Academic Press, Amsterdam.
Franklin, S. E. (2020). Interpretation and use of geomorphometry in remote sensing: a guide and review of integrated applications. International Journal of Remote Sensing, 41(19), 7700-7733.
Gharachorlou, M., Esfandiyari, F. and Dalal oghli, A. (2018). Regession analysis of geomorphic-vegetation cover relationships with emphasis on spatial scale (case study, Arsbaran catchments: naposhtehcay, ilghinehcay and mardanqumcay). Quantitative Geomorphological Research, 6(2), 79-98. (In Farsi)
Ghorbani, M., Gorji, M., Azarnivand, H., Arzani, H. and Ramk Masoumy, T. (2009). Soil, Topography Characteristics and Geology Effects on Distribution of Plants (Case Study: Ghazvin- Kohin Region). Jwmseir, 2 (5) :1-10. (In Farsi)
Huggett, R. and Cheesman, J. (2002) Topography and the Environment. Prentice Hall.
Ju, C., Cai, T. and Yang, X. (2008). Topography-based modeling to estimate percent vegetation cover in semi-arid Mu Us sandy land, China. Computers and electronics in agriculture, 64(2), 133-139.
Keyghobadi, M., Piri Sahragard, H., Pahlavan Rad, M., Karami, P. and Yari, R. (2020). Application of Generalized Additive Model and Classification and Regression Tree to Estimate Potential Habitat Distribution of Range plant species (Case Study: Khazri Rangelands of Beyaz Plain, Southern Khorasan). Iranian Journal of Range and Desert Research, 27(3), 561-576. (In Farsi)
 Khanifar, J. and Khademalrasoul, A. (2020). Multiscale comparison of LS factor calculation methods based on different flow direction algorithms in Susa Ancient landscape. Acta Geophysica, 68(3), 783-793.
Khanifar, J. and Khademalrasoul, A. (2021). Effects of neighborhood analysis window forms and derivative algorithms on the soil aggregate stability–Landscape modeling. CATENA, 198, 105071.
Lam, N. S. N. (2019) Resolution. In: Wilson J. P. (Ed.), The Geographic Information Science & Technology Body of Knowledge (2nd Quarter 2019 Edition). DOI: 10.22224/gistbok/2019.2.11.
Moradi, H. R. (1994). Investigation between geomorphology units, vegetation, and soil in the Vaz watershed. Masters dissertation, Tarbiat Moddares University, Iran. (In Farsi)
Olaya, V. (2009) Basic Land-Surface Parameters. In: Hengle, T. and Reuter, H.I. (Eds.), Geomorphometry: Concepts, Software, Applications. (pp. 141–170). Elsevier, Amsterdam.
Rigol-Sanchez, J. P., Stuart, N. and Pulido-Bosch, A. (2015). ArcGeomorphometry: a toolbox for geomorphometric characterisation of DEMs in the ArcGIS environment. Computers & Geosciences, 85, 155-163.
Roecker, S. M. and Thompson, J. A. (2010). Scale effects on terrain attribute calculation and their use as environmental covariates for digital soil mapping. In Boettinger, J. L., Howell, D. W., Moore, A. C., Hartemink, A. E. and Kienast-Brown, S. (Eds.). Digital soil mapping: Bridging research, environmental application, and operation. (pp. 55-66). Springer, Dordrecht.
Shokrollahi, J. (2009). Relationship between Vegetation Cover and Density with Geomorphologic Unit in a Part of Polur Summer Rangelands. Masters dissertation, Tarbiat Moddares University, Iran. (In Farsi)
Siegel, S. and Castellan, N. J. (1988) Nonparametric statistics for the behavioral sciences (2nd ed.) New York: McGraw-Hill.
Reports of justification studies of Watershed Management in the Remains of Dez Dam watershed. (n.d.). Natural Resources organization of Iran. (In Farsi)
Wilson, J. P. (2018) Environmental Applications of Digital Terrain Modeling. John Wiley & Sons.
Wood, J. (1996). The geomorphological characterisation of digital elevation models. Ph. D. dissertation, University of Leicester.
Young, M., (1978). Statistical Characterization of Altitude Matrices by Computer. Terrain Analysis: Program Documentation: Report 5 on Grant DA-ERO-591-73-G0040. Department of Geography, University of Durham, Durham, UK. 18 pp.
Zare Chahouki M.A, Mashghooli, M. and Hosein Jafari, S. (2016). Classification of Vegetation Cover related to Environmental Factors (Case study: Gharabagh Rangelands of Azarbaijan Province). Journal of Plant Research (Iranian Journal of Biology), 28(5), 995-1005. (In Farsi)
Zaremehrjardi, M., Ghodousi, J., Noruozi, A. and Lotfollazadeh, D. (2007). Analysis of the relationship between geopedologic characteristics with vegetation in Dagh-Finou catchment of Bandar Abbas. Pajouhesh & Sazandegi, 76, 144-150. (In Farsi)
Zhan, Z. Z., Liu, H. B., Li, H. M., Wu, W. and Zhong, B. (2012). The relationship between NDVI and terrain factors--a case study of Chongqing. Procedia Environmental Sciences, 12, 765-771.
Zhu, A. X. (2008) Keynote Paper: Spatial Scale and Neighborhood Size in Spatial Data Processing for Modeling the Natural Environment. In: Mount, N., Harvey, G., Aplin, P. and Priestnall, G. (Eds.), Representing, Modeling, and Visualizing the Natural Environment. (pp. 147–165). CRC Press.