Vegetation cover

Open Access Article

1 - Survey of Flood water Spreading on quantitative changes of Vegetation Cover and Groundwater Recharge by Remote Sensing and GIS in Tasouj Aquifer in East Azarbayjan
Hossein Saadati Maghsoud Khayyam

One of the methods for water supplying and control of drying and flood is theapplication of water flooding. The work reported here was conducted at theexperimental station located in Tassuj plain, 110 km north-west of Tabriz in thenorthern of Oroumiye lake, situated bet More

One of the methods for water supplying and control of drying and flood is theapplication of water flooding. The work reported here was conducted at theexperimental station located in Tassuj plain, 110 km north-west of Tabriz in thenorthern of Oroumiye lake, situated between 45°18 to 45° 33E and 38° 15 to 38° 24 N,with an average annual precipitation of 362.3 mm, and average annual evaporation of989.5 mm. The study basin has an area of 5590 km2 with 3000 km2 on which floodspreading is possible. The aims of this research are investigation of efficacy of FloodSpreading Project (FSP) on vegetation cover and recharge of groudwater in Tassujstation. Remote sensing and GIS systems are effective and efficient techniques inwatershed management and investigation flood distribution in plains. After preparingmentioned parameters in GIS environment (using Arc GIS software), digital maps andtwo satellite images TM (1992) and ETM (2002, 2006) of the study area from floodspreading of Tassuj was used. Images were interpretated by Hybrid or optic method oncomputer monitor. The results were indicated that vegetation cover increased afterFlood Spreading Project equal 18% to 34% in 1378 to 1384 year. Bare soil decreasesin 9 years at last too. Deposit of drying, groundwater level does not decrease but alsodischarge of wells was increased. Study of unit hydrograph of Tassuj plain wasdeterminated that groundwater level decreases equal 10 meters in 1373 to 1380 butafter flood spreading in the1380 year it increased. Manuscript profile

Open Access Article

2 - Investigating indices of soil surface erosion and their relations to slope characteristics in semi-arid rangelands
علی رضا واعظی زهرا بیات مجید فرومدی

Surface erosion is a one of the major factors of soil degradation and gradual decline in soil productivity. Little studies have been done on the surface erosion indices in the semi-arid rangelands. Therefore, this study was conducted to quantify surface soil erosion ind More

Surface erosion is a one of the major factors of soil degradation and gradual decline in soil productivity. Little studies have been done on the surface erosion indices in the semi-arid rangelands. Therefore, this study was conducted to quantify surface soil erosion indices using the land characteristics in a semi-arid region. Five southern hillslopes with different slope gradients (9, 13, 17, 31 and 33%) which subjected to surface erosion were selected in Zanjan province. Soil samples were collected from two depths (0-5 and 5-15 cm) in four locations at a 2-m distance along the slope at two replications. A total of 80 soil samples were collected for analyzing particle size distribution. Soil surface erosion indices were determined using the proportion of particle diameter for given frequency in surface and sub-surface soils. Toward this, the proportion of particle diameter in the frequency of 40 (d401/d402), 50 (d501/d502), 60 (d601/d602) and 70 % (d701/d702) was computed. Additionally, proportions of mean weight diameter (MWDp1/MWDp2), geometric mean diameter (dg1/dg2) and geometric standard deviation (δg1/δg2) of surface and subsurface soils particles were determined. Based on the results, significant differences were found among the hillslopes in all soil surface erosion indices, whereas the differences for the locations along the hillslopes were not statistically significant. In the steep slopes, the frequency of fine particles (silt and clay) and organic matter content was very low in surface soil. Multiple linear regression analysis appeared a strong relationship between the MWDp1/MWDp2 and slope gradient (R2= 0.51, p< 0.001). This study revealed that the MWDp1/MWDp2 is the proper index to evaluate soil surface erosion in the semi-arid hillslopes. Manuscript profile

Open Access Article

3 - Detection The Spatiotemporal Association between Climatic Factors and Vegetation Cover (NDVI) (Case study: Charmahalva Bakhtiary Province of Iran)
Behzad Amraii mansor halimi

10.22034/jest.2021.45792.4751

Background and Objective: the climate factors are main determinant of vegetation spatiotemporal dynamics. A visual comparison of climate and vegetation on a global scale immediately reveals a strong association between climate and vegetation.  The main object of th More

Background and Objective: the climate factors are main determinant of vegetation spatiotemporal dynamics. A visual comparison of climate and vegetation on a global scale immediately reveals a strong association between climate and vegetation.  The main object of this study is to reveal the spatiotemporal association between climatic factors and Modis derived NDVI in Charmahal & Bakhtiary province of Iran.Material and Methodology: In this study, we use MOD13A3 of MODIS product as NDVI layer for study area. MOD11A2 as land surface temperature and mean monthly accumulative rainfall of synoptic station for study area during 2008 to 2018. We used the correlation analysis in 0.95 confident level (P_value =0.5) to reveal the spatiotemporal association between the NDVI and climatic factors.Findings: The results indicated that during winter (December to March) the spatial distribution of NDVI is highly correlated with LST spatial distribution. In these months, the pixels which have the high value of NDVI are spatially associated with the pixels which have highest value of LST (6 to 12C°). In winter the spatial correlation between NDVI and LST is so high which is statistical significant in 0.95 confident level. In transient months such as May, October and November, the spatial correlation between NDVI and LST is falling to 0.30 to 0.35, which is not statistical, significant in 0.95 confident level. Finally, in summer season or warm months including Jun to September, we found the minimum spatial association between the NDVI and LST.Disscosion & Conclusion: we found that the maximum correlation between NDVI and LST simultaneously appears and no lag time has been observed. The spatial correlation of NDVI and monthly accumulative rainfall was statistical significant in spring season (April to Jun) by 1-month lag time but in other months we do not find any significant correlation between NDVI and rainfall.  Manuscript profile

Open Access Article

4 - Investigation on the Qualitative Changes of Tehran green space, between 1990 and 2006(Case study: District 5 of Tehran municipality)
Mona Soroudi Seid Ali Jozi

Background and Objective: Regarding the vegetation's crucial role in urban environment, investigation on the change detection seems to be necessary. Therefore, the usage of remote sensing was noticed to be important to study the changes. Method: In this study, to estim More

Background and Objective: Regarding the vegetation's crucial role in urban environment, investigation on the change detection seems to be necessary. Therefore, the usage of remote sensing was noticed to be important to study the changes. Method: In this study, to estimate the qualitative changes of vegetation cover, the NDVI was applied and Tm and IRS images of 1990 and 2006 were used and vegetation maps of District 5 of Tehran municipality by underlining the different greenness levels were generated. Findings: Statistics revealed that the area of good and moderate greenness level vegetated lands decreased and the area of poor greenness level vegetated lands increased by 23.22, 684.27 and 299.43 ha respectively. It is important to mention that to find out the procedure of qualitative changes of the study area's vegetation cover post-classification change detection technique applied and results indicated that non-vegetated areas converted to poor and moderate greenness level vegetated lands by 0.9 and 186.48 ha respectively. Also the conversion of 419.58 ha of poor and 175.86 ha of moderate greenness level vegetated lands to non-vegetated lands was noticed.                                                                                                                Conclusion: The maximum amount of increased non-vegetated area and destroyed moderate and good greenness level vegetated lands were studied in region number 2. So, region number 2, in comparison with other six regions has been changed the most during 1990 to 2006. The equal amount of increased non-vegetated area and decreased vegetated area by 408.06 ha showed that land use changes have been accrued in study area, therefore conservation and increase the urban vegetated areas are important to develop urban master plans.                                                                                                                         Manuscript profile

Open Access Article

5 - Studying the effect of dust on vegetation changes (Case study: Shadegan wetland, Khuzestan)
Reza Bayat Somayeh Jafari Bagher Ghermezcheshmeh Amir Hossain Charkhabi

Wetlands and water ecosystems are important, especially in terms of environmental values. Mapping vegetation changes can provide valuable information and removing vegetation can cause environmental disasters such as dust. This study aimed to investigate and determine th More

Wetlands and water ecosystems are important, especially in terms of environmental values. Mapping vegetation changes can provide valuable information and removing vegetation can cause environmental disasters such as dust. This study aimed to investigate and determine the spatial and temporal variations in Khuzestan, Shadegan wetland coverage and these changes are analyzed with a dust storm data. Temporal and spatial variation of vegetation measured using Normalized difference vegetation index (NDVI) of MODIS images from 2000 to 2011, and vegetation cover changes were determined and different variables of dust (total annual density, maximum annual concentrations and annual average concentrations of dust)  from Ahwaz station were analyzed for detecting changes of vegetation cover. The results indicated that the total area of vegetation NDVI from 2000 to 2011 declined 7.36%. Also, the results showed the highest and lowest water area 25.67% and 19.72% belong to 2007 and 2000 respectively, and the highest and lowest vegetation area were 31.21% and 17.27 % in 2000 and 2004 respectively. According to statistics from 2002 onwards we have been faced with increasing dust storm which indicated a correlation between dust and wetland vegetation. Also worth noting is that the total annual concentration of dust and vegetation indices showed a higher determination coefficient (0.8516). Meanwhile, 2 month delay effect of dust has 0.8214 determination coefficient with NDVI. Manuscript profile

Open Access Article

6 - Study effect of flood productivity on vegetation changes using field work and Landsat satellite images (Case study: Shandak of Sistan region)
Mansour Jahantigh Moien Jahantigh

The object of this research is evaluated of flood productivity on vegetation cover changes. For this purpose, 5 linear transects with a length of 50 m were installed before flooding in the year 2006. In each of these transects, two plots 3×3 were identified at a h More

The object of this research is evaluated of flood productivity on vegetation cover changes. For this purpose, 5 linear transects with a length of 50 m were installed before flooding in the year 2006. In each of these transects, two plots 3×3 were identified at a height of 50 m at the beginning and 1% in length, and within each of them a plot of 1×1 was laid out for uniform harvesting at equal distances, their coordinates using specific GPS and feature the percentages of canopy cover, forage production, bare soil percentage, density and litter before starting flood spreading in 2003 were estimated. In addition, the vegetation characteristic changes were measured in the same place after the flood propagation in the year 2019. Landsat satellite images for a period of 16 years (2003-2019) was also used to study vegetation changes before and after flood propagation. For this purpose, after applying pre-processing on the images, the vegetation index was adjusted according to the soil adjusted vegetation index (SAVI) and soil water index (SWI) over five different time periods. Field results showed that with the application of flood propagation application, the amount of forage production increased from 68 to kg/ha, the percentage of canopy cover increased from 5.9 to 31.4%, as well as the amount of litter from 2 to 16.8% and bare soil decreased from 92.1 to 51.8%. Statistical analysis of vegetation characteristics before and after flood propagation revealed a significant difference between these parameters (p<0.01). In addition, the results showed significant changes in the SAVI and SWI indices over the period. The SAVI and SWI indices increased from 0.027 and 0.5 in the year 2003 to 0.49 and 1 in the year 2019, respectively, and the trend of changes in these indices showed high correlation (R² = 0.65) in flood propagation area. The results of this study showed that flooding productivity by providing soil moisture in the study area improved germination and plant growth conditions, which resulted in the establishment and improvement of vegetation cover in the floodplain. Manuscript profile

Open Access Article

7 - Vegetation Vulnerability Probability Index: A Method for Determining Desertification Risk
Esmail Heydari Alamdarloo Pouyan Dehghan Rahimabadi Hassan Khosravi Javad Rafie Sharifabad Hassan Barabadi

10.30495/girs.2022.692984

Determining desertification risk can be a good way to prioritize an area for management and control of the desertification process. One determinant of desertification risk is the use of the Probability of Vegetation Vulnerability Index (PVVI). For this purpose, in this More

Determining desertification risk can be a good way to prioritize an area for management and control of the desertification process. One determinant of desertification risk is the use of the Probability of Vegetation Vulnerability Index (PVVI). For this purpose, in this study, LST and EVI of MOD11A2 and MOD13A2 products, respectively, from MODIS sensors were used to calculate TCI and VCI to estimate VHI in Yazd province from 2001 to 2019. VHI, which indicates the severity of drought, was classified into five classes. Then, the probability of occurrence for each class was calculated and multiplied by the weight of each class, which was between zero and 4 based on the severity of the drought. Finally, by adding the values obtained for each class, PVVI was calculated. The results showed that in the western, eastern, and southern parts of Yazd province, the risk of vegetation degradation and consequent desertification is generally higher than in other areas. The highest probability of Non-drought class occurs in Abarkooh (VHI = 68.34) and the lowest is in Ardakan (VHI = 53.59). Abarkooh with 14.03% and Ardakan with 46.02% have the lowest and the highest areas in the high class of PVVI. Also desert areas and uncovered lands, such as Abarkuh, were at low risk of desertification, which could be due to the ecological inability of this area to regenerate the vegetation cover. In general, the evaluation of the results obtained in this study showed that PVVI can distinguish real deserts from the areas that are at risk of desertification. Manuscript profile

Open Access Article

8 - Development trend analysis of urban heat island regarding land use/cover changes using time series of landSat images
Sirous Hashemi Dareh Badami Isar Nouraeisefat Saeid Karimi Sajad Nazari

Using time series of satellite images is a cheap and efficient way to study trend changes of natural and human phenomena. The aim of the studyis to analyze the development of Urban Heat Iisland (UHI) in Rasht using time series satellite images. For this study, time seri More

Using time series of satellite images is a cheap and efficient way to study trend changes of natural and human phenomena. The aim of the studyis to analyze the development of Urban Heat Iisland (UHI) in Rasht using time series satellite images. For this study, time series of LandSat images during 1990 and 2015 were used. Thresholding Normalized Difference Vegetation Index (NDVI) and Fraction Vegetation Cover (FVC) method has been applied to obtain the land surface emissivity; in addition, Planck's law for TM and ETM+ images and Split Window (SW) algorithm for OLI/TIRS images were utilized in order to retrieve land surface temperature. UHI and FVC trends were analyzed by statistical and Mann-Kendall methods. Statistical analysis showed that the average of FVC has decreased during the study periodand data skewness has changed to low FVC. The reduction trendhas increased FVC caused an average normalized temperature during the study period and also enhanced the data skewness of land surface temperature. The Mann-Kendall spatial analysis showed that in most of the study area, the land surface temperature and vegetation fraction haveincreased and decreasing trends, respectively; these mentioned trends have been intensified in the places where gardens and agricultural land uses were changed into built-up ones. Manuscript profile

Open Access Article

9 - Analysis relation of vegetation cover on the number of dust event in Khorasan Razavi using geographic information system and remote sensing
Sima Pourhashemi Mehdi Boroghani Mohammad Ali Zangane Asadi Abolghasem Amir Ahmadi

Dust phenomenon is one of the climatic hazards in arid and semi-arid regions of the world that usually brings damages to human life and properties. In recent decades due to long droughts in Iran, the number of dust event increased and affected many cities and villages. More

Dust phenomenon is one of the climatic hazards in arid and semi-arid regions of the world that usually brings damages to human life and properties. In recent decades due to long droughts in Iran, the number of dust event increased and affected many cities and villages. The aim of this study was to investigate the effect of vegetation and relationship with dust events in Khorasan Razavi province during 2004-2013 using Geographic information system (GIS) and Normalized difference vegetation index (NDVI). The data of dusty days in the region synoptic stations were provided from Meteorological Organization and the frequency of dusty days in different seasons were determined.  Using the method of Normal Kriging in GIS, dusty days were zoned in the province. Vegetation map area, were provided using MODIS image in ENVI®4.8 software. The results showed closed relations between the number of dust event and vegetation distribution. In addition, decreasing of vegetations caused the increasing of  the number of dust event. Results showed the number of dust event increased during the recent years and in 2008 and 2005 were recorded as the most and the least number of dust event respectively. Manuscript profile

Open Access Article

10 - پیش بینی تأثیر پوشش گیاهی بر ضریب زبری هیدرولیکی کرانه و بستر رودخانه خشک شیراز
محمدرضا نیک منش

مدیریت منابع آب و خاک در رودخانه‌ها، بدلیل ارتباط مستقیم با سیستم‌های مختلف همچون زمین ، جامعه و مردم از اهمیت بالایی برخوردار است. طرحهای احیای پوشش گیاهی و بیومهندسی در رودخانه‌ها، همواره به عنوان یکی از روشهای مدیریتی منابع آب و خاک مد نظر بوده، اما اینگونه طرح‌ها، ع More

مدیریت منابع آب و خاک در رودخانه‌ها، بدلیل ارتباط مستقیم با سیستم‌های مختلف همچون زمین ، جامعه و مردم از اهمیت بالایی برخوردار است. طرحهای احیای پوشش گیاهی و بیومهندسی در رودخانه‌ها، همواره به عنوان یکی از روشهای مدیریتی منابع آب و خاک مد نظر بوده، اما اینگونه طرح‌ها، علیرغم مزایای فراوانی که دارد، در صورت طراحی و روش‌های اجرایی نامناسب، می تواند مشخصات هیدرولیکی رودخانه را تغییر دهد. استفاده از پوشش گیاهی، کاهش میانگین سرعت جریان، کاهش عرض رودخانه، افزایش رسوب گذاری در بستر رودخانه و در نتیجه کاهش دبی جریان عبوری رودخانه را به همراه دارد و در مواردی ممکن است، باعث بالا آمدن سطح آب و افزایش عمق جریان گردد. در این مقاله ضمن معرفی جنبه‌های مختلف مدیریتی منابع آب و خاک در رودخانه‌ها و به طور خاص، رودخانه خشک، به عنوان یک عنصر تأثیرگذار مهم در شهر شیراز، طرحهای احیای پوشش گیاهی و بیومهندسی اجرا شده در این رودخانه و تأثیرات آنها بر هیدرولیک رودخانه، مورد بررسی قرار گرفته است. همچنین فواید این طرحها، در بازه‌هایی از رودخانه خشک که با روش‌های مناسب اجرا شده و باعث حفظ منابع آب و خاک گردیده اند و همچنین مضرات آنها، در بازه‌هایی که  با روشی نامناسب انجام شده و باعث افزایش ضریب زبری و کاهش دبی جریان عبوری می گردند، مورد تجزیه و تحلیل قرار می گیرد. بر اساس نتایج به دست آمده، اگرچه میزان فرسایش کناره‌های رودخانه  در مقاطع فاقد پوشش گیاهی به مراتب بیشتر از مقاطع دارای پوشش گیاهی، می‌باشد، اما به دلیل افزایش ضریب زبری و کاهش سطح مقطع، ناشی از وجود پوشش گیاهی، در برخی مقاطع، دبی عبوری به مقدار قابل توجهی کاهش می یابد. مقاطعی نظیر بالادست و پائین دست پل بلوار چمران،  بالادست پل غدیر و  پائین دست پل فضیلت، نمونه‌هایی از این مقاطع می باشند که نتایج آنالیز انجام شده با نرم افزار HEC-RAS در این مقاطع، برای دبی عبوری 100 تا 250 مترمکعب بر ثانیه، کاهش دبی عبوری به مقدار 10 تا 5/28 درصد را نتیجه می دهد. Manuscript profile

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