Behnaz Asefjah; Yahya Esmaeilpour; Ommolbanin bazrafshan; Hossein Zamani
Abstract
The past decade has seen a major revolution in vegetation monitoring using satellite imagery, resulting in quantitative indicators of vegetation with a professional processor in a web-based interactive development environment. In this study, using MOD13A1 and MOD13Q1 products of Modis sensor, the trend ...
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The past decade has seen a major revolution in vegetation monitoring using satellite imagery, resulting in quantitative indicators of vegetation with a professional processor in a web-based interactive development environment. In this study, using MOD13A1 and MOD13Q1 products of Modis sensor, the trend of temporal and spatial changes of NDVI and EVI indices in Fars province in a period of 16 days from 2000 to 2020 was coded and processed monthly in Google Earth engine system. The results of this study showed that the average index of NDVI index is from minimum 0.11 to maximum 0.495 and the average index of EVI index is 0.1. According to the results obtained in this survey, in all the years from 2000 to 2020 in January, NDVI and EVI values had the highest values compared to other months, so that in January 2019 and January 2020, the highest EVI values averaged 0.22 and the NDVI values Was estimated to be 0.18. The lowest monthly average values of both indices occurred between 2000 and 2005, which indicates that the vegetation has been severely degraded during these years. The results of spatial changes using EVI index showed that the level of vegetation in Fars province in different months varied from 10,000 square kilometers to 22,000 square kilometers and from the perspective of NDVI index from 15,000 square kilometers to 30,000 square kilometers.
Reza Omidipour; Ataollah Ebrahimi; Pejman Tahmasebi; Marzban Faramarzi
Abstract
Vegetation canopy cover (VCC) and Above-Ground Phytomass (AGP) are the most important indicators of rangeland ecosystem’s structure and function, therefore their accurate evaluation and monitoring is vital for ecosystem welfare. Vegetation indices, are essential tools for assessing and monitoring ...
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Vegetation canopy cover (VCC) and Above-Ground Phytomass (AGP) are the most important indicators of rangeland ecosystem’s structure and function, therefore their accurate evaluation and monitoring is vital for ecosystem welfare. Vegetation indices, are essential tools for assessing and monitoring VCC and AGP which have not been addressed under different managerial conditions, so far. In the present study, the effect of long-term grazing and enclosure (26-year) on the relationship between the VCC and AGP with vegetation indices were evaluated in the Sabzkouh protected area of ChaharmahalVaBkhtiari province using Landsat-8 images. VCC and AGP were evaluated in both grazed and enclosed area by 10 plots of 30*30-m in each of which three quadrates of 2×2 square meters were applied (totally 60 quadrates) in the June, 2016. The results indicate significant differences between grazed and enclosed areas in terms of VCC (57% and 46 respectively) and AGP (with 1656 and 1011 kg per hectare, respectively). The soil adjusted vegetation indices show a more significant prediction of VCC in enclosed and grazed areas (TSAVI1=0.828 and PVI3=0.884, respectively). The PVI2 index showed appropriate results for estimating AGP in both enclosed (R2=0.726) and grazed (R2=0.698) areas. The improved performance of these indies is mainly due to the adjustment of soil effects. Our results suggest that grazing caused a significant effect on the relationship between VCC and AGP with vegetation indices due to feasible changes in vegetation structure or composition. Therefore, using different indices is necessary to study and monitor different rangelands under management strategies.
TAYYEBEH MESBAHZADEH; farshad soleimani sardou
Abstract
Due to incorrect policies in the water resources sector and excessive withdrawal of groundwater resources, water quality in most plains of the country has decreased. Therefore, the quality of water for drinking and agriculture is important in qualitative terms.With this aim in this study, the desertification ...
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Due to incorrect policies in the water resources sector and excessive withdrawal of groundwater resources, water quality in most plains of the country has decreased. Therefore, the quality of water for drinking and agriculture is important in qualitative terms.With this aim in this study, the desertification changes in Khash plain were studied using two criteria of groundwater and vegetation. Shooler and Wilcox diagrams were drawn up for AquaChem software for the years of 2001, 2008 and 2015. Also, spatial variations were made on Arctic plain surface using Arc GIS software and vegetation changes trend were also done using MOD13A2 sensor images and remote sensing techniques. The results showed that the number of wells that have an unpredictable TDS in the years 2008 and 2015 compared to 2001 have been increased by comparing the Schuler diagram. However, the level of lands with good drinking status decreased during the years 1387 and 1394 compared to 1380 and was increased by the level of acceptable drinking water. According to Wilcox's diagram, the result is that most wells are salty to very salty and their use is harmful to agriculture or requires measures. The results of the vegetation change trend also indicated that the trend is to reduce vegetation and the average level of the NDVI index decreases with the passage of time.
sahar sabaghzade; Mohammad Zare; Mohamad Hosein Mokhtari
Abstract
Vegetation is an important component of each global ecosystem. Determining of the biomass of plant is important to assess its impact upon climate, soil erosion, and as well for management of natural resources. The aim of this study was to estimate biomass using vegetation indices based on remote sensing. ...
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Vegetation is an important component of each global ecosystem. Determining of the biomass of plant is important to assess its impact upon climate, soil erosion, and as well for management of natural resources. The aim of this study was to estimate biomass using vegetation indices based on remote sensing. The Landsat 8 data of May 2013 and field studies coinciding with field imaging in Marac (South Khorasan province) were used. Tamarix plant biomass measured in 30 random plots of 11 vegetation indices including DVI, IPVI, NDVI, PVI, RVI, SAVI, TSAVI, WDVI, and Tasselcap were used to estimate biomass of Tamarix.Then, using cluster analysis, vegetation indices were divided into three groups among which SAVI, RVI , and IPVI were chosen. The results showed that indexes which consider soil factors are more accurate than other measures. In this study, biomass map was prepared using the SAVI index.
