Leila Yaghamei; Reza Jafari; Saeed Soltani; Hasan Jahanbazi
Abstract
Snow is one of the effective fators on vegetation rate and function in mountainous areas. The aim of this study was to investigate the impact of snow cover area index and snow cover duration index on two declining and dominant plant species including Astragalus adscendens and Quercus brantii in Chaharmal ...
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Snow is one of the effective fators on vegetation rate and function in mountainous areas. The aim of this study was to investigate the impact of snow cover area index and snow cover duration index on two declining and dominant plant species including Astragalus adscendens and Quercus brantii in Chaharmal and Bakhtiari Province from 2003 to 2016. For this purpose, Normalized Difference Snow Index (NDSI) and Normalized Difference Vegetation Index (NDVI) were extracted from MODIS satellite images and compared using Pearson analysis in forest decline regions (Barz, Seveh, Helen and control area) and in rangeland decline regions including Astragalus adscendens decline and control areas. Results showed that about 32% of the snow cover in the study area has been reduced, although a constant trend was not observed. The studied snow indices showed the highest relationships with rangeland and forest vegetation cover in March. The decline region of Astragalus adscendens had the maximum relationship with the snow cover area (R>0.70) and snow cover duration (R>0.71) in March. According to the findings, snow precipitation in late winter season and its duration is more effective on the rangeland Astragalus adscendens species than forest vegetation cover and this pecies can be more sensitive to decline in case of snow reduction.
Nahid Moshtagh; Reza Jafari; Saied Soltani; Nafiseh Ramezani
Abstract
Land surface temperature (LST) is an essential parameter in ecological, hydrologic, climatic, and related studies. The objective of this study was to evaluate the performance of Artis and Sobrino algorithms for retrieving LST from 2009 Landsat TM thermal infrared band in Damaneh region of Isfahan province. ...
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Land surface temperature (LST) is an essential parameter in ecological, hydrologic, climatic, and related studies. The objective of this study was to evaluate the performance of Artis and Sobrino algorithms for retrieving LST from 2009 Landsat TM thermal infrared band in Damaneh region of Isfahan province. The accuracy of LST extracted from geometrically corrected image was then assessed against field-based LST data recorded at 10 meteorological stations using linear regression analysis. The results showed that both algorithms were able to map LST spatial distribution in the region and they were significantly correlated (R>0.97), but the Artis algorithm performed slightly better than Sobrino one. This algorithm explained up to 72% of the variation in the field measurements of LST. According to this algorithm, bare lands and highly vegetated agricultural and rangeland areas had the highest (328k0) and lowest LST (291k0) in the region, respectively. As the results indicated here the decrease in vegetation cover corresponds with increase in temperature values, therefore, remotely-sensed LST information with their extensive coverage can have a key role in ecosystem management.
Fatemeh Hadian; Reza Jafari; Hossein Bashari; Saeed Soltani
Abstract
Because soil moisture condition affects vegetation changes hence, monitoring of drought and vegetation changes are among valuable management tools in these ecosystems. Nowadays, satellite images are used as a low-cost and fast method for vegetation study in different scales. Vegetation change is assessed ...
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Because soil moisture condition affects vegetation changes hence, monitoring of drought and vegetation changes are among valuable management tools in these ecosystems. Nowadays, satellite images are used as a low-cost and fast method for vegetation study in different scales. Vegetation change is assessed using vegetation spectral characteristics. This study aimed to analyze and monitor the vegetation cover changes in 4 rangelands and one forest type site in south of Isfahan and southeastern of Chaharmahal and Bakhtiary province during 1997-2009 ّField sampling were used for measuring the percentage of canopy cover in all vegetation types using step-point method in radial direction (6000 points per vegetation type). Regression analysis technique was used to ensure if vegetation cover can be measured properly using a Landsat images from 2009. Then NDVI indices were derived from 12 Landsat images between 1997 to 2009 (all images were taken from 22th of May to 5th of Jun each year) to monitor vegetation changes. According to results, there was significant correlation between NDVI indices and canopy cover in all vegetation types. Evaluating the canopy cover changes indicated that the precipitation had various effects on different vegetation types based on their plant form and ecological condition. T
