Showing 3 results for Heydari Alamdarloo
Bezad Rayegani, Hossein Arzani, Esmaeil Heydari Alamdarloo, Mohammad Mehdi Moghadami,
Volume 13, Issue 3 (10-2019)
Abstract
The present study examined impacts of climate change on the phenology and productivity data using remote sensing in Tehran province. Long-term changes in growing season in Tehran province from 2000 to 2014 were obtained from NDVI MODIS data. To generate and extract the phenological parameters TIMESAT software was used, and the time series was analyzed by TERRSET software (Earth Trend Modeler). Also, the correlation between the phenological curves, temperature and precipitation was investigated. The results of this assessment showed that in the northern part of Tehran, the beginning of the growing season of the plants occurred later than the other parts and the length of the growing season decreased. In the north of the province, especially in the northeastern part, there was a significant increase in the NDVI maximum value, and then this led to an increase in plant production parameters in this section. However, the southern part, especially in the southwest the beginning of the growing season of the plants occurred earlier and there is an increase in the length of the growing season. The results showed that in areas where non-climatic factors are cause of the vegetation change, no significant relationship between vegetation and climate parameters could be found by application of NDVI. As we approach the human setellments with more populations and tensions, the relationship between rainfall and vegetation decreases. This may be the impact of human activities.
Samaneh Bagheri, Esmail Heydari Alamdarloo, Hassan Khosravi, Azam Abolhasani,
Volume 15, Issue 4 (12-2021)
Abstract
Drought as a complex ecosystem crisis can affect vegetation density and health. Iran with an arid and semi-arid climate is exposed to this phenomenon. Therefore, it is necessary to evaluate the effect of drought on vegetation. The purpose of this study is to evaluate the effect of meteorological drought on vegetation dynamics in Iran. In this regard, using MATLAB software, SPEI index with time scales of 3, 6, 9, and 12 months years was calculated and zoned for 99 meteorological stations with a statistical length of 30 years in Arc GIS software. In the next step, the highest value of EVI index per month was obtained from MOD13Q1 MODIS sensor product for the period 2001-2019. Then, using Terrset software, the correlation and slope of EVI index changes were calculated based on SPEI index changes. The results showed that in 18.46, 22.63, 30.77, and 28.14% of the total area of Iran, the SPEI of 3, 6, 9, and 12 months have the highest correlation with vegetation, respectively. The results of linear regression analysis showed that in Lut plain and the heights of Alborz and Zagros mountain ranges, the sensitivity of vegetation to meteorological drought is much lower and the slope of the line has been negative. While the central, southwestern, southeastern, and coastal areas of the Persian Gulf have a positive line slope and vegetation has shown great sensitivity to meteorological drought. According to the obtained results, it can be concluded that climatic conditions, topography, type of vegetation, geographical location, and human management are effective in determining the relationship between the two indicators of vegetation and drought. As a result, it is suggested that in future studies on the effect of climate change on vegetation, factors such as topography, land use, etc. should be considered in the modeling.
Pouyan Dehghan Rahimabadi, Esmail Heydari Alamdarloo, Masoumeh Rahimi Dehcheraghi, Hossein Azarnivand,
Volume 18, Issue 2 (7-2024)
Abstract
Background and objectives: Primary Net Production (NPP) is a crucial component of the carbon cycle, key to carbon storage and evaluating ecosystem functions. Rainfall and temperature are essential elements in studying climatic stability in any region. Understanding temporal and spatial changes in NPP and its interaction with various climatic factors over the past decades has been central to global change studies. Advances in remote sensing data offer a cost-effective and accurate method to estimate NPP at landscape and regional scales
Methodology: This study examined the trend of spatiotemporal changes in NPP under the influence of climatic factors (temperature and precipitation) from 2006 to 2020 in Alborz province. NPP maps were extracted from the MOD17A3HGF product of MODIS, with annual and spatial resolutions of 500 meters. The Land Use/Land Cover (LULC) map for Alborz province was generated based on data from the Natural Resources and Watershed Management Organization of Iran, comprising nine categories: residential lands, water bodies, irrigated agricultural lands, rainfed agricultural lands, garden lands, good, medium, and poor rangelands, and lands without vegetation. The trend of NPP changes and its correlation with temperature and rainfall were investigated using the Mann-Kendall test and linear regression in TerrSet software's Earth Trends Modeler. Residential areas and water bodies were masked and excluded from correlation analysis. Finally, the average correlation coefficients of NPP with temperature and rainfall were classified.
Results: The results indicated that rainfall decreased in 2008 and 2014, reducing NPP in various LULC types. Conversely, precipitation increased from 2017 to 2020, leading to a rise in NPP in these LULC types. The temperature changes across different LULC types were not significant, resulting in a weak correlation between NPP and temperature. The highest NPP values were observed in irrigated agricultural lands, and the lowest in bare lands. NPP changes in most areas of Alborz province showed no trend; however, an increasing trend was noted in the northern and southern parts, while a decreasing trend was observed in the central parts. The correlation of NPP changes over time revealed a stronger positive correlation in the northern parts compared to the central and southern parts. The northern regions, especially the northwest, exhibited a higher intensity of NPP change than the central and southern regions. In contrast, the eastern and most southern areas showed less change.
Conclusion: Over the past 15 years, NPP in the central and southern parts of Alborz province has been more affected by annual rainfall than in the northern areas, due to the climatic and environmental conditions of the Alborz mountain range, which experience fewer climatic stresses than the southern regions. In contrast, NPP changes due to temperature showed the opposite results. The northern parts of the province were more affected by temperature changes than the southern parts. The high correlation between NPP and precipitation and the low correlation with temperature in the southern parts are related to the arid and semi-arid climate of these areas. Overall, NPP in Alborz province is generally influenced by climatic factors of rainfall and temperature. Conservation and restoration efforts should prioritize temperature and precipitation fluctuations as significant climatic factors.
