Volume 18, Issue 2 (7-2024)
مرتع 2024, 18(2): 184-201 |
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Dehghan Rahimabadi P, Heydari Alamdarloo E, Rahimi Dehcheraghi M, Azarnivand H. Investigating the Trend of NPP Changes in Vegetation Cover of Alborz Province. مرتع 2024; 18 (2) :184-201
URL: http://rangelandsrm.ir/article-1-1125-en.html
URL: http://rangelandsrm.ir/article-1-1125-en.html
Pouyan Dehghan Rahimabadi 
, Esmail Heydari Alamdarloo , Masoumeh Rahimi Dehcheraghi , Hossein Azarnivand
, Esmail Heydari Alamdarloo , Masoumeh Rahimi Dehcheraghi , Hossein Azarnivand
Department of Reclamation of Arid and Mountainous Regions, Faculty of Natural Resources, University College of Agriculture and Natural Resources, University of Tehran, Karaj, Iran.
Abstract: (1523 Views)
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.
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.
Type of Study: Research |
Subject:
Special
Received: 2022/02/16 | Accepted: 2022/07/4 | Published: 2024/07/31
Received: 2022/02/16 | Accepted: 2022/07/4 | Published: 2024/07/31
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