Extended Abstract
Introduction: Rangelands, as renewable natural resources, play a vital role in environmental preservation and in meeting the needs of both livestock and vegetation. These resources not only provide forage for livestock but also protect soil and water. However, unplanned land-use changes and degradation of vegetation cover in Iran, especially over the past four decades, have led to a decline in the quality of these resources. Factors such as population growth, urbanization, and overgrazing by livestock have contributed to rangeland degradation. In this context, remote sensing (RS) and geographic information systems (GIS) are efficient tools for monitoring these changes. These technologies enable precise monitoring of environmental changes and the identification of factors such as soil salinity and erosion without the need for costly traditional methods. The use of satellite data provides valuable insights for assessing vegetation cover changes, drought impacts, and other environmental threats. Therefore, these tools play a significant role in natural resource management and rangeland conservation.
Materials and Methods: This study focuses on the Jiransu winter rangeland in the Maneh and Samalqan district, covering an area of 2,168 hectares. Located in northwestern Iran, the region has a cold and dry climate with an annual rainfall of 223 mm. To analyze vegetation cover changes, Landsat time-series images (TM and OLI) and Google Earth images were used. Satellite images with a spatial resolution of 30 meters were collected from different years (1997, 2002, 2008, 2013, 2018, and 2023) from the US Geological Survey (USGS) archive. After data preprocessing to ensure quality and correct geometric and radiometric errors, the images were processed using various techniques such as histogram adjustment and color composite for information enhancement. NDVI and MSAVI vegetation indices were employed for vegetation analysis. Subsequently, vegetation cover changes were analyzed using image differencing and threshold classification methods.
Results and Discussion: The results revealed that during the analyzed time periods, the lowest vegetation index values were observed in 2008, coinciding with a severe drought in Iran. This reduction in vegetation cover highlights its strong dependence on rainfall and climatic conditions. Land-use changes showed similar trends, particularly during the 1997–2008 period, where approximately 226 hectares of poor rangeland were lost, representing 10% of the total rangeland area. In the subsequent period (2008–2013), approximately 323 hectares of poor rangeland decreased, with declining classes covering more than 14% of the area. These findings indicate that RS methods, particularly those using vegetation indices, are efficient and accurate tools for monitoring vegetation changes and assessing rangeland conditions. Overall, the study emphasizes that satellite images and vegetation indices like NDVI and MSAVI offer significant accuracy in detecting ecological changes and trends, especially in dry and semi-arid regions, compared to traditional methods.
Conclusion: This study emphasizes the importance of NDVI and MSAVI indices in monitoring vegetation cover changes and demonstrates that these indices can effectively track degradation trends and environmental changes. These indices, particularly in dry and semi-arid regions impacted by climate change and drought, play a key role in modeling vegetation decline and rangeland productivity. Furthermore, the results suggest that using these indices, due to their ability to correct for bare soil effects and their effectiveness in assessing vegetation changes, provides valuable tools for rangeland monitoring and management. These tools can aid in identifying degraded areas and, by providing timely and accurate data, help predict and manage rangeland degradation. Therefore, integrating these indices into comprehensive natural resource management programs and utilizing them in detailed environmental assessments can play a crucial role in enhancing conservation efforts for natural resources. Additionally, their application can have a profound impact on the restoration and improvement of ecosystem health, leading to long-term environmental sustainability.