جستجوی مقالات مرتبط با کلیدواژه « Decline » در نشریات گروه « جغرافیا »

Sistan is a large and extensive land that throughout history in the field of livelihood, economic and agricultural activities such as "Khorasan bread warehouse and breadbasket" has had ups and downs. The economic and agricultural decline of Sistan in the history of post-Islamic Iran will be addressed using library tools and historical-analytical research methods. Considering the issues raised, the main question of the present study is: What are the causes of the stagnation of agricultural production and economic decline in Sistan in different Islamic periods caused by what phenomena and natural disasters? Comparative studies of the research based on local and geographical historical texts such as: "History of Sistan and the revival of the kings and the genealogy of the kings" show natural phenomena such as: severe erosion in Sistan, the presence of branches, the phenomenon of quicksand, 120-day winds in Sistan, successive droughts, famine outbreaks, cholera and plague are caused by human activities, and subsequently the destruction of farms has been directly and indirectly related to the economic and agricultural recession in Sistan. Other factors affecting growth and The spread of natural disasters by the Mongols and Timurids in this region had a significant impact on the decline in production and economic activities, and the adverse consequences of this siege, many dams, damaged water structures and the ground to reduce the loss of economic and agricultural activities.

Decline phenomenon is one of the most important reasons for the destruction and mortality of oak trees in Zagros forests due to the wide variety and diversity of the topography of its determination through track and field operations is not readily possible. Changes in an ecosystem are often gradual changes, but sometimes changes occur in an ecosystem in a short time. This change can cause a catastrophe in the ecosystem, which is difficult to identify. A proposed method for identifying a general change in time series is use the BFAST model, which, by analyzing the time series in the process, season, and residual components, identifies the changes in the time series and also repeatedly estimates the time and amount of the changes, and The path and amount of variation in this study, using this model and satellite images to monitor and evaluate the changes in coverage and decline of oak forests in Lorestan province during the statistical period (2000-2017). The results showed that more than 42804 hectares (1.5%) of the oak forests of the province were lost due to the decline phenomenon during the studied period. Also, according to the BFAST method, the trend diagram is a failover and their frequency variations are irregular. Comparison and study of different forest coverings also showed a decrease in NDVI, which indicates that the process of decreasing forest cover is inclusive. The study of autocorrelation and Kendal coefficient showed that there were significant changes and severity of failure (-0.7) in the area Study. The seasonal chart also has uneven and irregular variations due to changes in oak forests in the region. The results of this research can be used to study the changes in the coverage of oak forests in the area and management and the way to think about this phenomenon.