تأثير شرايط اقليمي بر خشكيدگي درختان بلوط ايراني در زاگرس

Forests are considered to be one of the main links of life continuity due to their effective role in the oxygen, water an‎d carbon cycles. Zagros oak forests are the dominant species of Zagros forests. In this study, the forest region of the northeast of Khuzestan province in the counties of Dezpart, Izeh an‎d Baghmalek was investigated during the period (2020-1990). To assess the impact of climate change on the forest cover of the region, MODIS sensor images from the 2000-2020 period, precipitation data, annual average lan‎d surface temperature from meteorological stations, an‎d VCI, NDVI, LST,ET-PET, AOD, DSI, SPI, VHI, an‎d TCI indices were used. The trends used were examined using Pettitt-Test statistical indicators. The P-test results confirmed an increase in air an‎d lan‎d surface temperatures of 1.3 ◦C, a decrease in water levels, an‎d thin an‎d dense vegetation cover without a trend, the TCI index of increasing temperature an‎d decreasing humidity in 2018, 2007, an‎d 2000, an‎d the VCI index of decreasing humidity in 2008, 2018, an‎d 2000. The VHI index, which includes vegetation health, confirms the existence of droughts in 2000 an‎d 2008 an‎d is consistent with precipitation fluctuations an‎d long-term droughts in the region. The DSI index has maximum values indicating the presence of drought an‎d inappropriate vegetation cover, an‎d the years 2000 an‎d 2008 show the most severe drought an‎d are consistent with the VHI index of the region. The AOD index, which is the result of changes in the concentration of aerosols in the atmosphere, is without a trend in the non-parametric test (P-Test) for the values of 0.47 an‎d 0.55, an‎d the year 2008 represents the turning point of the presence of aerosols in the region. The results of the non-parametric test of turning points (Pettittʹs Test) show that the average temperature has a significant trend at the 95% confidence level (P-value=0.04). an‎d the annual precipitation (1990-2020) of the region shows that since 2007, the frequency of precipitation with a negative anomaly has been higher. From this anomaly, it can be concluded that in the last decade the region has experienced drier years than in the early 1990s. The annual rainfall anomaly in the region confirms the occurrence of a long-term drought period from 2007 to 2017. Changes in the regionʹs vegetation an‎d humidity indicate increased humidity fluctuations during this time period. These two indicators indicate a decrease in forest cover in the region from 2000 to 2020. The consequences of continuing the current climate trend will be a decrease in carbon sequestration, a decrease in base flow, an‎d a change in the riverʹs water regime. Climate projections for the period 2021 to 2045 under scenarios 2.6, 4.5, an‎d 8.5 were made from CMPI6 data. Also, for the Baghmalek watershed, the calibration an‎d validation stage of the coefficient of determination, the Nash-Sutcliffe efficiency is 0.61. The climate results showed that in general, the temperature in the future period of 2045 has increased in all months compared to the previous period of 2012 to 2021, an‎d this increase has been different in different months. So that the increase in the average temperature of the future period compared to the previous period has been greater in the warm months of the year than in other months. The graph of changes in the average monthly precipitation in the future period for all three scenarios has almost the same conditions. So that the months of Azar, Di an‎d Bahman (December, January an‎d February) have been increasing an‎d in the rest of the months of the year there has been a decrease.

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