Study the effect of meteorological variables variation on phenology of temperate forest in Gorgan region using MODIS sensor

Articles in Press

Document Type : Research Paper

Authors

1 Dept of Irrigation and Reclamation Engineering, Faculty of Agriculture, University of Tehran Karaj, Iran

2 Dept of Irrigation and Reclamation Eng, Faculty of Agriculture,University of Tehran, Karaj,Iran

Abstract

In this research, the temporal changes of three phenological events of the start (SOS), End (EOS) and Length (LOS) of the growing season of the temperate forest located in the south of Gorgan city, north of Iran, in response to meteorological variables variations was investigated. temperature and rainfall data of and the time series of the Vegetation Index (EVI) of the MODIS sensor, were collected and analyzed using three smoothing approaches. Results showed that in all three smoothing methods, an increase in T ̅_max and T ̅_min in the 10-day period prior to SOS phenology stage, it would be delayed, similarity any decrease in T ̅_max and T ̅_min in a 10-day period before the EOS, this stage is also delayed. In Gaussian and Savitzky-Golay (p < 0.05) and Double Logistic (p < 0.01) methods, correlation between LOS and T ̅_min and T ̅_max in spring; and in all three smoothing methods, the correlation of SOS and EOS with T ̅_max in the summer season was significantly positive, and the correlation of SOS and EOS with T ̅_min in the summer season was weak and positive (p < 0.05). Also, SOS, EOS and LOS phenological stages have not shown any significant relationship with precipitation in different seasons. According results, temperature is the most important factor in the variability of SOS, EOS, and LOS occurrence time in study forest. Any increase and decrease of T ̅_max and T ̅_min cause daily shifts in the time of occurrence of these phenology stages.

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Iranian Journal of Soil and Water Research

Articles in Press, Accepted Manuscript
Available Online from 22 February 2025

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