Document Type : Original Article

Authors

• احمد عباس نژاد ¹
• Ali Asghar Darvishsefat ²

¹ College of Agriculture & Natural Resources of University of Tehran

² Faculty of Natural Resources, University of Tehran, Karaj, I.R. Iran

Abstract

Investigating the long-term trend of changes in this ecosystem and their response to climate change is necessary for sustainable managemen. Therefore, the aim of the current research is to investigate the long-term trend of Hyrkanian forests in time and space and their relationship with changes in climatic parameters. For this purpose, the MOD13Q1 and MYD13Q1 products of the MODIS sensor were combined and a time series with an interval of 8 days and a spatial separation of 250 meters was prepared from the EVI vegetation cover index for the period from 2003 to 2020. Also, data from synoptic stations prepared and a time series of T_min, T_max and P every 8 days, it was built in the mentioned time period. Then the Mann-Kendall test and its significance were used to investigate the long-term change trend of forests and the Pearson coefficient was used to investigate the correlation of climatic parameters with the average EVI in the forest areas that are 5 and 10 km away from the meteorological station. The results of the long-term trend showed that the phenomena of greening and browning occurred in 77 and 23 percent of the region, respectively, of which 47.97 and 7.79 percent are significant at the 10% level. Also, the Pearson correlation between EVI and climatic parameters showed that EVI has a positive and strong correlation with temperature and a weak correlation with precipitation.the present study confirms Greening for forests over an 18-year time span, and identifies temperature as its main climatic factor.

Keywords

• long-term trend
• temperature
• precipitation
• EVI
• Browning and Greening

Main Subjects

• Climatology