dc.description.abstract |
Vegetation phenology is a key environmental indicator of ecological response to climate
variability. Long-term studies of phenological changes by applying remote sensing
techniques can improve our understanding of spatiotemporal climate patterns. However,
studies have not been focused on such phenological dynamics in Tana and Beles sub basins. Therefore, this study explored the vegetation phenology dynamics in relation to
rainfall seasonality parameters and lag time effects of rainfall on vegetation phenology.
From MODIS 8-day normalized difference vegetation index and from Climate Hazards
Group Infrared Precipitation with Station dataset pentad rainfall data was calculated
over the 20-year period (2001-2020). TIMESAT program was used to generate and
derive major phenological events for cropland, grassland and shrub and bushland
vegetation types. Rainfall seasonality and phenological event relationships were
examined, and simple linear regression models were created. The study found cropland,
grassland, and shrub and bushland had mean start of growing season on 166th, 133rd and
146th days of the year, with average end of growing season dates 312th, 335th and 343rd
days of the year, respectively. Over the 20-year study period, rainfall and phenological
parameters exhibited a positive and significant strong relationship with correlation
coefficients of 0.76, 0.49 and 0.56 for the start of the growing season and the start of the
rainy season, and 0.31, 0.38 and 0.19 for the end of the growing season and the end of
the rainy season respectively. Cropland, grassland and shrub and bushlands had average
23,11, 6 days lag time between the start of the rainy season and the start of the season,
respectively. As a result, the findings of this study point to a much more explicit role of
rainfall on vegetation phenology, specifically as one of other climate agents that could
recommended as properly understand the pattern of phenological events which helps
farmers and decision makers about the determining crop sowing date and vegetation
management that able to adapt the changing environment. |
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