Evaluating the relationship between drought and vegetation greenness in Chyulu-Amboseli Rangeland, Kenya

Abstract

Remote sensing techniques have been widely used to monitor moisture-related vegetation conditions. Vegetation vigour response to drought however is complex and has not been adequately studied using satellite sensor data. This paper investigated the time lag response of vegetation to drought in Kenya’s Chyulu-Amboseli ecosystem based on Standardized Precipitation Index (SPI) derived from monthly precipitation data for the period January 2000-October 2016 downloaded from the Climate Hazards group InfraRed Precipitation with Stations and Normalized Difference Vegetation Index (NDVI) computed from Moderate Resolution Imaging Spectro-radiometer (MODIS) pre-processed images downloaded from the University of Natural Resources and Life Sciences (BOKU) database. Statistical analysis showed that drought severity increased over the study period while corresponding vegetation conditions degenerated. Results further revealed that the relationship between drought and vegetation greenness was significant (R² = 0.6) with 2 months optimal lag. This calls for policy makers and programme managers to integrate the lag effect in measures to cope with drought in the rangelands.

Keywords: Drought, Vegetation greenness, Chyulu-Amboseli, Statistical Analysis, Rangeland