Relationship between Space-Based Vegetation Productivity Index and Radial Growth of Main Tree Species in the Dry Afromontane Forest Remnants of Northern Ethiopia

Abstract

Investigating the relations between Normalized Difference Vegetation Index (NDVI) and tree growth is vital for quantifying ecosystem primary productivity over large spatial and long temporal scales. In this study, the relationships between forest growth (tree-ring width indices) and space-based measurement of vegetation activity (NDVI) were examined in the dry Afromontane forest remnants of northern Ethiopia. The results showed that radial growth of the main tree species (Juniperus procera, Olea europaea and Podocarpus falcatus) is positively correlated with inter-annual NDVI values. Moreover, the relationships between ring width – rainfall and rainfall – NDVI were positive and significant (p<0.05), suggesting that rainfall seasonality is an overriding growth-limiting factor in the study region. Rainfall during the wet-season largely controls cambial activities and phenological processes of the founding tree species, and hence affects overall vegetation dynamics in the region. Overall, the study showed the coupling of tree-ring growth and NDVI values with potential implications for understanding forest growth dynamics. Thus, it gives insights to the applicability of NDVI – treerings integration approach to predict landscape-level patterns of vegetation productivity

Keywords: Dry Afromontane Forest, Remote-sensing, Tree-rings