Influence of Climate Variation on Growth of Tropical Tree Species in Western Kenya

Aims: Growth-climate relationships were examined in 7 tropical tree species growing in the Yala river basin of western Kenya: Acacia mearnsii, Cupressus lusitanica, Eucalyptus camaldulensis, Eucalyptus grandis, Eucalytus saligna, Mangifera indica, and Markhamia lutea.

Methodology: Standardized basal area increments were correlated with monthly and seasonal (3 month periods) climate variables (precipitation, mean temperature, Climate Moisture Index) obtained from nearby meteorological stations.

Results: A majority of the tree species (M. indica, C. lusitanica, E. camaldulensis, and E. saligna) showed positive correlations with monthly and seasonal precipitation and moisture index during periods of the long and short rainy seasons. This study also revealed significant correlations between monthly and seasonal temperature data and radial growth of M. indica, M. lutea and E. grandis. Growth of M. lutea was negatively affected by cool growing season conditions while M. indica and E. grandis experienced high temperature stress.

Conclusion: Associations between radial growth of tropical tree species and temperature are generally rare in warm tropical regions, and for some of the species examined in this study that are non-native (i.e., M. indica and E. grandis), strongly suggests that they may be growing outside the optimal temperature conditions of their native geographical range.