Vegetation Response to Rainfall and Soil Moisture Variability in Botswana
1991
Farrar, Tammy J.
This paper presents the results of a study of the relationships between rainfall, soil moisture, and the Normalized Difference Vegetation Index (NDVI) in Botswana. Soil moisture values were calculated via a surface hydrologic model. Spatial and temporal relationships between the variables were examined through statistical analyses. Time series were evaluated and linear regressions/correlations were performed on the data according to vegetation and soil type. Good agreement between NDVI, rainfall, and soil moisture was found on both monthly and annual time scales. The NDVI cycle was found to lag that of rainfall by 1-2 months, but no lag was evident between the NDVI and soil moisture cycles. The relationships between the variables indicate that NDVI may be used in climatic studies to monitor rainfall and soil moisture variations. The dependence of the interrelationships upon soil composition is presented. Best relationships are found for soils with relatively even mixtures of sand and clay. In addition, the sensitivity of the hydrologic model to variations in clay content is shown.
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