Abstract:
Understanding the spatio-temporal dynamics of land surface phenology is important to
understanding changes in landscape ecological processes of semi-arid savannas in Southern Africa.
The aim of the study was to determine the influence of variation in tree cover percentage on land
surface phenological response in the semi-arid savanna of Southern Africa. Various land surface
phenological metrics for the green-up and senescing periods of the vegetation were retrieved from
leaf index area (LAI) seasonal time series (2001 to 2015) maps for a study region in South Africa.
Tree cover (%) data for 100 randomly selected polygons grouped into three tree cover classes, low
(<20%, n = 44), medium (20–40%, n = 22) and high (>40%, n = 34), were used to determine the
influence of varying tree cover (%) on the phenological metrics by means of the t-test. The
differences in the means between tree cover classes were statistically significant (t-test p < 0.05) for
the senescence period metrics but not for the green-up period metrics. The categorical data results
were supported by regression results involving tree cover and the various phenological metrics,
where tree cover (%) explained 40% of the variance in day of the year at end of growing season
compared to 3% for the start of the growing season. An analysis of the impact of rainfall on the land
surface phenological metrics showed that rainfall influences the green-up period metrics but not the
senescence period metrics. Quantifying the contribution of tree cover to the day of the year at end
of growing season could be important in the assessment of the spatial variability of a savanna
ecological process such as the risk of fire spread with time.
