Phenology of woody plants in riverine thicket and its impact on browse availability to game species

Abstract

The study area was located in the central Free State Grassland biome, but the vegetation partially represented riparian thicket. Leaf carriage patterns of deciduous species were determined from September 2004 to August 2008. Similarities existed between Acacia karroo and Diospyros lycioides – mature leaves were present from October to April, with some dry leaves retained until June. Ziziphus mucronata had mature leaves from December to May with dry leaves retained until August. Mature leaves of Searsia pyroides were present from November to March and dry leaves until June. Though statistically non-significant, large A. karroo trees shed leaves faster than smaller trees. Differences were observed in phenology between years. Minimum temperature was strongly correlated with leaf phenology. Rainfall was weakly correlated with leaf phenology, though above-average rainfall resulted in increased growth of shoots and leaves. The few semi-deciduous shrubs retained mature leaves for longer periods, normally until September, and were extensively browsed. The winter-deciduous nature of woody species and absence of evergreen species have serious consequences for introduction of browsing game species on small fenced properties. The critical period, when browse was limited, is from July/August to mid-October; unless stocking rates are kept low this will necessitate the supply of feed.

Keywords: foraging ecology, leaf budding, leafless period, mixed feeder, seasonal changes, senescing leaves

African Journal of Range & Forage Science 2011, 28(3): 139–148