Grassroots Vol 20 No 3 | Page 19

FEATURE along a 50 m transect into the thicket and 50 m into the transformed area. The thicket patches were well utilized and were more open than we expected when viewing from the road. The transformed patches were very open and have been so for about forty years. These areas have been exposed to herbivory by Elephant (Loxodonta africana), Kudu (Tragelaphus strepsiceros), African Buffalo (Syncerus caffer) and Red Hartebeest (Alcelaphus buselaphus caama). Warthogs (Phacochoerus africanus) are also common utilizers of the transformed areas. Results from soil samples % Soil moisture 35 30 25 20 15 10 5 Thicket transformed boundary Our results were surprising, with the highest soil moisture at the 40 m mark from the thicket-transformed boundary, in the transformed area. This is probably due to a rainfall event shortly before sampling. Work by Cowling and Mills (2011) show that rainfall interception by thicket canopy is some of the highest in the literature, and where rainfall events are small (<5 mm) there is very little water reaching the soil. The soil moisture response in this area would explain the preference of the animals for these transformed patches as the higher soil moisture will produce more green leaf as long as it lasts. As expected, the soil in the transformed area was more compacted than in the thicket area, making it more difficult for seeds to establish and for rainwater to infiltrate (Sigwela et al. 2009). Nitrogen in the soil was higher in the thicket area, which is likely to be associated with higher levels of protein in the associated vegetation, or indicative of the de-coupling of the nutrient cycle in the transformed habitat leading to steady-state of leakage. 0 Figure 4: Percentage of soil moisture in the transformed and thicket areas. Penetromer Kg/m 2 4 3,5 3 2,5 2 1,5 1 0,5 0 Transformed 40m Transformed 20m Thicket 20m Thicket 40m Vegetation type Transformed 40m Transformed 20m Thicket 20m Thicket 40m Vegetation type Figure 5: Soil compaction measured with a penetrometer in kg/m 2 Red line indicates the thicket-transformed boundary. Thicket transformed boundary There were also large differences in the vegetation between the two areas. The thicket areas had 17 woody species with 462 individuals. The most common woody species in these utilized thicket areas were Azima tetracantha (Beesting bush) with 73 individuals and Euclea undulata (Common Guarri) with 61 individuals. Euclea is fairly unpalatable (Haschick & Kerley 1997) and their unpalatability may explain why they seem to dominate the well-utilized xeric thickets. Of the more palatable and typical thicket species, there were only 19 individuals of Portulacaria afra (Spekboom) in the 1 500 m 2 surveyed in the thicket and 47 individuals of Schotia affra (karroo boerbean). In the transformed area only nine woody species were found with 104 individuals. These were mainly Gymnosporia (spikethorn) species which amounted to a total 85 of the woody individuals found in the 1 500 m 2 of the transformed area. The woody plants in the transformed area seemed to be well utilized as the average height of the vegetation in the transformed area was only 10 cm compared to the average height of 93 cm in the utilized thicket. Individual woody plants also covered a smaller area in the transformed area with an average of 24 cm compared to 95 cm in the intact thicket. During the survey in May there were no grasses recorded, with the forb layer dominated by a succulent vygie; Drosanthemum. What do these results contribute to understanding the value of thicket patches? Patches in the thicket are often cleared to provide forage to herbivores. These transformed areas are frequently dominated by grasses and provide highquality forage with lots of valuable young green leaf to domestic and wild animals during the growth season. The thicket, even when well utilized, covers more nutrient-rich, less compacted soils Grassroots Vol 20 No 3 September 2020 18