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Using an analysis of aerial photographs from 1942, 1985 and 2004 we assessed the impact of changing land tenure and land-use regimes on the cover of thicket vegetation on the Grahamstown commonage. Land-use impacts were examined by comparing plant species composition within three vegetation types between sites incorporated into commonage for different lengths of time and sites outside the commonage. Results showed that thicket cover increased by 87% between 1942 and 1985 but declined by 11% between 1985 and 2004. The increase in thicket cover was highest on land where goat browsing and wood harvesting was excluded. There was a decline in thicket cover when uncontrolled goat browsing and wood harvesting were introduced. An analysis of plant species composition suggests an increase in the impact of livestock in areas closest to the urban area and with time since inclusion into commonage. Such areas exhibited greater cover of Increaser II grasses and dwarf shrubs in the herbaceous layer and lower cover of succulents within subtropical thicket. We interpret the decline in thicket cover and shift to a less palatable and less productive vegetation as resulting from the open-access land use system that has prevailed on the commonage since 1994. [ABSTRACT FROM AUTHOR]

We examined the effect of changes in land use and land tenure on bush encroachment and vegetation condition. An analysis of aerial photographs from three time steps (1949, 1985 and 2004) was used to document changes in woody plant density in different vegetation types on commonage and an adjacent commercial farm in Fort Beaufort, South Africa. Rangeland condition was assessed in different vegetation units of the area and woody plant density was related to distance from urban settlement. Results showed that there has been an increase in woody plant cover in both commonage and commercial farming areas, particularly between 1949 and 1985. However, since 1985, increased rates of urbanisation have stabilised, and in some areas reduced, woody plant thickening, especially at locations closest to urban settlements. Bush encroachment is being controlled to some extent by fuelwood harvesting and goat browsing, resulting in a reduction in height of favoured woody species such asAcacia karroo(Vachellia karroo). There has been a shift to less palatable browse species on the commonage areas and the condition of the grass sward is poor. Change in woody plant cover is significantly influenced by changing patterns of land use and land tenure over time which, in turn, affect rangeland condition. [ABSTRACT FROM AUTHOR]

The frequency of fire has increased in savannas yet few studies have assessed how plants persist when subjected to long-term disturbance by fire. We investigated the contributions of bark thickness and resprouting to the persistence of woody plants in two fire trials that were started in 1948 and 1949. The number of resprouts per individual, bark thickness, basal diameter and height of woody plants were measured in unburnt plots and those burnt annually, triennially and quinquennially during the late dry season. Changes in tree density, number of resprouts and individuals in different height classes between 1963 and 2002 were assessed. Bark thickness varied among species and also increased with increases in basal diameter. Generally, plants with thick bark survived fire more than those with thin bark. Resprouting was the major fire survival strategy for most species. The number of resprouts produced per plant ranged from 4 ± 3 ( Acacia rehmanniana) to 14 ± 9 ( Pseudolachnostylis maprouneifolia). Fire reduced species richness in plots burnt annually and triennially by 47% and 6% respectively. Species richness increased in unburnt plots (5%) and those burnt quinquennially (16%). Most woody species survived fire through a combination of traits. [ABSTRACT FROM AUTHOR]