Browsing by Author "Skowno, Andrew L"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Open Access
    The effects of habitat change on bird diversity and community structure in a mesic Savanna landscape
    (2000) Skowno, Andrew L; Bond, William J
    Many conservation areas are effectively islands in a sea of agricultural or urban development in which natural disturbance regimes have been altered or limited. Managers of such areas often need to artificially maintain disturbance regimes in order to control ecosystem processes such as vegetation succession (Richards ef al. 1999). The relationship between disturbance, succession, vegetation change and habitat heterogeneity is crucial to managers because together they can influence biodiversity. For example, a break in the disturbance regime could promote woody plant encroachment. Though this might lead to an increase in habitat heterogeneity, the effects on biodiversity could be positive or negative. Habitat heterogeneity, in this context, can refer to vegetation variability or complexity at a range of spatial scales.
  • Thumbnail Image
    Item
    Open Access
    The successional dynamics of Acacia nilotica (L.) savanna
    (1996) Skowno, Andrew L; Midgley, Jeremy J
    Analysis of aerial photographs indicates that woody plant biomass has increased in Hluhluwe Game Reserve, KwaZulu Natal, over a relatively short period. Despite their slow growth rates, Eucleas and other broadleaf species are responsible for the majority of this increase. Nine sites were chosen to examine the recruitment patterns and sizeclass distributions of Euclea divinorum and E. racemosa. Analysis of the size-class distribution data suggests that recruitment of Eucleas is slightly higher below adult A. nilotica canopies than in adjacent interspaces. The number of seedlings is significantly higher below Acacia canopies than in open spaces. Size class data indicate that the largest Euclea individuals are found in open spaces and not below A. nilotica canopies. Because Eucleas have slower growth rates than A. nilotica, the large Eucleas may well have become established before the present A. nilotica stand. The data also indicate that A. karroo is replacing A. nilotica and that broadleaf species other than Eucleas are recruiting in both open and below canopy plots. I suggest A. nilotica adults only weakly facilitate the establishment of Eucleas and other broadleaved species, and that increase in woody vegetation is due to changes in the fire regime that allow suppressed broadleaf individuals to escape and become visible. This release may explain the rapid rate of encroachment by inherently slow growing species.