Fragmentation of South African renosterveld shrublands: effects on plant community structure and conservation implications

Nearly 85% of South Coast renosterveld, a fire-prone shrubland, has been re placed by agriculture; the remaining areas are small fragments scattered th roughout agricultural lands. Because nearly all of the remaining vegetation is required to fulfil a modest reservation target, conservation of these f ragments will be central to any implementation plan. To assess the conditio n and, therefore, the conservation potential of these fragments, we investi gated the community patterns, species diversity and representation of biolo gical attributes in 23 renosterveld fragments. Communities in large fragmen ts were more similar to each other than those in small fragments. There wer e no significant linear relationships between species diversity and fragmen t area. We found weak fragmentation effects in attribute representation. Nu mbers of alien graminoid species and total alien species, and frequency of individuals of geophyte species increased with decreasing fragment size. Fr equency of individuals and percentage cover of species with seeds that are dispersed for short distances, increased with decreasing fragment size, whi le percentage cover of perennial graminoids decreased. Small fragments are highly disturbed by grazing, trampling, crop spraying and frequent fires, b ut retain a similar community structure to large fragments that presumably represent the pre-agricultural matrix vegetation. Therefore, all remnants o f renosterveld, irrespective of fragment size, should be considered conserv ation-worthy. (C) 1999 Elsevier Science Ltd. All rights reserved.