Maintaining diversity through intermediate disturbances: evidence from rodents colonizing rehabilitating coastal dunes

Rodents inhabit the coastal dune forests of KwaZulu-Natal, South Africa. He re habitat rehabilitation following mining of dunes has resulted in coastal dune forest succession similar to that recorded in nonmined forests. We in vestigated the colonization of rehabilitating stands and evaluate the role of disturbance in maintaining rodent diversity. A trapping programme was es tablished between July 1993 and February 1995 during which rodent colonizat ion, local extinction and species richness were recorded for rehabilitating stands of different ages. Trends in these variables were closely associate d with one of three possible outcomes for a disturbed patch over time, with no intervening disturbances following the initial disturbance. Colonizatio n was initially high which led to an increase in species richness. Extincti on was lower than colonization, but became higher when the habitat was 3 ye ars old, which led to a decline in richness. We extrapolate this result ass uming negligibly small disturbances after the initiation of rehabilitation and suggest that intermediate levels of disturbance maintain rodent species richness in coastal dune forests. Furthermore, our results illustrated spe cies turnover, a prediction of the recorded outcome, with young stands domi nated by Mastomys natalensis and older stands by Saccostomus campestris or Aethomys chrysophilus.