Twentieth century changes in montane vegetation in the eastern Free State, South Africa, derived from palynology of hyrax dung middens

Abstract

The dating and pollen analysis of a hyrax dung deposit in a mountain rock shelter (Rooiberg Shelter II) are compared with that in a previous study from the same mountain range at the rural town Clarens, in South Africa. Calibration of radiocarbon measurements from the dung deposit provides different possibilities for the age of the sequence. Unlikely dates can be eliminated on the basis of pollen stratigraphy, comparisons with a previously studied accumulation from the last 30 yr, artificially increased radiocarbon levels in the upper samples as result of nuclear arms testing after 1954, the presence of historically introduced exotic elements, and the assumption of a relatively constant rate of dung accumulation. According to these considerations we suggest that the dung started accumulating at the beginning of the twentieth century. The pollen contents show marked changes in composition, indicating mainly open grass vegetation with fynbos in the first half of this century and woody vegetation in the second half. A first marked increase of the woody component is estimated to have occurred around 1950, but it only became permanent in the 1960s. The fluctuating pollen sequence can best be interpreted in terms of the combined effects of rainfall changes, fire and stock grazing, the latter of which increased together with town expansion in the area during the course of this century. Considering historical events recorded in the area and the region in general, the results suggest that pollen in hyrax dung is a good recorder of vegetation change.