Open Access  Subscription Access

In southern Africa long-term regional rainfall data sets are very limited such
that the variability of rainfall across the region is poorly understood. With
available climate records so limited the development of strong proxy records
are vital to develop drought management plans. In our continuing efforts to
develop such proxy records we present the results of an investigation into the
dendrochronological potential of Widdringtonia nodiflora and Widdringtonia
schwarzii. We sampled W. schwarzii, from the area it is endemic to,
the Baviaanskloof wilderness area, in the Langkloof region of the Eastern Cape
Province. Widdringtonia nodiflora samples were collected from the
Grootvadersbosch Nature Reserve near Heidelberg in the Western Cape Province.
The results indicate that inconsistencies in ring width combined with poorly
defined ring boundaries and converging rings make cross-dating between
different trees from the same locality an impossible task for both species
using manageable sample numbers. Without cross-dating, chronology development
is an equally impossible task for both W. nodiflora and W. schwarzii.
As with W. cedarbergensis, W. schwarzii may avoid drought stress
by accessing deep water. This may explain the many false rings and poorly
defined ring boundaries apparent in this species. This study concludes the
dendrochronological assessment of all of the Widdringtonia species with
only two South African conifers not evaluated (Podocarpus henkelii and
P. elongatus). Widdringtonia cedarbergensis is the only South
African conifer that has been successfully cross-dated,
however, there are no significant correlations between ring width indices and
climate variables for this species.

South African Journal of Botany 2003, 69:
428–433