New Zealand Journal of Botany
abstracts
Evidence for rising upper
limits of four native New Zealand forest trees
P.WARDLE*
M. C. COLEMAN†
DSIR Land Resources
Private Bag, Christchurch
New Zealand
*Present address: Landcaie Research New Zealand
Ltd, P. O. Box 69, Lincoln, New Zealand.
†Present address: Landcare Research New Zealand
Ltd, P. O. Box 31-011, Christchurch, New Zealand.
Abstract
Since the 1860s New Zealand mean air temperatures have risen about
0.5°C, which might be expected to have led to a rise of about
100 m in altitudinal limits of plants. Four tree species were examined
at several South Island localities for evidence of such a rise. Young
silver beech plants have established above the upper limit of mature
trees, mostly within the last 60 years. However, as beech timberlines
are strongly buffered, few of these young plants occur more than 9 m
from the forest margin. Above mountain beech timberlines, which lie in
drier climates east of the Main Divide, the "advance zone" is usually
less than 7 m wide, and does not include the exposed spurs and
northerly faces where timberline ascends highest. Above the limit of
mature red beech trees, there is a zone in which younger red beech, up
to 150 years old, occur through nearly 30 m of altitude. Scanty data
for miro suggest a still wider advance zone. The difference between the
potential altitudinal rise of upper limits and that which is actually
achieved suggests that in the event of rapid and substantial climatic
change, species with intrinsically slow rates of spread would be unable
to keep pace. Those with narrow environmental ranges could be B91037
Received 20 August 1991; accepted 23 July 1992 threatened with
extinction unless managed so as to assist dispersal and establishment.
To substantiate the prima facie findings of this study, transects have
been set up to monitor long term future changes.
Keywords
altitudinal limits; climate change; mountain beech; Nothofagus; red
beech; silver beech, timberline
B91037 ; Received 20 August
1991; accepted 23 July 1992
New Zealand Journal of Botany,
1992, Vol. 30: 303-314
0028-825X/92/3003-0303 $2.50/0 © The Royal Society of New
Zealand 1992
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