New Zealand Journal of Botany abstract
B97006
Received 27 January 1997; accepted 27 May 1997
New Zealand Journal of Botany, 1997, Vol. 35: 525-534
0028-825X/97/3504-0525 $7.00 (c) The Royal Society of New Zealand 1997
Clematis vitalba in a New Zealand native forest remnant: does seed
germination explain distribution?
R. A. BUNGARD*
G. T. DALY
D. L. MCNEIL
A. V. JONES
Department of Plant Science
P. O. Box 84
Lincoln University
Canterbury, New Zealand
J. D. MORTON
Animal and Veterinary Sciences Group
P. O. Box 84
Lincoln University
Canterbury, New Zealand
*Present address: Department of Animal and Plant Sciences, University of
Sheffield, Sheffield S10 2TN, United Kingdom.
Abstract The pattern of distribution of the invasive vine
Clematis vitalba in a typical New Zealand native forest remnant and the
influence of chilling duration (chilling), nitrate (NO3
-), and light
on germination of
C. vitalba were investigated. In the forest remnant,
C. vitalba was not established in undisturbed forest where light levels
were <=3% full sunlight and rarely established where light levels were
<=5%.
Clematis vitalba was, however, established in forest gaps and
margins where light levels exceeded 5%, particularly when these areas were
associated with recent soil disturbance. Under controlled environment
conditions, germination in the absence of chilling, NO3
-, or light
was low (3%). When applied alone, chilling and NO3
- increased
germination. Light, however, only increased germination when applied with one
or both other factors. In the presence of light, germination increased up to
c. 80% with increased chilling (0-12 weeks), and increased up to
c. 50% with increased applied NO3
- in the range 0.1-2.5
mol/m
3 but then changed little with additional NO3
- up to
50.0 mol/m
3. In general, germination in the presence of two or three
factors was greater than when either factor was applied alone.
In the field, seeds remaining on vines over winter retained a high degree of
dormancy and viability. We suggest that sporadic release of this seed
effectively produces a seed bank. By comparing the levels of chilling,
NO3-, and light that can be expected in the field with the levels
that influence germination under controlled environment conditions, and
considering a seed bank, we argue that C. vitalba is likely to rapidly
establish following soil disturbance. We suggest that rapid establishment may
account for the distribution of C. vitalba in recently disturbed, high
light sites and, to some extent, the success of C. vitalba in New
Zealand native forest remnants.
Keywords Clematis vitalba; New Zealand native forest
remnant; germination; dormancy; chilling; light; nitrate
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