New Zealand Journal of Botany abstract
Effects of microsite characteristics on Hieracium seedling establishment
in tall- and short-tussock grasslands, Marlborough, New Zealand
ALAN B. ROSE
Landcare Research
Private Bag 1007
Blenheim, New Zealand
CHRIS M. FRAMPTON
Centre for Computing and Biometrics
P.O. Box 84
Lincoln University
Canterbury, New Zealand
Abstract The distribution and density of
Hieracium
pilosella,
H.
caespitosum, and
H.
lepidulum
seedlings were quantified at an early stage of invasion of a tall-tussock
(
Chionochloa) and a more open short-tussock (
Festuca-
Poa)
grassland. Seedling and available (unoccupied) microsites were compared in 11
stands. Recorded variables included establishment substrate, overhanging cover,
and proximity and height of neighbouring plants. Total
Hieracium cover
was <7% in both grasslands. Total
Hieracium seedling densities
averaged 126 per 100 m
2 in tall-tussock and 38 per 100 m
2
in short-tussock grassland. The three species showed wide overlap, but also
some consistent differences, in microsite characteristics. All three had
established on all substrates, over 60% of seedlings were among vegetation or
litter, and establishment was not dependent on the availability of bare ground.
The least favourable substrates were tall-tussock bases, large-herb patches,
deep litter, and rock fragments. Shorter/more open vegetation, shallow litter,
and soil were either highly favourable or had no detectable effect on
establishment. The effects of overhanging cover and canopy-plant proximity and
height were most consistently adverse for
H. pilosella and most
consistently favourable for
H. lepidulum. Although biotic barriers to
establishment were stronger in tall-tussock grassland, it had higher seedling
densities probably because it was located closer to established
Hieracium populations and was subjected to a greater seed rain.
Management of tussock grassland structure provides a key strategy for
controlling
Hieracium invasion.
Keywords safe sites; plant invasion; invasibility; vegetation
structure; tussock grasslands; degradation; Hieracium pilosella;
Hieracium caespitosum; Hieracium lepidulum
B98039
Received 30 June 1998; accepted 31 August 1998
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