New Zealand Journal of Botany abstracts

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Effect of Coriaria arborea on seed banks during primary succession on Mt Tarawera, New Zealand

Beverley R. Clarkson

Landcare Research
Private Bag 3127
Hamilton, New Zealand

Lawrence R. Walker

Department of Biological Sciences
Box 454004
University of Nevada
Las Vegas, Nevada 89154-4004, USA

Bruce D. Clarkson 

Warwick B. Silvester

Centre for Biodiversity and Ecology Research
Department of Biological Sciences
University of Waikato
Private Bag 3105
Hamilton, New Zealand

Abstract   An experiment was conducted over two years to investigate the effect of Coriaria arborea, a native nitrogen-fixing shrub, on soil seed banks at sites representing a post-volcanic successional sequence on Mt Tarawera, New Zealand. The sites ranged from bare volcanic ash and lapilli substrate, through low-growing pre-Coriaria vegetation, to dense stands of Coriaria scrub. Soils (to a depth of 50 mm) under recently established Coriaria and older stands had more seedlings (1096 and 1585 seedlings 0.4 m^-2, respectively) and species (37 and 45 species 0.4 m^-2, respectively) emerge than where there was no Coriaria (243-320 seedlings 0.4 m^-2, 14-25 species 0.4 m^-2) and were the only soils with Coriaria seedlings. In total, 3488 seedlings representing 63 taxa were recorded. Seeds were still germinating after 24 months but rates declined markedly in the second year. For example, Coriaria reached a germination peak at 8 weeks but continued to germinate sporadically over the 2-year period. Tree species present in young forest within 0.5 km of the sites were absent. Establishment of Coriaria greatly accelerated an underlying trend of gradually increasing abundance and diversity of seeds in the soil with vegetation age. Adventive, wind-dispersed, and annual species were over-represented in the seed banks compared with the regional evergreen forest-dominated flora. These proportions are expected to decline as succession to forest gradually occurs.

Keywords   Coriaria arborea; Mt Tarawera; nitrogen fixation; seed bank; volcanic primary succession

B02005 Received 23 January 2002; accepted 6 August 2002; published 28 November 2002
New Zealand Journal of Botany, 2002, Vol. 40: 629-638
0028-825X/02/4004-0629 $7.00 © The Royal Society of New Zealand 2002

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