Rogers et al.—Trends in spring annual herbs

New Zealand Journal of Botany abstracts

Land use effects on "spring annual" herbs in rare non-forest ecosystems of New Zealand

Geoffrey Rogers

Research, Development, and Improvement Division
Department of Conservation
PO Box 5244
Dunedin 9016, New Zealand

Jacob McC. Overton

Robbie Price

Landcare Research
Private Bag 3127
Hamilton 3216, New Zealand

Abstract We examined trends over six consecutive spring seasons in three "spring annual" herbs, Myosurus minimus subsp. novae-zelandiae (Ranunculaceae), Ceratocephala pungens (Ranunculaceae), and Myosotis pygmaea var. minutiflora (Boraginaceae), in terms of their habitats and site land uses in several rare, non-forest ecosystems. On dry hillslopes, saline soils, and turfs of ephemeral wetlands (including coastal turfs), Ceratocephala and Myosotis declined where sites were managed for conservation by removal of mammalian herbivores. Some populations of Myosurus declined only marginally or remained stable despite high cover of ruderal and weedy, herbaceous exotic plants. Loss of monitored populations during the study was offset by discoveries of additional populations of all three taxa. Statistical models of population trends suggest that in some instances spring annual populations benefit from farm animal and rabbit (Oryctolagus cuniculus cuniculus) disturbance of their habitats perhaps by 1) suppressing transitions to taller vegetation and retarding competition of invasive exotic plants and 2) maintaining nutrient supplementation from faeces lost with the extinction of ground-dwelling birds. Frequent seeds of all three taxa preserved in moa coprolites from several sites in Central Otago point to 1) the herbs' probable non-rarity in pre-human times and 2) dispersal mutualisms and mediation of community ground cover by extinct ratites.

Keywords annual plants; spring annuals; New Zealand; Myosurus; Myosotis; Ceratocephala; land use; herbivores

B06035, Online publication date 2 May 2007; Received 18 August 2006; accepted 19 March 2007

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