Demography and conservation of botrychium australe, a peculiar, sparse mycorrhizal fern

Abstract

Botrychium australe is a sparse native fern which is demographically unusual in having only a single leaf at any one time and in probably being strongly mycorrhizal. Individual plants of B. australe were mapped and followed at Cass, inland Canterbury, from 1987 to 1993. Plants were long-lived, with a mean half-life of 11.2 years. Some plants (21%) failed to produce any above-ground tissue in 1 or 2 years but later resumed normal growth. Up to 14% of plants were missing in this way in any one year. It is not known if this represents subterranean predation of fronds or quiescence while the fern is supported by mycorrhizae. Demographically, B. australe is more similar to some orchids than to other ferns. In any one year, only 9–20% of plants produced fertile spikes with sporangia. Fertile spike production was strongly correlated with higher light intensity; plants in deeper shade (<10% of full light) were very unlikely to be fertile. Plants in deeper shade also had larger sterile (green) fronds. The major identifiable cause of death was pig rooting, especially in 1989; over all years, 41% of deaths were attributed to pigs. B. australe appears to be detrimentally affected by shading by woody plants, and favoured by disturbance. Persistence of its populations may be enhanced by occasional disturbance (e.g., burning) where this does not conflict with other management aims. © 1994 Taylor & Francis Group, LLC.