Byron Flora and Fauna Study 1999 - Byron Shire Council

A GREENPRINT FOR A SUSTAINABLE FUTURE
Davidson’s Plum (Davidsonia pruriens var. jerseyana FAMILY DAVIDSONIACEAE)
Introduction. Davidson’s Plum is one of the best known edible native fruits and is widely used for jam, sauces and wine.
It is common in cultivation, since its habit and size make it suitable for small gardens. Davidson’s Plum has a restricted
distribution in north-east New South Wales, though another variety of the species occurs in north Queensland. Targeted
surveys are in progress and a Recovery Plan will be drafted in the near future. A detailed species outline has been
compiled by Quinn et al. (1995).
Conservation status. Davidson’s Plum is listed on Schedule 1 (Endangered) of the TSC Act, 1995 and has a ROTAP code
of 2ECi (Briggs and Leigh 1996).
Habit. A small to medium tree up to 10 m tall, with large ornamental leaves (Floyd 1989).
Flowers. Pink-red, clustered in panicles in the upper leaf axils or on the leafless trunk. Flowering October to January
(Floyd 1989). Pollinators of Davidson’s Plum are unknown. The cauliflorus flowers may be indicative of mammal pollination.
Fruit. Drupe-like, black with a bluish bloom, up to 5 cm long with crimson juicy flesh (Floyd 1989). Each fruit has two
large endocarps, which are fibrous on the outside and contain a large white seed (Quinn et al. 1995). Fruit ripe January
to February (Floyd 1989). No information about seed dispersal vectors is reported by Floyd (1989). However, the fruit
characteristics are consistent with adaptation for seed dispersal by birds (Floyd 1990a). King Parrots have been observed
consuming seeds (F. Eliott pers. obs.) and may occasionally carry them from the tree. The seeds of Davidson’s Plum are
likely to be particularly prone to predation by rodents, as indicated by nursery experience (Nicholson and Nicholson
1985). Rodents eating seeds from fallen fruit may also occasionally drag seeds away from the tree and leave them undamaged.
Dispersal of seeds to a significant distance from the parents must be a rare event, but is likely to increase the chance
of successful regeneration by escaping from seed predators attracted to the tree.
Habitat. Floyd (1989) describes Davidson’s Plum as occurring on basaltic soils and riverine rainforest, while Quinn et al. (1995)
describe the habitat as subtropical rainforest at low altitudes (usually less than 300 m), and usually on red and yellow soils
of poor structure, over Silurian greywacke, slate, phyllite and quartzite. During the current survey Davidson’s Plum was
recorded in subtropical rainforest with an overstorey including Brush Box, Hoop Pine and/or eucalypt species and in one
instance in a sheltered gully in wet sclerophyll forest. In several localities Davidson’s Plum was found in regrowth rainforest
with a high percentage of Camphor Laurel, Lantana and other exotic weeds. Other trees are isolated in paddocks.
Distribution. Brunswick and Tweed Rivers, NSW. Var. pruriens occurs in North Queensland and Fiji. Var. jerseyana is
recorded from Mullumbimby; Brunswick Heads NR; Billinudgel; Mooball; Couchy Creek; Chillingham; Murwillumbah
(Floyd 1989, NPWS Atlas of NSW Wildlife). A number of additional sites in the same general areas are recorded by
Quinn et al. (1995).
Regeneration and horticulture. Seeds are quick to germinate (Nicholson and Nicholson 1985). Most subpopulations of
Davidson’s Plum consist of isolated mature trees or small numbers of clumped stems with little regeneration. Some stems
are damaged or senescing. Seedlings and saplings of Davidson’s Plum are shade-tolerant, and probably need the sheltered
conditions under at least a light canopy to establish.
Economic and cultural significance. Davidson’s Plum is an important bush food species, and the fruit has been used
traditionally by locals. Its ornamental appearance, small size and compact habit make it an attractive horticultural subject.
It also has the aesthetic and ecological values of all native rainforest trees.
Abundance and reservation. Davidson’s Plum is reasonably common locally, though the total number of mature trees is
low overall. Details of 50 locations were compiled for the study area, including seven locations newly recorded by the
authors during this study. Davidson’s Plum is reserved in the Shire only in Brunswick Heads NR and Broken Head NR,
and is considered inadequately reserved (Briggs and Leigh 1996). The populations on the Shire’s private land thus have
particular importance for the conservation of Davidson’s Plum.
Threats and amelioration. Land clearing, roadworks, damage by stock and low population numbers are listed by Quinn
et al. (1995) as threats to Davidson’s Plum. Many plants occur in vulnerable environments associated with farming,
development and roadworks. Fire is an additional threat. Upgrading and duplication of the Pacific Highway between
Brunswick Heads and Chinderah will result in the removal of a number of plants of Davidson’s Plum, including some
within Byron Shire, and bisection and removal of suitable habitat. The low level of natural regeneration in fragmented
habitat, and where trees are isolated in paddocks, suggests that Davidson’s Plums will slowly decline in their natural
environment without active management. Over-collection of fruit for bush food is also a threat.
To improve the conservation status of Davidson’s Plum, the health of the populations and their regeneration potential
should be enhanced by weed management, grazing exclusion, fire protection and replanting of surrounding habitat.
148