Acacia dealbata subalpina

Acacia dealbata subsp. subalpina, commonly known as the Monaro or subalpine silver wattle, is a bipinnate-leaved wattle native to south-eastern Australia, occurring across the tablelands of south-eastern New South Wales, the ACT and north-eastern Victoria, including the Brindabella Ranges and Namadgi ranges. It occupies the higher-altitude end of the A. dealbata range, typically above 700 m, distinguished from the widespread lowland subsp. dealbata mainly by its smaller stature and smaller leaves.

Description

The subalpine silver wattle is a bushy shrub or small tree, typically to 3–5 metres, rarely to 10 metres — markedly smaller than subsp. dealbata, which can reach 30 metres. Bark is smooth and grey to greyish-brown when young, becoming fissured and corrugated with age. Branchlets are angled toward the tips, ridged, finely hairy and carry a waxy, glaucous bloom. The bipinnate leaves are glaucous, bluish-grey to silvery, and notably shorter than typical dealbata foliage 1.5–8.5 cm long, with 6–20(–22) pairs of pinnae 0.5–2.5 cm long, each bearing pinnules only 0.7–4 mm long. A single rounded, tomentose jugary gland sits at the base of each pinna pair; interjugary glands are absent. Flowers are borne in globular heads of 13–34, pale to bright — often golden yellow, produced from late winter into spring.

Habitat and ecological role

Subsp. subalpina favours forest, woodland, grassy areas, streambanks and wet gullies at tableland and subalpine elevations, generally above 700 m. Where its altitudinal range meets that of subsp. dealbata on lower slopes, intermediates between the two are common this has been recorded at Mt Franklin, ACT, where subsp. dealbata grows as trees to ~14 m on the lower slopes and subsp. subalpina forms bushy stands to ~3 m higher up. As with other wattles, it contributes nitrogen fixation and understorey structure to the communities it grows in, and its smaller stature suits it to more exposed, higher-elevation sites than the lowland subspecies can tolerate.

Position in this vault

Acacia dealbata subsp. subalpina represents the higher-altitude, subalpine form of the wattle lineage in the Brindabellas, sitting alongside and grading into subsp. dealbata as elevation decreases.

Notes

• Described in 2001 (Kodela & Tindale, Telopea 9(2): 319–322)
• Source: NatureMapr — Canberra & Southern Tablelands