Plant communities

Riparian vegetation

The highly variable riparian floodplains of the UMDR support a diversity of riparian vegetation:

  • Tableland Aquatic and Fringing Vegetation Complex dominated by macrophytes and found in wet slow-flowing areas where it also provides refuge to young and small bodied aquatic fauna ‑ good condition
  • River Bottlebrush – Burgan Tableland Shrubland dominating the rocky gorge areas with river bottlebrush (Callistemon sieberi), river tea-tree (Leptospermum obovatum) and burgan (Kunzea ericoides) ‑ good condition
  • Ribbon Gum Tableland Riparian Woodland found on the upper alluvial floodplain terraces ‑ 90% has been felled for timber and cleared for agriculture and the remaining 10% is in poor condition and is in urgent need of protection and enhancement throughout the project area
  • She-oak Tableland Riparian Woodland occurring along the river downstream of Point Hut Crossing ‑ significantly reduced vigour following the 2003 bushfires.
Dry riverine valley vegetation communities

Broad-leafed Peppermint-Apple Box Tableland Woodland, Red Stringybark-Scribbly Gum Tableland Forest, Yellow Box-Blakely's Red Gum Tableland Grassy Woodland and Burgan Derived Tableland Shrubland communities occur across the reach and are in good condition despite recent prolonged drought and fierce fires in the ACT.

The Snow Gum ‑ Candlebark Tableland Woodland has a restricted distribution and is now highly degraded. The Black Cypress Pine Tableland Woodland in the ACT has shown very patchy recovery following the 2003 fires and an ecological succession that is fire-tolerant and eucalypt-dominated is likely to replace much of it. It is in good condition where it is found in NSW.

Rare or uncommon plant species

Rare or uncommon species include the Tuggeranong lignum (Muehlenbeckia tuggeranong), Australian anchor plant (Discaria pubescens), pale Pomaderris (Pomaderris pallida), Bredbo gentian (Gentiana bredboensis), Michelago parrot-pea (Dillwynia glaucula) and Austral toadflax (Thesium australe). Some uncommon fringing species such as the quillwort (Isoetes muelleri and I. inundata) occur in the occasional small perched wetlands found in the Tableland Aquatic and Fringing Vegetation Complex.

Threats to plants

Threats to plants include weed invasion, reduced occurrence of floods, disturbance by feral animals, overgrazing and bank disturbance, and clearing of riparian margins.

Weeds particularly willows (Salix spp.), African lovegrass (Eragrostis curvula) and blackberries (Rubus fruticosus agg.) are a significant problem in all areas that are not rocky. The river also provides a convenient way for seed to spread to areas not infested.