Riverine vegetation includes riparian vegetation associated with the stream or river channel and bank, and floodplain vegetation associated with alluvial flats adjacent of the bank. Riverine vegetation provides multiple benefits within rural landscapes. It influences in-bed physical form and prevents erosion and incision, provides terrestrial and aquatic habitat, and facilitates movement of fauna across the landscape.Floodplain vegetation is unique in the landscape, commonly comprising extensive native grasslands and grassy open woodlands which are not represented elsewhere.The riverine vegetation of most NSW catchments, particularly the floodplain component, has been cleared extensively over the past 150 years for cropping and pastoralism, so that only fragments of the original extent remain. It is important that those who manage remaining areas of riverine vegetation are aware of their inherent condition, so that informed decisions can be made about prioritisation for conservation and management.The total area of the riverine zone in the Namoi catchment in north-western NSW exceeds 10,000 km2, about 25% of the catchment area. It includes over 8,000 km of major streams and rivers within 40 sub-catchments, dominated by either river oak (Casuarina cunninghamiana) or river red gum (Eucalyptus camaldulensis) types, with various other riparian types less common. The floodplain represents about 90% of the riverine zone, and includes major cotton and other cropping areas of the Namoi valley, such as the Liverpool Plains and Walgett Plains. Native vegetation of the floodplain includes open grassy woodlands dominated by Poplar Box (Eucalyptus populnea), Black Box (Eucalyptus largiflorens) and Coolibah (Eucalyptus coolabah), and also true native grasslands dominated by Plains Grass (Austrostipa aristiglumis). A total of 30 regional vegetation communities (RVCs) occur in the riverine zone.An estimated 35% of the riparian zone and 7% of the floodplain zone comprises woody cover in the Namoi, indicating substantial loss of native tree cover in the past. About half the original native vegetation of the Namoi floodplain has been displaced by cropland - most other treeless areas support native grasslands derived from former grassy open woodlands (although areas of true native grassland also remain). The majority of the cleared riparian zone also constitutes derived grassland.This study was commissioned by Cotton Catchment Community CRC and Namoi CMA to develop and apply a framework for evaluating and mapping the condition of native riverine vegetation (riparian and floodplain) in the Namoi catchment. A framework was developed that measured condition using:i. a combination of landscape metrics derived from remotely sensed data,ii. a plot-based sampling program designed to capture ecological data and score them against established benchmarks.The landscape condition assessment used metrics such as %-woody cover, %-nonnative, continuity of vegetation along rivers, and connectivity. Through the combined influence of all landscape metrics, the assessment established that the best 'condition' sub-catchments were associated with large contiguous blocks of vegetation such as in the Pilliga. Conversely, the worst 'condition' sub-catchments were associated with extensively cleared lowlands, such as the Liverpool Plains.The plot-based assessment of vegetation condition sampled a total of 329 plots across the Namoi riverine zone, including 91 on the floodplain and 238 along major channels. A number of ecological attributes, including %-cover and species richness in the canopy, midstorey and understorey, number of large trees, and length of dead fallen timber were measured consistently in each plot. A set of 'benchmarks' was established for each RVC (one benchmark for each ecological attribute) from which plot data could be compared and scored to a maximum value of 100. Vegetation was scored for all 329 sampled plots, providing a final vegetation condition score at each plot.Vegetation condition varied from 98/100 (best condition) to 2/100 (poorest condition), with an overall mean score of 55/100 across all plots sampled in the Namoi catchment. Absence of large and recruiting trees and low shrub diversity and cover appeared to influence condition the most. Three major patterns were observed from the plot data:1. Remnant floodplain vegetation appeared to be in better condition than riparian vegetation;2. Riparian vegetation of upland areas associated with pastoral activities was in poorer condition than that in lowland channels associated with cropping;3. Condition of native remnant vegetation within cotton growing areas was almost identical to that outside cotton growing areas.These observations indicate that the cotton and other cropping industries do notadversely affect the inherent condition of remnant native vegetation relative to other agricultural land-uses in the Namoi (in fact the converse might be true), although the extent to which native floodplain vegetation has been removed and displaced by cropping is likely to be compromising landscape functionality, in terms of provision of effective habitat and facilitation of species movement via corridors of native vegetation.The results are encouraging for the cotton industry because they provide evidence that an effective network of habitats and corridors might be secured and managed to support and improve the conservation of native vegetation, and local fauna and flora species within the Namoi floodplain, while maintaining and developing the cotton industry. It is important that Namoi CMA now commit to better mapping and sampling intact areas of floodplain vegetation, working with landholders and the Cotton CRC to protect the larger areas, and developing a revegetation strategy which aims to link strongholds of good condition native vegetation across the riverine landscape.While some regional priorities for conservation works are proposed - these target good condition floodplain and riparian vegetation - a broader strategy of targeted river reach revegetation is also proposed which aims to improve vegetation condition along significant river reaches in the short term. The strategy requires direct tree (and some shrub) planting over sections of major streams and rivers in which recruitment is lacking and canopy cover is poor, with hands-on protection through the first years of establishment. The Namoi River itself is suggested as a starting point, as a long term goal might be achievement of a continuous east-west riparian corridor through the valley. The program would be focus on working with multiple rather than single landholders.Comparison of landscape-derived and plot-based condition scores provides evidence of a positive correlation, with inherent condition generally greater than surrounding landscape condition. However the relationship is weak, suggesting that local condition of riverine vegetation cannot be confidently predicted from landscape-generated estimates of condition, and that field assessment is ideally required to evaluate vegetation condition on the ground.Outcomes of plot-based sampling demonstrate that a robust estimate of average vegetation condition can be established for any geographic region or entity, such as sub-catchment or stream order, if an adequate number of plots are sampled therein. It follows that estimation of change in vegetation condition is also achievable from year to year, or at regular intervals, if a minimum number of plots are sampled and average condition re-derived. Plot-based condition sampling could readily be employed to monitor, evaluate and report changes in riverine vegetation condition (riparian and floodplain), thus addressing key responsibilities of the Namoi Catchment Action Plan (CAP). The sampling protocol has been designed to undertake sampling rapidly and repeatedly, and is consistent with vegetation condition assessment protocols used in New South Wales, Queensland and Victoria.
