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The natural flow regime and the relationship between flows and riparian vegetation are described for sites on both the Blackwood River insouth-western Australia and the Ord River in north-western Australia. Analysis of long-term flow data showed the historic mean monthly river discharge for the Blackwood River is strongly seasonal and highlypredictable with generally low variability each month. The Ord Rivershowed a strong seasonality of flows with about 92% of the (total) yearly flow occurring between December and March. Flow variability wasvery high (e.g. coefficient of variation >100% for all months) but highly predictable, with this mostly attributed to low but constant dry-season flows. Water depth, duration of flood events and the number of flood events per year show a significant correlation with aspects of the riparian vegetation within experimental vegetation plots. Results highlight the strong relationship between floristics, life form structure and population dynamics with stream hydrology. On the Blackwood River, species richness and cover of shrubs reduced with increased duration and frequency of flooding, while cover of exotic species and annual herbs increased with increased flooding. Germination of tree seedlings was not influenced by flood regime but size class of treespecies increased with flooding frequency. On the Ord River, speciesrichness was not influenced by flooding regime. However, cover of perennial grasses increased with flooding frequency whilst cover of shrubs decreased. There was no relationship between flooding and seedling establishment whilst tree size class decreased with increased flooding. The methods described here can be used to compare the response of different components of the riparian vegetation to different fluvial regimes (e.g. because of impoundment and abstraction). This technique can be expanded for the management of riparian zones and planning rehabilitation programs. It may also be useful for improving the ecological [ABSTRACT FROM AUTHOR]

Water elevation in the Upper Mississippi River (UMR) is highly regulated by an extensive system of locks and dams. Completion of this system in the 1930s created productive, biologically diverse backwater habitats. The status of plant communities in these backwater areas maynow be threatened by several factors, including sediment accumulation, recreational use, and navigation traffic. Aerial photography, taken in 1975 and from 1991 to 1995, was used to describe vegetation changes occurring in four UMR backwater areas of Navigation Pool 8. The objectives were to determine (1) if changes occurring in these areas are consistent with hydrarch succession, (2) if the diversity of theirplant communities has declined since 1975, and (3) how a large floodevent that occurred in 1993 affected the composition and diversity of plant communities in these areas. Three general cover classes were recognized, representing an aquatic to terrestrial gradient. Coverages of specific vegetation types were estimated and evaluated using twoindices of community diversity (vegetation richness and the Shannon diversity index). Though some vegetation changes were consistent withexpected successional patterns (e.g. increased terrestrialization), other changes were not (e.g. loss of marsh vegetation). Diversity indices and coverages of most aquatic macrophytes declined from 1975 to 1991/1992 but then increased following the 1993 flood. The results suggest that disturbance-diversity concepts, including the flood pulse model, are applicable to the vegetation dynamics of these systems. [ABSTRACT FROM AUTHOR]

Visual estimates of macrophyte cover in Murray and Ovens River billabongs were unrelated to farming and regulation activities, but were positively related to the ratio of Chydoridae to total Cladocera in assemblages of skeletal remains from surface sediments. This ratio (%CHYD) was thus used as a surrogate for macrophyte cover in a palaeoecological analysis. Values of %CHYD were lower in sediments deposited after European settlement than in the pre-settlement parts of sediment cores from three relatively large deep billabongs, and two moderately-sized billabongs, reflecting an historical contraction of the littoral zone in these billabongs. No evidence of a contraction in the littoral macrophyte zone was found in historical records from the two smallest billabongs, although the records were of poorer quality. Visualestimates of macrophyte cover confirmed that macrophytes were generally found in small or shallow billabongs, and that large deep billabongs were macrophyte poor. The timing and spatial pattern of the historical decline in macrophytes implicates an early farming activity as the cause. Control billabongs, at present remote from farming centres, have evidence of historical farm impacts which may explain why visual estimates of macrophyte cover and farming are unrelated. Use of the floodplain by farmers may have declined recently, and the historical pattern of macrophyte cover suggests that a naturally stable state of algal dominance has prevented macrophytes from recolonizing large deep billabongs. Evaluations of the role of billabongs in river-floodplain functioning and river-floodplain management strategies must take into account the historical impacts of farming on macrophyte cover.Methods for assessing billabong health that rely on comparisons of affected and non-affected sites (cf. RIVPACS; Wright, 1995) will not work in this region. Attempts to rehabilitate rivers through environmental flows will fail unless steps are taken to remedy farm impacts. [ABSTRACT FROM AUTHOR]

The composition and distribution of littoral vegetation in four weirpools of the lower Murray were surveyed in summer 1994. Between-weirgradients in the amplitude of water level fluctuations were reflected in the typical distributions of plants, with a 4-6 m elevational range in upper-pool sites, where levels fluctuate most, and a 1-1.5 m band in the lower-pool sites, where levels are more stable. Forty-one of 48 species occurred across much of the longitudinalx elevational site matrix within this cone-shaped distribution, indicating considerable tolerance to flooding and exposure; this was especially apparent for Phragmites australis, Cyperus spp. and Centipeda spp. The 41 species were represented in seven of nine water-regime groups identified by cluster analysis. The remainder, found within 1 m of the water surface in lower-pool reaches, were aquatic macrophytes such as Vallisneria americana and Typha spp. and amphibious mudmats' such as Glossostigma elatinoides. Water regimes at given sites were measured by the number of days in 2 years flooded to any depth (>0 cm), or to 0-30 cm,and by days exposed by >100 cm. Inter-pool differences in the mediannumber of days flooded to >0 cm and 0-30 cm were 3-30% and <8%, respectively, for all species except Typha spp. but an order of magnitudefor the number of days exposed by >100 cm. However, eight of 14 common or representative species analysed showed significant inter-pool differences in the number of days flooded to >0 cm, indicating that sufficient variation exists to necessitate considerable intra-pool replication to allow for the detection of statistical differences in a multi-pool experiment. The practice of maintaining stable weir pool levels limits vegetation processes, e.g. germination, recruitment, decomposition. An increase in the amplitude of river level fluctuations during low flows, from the current 10-20 cm range to 20-50 cm, would reinstate water regimes suitable to the majority of species surveyed [ABSTRACT FROM AUTHOR]

Vegetation structure and composition and the mass of components of organic detritus were assessed in paired areas, with and without stockaccess, at six sites. The study revealed that grazing has altered and continues to alter the structure and function of the riparian landscape in the Murrumbidgee River and its tributaries in southeastern Australia. Seedlings and saplings of the dominant Eucalyptus tree species were up to three orders of magnitude more abundant in areas with no stock access, and the biomass of groundcover plants was an order ofmagnitude greater in areas with no stock access at all sites. Plant species richness did not differ between areas with and without stock access when the ameliorating effect of canopy tree density was taken into account, but plant community composition differed significantly between areas at all sites. Coarse particulate organic matter and terrestrial fine woody debris were consistently more abundant in areas without stock. In-stream fine and coarse woody debris was more abundant in areas without stock at mainstream sites, but not in tributaries.The percentage of bare soil was greater in areas with stock access at all sites. Differences between areas with and without stock access were generally most pronounced at sites where the riparian zone had been excluded from stock access for more than 50 years. The effects oflivestock on vegetation and components of detritus have a significant influence on the function of riparian zones. Efforts to restore river health that focus solely on reducing the impact of regulated flowsmay be nullified if livestock grazing is not considered as part of river ecosystem management. [ABSTRACT FROM AUTHOR]

During floodbank raising work as part of a major capital flood defense scheme on the River Torne between 1985 and 1990, selected reaches of the main trapezoidal channel were enhanced. By winning spoil from the channel margins and from borrow pits in the floodplain, a more varied marginal zone was created which maximized the potential habitat for wetland plant communities and their associated fauna. Enhancementcomprised bank re-profiling to create narrow wetland shelves (berms), shallow bays, channel margins of varying shape and depth and linearstill ponds from the borrow pits. The 1990 planting program comprised 11 macrophyte species and a total of 7740 individual plants. This paper reports on an initial study to evaluate the marginal habitat enhancements on the River Torne 5 years after completion of the project.Lack of pre-scheme data necessitated a space-time substitution; enhanced river margins were compared with neighboring reaches that had undergone conventional floodbank repair and remained as trapezoidal channel sections planted with a standard, low maintenance seed mix. Marginal vegetation was surveyed and supported by measurements of the physical habitat at 10 enhanced and 10 conventionally-engineered reaches. The macrophyte surveys and the results from the cluster analysis and polar ordination indicate that enhanced and conventionally-engineered reaches are floristically distinct and that the enhanced reaches have a more varied macrophyte community. The results from the Mann-Whitney U-tests show that enhanced reaches have significantly higher values of wetland species diversity and equitability, percentage of wetland species, bank width and soil moisture and significantly lower bank angles. However, the correlation and linear regression analyses didnot show any strong associations between the physical habitat and plant parameters. [ABSTRACT FROM AUTHOR]

Breeding of herbicide-resistant foxtail millet (Setaria italica (L.)Beauv.) is desirable in modem agriculture because no selective herbicide is available for this crop. Trifluralin-resistant millet lines obtained from a interspecific cross between a resistant green foxtail (Setaria viridis (L.) Beauv.) and a foxtail millet cultivar were tested for response to five dinitroaniline herbicides in greenhouse and field experiments. The results in the greenhouse study showed that theresistant type was cross-resistant to all tested herbicides. ED{sub}50{end} values indicated that the highest resistance was obtained with trifluralin, the resistant biotype being seven and 33 times more resistant than the parent cultivar at the emergence and seedling stages, respectively. However, the doses recommended for efficient weed control resulted in some detrimental effects on emergence and growth in the field. Strategies for use of this resistance to control weeds in millet fields are proposed. [ABSTRACT FROM AUTHOR]

The River Fortun is situated in south-western Norway and is typical of the fiord landscape catchments with large areas above 1000m a.s.l,steep valley walls and an alluvial river plain at the valley floor. It was regulated for hydropower in 1963 and is Norway's 10th largest regulation scheme. The hydropower scheme has resulted in a large reduction of the frequency of large magnitude flood events. This paper describes the long-term geomorphological response of a gravel-bed riverchannel to this regulation. The study was initiated after complaintsfrom local farmers of an increase in flooding of farmland after regulation. Forty-seven cross-profiles of the river repeatedly measured in 1973, 1989 and 1995 along a 1600m reach have been used to quantify aggradation and degradation in the reach. The profiles show a reduction in channel size and capacity since 1973, with a net aggradation of12000m3. The upper part of the reach has been subject to the greatest amount of aggradation, with the river bed being raised by up to 1.5m, while the lower part has degraded, with lateral erosioncutting banks back by up to 30m. Aerial photographs from 1964 and 1984 show that former gravel-bars and flood channels have been subject to vegetation encroachment. The hydraulic model HEC-2 was used to compute the water level in 1973 and 1989. The water level has been raised by 0.6m at low flows in the upper parts of the studied reach. This corresponds to an increase in discharge of between 20-303/s. Overbank flow therefore occurs at lower discharges today than prior to regulation. [ABSTRACT FROM AUTHOR]

The Platte River in central Nebraska responded to water development by rapid channel narrowing and expansion of native riparian woodland.Woodland expanded most rapidly in the 1930s and 1950s; open channel and woodland area stabilized in the 1960s and have remained stable for most reaches into the mid-1990s, despite relatively low flows and infrequent peak flows in the past decade. Open channel area may have been maintained or increased under recent lower flows because of increased erodibility of the floodplain as it has aggraded, developed vertical banks and as its woodland vegetation has become older, sparser and less protective of banks. One section of the Platte River, near Grand Island, has disequilibrated in the past decade by undergoing a 10% loss of channel area. The reach occurs below an area where vegetation has been removed to increase open channel area for migrating whooping and sandhill cranes and other water birds. Vegetation clearing may have liberated excess sediment, locally aggraded the channel and stimulated tree and shrub recruitment. This management practice needs to be examined before it is used more widely in the Platte River. [ABSTRACT FROM AUTHOR]

In an effort to evaluate the selective control of the exotic weed Eurasian water milfoil (Myriophyllum spicatum L.) and to assess the recovery and restoration of the native submersed plant community, a 6-hariver and 4-ha cove plot were treated with the herbicide triclopyr at application rates of 2.5 and 1.75 mg/l, respectively, in the Pend Oreille River, WA, in August 1991. Water exchange half-lives within the plots were measured using rhodamine WT dye (river, t1/2=20 h; cove, t1/2=52 h), and triclopyr dissipation rates were also calculated (river, t1/2=19 h); cove, t1/2=53 h). Triclopyr concentrations were below the proposed potable water tolerance level (0.5 mg/l) within the river treatment plot by 3 days after treatment (<0.01 to 0.41 mg/l), and 675 m downstream of that plot by 1 day after treatment (<0.01 to 0.47 mg/l). Following the cove treatment, triclopyr residues ranged from 0.12 to 0.29 mg/l by 7 days after treatment, and from<0.01 to 0.06 mg/l as close as 150 m downstream from the plot. Eurasian water milfoil biomass was reduced by99% in the treated plots at 4 weeks post-treatment, remained low oneyear later (river treatment, 28% of pretreat levels; cove treatment 1% of pre-treat levels) and was still at acceptable levels of controlat two years post-treatment (river treatment, 47% of pre-treat levels; cove treatment, 24% of pre-treat levels). The four-week post-treatment efficacy results verified triclopyr concentration/exposure time relationships for controlling Eurasian water milfoil developed under laboratory conditions. Non-target native plant biomass increased 500-1000% by one year post-treatment, and remained significantly higher in the cove plot at two years after treatment. Native species diversity doubled following herbicide treatment, and the restoration of this robust community delayed the re-establishment and dominance of Eurasian water milfoil for three growing seasons. [ABSTRACT FROM AUTHOR]

In an effort to evaluate the selective control of the exotic weed Eurasian water milfoil (Myriophyllum spicatum L.) and to assess the recovery and restoration of the native submersed plant community, a 6-hariver and 4-ha cove plot were treated with the herbicide triclopyr at application rates of 2.5 and 1.75 mg/l, respectively, in the Pend Oreille River, WA, in August 1991. Water exchange half-lives within the plots were measured using rhodamine WT dye (river, t1/2=20 h; cove, t1/2=52 h), and triclopyr dissipation rates were also calculated (river, t1/2=19 h); cove, t1/2=53 h). Triclopyr concentrations were below the proposed potable water tolerance level (075 mg/l) within the river treatment plot by 3 days after treatment (<0.01 to 0.41 mg/l), and 675 m downstream of that plot by 1 day after treatment (<0.01 to 0.47 mg/l). Following the cove treatment, triclopyr residues ranged from 0.12 to 0.29 mg/l by 7 days after treatment, and from<0.01 to 0.06 mg/l as close as 150 m downstream from the plot. Eurasian water milfoil biomass was reduced by99% in the treated plots at 4 weeks post-treatment, remained low oneyear later (river treatment, 28% of pretreat levels; cove treatment 1% of pre-treat levels) and was still at acceptable levels of controlat two years post-treatment (river treatment, 47% of pre-treat levels; cove treatment, 24% of pre-treat levels). The four-week post-treatment efficacy results verified triclopyr concentration/exposure time relationships for controlling Eurasian water milfoil developed under laboratory conditions. Non-target native plant biomass increased 500-1000% by one year post-treatment, and remained significantly higher in the cove plot at two years after treatment. Native species diversity doubled following herbicide treatment, and the restoration of this robust community delayed the re-establishment and dominance of Eurasian water milfoil for three growing seasons. [ABSTRACT FROM AUTHOR]