Summary1. Population modelling and field measurements of births, growth and deaths were used to investigate the long-term change in abundance of Atriplex vesicaria (Chenopodiaceae), a long-lived, palatable, perennial shrub, under sheep grazing. Of particular interest was whether A. vesicaria is at risk of being eliminated throughout grazed paddocks when the recommended practice of continuous grazing at conservative stocking rates is employed. 2. Time-invariant matrix population models indicated that the A. vesicaria population was in decline over much of the study paddock, but the rate of decline was greatest nearer to the water point (population growth rate λ ≈ 0·8). Time-varying stochastic matrix models projected that the A. vesicaria population would become locally extinct at most sites up to approximately 2200 m from water, occurring first closer to water (within 12-29 years). The population was stable (i.e. λ ≥ 1) at sites greater than 2200 m from water over the projection period of 100 years. 3. Decreases in adult survival and recruitment made the largest contributions to reductions in the population growth rate. However, there were spatial patterns centred on the water point in the degree to which particular demographic processes contributed to these reductions, because of a grazing gradient and the differential sensitivity of demographic processes to grazing. Thus decreases in recruitment contributed to reductions in the population growth rate at greater distances. Such responses, together with the sensitivity of the population growth rate to these processes, determined the spatial pattern in population growth. 4. The results suggest that piospheres (i.e. the zone of impact) continue to expand over many years under set-stocking so that the area around the water point that is devoid of A. vesicaria becomes larger. The process of expansion appears to first involve the inhibition of recruitment, followed by eventual mortality of established shrubs. 5. The large contribution of adult survival to the population growth rate in A. vesicaria suggests that minimizing the mortality of established adults should be a priority for management. This is likely to involve resting from grazing at critical times such as during extended dry periods. This may also permit increased levels of recruitment during subsequent moister periods.

Beef cattle grazing is the dominant land use in the extensive tropical and sub-tropical rangelands of northern Australia. Despite the considerable knowledge on land and herd management gained from both research and practical experience, the adoption of improved management is limited by an inability to predict how changes in practices and combinations of practices will affect cattle production, economic returns and resource condition. To address these issues, past Australian and international research relating to four management factors that affect productivity and resource condition was reviewed in order to identify key management principles. The four management factors considered were stocking rates, pasture resting, prescribed fire, and fencing and water point development for managing grazing distribution. Four management principles for sound grazing management in northern Australia were formulated as follows: (1) manage stocking rates to meet goals for livestock production and land condition; (2) rest pastures to maintain them in good condition or to restore them from poor condition to increase pasture productivity; (3) devise and apply fire regimes that enhance the condition of grazing land and livestock productivity while minimising undesirable impacts; and (4) use fencing and water points to manipulate grazing distribution. Each principle is supported by several more specific guidelines. These principles and guidelines, and the supporting research on which they are based, are presented.

Achieving more uniform grazing at landscape and paddock scales is seen as an important management objective by pastoralists in northern Australia, but it is difficult to attain in practice. This paper presents a brief review of some key factors to be considered in attempts to modify grazing distribution in extensive rangelands by drawing on the preliminary results of a project that is investigating several options for achieving more uniform grazing. Subdividing the landscape into smaller paddocks and, to a lesser extent, installing additional water points in large paddocks are effective in distributing grazing more widely across the landscape. However, these approaches are less effective in achieving uniform grazing within paddocks, and areas of concentrated use still occur even in small paddocks. To achieve spatial grazing objectives, it is necessary to use management tools that operate at the appropriate scale. Attaining more even use within paddocks should therefore be viewed as a separate management objective, requiring different techniques, to obtaining more effective use of the landscape as a whole. Integrating the use of several spatial management tools that act at different scales is likely to be most effective in improving grazing distribution. Our findings also highlight the importance of understanding paddocks in terms of the spatial arrangement of forage resources and their acceptability and quality in relation to water points and other landscape features. Differences between individual cattle in the way they use the landscape are important in producing more uniform use in larger paddocks and may also offer other opportunities for improving the use of landscape resources overall. Finally, the implications of more uniform use for livestock production and other land use values should be considered, with the protection of biodiversity values potentially requiring special management arrangements where more even use is achieved.