Leigh P. Hunt

Factors affecting the management of cattle grazing distribution in northern Australia: preliminary observations on the effect of paddock size and water points

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.

Principles and guidelines for managing cattle grazing in the grazing lands of northern Australia: stocking rates, pasture resting, prescribed fire, paddock size and water points - a review

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.

Measure it to better manage it: a biodiversity monitoring framework for the Australian rangelands

The need for broad-scale, long-term biodiversity monitoring to support evidence-based policy and management in the Australian rangelands is clear and pressing but, despite protracted discussion of this need, there has been little progress towards implementation. To prompt real progress, we propose a framework of spatially hierarchical and complementary components that together use a combination of direct and indirect measures of biodiversity and drivers: • Targeted monitoring; involving localised field-based monitoring of target species, addressing specific management questions. • Surveillance monitoring; involving broad-scale, field-based sampling of multi-taxa and a set of habitat and condition attributes. • Landscape-scale monitoring; providing regional to national-scale intelligence on habitat quality and trends in threats to or drivers of biodiversity, with data obtained using systematic ground-based and remote methods. The framework aims to provide information on the response of biodiversity to rangeland management that is relevant to regional, state and national jurisdictions. We believe the characteristics of the proposed framework address many of the pitfalls that often stall biodiversity monitoring in Australia. These characteristics include: clarification of the desired outcomes and management requirements; a strong collaborative partnership that oversees the administration of the framework and ensures long-term commitment; a conceptual model that guides clear and relevant question-setting; careful design and analysis aimed at addressing the set questions; timely and relevant communication and reporting; and, regular data analysis and review, providing an adaptive mechanism for the framework to evolve and remain relevant. The proposed framework can be incrementally implemented at a moderate cost, relative to current total expenditure in natural resource management in the Australian rangelands.

Sustainable grazing management for temporal and spatial variability in north Australian rangelands – a synthesis of the latest evidence and recommendations

Rainfall variability is a major challenge to sustainable grazing management in northern Australia, with management often complicated further by large, spatially-heterogeneous paddocks. This paper presents the latest grazing research and associated bio-economic modelling from northern Australia and assesses the extent to which current recommendations to manage for these issues are supported. Overall, stocking around the safe long-term carrying capacity will maintain land condition and maximise long-term profitability. However, stocking rates should be varied in a risk-averse manner as pasture availability varies between years. Periodic wet-season spelling is also essential to maintain pasture condition and allow recovery of overgrazed areas. Uneven grazing distributions can be partially managed through fencing, providing additional water-points and in some cases patch-burning, although the economics of infrastructure development are extremely context-dependent. Overall, complex multi-paddock grazing systems do not appear justified in northern Australia. Provided the key management principles outlined above are applied in an active, adaptive manner, acceptable economic and environmental outcomes will be achieved irrespective of the grazing system applied.

Resting pastures to improve land condition in northern Australia: guidelines based on the literature and simulation modelling

Pasture rest is a possible strategy for improving land condition in the extensive grazing lands of northern Australia. If pastures currently in poor condition could be improved, then overall animal productivity and the sustainability of grazing could be increased. The scientific literature is examined to assess the strength of the experimental information to support and guide the use of pasture rest, and simulation modelling is undertaken to extend this information to a broader range of resting practices, growing conditions and initial pasture condition. From this, guidelines are developed that can be applied in the management of northern Australia’s grazing lands and also serve as hypotheses for further field experiments. The literature on pasture rest is diverse but there is a paucity of data from much of northern Australia as most experiments have been conducted in southern and central parts of Queensland. Despite this, the limited experimental information and the results from modelling were used to formulate the following guidelines. Rest during the growing season gives the most rapid improvement in the proportion of perennial grasses in pastures; rest during the dormant winter period is ineffective in increasing perennial grasses in a pasture but may have other benefits. Appropriate stocking rates are essential to gain the greatest benefit from rest: if stocking rates are too high, then pasture rest will not lead to improvement; if stocking rates are low, pastures will tend to improve without rest. The lower the initial percentage of perennial grasses, the more frequent the rests should be to give a major improvement within a reasonable management timeframe. Conditions during the growing season also have an impact on responses with the greatest improvement likely to be in years of good growing conditions. The duration and frequency of rest periods can be combined into a single value expressed as the proportion of time during which resting occurs; when this is done the modelling suggests the greater the proportion of time that a pasture is rested, the greater is the improvement but this needs to be tested experimentally. These guidelines should assist land managers to use pasture resting but the challenge remains to integrate pasture rest with other pasture and animal management practices at the whole-property scale.

EcoFire: regional-scale prescribed burning increases the annual carrying capacity of livestock on pastoral properties by reducing pasture loss from wildfire

Prescribed burning is an important management tool in the extensive pastoral lands in northern Australia. It can be used to influence grazing patterns, increase the nutritive value of pastures, reduce the density of woody shrubs and reduce the risk of damaging wildfires. The consequences of regional-scale prescribed burning on pasture availability and annual carrying capacities of pastoral properties in northern Australia were examined using EcoFire, a fire management program in the Kimberley Region of north-west Australia, as an example. Theoretical long-term carrying capacities of land systems, and fire scar imagery from years before (2004–06) and during EcoFire (2007–11) were used to model the impact of the program on the seasonality and extent of fire-induced losses in annual carrying capacity, and the likelihood of properties experiencing catastrophic losses in a given year. Over the 5 years that EcoFire has been running, it has resulted in a progressive reduction in the loss of annual carrying capacity caused by the burning of pasture, and shifted the season that annual carrying capacity is lost to fire from predominantly the late to the early dry season. Most notably, the established program has reduced the probability of experiencing catastrophic loss (defined here as >50% of annual carrying capacity removed due to fire) from 18 incidences to three incidences within a 3-year period. These outcomes have the potential to deliver economic benefits to pastoralists via increased annual carrying capacity and by improvements in pasture condition, provided stocking rates and pasture utilisation are managed carefully.

Aboveground and belowground carbon dynamics in response to fire regimes in the grazed rangelands of northern Australia: initial results from field studies and modelling

The world’s rangelands are often seen as offering considerable potential as a carbon (C) sink, which could contribute to the management of atmospheric C levels, but there are often few data available to assess this potential or to inform the type of management regimes that would be necessary. This paper reports on a review of the literature, a field study and modelling of C stocks under a selection of experimental fire regimes in two plant communities in Australia’s northern rangelands. The field study on an open eucalypt savanna woodland and a savanna grassland-open shrubland suggested that fire regime had no effect or an inconsistent effect on aboveground C stocks. However, modelling using the Century model for the open woodland site showed that increasing fire frequency was associated with reduced aboveground and soil C stocks. Thus, while infrequent fires allowed C stocks to increase (10-yearly fire) or remain stable (6-yearly fire) over a modelled 58-year period, a regime of more frequent fires (4- and 2-yearly fires) reduced C stocks over time. Simulation of C dynamics over 93 years of pastoral settlement suggested that total C stocks had increased by 9.5 t ha–1, largely due to an increase in C in woody vegetation following a reduction in fire frequency associated with pastoral settlement. Frequent burning, as recommended to maintain low woody density and promote pasture production for grazing, will, therefore, reduce aboveground and to a lesser extent soil C stocks where there has been a history of infrequent fire. The opportunities for pastoralists to increase C stocks will depend on the frequency of fire and vegetation type, especially its woodiness or potential woodiness. Reducing fire frequency in woody rangelands will increase C stocks but may have adverse effects on pasture and livestock production. Reducing grazing pressure or destocking might also increase C stocks but may be relevant only when a property is overstocked or where relatively unproductive land could be taken out of livestock production. Any C gains from altering fire and grazing management are likely to be modest.

Sampling requirements for predicting cattle diet quality using faecal near-infrared reflectance spectroscopy (F.NIRS) in heterogeneous tropical rangeland pastures

Faecal near-infrared reflectance spectroscopy (F.NIRS) provides predictive information on cattle diets and nutritional levels, useful for livestock management or for research purposes. Potential errors exist throughout the entire F.NIRS process, including the collection method. The accepted collection method involves aggregating equal amounts of faecal material from 5 to 15 animals, mixing and removing a single sample for analysis. The adequacy of this method was tested by collecting and analysing up to 70 samples from individual cattle in different paddocks. Two methods were used to determine sample size based on observed variability in dietary attributes. Variability of dietary non-grass material and crude protein content increased with paddock size, so required sample size also increased. For dietary F.NIRS predictions to be used for research, our results suggest from 20 to 51 samples are needed in small to large paddocks to accurately predict the proportion of dietary non-grass material, from 12 to 50 samples for crude protein content and from 6 to 34 samples for dry matter digestibility. Composite samples from 15 cattle provided representative means in less than 50% of the situations investigated using biologically significant precision levels, but would be adequate for management of animal nutrition. Analysis of individual samples provided additional measures of range and variability which were also informative.