Opportunistic Management for Rangelands Not at Equilibrium

Westoby, Mark; Walker, Brian; Noy‐Meir, Imanuel

doi:10.2307/3899492

Cited by 1,517 publications

(1,206 citation statements)

References 41 publications

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“…According to rangeland ecology literature (e.g., Westoby, 1989 andBriske et al, 2003), savannas can be viewed in light of range succession or state-and-transition models. In range succession models, savannas are a point in a continuous spectrum whose extremes are grassland and forest.…”

Section: What Is Special About the Savanna Environment That Allows Trmentioning

confidence: 99%

Tree–grass co-existence in savanna: Interactions of rain and fire

Accatino

Michele

Vezzoli

et al. 2010

Journal of Theoretical Biology

116

105

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The mechanisms permitting the co-existence of tree and grass in savannas have been a source of contention for many years. The two main classes of explanations involve either competition for resources, or differential sensitivity to disturbances. Published models focus principally on one or the other of these mechanisms. Here we introduce a simple ecohydrologic model of savanna vegetation involving both competition for water, and differential sensitivity of trees and grasses to fire disturbances. We show how the coexistence of trees and grasses in savannas can be simultaneously controlled by rainfall and fire, and how the relative importance of the two factors distinguishes between dry and moist savannas. The stability map allows to predict the changes in vegetation structure along gradients of rainfall and fire disturbances realistically, and to clarify the distinction between climate-and disturbance-dependent ecosystems.

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Section: What Is Special About the Savanna Environment That Allows Trmentioning

confidence: 99%

Tree–grass co-existence in savanna: Interactions of rain and fire

Accatino

Michele

Vezzoli

et al. 2010

Journal of Theoretical Biology

116

105

View full text Add to dashboard Cite

show abstract

“…This severely reduces animal production, while herd mortality and the expense of drought feeding can affect enterprise profitability for years (Hinton, 1993). Overgrazing in droughts can also lead to major, sometimes irreversible, declines in land condition (Westoby et al, 1989). Aside from its long-term impacts on productivity, the associated declines in ecosystem services such as reduced water quality are a major societal cost.…”

Section: Introductionmentioning

confidence: 99%

Sustainable management for rangelands in a variable climate: evidence and insights from northern Australia

O’Reagain¹,

Scanlan²

2013

Animal

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Inter-annual rainfall variability is a major challenge to sustainable and productive grazing management on rangelands. In Australia, rainfall variability is particularly pronounced and failure to manage appropriately leads to major economic loss and environmental degradation. Recommended strategies to manage sustainably include stocking at long-term carrying capacity (LTCC) or varying stock numbers with forage availability. These strategies are conceptually simple but difficult to implement, given the scale and spatial heterogeneity of grazing properties and the uncertainty of the climate. This paper presents learnings and insights from northern Australia gained from research and modelling on managing for rainfall variability. A method to objectively estimate LTCC in large, heterogeneous paddocks is discussed, and guidelines and tools to tactically adjust stocking rates are presented. The possible use of seasonal climate forecasts (SCF) in management is also considered. Results from a 13-year grazing trial in Queensland show that constant stocking at LTCC was far more profitable and largely maintained land condition compared with heavy stocking (HSR). Variable stocking (VAR) with or without the use of SCF was marginally more profitable, but income variability was greater and land condition poorer than constant stocking at LTCC. Two commercial scale trials in the Northern Territory with breeder cows highlighted the practical difficulties of variable stocking and provided evidence that heavier pasture utilisation rates depress reproductive performance. Simulation modelling across a range of regions in northern Australia also showed a decline in resource condition and profitability under heavy stocking rates. Modelling further suggested that the relative value of variable v. constant stocking depends on stocking rate and land condition. Importantly, variable stocking may possibly allow slightly higher stocking rates without pasture degradation. Enterprise-level simulations run for breeder herds nevertheless show that poor economic performance can occur under constant stocking and even under variable stocking in some circumstances. Modelling and research results both suggest that a form of constrained flexible stocking should be applied to manage for climate variability. Active adaptive management and research will be required as future climate changes make managing for rainfall variability increasingly challenging.Keywords: grazing strategies, profitability, land condition, climate forecasts, simulation models ImplicationsEvidence from northern Australia suggests that managers should apply a form of constrained flexible stocking with upper limits to stocking rate of about 20% to 40% above long-term carrying capacity. Stocking rates should be tactically adjusted on the basis of forage availability, and where appropriate, informed by seasonal climate forecasts. Even in the best years, annual stocking rate increases should be limited to 10% to 20% in order to avoid overstocking in the event of poor subsequent seasons....

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“…Succession has traditionally been thought to be a relatively linear process, but growing evidence indicates that persistent alternative vegetation or ecosystem states separated by critical thresholds may occur in many different types of ecosystems , including Mediterranean vegetation types around the world (Arianoutsou-Faraggitaki and Margaris 1982;Holmgren 2002;Kefi et al 2007;Laycock 1991; Van de Wouw et al 2011;Westoby et al 1989).…”

Section: Introductionmentioning

confidence: 99%

Pathways for resilience in Mediterranean cork oak land use systems

Acácio¹,

Holmgren²

2012

Annals of Forest Science

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Context Loss of woodlands and degradation of vegetation and soil have been described for all Mediterranean-type ecosystems worldwide. In the Western Iberian Peninsula, overexploitation of evergreen cork oak land use systems has led to soil erosion, failures in oak recruitment, and loss of forests. Degraded and dry sites are quickly colonised by pioneer heathland rockrose (Cistus spp.) shrubs forming highly persistent patches. Aims Although traditionally shrublands have been considered as a transient successional state, we present evidence that they can represent persistent alternative states to former cork oak forests. Review trends and conclusions We first describe how Mediterranean vegetation evolved in the Iberian Peninsula and the role of fire and long-term human management as main disturbances. We then discuss alternative pathways through state-and-transition models indicating the ecological and land use variables that halt cork oak regeneration and recruitment and drive vegetation transitions towards persistent shrublands. Unless concerted management actions and restoration programmes are undertaken, the cork oak land use systems will not be sustainable.

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Opportunistic Management for Rangelands Not at Equilibrium

Cited by 1,517 publications

References 41 publications

Tree–grass co-existence in savanna: Interactions of rain and fire

Tree–grass co-existence in savanna: Interactions of rain and fire

Sustainable management for rangelands in a variable climate: evidence and insights from northern Australia

Pathways for resilience in Mediterranean cork oak land use systems

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