Impacts of shrub encroachment on ecosystem structure and functioning: towards a global synthesis

By D. Eldridge, M. Bowker, Fernando T. Maestre, E. Roger, J. Reynolds, W. Whitford. Ecology Letters, 2011

1,186 citations recorded by the source corpus.

Encroachment of woody plants into grasslands has generated considerable interest among ecologists. Syntheses of encroachment effects on ecosystem processes have been limited in extent and confined largely to pastoral land uses or particular geographical regions. We used univariate analyses, meta-analysis and structural equation modeling to test the propositions that 1) shrub encroachment does not necessarily lead to declines in ecosystem functions, and 2) shrub traits influence the functional outcome of encroachment. Analyses of 43 ecosystem attributes from 244 case studies worldwide showed that some attributes consistently increased with encroachment (e.g. soil C, N), and others declined (e.g. grass cover, pH), but most exhibited variable responses. Traits of shrubs were associated with significant, though weak, structural and functional outcomes of encroachment. Our review revealed that encroachment had mixed effects on ecosystem structure and functioning at global scales, and that shrub traits influence the functional outcome of encroachment. Thus, a simple designation of encroachment as a process leading to functionally, structurally or contextually degraded ecosystems is not supported by a critical analysis of existing literature. Our results highlight that the commonly established link between shrub encroachment and degradation is not universal.

Subfields: Global and Planetary Change, Management, Monitoring, Policy and Law, Nature and Landscape Conservation

View Paper: https://www.semanticscholar.org/paper/005fb40bd80de708379a4b518a0898e20c4e01bb

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In Global and Planetary Change

In Management, Monitoring, Policy and Law

Fernando T. Maestre

In Nature and Landscape Conservation

Citations in the corpus

Assessing Land Degradation and Desertification Using Vegetation Index Data: Current Frameworks and Future Directions (2014, neutral): “encroachment is not universally accepted as a component of land degradation [122].”
Are shrubs really a sign of declining ecosystem function? Disentangling the myths and truths of woody encroachment in Australia (2014, background): “…body of literature on shrub encroachment currently in the public arena (see, for example, Noble 1997; Van Auken 2000; House et al. 2003; Archer 2009; Eldridge et al. 2011), nor the body of work on tree regrowth and clearing (e.g. Fensham2008;Witt et al. 2009, 2011; Silcock et al. 2013;Witt 2013).”
Positive effects of shrubs on plant species diversity do not change along a gradient in grazing pressure in an arid shrubland (2012, background): “Der Boden unter beiden Ammenpflanzen besaß signifikant höhere Indizes in Bezug auf en Nährstoffkreislauf und die Durchlässigkeit und enthielt mehr C und N als der Boden in offenen Bereichen.”
Shrub encroachment and vertebrate diversity: A global meta‐analysis (2018, background): “Mammals and herpetofauna may exhibit less variation in use of cover and foraging modes than birds, for example, leading to increased sensitivity to shrub encroachment (Eldridge et al., 2011; Slagsvold, 2001).”
Uncovering multiscale effects of aridity and biotic interactions on the functional structure of Mediterranean shrublands (2013, background): “Our knowledge on the mechanisms driving the functional structure of arid and semi-arid ecosystems remains incomplete (Maestre et al. 2009a; Eldridge et al. 2011; Freschet et al. 2011; Frenette-Dussault et al. 2012), despite their ecological importance, extent and the ecosystem services that they pro”