Soil-mediated indirect impacts of an invasive predator on plant growth

Wardle, David A.; Bellingham, Peter J.; Fukami, Tadashi; Bonner, Karen I.

doi:10.1098/rsbl.2012.0201

Cited by 17 publications

(15 citation statements)

References 20 publications

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“…; Wardle et al . ). We used a paired 2 × 2 factorial design, in which for each site, we grew seedlings in sterilized soils from either the exclosure or the paired control plot, and inoculated each sterilized soil with living soil inoculum from either the exclosure plot or the paired control plot.…”

Section: Methodsmentioning

confidence: 97%

Soil‐mediated effects of invasive ungulates on native tree seedlings

et al. 2014

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Summary1. Invasive browsing ungulates can have strong impacts on the structure and composition of forest ecosystems, particularly where ungulates are not native ecosystem components as in New Zealand. Ungulate impacts on plant communities have been considered mostly from an above-ground perspective. However, understanding below-ground effects of these invasive herbivores is critical as they may drive feedbacks to above-ground ecosystem components. 2. We measured growth responses of seedlings of five common tree species in a greenhouse experiment in soils collected from 26 plots fenced to exclude invasive ungulates for at least 17 years and from paired, unfenced control plots. We then further investigated soil-mediated effects of ungulates on one tree species, Melicytus ramiflorus, by partitioning these effects into soil abiotic and biotic components, as well as measuring arbuscular mycorrhizal fungal (AMF) root infection. 3. Biomass of seedlings of all five species was greater in soils from within exclosures, although this was only significant for two species. These soil-mediated effects were partially driven by changes in physical and chemical soil properties; soil bulk densities were lower inside exclosures than in controls. 4. Effects of invasive ungulates on seedling biomass of M. ramiflorus were positively related to effects on per cent AMF root infection. The biomass of M. ramiflorus seedlings was positively related to the AMF infection of its roots, which in turn was related to greater organic matter content and lower bulk density of soils from within exclosures. Results for M. ramiflorus indicated that soilmediated effects of ungulates on seedling biomass were of abiotic origin, but were mediated by the biotic soil component, that is, through effects on AMF. 5. Synthesis. Invasive herbivores may potentially impact on plant performance and community structure not only directly but also indirectly through influencing soil abiotic and biotic properties. Our results show that shifts in plant-soil interactions and feedbacks represent important but understudied pathways by which invasive ungulates can have wide-ranging impacts on forest ecosystems. Future studies should consider the importance of soil-mediated effects of invasive ungulates relative to direct effects of herbivory.

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Section: Methodsmentioning

confidence: 97%

Soil‐mediated effects of invasive ungulates on native tree seedlings

et al. 2014

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“…Nevertheless, such cascading effects involving both trophic and non‐trophic interactions remain relatively poorly studied particularly in predator–detritivore–plant systems (but see Wardle et al . ).…”

Section: Introductionmentioning

confidence: 97%

Predatory beetles facilitate plant growth by driving earthworms to lower soil layers

Zhao

Griffin

et al. 2013

Journal of Animal Ecology

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Summary1. Theory suggests that predators of soil-improving, plant-facilitating detritivores (e.g. earthworms) should suppress plant growth via a negative tri-trophic cascade, but the empirical evidence is still largely lacking. 2. We tested this prediction in an alpine meadow on the Tibetan Plateau by manipulating predatory beetles (presence/absence) and quantifying (i) direct effects on the density and behaviour of earthworms; and (ii) indirect effects on soil properties and above-ground plant biomass. 3. In the absence of predators, earthworms improved soil properties, but did not significantly affect plant biomass. Surprisingly, the presence of predators strengthened the positive effect of earthworms on soil properties leading to the emergence of a positive indirect effect of predators on plant biomass. 4. We attribute this counterintuitive result to: (i) the inability of predators to suppress overall earthworm density; and (ii) the predator-induced earthworm habitat shift from the upper to lower soil layer that enhanced their soil-modifying, plant-facilitating, effects. 5. Our results reveal that plant-level consequences of predators as transmitted through detritivores can hinge on behaviour-mediated indirect interactions that have the potential to overturn predictions based solely on trophic interactions. 6. This work calls for a closer examination of the effects of predators in detritus food webs and the development of spatially explicit theory capable of predicting the occurrence and consequences of predator-induced detritivore behavioural shifts.

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“…In particular, it is common to either: (1) fill each container with soil from one experimental unit (e.g. Callaway et al, 2004;Hood et al, 2004;Kardol et al, 2006;Wardle et al, 2012), or (2) fill each container with a mixture of soils from multiple experimental units (i.e. all sites within a region, all plots that received the same treatment) (e.g.…”

Section: Introductionmentioning

confidence: 99%