Abstract

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.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 17years 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.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.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 soil-mediated effects of ungulates on seedling biomass were of abiotic origin, but were mediated by the biotic soil component, that is, through effects on AMF.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.

Keywords

herbivory; arbuscular mycorrhizal fungi; feral goats; soil organisms; biological invasions; browsing mammals; cluster roots; New Zealand forests; above-ground-below-ground interactions; deer

Published in

Journal of Ecology
2014, Volume: 102, number: 3, pages: 622-631
Publisher: WILEY-BLACKWELL

SLU Authors

• Kardol, Paul

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

• Wardle, David

  • Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
    

Associated SLU-program

SLU Plant Protection Network


Sustainable Development Goals

SDG15 Protect, restore and promote sustainable use of terrestrial ecosystems, sustainably manage forests, combat desertification, and halt and reverse land degradation and halt biodiversity loss


UKÄ Subject classification

Forest Science


Publication identifier

DOI: https://doi.org/10.1111/1365-2745.12234

Permanent link to this page (URI)

https://res.slu.se/id/publ/60869