Fungal inoculation in native plantings

Location: Mackenzie Basin, Canterbury, Aotearoa New Zealand
Project type: Field restoration experiment
Delivery/lead organisations: University-based researchers (with landholder cooperation)
Date/period: Late 2000s – early 2010s
Scale: Site
Primary system or theme: Soil biota (arbuscular mycorrhizal fungi), native woody plant establishment

Context

Why this site matters
The Mackenzie Basin is a cold, semi-arid inland landscape with low soil organic matter and a long history of pastoral land use. These conditions create nutrient-limited soils that differ substantially from intact forest ecosystems, influencing native woody plant establishment.1

Challenge or constraint

What wasn’t working/what needed to change
Native woody species have often shown poor survival and growth when planted into degraded Mackenzie Basin soils using standard restoration methods. Evidence indicates that mycorrhizal benefits are highly dependent on soil phosphorus availability and plant–fungal compatibility, rather than simple presence or absence of mycorrhizal fungi.2

Intervention

What was done
A field experiment tested whether arbuscular mycorrhizal fungal (AMF) inoculation could improve the establishment of Podocarpus cunninghamii (mountain tōtara) in degraded high-country soils.3

Key components

  • Pre-planting inoculation of nursery-raised seedlings
  • Comparison of inoculum sources: indigenous forest-derived AMF, grassland-derived AMF, and commercial AMF products
  • Non-inoculated control seedlings

Implementation notes

Design and delivery considerations

  • Inoculation effects were assessed under low-fertility field conditions
  • Soil phosphorus history influenced plant responses to AMF2
  • Root colonisation was confirmed to distinguish functional effects from inoculation failure3
  • The intervention operated as a supporting mechanism rather than addressing broader site constraints (e.g. climate, browsing, competition)

Outcomes

Observed or reported outcomes

  • Seedlings inoculated with indigenous forest-derived AMF showed higher survival and growth than those receiving grassland-derived or commercial inocula3
  • Commercial AMF inoculation resulted in lower survival compared with forest-derived inoculum3
  • Successful root colonisation confirmed treatment effectiveness3

What is plausible but unmeasured

  • Improved long-term nutrient uptake efficiency beyond the early establishment phase
  • Gradual convergence with background soil fungal communities over time

Evidence and limits

What the evidence supports
The study demonstrates that early establishment of native woody species can be constrained by the availability of compatible mycorrhizal fungi, and that locally derived inoculum can outperform generic commercial products in degraded high-country soils.3

Key limitations or uncertainties

  • Effects were measured over early establishment only; long-term persistence is uncertain
  • Outcomes are highly context-dependent, varying with soil fertility and plant species2
  • Environmental stressors (e.g. drought, browsing, competition) can override mycorrhizal effects4
  • Benefits may diminish as background fungal communities recolonise roots5,6

Relevance to design practice

  • Mycorrhizal interventions should prioritise locally sourced or reference-ecosystem inoculum where soil biotic mismatch is suspected
  • Avoid assuming commercial inocula are beneficial; inappropriate fungi can reduce survival3
  • AMF inoculation is a targeted, context-specific tool that should complement, not replace, broader soil, moisture, and disturbance management

References

  1. Crush, J. R. (1975). Occurrence of endomycorrhizas in soils of the Mackenzie Basin, Canterbury, New Zealand. New Zealand Journal of Agricultural Research, 18, 361–364.
  2. Crush, J. R. (1976). Endomycorrhizas and legume growth in some soils of the Mackenzie Basin, Canterbury, New Zealand. New Zealand Journal of Agricultural Research, 19, 473–476.
  3. Williams, A., Norton, D. A., & Ridgway, H. J. (2012). Different arbuscular mycorrhizal inoculants affect the growth and survival of Podocarpus cunninghamii restoration plantings in the Mackenzie Basin, New Zealand. New Zealand Journal of Botany, 50, 473–479.
  4. Davis, M. R. (2011). Conifer establishment in South Island high country: Influence of mycorrhizal inoculation, competition removal, fertiliser application, and animal exclusion during seedling establishment. New Zealand Journal of Forestry Science, 41, 1–12.
  5. Maltz, M. R., & Treseder, K. K. (2015). Sources of inocula influence mycorrhizal colonization of plants in restoration projects: A meta-analysis. Restoration Ecology, 23, 625–634.
  6. Neuenkamp, L., Prober, S. M., Price, J. N., Zobel, M., & Standish, R. J. (2019). Benefits of mycorrhizal inoculation to ecological restoration depend on plant functional type, restoration context and time. Fungal Ecology, 40, 140–149.