Abstract
The role of ectomycorrhizae has often been overlooked during the ecological restoration of southern beech (Nothofagaceae) forests. This interaction may prove to be vital when trying to encourage the regeneration of beech forests into grasslands. A previous glasshouse study using soil bioassays showed that distance limited ectomycorrhizal colonisation of beech seedlings with increasing distance from forest edge. However, the additional potential role of spore dispersal in the field remains untested. Isolated trees in grasslands may also accumulate a lower diversity of ectomycorrhizal fungi, which may be less effective than forest fungal communities for promoting tree establishment. This thesis aimed to assess the effect of distance from the forest edge on colonisation of seedlings and characterise how the community of ectomycorrhizal fungi changes at different distances from the forest and when different ectomycorrhizal hosts are present. Seeds were sown at varying distances up to 100 m from the beech forest edge in the Motatapu Valley, Otago. After eight months of growth, seedlings were harvested and their roots were examined to assess levels of ectomycorrhizal colonisation. In line with previous work a threshold was observed at 12 m from the forest edge, with a significant decrease in the levels of ectomycorrhizal root colonisation, however, there was still low levels of colonisation all the way to 100 m. In order to assess the impact of distance and how a dual mycorrhizal host like mānuka (Leptospermum scoparium) may impact ectomycorrhizal community composition, an existing metabarcoding dataset collected in the same area was analysed. It was found that host type and distance acted independently in altering the ectomycorrhizal community composition. Beech trees on forest edges where mānuka was present had more early successional fungal taxa whereas beech trees on the edge of forests without mānuka were more dominated by late successional fungal communities. Different sampling methods were also compared, with hyphal ingrowth bags tending to detect more early successional species, whereas root sampling recovered more late successional species. This difference in sampling supports the popular idea that multiple sampling methods are needed at the temporal and spatial level to ensure that the whole community is sampled. The impact of host type also supports the suggestion that mānuka can act as a nursery for beech seedlings, providing the necessary ectomycorrhizal fungi and protecting the seedlings from abiotic and biotic stressors. Such successional approaches could prove effective for promoting the natural expansion of beech forests where desirable.