Janice Lord and field assistant Hilary at Ben Lomond Scenic Reserve.
Janice Lord and field assistant Hilary at Ben Lomond Scenic Reserve.

Researchers are developing a customised seed-mix that can be planted to grow large-scale forests of native vegetation as easily as farmers sow pasture.

The study could have major implications for the Government’s Billion Trees initiative, while the work is also important for long-term ecological restoration projects that need to be done at landscape scales.

Agricultural techniques will be used to plant the seed-mix by the hectare – drastically reducing costs and increasing the success rate of native reforestation in Aotearoa New Zealand.

Known as Ngā Kākano Whakahau, the project is a collaboration between QEII National Trust and the University of Otago, with support from the BioHeritage Challenge.

University of Otago botanist Janice Lord is leading the project and says it’s as much about below-ground rehabilitation as it is about above-ground revegetation. As well as planting the seeds, the scientists are working on techniques to re-introduce the native mycorrhizal fungi upon which many native species depend.

“Most native trees and shrubs need their roots to be colonised by mycorrhizal fungi in order for them to obtain enough phosphorus and nitrogen in our naturally nutrient-limited soils.

“In pastoral areas where the native forest has been removed, or in areas invaded by wilding conifers, most native mycorrhizal fungi would have disappeared. We’ve been experimentally comparing methods for introducing isolated fungal spores to seeds.

“The first phase of the project involved isolating mycorrhizal fungi associated with beech and mānuka on Otago’s Mahu Whenua high country station. Spore concentrates made from these fungi were then used to treat beech and mānuka seeds in glasshouse and field trials to enable mycorrhizal connections to re-establish and assist with seedling growth. The team also isolated mycorrhizal fungi assisting seedling establishment following enviro-blanket seeding.

In autumn next year, the team plan to carry out native reseeding field trials at sites in Otago and Canterbury that will be the largest of their kind in Aotearoa.

“These sites will serve as flagships and experimental resources for future restoration research.”

Janice says Ngā Kākano Whakahau is especially focused on finding practical methods that can be used by community groups.

“It has sparked a surge of interest in native mycorrhizae among Otago and Southland community-based restoration groups and native plant growers. With a heavy beech seeding year approaching, the Ngā Kākano Whakahau team is working with these groups to maximise seed and fungal spore collection for next year’s field trials.”

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