A new study from Auckland University of Technology suggests that planting large native canopy trees at the beginning of forest restoration projects rather than waiting years could simplify efforts and reduce costs across Aotearoa New Zealand.
The findings, published in Ecological Solutions and Evidence, challenge the traditional staged approach to forest restoration, which typically prioritizes fast-growing “nurse” plants before introducing slower-growing canopy species.
Conventional restoration methods recommend planting early-successional nurse species first. These hardy plants provide shade and shelter, improving conditions for late-successional canopy trees that are introduced later.
But researchers from AUT’s Living Laboratory program monitored 1,840 canopy trees across three restoration sites in the Tāmaki Makaurau Auckland region Te Muri, Pūkorokoro, and Te Pourewa and found that several large native species can survive when planted alongside nurse plants from the start.
Over a three-year period, four of the six canopy species studied pūriri, rewarewa, kahikatea, and tōtara demonstrated high survival rates when planted early. However, rimu and taraire showed significantly lower survival, indicating that the approach may not suit every species or location.
“Usually, it is said that we should plant early successional trees first,” said lead researcher Dr. Sarah Bürli. “We were curious to examine what happens if you plant early and late successional trees at the same time.”
The results suggest that, for certain species, simultaneous planting could accelerate forest development and lower long-term project costs.
The study also identified planting layout as a key factor in seedling survival.
Researchers found that spacing nurse plants approximately two meters apart provided the optimal balance. Closer spacing created excessive shading and competition, while wider gaps left young canopy trees vulnerable to environmental stress such as wind and harsh sunlight.
Ground-level vegetation also played a crucial role. Both living plants and dead organic material around seedlings improved survival by retaining moisture and buffering temperature extremes. However, invasive kikuyu grass was found to be harmful, often smothering young trees.
“These results show that vegetation on the ground creates a more protective microenvironment for native plantings,” Bürli noted.
The research further revealed that soil conditions influenced survival differently across sites. In some areas, richer soils boosted survival rates, while in others, poorer soils were linked to better outcomes.
These contrasting patterns highlight the importance of tailoring restoration strategies to local environmental conditions rather than applying uniform planting methods.
Big canopy trees often referred to as late-successional species are essential for long-term forest health. They provide habitat, store carbon, and shape forest structure. If planted successfully at an earlier stage, they could help restored forests mature more quickly and deliver ecosystem benefits sooner.
The study’s findings offer practical guidance for community groups, landowners, and conservation organizations working to rebuild native forests across the motu. By combining early planting of select canopy species with thoughtful spacing and site-specific planning, restoration projects may achieve stronger results with fewer resources.