Native species flourish in Tairāwhiti pine plantations, ecologist reports

A research report found that species in the understory of pine plantations across Tairāwhiti were overwhelmingly native, with natives comprising 98.2 % of the understory.

Native plant species are thriving under the cover of pine in Tairāwhiti, a new study has revealed.

Researchers Meg Graeme, Mark Kimberley and Mike Bergin authored the report Native understory characteristics of pine plantation stands in Tairāwhiti, New Zealand for Tāne’s Tree Trust and the Ministry for Primary Industries.

Forty-five plots in 24 radiata pine plantations were studied across the region to investigate whether the native regenerating understory found within Tairāwhiti pine plantations was influenced by stand age, pine stem density, and distance to native seed source.

The research found that species in pine plantations’ understory were overwhelmingly native, with natives comprising 98.2 % of the understory.

The findings suggested that older and sparser pine canopy supported more diverse native growth in the understory and more carbon storage.

The research was welcomed by environmental advocacy group Mana Taiao Tairāwhiti.

“The research conducted over the past year revealed that pine plantations across erosion-prone hill country in Tairāwhiti are already regenerating with an understory that is 98% native species – dominated by kawakawa, māhoe, hangehange, and coprosmas," a statement from the group said.

The group noted that the research found that, without effective pest control and abundant native seed sources, large-canopy trees may fail to establish, leaving gaps filled by shrubs or invasive wilding pines.

“This research confirms what many locals have seen on the ground – pine plantations can act as ‘nurse crops’ that help bring back permanent native forests,” Mana Taiao Tairāwhiti spokeswoman Aimee Vickers said in a statement.

“But successful transition will require active management across tens of thousands of hectares that cannot be sustainably harvested.”

Vickers said an approach that involved pest control, access to diverse native seed sources and a thinning or modification of pine canopies would deliver “enormous benefits”.

“It’s not just about biodiversity – these forests are critical for soil stabilisation, climate resilience, carbon sequestration and reducing the devastating downstream impacts on our communities and ecosystems," she said.

“Mana Taiao Tairāwhiti is calling on central and local government, iwi, and forestry companies to work together to implement the report’s recommendations and ensure that Tairāwhiti’s vulnerable landscapes are transitioned into thriving, resilient native forests for future generations.”