An innovative solution to bush regeneration and resilience is being developed for a small stand of mature kahikatea trees in Turua.
The aim of the project, a uniquely-designed irrigation system, is to keep the stand healthy, giving its trees the best possible chance of resisting dieback disease.
The project is the brainchild of Turua Domain caretaker and committee member Jim Sutherland.
The aim is to use stormwater collected from the neighbouring Barnados Early Learning Centre to maintain the water table in the domain’s fenced-off section of bush at the back of the property, adjacent to Piako and Oparia Rds. The two-acre stand has around 72 mature kahikatea trees which are roughly 400 years old, along with at least 100 young saplings.
Two 4000-litre water tanks have already been installed behind the Barnados building.
“They were going to put in an underground tank… That was going to cost them $15,000,” Jim said.
“I’d priced our irrigation scheme up to about $15,000 as well. So they said, ‘well, that’s pretty easy. We’ll just do the irrigation scheme then if the council agrees’.
“Barnardos have been really good with us, and we’ve worked with them a lot.”
An adjacent shed, funded by a $700 grant from the Seagull Centre in September last year, will eventually house an irrigation pump, and the committee is now working on pipes to move the water from the tanks to the bush, around 100 metres away.
The pipes will be connected to a manifold at the treeline, and pumped through hoses laid around the boundary.
“They’ll be movable hoses. And we’re going to make them out of the fire brigade’s [old] forestry firefighting hose which is made to weep so they don’t get burnt when you drag them through the fire, [and] modifying those with holes to some degree as soaker hoses,” Jim said.
“So we’ll have the pump running, we’ll have two or three lines coming off that manifold. But we’ll also have the option to bring it around if we do some special planting in some area we want to water.
“Because if we can put more water in here in the summer, [the bush will] generate itself, we won’t have to worry about planting. That’s what we want, then we’ve won the game.”
Jim, who formerly worked for the Department of Conservation’s predecessor the NZ Forest Service, said he realised how important it was to keep the trees watered when researching rainfall records.
“We had three years in a row where we were under one metre [of rainfall]. That’s the first time in 50 years of records that I read that we had three dry years in a row,” he said.
“That was before the dieback started. And I believe that was the trigger point to make the trees that weak that the pathogens got at them. So that was the trigger point to make me think, we’ve got to do something.”
The committee received advice from the Waikato Regional Council while planning the project. The tree stand itself is being monitored by the council as part of its push to restore and protect indigenous forest stands.
“The council has been leading research into apparent dieback… Early indications suggest a potential link to climate stress, with trees that are periodically flooded appearing to be more affected than trees in permanently wet or permanently dry locations.
“The stress of experiencing flood and drought extremes may make these trees more susceptible to attack by soil pathogens (Phytophthora and Pythium species), which have been detected under kahikatea trees,” a statement from the council said.
Council scientist Yanbin Deng said they were impressed with the dedication of the volunteers looking after the domain.
Council visits to Turua in 2023 and 2024 found most of the domain’s trees had remained healthy, with the forest experiencing a slightly increased health score for improvements in species composition and winter bird food species, thanks to recent planting undertaken by the domain volunteers. Several of the trees have been tagged for ongoing monitoring.
“It’s an experiment… I don’t think it’s been done before. But it just makes sense to me,” Jim said of the irrigation project.
“[Dieback] is here. What we’re going to do is keep the trees healthy and they’ll fight it off.
“In a hundred years’ time [I hope] it starts to look like a natural native bush. But it’s not a scientific project. It’s an asset to the town. People love it, they bring a plastic chair around and sit here and just take in the ambience. And that’s what we want.”
