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Knowing when native regeneration is for you and what you should do about it.

Date: 15th May 2023

Last year I visited Motupohue/Bluff Hill at Bluff in the South Island. I am used to the fast-growing nature of our native plants in the Hauraki Gulf and Northland, and I find it hard to get my head around the shorter growing seasons in many areas of the South Island and how long it takes for many South Island species to grow.

At Motupohue the tenacious and smart work of the Bluff Hill Motupohue Environment Trust has led to native regeneration that looks like it’s on steroids from the small understory colonisers – ferns, hebes and poroporo with its showy purple flowers to mid canopy species like makomako/wineberry and akepiro/tree daisy. It’s a stunning sight especially when you consider the placement of this hill right next to the wilds of Foveaux strait where the wind can blow you off your feet.

A key stage of wilding pine work is what to once you’ve got rid of all the trees or at least most of them. Do you leave nature to its own devices and hope for the best, do you give it a bit of a helping hand e.g., animal and pest plant control or do you go all out and get into a restoration project and planting up a storm?

Adam Forbes and a group of researchers from Manaaki Whenua have just collaborated on a really interesting paper entitled Knowing when native regeneration is for you, and what you should do about it. The Aotearoa New Zealand context.

The paper describes a step approach for assessing at a site scale whether forest restoration can most efficiently be achieved via active or passive methods, or combinations of the two.

The assessment covers the main biotic and abiotic factors which explain the probability of native tree establishment. These factors are mean annual rainfall, mean annual air temperature, proximity and composition of adjacent seed sources, landform type, slope aspect, slope, topographic exposure, and the presence of existing woody cover.

The authors then describe the main management interventions that will be required to support successful natural regeneration outcomes and highlight the importance of strategic natural regeneration for achieving large scale restoration for the betterment of both our climate and biodiversity.

It’s a really easy to read and thought-provoking paper with excellent advice on how to make informed pragmatic decisions as to whether to let nature take its course, give it a bit of a helping hand or help it a lot. I think it’s a really relevant paper with where some wilding projects are at in their management cycle and even for some that might be starting and thinking about what to do when we have controlled all the trees as often good planning starts by working backwards from your ultimate goal.

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