We use climate modelling to predict forest masts a year ahead. We then monitor seed the following summer to check our prediction and measure any seed present. Along with our tracking of current predator numbers, we can use this for predator control planning.
When beech forests seed heavily, they can produce up to 15,000 seeds per square metre or 250 kg of seeds per hectare. This provides a bounty of food for native insects and birds but also for rodents, whose populations can expand rapidly and fuel an explosion of stoat numbers. By forecasting a mast and measuring the amount of seed, we can be prepared and plan measures to protect our native species.
We've been sampling beech and rimu forests since 2011 to measure the size of forecast mast events. Read what we've found in our most recent monitoring work below.
Lull in seeding in 2020
Our sampling of beech and rimu trees in February and March has confirmed there is no significant beech or rimu forest mast in 2020.
A DOC team snipped branches by helicopter from more than 1100 beech and 600 rimu trees at 46 sites across the country in the sampling programme. Back at the office, workers processed the beech and rimu samples and counted any seed present.
Results from seed sampling show there is little or no beech seed across the South Island and only a moderate mast at several North Island sites. Only sites in the Kaimanawa and Kaweka forest parks showed moderate seed present.
Rimu sampling also showed very little ripe fruit and new tips indicating no rimu mast this year or next. Rimu fruit and seeds take 15 months to mature after fertilisation.
The 2020 forest seeding areas for beech and rimu are highlighted on the maps below:
Estimated seeding in 2020
See larger maps
Our 'mega' mast in 2019
Watch our 2019 video on forest sampling to learn more
In 2019, our scientists found beech forests around the country were seeding with particularly heavy seeding in the South Island and a mix of moderate to heavy seeding in the North Island. Tussock grasslands in the South Island also produced lots of seed.
Fruiting in South Island rimu forests was also heavy and exceptionally so on Stewart Island/Rakiura and in the Catlins and Taramakau valley on the West Coast. In the North Island rimu fruiting was more variable.
The 2019 forest seeding areas are highlighted on the maps below:
Estimated seeding in 2019