Station 15

Recovering forest reveals its history like chapters in a book if you take the time to read the pages of the story.

Kereru, the world's largest pigeon, seek out puriri trees to feed on their berries.

Our eastern trapline sidles across the slopes of a steep stream valley as it heads up to the watershed ridge line. Once cleared farmland, these slopes are now reforested with mature canopy kanuka forest. Along the floor of the valley, remnants of the original forest are still present with these trees marked out by their size and height.

Station 15 on the trapline is at the confluence of two headwater streams and is a great place for a break from setting traps before the steep climb out of the valley. On the cool, moist stream bank stands a very large puriri tree that not only provides a massive structural canopy it tells the story of this forest.

This puriri predates the clearance of the valley and it would have been a large tree when the axes arrived. It clearly became a mature tree inside a forest as its branches are erect and it does not have the spreading canopy of puriri that grow in the open. It has grown up into a light well that was created when an even older tree fell and tore a gaping hole in the original forest canopy. This tree is the first chapter of the forest’s story and it proves that mature broadleaf forest has persisted continuously on this site for at least centuries.

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Puriri are a very important part of northern forests as they are a wildlife larder that carry nectar and berries in all months of the year. Its fruit are large red berries, about the size of a cherry, and its flowers often produce more nectar than can be taken by birds. It is especially important as a food source in winter when it flowers most heavily, and when little other nectar is available in the forest. While tui love the flowers, it is the kereru / wood pigeon that eats and transports the fruit with its enclosed seeds.

Kereru are the largest pigeon in the world and the last effective seed disperser of New Zealand’s large fruiting trees in mainland forests including tawa, taraire, karaka, puriri and kohekohe, especially now that weka are absent from these habitats. They are effectively seed bombers able to carry large quantities of fruit in their gut over long distances before depositing these under a favoured tree when they stop to feed.

Growing under the canopy of the puriri at Station 15 are young tawa, kohekohe and puriri, some several metres high and some more than 10 metres high. Small fruited trees are also there including mahoe, kawakawa, red matipo and pigeonwood but away from the puriri, forest regeneration includes only the small fruited trees dispersed by smaller birds such as tui and waxeye. That kereru visit this puriri and continuously bring large fruited tree species into the valley is the second chapter of the forest’s story as it shows this valley is still connected to similar remnant forest patches throughout the area with seed dispersal actively occurring.

The third chapter is much more recent and is written in the forest as scars that remain after a terrible injury. The puriri, with its understorey of canopy trees of the future, stands on the floor of the valley and upslope the composition of the forest changes to small fruited tree species and then large kanuka, the pioneer species that has reclaimed the open pasture and dry slopes, and which will gradually be replaced by climax species as equilibrium returns to the forest.

Recovering native forest lacking understorey and shrub layers as a result of wild mammal grazing.

From the vantage point of Station 15 the view stretches down the stream valley and it is remarkable how far you can see. The forest below the canopy is open. Yes there are twisted vines of supplejack climbing up to the light and thick ropes of kiekie clinging onto tree trunks. What is missing is a carpet of seedlings on the forest floor, thickets of shrubbery and voluminous subcanopy below the roof of the forest. What is there is a slowly regenerating flora dominated by unpalatable tree ferns with occasional emergent rewarewa.

The forest is a donut that has been hollowed out by the incessant trampling and grazing pressure from feral goats, wild pigs and the occasional red deer, who all work at ground level, aided and abetted by possums who extend the grazing pressure up into the trees. A closer look reveals no sprays of red berries on the trunks of the nikau palms, no masses of purple fruit on the five-finger and no spikes of orange and yellow seeds on the kawakawa. No doubt the birds got some but these have been consumed by the unseen mouths of rats and mice who strip bare the forest’s cupboard each and every night.

The Silent Spring has become another silent summer as the forest struggles to recover under incessant pressure from invasive mammals who disrupt, interrupt and corrupt the natural processes that would heal these ecological wounds. Without adequately addressing all introduced mammals in our forests our predator free aspirations will deliver wildlife hollow forests unable to support the potential fauna recovery that predator control promises.