North Canterbury Farm Forestry Field Day 25th March 2015 Wilding Pines in the Craigieburn area.
Way back around the end of the 19th Century, the NZ government got a little worried about what was going to happen in the future as the native timber stocks were rapidly dwindling and the native timbers took too long to grow. Much research and trials later, they hit on Monterey pine (Pinus radiata) from California as the saving grace. A tree that excelled in the NZ climate, grew just about anywhere it was planted and could be harvested on a 30 – 40 year rotation with an average diameter in the bottom log of 80cm, with another 2 or 3 6m logs above that. A few other pines joined the mix, particularly in the South Island, Scots pine (P. sylvestris), Ponderosa pine (P. ponderosa), Corsican and Austrian pine (P. nigra ssp), Bishop pine (P. muricata), lodgepole (P. contorta) and for erosion control mountain pine (P. mugo). Douglas fir (Pseudotsuga menziesii) sold as Oregon, larch (Larix spp.) and a couple of cypresses. Scots, Ponderosa, Corsican, lodgepole, Douglas fir and Larch were widely planted for wind shelter on high country farms.
By the end of the 2nd World War, overzealous land clearance, mismanagement, and feral deer, goats and pigs were causing steep hill country and mountain lands that should never have been deforested to slide into the rivers sending waves of shingle downstream resulting in increased flooding. Along with wild animal control extensive planting programs were undertaken to stabilise the falling hills. Again, exotic species were called on for their rapid growth, lodgepole and mountain pine were integral components.
As NZ has no native pines, any pine that is not planted is termed a wilding and wild Douglas fir and larch get gathered up in the catch all of wilding pine. Some of the pines and larch are able to grow up to 500m higher than the natural tree-line and with our wind-lashed landscapes seed are able to travel for many kilometers. Wilding pines are a serious problem from the Rangipo Desert south. In the South Island there are huge areas that are now dominated by wilding pines, transforming landscapes and smothering native ecosystems. For the summary on Wikipedia go here.
Back to the field day. We were led by Nick Ledgard (3rd down here), retired Forest Research scientist, who has a life’s experience with the introduced conifers of the Craigieburn Range, Castle Hill Basin and the dynamics of wilding pines. First stop was at Lake Lyndon where Nick pointed out that a small group of pines (Corsican?) at the rest area had started to spawn a new generation on the surrounding tussock slopes and were promptly removed with several years of follow up to get the wildings. If this hadn’t been done everything we could see would now be dominated by pines.
Then on to Castle Hill Station where lodgepole remain in shelterbelts. Low in the landscape and surrounded by grazed pasture these trees are not currently a significant problem for the surrounding natural areas.
At Castle Hill Village, Marie Goldring told us the history of this alpine style, recreation village. Mostly bach’s with 125 houses there are only 18 residents. Conifers, particularly lodgepole, Douglas fir and larch were planted to enhance the alpine feel. Now with the growing realisation that these species are a potential threat to the natural environment a strong group of house owners are removing the conifers and replacing them with native beech. Not everyone is in agreement on this so there are interesting times ahead.
Moving on to the former Craigieburn Forest Range Experiment Station Nick told us about the history of the research, Flock Hill Station and the early plantings. Planting started in 1956 on slips and screes. It was later found out that a lot of the bare rock and scree is natural and not induced erosion at all. However those areas where yellow subsoil can be seen probably are induced but not the rocky hill tops.
It’s these hill tops that initiate the problem with wildings as they are launch sites for wide dispersal. Even with that advantage of height and exposure it takes severe (140km/hr) wind events to disperse seeds over any great distance, most seeds falling near their parent tree. Lodgepole, mountain pine, Scots pine, Douglas fir and larch are the main culprits here.
Control work started around 2006 focusing on launch sites and containment of the core area by eliminating outlying pines. In the meantime the non-urgent areas have filled in as can be seen in the photos below.
It’s pretty damn impressive for under 10 years but so too is the effort that has gone into turning this around. Mostly it has been chainsaws and hand pulling for control but recently there has been enough funding to use herbicide from a helicopter and a big team of volunteers are chipping away at the rest.
I was disappointed at the end of the day when a couple of learned fellows (scientists) took up the do nothing argument.
Waste of time and money; let them go; the land is good for nothing; better in trees…
Never mind that the timber from wilding pines is worthless, most would be too difficult to get to anyway and the downwind area has around 300km2 of land that is low productivity, best left to growing wool and serving nature. But what really galls is the old dinosaur attitude that if you can’t eat it or sell it, it has no value. Even the landscape would change and there is actually a value in keeping pines out as they would reduce the water yield from that 300km2 by up to 50%. There’s a host of plants and associated organisms that thrive in these barren landscapes, it would be a shame if they were smothered out by weeds gone rampant.
After that you might think I was wild about wilding pines and you’d be right. It’s not that I’m against pines but care is needed in choosing and siting exotic species in our landscape, particularly the Eastern South Island. Below are a trifling few of the things I wouldn’t want to lose and examples of the landscapes that would change (wiping out native ecosytems) if we turned our backs on wildings.