Farming Old-Growth Forests

by Charly Kearns, October 2015

Overview of forest stand N022, which will be thinned in the coming years.

Overview of forest stand N022, which will be thinned in the coming years.

The Land Trust’s Mount Rainier Gateway Forest Reserve is a 2,500 acre corridor connecting the Elbe Hills State Forest to the west with the Gifford Pinchot National Forest and Mount Rainier National Park to the east. This is roughly half of the land owned by the Land Trust, and nearly all of it was previously owned and managed by industrial timber companies. The Mount Rainier Gateway properties were purchased with Section 6 Endangered Species Act Funding, with a particular interest in creating a buffer for northern spotted owls and marbled murrelets, both of which nest in nearby old growth forests.

Old growth forests are complex ecosystems, with structural and biological components. Of course they have big, old trees, but dead trees are just as important. Spotted owls nest in cavities, which are usually found in old snags. Downed trees will decay and provide food for insects and fungus, which will form the base of the food chain, and also provide an excellent growing platform for the next generation of trees. Marbled murrelets require large-limbed trees to serve as nesting platforms, which only develop in very old conifers.

The Land Trust’s property is a mosaic of second-growth and third-growth forests, which have been managed to produce fast growing, straight conifers, which can be harvested in 40-50 years. This is not the sort of management strategy that produces good habitat for species that require old growth forests. However, some of the same forest management techniques used by the timber companies can be repurposed to speed up the development of old growth characteristics.

Recently, I met with a Natural Resources Conservation Service (NRCS) forester to take a look at a stand of young trees on the property. The stand encompasses over 200 acres and is composed of 25 year old trees. The trees are very tightly spaced, and in the midst of some intense competition for available resources. If left alone, the trees would continue to grow quickly in height, without putting on trunk diameter. This creates tall, thin trees which are likely to blow over sometime down the road. This is a natural process that would eventually allow the largest and healthies trees to dominate. However, the process can be sped up by selectively removing the weaker trees.

We spent a few days walking through the thick, wet trees, taking tree measurements and assessing the best way to manage the stand. In some places, we counted as many as 4,000 trees per acre (tpa). This is more than 10 times the number of trees that is recommended for developing large, healthy trees. Over the next few years, we plan to hire a forestry crew to work through the stand and cut out the weakest trees. This will give the larger trees the space they need to begin to put on diameter and maintain a healthy crown (the green stuff). The crew will also be able to influence the species composition of the future forest. Most of the stand is dominated with Douglas fir, western hemlock, and noble fir, with scattered red cedar. By favoring the hemlock and cedar, the forest will move towards a true climax forest earlier than if it were left on its own.

Returning to the truck after a soggy day, we hiked up through one of the few remaining stands of old-growth forest on the property. It was a great way to finish out the afternoon. We found lots of cool plants, and, my personal highlight, an old Doug fir with an agarikon conk fungus on it (one of the longest lived species of fungi and an ecological indicator). I feel most at peace in these ancient forests, with unknown ecological processes happening all around. I am happy to know that these trees will outlive me, and the next 40 generations. And I have hope that the owls, murrelets, plants, insects and mushrooms will continue to find refuge in places like this.