Making Wildlife Trees – Does it Work?

Ken Bevis, Wildlife Biologist, Washington Department of Natural Resources,

Obi-Wan Kenobi of “Star Wars” fame knew the challenge he faced when dealing with big problems, but he also knew how to deal effectively with these obstacles by using multiple tools. Standing dead trees in the forest are like the outnumbered rebels going up against the ruling paradigm demanding their destruction, but they can be maintained by using creative strategies.

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Wind River Canopy tower (formerly crane), July 2019. Devices are measuring carbon and other atmospheric variables within the forest canopy. (Photo by Ken Bevis, DNR)

Challenges in active forest management include identifying, protecting, promoting, and maintaining vital wildlife habitat features, while continuing to manage stands for other objectives (such as timber and recreation). Standing dead trees, or “snags”, are crucial elements of a forest that often require a conscious effort (and a bit of paradigm-busting) to keep around. Earlier this year, I visited the Wind River Canopy Crane research site and gained some insight into this issue.

Late in the 20th Century, a remarkable research project was established deep in the Douglas-fir forests of Skamania County. In 1994 and 1995, the University of Washington’s Dr. Jerry Franklin and a host of other cooperators installed a very tall (>85 meters) construction-style sky crane in an old-growth stand near Stevenson that reached well above the trees and allowed researchers to dangle and measure everything at varying levels in the forest canopy. The sweep of the long arm (the “jib”) covered a study area of about 5 acres. Over a period of approximately 16 years, various studies have been undertaken using the jib and attached gondola to investigate the ecology of the old-growth forest, with an emphasis on the tree canopy. These studies have looked at carbon dynamics, tree leaf morphology, nutrient cycling, photosynthetic rates, wildlife use of different canopy levels (by species and by season), and just about anything else the gentle reader might imagine you could study while in controlled suspension 30 to 180 feet above the forest floor in the midst of the amazing, three-dimensional tree tops.

In order to place this gigantic piece of equipment in the research area, significant infrastructure work had to be done. High-power electrical lines were laid beneath the reconstructed road, various machinery and the enormous pieces of the crane itself had to move over half a mile into the forest stand, and the monstrous tower had to be assembled. These were daunting tasks, replete with all manner of logistical and safety concerns.

This is an old-growth forest. A significant element of these forests are standing dead trees, which are known for their critical ecological roles in nutrient cycling and habitat, among other functions. Unfortunately, snags are routinely removed (or simply cut down) in the interest of human safety. Hence, to address safety concerns involving all of this activity, hazard trees within striking distance of the road and crane were identified. More than 60 standing dead trees, many of them of quite large in diameter, were marked for removal.

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Topped snag with jagged top created with climber and chainsaw 25 years prior to this photo – note its height. This one is back from road and could be maintained at a greater height. (Photo by Ken Bevis, DNR)

At the time, Dave Shaw, now a forestry professor at Oregon State University, was the director of the Canopy Crane Site for the University of Washington, working with legendary forester Dr. Jerry Franklin. Members of the research team had concerns about maintaining habitat quality and ecological integrity on this research site but were prepared to do what was needed to install the crane and make the project work. Tim Brown was brought in to do the necessary hazard tree work. Brown is a pioneer in wildlife tree creation techniques and helped the team generate an alternative to simply cutting these snags down.

“When I arrived on the site, I knew I wasn’t going to just cut these trees down,” Brown recalled. “We had to do something else.”

The team came up with a plan, and Brown used his considerable expertise to shorten and modify the snags in various ways to address safety concerns, while emulating natural processes and keeping some of the habitat quality in the forest.

“This is a 500-year-old stand, and the objective was to maintain vertical forest structure and habitat quality on this research site,” Brown said. “We wanted to maintain the natural habitat as much as possible. We custom carved (with chainsaws) each top based on species, diameter, decay classification, hardness, and location to meet safety concerns. Some trees closer to the road had to be shorter to meet safety issues.”

A remarkable, and risky, element of this project was taking the tops out of standing dead trees. Brown’s expertise and use of creative techniques, including dangling by ropes from adjacent trees, made this possible.

“Some of these trees were really sound, but some were extremely fragile. We removed the weak parts when we could to help those trees persist,” Brown said. “The tops were carefully laid between existing vegetation features to reduce damage whenever we could.”

The tops were treated in different manners, sometimes left extremely jagged as if they had broken off, sometimes with deliberate crevasses to trap water, bird droppings, and other forest litter. All were shortened considerably.

“Sometimes making the trees shorter enables them to stand longer,” Brown said. “A created wildlife tree will usually be substantially shorter than the original tree.”

Then the forest director, Shaw was key to allowing these trees to be shortened and maintained as habitat, rather than being knocked down or completely removed. The work was done using standard arborist and logging technology, but with cutting-edge (wink-wink-nudge-nudge) techniques emphasizing habitat.

David Braun worked on the project in 1999-2002 as the “Arbornaut,” a position created for facilitating the safe movement of scientists in the gondola hanging from the jib so they could access the canopy for research. He also worked on canopy studies from the gondola with Shaw.

In 1994, just before the crane was erected, Braun worked with other scientists in mapping all of the trees and vegetation in the original core area around the selected crane location. While doing that, he witnessed Brown shortening and carving up the snags. Braun was intrigued by Brown’s work, and since that time wondered what the fate of these altered snags would be.

So, what’s happened to these reduced snags 25 years later?

Braun, (now operating his own arborist service in Hood River Oregon) with Shaw’s approval and Brown’s assistance, is working on a monitoring project to document changes in these wildlife trees over time. Our existing knowledge of long-term changes to dead trees, with real-time measurements, is limited (remember, forestry as a profession in America is just over 100 years old and some snags can last for centuries!).

This project sets out to measure key variables on these trees at intervals over the next decades, with an open end to the project.

“The first step is to describe the exact size and condition of the snags 25 years after they were shortened,” Braun said. “There is a body of research on what happens to snags after fire. People have shown that tall, skinny snags tend to break first, and bigger, thicker snags will take longer to break. These breaks typically occur well below the tops, and tall snags sometimes fail at the base, depending on species, decay, and site conditions.”

Braun intends to investigate these and other questions.

“How do shortened snags behave compared to snags that have not been shortened? How would modifications to the cut surface (such as roughening with a chainsaw) effect the subsequent processes of decay and colonization by plants and use by wildlife. My hypotheses will test these concepts,” Braun said.

The initial observations indicate that these 60-plus snags have not changed very much in the first 25 years.

“How long do these snags last after being treated and how much hazard was abated for the investment?” Braun said. “So far, it looks like they have disintegrated very little and apparently none have fallen over.”

Variables measured in the snag monitoring project include: tree species, snag height, diameter, amount of bark present, presence/absence of feeding or cavity excavations, wildlife evidence, decay conditions (using a standard 1 through 9 rating system), and the percent cover of plants, moss, and even lichens on the cut surfaces.

“The Canopy Crane is a long-term research site, with the first plots established in 1994, so there is a history of repeated measurements over time,” Braun said. “This project is part of that.”

Shaw acknowledged the first phases of the monitoring, saying, “We are amazed at how they are persisting in this first 25 years, and how slowly they are decaying.”

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Dr. Dave Braun gathers data on a short wildlife tree. Even after 25 years, the bark is still intact and a plant community has established itself on the cut surface. (Photo by Ken Bevis, DNR)

The jib of the crane was removed in 2005, and UW is no longer the lead on the project.

It continues under the auspices of the National Ecological Observation Network (NEON), a project funded by the National Science Foundation. The snag monitoring initiated by Braun fits in with the long-term interests of NEON research at the Canopy Crane site. And the tall, tall crane tower is still there, covered with sensors sniffing and reading the forest canopy right now.

So, how does this matter to small forest landowners? Most landowners have a deep interest in maintaining all of the functions of a forest ecosystem, including providing quality wildlife habitat. Perhaps the best way to provide such habitat is maintaining and enhancing key elements of the natural forest ecosystem on our land in perpetuity. Dead wood is one such key habitat element, and shortening potential hazard trees to maintain habitat can be a viable tactic for small landowners.

Like snags and logs? Me too. Send me your best photos of wildlife using dead trees and, if you have them, your created wildlife trees!  Thanks, and May the Snags be with You.

Here are a couple more stories on the Canopy Crane project: