By Janean Creighton, Oregon State University, Forestry & Natural Resources Extension
Climate change is predicted to accelerate through the 21st century, leading to changes in forest species distribution, productivity, and disturbance regimes¹. These changes may have profound impacts on the public and private benefits from forests; as well as managers’ strategies to sustain these benefits into the future. As our understanding about potential climate change impacts on western U.S. forests improves, land managers are developing adaptation strategies to meet these challenges.
How do forest managers perceive climate change impacts, and how is this reflected in their forest management strategies? To get a land manager’s perspective, I interviewed Sara Lipow, Forest Geneticist for Roseburg Forest Products.
J.C. Tell me about your background.
S.L. I am the Forest Geneticist for Roseburg Forest Products in charge of tree improvement, and have been since 2008. Before that, I was the geneticist for the state of Oregon, working in ODF’s Private Forests Program, where one my key responsibilities was to assist small woodland owners. I established a seed bank to provide small woodland owners with access to genetically improved seedlings, which are now widely available for purchase through private nurseries. I’m also a small woodland owner myself, with 40 acres in Lane County.
J.C. From the perspective of a geneticist and a small woodland owner are you noticing significant changes in the resource in terms of climate change?
S.L. During the past few years, trees have been developing much earlier in the season; especially this year: trees began flowering and breaking bud several weeks earlier than is typical. Tree phenology—the timing of various developmental stages–is linked to climate. Trees are flexible with respect to phenology and climate, but there are also genetically based adaptations. For example, the timing of bud burst will differ for a Douglas-fir tree from Cascadia and Coos Bay, even if they are grown on the same site and this is genetically controlled; but the timing of both will vary with climatic conditions.
J.C. What other changes are you seeing that are linked to climate?
S.L. I work primarily with Douglas-fir in western Oregon. There’s a lot of die back of individual branches and tops of trees that’s happening currently, which is drought related and seen primarily on droughty sites. If you drive up and down I-5 right now, you can see browning at the tops of some trees and many dead, individual branches. Trees growing along the highway are often on sites where soil is compacted or conditions are otherwise not ideal for tree growth, which makes the phenomena especially visible along roadsides. It is less prevalent in healthy, appropriately stocked established stands.
J.C. Are you seeing this primarily with Douglas-fir?
S.L. I’m seeing this drought related die-back with a range of species.
J.C. Are there areas that you see as being more vulnerable to changes in environmental conditions? Anything you’re seeing that’s unexpected?
S.L. Swiss needle cast is a native pathogen that affects Douglas-fir, especially along the coast of Oregon, and results in reduced tree growth and needle loss. There are different ideas about how much Swiss needle cast might be expected to change with climate change. We know the timing of when the pathogen’s spores are released – and thus the likelihood it will infect trees – is linked to environmental cues, but we don’t have a complete enough picture of this ecological interaction to make good predictions about how disease severity will change under different climate scenarios.
There has been increasing concern about intensified Swiss needle cast in the Coos Bay area, which may be linked to climatic changes. So for landowners with property in the Swiss needle cast zone or on the edge of this zone, there’s no clear picture whether they will see more or less of this disease. Then there’s fire, of course. Climate impacts will impact fire regimes—something of present concern. Depending on the patterns of climate change, some outcomes could be helpful, while others will be harmful.
J.C. How could climate impacts be helpful?
S.L. Climate models are not yet accurate at the local level. We don’t know whether drought-limited sites will get wetter. It is possible that we could see an increase in productivity in some of our forests, IF droughty sites get wetter at the right time of year. We really don’t have a handle on that; as the precipitation models at a local scale are uncertain. Warmer temperatures also could mean that trees will break bud earlier, have a longer growing season, and potentially grow faster.
J.C. In the forests that you are managing, are you prioritizing specific management areas?
S.L. We are increasingly focused, at a research level, on understanding how different populations of Douglas-fir grow in different environments. Oregon has got a lot of environmental variation linked to geography and as you move from the coast, inland, and into the mountains, the change in environment can be viewed as a surrogate for changes that may occur in climate over time. We are spending a lot of effort understanding the adaptation of trees to their environment so we can make informed decisions on where we plant different sources to ensure that they remain well adapted to current and future climates. In Oregon in the 1970’s, there was an idea of extreme local adaptation, and people developed very small seed zones; for a few decades in the Pacific Northwest most landowners planted very localized seed sources. There has been an increased understanding that this was not biologically based, and that Douglas-fir is much more flexible and widely adapted and can be safely moved longer distances. Genetic research linked to climate and the environment provides a better understanding of the adaptability of populations and how they respond to environmental variation.
The forest industry and most public agencies overwhelmingly plant genetically improved stock when they reforest. Such genetically improved seedlings are available for non-industrial landowners; and are a good choice for landowners that want to guard against future climate impacts. This is because the trees in the tree improvement program—those producing the seed used to grow the genetically improved seedlings–have generally been selected for wide adaptability. They have been shown to perform well across a range of sites. So while there are limited options for what people can do with their existing forests, if landowners are planting a new forest, I would encourage the planting of genetically improved seedlings. These seedlings provide high return on investment. Genetically improved seedlings are available for Douglas-fir and coastal western hemlock.
J.C. What about the drier east side forests?
S.L. Well, for the mixed-conifer stands the safest approach from an adaptability standpoint is to put them back into mixed-conifer stands; but of course you have to weigh this from a landowner value perspective. There are different values for different species.
J.C. So one of the adaptation strategies you see is the planting of genetically improved seedlings. Is that happening all over the region?
S.L. Yes, in western Oregon and Washington the overwhelming number of Douglas-fir seedlings planted on both public and private lands has been tested by tree improvement programs.
J.C. So if a group of landowners were to ask you, “What’s one thing I can do to prepare for climate impacts” it would be to plant the improved seedlings.
S.L. Yes. That would be it. The Oregon Department of Forestry puts out an annual publication: “Sources of Native Forest Nursery Seedlings” for small woodland owners. Landowners can look in this publication to find nurseries growing seedlings adapted to their region, including genetically improved ones.
J.C. In terms of the vulnerabilities to increased pathogens, etc., what’s the strategy?
S.L. Manage for as healthy a stand as possible. Overstocked stands can be more prone to pathogens and drought.
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