TreeTopics

The phone has been ringing off the hook lately with calls from people describing sick and dying Douglas-fir and other conifer trees. The trees are of a wide range of ages and in many environments and settings, although most calls have been coming from within the valley margin and have to do with young trees.

So far, the answer is generally: “It is drought stress”.  Huh, in May? Well it has been a dry winter and spring, … but that is not the issue.

My best explanation is that we had a pretty hard end of summer last year. Remember that? NO rain until mid-October then, Boom, it was winter. By then, many trees had started running out of water, killing tops or branches, and leaving leaders and branches susceptible to attack by various opportunistic pests.

We started seeing a few classic signs of drought stress (tops dying and branches “flaring out”) at the very end of the season last year, but late enough that many did not have time to show up before the weather turned. Injuries had occurred, so it was just a matter of time before they expressed themselves, which is happening now. The recent hot weather seems to have made it more sudden and dramatic.

This happens from time to time. Here are two good articles a few years back by the ODF Forest Health team explaining Dead tops and Branches (with Good pictures), and about Drought and Mortality.

It is important to keep in mind that the Willamette Valley can be a challenging climate for trees. Many of our soils in the valley are poorly drained, which is hard on most of our conifers, and other soils are fairly shallow and cannot hold much water. Also our summers are hotter and drier than in the mountains. Heat and drought stress can kill trees outright, or more often just put the trees under stress, which can then lead to pest problems (as explained in the two publications above). From what I am seeing and hearing, the major cause of the problem now seems to be drought stress. Insect or diseases which able to take advantage of a stressed tree’s condition may sometimes be involved, but they are generally not the cause of the problems.

Finally, weather can be more stressful when trees are overcrowded, so thinning stands to keep trees vigorous with adequate growing space may be helpful in the long term. Right now, we just have to wait it out, and hope we get some serious rain this year, or we will see this problem intensify.

We all better get out there and wash the car…..

Brad Withrow-Robinson

In response to last week’s post on the value of dead wood in the forest, I received this e-mail from a landowner:

“We’ve never left much on the ground in the way of dead wood…not during logging, but wind damaged, etc.  Our thought has always been that these rotting logs increase the insects in the forest, both good and bad. Is this a valid concern and if so, where is the balance between bugs and wildlife?”

He raises a point worth exploring. While calling an insect “good” or “bad” is a matter of perspective, for the purposes of this discussion let’s assume that “bad” insects are those that cause economic or environmental damage, and “good” insects are those that don’t. The vast majority of insects that inhabit western Oregon forests fall into the “good” category…with a few notable exceptions.

One of these “bad” bugs that the e-mailer might have in mind is the Douglas-fir beetle. This time of year, the adult beetles are flying around in search of Douglas-fir trees where they lay their eggs underneath the bark. Their favorite targets are large diameter, freshly downed logs—or standing trees that are weakened from another cause (root disease, soil compaction, etc.). Through the summer and winter, the eggs hatch and the larvae grow as they tunnel around under the bark (this activity is what kills the tree). The following spring, they have become adult beetles, and they fly away in search of new homes. If they can’t find another weak tree or fresh log, they will go after a healthy tree.

reddish bark dust in bark crevices is a sign of the Douglas-fir beetle (Photo: Elizabeth Willhite, bugwood.org)

Healthy trees can withstand a low-level Douglas-fir beetle attack, and in normal circumstances there are rarely enough beetles around to cause concern. The problem arises when the beetle population builds up and lots of them infest a healthy tree at once. When does that happen? In situations where there is a lot of freshly downed or damaged wood on the ground for them to target initially – like after a winter windstorm.

Here’s a true story for illustration.

In fall 2009, a landowner in the Coast Range was hit hard by beetle kill to his otherwise healthy, 100+ year old forest. Why? Here’s how we think this may have played out.

• The stand is adjacent to a sawmill.
• The big windstorm of December 2007 created lots of blowdown along the coast, though this particular stand was too far inland to be damaged.
• Some of the coastal blowdown was not salvaged until summer 2008…too late, because Douglas-fir beetles had already found them during the spring.
• The salvaged logs were brought to the mill, along with the beetle larvae living under the bark.
• Then, in late 2008 the recession hit and the mill curtailed operations. The logs sat in the deck…and the beetles matured.
• In spring 2009, they emerged and flew off to the neighboring stand, where they attacked the healthy, mature trees.

It was a sad situation, especially since the landowner had to cut more trees to avert further beetle damage, and in a poor market.

So, back to the e-mailer’s question: does retaining snags and downed wood for wildlife create a forest health risk? The take-home messages are these:

• Most insects are not forest health risks.
• In western Oregon, the Douglas-fir beetle (the “baddest” dead wood-inhabiting insect) only thrives in FRESHLY dead or downed trees. Once the snag or downed wood has been dead for more than a year, it is no longer a target. Instead, it will become inhabited by the dozens of “good” bugs that feed wildlife.
• There needs a LOT of this fresh down wood to pose a forest health risk – like after a storm. According to Oregon Department of Forestry, a good rule of thumb is that fewer than 3 FRESH down logs/acre does not present a hazard.

After a windstorm or other stand-damaging event, yes, prompt salvage is important in order to prevent a beetle infestation. But, when scattered trees gradually die in a stand from other causes, it is hard to imagine when this would create a risky situation with respect to bark beetles. And during harvest activities, you can be strategic about how much dead wood is left behind, and in what conditions.

We appreciate it when readers respond to our blog posts. We like your e-mails, but you can also respond by commenting directly on the blog, where other readers can contribute to the conversation.

Amy Grotta

I recently was at a conference on “Wildlife in Managed Forests” sponsored by the Oregon Society of American Foresters and the Oregon chapter of The Wildlife Society. Speakers discussed current research on wildlife damage and wildlife habitat enhancement projects across western Oregon and Washington. There was far too much interesting stuff for this short article, so in this post I will focus on one recurring theme of the meeting. It’s one of the easiest and most effective ways to maintain a wildlife-friendly forest: retaining dead wood as snags (standing dead trees) or downed wood (on the ground). I’ll return to some other topics later.

Evidence of pileated woodpecker foraging on a snag

Nearly 100 species of animals in Oregon (mostly birds) use snags. First, birds such as woodpeckers forage on insects living in these trees and then excavate cavities in them for nesting. Later, these cavities are used by other bird and mammals for nesting and shelter. Raptors such as hawks may also use snags as perches, from which they can prey on voles or other mammals that might damage seedlings.

With snags, the rule of thumb is “bigger is better” – smaller diameter snags will only be used by smaller animals and do not last as long. So if scattered trees die on your property, consider leaving them for wildlife, keeping safety in mind. Snags can also be created artificially during harvest. Mechanical harvesters can top trees up to 20 feet or so, and so can create a snag out of a tree with a defect down low but a merchantable top. The second best option, if you cannot safely cut the tree up high, is to fell the tree and leave the defective portion in the woods where wildlife will use it. Now it has become “downed wood.”

Just a few days after the workshop, I was out visiting with a landowner near Rainier. A small harvest had just been completed, and the logger had left a big, defective log alongside the unit (shown in photo below). The owner wondered, could it have been sold as a pulp log? Should she see if someone wanted it for firewood? I suggested that the log was already providing value, and probably more than what might have ended up in her wallet from these potential uses. Downed wood is used for cover, travel corridors, breeding spaces, and are especially important for amphibians such as newts.

The naturally regenerated alder in the background had come in after a harvest that had left little to no wood on the ground. The foreground will soon be planted back to conifers, which will take decades to reach a size that will provide a new source of snags or downed wood. By carrying over some downed wood like the log in the photo from one forest generation to the next, you can ensure some continuity of these wildlife-friendly habitat elements. Consider not disturbing down logs that are already in your forest – they are playing an important role, and besides, your equipment may take a beating if you try to move them or run them over!

Have you created or left snags or downed wood on your property? Do you have evidence of wildlife using these structures? I would like to create a photo gallery. Send me a photo of dead wood in your forest with a description of how it came to be or who you think is using it. If I get enough responses, I’ll share them all in a future article.

For more information on managing for wildlife, check out “Wildlife in Managed Forests: Oregon Forests as Habitat” published by the Oregon Forest Resources Institute. You can find it and many other publications about forest wildlife at KnowYourForest.org.

Amy Grotta

I recently got a call from a guy selling some woodland property in the Coast Range. A prospective buyer recently told him that he had Swiss needle cast (SNC) and so was not interested in buying the property. It is not hard to find the disease in western Oregon. It is a native disease of Douglas-fir and is wide spread from the coast into the Cascades. But this fellow was calling for some guidance about how to respond to this concern. Was it reasonable? How can he gauge its impact on his young forest stand?

Phot credit: SNC Coop

He already knows how to recognize SNC when he sees it: from a distance it makes a tree look paleand sparse. This is because the fungus is developing in the needles, gradually clogging the stomates, which is where the leaf exchanges water vapor, carbon dioxide and oxygen. Up close with a hand lens you can look on the underside of a diseased needle and see tiny black dots in neat rows where healthy white dots (the stomates) should be visible. In some places or during seasons when the disease is severe, this causes many needles to turn yellow, and eventually to drop (to cast), giving the recognizable symptoms. If enough stomates get plugged, and or enough needles are cast the disease begins to affect photosynthesis, and possibly growth, the crux of the caller’s question.

“The key to understanding the impacts from Swiss needle cast,” says Dave Shaw, OSU Extension Forest Health Specialist and Director of the SNC Cooperative, “is whether the needle retention on the tree is good or not. If the tree is retaining around 3 years of needles, then growth should be close to normal. The impacts occur when needle retention is below three years, and especially when it drops to 2 years or less.”

Photo Credit: SNC Coop

So, the question for the caller is: “What is your average needle retention in these stands?” If near 3 years, he can tell folks that yeah, the disease is around but the stand is doing ok.

To count needle retention, use binoculars and cruise the stand, taking the needle retention from the mid crown, south side of tree, and not the apical stem, but the 4-yr and older side branches. There is a good illustration of branching and needle cohorts on page 3 of Swiss needle cast of Douglas-fir in Oregon. This time of year is good. Even if the stand is discolored a little, needle retention is the key factor.

More information about SNC can be found on the SNC Cooperative website, which has aerial survey data, research findings and even a Stand Assessment Tool that provides a more quantitative approach to assessing impacts on growth.

Brad Withrow-Robinson

Feel like spring to you? It did to me earlier this week on a sunny walk in the woods. I spotted new leaves on many of our native shrubs, including Indian plum, huckleberry, elderberry, red flowering currant and salmonberry. These caught my attention particularly because I’ve just started dipping a toe in a new project – tracking phenology of a couple of our forest plant species through the National Phenology Network’s Nature’s Notebook.

Phenology? It is the timing of seasonal events in the life of a plant or animal. For plants, important phenological events include bud break, flowering, fruiting, or leaf drop. For animals, they are things like migration or egg hatch. These events have a predictable annual sequence that is tied to weather and climate patterns and ensures the survival of the species. Plants have adapted to their local environments such that they do not leaf out if they are likely to be damaged by frost; nectar-feeding insects’ life cycles are tied to the plants that they feed on.

Why phenology? Other than appreciating those first signs of spring, there are many practical ways that phenology ties into forest function and forest management. Here are a few examples that come to mind for me. Do you use herbicides around newly planted trees to control brush? Then you may monitor when your seedlings break and set buds so as not to chemically damage them. Do you rely on non-chemical methods of weed control such as mowing? Then you pay attention to when your target plants flower and set seed so that you can time your actions accordingly for best results. And, the timing of these events varies across the range of a particular plant species. That is why we have seed zones to ensure that when it comes to reforestation we “plant local”.

In the face of climate change, scientists are paying particular attention to phenology and interactions among species. For example, if due to an earlier spring, a nectar-feeding bird species begins to migrate earlier, but the phenology of a plant species in its summer range does not change, then the bird may not have a food source and the plant may not get pollinated.

Like tracking precipitation through CoCoRaHS, which I wrote about a few months back, tracking phenology is easy to do in your own woodland or even your own backyard. You choose a species from the many that are in the Nature’s Notebook database. You create an online account. Then you start observing your chosen species. This is another example of citizen science, where collectively the power of thousands of individuals gathering data can inform scientists and contribute to their research.

Oh yes…to the app. Nature’s Notebook has an App for Android and iPhone so that you can submit your observations right on your smartphone. How convenient! No need to remember to log into your computer when you get home. Just bring your phone out with you to the woods. I am using the app on my iPhone. It’s pretty basic, but it gets the job done.

Extension programs across the country are starting to adopt Nature’s Notebook with their volunteers. I’ve given some thought to this; hence my toe-dipping experiment. If you are a phenology tracker or become inspired to be one through this post, I’d love to hear from you. Comment on the blog, or send me an email.

Amy Grotta

Although a significant challenge, successful planting and establishment is of course only the first step towards restoring a forest. Moist tropical forests tend to have much higher tree species richness and diversity than do our temperate forests. While a forest in the Coast Range or Cascades of Oregon may have a dozen or so trees and shrubs (and is often dominated by just a few tree species) a similar area hill evergreen forest in Northern Thailand may have 100 to 150 species.
Replicating or recreating this diverse forest in one fell swoop at planting is impractical, or impossible. There are significant challenges of producing so many species in the nursery and also, many species seem poorly adapted to the harsh conditions of abandoned farm fields, and simply do not survive and prosper. Restoring a forest means restoring conditions and processes which in turn help create the forest.
After screening over 400 species, FORRU selected about 20 hardy species to plant as the “framework” for the future forest structure and processes. Species were selected according to their suitability to nursery production, survival and growth in abandoned field conditions, as well as to represent different growth forms and several successional stages. A great many of the selected framework species bear fruit, which is meant to encourage birds to visit the site in the hopes that they will carry in other native species. This is a key idea behind the framework species approach (adapted from Australia): along with changing the physical environment (light, leaf litter and organic matter) to favor establishment and survival of additional species, the planting needs to encourage mechanisms that deliver those species to the site. Initial findings are promising, with an increase in the number of birds and small mammals observed, and over 70 additional tree species recruited to the study plots.
But what will be the fate of those new seedlings? Does their presence today tell us what the future forest will be?
Most foresters and woodland owners in Oregon have seen a carpet of seedlings emerge on the forest floor following a thinning or other disturbance that lets more light reach the ground and maybe exposes some soil. Douglas-fir, grand fir, hemlock, alder and maple may all show up in abundance. Familiarity with our local species tell us that the fate of these seedlings is not the same. Douglas-fir generally will not grow to maturity in those conditions, while the hemlock or maple might.
Hathai (my graduate student) is trying to develop a similar understanding of the trees which make up the hill evergreen forests in Thailand. Her work on the regeneration dynamics of trees in the understory should help people here in Thailand have a better idea of the likely fate of the seedlings, and if their arrival heralds development of more complex and diverse forests in the future. Her work may also suggest ways to manage the plantings to best meet the restoration/management goals.

Brad Withrow-Robinson

If you have called or emailed me recently, you have received an “out of office” message saying I would be away in February. The full story is that I am in the mountains of Northern Thailand, helping my graduate student, Hathai, with her dissertation research on forest regeneration dynamics of understory trees. Her work is part of a bigger effort at Chiang Mai University (CMU) to study how to restore diverse, seasonally-dry tropical forests.
Thailand has lost over half its forest areas in the last 40 years to unsustainable timber harvest practices and land use conversion. In the mountains of Northern Thailand, most forest loss and degradation is driven by a history of shifting agriculture. Abandoned after farming, much of this land becomes dominated by aggressive invasive perennial weeds which prevent forest regeneration both by directly competing with seedlings and also by feeding widespread fires each dry season (March-May). These fires are not part of the natural fire regime, but are human-origin fires that kill many of the young seedlings getting established naturally, or as part of planting efforts. This favors and perpetuates the weed communities rather than native forests.
The Forest Restoration Research Unit (FORRU) at CMU has been working on this restoration challenge for the past two decades. The FORRU team began their work with basic research on local forest trees, studying life cycles, flowering and fruiting phenology. Likewise, they tackled challenges in nursery production by testing germination and nursery cultural requirements to help them grow and plant viable seedlings. All very much as was done in the Oregon four or five decades ago.
Success in the field came by both controlling the weeds in the plantations for several years after planting (no surprise to us in Oregon) and very importantly, through rigorous and on-going community-level fire suppression.

This work has paid off, and they have made great progress in learning how to begin to put forests back on the landscape.

Brad Withrow-Robinson

Planting trees is a central part of woodland ownership. For many folks, planting was the first thing they had to do upon buying cut-over land. For others, it is part of leaving things better than they found them, of leaving a legacy or creating opportunities for the next generation.

Planting is a critical step towards growing a new forest, whether you are reforesting a harvested unit, or converting pasture or other farm ground to a riparian buffer. But it is not the first step in the process. That began a year or more ago with a look at the ground to decide what to plant and how to prepare the site. It continued with the work done to be ready to plant, and will go on a few more years after the seedlings are in the ground. At each step, in each season, success comes from focusing on the task at hand.

I was reminded of this when I was out visiting Bob Feldman last month. Bob and his family tend about 350 acres of conifers, oak woodlands and Christmas trees in the Eola Hills northwest of Salem in Polk County.

We walked down the hill to a 6 acre clear cut he harvested last summer. Before the logger left with his equipment, Bob had him deck some logs for firewood and pile the excess slash for burning. The site looks great, ready to plant.

So now Bob is ready to go with his ground ready, 2-0 seedlings ordered and planting crew lined up. After picking them up from the nursery, he will store his seedlings in a local cooler, pulling out a day’s-worth at a time to keep them in the best condition possible.

Bob stressed the importance of lining up a good contractor, someone with experience and a record of success they can demonstrate. Be sure to oversee their work, establish accountability and to make sure they do a good job. How? Get out there with them. Spend a good part of the first day with them, and a little time each day after that. Make sure you have explained how you want the job done, and to show that you care that it is done right. Check to see that things are being planted at the agreed spacing. Dig up a few seedlings to see that they are planted correctly, snug, at the right depth and not J-rooted. Check across the planting crew, and bring concerns to the crew leader. When finished, go out and look to see if you got what you asked for.

Good advice. But what if you are the leader, and the crew is your family? Bob has lots of experience there too, and says if they are new to it, then you have to teach them how to do it right. Stay with them and supervise until they get the hang of it. If adults, they should be as interested is getting it done right as you. If kids, their interests are a bit more complicated. Be patient with kids. As important as it is, you are teaching them more than “green side up, brown side down.” You are teaching them how to grow a new forest.

Brad Withrow-Robinson