In recent entries in this series on the basics of herbicide use in weed control, I have reviewed how some foliar herbicides work, and the relationship between the plant’s physiology and the herbicides’ behavior. Now I want to illustrate how that that information translates to what gets done in the woods, looking at controlling blackberries, a frequent target of foliar herbicides.
Blackberries are a problem because they are widely dispersed by birds and start readily from seed and once established, rapidly spread vegetatively by tip rooting, quickly forming daunting patches seemingly too tall and wide to tackle. We’ve all seen these conditions in old pastures, riparian areas and struggling plantations. Continue reading →
In previous installments of this series on the basics of herbicide use in weed control, I distinguished between foliar and soil active herbicides, describing foliar herbicides as those applied to the leaves or stems of plants to be absorbed and carried throughout the plant to affect control. In the previous post I began discussing foliar herbicides in more detail with an overview of glyphosate.
In this entry I will look at a group of herbicides called “growth regulators” that include some important foliar herbicides and popular weed and brush killers commonly used in forestry, agriculture and habitat restoration. Continue reading →
In my previous installment of this series on the basics of herbicide use in weed control, I distinguished between foliar and soil active herbicides. In this post I begin discussing foliar herbicides in more detail. Note: The attention given to herbicides in this series does not indicate an advocacy for their use but an acknowledgement that using herbicides presents some unique risks, and that landowners and managers need to know enough about them to make informed decisions on their use.
Foliar herbicides are applied to the leaves or stems of plants to be absorbed and carried throughout the plant to affect control. They are common and widely used to control annual and perennial herbs and also woody shrubs. Continue reading →
Weed control is a top of mind topic now for many landowners. Following this spring’s strong log market, a lot of folks will be reforesting a harvest unit. Others may be planting a field of Christmas trees, or a swath of trees and shrubs as a restoration project to improve habitat conditions. And it seems everyone is struggling to control one invasive weed or another on the property.
While a number of approaches and strategies (including mowing, pulling and mulching) can and are used in managing weeds, many people will use herbicides as at least part of their approach. This is no surprise given their demonstrated effectiveness and efficiency. But not all users are well-versed in vegetation management, or the science behind it, so some review of herbicides seems to be in order. The attention given to herbicides in this and later articles does not indicate an advocacy for their use but an acknowledgement that using herbicides presents some unique risks, and that landowners and managers need to know enough about them to make informed decisions on their use.
Now, it is important to realize that one need not be a crop scientist to use herbicides. The label gives instructions that ensure the safe and allowable use of an herbicide, so the label needs to be read and followed. But responsible and effective use of herbicides requires some additional understanding about herbicides and how they work, as well as knowledge about the life cycle and other characteristics of both crop and target plant species they will be used with. Let’s begin talking about some basics. Continue reading →
Fire Season is now or soon will be in effect in much of the Tree Topics reading area, as declared by the State Forester according to regional fire conditions. So I got online to see what’s been declared. I went over to the ODF Wildfire website and clicked on Forest Restrictions and Closures section. There you can find links to an overview of the Industrial Fire Precaution Level (IFPL), closures and other information about fire regulations and restrictions. Continue reading →
Last week, we kicked off our Master Woodland Manager training in northwest Oregon. Over the next six months the class will explore many aspects of small woodlands management and the trainees will come away with a better understanding of their own lands as well as a foundation from which to assist others.
We started out with a field tour where we investigated the environmental factors that influence forest growth on a given site. In particular, we wanted to see how variations in climate, topography and soil shape species composition, forest productivity, and management opportunities.
We went to five different sites, at various elevations and topographic positions from the uplands to the Valley floor. Despite the sites all being within a four-mile radius, we saw striking differences in the vegetation. The uppermost site supported a fast-growing stand of Douglas-fir and red alder. Further along, we came upon a rocky, south-facing site dominated by madrone and some not-as-fast-growing Douglas-fir; but this was just a few hundred yards from another site where the madrone were gone. Calculating the site index revealed that the Douglas-fir here were growing faster.
As we traveled down the watershed, the steep slopes along an upland creek supported alder and western redcedar. But on the flats further down the watershed, at our last stop on the Valley floor, the dominant species were Oregon white oak, Oregon ash, and valley ponderosa pine; the Douglas-fir at this last stop looked like they had caught a bad case of the crud.
Prior to the field tour, we spent some time learning how to find information about soils. The Web Soil Survey is a really handy tool for identifying soil types and learning about their properties. Using the Web Soil Survey, we mapped out our field sites and found some possible clues to our site differences. According to our soils map, the madrone were growing on a gravelly Saum soil, whereas the taller firs down the road were on the more productive Jory soil.
A recently formed gully at the latter site gave us the opportunity to see the soil profile which revealed a deep silty clay loam.
Recently I’ve discovered SoilWeb, which has become one of my favorite natural resources-related mobile apps, available for both the iPhone and Android. Using your phone’s GPS capability, SoilWeb accesses the soil data from the Web Soil Survey for the soil right underneath your feet. That is, assuming A) that you are in a place where you can get a phone signal and B) that the soil maps accurately reflect the soil on your site. As we learned on our field trip, soil types as mapped often contain unmapped pockets of other soils. The SoilWeb app doesn’t give you everything you can find on Web Soil Survey, but you can quickly ascertain the soil texture as well as the expected depth, drainage, and other important features.
The takeaway from our tour was that what’s growing on your forest can be a clue to your site’s underlying environmental influences, and vice-versa. The growing number of applications such as SoilWeb makes it easier to be a site “sleuth”, finding those clues and piecing together the puzzle.
“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.
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.
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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.
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.
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?
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.”
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.
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.