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The Mystery – (and it is a sad one) – As shared in earlier posts, the Hyla Woods forests are experiencing a much accelerated rate of trees dying. Dead trees are an important part of a healthy forest, and we sometimes help things along by girdling trees to create snags. But in the past two years things have changed; once healthy and vibrant trees are dying – old ones, middle aged ones, and young ones. We’re not alone, and it seems that our mixed aged, mixed species forests are having less problems than the more monocultural forests nearby. When we ask the knowledgeable “..ologists” for their thoughts on the causes, we are given a one word answer – drought. Our Hyla Woods team thinks that the situation may be more complex than that; are we certain that the cause is drought? If it is drought, is there a chance that drought is the trigger, but that the causes might be more complex – soils, seed, disease, insects….?
While we can rise above the discovery that more 30 year old fir have died in some area of the forest, we experienced serious sadness when we discovered that a number of large, old, beautiful cedars in the wildest corner of Mt. Richmond Forest had no remaining green. The Red cedar on our “avenue of the giants” are taking on a new kind of red.
The Dilemma – How should we respond to these dead cedars? They have beautiful wood in them which we could put to good use. On the other hand, our forests are short on large, dead, downed wood that supports more life than the living tree ever did. Do the right thing? But what is the “right thing”?
A Decision – Team Hyla convened around the table and wrestled with the options. Our decision is that the best approach for us is to avoid the simplistic, “either-or” constraints and to instead try a compromise. Some of the dead cedar has been left on the forest floor where it is adding to the forest’s health. The rest of the wood from these recent casualties has been felled, bucked, and skidded to the landing where it awaits a ride from the tree taxi up to the mill. An up side of the increased mortality is that there seems to be enough dead wood to meet both goals – economic and ecological.
….And About That Bathroom – It seems fitting that at the same time as we’ve been wrestling with dead cedar and related decisions, these photos came in from a happy customer who gave one of our large, old, windthrown cedars a second life.
…and so the cycle continues – but let’s keep digging into the mystery; the forest challenges us to dig deeper.
“What’s the big deal about an Olive Sided Flycatcher?”
That’s a reasonable question.
It was answered in the course of this morning’s third and final annual bird count in our Mt. Richmond Forest. Here are a few of the reasons why we are excited to hear and see them:
- Inspiring Globe Crossers – Their long annual migrations – from as far south as Bolivia and on up to the arctic – are yet another reminder of how remarkable birds, and all of nature, are.
- They’re in Trouble – Of the birds that depend on Oregon’s Coast Range forests, they’re one of the four species that are in steepest decline. Much of this decline is driven by habitat loss.
- They’re Here – We’re pleased that the Hyla Woods forests provide reliable safe haven for these remarkable and stressed birds.
- They’re Increasing – In Our Forests – Reviewing data from our more than 15 years of careful, annual counts, we can see that that we’re successfully bucking the trend; while they decline in our region, they are on the increase in our forests. Who knows why? Our habitat is improving? Habitat in surrounding forest in other forests in the regions deteriorating? Perhaps both? We all benefit when steps to arrest their decline are successful. Their presence and increase validate that we may be working in the right direction.
- We Need and Value Then – Flycatchers, as their name reflects, depend on eating insects – lots of them! Insects help keep forests healthy, but, when out of balance, they can become a threat to forest health. These winged insect eaters help maintain necessary balance. We work for them – they work for us.
As we hang up the binos, clipboards, and stop watch at the end of yet another yearly round of bird counts, we enthusiastically raise a glass to thank and toast these remarkable birds.
Thanks also go to our remarkable, reliable, and long suffering expert birders – Char Corkran and Lori Hennings.
Visitors to our forests often ask why we work on growing forests that are multiple ages and many species. “Wouldn’t it be easier and more profitable to just grow single age, single species plantations like nearly all of your neighbors do?”. While we have many reasons for using the approaches we do – some of them scientifically based and other driven more by gut instinct – the question raised is a good one. Because of this, it is something that we always work on learning more about. As people who feel that we have a responsibility to maintain and rebuild the public values of our forests and believe that the long term profitability and health of our forests is more important than the short term, we think that avoiding the risks of the plantation approach makes good, pragmatic business sense. At the same time, we work to be disciplined in always questioning the assumptions that our approaches are based on – “what if we’re wrong?”.
Which brings us to the value of learning. We’re prompted to share these thoughts just now because of two research publications that we’ve run into in recent months. Both appear to shine light on the risks and down sides of the plantation approach that dominates our landscape in western Oregon. Though we are told that plantation silvaculture is what the prudent investor does, we question whether that conclusion is a valid one.
The first piece of research, done by scientists at Oregon State University, explores the negative impact of plantation forestry on summer stream flows. We encourage you to check it out and are happy to provide copies of the paper. Unfortunately it does not appear to be available online.
The second paper suggests that, in some circumstance trees, grow better in mixed species stands rather than in single species stands. This link provides a newspaper style report:
Here is a link to the paper: http://www.nature.com/articles/s41559-016-0063.
Because we find both of these studies to be helpful and interesting, even if not definitive, we think you may as well.
The learning continues – and that is one of the rewards of forest stewardship.
I discovered something that was really uplifting and surprising yesterday.
At day’s end I traveled back through the Mt. Richmond Forest with a sense of satisfaction – and fatigue – from having planted the last of the 2,200 seedlings that we’ve planted this winter.
Pausing by the “Beaver Pond” wetland I reflected on how different it feels to visit the spot since all of the resident beaver mysteriously disappeared from the pond and forest about five years ago. Though we have hypothesis, the puzzle of the cause remains unsolved. Reflecting on this sadness I somehow decided to dismount from my “iron pony” and hobble over to where the stream flows out of the pond. Drawing closer, something caught my eye – “isn’t that a low dam blocking the outlet – with freshly cut, green reeds woven into the sticks? Could it be…..?”
A closer look persuaded me that nothing could have made this – other than a beaver. Looking further around the wetland my conclusion was verified by finding this….
After five years of lamenting the loss and considering options for reintroduction, the problem has solved itself. What is remarkable is that this beaver (could there be 2?!) had to cross some seriously inhospitable terrain. From the nearest beaver habitat in the Tualatin River, it had to navigate roughly a mile of open, unvegetated ditch through industrial farmland, climb up a steep stream through pastureland, and find its way through another half mile of forestland that we recently bought from the neighbors. Go Beevs!
Perhaps I shouldn’t be, but I am surprised by how much my winter weary spirits have been lifted by discovering that the forest’s wetland habitat is once again home to a beaver – and that the “Beaver Pond” once again deserves its name.
Barak Obama’s forecast that the sun would rise on the day after the election verified, yet on November 9th as I looked east from the top of Mt. Richmond Forest over the folding ridges, valleys, wetlands, and hills of the Tualatin Valley toward the rising sun, I realized that while the familiar landscape looked unchanged – it felt very different.
Just as I know and value this place’s ecological diversity, I also appreciate the healthy political diversity of my neighbors. The success of our forest business and the experiments that we explore depends on many dimensions of this landscape. Uncertainty goes with the territory – for both better and worse – but the rising sun of November 9th illuminated a place with many new uncertainties and fewer certainties.
Culture – Like many businesses, our forests depend on the hard, careful work of recent immigrants; will their new fears be realized or will we find ways to help them feel welcomed, valued and appreciated?
Ecology – In this landscape that has been transformed in so many ways to suit the needs of humans, and where we and others work together to rebuild the land’s health and wealth, will federal laws like the Endangered Species Act and the Clean Water Act continue to advance this process?
Climate, Atmospheric – Human driven climate change is already impacting our forests’ health; what impact will the newly elected have on our ability to change course on climate alteration before it is too late?
Climate, Human – Our years in this valley have shown us how kind, respectful, honest, and good hearted so many of our neighbors are; how will this fair in a national environment shaped by a president and his followers who consistently demonstrate hate, intolerance, fear, and intellectual dishonesty?
This election rocks the world that we and our businesses work within. How should we respond? It seems that we should respond in at least two ways:
- As prudent business owners and as citizens we should be ready and willing to stand up and fight for those things that are important to us, and
- We should apply the lessons taught by the forest by taking the long view.
Our forests are increasingly islands surrounded by a sea of young plantations whose owners normally clear cut their trees when that reach the age of forty years that is considered to be “economic maturity”. The November 9th rising sun shines on a land whose ecology and human culture both run long and deep. We’re reminded of this by the eyes of the pictographs that have looked out from the cliffs across the valley for many thousands of years. The photo below and the huge stumps in our forest reminds us that while elections may get us worked up and amplify uncertainties we’re just ignorant newcomers flopping around in a place with a deep, long and remarkable past. The photo, taken on the central Oregon coast, just over the hill from Mt. Richmond, shows the stump of a tree that was cut in the 1920s and sprouted in 580 BC intertwined with and nourished by a tree that sprouted in roughly 2600 BC.
Yes, it is in our business interest to pay attention and resist changes that threaten our interests – but our forests also teach us the wisdom of taking the long view.
(Editor’s Note – The Hyla Woods Team is thrilled to have an ongoing partnership with the 7th grade students and faculty from Catlin Gabel School in Portland. Each year, with the excellent leadership of their teacher, Jesse Lowes, and other adults, the students do important and useful scientific investigations in the forests. The report below is just one of the many summary reports that the students have produced. The class cooperatively made the decision that Hannah’s report would be shared. We thank all involved for their hard and careful work.)
Into the Woods – A Report on a Scientific Investigation:
By Hannah Renee Langer
It was drizzling. The skies looked overcast and positively cranky, clouds bumbling about and bumping against each other grumpily. We all stood underneath the awning outside of the gym, bundled up in rain jackets. Though the benefits of tromping in the soggy forest for hours may not have been immediately discernible, we all knew that the environment – and us, to a certain extent – would greatly profit from our hard work and the extensive evaluation we did on the water quality of a little creek in the Coast Range.
We, one of the four science classes that make up 65 students total, were about to board a school bus to leave for Hyla Woods, an experimental forest plopped down right in the middle of Oregon. Tall trees of all different sorts reached towards the sky, awe-inducing, like decorated church spires. The moment I stepped off the bus and took a deep lungful of the crisp autumn air, I knew this environment was nothing like the one I was living in. Hyla Woods had a certain quality about it that made everything about it seem even more enchanting: the assorted bird calls that echoed throughout the treetops mournfully, the feeling of a soft pad of moss underneath the sole of my rubber boots, and the simple quiet of the place. Almost immediately after arriving, we all stood in a circle, closed our eyes, and simply focused on the noises of the forest. Instead of hearing construction, cars whirring by, and the busy hubbub of the city that we had just tuned out and accepted as everyday white noise, we were exposed to a magical forest almost out of a storybook where birds gossiped, a distant creek burbled, and stray raindrops hit the ground, twirling and falling helplessly from the verdant boughs of nearby trees and rich vegetation.
At this forest, we tracked the question “How can we tell if an ecosystem is healthy?” and did so by investigating the stream that sauntered through the forest, Louisignont Creek. We completed many tests on the water quality of the stream, including an inventory of the organisms that were folded inside of the stray leaf packs that were scattered and rooted in the silt. Though I wasn’t used to getting mud everywhere (everywhere, I tell you!) and shielding myself from the drizzling rain for hours on end, while I was there, in the moment, I felt like I was completing important work – and I was!
This important work was completed over two days in October and November. To ensure that our evidence and findings were meaningful, there were 12 research sites in total that different groups worked at along the bank of the creek. Our topic question, how can we tell if an ecosystem is healthy?, is very important because we live in one! It’s very important to know how to tell whether an ecosystem is healthy or not, and how to improve and measure that health, because this information is necessary in order to take care of the big, wet rocky sphere we inhabit.
While visiting Hyla Woods, we conducted tests on the creek that bubbled through the woods. We tested the temperature of the water, as well as the pH of the water, the amount of dissolved oxygen (DO) in the water, and the turbidity (cloudiness) of the water. A good water temperature for Northwest aquatic life is 5-15 degrees Celsius, and the class of 2020 tested the water to be 11 degrees, which is perfect! The air temperature was also around 11 degrees Celsius that day. If the water temperature was too hot, some organisms would not be able to thrive in the environment, and it’d throw the whole food web out of whack! The optimal pH range is 6.5-8.3, and our class measured the pH to be 6.7 (the average from 12 research sites over two days), which means there’s a healthy pH value in the stream. If the pH value weren’t in this optimal range, however, it may impair the vision of fish or prevent fish eggs from hatching. The DO (dissolved oxygen) range that is most suitable for Northwest aquatic life is at least 8-12 ppm (parts per million), and our class measured the DO to be 9.1 ppm, suggesting that the stream is right in the ‘healthy’ range. If the DO was lower, the water may not be suitable to the organisms, because they may not be able to breathe in water with less dissolved oxygen. Finally, our class measured the turbidity (cloudiness) of the water to be 10 NTUs (Nephelometric Turbidity Units), which is healthy! To find this information, we filled a tube with water from the creek until we couldn’t see the bottom anymore. Many groups kept filling it until it overflowed, and they were still able to see the bottom of the tube, meaning the water was very clear. 10 NTUs means that the water isn’t so cloudy that it disrupts the organisms or their homes.
After testing the water, we planted an artificial leaf pack. Leaf packs are natural clumps of leaves that form in streams and act as perfect homes for assorted aquatic macroinvertebrates, tiny little creatures that dwell in ecosystems like the stream we investigated at Hyla woods. Some examples of these are caddisflies, midges, and aquatic sow bugs. Based on how sensitive the organisms we discovered living in our leaf packs were, we could then determine whether or not the ecosystem was healthy. For example, if many sensitive macroinvertebrates like alderflies and mayflies are living in the stream and thriving, it means the stream is healthy. But, if there are many tolerant species living in the leaf packs like leeches or midges and not many sensitive species, it means the stream is somewhat or very unhealthy. To efficiently measure the amount of sensitive and tolerant species living in our leaf packs, we plugged the species we discovered at all twelve sites into an equation and came out with a number, the Biotic Index, that we could then use to judge the healthiness of the stream. Our class average for the Biotic Index was 3.76. This data comes from the artificial leaf packs we placed, but some leaf packs were either lost or compromised. This means the water quality was good (nearly excellent) because the range for excellent water quality is 3.75 or more.
From what I’ve learned, I’ve come to the conclusion that a healthy ecosystem is an ecosystem that is balanced and thriving. A healthy ecosystem should be filled with many different organisms that work together synergistically to support their environment. In class, we studied food webs, which perfectly sums up invertebrates in an environment and how they all connect and help each other out. We also interviewed different people in our lives outside of school, asking them about what they considered a healthy ecosystem to be. My mom pointed out the fact that an ecosystem should be rooted and connected, sometimes so much so that when one piece falls from the puzzle, the whole construction collapses. Ecosystems should be tightly woven, like a quilt made up of a wide plethora of different kinds of organisms. After completing many tests on the water quality and examining the organisms that live in the Louisignont creek, this year’s Catlin Gabel 7th graders have come to the conclusion that Hyla Woods continues to be a healthy, thriving ecosystem.
Talk of “divides” is all around us. Red/Blue, Urban/Rural, Rich/Poor, White/Brown…..
Of course it’s not new, but it seems to be more acute than at any other time in my brief sixty years. There seems to be agreement that is a problem deserving of our attention, which leads to the good question of “how”?
The Hyla Woods team thinks and cares about this issue and question. One answer that we’ve focused on seems simple and manageable – reach across a divide and find some reason to work together. It’s not rocket science – (or far more complex, ecosystem science) – but many drops of water do turn the mill. Here are examples of what we’ve done and learned by doing this.
We’ve identified products that grow in our forests that urban people need and we have provided them. Many years ago, thanks to a “block party” organized by our friends at Ecotrust, we met and visited with Christine and Robert. They’re both retired from interesting lives as members of religious orders, live in SE Portland and – most importantly – want a load of firewood each fall. They don’t want just any wood; they want wood from what feel is a well cared for forest. In addition to the “cord in the Ford” making the drop off each fall, we connect with them in other ways. They enjoy honoring the salmon that return to the forest each year and are always asking for updates on the ups and downs of life in the forests. With each passing year and interaction, we come to know one another – and the realities we live in – better.
We know that our main logging contractor (logger!) holds strong political opinions that are very different from our own. The day after the election I (peter) sent Brandon an invitation asking whether he would like to get together for a conversation over a greasy breakfast. Our getting together started with him smiling and declaring “I like food” and ended with us each understanding one another better and agreeing that the things we share in common and agree on are more important and powerful than the things we part company on. In between we discussed our hopes and fears for our country, our families, our local communities, and our businesses. Because we need him and he needs us, we look forward to continuing to work together. With hash browns and eggs in our bellies, he headed off to trouble shoot a blown hydraulic line on his loader and I set out to try to fix our sawmill.
Forests certainly do not heal all things, but they can help.
Do you remember encountering, at some point in your school, a lesson in tipping points? Phenomena the may change at a slow, regular and predictable point but then cross a threshold, or tipping point, when they can change dramatically and rapidly? I do. Images of the concept stick with me; I think of it as I read news of melting ice in the polar regions or the prospect of the Gulf Stream radically shifting. Those of us owned by forests think about these things in the early morning hours. Over the past two year’s the concept has been brought home, literally, and made real as we watch the impacts of recent drought on portions of our forests. In our areas of mid aged Douglas fir, we are accustomed to watching some trees vibrantly thrive while others sputter along with less vigor. We know that these differences may be caused by many things – soils, available moisture, seed source……. But until recently, experience always taught us that change in the condition of the underdog trees would be gradual and predictable. Now that has changed. A tipping point threshold was crossed and in several parts of the forests we have significant areas where, in the period of one or two years, 20 to 60 year old trees have begun dying – not gradually, but in the course of one or two years. As the theory has been brought home in the shape of brown and falling needles, curling, dry bark and falling trees we now must answer the question of “now what?” While we assume that many factors may work together to create the problem, it seems probably that drought pushed these trees across the tipping point threshold. Is the drought a consequence of human caused climate change? Will we ever know for certain? Regardless, these dead trees in their even aged, monoculture plantations reminded us of something we already knew – that a forest that is diverse in age and species is better suited to a changing world than one that is less diverse. Applying this lesson in tipping points, on all scales seems important. Right Donald?!
This blog was born out of a teacher asking “wouldn’t it be great if we had some way to better learn about what other educators and their students are doing in the Hyla Woods forests?”. Of course, those of us on the Hyla Woods team responded with two things: 1) an enthusiastic “yes!”, and 2) a this blog.
Five years and many posts later, the experiment has been a success and the blog provides an ever evolving and growing compendium chronicling the good work done in the forests – by students of all types.
In keeping with that spirit, we encourage you to read this recently published piece by Catlin Gabel School second grade teachers Natanya Biskar and Laura Morton summarizing their students’ explorations and discoveries in the Timber Forest. It is particularly exciting to see how this work fits into both the yearlong work of the second grade as well as the school’s overarching educational philosophy.
Effects of Management Practices on Avian Abundance in Oregon Coast Range Forests
Advisor: Delbert Hutchison
Forestry in Oregon has traditionally used an industrial model aimed to maximize timber production and revenue, with little attention to the potentially negative affects on ecosystem health and biological diversity. However, some landowners have begun experimenting with more sustainable management practices. This study examines the affect of some of these innovative silvicultural techniques on avian abundance and diversity in the Oregon Coast Range. Data on bird number and species were collected across designated stops for three years with each stop characterized by forest type (predominantly Douglas fir, mixed, or predominantly a species other than Douglas fir), understory (woody shrub, fern, or herbaceous), and treatment (control, lightly thinned, thinned, or patch cut). Total number of birds, number of birds in certain foraging guilds, and four indicator songbird species were compared across stops. Because data were collected with no clear analysis in mind, not all combinations of stop characteristics could be considered. Data were analyzed using one and two-way ANOVA, and results were corrected using the Bonferroni correction. While no significant results were found related to forest type or understory, birds clearly preferred the lightly thinned treatment. Studies analyzing all combinations of forest characteristics and comparing sustainably managed forests to industry methods should be implemented to more thoroughly answer the question of what management practices maximize forest ecosystem health.
Commercial forestry has remained a predominant use of forestland in Oregon since the mid-1800s (Oregon Forest Resources Institute 2013). Forests cover about half of Oregon, and roughly 80% of that forestland supports growth of commercial-grade timber. The vast majority of management of working forests in Oregon uses an industrial model aimed to maximize timber production and revenue, with little attention to the potentially negative effects on ecosystem health and biological diversity (Jones et al. 2012, Oregon Forest Resources Institute 2013). Industrial forest management uses a rotational monoculture crop system, heavy application of herbicides, and large clear cuts to maximize production of Douglas fir, the main commercial forestry crop in the Northwest (Oregon wild 2012). A focus on maximizing production and profit has led to a decrease in structurally complex and biologically diverse ecosystems. With most of Oregon’s working forestland managed in this unsustainable way, old growth forest is one of the few ecologically healthy forest types remaining. With old growth in Oregon diminishing from 14.2 million acres in 1935 to only 4.9 million acres in 1992 (Bolsinger 2011), finding new ways to mindfully manage Oregon’s forestlands to maintain and create ecological complexity and vitality is essential.
Some Oregon landowners have begun to shift their focus from maximum wood production and economic gain to a model aimed to enhance ecosystem health while still supporting an economically viable business (Thomas et al. 2006). While these changes have primarily taken place on private lands with owners who feel a responsibility to manage their properties sustainably, in response to public pressure these innovative silvacultural techniques are beginning to be implemented on public lands that have been managed in a more traditional, industrial way in the past (Franklin and Johnson 2013). However, these changes in management on public land are recent and small-scale. For example, recent legislation has mandated that the O&C lands, approximately 2.4 million acres of forestland in western Oregon that was reclaimed from the Oregon & California Railroad by the Federal Government in 1916 and has been heavily logged ever since, will be managed using a variable retention method (Association of O&C Counties 2008, Franklin and Johnson 2013). Variable retention harvesting, a method modeled on natural patterns of disturbance, may help to maintain and rebuild healthy ecosystem functioning (Franklin and Johnson 2013). This recent shift in focus has led to management practices focused on diversifying forests in terms of age and species in order to support ecosystem health and biodiversity (Davis et al. 2007, Davis et al. 2009, Muir et al. 2002). These new management practices often include stand thinning, limited herbicide use, and encouragement of variation in forest species and age composition, all of which are beneficial in that they support ecosystem health and biodiversity (Betts et al. 2013, Cahall et al. 2013, Hagar et al. 2004, Linden et al. 2012, Yegorova et al. 2013).
Birds, and specifically songbirds, function as indicators of ecosystem health due to their close associations with vegetation (Yegorova et al. 2013). These relationships between bird species and density and vegetation may function and be apparent in a variety of different ways. For example, certain species have been identified as especially good indicators due to their reliance on certain understory types for breeding habitat, the destruction of which is associated with declining bird populations (Canterbury et al. 2000, Stephens et al. 2011). Studies in forests of the Oregon Coast Range support the hypothesis that industrial practices including clear cutting, heavy herbicide use, and single age monoculture rotation, negatively affect avian abundance as compared to more varied and ecologically minded management techniques. For example, thinned, as opposed to unthinned, regeneration after clearcut promotes avian diversity (Cahall et al. 2013, Hagar et al. 2004, Hagar et al. 2009): changes in vegetation caused by thinning may mediate post-thinning bird response by affecting food sources such as invertebrate insects as well as nesting habitat for local birds (Hagar et al. 2012, Yegorova et al. 2013). Some have argued that recently clearcut areas may play an important role in initiating forest succession, an ecological process that provides diverse habitat to bird populations (Bosakowski 1997). However large clearcuts are highly destructive and may harm cavity nesting species as well as other birds that depend on trees and thick underbrush (Mahon et al. 2008). Clearcuts also vary in their value as avian habitat based on the amount of woody debris and snags retained (Bosakowski 1997). Herbicides applied in amounts typical of industrial forestry practices also negatively impact avian abundance as compared to sites with light or no herbicide application (Betts et al. 2013); while thinning promotes understory vegetation favorable to many bird species, herbicide use reduces understory vegetation (Betts et al. 2013, Hansen et al. 1995). Additionally, stand complexity in terms of tree age and species promotes avian diversity, while single-age monocultures significantly reduce avian diversity (Felton et al. 2011).
Located in the Oregon Coast Range, the owners of the family-owned and managed forestry business Hyla Woods have managed their forestlands to promote ecosystem health and biological diversity since 1986 (Hayes and Hayes 2013). Hyla Woods owns 825 acres divided between three locations in the Northern Oregon Coast Range: Manning (100 acres), Timber (173 acres), and Mt. Richmond (552 acres) (Fig. 1 – 4). Their management practices include varied thinning and patch cutting with a maximum clearcut size of two acres, limited, point specific herbicide use, and encouragement of multi-age, multi-species tree communities. Since 1986, the managers of Hyla Woods have worked to better understand the ecosystem functioning of their forestland through a variety of monitoring regimes. Through data collection and analysis they hope to answer three central questions: “what is the status of the health of these forests?; how is it changing over time?; and what can we understand about the causes of these changes, particularly the impacts of our actions on these changes?” (Hayes and Hayes 2012). Available data sets include water temperature, aquatic invertebrates, juvenile fish, spawning salmon, birds, owls, terrestrial amphibians, aquatic amphibians, large mammals, trees, and oak habitat. All data collection followed set protocols, but with no specific analysis in mind.
Because birds function as indicators for overall ecosystem health, and given the robust and long time-term nature of the Hyla Woods data set on birds, I used the bird data set to examine the relationship between forest treatment (unthinned, lightly thinned, thinned, or patch cut), understory, and forest health (Yegorova et al. 2013) as defined by the number and diversity of species supported by a given area. Due to the challenging nature of detecting trends in data collected with no clear study design, as was done in this project, one lesson from this analysis is the importance of clearly outlining study objectives and specific statistical analyses before beginning data collection.
Materials and Methods
Data were collected from three non-contiguous pieces of forestland (Timber, Manning, and Mt. Richmond sites), all within the western hemlock zone and between 400’ and 1200’ in elevation (Fig. 1). The three study areas consisted of predominantly Douglas fir ranging in age from recently planted to around 200 years old, and also contained a variety of other tree species including big leaf maple, western red cedar, grand fir, red alder, and Oregon white oak. The owners manage all three areas to promote biodiversity through a variety of harvest techniques
(thinning and patch-cutting), very limited herbicide use (spot treatments only), and encouragement of multi-age as well as multi-species tree communities.
At each forest, trails were created with multiple “stops” where data were collected. Bird and vegetation data were collected from 14 stops at Timber, 10 stops at Manning, and 24 stops at Mt. Richmond (Fig. 2-4). Three factors influenced stop determination. First, the combination of the stops at each separate forest is representative of the variation in that forest in terms of age, species, and understory; the owners tried to create enough stops to sample as many combinations of these variables as possible. Second, the route between stops must be accessible by foot on roads, trails, and skid trails. Lastly, stops were as evenly spaces as possible, while taking into account the first two considerations. Because of the size, shape, and accessibility of Mt Richmond, data collection occurred on two routes with 12 stops each (Fig. 4).
At each forest, observers trained in bird identification by sight and sound collected bird data at all stops for three consecutive years: at Manning from 2007 through 2009, at Timber from 2010 through 2012, and at Mt. Richmond in 2013 only. Data collection at Mt. Richmond will continue in 2014 and 2015. Yearly, observers recorded data at each stop on three days, each approximately a week apart during late May and early June. Observers did not collect data on days with rain or strong wind. Observers began walking the loop at 5:00 am (around first light). Once reaching a stop, they stood silently for approximately one minute before beginning a three minute period in which they recorded the species and abundance of all birds detected by sight or sound. Observers followed this point-count protocol at all stops and finished the route between 7:00 and 7:30 am (Huff et al. 2000).
Habitat data were collected once in 2013 at all stops at Timber, Manning, and Mt. Richmond. At each stop four subplots were sampled, each with a radius of ten meters, and located a randomly determined distance between ten and 50 meters directly north, east, south, and west of the stop center. An ocular estimate of percent vegetation cover within the categories woody shrubs, ferns, and herbaceous species at two height classes (<1.5 m and >1.5 m) for each subplot was also made.
Due to the varied species, understory, and treatment history between stops, each stop was generalized into categories of “forest type”, “understory” and “treatment”. Forest type was determined by summing the numbers of individual trees in distinct species across the four subplots. Based on total number of trees of each species, each stop was classified as predominantly Douglas fir, mixed, predominantly a species other than Douglas fir, or no trees. A stop was considered predominantly a single species if half again more of one species was present than other species. To determine the majority understory present at each stop, ocular estimates for three categories (woody shrub, fern, and herbaceous) were summed across the four subplots. Each stop was then classified within one of these three understory categories based on the most common understory type. Finally, stops were characterized by treatment groups as control (unthinned), lightly thinned, thinned, or patch cut. A number of stops contained variation between the four subplots and therefore received two treatment categories.
Data on bird species and total numbers collected across years on the three observation days within each year for each stop were summed and then standardized assuming nine total stops in order to make all stops comparable. Bird species were then divided into foraging guilds and the total number of birds was calculated in each of seven foraging guilds, taking into consideration the standardized totals. Bird species were divided as classified by Bryce’s guild system (Bryce 2006), and those not included in this guild system were assigned based on their foraging habits (Poole 2005, Sibley 2003, Wilson 1999). Foraging guilds included ground gleaner (GG), foliage gleaner (FG), bark gleaner (BG), hawker (HA), hover feeder (HOV), aerial feeder (AER), and aerial patrol (AP). In addition to grouping species into guilds, four songbird species, Macgillivray’s warbler (MGWA), orange-crowned warbler (OCWA), Swainson’s thrush (SWTH), and Wilson’s warbler (WIWA), known as especially good indicators for forest biodiversity and health (Stephens et al. 2011) were used to analyze songbird association across forest type, understory, and treatment.
Although the three areas were studied at different times, their similarities in region, management, and community composition across the three forests meant they could be combined into one data set for analysis. Thus, when combined across forests the bird and habitat data sets included 48 stops. Because the data were collected without any specific analytical techniques in mind, there are gaps in sampling which limit statistical analyses. However, it was possible to “mine” the data for suitable combinations of variables that did lend themselves to one- and two-way ANOVAs (Rstudio, Minitab).
The unbalanced design of this study limited the number and type of possible statistical analyses. With the data available the effect of forest type, understory, and treatment on total number of birds, numbers of specific indicator species, and prevalence of guild types was analyzed. Data for all combinations of factors (forest type, understory, and treatment) were not available, and therefore results are specific to certain groupings of stand characteristics. Because twenty-two statistical tests were performed, alpha values were corrected using the Bonferroni correction (Rice 1989) to account for the fact that at an alpha level of 0.05, and given twenty-two tests, statistically one test would be expected to yield falsely positive results.
All results were deemed significant by the Bonferroni correction unless otherwise indicated by the appropriate p-value.
Using a one-way ANOVA, total number of birds was compared across three forest types (predominantly mixed, predominantly Douglas fir, and predominantly a species other than Douglas fir) at stops with herbaceous understory. At an alpha level of 0.10, the mean number of birds found in stands with a predominantly Douglas fir forest type with herbaceous understory was significantly higher than the mean number of birds found in mixed species stands with herbaceous understory (F = 49.85, d.f. = 1, p = 0.09, r2 = 6.32, Fig. 5). Total number of birds was also compared across the three forest types (predominantly mixed, predominantly Douglas fir, and predominantly a species other than Douglas fir) at stops with herbaceous understory and a control treatment. Although the results were not significant, a graphical representation shows a trend in which bird number was highest in stands with a predominantly Douglas fir forest type, followed by mixed stands, and lowest in stands with no trees (Fig. 6).
Using a two-way ANOVA, total birds were compared across forest types by treatment at stops with herbaceous understory. Two-way ANOVA was used to compare total number of birds designated as a combination of the foraging groups ground gleaner and foliage gleaner across the three forest types (predominantly Douglas fir, mixed, and predominantly a species other than Douglas fir) at stops with herbaceous understory, but no significant results were found. Finally, total birds were compared across forest types at stops with herbaceous understory with the foraging guilds ground gleaners and foliage gleaners evaluated separately. No significant results were found for any of these tests. Given available data, no other statistical tests were possible using the variable forest type.
Using one-way ANOVA, total number of birds was compared between stops with woody shrub and herbaceous understory in stands with a predominantly Douglas fir forest type. No significant results were found. A series of one-way ANOVAs were used to analyze the distribution of four indicator species (MacGillivray’s warbler, orange-crowned warbler, Swainson’s thrush, and Wilson’s warbler) across understory types. None of these indicator species were significantly more prevalent in one understory type over another.
Sufficient data were available to perform a one-way ANOVA of total birds summed across the four indicator species across all four treatments (control, lightly thinned, thinned, and patch cut). The total number of birds was significantly higher in lightly thinned stands (an intermediate between control and patch cut) than in control, thinned, or patch cut stands (F = 5.96, d.f. = 3, p = 0.001, r2 = 59.97, Fig. 7). Using one-way ANOVA, total number of birds was compared between the treatments thinned and patch cut in stands with a predominantly Douglas fir forest type. No significant results were found. Total number of birds was also compared between control and thinned stands at stops with herbaceous understory and a predominantly Douglas fir or mixed forest type, as well as across treatments at stops with a predominantly Douglas fir forest type and herbaceous understory. Neither test delivered significant results. Two-way ANOVA was used to compare total birds between thinned and patch cut treatments by understory (only including woody shrub and herbaceous) in stands with a predominantly Douglas fir forest type. While no significant results were found, the graphical representation of total birds across treatment and understory in stands with a predominantly Douglas fir forest type revealed a striking interaction effect in which herbaceous understory was most common in patch cut stands and least common in thinned stands (Fig. 9).
Two-way ANOVA was used to compare total birds across treatments by the four indicator bird species. There was an interaction effect in which the summed number of birds across all indicator species (but especially orange-crowned warblers and Swainson’s thrushes) was higher in lightly thinned stands than in control, thinned, or patch cut stands (F = 2.06, d.f. = 9, p = 0.035, r2 = 59.97, Fig. 11). A series of one-way ANOVAs were used to determine the distribution of the four indicator bird species across treatments. Orange-crowned warblers were present in significantly higher numbers in lightly thinned stands than in control, thinned, or patch cut stands (F = 9.09, d.f. = 3, p < 0.0001, r2 = 38.26, Fig. 8), while the other three indicator species did not vary significantly across treatments.
Total number of birds was compared between the foraging guilds ground gleaners and foliage gleaners at stops with herbaceous understory, as well as across the four indicator species, using a series of one-way ANOVAs. There were significantly more birds in the foliage gleaner group than in the ground gleaner group across all stops (F = 195.23, d.f. = 1, p < 0.0001, r2 = 67.50, Fig. 10). The number of birds also varied significantly between indicator species with significantly more MacGillivray’s warblers than orange-crowned warblers, and significantly more orange-crowned warblers than Swainson’s thrushes and Wilson’s warblers (F = 48.13, d.f. = 3, p < 0.0001, r2 = 59.57, Fig. 11).
Overall bird numbers were higher in stands with a predominantly Douglas fir forest type and herbaceous understory than in mixed stands with an herbaceous understory (not significant under the Bonferroni correction). This result was counter to expectations that more birds would be found in mixed stands due to the wider variety of habitat and availability of associated niches (Molles 2008). This pattern of more birds in Douglas fir stands than mixed stands may have differed in stands with a fern or woody shrub understory type. When comparing total number of birds across forest type at stops with an herbaceous understory and control treatment the results were not significant, however the overall trend suggests that bird density is highest in predominantly Douglas fir stands, followed by mixed, with lowest bird density in stands with no trees. This trend agrees with the results found when comparing total bird number between predominantly Douglas fir and mixed stands with an herbaceous understory.
No significant results were found when using understory as the independent variable. Due to data limitations, a comparison between understory types within all forest types and treatments was not possible. Performing more tests using understory may have produced more significant results.
When the total number of birds was summed across the four indicator species and compared across treatments, more birds were present in lightly thinned stands than in control, thinned, or patch cut stands. Additionally more orange-crowned warblers were found in lightly thinned stands than in control, thinned, or patch cut stands. These differences in bird density between treatments may result from available nesting habitat, prevalence of certain types of understory, or the amount of bare ground or open space (Parrish and Hepinstall-Cymerman 2012). Because birds appear to prefer lightly thinned stands to other treatments, the majority of birds likely forage in vegetation associated with lightly thinned stands and do not require the open space provided by patch cut stands.
A non-significant trend suggests that herbaceous understory is most common in patch cut stands and least common in thinned stands. While data were not available to determine the most common understory type in lightly thinned stands, it may be extrapolated that lightly thinned stands either have more fern or woody shrub understory types or more bare ground. The association between bird number and treatment is clearly visible in the higher density of birds in lightly thinned stands than stands with other treatments, and is likely explainable by the association between understory and treatment. Sufficient data were not available to accurately analyze this connection. These results on bird distribution across treatments do not include an analysis of species distribution beyond looking into foraging guilds and four specific indicator species. Analyzing species distribution would be valuable in determining whether the trends apparent in this study result from many individuals belonging to a small number of species or fewer individuals belonging to many species. While light thinning may be the best harvest method for the greatest number of birds, light thinning may not promote species diversity because certain species may rely on habitat not available in lightly thinned stands.
Comparing total number of birds across the two foraging guilds, ground gleaner and foliage gleaner, significantly more foliage gleaners were present across all stops. This abundance of foliage gleaners is likely explained by overall species composition in the area. However, an analysis of species composition within the stops monitored would determine whether this result is due to many distinct foliage gleaning species or many individuals belonging to a small number of foliage gleaning species. Because foliage gleaners are present at higher densities than ground gleaners across all stops, and the total number of birds summed across the four indicator species is highest in lightly thinned stands, there may be more foliage present in lightly thinned stands than in other treatments. To accurately determine this association, data on total bird density across all species would have to be analyzed. Due to the presence of foliage at all stops analyzed, this abundance of foliage gleaners is expected. An analysis of industrially managed, clearcut land may result in more ground gleaning species.
Significantly more MacGillivray’s warblers than orange-crowned warblers, and significantly more orange-crowned warblers than Swainson’s thrush or Wilson’s warblers were present across all stops. Similar to the distribution of birds across foraging guilds, these differences may simply indicate general abundance in the area. It is also possible that Hyla Woods creates habitat that better provides for the requirements of certain indicator species than for those of other indicator species. These results are not directly associated with foraging guild type because all indicator species used in this study belong to the foliage gleaning guild.
The most significant trends from this data are that birds prefer stands with a predominantly Douglas fir forest type, and birds prefer lightly thinned stands to other treatments. Because the data on forest type only includes stops with an herbaceous understory and is not significant using the Bonferroni correction, additional research should be done before drawing any major conclusions regarding forest type. Because similar results emerged from a variety of tests on treatment, the conclusion that birds prefer lightly thinned stands seems fairly robust. In creating avian habitat, landowners should implement the harvest method of light thinning. However, because different species require a variety of habitat (Parrish and Hepinstall-Cymerman 2012), and total number of birds does not necessarily correlate with total number of species, maintaining a variety of habitat through varied treatment methods remains important.
More significant differences between stops may not have been found due to limitations in data. It is also possible, however, that the amount birds use these different stops does not vary significantly. Because the properties owned by Hyla Woods are relatively small, birds may travel throughout each property, using a variety of habitat types. Because the Hyla Woods properties are primarily adjoined to land managed in an industrial method relying on large clearcuts, heavy herbicide application, and single-age monoculture rotation, birds may pack into Hyla woods properties from these surrounding areas (Hejl 1992). Birds may also gravitate toward the edge habitat between forest and clearcut (Bosakowski 1997).
Future research should be performed to more completely answer the question of how the different forest characteristics present on Hyla Woods property impact avian populations. A study design similar to the one used in this paper should be implemented with specific research questions and analysis methods in mind. The set up should include stops with all combinations of the factors investigated as well as replicates of those combinations. Stops should be located in the center of stands demonstrating the desired characteristics to avoid stops with intermediate characteristics. Stops should also be located away from roads and major trails to avoid the impact of these open spaces on bird behavior as well as habitat characteristics. In addition to analyzing differences between certain characteristics within Hyla Wood’s property, stops should be added on neighboring properties. These additional stops would provide data to test the packing hypothesis, that birds may disproportionately utilize the habitat created by Hyla Woods. Two of the three main factors that differ between Hyla Woods management and that of industrially managed forests were investigated in this study, that of forest type and harvest method. The third factor, herbicide use, could also be investigated with the addition of stops on neighboring property.
While avian abundance may be used as a proxy for forest health, it may also be important to analyze avian diversity. As many factors as possible should be used in determining whether a forest ecosystem is “healthy”. Forest health may be difficult to quantify in a landscape so heavily influenced by human presence. Hyla Woods has the appropriate data on birds as well as many other species to perform a study comparing species abundance and diversity on their properties to that of industrially managed forests. These additional studies may shed more light on the beneficial impacts of alternative silvicultural practices on forest ecosystems. More complete research may in turn influence policy associated with managing state forestland.
Thank you to Pam and Peter Hayes, owners and managers of Hyla Woods, who supplied data and oversaw the research portion of this project. I would also like to acknowledge the birders who helped with bird identification and data collection, Steve Engel, Nate Richardson, and Lars Norgren with a special thanks to Char Corkran and Lori Hennings who donated their time and expertise as lead birders. Thank you to Linda Craig, Ken Chamberlain, Kahler Martinson, and Charlie Graham for helping with count timing, recording of bird counts, and bird identification. Thank you to Joan Hagar who supplied her habitat monitoring protocol for this project. Finally, thank you to Delbert Hutchison, Associate Professor of Biology at Whitman College, for his support and guidance as the advisor to this project.
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