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. Continue reading
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
One of the guiding principles of the Extension Service is to be a source of research-based information. Research-based? Meaning that the information we provide is not supposed to be based on rumor or anecdotes, but is supported by science.
University researchers are obviously an important source of our research-based information. Nonetheless I believe that “research” and “science” come in many forms and on many scales. Many woodland owners like to experiment on their own forests to come up with management techniques that work for them.
I’ve found this especially to be the case when it comes to preventing deer and elk damage to western redcedar seedlings: from painting seedlings blue to scare tactics, I think I may have heard it all. Are these experiments “research”? Maybe – it depends on how they are set up and measured.
Recently a forest owner wrote to ask about one such browse deterrent method whereby a cedar and a spruce seedling are planted together (see photo). (The hypothesis: the animals are deterred by the sharp spruce needles; the spruce thereby protects the cedar; eventually, when the cedar has grown above browsing height, the spruce is carefully cut away.) The individual wanted some specific guidance on how to do this, and wanted to see a demonstration site. Although we know that people have tried this method, to our knowledge none of these plantings were carried out in a scientifically valid way. We can provide a hypothesis on how things might turn out, but to date we do not have research-based information to provide. Instead, we can only rely on anecdotal evidence.
I’m a strong advocate for woodland owners contributing to our collective knowledge of woodland management by trying out different techniques on their own properties. However, there are several important design factors to keep in mind if you want to call your experiments “research”:
(If you missed them, here’s Part 1 and Part 2. Now for the final installment…)
Coweeta and other LTERs have all kinds of equipment which continuously monitor and record temperature, precipitation, stream flow, water chemistry, and so forth, and thus have compiled valuable long-term records.
At Coweeta, these records date back to 1934, and two climate trends are evident from the data that’s been collected since then. First, there’s been an upward trend in temperature since around 1980 (before that, there was no discernible trend). Second, with respect to rainfall, the wettest years have been getting wetter, and the driest years have been getting drier. They collect data on rainfall chemistry too; and interestingly, they started seeing a sharp drop in sulfate concentrations around 1990 – coincident with the passage of the Clean Air Act which was enacted in response to sulfur dioxide deposition (a.k.a. acid rain).
The biggest takeaway I left Coweeta with was an appreciation for the value and power of long-term observation. Forests grow slowly, and so we need to be really patient if we want to understand how they work. This is one of the reasons why the network of LTER sites across the country is so valuable.
This leads to some further musings. One, as a family forest landowner, you probably don’t have access to fancy monitoring equipment, or a Ph.D. scientist (or two or three) for hire. However, you do have a place that you observe on a fairly regular basis and you and your family may have a long-term connection to that place. Your observations, and more importantly your recording of your observations, have power. You can monitor changes on your property for your own purposes – wildlife sightings, stream changes – whatever fits your interests. For example, if you attend the upcoming June 23rd tour at Hyla Woods, you’ll learn how the host family has been monitoring birds in different forest types on their property for years.
Additionally, there are opportunities to contribute your locally collected data to larger networks to help scientists understand long-term and large-scale patterns of change. Some examples include the National Phenology Network, the Community Collaborative Rain, Hail and Snow Network (CoCoRaHS), and the Oregon Invasive Species Hotline.
The final thought – partly because nature is full of long-term processes, our scientific understanding evolves over time, and sometimes what seems like a pattern or a clear result in the short term turns out to be different in the long term. I suppose that’s why forest management practices are based on the “best available science” of the time, but as time passes we might revisit and revise what is considered a best management practice. If those scientists who planted the pine watershed at Coweeta had stopped their experiment after ten years, they would have come to false conclusions about different tree species’ water use. And if climate scientists looked at trends over just a decade or two, they would certainly also miss the big picture.
In Part 1, I reflected on whole-watershed-sized forest science experiments that have informed present-day management practices and understanding of water cycling through forests. But what happens when a factor beyond our control changes the forest ecosystem, creating a quasi-experiment of its own? That’s what is happening right now in the southeast U.S. due to an aggressive non-native insect.
For the record, we have hemlock woolly adelgids here in Oregon also, but they don’t cause much harm to Oregon’s two native hemlock species, western hemlock and mountain hemlock. The scientist who led our tour at Coweeta described why, tossing around fancy terms I haven’t uttered much since graduate school such as stylet, petiole and parenchyma. Basically what it boils down to is that the insects cannot penetrate the leaf structure of our west coast hemlock species very easily.
But back east, the hemlock woolly adelgid is leading to the loss of an entire component of the forest ecosystem throughout the Appalachian region. What is the impact when a tree species is lost from the landscape? Many scientists are trying to answer that question, looking at everything from soil chemistry to aquatic habitat to understory species composition.
Unfortunately the hemlock woolly adelgid is not the only non-native insect to create such widespread impact. While on a family trip to Wisconsin last summer, I heard a lot about the emerald ash borer, another invader from Asia which is killing ash trees throughout the midwest. Unlike the hemlock woolly adelgid, the emerald ash borer hasn’t shown up on the west coast yet (that we know of). If it arrived, would it wipe out our Oregon ash trees? I hope we don’t have to find out.
Last week, I traveled to western North Carolina for a natural resources Extension conference. While there, I took a field trip to the Coweeta Hydrological Laboratory – a 5,400 acre experimental forest and the oldest continually running LTER (Long Term Ecological Research) site in the country. Coweeta is famous as the site of groundbreaking studies of how forest management and land use changes affects things like water supply and quality. It was a fascinating tour and if you have an interest in forest science, read on over the next few days as I share some of what I learned and reflect on how it relates back home in Oregon.
Many of the studies at Coweeta are set up as paired watershed studies. Two watersheds of similar size and topography are selected. 
One is left as a control, and the “treatment” is applied to the other.
What is striking about paired watershed studies is the sheer size of the experiments. Here is a photo from a watershed at Coweeta that has been studied since the 1940’s. Back then, scientists wanted to know whether converting a mixed hardwood forest to a pine plantation would impact the water supply. So, they clearcut the treatment watershed, controlled the regrowing vegetation for a decade, and then planted it back to eastern white pine.
For the first ten years, there was more water in the stream exiting the cut watershed than in the control watershed. But, as soon as the pine was planted, water levels in the stream began to return to normal, and by the time the pines were ten years old, they were using as much water as the control forest. Ever since then, there has been significantly less water in the stream exiting the pine watershed than the hardwood watershed. Why? At the risk of oversimplification, it boils down to a few reasons: 1) pines grow (and thus use water) all through the mild Appalachian winter while the hardwoods lose their leaves and shut down; 2) pines have more foliage surface area
than hardwoods, so there’s more capacity for photosynthesis (and, when trees photosynthesize they use water); and 3) pines are less efficient water users than the native hardwood species – sort of like a regular shower head compared to a low-flow one – they both get the job done, but one uses a lot more water. These were an important finding because most of the region’s drinking water originates from these mountain streams.
We have well-known paired watershed studies in Oregon, too. Some are conducted at our “local” LTER, the H.J. Andrews Experimental Forest. Other paired watershed studies in the Coast Range at Alsea, and Hinkle Creek, and Trask have informed the development of today’s Forest Practices Act and other best forest management practices.
To learn more about the research in paired watersheds in Oregon, you can watch a videostream of a recent lecture at OSU. Also this week, as part of the Starker Lecture Series in the OSU College of Forestry, there was a field tour of the Alsea watershed studies. Unfortunately, I couldn’t make the tour. Did you go? If so, what did you learn?
As a follow up to an article I included in last winter’s newsletter, here’s a story from OSU’s Terra magazine about some research on the effectiveness of beaver relocation projects. In theory, relocating beavers from areas where they are a nuisance to areas where they could contribute to habitat restoration could benefit all involved (including, presumably, the beavers themselves). Do relocated beavers stay put? Do they actually help create fish habitat in their new homes? Read the blog post, or listen to a short podcast.