Research Highlights

"Hermit Warblers (Setophaga occidentalis) are an endemic-breeding species in the Pacific Northwest that winters in Mexico and the Central Americas. This species faces threats from mature forest loss and climate change throughout its range, but we know little about its migration ecology. To understand the annual movements of Hermit Warblers, researchers tracked 22 adult male Hermit Warblers. Birds showed shorter and faster movements during spring migration compared to fall migration. A high degree of mixing on the wintering grounds among birds from different breeding locations indicated low migratory connectivity. A compressed breeding schedule and departure of birds from the breeding grounds in early July may indicate that breeding is limited by a short window of favorable climatic conditions for breeding, which could signal heightened vulnerability under future climatic scenarios."

Kim, H., R. B. Siegel, J. L. Stephens, J. C. Hagar, B. J. Furnas, M.-S. Jeong, B. C. McComb, and M. G. Betts. 2024. Annual migratory movement, apparent molt-migration, migration schedule, and diffuse migratory connectivity of Hermit Warblers. Avian Conservation and Ecology 19(2):6. https://doi.org/10.5751/ACE-02622-190206

In the last 10 years, David Herasimtschuk has photographed forests across the Pacific Northwest, documenting the inhabitants of these last remaining old-growth ecosystems. From salamanders and salmon to bears and mountain lions, his images illustrate not only the beauty of the forests and their creatures but the symbiotic relationships which are vital to the forests’ health and the planet’s welfare. 

See the full article and photographs at https://www.npr.org/sections/the-picture-show/2024/09/03/g-s1-5057/photographer-captures-life-in-old-growth-forests

A cross-site synthesis marking the 40th anniversary of the LTER Network reveals how a long-term ecological research perspective facilitates insights into ecosystem response to climate change, described in an overview paper by Jones and Driscoll (2022). At all 28 LTER sites, from the Arctic to Antarctica, air temperature and moisture variability have increased since 1930, with increased disturbance frequency and severity and unprecedented disturbance types, altered primary production, enhanced cycling of organic and inorganic matter, and changes in populations and communities.

The Andrews Forest is one of nine forest/freshwater LTERs.  Campbell et al (2022) report that forest and freshwater ecosystems are tightly linked and together provide important ecosystem services, but climate change is affecting their primary production, carbon storage, water and nutrient cycling, and community dynamics.

Jones and Driscoll (2022) report that virtually all ecosystem and ecological processes are being affected by changing climate. Responses differ by region or ecosystem type, and interact with other past and ongoing human activities. Ecosystem responses to climate change are just emerging and are likely to intensify as climate change accelerates. Long-term ecological research can link changes in greenhouse gases to environmental forcing, ecosystem responses, ecosystem services, and climate feedback loops. These syntheses demonstrate the value of and need for continued long-term ecological research on ecosystem responses to global climate change.

In an introduction to the series, Nelson (2022) notes that our knowledge, our love, and our privilege as ecosystem researchers carry a corresponding responsibility to directly address climate change both by describing the impacts of climate change on ecosystems and by advocating on behalf of those ecosystems.

Press release from Oxford University Press: https://www.eurekalert.org/news-releases/961901

Findings from a recent study indicate that old-growth forests may provide thermal refugia for species that are sensitive to climate change effects. The compositional diversity and microclimatic conditions of old-growth forests may provide resources and conditions that are less available in simple second-growth forest stands under global warming. The authors conclude that "Conservation of old-growth forests, or their characteristics in managed forests, could help slow the negative effects of climate warming on some breeding bird populations via microclimate buffering and possibly insurance effects."

The research is featured in an EcoWatch article and in a radio interview on Jefferson Public Radio.

Full article: "Forest microclimate and composition mediate long-term trends of breeding bird populations" in Global Change Biology, Hankyu Kim, Brenda C. McComb, Sarah J. K. Frey, David M. Bell, Matthew G. Betts

The summer and fall seasons in the Pacific Northwest are typically warm and dry, and solar radiation and breezes affect temperature and moisture content of the air under the forest canopy. In forest plantations, in which all trees are of similar height, the sun heats the canopy and creates an inversion—the air closest to the ground is cooler, and air near the top of the tree canopy is warmer. On days with strong canopy heating, this inversion limits moisture loss through the top of the canopy and enhances winds that flow downslope below the canopy, carrying moisture out of the system. On days with less canopy heating, winds mix air above and within the canopy and promote moisture loss to the air above the forest canopy. Regional models project declining dry-season relative humidity in the future. Collectively, these findings indicate that future climate conditions will increase vertical and downslope moisture loss from forest plantations, which represent a large fraction of forest cover of the Pacific Northwest of the USA.

Drake, S. A., Rupp, D. E., Thomas, C. K., Oldroyd, H. J., Schulze, M., & Jones, J. A. (2022). Increasing daytime stability enhances downslope moisture transport in the subcanopy of an even-aged conifer forest in western Oregon, USA. Journal of Geophysical Research: Atmospheres, 127, e2021JD036042. https://doi.org/10.1029/2021JD036042

Phenology is the study of the timing of major life-cycle events of organisms. A general prediction under climate change is that phenological events will occur earlier with increasingly warmer temperatures. For aquatic insects, a major life-cycle event is emergence, the transition of the aquatic juvenile stage to a terrestrial flying adult. We asked a simple question: If aquatic insects experience warmer water, do they emerge earlier? The answer, it turns out, is not so simple. We evaluated springtime emergence timing for two common species of stonefly, one mayfly, and one caddisfly across six headwater streams of the Lookout Creek basin, for six consecutive years. The six streams spanned a thermal/elevation gradient, and mean water temperature also varied through time by 1.6℃ (2.9℉) on average between the coolest and warmest years.

Among the four species, we detected three major responses. (1) The caddisfly responded directly to springtime temperatures, emerging predictably earlier in both warmer streams and in warmer years. (2) One of the stoneflies had a naturally lengthy emergence period (up to three months), such that differences in timing among streams or years were not detectable. (3) The final two species, a mayfly and the other stonefly, showed an intriguing pattern of nearly synchronized emergence throughout the Lookout Creek basin within individual years but in warmer years, they all emerged substantially earlier than in cooler years. This third pattern suggests intricate physiological mechanisms likely associated with timing and length of winter dormancy to ultimately coordinate mating periods. These final two species have short adult life spans, a characteristic that could make it “worth it”, evolutionarily speaking, to have complex physiological mechanisms for coordinating emergence among streams. After all, individuals of these species are in a major time crunch to mate and lay eggs.

Overall, despite the high variability in physiological response among species, our results meet general predictions and observations from other systems: we can expect aquatic insect emergence to occur earlier in the Lookout Creek basin as temperatures continue to warm.

Finn, D. S., Johnson, S. L., Gerth, W. J., Arismendi, I., & Li, J. L. (2022). Spatiotemporal patterns of emergence phenology reveal complex species-specific responses to temperature in aquatic insects. Diversity and Distributions, 00, 1– 18. https://doi.org/10.1111/ddi.13472 

A snow drought occurs when warm temperatures result in mountains receiving a higher proportion of precipitation as rain instead of snow. A new study measured the effects of the 2015 snow drought on water transit time, the time that water molecules spend moving through a basin. Dr. Catalina Segura modeled transit time in seven basins in the H.J. Andrews Experimental Forest and found that mean transit times during the 2015 drought were shorter (< 2yrs) than in 2016, 2017, or 2018. The lack of a snowpack in 2015 likely resulted in lower infiltration of water in the soil which limited the connection between water received as precipitation during 2015 and old ground water stored in the landscape. The 2016–2018 transit times were longer (2–6 yrs) varying widely across all basins but especially within the smaller high elevation watersheds, indicating that the impact of the 2015 snow drought was stronger in basins that depend heavily on snowmelt input.  These results were based on the analysis of water stable isotopes in 796 samples of stream water and precipitation. Although the impact of the 2015 snow drought appears short-lived, these results are critical considering the expected regional snowpack decline as the climate warms in the western USA. 

Reference: Segura, C. (2021). Snow drought reduces water transit times in headwater streams. Hydrological Processes, 35( 12), https://onlinelibrary.wiley.com/doi/full/10.1002/hyp.14437

A commentary by Mark Harmon, OSU professor emeritus, recently published in the journal Biogeochemistry focuses on the role of woody detritus (aka dead trees) in biogeochemical cycles.  The ecological role of dead trees in aquatic, terrestrial, and riparian environments has been a topic of long-held interest within the Andrews Forest community.  Moreover, the Andrews Forest hosts the so-called 200-year Log Decomposition Study.  One the study sites, affectionately known as the “log bone yard”, also serves as an observation station for the Long-Term Ecological Reflections program.  So, our collective obsession with the dead tree has been well established across disciplines.  

Harmon’s latest contribution examines the current state of knowledge regarding how dead trees have, and will, influence water, nutrient and organic matter flows within and between ecosystems to influence very small scale (the soil nutrients beneath a log) to global phenomena (the amount of carbon in the atmosphere).  Harmon’s commentary anticipates the key scientific developments needed to more fully understand how recently observed and projected increases in tree mortality will influence forested ecosystems function and management in the future.  He does this by not only reviewing the literature, but by developing a series of mini-models that synthesize knowledge to suggest hypotheses for future exploration.  Many of these explorations reveal that the response we perceive will be highly dependent on the level, or scale, of the examination.  For example, nutrients can be lost from a decomposing tree, but accumulate in a collection of the trees as forests age. This suggests that we need to not only learn much more about the processes controlling dead tree dynamics, but also must meet the challenge of building an integrated, multi-scale understanding. 

More reading:  

Harmon, Mark E. 2021. The role of woody detritus in biogeochemical cycles: past, present, and future. Biogeochemistry. 154(2): 349-369. doi: 10.1007/s10533-020-00751-x 

The LTER Reflections Program and the Forest Log, a collection of works of writers and artists in residence, including Jerry Martien’s Return of the Dead Log People, written after a visit to a 200-year log decomposition study site

In the face of a warming climate, organisms may find at least temporary refuge in cooler nooks and crannies of a landscape. Previous work from the Andrews Forest (Frey et al. 2016 – Science Advances) found that sites with concave microtopography and with old-growth forest structure tended to be cooler than other locations across the landscape. But how consistent is this effect? If plants, animals, fungi etc. are to find refuge in hot years, it is critical that such sites are consistent over time (otherwise biodiversity would need to move around the landscape to track refugia). This is where long-term undercanopy data from the Andrews Forest come in. Chris Wolf (a postdoc with Matt Betts’s group at OSU) and colleagues analyzed 10 years of microclimate data from 184 sites across the Andrews Forest to test whether there is temporal consistency in thermal refugia. Three important findings emerged. First, cool and hot sites were remarkably consistent and predictable across the 10-year study. This is good news for organisms that aren’t likely to pick and move to track microclimates (e.g., lungless salamanders, herbaceous plants, tree seedlings, mosses, lichens). Second, old-growth forests played an important role in this refugia effect (on the order of 3-5 degrees C cooler in summer months). Finally (and this is the less good news), free-air temperature (i.e., how warm it is in the region) overwhelmed the capacity of local sites to stay cool. That is, even though the coldest sites across the Andrews Forest are consistently so, even these sites warm up considerably in hot years. Overall, these findings have important implications for policy and management; to maintain microrefugia in a rapidly changing climate, conservation of old-growth and other structurally complex forest habitat is critical, especially at sites with high elevation relative to their surroundings.

Wolf, Christopher; Bell, David M.; Kim, Hankyu; Nelson, Michael Paul; Schulze, Mark; Betts, Matthew G. 2021. Temporal consistency of undercanopy thermal refugia in old-growth forest. Agricultural and Forest Meteorology. 307: 108520. doi:https://doi.org/10.1016/j.agrformet.2021.108520

A food chain shows what eats what in an environment. A food web shows the structure of the interconnections between multiple food chains. Food webs show the architecture of trophic relationships, revealing the biodiversity and species interactions in an ecosystem. Most research about food webs has focused on species interactions while the influences of surrounding environments often have been overlooked.  Understanding which factors change the structure of a food web offers us the ability to predict how a food web will change when influential factors in the environment are altered.

A group of scientists from Oregon State University used pre-existing data from the HJ Andrews Experimental Forest to look at how the structure of aquatic food webs varied across a range of geophysical conditions within a whole stream system.

The researchers found that the structure of food webs responds to geophysical features at both local (i.e., slope) and broader (i.e., basin size) spatial extents. River food webs are complex because they not only include multiple species of aquatic insects and fish, but also all of their interactions. Researchers analyzed the size and complexity of stream food webs across the Lookout Creek basin in relation to stream size and local geophysical characteristics. They found that downstream food webs, with higher levels of omnivory, are more resilient than upstream food webs. This finding extends ecologists’ understanding of the stability of stream food webs and will help in predicting how food webs and stream communities may respond to both natural disturbances and current global environmental change.

Full paper:  Zatkos, Lauren; Arismendi, Ivan; Johnson, Sherri L.; Penaluna, Brooke E. 2021. Geophysical templates modulate the structure of stream food webs dominated by omnivory. Ecosphere. 12(3): e03444. doi:https://doi.org/10.1002/ecs2.3444

Temperature is a primary control on ecological systems and processes, ranging from enzymatic reactions to tree growth. Temperature is also a fundamental characteristic of climate. Indeed, much of the concern about the impact of climate warming on ecosystems is motivated by the pervasive influence of temperature on organisms like plants. Although scientists often focus on air temperature, the actual temperature of a plant is more relevant; a plant’s temperature can depart from air temperature by 10-20 degrees Celsius. By mounting thermal cameras in trees, we can take trees’ temperatures directly using technology similar to what is found in night-vision goggles. The patterns that appear in canopy thermal images are interesting. For example, we see typically warmer trunks and branches and cooler leaves. Also, we see that the thermal patterns change rapidly throughout the day due to solar radiation, wind, and transpiration.

In a recent paper, researchers used canopy thermal images to understand connections between tree canopy temperatures and biological processes like photosynthesis, as well as the response of trees to heat waves and droughts. Thermal image data from an old-growth Doug-fir canopy at the Andrews Forest were showcased in the paper to highlight nighttime radiative cooling that leads to dewfall in the upper canopy, potentially ameliorating drought stress in the rainless summer at this site. Continued monitoring of tree canopy temperatures at the Andrews Forest is planned. New thermal imaging using drones will capture thermal data of forests of different ages and at different positions on the landscape such as along north- or south-facing hillslopes and proximity to streams.

The full paper is: Still, C. J., Rastogi, B., Page, G. F. M., Griffith, D. M., Sibley, A., Schulze, M., Hawkins, L., Pau, S., Detto, M., & Helliker, B. R. (2021). Imaging canopy temperature: shedding (thermal) light on ecosystem processes. New Phytologist. https://doi.org/10.1111/nph.17321. 

Sixty oral histories totaling more than 160 hours of interviews of Andrews Forest researchers and staff and participants in Northwest Forest Plan formulation are now available online in the Voices of the Forests: Voices of the Mills archive in the OSU Library Special Collections and Archives Research Center.

Some of these records gathered from as early as 1991 are already being used in storytelling and historical work, such as the Oregon Public Broadcasting’s podcast “Timber Wars” which aired in 2020, and in a book on the Northwest Forest Plan currently in preparation by Norm Johnson, Jerry Franklin, and Gordie Reeves (OSU Press).

The interviews cover topics such as the establishment of the LTER Network and the Andrews Forest research program [Jerry Franklin, Art McKee] and the life of a District Ranger working closely with researchers during the Forest Wars of the early 1990s [Lynn Burditt, Steve Eubanks], to the plans for information management designed to carry through the decades [Susan Stafford].  In one interview, you’ll hear Eric Forsman’s reflection on growing up as a kid observing birds and other wildlife along the McKenzie River on the outskirts of Springfield; through his career as a Forest Service scientist, Eric focused on the northern spotted owl and now, in retirement, sees the species on the brink of extinction.

Another effort in historical archives work is the recent posting of the personal and professional records of Horace Justice (HJ) Andrews. This collection of 152 digital records is online as a database (SS008) in the Andrews Forest databank.  The collection includes early personal records of the 1920s, correspondence, news articles, and condolence letters to his widow from government officials, including Supreme Court Justice W. O Douglas.

Thanks to historians Sam Schmieding and Max Geier for their critical roles in this work, and for the support of Fred Swanson in the efforts to archive these records.

The book A Place for Inquiry, A Place for Wonder: The Andrews Forest offers a historical account of the place and the people of Andrews Forest; its programs of research, education, partnership with land managers, and arts/humanities. Historian Bill Robbins places the work of the Andrews Forest within its larger and continuously evolving societal and political contexts, which both influenced and were influenced by discoveries at the Andrews Forest. Robbins recounts stories concerning watershed science, characterization of old growth, and the northern spotted owl, and extends the account to the current cast of characters and projects.

A conversation about the history of the Andrews Forest, including a Q&A with Bill Robbins and Michael Paul Nelson, is on the Andrews Forest YouTube channel:  https://youtu.be/5PikollmpwE

Bill Robbins discusses his book and the Andrews Forest long-term research, in light of the September 2020 Holiday Farm Fire, on the OSU Press Blog: http://osupress.oregonstate.edu/blog/inquiry-and-wonder-in-andrews-forest

If you are interested in learning more about or purchasing Bill Robbins’ book, A Place for Inquiry, A Place for Wonder: The Andrews Forest, you can find it at the OSU Press website. Through December 31, 2020, take 30% off and free shipping when you purchase directly through the OSU Press website. Enter the promo code 20HOLIDAY at checkout to receive the discount.

From OSU Press:  “In A Place for Inquiry, A Place for Wonder, historian William Robbins celebrates the long-overlooked Andrews Forest, highlighting its importance to environmental science and policy. From its founding in 1948, the experimental forest has been the site of wide-ranging research, beginning with postwar studies on the conversion of old-growth timber to fast-growing young stands. Research shifted in the next few decades to long-term ecosystem investigations of climate, streamflow, water quality, vegetation succession, biogeochemical cycling, and the effects of forest management, putting the Andrews at the center of a dramatic shift in federal timber practices: from industrial, intensive forest management policies to strategies emphasizing biodiversity and healthy ecosystems.”

Bill Robbins is an OSU Emeritus Distinguished Professor of History. He has authored and edited many books, including “Landscapes of Conflict: The Oregon Story, 1940-2000” (published 2004) and “Landscapes of Promise: The Oregon Story, 1800-1940” (published 1997).

Dwarf mistletoe’s quaint name belies its severity. The native parasitic plant commonly infects western hemlock trees in western Oregon and Washington via projectile seeds that land on branches and bore through the tree’s bark, where the plant induces tissue swelling and deformities. The result: a diminished ability to transport water and other physiological effects, which reduce tree growth and increase mortality, especially among heavily-infected trees.

How might a parasitic plant, like dwarf mistletoe, interact with the climatic conditions scientists project? A long-term data set and new study may provide the answer.

David Bell, a research forester based at the Corvallis Forestry Sciences Laboratory, and Oregon State University colleagues Robert Pabst and David Shaw reviewed several decades of data gathered at the Wind River Experimental Forest, a 500-year-old-forest located in Washington State that is part of the Forest Service’s Experimental Forest and Range Network. Wind River, and the 83 other sites located across the country, are maintained as long-term experimental areas and represent the largest and longest-lived ecological research network in the United States. Bell and his colleagues studied five repeated measurements of nearly 1,400 individual hemlock trees from 1991 to 2014, examining how western hemlock tree growth and mortality varied with temperature increases, precipitation decreases, and mistletoe infection rates.                                                                                         

“Although mistletoe infection intensity varied across individual trees over this time frame, our results suggest that warmer, drier conditions amplified the parasitic plant’s effects on western hemlock growth and mortality,” Bell said.

Specifically, tree growth rates decreased and mortality rates increased during warmer‐drier time periods for all trees, regardless of infection status. Growth reductions and mortality increases were also related to mistletoe infection intensity, most notably during the warm and dry measurement intervals.

“Our study, grounded in a rich long-term data set, revealed an unrecognized vulnerability of forests to climate change as a function of common and endemic pests and pathogens, especially in westside forests, which are generally assumed to have low vulnerability,” Bell said. “We expect that other forest pests or pathogens also would amplify the effects of climate change.”

For managers, these findings suggest that native pest and pathogen management may be a key component of preparing for climate change.

--From: the US Forest Service Pacific Northwest Research Station "Science Spotlight"

The full article "Tree growth declines and mortality were associated with a parasitic plant during warm and dry climatic conditions in a temperate coniferous forest ecosystem" was published in "Global Change Biology".

Western hemlock dwarf mistletoe (Arceuthobium tsugense subsp. tsugense) is a small, parasitic plant that infects the leaves and branches of its host plant, the western hemlock (Tsuga heterophylla) tree. Within a forest, like the HJ Andrews Experimental Forest, areas of mistletoe infection are patchy. Some areas of the forest have trees that are not infected, while other areas have trees that are heavily infected. Hemlock trees infected with dwarf mistletoe grow dense, multi-branched growths, called witches’ brooms. Researchers believe that mistletoe infections cause changes in the tree’s growth and water use. To understand the effect of mistletoe in the canopy of a tree, and in the broader area of a forest, graduate student Stephen Calkins and postdoc scholar Sky (Yung-Hsiang) Lan are climbing into the canopy of dozens of western hemlock trees to take a closer look. They measure the extent of the mistletoe infection by noting size and location of brooms in each tree crown. They also map each branch in the tree, recording its location and measuring the size. Each tree will also be cored to measure its sapwood. With these data, Stephen and Sky, together with their advisor, Dave Shaw, from Oregon State University, hope to learn more about how dwarf mistletoe may be affecting forest stands across the Pacific Northwest. See a little of the field work, high in the canopy, at https://andrewsforest.oregonstate.edu/gallery/dwarf-mistletoe-survey-2019. 

A recent publication out of the HJ Andrews Experimental Forest LTER site illustrates the role that summer research experiences can play in contributing to LTER science and in engaging and mentoring students. Oregon State University graduate student Matthew Kaylor is the lead author on a paper about how trout and salamanders respond to drought. Kaylor wrote this paper in collaboration with two undergraduate students. The first student, Brian VerWay, worked with Kaylor to survey trout and salamanders in a set of streams in the Andrews Forest in 2014 and 2015. As it happened, 2015 was a severe spring/summer drought year in the Pacific Northwest region. VerWay wrote his senior undergraduate honors thesis and published a paper on the movement, growth and abundance responses of fish to drought in one tributary stream of the Andrews Forest (VerWey et al 2018). In 2016 and 2017, the second student, Alvaro Cortes, revisited six of the stream sites that Kaylor and VerWay had surveyed. Cortes wrote his senior theses about the recovery of fish and salamander populations from the 2015 drought. The three students worked with their advisor, OSU Assistant Professor Dana Warren, on a paper that pulled together their research into a broader story. The paper, “Drought impacts to trout and salamanders in cool, forested headwater ecosystems in the western Cascade Mountains” was published in Hydrobiologia. Their findings suggest that drought impacts salamanders and trout, but the responses differ. They found fewer adult trout in the drought year. Salamander abundance remained the same, but body condition was lower in the drought year. Both trout and salamander populations seemed to rebound within two years of the drought. The work could not have happened without strong leadership and mentoring by the graduate student, nor without the engagement and interest of the undergraduate student researchers. It was a collaborative exercise that reached across multiple years of data collection and multiple projects at the Andrews Forest LTER site. 

From OSU Press Release http://today.oregonstate.edu/news/streams-may-emit-more-carbon-dioxide-warmer-climate:

"Streams and rivers could pump carbon dioxide into the air at increasing rates if they continue to warm, potentially compounding the effects of global warming, a new worldwide analysis has shown.

To reach that conclusion, an international research team conducted the first continental-scale study of carbon flows into and out of streams across six major climatic zones. They collected data in watersheds from Puerto Rico and Oregon to Australia and Alaska. In each one, scientists analyzed the balance between photosynthesis — which uses atmospheric CO2 to generate plant material such as roots and leaves — and respiration, which pumps CO2 back into the air.

“This paper is the first to look at the effects of climate change on stream metabolism at the continental scale using field observations,” said Alba Argerich, co-author who monitored McRae Creek and Lookout Creek in the H. J. Andrews Experimental Forest. “This approach takes into consideration the complexity of an ecosystem, as opposed to controlled experiments where you recreate simplified versions of an ecosystem.” 

Argerich and other scientists monitored streams for water temperature, dissolved oxygen and sunlight at the water surface. The researchers also simulated the balance between net primary production (the product of photosynthesis by all organisms in the stream) and respiration under a 1-degree Celsius rise in stream temperature. The net result of the simulations, they reported, was a 24 percent shift toward more respiration and CO2 emissions. 

The shift toward more CO2 emissions appears to be more pronounced in warmer streams, the scientists found, while colder streams might actually see an increase in net primary production. Carbon cycling in streams can also be affected by other factors such as the plants and microbes in the stream ecosystem and nutrients flowing into the water from surrounding lands."

Also see:

Article from Oregon Public Radio's EarthFix program:https://www.opb.org/news/article/climate-change-warm-streams-carbon-pollution/ 

See the full article in Nature Geoscience, "Continental-scale decrease in net primary productivity in streams due to climate warming"

Clearcuts often create stark boundaries between forest habitats. These ecological “edges” can seriously affect neighboring undisturbed ecosystems for some distance in from the edge, perhaps representing a multi-decadal legacy of has clearcutting. A new study led by David Bell took on the question of how historical timber harvests have affected the structure of neighboring old-growth forests in western Oregon. Bell and his team used a remote-sensing technique called lidar to map tree basal area (a measurement related to tree density and biomass) in lower and middle elevation mature and old-growth forests in the Andrews Forest. They then assessed how harvest edges have influenced tree basal area and how those effects varied with harvest size and age. They found that forests within 75 meters of harvest edges (approximately 20% on the unharvested forests) had 4-6 percent less live tree basal area than forests tucked in the interior away from edges. They were surprised to find that the length of time since harvest had little or no effect: whether the harvest happened 13 years ago or 60 made little difference on the structure of surrounding unharvested forest area. This implies that the edge influence persisted over many decades in spite of forest recovery processes. This study is important in examining the subtle impact of human activity on forest landscapes in western Oregon and showing how widespread and long-lasting the edge influence of past clearcutting has been on neighboring old-growth forest.

The paper, Historical harvests reduce neighboring old-growth basal area across a forest landscape, is published in the journal Ecological Applications: http://onlinelibrary.wiley.com/doi/10.1002/eap.1560/abstract

There is much discussion about how plantation forestry affects streamflow in dry (lowflow) seasons, especially as climate change may exacerbate water scarcity. Analysis of 60‐year records of daily streamflow from eight paired‐basin experiments in the Andrews Forest revealed that the conversion of old‐growth forest to Douglas‐fir plantations had a major effect on summer streamflow. Average daily streamflow in summer (July through September) in basins with 34‐ to 43‐year‐old plantations of Douglas‐fir was 50% lower than streamflow from reference basins with 150‐ to 500‐year‐old forests dominated by Douglas‐fir, western hemlock, and other conifers. The study, by Timothy Perry and Julia Jones, was published in 2016 in the journal Ecohydrology. View the full article online: http://onlinelibrary.wiley.com/doi/10.1002/eco.1790/full

Streams move carbon from land into oceans and the atmosphere. Carbon in streams can come from leaf litter decomposing in the water. How quickly that leaf litter decomposes depends upon the temperature of the water — the higher the temperature of the water, the faster the rate of decomposition. With climate change, stream temperatures are expected to rise. The rise in stream temperature is projected to increase rates of leaf litter decomposition, thereby affecting the carbon cycle. A team of scientists, including Andrews Forest scientist Sherri Johnson, synthesized 1025 records of litter breakdown in streams and rivers to quantify its temperature sensitivity.

The study indicates average breakdown rates may increase 5 percent to 21 percent with a 1 degree to 4-degree Celsius rise in water temperature — half as much as the 10 percent to 45 percent increase predicted by metabolic theory. Mean annual water temperature for some streams and rivers is currently rising at an annual rate of about 0.01 degrees to 0.1 degrees Celsius due to changes in climate and land use. Read more in a University of Utah press release on the article.

The study “Global synthesis of the temperature sensitivity of leaf litter breakdown in streams and rivers” was published February 2016 in Global Change Biology. View the full article.

The amount of carbon stored in tree trunks, branches, leaves and other biomass — what scientists call “aboveground live carbon” — is determined more by timber harvesting than by any other environmental factor in the forests of the Pacific Northwest, according to a report published by researchers at Oregon State University: "Complex mountain terrain and disturbance history drive variation in forest aboveground live carbon density in the western Oregon Cascades, USA" (doi:10.1016/j.foreco.2016.01.036).

In forests that are about 150 years old or less, live carbon above the ground is associated primarily with the age of a stand — reflecting how long ago it was harvested — rather than with climate, soil, topography or fire. However, as forests mature into “old growth,” the density of carbon is determined largely by factors other than harvesting.

The Pacific Northwest has some of the highest forest-carbon densities in the world. Understanding how much carbon is stored in growing forests is a critical component of international efforts to reduce climate change. 

Researchers found that air temperatures, sun exposure and soils were also important in driving the variation in live carbon across the region. High-elevation forests tend to be cooler and contain lower amounts of carbon than do low-elevation forests. 

Researchers conducted the study at the H.J. Andrews Experimental Forest in the Cascade Range east of Eugene. They combined data from two types of measurements: LiDAR (an aerial mapping technique that uses lasers) and ground-based forest inventories in which scientists measured tree growth at 702 forest plots. The study is one of the few to quantify carbon in living forest biomass in mountainous terrain.

Harold Zald, research associate in the College of Forestry, is lead author of the paper published in the journal Forest Ecology and Management.

“Very few studies have looked at above-ground carbon at a landscape scale with the combination of LiDAR and detailed disturbance history (logging and fire) that we have at the H.J. Andrews Forest,” said Zald. “These findings can be applied to the Douglas-fir dominated forests on the west slope of the Cascades in Oregon and Washington.”

The researchers found that fire was not a significant driver of carbon density in the H.J. Andrews. In the last century, these forests have experienced little severe “stand replacing fire,” but it’s possible that fire played a significant role in shaping the structure of old-growth forests and increasing carbon density over time. “Remnant old-growth trees resulting from non-stand replacing fires likely enhance the recovery of forest C (carbon) density,” they wrote.

The study was conducted by researchers at Oregon State University, the Pacific Northwest Research Station of the U.S. Forest Service and the University of Natural Resources and Life Sciences (BOKU) in Vienna, Austria.

This story is also available at http://bit.ly/1U7tKrT.