This set of pages describes ongoing and past research - with lots of pictures from the field to help you visualize the fun part of the process. You can also drag down on the "Research" tab to find highlights from the Millennium Redwood Project and other past research.
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Sensitivity of Douglas-fir and western hemlock forests to drought and irradiance
This research combines tree-ring isotopes collected across climate gradients in the Pacific Northwest with intense monitoring of sap flux near the canopy tower at Wind River, Washington. The tower at Wind River will eventually become a primary NEON site for the Pacific Northwest.
This research combines tree-ring isotopes collected across climate gradients in the Pacific Northwest with intense monitoring of sap flux near the canopy tower at Wind River, Washington. The tower at Wind River will eventually become a primary NEON site for the Pacific Northwest.
Dr. Chris Still (left) and Dr. Rick Meinzer (right) at the top of the tower are two primary collaborators on this research effort. Renee Brooks and Julia Burton are additional collaborators on this research.
A view down into the canopy from the top of the tower may make the trees appear relatively small, but many of the tallest trees exceed 50 meters in height.
Bishop pine mortality patterns in response to historic drought in California
Pictured here is our research group from a November 2014 data collection trip to Santa Cruz Island (SCI). From left to right is Linlin Gao, Steve Voelker, Reed Arce, Sara Baguskas, Chris Still, Bharat Rastogi, Rebecca Miller and Burke Greer. Chris, Sara and Bharat have done research here, mostly investigating to how fog effects ecosystem processes including the occurrence and mortality patterns of Bishop pine. We were at SCI to characterize patterns of mortality and survival within stands, across the rugged topography of the island and how that may interact with fog occurrence.
Pictured here is our research group from a November 2014 data collection trip to Santa Cruz Island (SCI). From left to right is Linlin Gao, Steve Voelker, Reed Arce, Sara Baguskas, Chris Still, Bharat Rastogi, Rebecca Miller and Burke Greer. Chris, Sara and Bharat have done research here, mostly investigating to how fog effects ecosystem processes including the occurrence and mortality patterns of Bishop pine. We were at SCI to characterize patterns of mortality and survival within stands, across the rugged topography of the island and how that may interact with fog occurrence.
Mortality of the Bishop pines was striking -- here dead trees flank a met station positioned on a shoulder ridge with the Pacific ocean in the background. About 35% of all adult trees have died within the past 1-3 years. More will die in 2015 and 2016 since mortality lags drought and the drought has only worsened in 2015. It is not unreasonable to expect that 3/4 of the pines or more may be dead by the end of 2016.
A wider view of the same shoulder ridge: this was a typical level of mortality.
We took tree cores of live and dead trees at each plot sampled so we can assess whether age, growth rate or growth variability was associated with a greater likelihood of mortality.
We took tree cores of live and dead trees at each plot sampled so we can assess whether age, growth rate or growth variability was associated with a greater likelihood of mortality.
This view, with the crew walking to a nearby sample plot shows that there are a few live pines, some graying pines that died 1-3 years ago and a lot of red-needled pines that died during the summer of 2014.
Carbon allocation to stems versus roots
To the left are two adjacent ponderosa pine stands near Black Butte, Oregon. On the left is the control stand and on the right is the "shelterwood" stand. The shelterwood stand is more open because it underwent a heavy cutting in 1987. This treatment greatly decreased seasonal drought stress and increased tree growth. We have also been studying a wet forest ecosystem on the Oregon coast where carbon availability has been similarly modulated.
To the left are two adjacent ponderosa pine stands near Black Butte, Oregon. On the left is the control stand and on the right is the "shelterwood" stand. The shelterwood stand is more open because it underwent a heavy cutting in 1987. This treatment greatly decreased seasonal drought stress and increased tree growth. We have also been studying a wet forest ecosystem on the Oregon coast where carbon availability has been similarly modulated.
Selfie in front of a pine that was 125cm (~4ft) in diameter. In the background is a root excavated to take a core sample for dendrochronological dating and growth comparisons to the trunk. Digging and coring large roots is arduous work! Although the coarse roots and trunks are separated by only 1-2 m, the roots are much more sensitive to environmental change than the trunks, indicating projections of carbon allocation in forests need to represent this variability.
Snowpack reconstruction potential in the Oregon Cascades using tree-ring stable isotopes
Pictured here are Anne Nolin, a snow research expert, and Chris Ratcliff, then a senior in the BioResource Research program at OSU. He has since graduated but this was his undergraduate thesis project. We sampled trees near the McKenzie Pass and Santiam Pass SNOTEL stations. Chris is still working with me to get the data set published in a peer-reviewed journal.
Pictured here are Anne Nolin, a snow research expert, and Chris Ratcliff, then a senior in the BioResource Research program at OSU. He has since graduated but this was his undergraduate thesis project. We sampled trees near the McKenzie Pass and Santiam Pass SNOTEL stations. Chris is still working with me to get the data set published in a peer-reviewed journal.
Snowpacks like that shown here on North and Middle Sister mountains supply water to cities, for agriculture and hydropower. However, snowpack is declining across the western United States. The record low snowpacks of 2014/2015 (see below) have caught national attention, largely due to the extreme drought in California and the realization that these snowpacks provide much of the water that sustains urban centers and agriculture in the western United States.
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A high pressure ridge over the west coast has deflected winter storms in 2014/2015, causing record low snowpack across much of the west. The snowpack levels are shown here, using data from SNOTEL stations like those we sampled tree-rings near. Not only are there extremely low values but there are only a handful of stations that met the 1981-2010 average.
The tree-ring carbon isotope signals we have sampled, even at the snowiest locations, show strong climate correlations. The climate signals differ depending on location/elevation: these include precipitation over the previous year, or summer vapor pressure deficit. In terms of ecosystem water balance, these factors can be considered the water supply and demand, respectively. In the future we will investigate using tree-ring isotopes collected at differing elevation bands to model past variation in snowpack. |
Central Oregon Forest Drought Stress and Resilience
In spring of 2015 the Voelker Lab was invited to collaborate on a new study with the Center for Advanced Forest Ecosystem Research, located within the US Forest Service PNW research station. This research aims to determine how the forests of central Oregon have responded to past and recent drought stress. Our results should help discern whether increased forest densities, resulting from fire suppression, may make the landscape less resilient to future droughts. Other primary researchers include: Dr. Rick Meinzer, Dr. Tom Spies, Dr. Chris Still, Andrew Merschel and Dr. John Roden.
To the left is Andrew Merschel, collecting a wedge from an old grand fir that we are currently analyzing for tree-ring carbon stable isotopes (Photo by Chris Ratcliff).
In spring of 2015 the Voelker Lab was invited to collaborate on a new study with the Center for Advanced Forest Ecosystem Research, located within the US Forest Service PNW research station. This research aims to determine how the forests of central Oregon have responded to past and recent drought stress. Our results should help discern whether increased forest densities, resulting from fire suppression, may make the landscape less resilient to future droughts. Other primary researchers include: Dr. Rick Meinzer, Dr. Tom Spies, Dr. Chris Still, Andrew Merschel and Dr. John Roden.
To the left is Andrew Merschel, collecting a wedge from an old grand fir that we are currently analyzing for tree-ring carbon stable isotopes (Photo by Chris Ratcliff).
Climate Change Effects on Forests of the Lake Superior Region
In July of 2015 Dr. Voelker and undergraduate research assistant Chris Ratcliff traveled to Lake Superior. We cored trees at the Turkey Lakes Watershed, a long-term climate and water and atmospheric chemistry monitoring site in Ontario, Canada. Then I went to the south shoreline of Lake Superior, where at the Huron Mountain Club in Michigan we collected tree cores and water samples from the lakes and streams for stable isotope analyses. These tree cores are being used for pilot studies investigating mixed temperate/boreal forest responses to climate change. I hope this research will ascertain 1) how climate change and temperature amplification by Lake Superior have differentially impacted tree species on the north (sugar maple) or south (white spruce) edges of their range and 2) whether we can use tree-ring isotopes to reconstruct water temperatures of Lake Superior across the late Holocene. To address these questions I will be working with a diverse group of colleagues including Dr. Kate McCulloh, Dr. Bob Fahey, Dr. Julia Burton, Dr. Paul Hazlett, Dr. Kara Webster, Dr. Kerry Woods, Dr. Rose-Marie Muzika, Dr. Michael Stambaugh, Dr. Richard Guyette, Dr. Renee Brooks and a number of other researchers.
Below and left, Dr. Paul Hazlett is shown coring a sugar maple tree at a forest inventory plot at Turkey Lakes Watershed. Below and right, my father (Leonard Voelker, who graciously served as a field assistant for a week) in the foreground taking a core from a sugar maple and myself in the background collecting a core from a white spruce at the Huron Mountain Club. Photos by Chris Ratcliff.
In July of 2015 Dr. Voelker and undergraduate research assistant Chris Ratcliff traveled to Lake Superior. We cored trees at the Turkey Lakes Watershed, a long-term climate and water and atmospheric chemistry monitoring site in Ontario, Canada. Then I went to the south shoreline of Lake Superior, where at the Huron Mountain Club in Michigan we collected tree cores and water samples from the lakes and streams for stable isotope analyses. These tree cores are being used for pilot studies investigating mixed temperate/boreal forest responses to climate change. I hope this research will ascertain 1) how climate change and temperature amplification by Lake Superior have differentially impacted tree species on the north (sugar maple) or south (white spruce) edges of their range and 2) whether we can use tree-ring isotopes to reconstruct water temperatures of Lake Superior across the late Holocene. To address these questions I will be working with a diverse group of colleagues including Dr. Kate McCulloh, Dr. Bob Fahey, Dr. Julia Burton, Dr. Paul Hazlett, Dr. Kara Webster, Dr. Kerry Woods, Dr. Rose-Marie Muzika, Dr. Michael Stambaugh, Dr. Richard Guyette, Dr. Renee Brooks and a number of other researchers.
Below and left, Dr. Paul Hazlett is shown coring a sugar maple tree at a forest inventory plot at Turkey Lakes Watershed. Below and right, my father (Leonard Voelker, who graciously served as a field assistant for a week) in the foreground taking a core from a sugar maple and myself in the background collecting a core from a white spruce at the Huron Mountain Club. Photos by Chris Ratcliff.
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The images below show increment core collections from logs that have fallen into two of the many lakes on the Huron Mountain Club property. This is pretty much the best fieldwork that you can do. The weather and water is nice and the lake breeze keeps the mosquitoes at bay.
About 75% of logs were white pines and the rest eastern hemlock (we did not sample trees that were hardwoods). These old trees are preserved in the water -- which allows us to extend tree-ring collections back in time past the oldest living trees that started growing near 1750. We used large borers (0.5 inch or 12 mm diameter) because the cores come out of the old trees intact more of thanten those from a standard sized borer. The Huron Mountain Club does not allow motor boats so we used the rowboats provided for club members. However, use of a motorboat and a chainsaw (or crosscut saw) would greatly expedite sampling if we expand our efforts to other lakes. We only sampled logs in shallow water for this survey but the use of a 12-volt winch or hand-winch would allow logs from deeper water (i.e. 4-20 feet deep) to be dragged into shallower water for sampling.
About 75% of logs were white pines and the rest eastern hemlock (we did not sample trees that were hardwoods). These old trees are preserved in the water -- which allows us to extend tree-ring collections back in time past the oldest living trees that started growing near 1750. We used large borers (0.5 inch or 12 mm diameter) because the cores come out of the old trees intact more of thanten those from a standard sized borer. The Huron Mountain Club does not allow motor boats so we used the rowboats provided for club members. However, use of a motorboat and a chainsaw (or crosscut saw) would greatly expedite sampling if we expand our efforts to other lakes. We only sampled logs in shallow water for this survey but the use of a 12-volt winch or hand-winch would allow logs from deeper water (i.e. 4-20 feet deep) to be dragged into shallower water for sampling.
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Finally, nothing tastes finer at the end of a long day coring trees than one or two bottles of Third Coast beer, a hoppy and satisfying blonde ale brewed by Bell's, in lower Michigan. Their packaging features a map of southeastern Lake Superior, covering the locations of the Huron Mountain Club and Turkey Lakes Watershed.
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