Silviculture and Carbon in the Cloquet Woods

Photo by Philip Potyondy

What are the connections between forests and atmospheric carbon?  How do different silvicultural interventions affect forest-based carbon uptake and storage?  On February 25, about 75 foresters, researchers, and others took to the Cloquet Forestry Center woods to find out.

The tour included visits to red pine, aspen, and mixed aspen-spruce stands with a variety of management histories, from benign neglect to a century of intensive management. At each stop, we discussed the stand history, rates of carbon sequestration and accumulation, and the impact of past and possible future silvicultural treatments.

Although the discussions took us much deeper into detail than is presented here, this post offers top-level take-home messages from the tour.

The tour was part of the February 2009 Forest Values and Carbon Markets conference.

Pure red pine: The student thinnings

This is one of the more impressive examples of the impact of active management in red pine that I know of.  The stand originated naturally around 1910, so it’s about 100 years old.  On one side of the road, the 40-acre stand has been thinned four times: in 1950, 1960, 1970, and 1985.  On the other side of the road, the stand has never been thinned.

Focusing on carbon dynamics, both stands have sequestered approximately the same amount of carbon during the past 100 years.  However, in the unthinned stand, almost 40% of that carbon has returned to the atmosphere, or is in process of doing so, through mortality and decomposition of dead wood.  In the thinned stand, almost all of that natural mortality has been “captured” through thinning and turned into wood products.

In the early thinnings, nearly all of the harvested material went into pulp production.  Pulp is a short-lived wood product, so much of this carbon would have returned to the atmosphere within 5-10 years.  However, in the later thinnings, larger and larger proportions of the harvested wood went into long-lived wood products such as construction materials.  Long-lived products store carbon on a nearly permanent basis.

Although not the focus of this tour, the four thinnings have also dramatically increased the financial return.  Including returns from products sold (compounded at 5% annually) plus the value of standing timber on the sites, the thinned stand has a total value of over $6,000 per acre, many times that of the unthinned stand.

Comparing the two stands drove home the potential of active forest management to do three important things: 1) reduce atmospheric emissions of carbon through mortality and decomposition, 2) increase long-term carbon storage by increasing the proportion of harvestable wood products that are long-lived rather than short-lived, and 3) produce a dramatic financial return.

See a photo slideshow from the student thinnings site here.

Aspen-spruce mix

Our next stop was at a 22-year old mix of aspen and white spruce.  The stand originated from a 1987 clearcut.  Natural regeneration was almost pure aspen, and in the same year as the harvest, 800 white spruce seedlings per acre were planted on the site.  Like most of the CFC soils, this is a low-productivity site for aspen, with a site index of only about 55 (meaning 50 year old aspen would be about 55 feet tall).

This stand has interesting silvicultural potential.  Perhaps the most likely treatment would be to harvest the aspen when it becomes merchantable, likely around age 45-50, leaving the spruce intact.  Depending on the pattern of harvest (e.g. uniform vs. patches), this would lead to some regeneration of aspen and more shade-tolerant conifers such as white spruce or balsam fir.

From a carbon storage perspective, this system would retain a relatively high level of carbon storage on site after the sale and harvest of the aspen.  White spruce is relatively long-lived in Minnesota and could easily be managed on an 80-120 year rotation.  The extended rotation, combined with the increase in growing space from the aspen removal, would also increase the growth rate of the spruce, producing larger trees and a higher proportion of long-lived wood products at the final harvest.

Based on research conducted in this area, on stands of similar age and composition, this stand is estimated to accumulate carbon at a rate of about 2.35 tonnes of CO2 equivalent per acre per year.  (Accumulation is sequestration minus respiration.)

See a photo slideshow from the aspen-spruce site here.

Mixed reserve stand

Just across University Road from the aspen-spruce stand is a reserved (unmanaged) mixture of aspen, birch, balsam fir, white spruce, and scattered other species.  (This stand is in reserve status on the CFC management plan.)

Photo by Emma Schultz

This stand is very similar to the stand that was clearcut in 1987 to produce the mixed aspen-spruce stand described above.

Typical of older stands, this one is breaking up fairly rapidly.  Dominant birch and aspen are nearing the end of their natural lives, particularly for northern Minnesota sandy sites.  Decadent stands like this one have a number of important ecological benefits: they provide coarse woody debris for forage, den sites, and cover as well as a different kind of habitat from intensively managed stands.

From a carbon dynamics perspective however, stands like this one are less than optimal.  Even before they fall, the dying trees begin to decay and emit carbon through the respiration activities of decomposition.

Based on research conducted in this area, on stands of similar age and composition, this stand is estimated to accumulate carbon at a rate of only about 0.4 tonnes of CO2 equivalent per acre per year.  This is just over 1/4 the rate of the aspen-spruce mix across the road.  The primary difference is the high rate of decomposition-related respiration in the reserve stand. (For more on this difference, click here.)

See a photo slideshow from the reserve site here.

Young pure aspen

Photo by Emma Schultz

The final stand we visited was a young pure aspen stand.  By this point of the tour, most of the big ideas were clear:  This stand is accumulating carbon at a relatively fast rate, which is great.  However, the likely silvicultural trajectory for pure aspen in this part of the world is a 40-55 year rotation followed by clearcut.  This pattern, while creating important benefits for wildlife habitat and local production of renewable wood products, does not lead to a high level of long-term storage of atmospheric carbon.

This point is clarified by comparison with the mixed aspen-spruce stand described above.  In that stand, after harvest of the merchantable aspen, a large standing stock of carbon remains in storage in the stand.  The tradeoff, of course, is lower production of aspen, which is important to Minnesota’s wood products industry.

See photos from the young aspen site here.

B4WARMED

After visiting all of the stands, we visited the B4WARMED experiment.  This experiment, led by Peter Reich with a number of other University of Minnesota collaborators, simulates the projected warming trend and will monitor impacts on native trees.  The study uses a sophisticated system to carefully monitor and manipulate soil and above-ground temperature fluctuations.  (Want to learn more about the project? Check out this KAXE interview with Rebecca Montgomery.)

Summing it up

The tour included several hours of discussion, in the woods, of practical issues associated with forest-based carbon accumulation, the role of silviculture, and related issues.  We also discussed possible carbon credit payments and associated (and complex) issues like additionality, leakage, and carbon credit protocols.  The take-home messages about carbon are as follows:

1. Increasing stocking of a long-lived shade tolerant species can increase the stand’s potential for long-term carbon storage.
2. Longer rotations, regardless of species, can increase long-term carbon storage as long as they don’t exceed the natural lifespan of the dominant species.
3. Increasing the proportion of harvestable products that are long-lived (e.g. construction materials) as opposed to short-lived can increase long-term storage after harvest.
4. Frequent thinning can capture mortality, turning trees that would otherwise die and decompose into products that can be harvested and sold, and at least some of which will contribute to long-term post-harvest storage.

Update: Minnesota Public Radio ran a story today called Northwoods hold an answer to slowing effects of climate change that covers similar ground.

What are your thoughts? Leave a comment or question below.

Free climate change webinar series for Spring 2009

This webinar series will run from January – May 2009 and feature monthly presentations geared to help land managers, consulting foresters, and private forest landowners stay informed on the latest science and tech transfer tools related to forest-based adaptation and mitigation of climate change. Each webinar is an hour long, including Q & A, although there will be an optional additional 15 minute Q & A period. Each webinar counts as one hour of continuing education credit for certified foresters.

The syllabus so far is as follows:

January 14, 2009 | Wed | 2pm EST:
Interactions Between Carbon, Climate, and Forests
Presenter: Chris Swanston (Research Ecologist, Northern Research Station, USFS)
This presentation will set the stage for a broader discussion on climate change and forests by briefly examining interactions between climate change, carbon cycling, and forest sustainability. First, we’ll cover some key mechanisms and major trends in climate change, and then explore forecasts of future climate and associated uncertainty. Next, we’ll survey the global carbon cycle and the distribution of carbon in major forest ecosystems. We’ll then consider several general ecophysiological concepts and how projected changes in climate may interact with forest ecophysiology. Finally, we’ll discuss how all these considerations may combine to affect forest carbon storage and productivity in the Lake States and Northeast.

February 11, 2009 | Wed | 2pm EST:
Forest Management During Climate Change
Presenter: Maria Janowiak (Outreach Scientist, Northern Institute of Applied Carbon Science)
Climate change is expected to have significant effects on the condition and function of forested ecosystems; however, the exact nature of the stressors, their intensity, and the ensuing impacts on forests are quite uncertain. Forest managers will need to cope with this uncertainty, balancing the paucity of detailed information on future conditions against the demands of active and sustainable resource planning and management. In this context, sustainable forest management must recognize the need for ecosystems to adapt to changing climatic conditions in order to achieve desired objectives including, among other things, maintenance of habitat, production of wood, and mitigation of increased levels of atmospheric greenhouse gases. This presentation synthesizes available information on forest management options in the northeastern United States to provide a background for working with an uncertain climate future.

March 18, 2009 | Wed | 2pm EST:
CVal: A Carbon Valuation Tool for Foresters and Private Forest Landowners
Presenter: Sarah Hines (Presidential Management Fellow, USFS)
This presentation will introduce participants to a just-released Carbon Valuation Spreadsheet and accompanying General Technical Report (GTR) written by Ted Bilek, Peter Becker, and Tim McCabee (2008). The spreadsheet is a powerful and valuable tool available to the forestry community (target audience: consulting foresters, state foresters) to be able to interface with private landowners and help them make sound, transparent decisions as to whether participation in the voluntary carbon market is an attractive option based on a full accounting of variables.

April 15, 2009 | Wed | 2pm EST:
TBA

May 13, 2009 | Wed | 2pm EST:
TBA

Click here to download a poster version of these details.

How to connect:
The webinar and dial-in info for the Climate Change Continuing Education Webinar Series is as follows:
Website: http://www.mymeetings.com/nc/join.php?i=747085393&p=&t=c
Meeting Number: 747085393
Phone number: 1.866.581.6894
Passcode: 8623725

Family forest radio & podcast series continues

The American Forest Foundation and Earth & Sky’s radio and  podcast series on family forest issues continues.  The podcasts are excellent and well worth a download.  This month’s series focuses on carbon credits with Neil Sampson.  Details from the announcement are below.Tune in to Earth & Sky radio network and website to learn how forest landowners manage their land for us today and the next generation tomorrow.

Starting this week, hear from Neil Sampson, of The Sampson Group, talk about the impact of climate change on forests through the following Earth & Sky radio shows and podcasts:

Climate change speeding flux of forest ecosystems
Carbon offsets could be boon to private forests
Forests are a family value, says expert
Extended Podcast: Neil Sampson on forests and climate change

The American Forests Foundation proudly continues our partnership with Earth & Sky through the production of the “2008 Forests Series” radio shows and podcasts.

You can listen to all of the past “2008 Forest Series” radio shows and podcasts at www.forestfoundation.org/cel_radio.html.

The shows will air on over 1,800 radio stations in the U.S. You can find a radio station broadcasting Earth & Sky Radio Shows in your area at www.earthsky.org/about/radio-affiliates. You can also listen online at www.earthsky.org and through iTunes.

Earth & Sky is a successful short format science radio program heard by millions of listeners throughout the U.S. and abroad that highlights the wonders of science and nature through daily radio shows.

Carbon credits on Minnesota woodlands

A brief overview of carbon credits on Minnesota woodlands.

Minnesota woodlands and climate change

How will climate change affect Minnesota woods? What changes should you expect? What can you do to prepare? This page will answer some of these questions.

Projected future changes

UCS/ESA image

It’s hard enough to predict tomorrow’s weather. Predicting climate change is complex. Different climate models offer different predictions. According to a recent report from the Union of Concerned Scientists, by the end of this century Minnesota’s summer climate will resemble the current climate of Kansas, and the winter climate will be more like that of southern Wisconsin.
There’s general agreement that Minnesota’s climate will get warmer. What’s less certain is what will happen to precipitation: will it get warmer and drier or warmer and wetter?

Impacts on Minnesota forests

Minnesota lies at the juncture of four major ecological provinces, or biomes. Ecological boundaries depend heavily on temperature and rainfall patterns, and changes in temperature and rainfall are likely to have relatively major effects near the boundaries.

Stress

Warming temperatures are likely to stress trees that are adapted to cooler conditions. This stress may predispose trees to secondary insect or disease agents, making them more vulnerable. This would be exacerbated by longer and/or more frequent drought events.

Insects & disease

Antoine Hnain img

Healthy trees can defend themselves against most native insect and disease threats. However, stressed trees are more vulnerable. As a consequence, native pests like the two-lined chestnut borer and bronze birch borer can have more damaging outbreaks when trees are stressed. Both of these insects have had recent outbreaks due in part to drought events. These outbreaks, and associated losses, are likely to become more common.

Invasive plants

Many invasive species, like buckthorn, can thrive under a wide variety of conditions. Some native tree species can only thrive under a relatively narrow range of conditions. Changing climate may displace some natives, creating growing space that will be filled by invasives.

Non-native insects

Insects like gypsy moth (right) and emerald ash borer are likely to enter Minnesota soon. Different bugs have different impacts, but overall, new insect invaders will further stress and weaken forests, compounding stress from a changing climate.

What you can do to keep your woodland healthy

Here are a few general recommendations:

1. Maintain diversity. Manage your woods to include a variety of different species. Different species will be affected differently, and some will be more resilient than others.
2. Maintain stand vigor. Thinning your woods is an excellent way to improve overall stand vigor. Trees with large, full crowns receive more energy from the sun and are much more resilient than crowded, spindly trees.
3. Grow and harvest more timber! Growing forests are carbon sinks, turning atmospheric carbon into wood.
4. Monitor your woodlands carefully. Insect and disease outbreaks may travel through stands more quickly due to tree stress. The more quickly you can identify and act to control outbreaks, the more damage you can prevent.
5. Do your part to reduce greenhouse gas emissions.