HARC Online Workshops - 26-30 November 2001

Discussion Summary: 26 November 2001

Thank you all for participating in the opening day of the HARC online workshop to discuss drivers and implications of changing treeline in the Arctic. Today's discussion was extremely diverse and raised many interesting questions that outline areas for future research, for example:

• How does soil type, including permafrost, affect the movement of treeline?
• Where is treeline most sensitive to various forces, such as human activity, substrate, or climate?
• What is the relevance of treeline as a boundary for humans, and how has the position of treeline influenced the use of wood products, including driftwood?
• How susceptible is the location of treeline to human activity, and to what kind of activity and at what spatial and temporal scales?
• How do ecological factors such as species composition and competition affect the location of treeline, and do current models overlook these factors?
• What are the temporal characteristics of treeline change – i.e., how do we move from one relatively stable position of treeline to another?

Sakari Kankaanpää, moderator
Frans Wielgolaski, moderator
Glenn Juday, discussant
Henry Huntington, SMO director

DISCUSSION QUOTES:

"Transient changes in vegetation do seem to be a crucial issue and I agree that our models of them are limited because our concepts and study of them are still quite recent. I wonder whether major advances in the treeline could be the result of the interaction between climate-influenced seed availability (increase probability of abundant crops) and some strongly negative effects on tundra (climate "disasters" reducing the competitive exclusionary effect of the tundra)." –Glenn Juday

"History shows us that the response of arctic treeline to past climate changes has been regionally heterogeneous, so we might expect the same in the future. This means that these questions may have different answers in different parts of the Arctic, and everyone's own regional experience is an important part of the puzzle." –Mary Edwards

"We show that upland white spruce in interior Alaska respond negatively to summer temperatures, due to this temperature induced drought stress. The trees are not at their thermal limits. They do quite well at warmer temperatures in other areas. But they may possible be at their moisture limits in terms of available moisture." –Val Barber

"Inuit were using spruce trees and whale bones as structural supports for their sod houses, spruce boughs lined sleeping platforms, etc. Working with the LDEO Tree Ring lab, we are building a chronology to better date archaeology sites using dendrochronology and gather additional information about the climate in the region." –Sue Kaplan

"Multiresolution remote sensing could help with the sorting out of stable treelines, but maybe GIS (substrate and topography) and climate data ought to drive the remote sensing. NASA has noted interest in using coarse sensors for finding 'hot spots' of change. Much more can be done with Landsat than coarser spatial resolution sensors than has been done with, say 1 or 4km pixel AVHRR. One intriguing point that might play in here – what does an advancing treeline look like?" –Tom Allen

"Who would have thought a few short years ago that sites to launch hang-gliders or to hills to perform 'high marking' snowmobiles would be valuable and contested resources today? " –Glenn Juday

Discussion Summary: 27-28 November 2001

The discussion about the location of treeline in the arctic and its implications has spanned a broad range of topics. The discussion has maintained a comparative treatment of the properties at treeline in different regions of the Arctic, including humidity, elevation, snow depth, tundra impact, logging, wildlife grazing and permafrost depth. Some of the central ideas under discussion are:

• What are the relationships among tundra moisture, tundra disturbance, competitive exclusion and treeline advance?
• How does climate warming feedback with fire, insect infestation, drought, active layer thickness and treeline advance?
• How limiting are seed production, seed viability, and seed dispersal?
• What are the long-term effects of disturbance on the landscape and how do trees respond?
• How have people in northern regions used available driftwood, since when and in what ways?
• How does wildlife grazing and caribou migration impact treeline?

We thank all of the participants who have contributed to the discussion and encourage everyone with a question or comment to chime into the discussion. We appreciate the questions and comments we are receiving from school teachers and graduate students as well. We look forward to continuing this international and interdisciplinary discussion tomorrow.

See you online!

Sakari Kankaanpää, moderator
Frans Wielgolaski, moderator
Glenn Juday, discussant
Henry Huntington, SMO director

DISCUSSION QUOTES:

"If we are interested in where the treeline will be in 100 years, we have lots of things to consider--climate, vegetation, insects, browsers, humans--but if we are thinking in terms of millennia, perhaps it's a lot simpler. This also depends on the spatial resolution of the models, and what is meant by a "reasonable approximation." –Henry Huntington

"We know that forest fires are influencing treelines in northeastern Canada. Increased summer temperatures may cause a more shallow permafrost zone and more rapid accumulation of organic litter in boreal forests, enhancing wildfires. Fires may lead to nutrient losses on short terms, but also to better seed regeneration and growth on dry sites. On wet sites in northeastern Canada, it has been shown e.g. by Payette that fires in combination with insect outbreaks often lead to a higher water table, poor seed reproduction and retreat of treeline." –Oddvarskre Skogforsk

"In our humid part of the world, the deciduous Nordic mountain birch is generally forming the treeline. Because of recent warming by climate change a few new plants are established at higher elevation or further north than before. However, in the harsh climate useually with only a sparse vegetation,the establishment is difficult. By research it is found that planting both small birch seedlings and small coniferous trees under shrubs that are native in an area (most often Salix shrubs in our case) we can extend the growth area considerably." –Frans Wielgolaski

"The "hunt" for the Bob Marshall plots was finally successful this year, we found two trees alive from 100 planted in 1968." –Martin Wilmking

"The lesson from northern Scandinavia has shown that the road system together with the logging increase fragmentation and has direct impact to the reindeer herding. The logging activities have been increased in North-West territories and Alaska but have been quite low so far. However, the Scandinavian type large scale logging will most probably have effect on the winter habitat of caribous." –Sakari Kangkaangpää

"The intuitive and logical answer to the question of how the tundra-taiga interface will react to global warming is that it should move north. This may be the eventual outcome if climatic warming persists over centuries or millennia. However, closer examination of the tundra-taiga interface across its circumpolar extent reveals a more complex situation." –Robert Crawford

Discussion Summary: 29 November 2001

Some interesting points were raised in today's discussion relating to how disturbance, by fire, reindeer or caribou grazing, or human development, can promote or retard the spread of treeline. It has been proposed that fire may have a positive feedback on the spread of birch trees, a theory which has only begun to be tested in the field at treeline. We encourage more investigators from the Frostfire research project in interior Alaska to provide further information on how fire might impact the movement of treeline.

We have prepared an outline of the report that will result from this online workshop. The 5-10 page report will cover the information presented in the discussion and conclude with a few of the future research questions that were unveiled through the dialogue. Please take a moment to look at the discussion outline below and send us an email if have comments or additions to the outline. We have been impressed by the diversity of the discussion and are impressed by the potential for future research that is necessary to continue to unravel the relationships among the variables influencing treeline throughout the arctic and how human activities affect, and are effected by treeline.

Sakari Kankaanpää, moderator
Frans Wielgolaski, moderator
Glenn Juday, discussant
Henry Huntington, SMO director

DISCUSSION QUOTES:

"Unlike in Sweden and Norway, reindeer herding is practised in Finland not only by Sami people but there are also Finnish people among the reindeer owners. The reindeer herding area in Finland extends about 400-500 km south from northern treelines (i.e., down to the middle boreal zone). Thus, it's not surprising that (as Sakari has told) there are controversies between forestry and reindeer husbandry." –Seppo Neuvonen

"I agree that the past treeline movement can tell us a lot on what we can expect to happen by further climate change. However, how much do we know on species diversity in the past, and what will the species composition be like at the treeline in the future?" –Frans Wielgolaski

"The surface layer of dead vegetation (leaves, mosses, lichens) can, if the fire is slow enough and hot enough) be stripped back to a skeletal soil. Revegetation may be quite slow (the Frost Fire experiment near Fairbanks will at least provide some controlled data on recovery) and early stages in regeneration are dominated by mosses (at Kobuk, a mixture of mosses (four Polytrichum species, Ceratodon purpureus in particular), lichens, and low forbs. Scattered white spruce seedlings occur, but the most significant tree species regenerating is birch... My point, I guess, is that fire must be a significant contributing factor which could lead to an artificial shift southwards of the treeline (by destroying the vegetation) and also encourage a northerly shift through the provision of a suitable seed bed and nutrients." –Rod Seppelt

Discussion Summary: 30 November 2001

Dear Treeline Workshop Participants,

On behalf of the HARC Science Management Office, thank you for joining us this past week in the on-line workshop on treeline. I would like to thank Frans Wielgolaski and Sakari Kankaanpää for serving as moderators, Glenn Juday for being our discussant, and Renee Crain and Wendy Warnick for their hard and talented work behind the scenes.

Thank you again for your participation, and please let us know if we can be of help in developing proposals to the Human Dimensions of the Arctic System initiative at the U.S. National Science Foundation.

Henry P. Huntington
HARC SMO Director

Moderators

• Sakari Kankaanpää is a researcher at the Finnish Forest Research Institute in Rovaniemi, Finland. He is a zoologist with an interest in treeline questions that began when he coordinated a timberline workshop that was held in Whitehorse, Yukon in 1998. He is presently involved in EU’s international reindeer research project RENMAN and coordinating Arctic Council’s northern timberline project.
  http://www.paliskunnat.fi
  http://www.arctic-council.org

• Frans Wielgolaski is professor in Botanical Ecology at the University of Oslo, Norway. He has tought in this field for 40 years and has written and edited several books in Ecology. Two recent books are Polar and Alpine Tundra, 1997, 920 pp., in the Elsevier Series: Ecosystems of the World, and Nordic Mountain Birch Ecosystems, 2001, 390 pp., in UNESCO's Man and the Biosphere Series. In the 1970s he was one of the leaders of the International Biological Program (IBP) in Norway and internationally in their Tundra Program, resulting in many scientific papers and books. At present he is chairman of the board in EU's international mountain birch project HIBECO.