ENTS, Lee is correct in saying that there are many methods available to test for and then reduce the many factors influencing ring width. These methods have been in development for nearly a century now. And, while it is a well-established science, we are still coming up with new methods to further reconstruct environmental history.
Couple quick thoughts on some of the idea in the thread here: - first, while lab studies do show an increase in plant growth when CO2 levels are immediately doubled, there is very little evidence or often contradictory evidence indicating CO2 fertilization impacts on natural trees. That isn't to say it isn't happening. It suggests either a) we do not know what we are doing yet/how to detect the influence of elevated CO2, b) the signal is so weak that it is overwhelmed by other factors, c) that only in certain growing conditions does elevated CO2 influence tree growth or d) something else is happening [i ran out of ideas here]. - people in the past have looked at global tree growth at latitudinal treeline sites, sites where global warming drives increased ring widths, removed the 'climate signal' to look for a residual increase in ring widths through time; a residual trend that might be the result of elevated CO2. that analysis revealed no trend and the authors suggested elevated CO2 was not an important factor of tree growth at these sites [but, this result could come back to a) above] - there is an incredible network of tree ring records 700 to 1000+ yrs in length in the western US, including Henri's 2000 yr record from New Mexico. An investigation looking at the percent of annual drought in this region does indeed suggest that the recent drought is becoming more severe than most droughts of the last 600 yrs. however, this same record indicates that the region was quite dry from 900-1300 A.D. If a similar drought hit today, well civilization would be altered significantly. you can find the abstract of this paper here: http://www.sciencemag.org/cgi/content/abstract/306/5698/1015 the data set from which this analysis is derived from is publicly available here: http://www.ncdc.noaa.gov/paleo/pdsi.html in fact, an update of this data set, V2, is available here. You can make maps of drought from this data set, too. neil On Jun 4, 12:58 pm, Lee Frelich <[email protected]> wrote: > Mike: > > The direct impacts of increasing CO2 would lead to wider rings, due to > CO2 fertilization and possibly modestly increased drought resistance. > However, severe droughts, competition from other trees and other local > factors that affect growth could easily override the rather modest > direct impacts of CO2 (i.e. direct CO2 effects may only partially offset > other negative influences). > > Increasing CO2 in the atmosphere causes heat to be retained near the > surface of the earth (i.e. global warming), which causes a change in > atmospheric circulation systems and redistribution of heat around the > world, with varying climate change in different regions (warmer, cooler, > drier, wetter in various combinations). If a given region gets drier as > a result of climate change, then increased drought frequency will show > up as narrower ring indices. It is possible to factor out various > influences in tree ring analyses, including factors such as tree age, > competition, temperature and phenomena such as El Nino (although climate > change itself might change El Nino frequency or intensity, and it might > be the object of study rather than something to factor out). These > factors can be taken into account in experimental design (i.e. choosing > trees that are more likely to be influenced by the factor of interest > and less likely to be influenced by unwanted factors in a given study), > as well as by filtering the tree sequences themselves. > > There are hundreds of papers in the scientific literature that present > methods for filtering out various factors, and one scientists junk to be > filtered out may be another scientists signal to be retained. For > example, in many studies of climate, competition among trees is factored > out (i.e. information on competition is thrown away as junk), whereas > most of my studies have done the opposite, and filtered out the climate > influences to retain just the competition signal, because I am > interested in releases from suppression in trees and reconstructing the > history of succession into gaps. > > Lee > > Mike Leonard wrote: > > > Bob, > > > Again the question is can you correlate the tree ring data with > > increased CO2 emissions while filtering out the impacts of El Nino, > > sunspot activity, etc? > > > Mike > > > -----Original Message----- > > *From:* [email protected] > > [mailto:[email protected]]* On Behalf Of* > > [email protected] > > *Sent:* Wednesday, June 03, 2009 7:49 AM > > *To:* [email protected] > > *Subject:* [ENTS] Re: High elevation forest response to > > climate change and other factors > > > Don, Mike, > > > Our own Dr. David Stahle, Lord of the Rings, has confirmed > > many instances of climate impact observable in the tree > > rings. His work studying the El Nino oscillation cycle has > > been well received within the scientific community. Dave > > will be one of the presenters at the Forest Summit - Old > > Growth conference in October at Holyoke Community College. > > Drs. Lee Frelich, David Foster, Don Bragg will also present. > > > Bob > > > ----- Original Message ----- > > From: "DON BERTOLETTE" <[email protected]> > > To: [email protected] > > Sent: Tuesday, June 2, 2009 10:49:52 PM GMT -05:00 > > US/Canada Eastern > > Subject: [ENTS] Re: High elevation forest response to > > climate change and other factors > > > Mike- > > I don't pretend to know much about NIPF in Massachusetts. > > > I don't think you have ever read me saying the phrase > > global warming. I know that to be a loaded concept that > > hasn't been universally accepted. > > > But I do believe that the regions I've worked and lived in > > are experiencing climate change outside of the natural > > range of climate variation. > > > Yes, actually there is tree ring documentation to that > > effect. Dendrochronology started with a man named Douglas > > at the Flagstaff Observatory (the one that discovered > > "canals" on Mars), and was furthered in partnership with > > early archeologist Emil Haury when they discovered missing > > tree ring segments in Anastazi roofing timbers...there are > > some really intereseting regional climate graphs that have > > been derived from dendrochronological research carried on > > at the University of Arizona at their Tree Ring Lab > > ('google' Tom Swetnum for a broad coverage of just about > > everything I've said). > > > I do however have a fair handle on forestry in the > > Southwest US. I can send you any number of supporting > > documents regarding my statements below. I stand behind my > > statement that all five of those points are inter-related, > > not separated as they were in your reply. Deconstruction > > doesn't work that way. > > > Regarding your comments on bio-fuels, you may be surprised > > that I've supported it, particularly in the Southwest, and > > with smaller more efficient operations. For much of the > > ponderosa pine forests, conditions (4 of 5 points below) > > have led to abundant smallwood that despite multiple > > efforts, no commercial operations can handle. More acres > > of controlled burning occur than should (difficult not to > > exceed air quality regulations), and running it as > > bio-fuel through an efficient energy generation plant was > > a solution being sought in Northern Arizona. Finding the > > balance between constant, consistent, regular source in > > the amounts appropriate for the energy generated was the > > key, that and being located centrally to the source. The > > small wood fuels are abundant and burgeoning. > > -Don > > > From: [email protected] > > To: [email protected] > > Subject: [ENTS] Re: High elevation forest response to > > climate change and other factors > > Date: Tue, 2 Jun 2009 16:41:24 -0400 > > > Don, > > > How do you know that the current drought in the west is > > the worst since 600 AD? Tree ring data? > > > I would say that unnatural fire suppression has led to > > invading white fir regeneration and above normal ponderosa > > pine regeneration as well as much of the bark beetle > > outbreaks. Blaming it all on global warming is bunk. > > > Mike > > > -----Original Message----- > > *From:* [email protected] > > [_mailto:[email protected]_]* > > On Behalf Of* DON BERTOLETTE > > *Sent:* Monday, June 01, 2009 4:06 PM > > *To:* [email protected] > > *Subject:* [ENTS] RE: High > > elevation forest response to > > climate change and other factors > > > Lee- > > Yes, these instances are almost > > always not a single cause > > issue...in the case of higher than > > normal mortality of old-growth > > ponderosa pine forests on the > > North Rim at Grand Canyon, it was > > a combination of: > > 1) altered natural fire regime, > > 2) invading white fir > > regeneration, competing with > > 3) above normal ponderosa pine > > regeneration, > > 4) 15 years of drought (not seen > > this long or serious since 600 AD), > > 4) causing moisture/nutrient > > stress on large old ponderosa pines. > > Here in Alaska, I was around when > > spruce bark beetle began a run > > that seemed stoppable at first, > > but in retrospect, could have only > > been stopped by a succession of > > two or three cold winters...we > > never got them and some 90% of > > Kenai Peninsula spruce (and > > significant interior populations) > > were wiped out. > > I have had several conversations > > with Southwestern academics who > > are beginning to sense the > > migration of species to more > > appropriate latitudes, elevations. > > It's apparent that just a few > > degrees annual change in > > ... > > read more » --~--~---------~--~----~------------~-------~--~----~ Eastern Native Tree Society http://www.nativetreesociety.org Send email to [email protected] Visit this group at http://groups.google.com/group/entstrees?hl=en To unsubscribe send email to [email protected] -~----------~----~----~----~------~----~------~--~---
