Hemlocks Still Abundant Despite Adelgid Infestation

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Lee Frelich
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by Lee Frelich » Fri Sep 30, 2011 9:54 am

Bob et al.:

I think the FIA is quite accurate at larger spatial scales--say the size of a county in northern MN, or half of MA. Most people don't appreciate the degree to which forest trends (in many variables such as species richness, tree mortality, species composition, etc.) can be opposite at different spatial scales. Its one of the most common reasons for people, and sometimes even scientists to be 'lost in space' without knowing it. Its only when one looks at a variable over several orders of magnitude of spatial scale that they can understand how the data behaves and what it means.

In this case the article appears to counteract local perceptions because the period of observation cuts off before the big increase in hemlock mortality in the southern Appalachians (1/5 of the FIA plots are surveyed each year, so that the picture of the forest from the data always lags reality by 5 years, plus the time taken to analyze the data and get something published), the area with the most hemlock volume is in northern places where the HWA has not arrived, and there are a lot of counties that are counted as infested (such as the county where Bob lives in MA), but where the infestation waxes and wanes from year to year depending on winter weather, and never quite builds up to a level that kills the forest. These counties counterbalance the ones where most of the hemlock has died, such as in the southern Appalachians. The study is not detailed enough or sophisticated enough to go into these details.

Lee

Joe

Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by Joe » Fri Sep 30, 2011 10:18 am

Lee Frelich wrote:Bob et al.:

I think the FIA is quite accurate at larger spatial scales--say the size of a county in northern MN, or half of MA.
Lee
Lee, I suspect norther MN is far more uniform than western MA- we have a great diversity of forest types here, elevation differences and some of the most complex geology in the world and thus great soil variability.

If only the state officials didn't make it seem that their FIA data is accurate to multiple decimal places, I wouldn't mind so much- but gee, one acre in 5,000 is practically worthless, IMHO.
Joe

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dbhguru
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by dbhguru » Fri Sep 30, 2011 10:46 am

Lee,

You've presented some mitigating information. Maybe at a very big picture level, FIA is useful and does provide valuable information. Maybe the real problem is the interpretation of the data, and consequently the interpreters. But, the methods used to gather the data are not uniform, nor are the gathers all well-qualified. I'll not go into that here.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

Joe

Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by Joe » Fri Sep 30, 2011 10:52 am

dbhguru wrote:Lee,

You've presented some mitigating information. Maybe at a very big picture level, FIA is useful and does provide valuable information. Maybe the real problem is the interpretation of the data, and consequently the interpreters. But, the methods used to gather the data are not uniform, nor are the gathers all well-qualified. I'll not go into that here.

Bob
but I might go into that (ha, ha)

The late Karl Davies studied FIA methodology- and, at least back a decade ago or so, it was mostly college students- and, they didn't measure tree heights which really pissed off Karl because he was a fanatic about measuring trees accurately, for the purposes of forestry- that is, to get a good measure of wood volume for commercial purposes- nobody was even in the same league as Karl on this subject. He said they were using a formula based on site index rather than actually measuring each tree height. And, he said the plots, all too often, were not well located to be representative- AND- the conclusions drawn by too many people, regarding the potential for forestry, was based on all this info from unmanaged and mismanaged forests, rather than what the forests can really do.
Joe

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Lee Frelich
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by Lee Frelich » Sat Oct 01, 2011 10:12 am

Bob and Joe:

FIA methods and implementation have improved a lot, especially in the last five years. I don't hesitate to use FIA data because I understand its many flaws, and like any good scientist, can extract conclusions that are not affected by those flaws. This is mainly a scale issue. With the density of plots FIA has, one can't characterize all of the forests in a small area like MA, especially if its broken into a lot of smaller forest types as you pointed out. You would need double or triple density or perhaps more than that.

In Minnesota, we can compare several different regions within the state using FIA data, each of which is the size of MA, with the variability within averaged out. Thats OK as long as one knows how that averaging affects what can be said about the forest. Your perception of Minnesota as not having diverse forests is a good example of how scale affects the way people think about the forest. You perceive it as averaged out over millions of acres of say, boreal forest, or northern hardwoods. However, in reality its not unusual to have a several different forest types with different hydrological and nutrient status within a few acres. A ten acre parcel in one of my study areas may include acid bogs (black spruce), moderate pH fens (tamarack), high pH fens (cedar), ash forests in ponds, multi-aged red and white pine on jumbled rocky terrain, jack pine on gently rolling ridge tops, black spruce lichen woodland on more exposed ridge tops, dwarf red maple-oak stands of ridge tops, and birch-aspen mixed with white spruce and balsam fir on mid slopes (and then there would be open bog, alder swamp, shrub carr, gravel bars, cobblestone bars, sand bars, sedge meadow, bullrush emergent marsh, water lily and submerged aquatic communities, 2 or 3 different cliff communities). The rest of the world perceives this as boreal forest with a few inclusions of other stuff.

Lee

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DonCBragg
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by DonCBragg » Tue Oct 04, 2011 8:40 am

For those interested, the FIA website (http://fia/program-features/) includes descriptions of how the samples are taken, including plot density across the US (about 1 plot every 6,000 acres) and how the data are collected. There has been extensive work done on characterizing sampling errors in the FIA data, and efforts have been made to improve quality in the information collected (hence, the shift to the new sampling design about 10 years ago). Not a perfect system, for sure, but one being used as the model for large-scale forest inventory across the world. Most of the field data are collected now by employees of state forestry agencies contracted with the US Forest Service--I suppose many of these are recent college graduates. They have all been systematically trained to meet measurement standards as required, and their work is checked by US Forest Service quality control staff. Disparage the samplers as you will, but remember that some of the most detailed studies coming out of universities are largely (if not exclusively) being measured by graduate students with varying degrees of training, and probably with almost no quality checking occurring... It is important to remember (as Lee has pointed out) that these data are not collected to tell you what a particular stand (or even landscape) may be experiencing, but large-scale forest trends.

Joe

Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by Joe » Tue Oct 04, 2011 9:02 am

but one acre in 6,000 is not much.... I realize that it's about cost- and it is what it is- the only thing that bugs me is when state officials claim the info is very, very, very accurate.... if they simply acknowledged that it's limited, then that's fine but they'll say things like "the average forest in the state is 67.345 years old and with 5.382 MBF, blah, blah, blah"- Drives me crazy to see that. Also, they claim most of the forest is even age and that's simply not true- most forests here have been cut over and over and at least once- so they're are clearly not even age- but they make that claim, then they use false logic to claim that "with all this even age forest we need more clearcutting to balance the age classes"- which is bullshit

they also stupidly claim that forest stop sequestering carbon at about 80 years so it's best to cut them for biomass, blah, blah, blah....

at one point I was more sympathetic to the anti biomass folks, but they lost me when they showed no interest in small biomass, which I've always liked and when it turned out that some of their strong supporters are heavily invested in fossil fuels

so now I'm more in support of small/medium sized cogen or thermal biomass, but I don't want stupid logic to support it- I want smart logic to support- I also think a fair amount of small clearcuts are fine but again, I don't want stupid logic to support it because using stupid logic makes the forestry world look stupid and thus they're going to lose such arguments to smarter people on the other side- what's needed is for forestry people to be smarter than people who don't like forestry

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dbhguru
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by dbhguru » Tue Oct 04, 2011 1:44 pm

Joe, Lee, Don, et al,

When I previously made a statement about qualifications of the samplers used for gathering FIA data, I don't mean to imply that I think they are all unqualified. I meant to say that they vary considerably in their qualifications and experience, and that some aren't well qualified. I have no doubt that others are. There are other situations known to me about shortcuts taken when doing CFI updates. I have no way of knowing if the situations about which I am aware are inconsequential at the big picture level. I bow to the expertise of others on this point.

I think what especially irks Joe and others are the interpretations made by public officials and past down to either the news media or to wood industry people who really misinterpret. The real problem may rest in invalid interpretation as opposed to the actual CFI plots and data.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

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gnmcmartin
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by gnmcmartin » Wed Oct 05, 2011 8:47 pm

ENTS:

I am not sure why some ENTS find this article, from the excerpts provided by Ed, so objectionable. The study is based on objective field measurements using a sampling method I may not completely understand. But I see nothing in this article that, to my understanding, in any way minimizes the devastating impact that the HWA has had, and will probably have in the future. Nothing in the article says that the HWA has not already devastated our hemlocks, and may not eventually wipe them out. The fact that their measurements do not show, yet, the statistical impact some may have expected, does not seem to me to be a statement that the overall threat is not, and will not, be exactly what we fear.

Of course there are on-going control efforts, but the article does not address their prospects, nor does it seem to me, either directly or indirectly, to minimize the need for them, or any others that might be developed and used in the future.

The article simply is reporting on what their objective measurements over the entire range of the eastern hemlock show. I don’t see the article as making any statement about the seriousness of the eventual impact of the HWA. The worst criticism I could make about this article, is that it is reporting a fact that may, in the larger picture of the problem, not be that important or significant, and which can be easily be misunderstood as it has been reported.

If I were in charge of such things, I may have simply held the data for some publication in another context at some future time. For me, at this point, the interest is very minimal. If I had sat down and thought about it carefully, with some maps of HWA infestations and their degree, at hand, I might have been able to guess at what they have found in the data. I am in a county where HWA has been reported, but in the last 20 years, the volume of hemlock on my timberland has increased "massively." But I live in fear that they will all be lost some time relatively soon.

--Gaines

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edfrank
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Re: Hemlocks Still Abundant Despite Adelgid Infestation

Post by edfrank » Wed Oct 05, 2011 9:08 pm

Gaines,

I know from photos taken in the 1910's -1920's Pennsylvania was pretty much cut over and large areas were totally devoid of any forest. The forest cover in the state has been generally increasing ever since. Hemlock grows in the understory in the shade. I would expect the overall numbers of hemlock is increasing even as the HWA affects the eastern half of the state. There are dozens of hemlock sprouts behind my house.

Ed

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"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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