Catching up on several topics

General discussions of measurement techniques and the results of testing of techniques and equipment.

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dbhguru
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Catching up on several topics

Post by dbhguru » Mon Nov 21, 2022 10:31 am

NTS

Over the last 6 years, I’ve been preoccupied with developing tree volume-biomass predictive models for several climate scientist friends and evaluating models that are already out there. Has it ever been an education! In addition, I’ve been trying to shine a spotlight on rampant misinformation about tree growth rates in terms of carbon sequestration. To this end, I’ve not been able to determine the original source of the truly misleading statement that a mature tree sequesters 48 lbs annually of CO2. One might argue that the Internet is loaded with misinformation, so why get disturbed about one more piece? The reason is that the statement is being used by people who seek to minimize the role of trees in combating climate change. Others push the importance of planting new trees at the expense of protecting mature ones when the latter is by far the more important strategy. Of course, there is need for both, but if big pulp, paper, and biomass companies can focus our attention on planting young trees, we won’t happen to notice when they slaughter entire landscapes of merchantable trees. Are we surprised?

Several sources attribute the 48-lb sequestration rate to the Arbor Day Foundation. American Forests has regrettably parroted the claim, despite my best efforts to dissuade them. But regardless, it is a ridiculous understatement for the performance of a mature tree and can be refuted by existing sources of information, including i-Tree, many volume-biomass models, the U.S Department of Energy, and simple common sense. Mature eastern trees that form fairly high canopies (oaks, maples, pines, hickories, ashes, etc.) can easily sequester between 150 and 350 lbs of CO2 per year.To talk about 48 lbs for West Coast behemoths is beyond ridiculous.

The most outstanding eastern performers can exceed 600 lbs into mid-to-late maturity. I won’t claim that true old growth specimens continue high rates, but well above the 48 can be achieved by an age of 40 to 50 and persist for another hundred years. So, why would an ostensibly tree-qualified organization put out or parrot such misleading information? I have a few ideas, but would appreciate hearing the thoughts of NTS members.

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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bbeduhn
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Re: Catching up on several topics

Post by bbeduhn » Tue Nov 22, 2022 9:26 am

Bob,

That is important work you are doing! Just like with accurate height measurement, misinformation spreads far more readily than accurate information. My daughter learned how to measure trees and buildings in her seventh grade class. Which method? Naturally by laying out tape and using the tangent method. As we all know, it can be accurate but in most cases, at least with trees, it is not. The battle for truth should have been won long ago.

Brian

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MikeK
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Re: Catching up on several topics

Post by MikeK » Thu Nov 24, 2022 9:04 pm

Bob,

I'm new to this but I've heard a number of arguments going one way or the other. Some sources have claimed younger forests sequester more carbon, at least at first, until they start to thin. Others have touted mature forests sequester far more in their root systems.

I'm familiar with the type of measurements you guys are doing here of above ground volume (although admittedly I don't think crown volume would be easy to estimate), but how do you estimate the volume of root systems? And on that particular note, I would assume different root systems store carbon in different volumes.

I would also assume a very important measure is the amount of trees that any given stand loses to natural disturbance, how long that carbon is left stored on the forest floor before it is completely oxidized, how long it takes for new trees to fill the gaps, and what rate they are absorbing carbon. The dynamics of this problem seem a bit staggering to estimate. It seems like it would be much easier, and convenient to measure and calculate second growth from clear.

I'd also be curious to know, or if anyone has estimated the amount of carbon that could be sequestered if we forested available land to the maximum level and how that might compare, fractionally, to the amount of hydrocarbons and coal (1000's of generations of forests) we've released.

Any sources would be appreciated.

I will say, whatever the estimates are I'm always in favor of mature, structured forests for a multitude of other reasons and although I don't deny climate change, I don't think I could be swayed away from that as a potential solution (if, in fact, second growth was a more effective system of carbon sequestration).

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dbhguru
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Re: Catching up on several topics

Post by dbhguru » Tue Nov 29, 2022 12:26 pm

Mike,

Lots to talk about. It is not too difficult to compute and compare growth rates of young versus mature trees when apples to apples comparisons are being made. Since you've asked, I'm willing to delve into the mechanics to whatever extent I can. I'm computing these days like mad, supporting several climate scientists who want to get down to the tree and stand level. Most of their analysis ends up on large landscape scale and depends on a lots of computer modeling that greatly varies in the returned results.

I'm happy to begin an extended discussion on carbon sequestration by trees based on my research and that of my colleagues if you are interested, But I'll offer a brief overview of what I've learned to date.

1. There are many tree biomass models that have been developed over the past 30 years or so by the U.S. Forest Service, the Canadian Forest Service, European counterparts, academics in several professions, and professionals working for both industry and conservation groups. Much of the research coming out of the U.S. Forest Service is very good, but different models lead to fairly widely varying results. I spend a lot of time comparing models and understanding their underlying assumptions. Most of that detail is lost when they are quoted in research papers by others. Opening the hood and looking at what is beneath is a real education.

2. Young forests do grow fast, but they don't accumulate much biomass for several decades, and eventually they aren't young forests any more. Individual trees are on one set of growth curves while stands of trees are on another. Of course, it is always species, site specific.

3. Management can increase growth rates of individual trees, but where cutting is heavy, the forest is always being returned to an earlier state. The carbon story of short stand rotations is one of continual loss of carbon. Management on that plan is never carbon neutral. wood products interests really feed the general public a line when they talk about how well young forests do.

4. The amount of carbon in the roots of a tree relative to that above ground is usually cited as about 20%. I use 15%, preferring to err on the conservative side. We don't get species specific with respect to root carbon. Jut a gross add-on.

5. So, how would we compare carbon both accumulated to a point in time and annual growth rate for a species? We can profile the growth of say a white pine that reaches a specified set of dimensions and show when it gained the most carbon. Of course, to be complete, you must factor in decay rates and they vary greatly. However, I've done a mountain of these comparisons and have it down pretty well, and am willing to share the methodology.

If you want I will begin by sharing predictive species volume-biomass models with you. Let me know if you'd like me to do this?

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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MikeK
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Re: Catching up on several topics

Post by MikeK » Tue Nov 29, 2022 2:51 pm

I'm certainly interested in reading whatever you want to share. I'm an engineer, no calculation can scare me. I've been combing through a number of studies on this site - particularly the OLDLIST and concurrent studies. I'm in the process of reading through most of the NY reports, and although most leave me with questions, I don't want to respond and revive all of these old threads, so I'll curb my enthusiasm the best I can.

I had been pondering what could be done with all the data that has been collected by this group - and of course this seems like it could be inline with that (carbon sequestration). I also thought of some other things such as height/girth/age limitation of species based on ecoregion. That seems like it could fit well into speciation distribution, and thus carbon modelling.

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Re: Catching up on several topics

Post by dbhguru » Wed Nov 30, 2022 7:33 pm

Mike,

Attached is the first of what could be many Excel workbooks containing volume-biomass tree growth models. It is for white pine only, and implements a model I call FIACOLE (Forest Inventory and Analysis - Carbon On Line Estimator). It is the best among over a dozen mainline models. It averages within about 4.5% of direct measurement modeling of trunk volumes. The second best is 6.3%. The worst is 25.3%.

You interact only with the BioMass worksheet. The other two support BioMass. You'll see that by entering the DBH in inches and height in feet for a white pine, lots of returns are generated to include trunk biomass and volume and total above ground biomass and volume. The carbon and CO2 equivalents of above-ground biomass are also returned. Lots of other neat stuff.

In the yellow box, the original authors layout their methodology. It takes some background in forest mensuration/forest biometrics to understand everything they're saying. I'll be happy to answer any questions you may have.

I have Excel workbooks implementing the FIACOLE model for 60 species. I also have implementations of 11 other models.

I'll leave it at this point for now.

Bob
Attachments
FIAvsNTSComparisonVolumeModelWPTEMPLATE-11-23-2022.xlsx
(27.23 KiB) Downloaded 11 times
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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MikeK
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Re: Catching up on several topics

Post by MikeK » Wed Nov 30, 2022 9:03 pm

Thanks for the sheet.

So what I'm seeing here is the models are using different degrees of input. FIA is using two parameters, the Jenkins using a single. And ENTS using 3 parameters. How do you measure and/or calculate the form factor?

I would expect this kind of modelling is going to be highly dependent on how much time you can allow yourself for measurement. I'd assume one would much rather just sample dbh (or girth) and not have to measure height. I'd also assume that the end model is not using the measurement of the entire forest, but rather some statistical sample of said forest. That then begs the question in my mind is it better to sample fewer trees in a plot with more measurements or sample more trees with simpler measurements. I'd assume this is the crux of the matter.

My question, beyond that of the form factor is does it take significantly more time in sampling to measure girth at two points (as you have outlined for comparison purposes) and height at two points, say the peak of the crown and the height to branches i.e. separate crown from stem?
Last edited by MikeK on Wed Nov 30, 2022 9:47 pm, edited 1 time in total.

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Re: Catching up on several topics

Post by MikeK » Wed Nov 30, 2022 9:30 pm

Oh, the other thing I got sidetracked about asking about was using growth rates to compare old to young forest. Are there any calculations of this? That seems like a fairly straightforward calculation if you can estimate height growth and I know there are USDA models of this for second growth 0-50 years of age. Core sampling and analysis seems like a good place to look to model overall growth rates of old trees, then simply applying the basal area to each stand should give an estimate of accumulation, or reduction in biomass.

Also I have to say, as an addendum to my last post I spent a good deal of my past career measuring and modeling mechanical systems - structural, dynamics and systems levels. There was always a lot of question in my mind as to how much effort one put into a model, especially early on. It always seemed to me, that no matter how good my model was, it was never going to completely predict my measurements. And my measurements, no matter how many or how good, always had certain limitations - in accuracy, precision, ease of implementation, time and cost to conduct. I never did any rigorous study on this, but in the end I generally had a good feel for how repeatable the measurements were and how well any given model might correlate. We generally did not err in this way, but I always felt it was better to take more measurements than to spend more time on models. The models could give a lot of insight into a given system, but not always in a way that wasn't easier just to measure. Sometimes I feel we were stalled on calculations and modeling when simply building something (or in this case, measuring something) was a better use of time and money.

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Re: Catching up on several topics

Post by dbhguru » Thu Dec 01, 2022 8:52 am

Mike,

Lots to cover here. I'll chip away at it.

There are actually many, many volume models that have been developed over time to predict commercial stem wood (from a 1-foot stump to a 4-inch outside bark diameter). No bark, just wood. Before the growth of the biomass market, foresters weren't interested in bark from an economic perspective. Many of these early models had additional variables such as crown length or crown volume, site index, diameter at root collar, stand basal area, etc. These fine-tuned models were applied very locally. But along with these fine-tuned models, there are plenty that are crude. Viewing from afar, the range of model sophistication represented in the FIA DB has always been very wide. So, large databases from multiple sources almost always include data from the crude to refined models. In addition, many trunk volume models were developed on young plantation forests with well behaved tree forms. You can't extrapolate very far with those models.

Beyond the local models, there are volume-biomass models designed for a geographical region or entire range of a species. These are the models that get the attention and carry the big names among Forest Service mensurationists, silviculturists, and forest biometricians. I use 12 of these models, comparing them against one another. My goal is to identify which ones work best for a particular species and often for a limited DBH range (and which ones don't work at all).

Models that estimate height for plantations can be pretty good, but very seldom do these models work on wild forests. They just don't because the growing conditions are very different. In addition, most of the raw data used in these models were collected using tape and clinometer methodology with all that methods risks.

Modeling growth rates for old trees is very site dependent. More on this point later.

Gotta run, now. I'll try to answer more questions later, including the form factor and its origin.

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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dbhguru
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Re: Catching up on several topics

Post by dbhguru » Fri Dec 02, 2022 9:10 am

Mike, et al.,

Attached is a discussion of trunk form factor. Among some forestry circles form factor isn't used much any more. But it is an extremely useful tool for estimating volumes for straight-trunked conifers and young hardwoods that still exhibit apical dominance.

Bob
Attachments
Mike&FormFactor.docx
(274.29 KiB) Downloaded 12 times
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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