Another opportunity to participate in carbon

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

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JHarkness
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Re: Another opportunity to participate in carbon

Post by JHarkness » Sun Mar 10, 2019 6:42 pm

Bob,

I'm curious, was this strictly done by modeling individual or a few individual trees in a stand and averaging crown area and volume to calculate stand volume per acre? Or was any of this done by establishing fixed sampling plots and modeling everything within each plot? I have the suspicion that averages from the former method could vary immensely from the actual stand volume with subtle changes in stand composition, structure, etc. that may not be visually discernable.

I'm also curious if this is limited exclusively to overstory trees as the crown area measurement would imply? One point to add to the table if that is the case, 40 year old forests often haven't had enough natural disturbance to allow for much regeneration, and what is present will likely be seedlings and small saplings, on the other hand a mature second growth forest or old growth forest will have had that disturbance and is much more likely to have a much more diverse structure with many midstory trees which may have a collective high volume. Quite a lot of carbon can also be held sub-canopy but not be reflected by including only overstory trees. Some old growth forests I've seen remind me of a young forest with isolated mature overstory trees, they could have the same stem density as a 40-year old forest with the added benefit of high volume individual trees.

Apologies if you've already gone over this and I'm missing something,

Joshua
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dbhguru
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Re: Another opportunity to participate in carbon

Post by dbhguru » Mon Mar 11, 2019 9:29 am

Joshua,

The data fed to the model for each scenario incorporates a bit of everything and in the end is an expression of my experience spread over many actual sites. Ion its present form, it's a mind exercise as opposed to a scientifically designed field experiment. We can get pretty good at estimating how fast suppressed and dominant pines grow on different sites based on what is happening at points in time. However, when we move from individual trees to the stand level with topography, natural disturbances, site history, etc. all thrown in, it's less and less clear where the averages lie. Of course silviculturists control the variables so they can predict results.

I was talking to my friend Don Bertolette last evening and he reminded me that in controlled plantings of conifers, it is a common practice to plant seedling 9 feet apart. That represents 691 stems per acre or exactly 100 more than the average I used. Lots to consider.

Bob
Robert T. Leverett
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Don
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Re: Another opportunity to participate in carbon

Post by Don » Mon Mar 11, 2019 8:25 pm

Bob-
I might add that the planting matrix could run from 7-10' spacing, depending on the species...which I suppose also would have variable carbon sequestration rates...And the use of 30-40 year old stands presumably indicates at the very least, second-growth, and when dealing with industrial timber company properties that have cut on MAI's of 23 years to maximize their economic advantage, do you get more or less carbon sequestration as you go through repeated 23-year rotations?
-Don
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Re: Another opportunity to participate in carbon

Post by dbhguru » Tue Mar 12, 2019 10:43 am

Don,

I fear that there are many ways to approach this issue that require data that I don't have. But starting simply, let's take say a 25-year old white pine stand that grew from a field and follow it. We assume nothing else is growing but pines. The amount of carbon in the trunk of a dominant pine at that age would be around 9 to 12 ft^3. A subordinate pine would be 2 to 3 ft^3. Intermediate pines would 4 to 8. If we use the stems per acre from the FIA data, we would have 1108/acre. To keep it simple, let's arbitrarily partition the stems 33-67 among dominant (11 ft^3) and subordinates (2.5 ft^3). So 365.6 * 11 + 742.4 * 2.5 = 5878 ft^3. Let's assume at 25 years 80% are alive since the reduction in live stems is dramatic. This gives us 4702 ft^3. How does this fit with approaching density from crown spread? if we assume that each stem sequesters the space occupying a circle with an 8-foot diameter, we would get 871 stems. If we partition the stems as previously done with 80% being live, we'd get 3697 ft^3. Call it 3,700 ft^3. I think this is much more likely. The mass would be 44.4 short tons/acre or about 22.2 tons of carbon.

At 150 years, the Trees of Peace have about 16,000 ft^3 in live pines per acre. If we add in 3,000 ft^3 for other species, we get 19,000 ft^3. If we consider that the non-pine stems have an average density of 40 lbs/ft^3 versus 24 lbs/ft^3 for pine, we get (16000 * 24 +3000*40)/2000 = 252 short tons versus 44.4 tons at 25 years. The ratio of current live stem mass to that at 25 years is 5.7 to 1 (252/44.4). The ratio of the age today for the Trees of Peace versus at 25 years is 150/25 = 6 to 1. This suggests that 6 full cycles of 25 years would produce 266.4 tons versus the 252, and is an affirmation of early young growth. However, and it's a big however, the durability of the wood in terms of holding carbon greatly favors the older trees since they are mostly heartwood. In addition, little can be done commercially to use 25-year old white pines. I think any arguments for rotating stands at 25 years wouldn't stand up in terms of wood durability (continuing to sequester the carbon), commercial viability, and certainly not long term standing carbon stocks.

However, it isn't clear how this approach fairs as we go from 25 to 50 years and beyond. We can say that individual trees gain most of their volume after 50 years, but trading off large numbers of small stems for a diminishing number of larger ones requires all the factors to come into play.

Thoughts?

Bob
Robert T. Leverett
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Re: Another opportunity to participate in carbon

Post by Don » Tue Mar 12, 2019 9:43 pm

Bob-
Lots to chew on there...one of the things I was supposing was that each successive "full cycles of 25 years" would deplete it's ecosystem and successively diminish to eventually a significant extent. The only commercial enterprise that would consider this would be either a mill that chewed forests to make paper, and cared only for long enough fiber at a minimum to make toilet paper, or alternatively, those wishing to strip fast growing young stuff for biomass to fuel generators.
Seems like the idea is not to constantly consume our forests for short-term gain, but to store carbon on a long rotation basis...but I've strayed from your point, haven't I ?!
I'll try again tomorrow!
-Don
Don Bertolette - President/Moderator, WNTS BBS
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Grand Canyon National Park

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Re: Another opportunity to participate in carbon

Post by dbhguru » Wed Mar 13, 2019 12:00 pm

Don,

I think you are spot on. Repeated 25 year rotations pretty well spells doom to any ecosystem values. The carbon value plus the wildlife plus the genetic heritage of the flora plus the aesthetic plus, plus, plus ..... versus the totally controlled environment of a crop.

Bob
Robert T. Leverett
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Re: Another opportunity to participate in carbon

Post by dbhguru » Mon Mar 18, 2019 10:59 am

Ents,

The challenge to climate scientists these days is determining the contribution of forests of different species and age classes to the carbon pool. We've seen heavy emphasis on tropical forests. The swing now is toward temperate forests and ones in younger age classes according to one school versus the older classes in another. For my very small roll in these discussions, I've carved out a little piece of white pine real estate to study. The personal challenge has been to follow the carbon sequestration through stand development from early fast growth to full maturity. We start with many seedlings, maybe 1,500, and from there drop to around 600 stems at 40 years and finally between 40 and 50 stems at 150 years. Can we trace the decline of stems and the growth of individual trees, keeping the carbon balance sheet up to date as we go? There are questions that I'm not in a position to answer. For example, what happens to the stems that die, i.e. how fast do they decay and what percentage of their carbon goes into the soil as opposed to CO2 into the air. My assumption is that the stems decay quickly since we're dealing with mostly sapwood. Some studies seem to conclude that returning carbon to the soil is a slow process, so that a reasonable conclusion is that most of the growth in young stands that a re in the process of self-thinning ends up back in the atmosphere.

The attached spreadsheet is a first attempt to balance stem density decline with individual trunk growth of surviving trees. I make no claims for it as to how well it profiles the standing live and dead volume win the Trees Peace at 40 years. I am curious as to what the rest of you think about the overall approach, and how we might improve it. What can we do at our level to make our best contribution?

Now to some details. A small white pine in our front yard, now 16 years old, has a 1.5 inch radius at 4.5 feet. That represents an annual increase of 0.09 inches. The radial growth at the base would be 0.14 inches. The tree has plenty of sunlight and no real competition. It is presently 20.2 feet tall. A dominant 115-year old white pine in our backyard has an average annual radial increase of 0.13 inches, taking its radius at 4.5 feet. That surprised me. Then I took the Jake Swamp white pine at 160 years of age at 10.83 feet in girth. The average annual radial growth is 0.13 inches. Doing a similar calculation for the larger, older Thoreau pine in MSF yielded an average annual radial growth of 0.13 inches.

The period of very fast radial growth occurs from 20 to 40 years if current forestry thinking is correct, at least as averages go. If we allow for 0.14 inches per year for 16 years and 0.3 inches for 24, we get an average of 0.236 inches over 40 years. In the spreadsheet, I show 6 stems averages at an average of 0.25 inches per year. For giving the young trees the benefit of the doubt, I think that's plenty fast. I then show 44 stems at an average rate of 0.2 inches. This is approximately equivalent to 0.14 inches for 16 years and 0.25 for 24. Again, this takes care of fast growth for those stems that will be dominant at age 40 - I think.

The remaining stems show a trailing off in size. Many will die before 40 years. Column Q projects percentage of live stems at age 40. We have 277 live stems remaining. Intuitively, that seems like enough, and it includes all of the two largest diameter classes, and 85% of the third class.

This leads to 4,238 ft^3 of live stem volume at 40 years. I've run other scenarios and they yield between 3,000 and 5,000 ft^3. I'm feeling fairly confident in this range.

Compare the 4,238 to 17,050 ft^3 for all live stems at age 150. If we want to make a comparison on the basis of acreage, it would take 4 acres of 40-year old pine to equal the one acre of mixed species (15,550 ft^3 of pine and 1,500 ft^3 of other species). If we think of rotating a single acre, that acre would have to be rotated 4 times to produce the same volume as exists at 150 years. However, we can get only 150/40 = 3.75 rotations in 150 years. The carbon advantage goes to the 150-year stand, although not by a lot. However, to be truly comparable, the 4-rotation plan would need to hold onto the carbon from each rotation as long as the carbon in the standing live trees at 150. That is extremely unlikely. I expect most of the carbon from the 40-year old stands would be back in the atmosphere. Thoughts?

Note that I don't introduce a decay factor in the standing live trees, either the 40-year old ones or those at 150 years. Lots of variables.

Bob
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Robert T. Leverett
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Co-founder and President
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Co-founder, National Cadre

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JHarkness
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Re: Another opportunity to participate in carbon

Post by JHarkness » Mon Mar 18, 2019 12:14 pm

Bob,

It seems only logical that substantially less carbon is sequestered and stored in the soil in a young forest compared to an old one, and think about it, a major disturbance such as a severe stand-leveling wind event, clearcutting, clearing for pasture, etc. will partially or completely kills the roots of trees, herbaceous plants, as well as the mycorrhizae so theoretically it would take many decades for the forest floor to recover enough to allow for any serious carbon sequestration and storage. I would agree that the majority of the carbon in a young forest is being released back into the atmosphere as plant material decays.

Joshua
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Re: Another opportunity to participate in carbon

Post by dbhguru » Wed Mar 20, 2019 8:02 am

Joshua,

I would guess you are correct. One area we in NTS could investigate is stem density and companion basal area at various stand ages. Aggregate stem density data from the sources I've seen thus far typically don't include diameter distributions. The projections don't allow us to differentiate how different age and diameter classes are behaving relative to carbon sequestration. Consequently, it is not possible for us to determine if very high stem counts are overwhelmingly of stem diameters at two inches and less. A stem with a 2 inch diameter is likely to have a stem volume of 0.10 to 0.12 ft^3 or less. This means we could have 1000 stems in an acre and they would only add up to not more than 120 ft^3. By comparison, it would take only 35 to 40 six-inch diameter stems to give us 120 ft^3 in an acre. The last Excel workbook I sent provides us with a means of easily testing lost of scenarios, i.e. combinations of stems sizes based on radial and height growth assumptions. Why is this important?

I may be sticking my neck out here, but I think most of the carbon projections for forests come from sources that have a big financial stake in the managing of our forests over relatively short-term stand rotation strategies. Maybe they are right, but I have yet to be convinced. I'd like to see what we can do independently. We have limited resources, but a wealth of combined experience.

Joshua, I'm curious about stand densities, average stem size, total volume, etc. for the woods you own? You possess the tree-measuring skills needed to figure those things out. Maybe we could adopt your woodlands as one of a series of baseline sites for relating total stand volume to variables like age, diameter class, canopy height, species mix, etc. Might you be game for that kind of project?

Bob
Robert T. Leverett
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Re: Another opportunity to participate in carbon

Post by Don » Wed Mar 20, 2019 5:43 pm

Joshua-
It's taking me a long time to get my head wrapped around this carbon sequestration thing, and it seems it'll be awhile before I get a really good grasp on it.
That said, your comments of the 'world' after a disturbance, even stand clearing one, I think doesn't mean there is no carbon sequestered in the coarse woody debris, the roots alive or dying (oak roots sustain a lot of disturbance, look up advance regeneration of oak seedlings), and the duff and detritus of past senescence of 'carbon bearing plants'. In fact the more of this still going on, lends to a more resilient ecosystem, right from the start.

So given that we're not really starting from zero carbon at Day One after disturbance, and what 'ground borne' carbon still remains, the first twenty years can be amazing. I'd be interested in studies where that first twenty or thirty years' "carbon sequestration" was graphed on 'amount' over 'time'.

Bob and I were discussing this and he thought it would be difficult to know the age of trees (he was thinking of eastern hardwoods). I thought back to my school days when I took graduate level class called "Stem Analysis", where we selected a grand fir in the field, and brought it back into the Forestry Lab. We then took 'cookies' out at each whorl, and at each midpoint between the whorls. The whorls are a very good indicator of the grand firs age, once you applied a factor to address the time it took to put out that first whorl, after the seed (or seedling) germinated.

Next is perhaps trivia, but back then (and still it seems) I was fascinated with the perception that the tree was clearly (maybe only in my mind) a set of nested annual rings, that added on one ring with each new whorl. This is actually borne out by our examination of each 'cookie under a binocular scope, and 'watching the rings add on with each whorl', all the way up the tree. Being in the northern California coast, the tree had no years in which it didn't set annual growth rings.

Okay, I've rambled on, just wanted to add a little to the discussion...I don't know eastern hardwoods well, and wonder if there are cues that those of you who are arborists, or 'nerdy' enough to have puzzled over how to 'age a young tree' without poking an increment borer into it?
-Don

JHarkness wrote:Bob,

It seems only logical that substantially less carbon is sequestered and stored in the soil in a young forest compared to an old one, and think about it, a major disturbance such as a severe stand-leveling wind event, clearcutting, clearing for pasture, etc. will partially or completely kills the roots of trees, herbaceous plants, as well as the mycorrhizae so theoretically it would take many decades for the forest floor to recover enough to allow for any serious carbon sequestration and storage. I would agree that the majority of the carbon in a young forest is being released back into the atmosphere as plant material decays.

Joshua
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

BJCP Apprentice Beer Judge

View my Alaska Big Tree List Webpage at:
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