Cross sections on the rise Robert Leverett Dec 21, 2005 13:09 PST
 Will, Jess, Don, Lee, John, Ed, et all:     From my 4th floor office window on the Mercy Medical Center Campus in Springfield, MA, I can look directly across to a gorgeous pin oak tree that is 80 yards away. It is 90.4 feet tall, has a CBH of 12.1 feet, branches at 23 feet above its base, and has a maximum lateral crown spread of an impressive 104 feet as determined from a distance. I suspect that the actual is between 95 and 100 feet. I'll confirm that tomorrow.      A level gaze from my chair brings me to 45 feet or half way up the tree - a perfect vertical vantage point. I can clearly see the spread of limbs in the morning (the tree is to my west) and I can count most of them since foliage no longer obscures vision. I think I can see the limbs through an arc of about 330 degrees. I'll inspect the remaining 30%, or whatever it turns out to be, from the ground.    A novel thought occurred to me this morning. With the RD 1000 I could model the tree pretty thoroughly from my office, excepting limbs in the hidden 30%. I could calculate the total cross-sectional area of wood at different heights as a kind of profile. Staying with cross-sectional area at different heights would free me from trying to calculate limb lengths. Of course, the cross-sections wouldn't provide the whole picture and wouldn't yield volume, but the exercise would be interesting.    So I plan to arrive at my office early tomorrow AM and spend about an hour taking measurements of the limbs at 45 foot level with the RD 1000, using its magnifier. If I'm successful tomorrow, on Friday, I'll drop to 30 feet and do another cross-section. Next week, I'll do one at 60 feet. I'll then model from 0 to 23 feet. No problems there. The section between 23 and 30 feet is the confusing area where the limbs begin to emerge until their separation is visibly distinct from my vantage point. I'll save that section for last. Any suggestions?    Lee, did you do anything like this when you analyzed crown area in your studies in the Porkies? Bob Robert T. Leverett Cofounder, Eastern Native Tree Society
 RE: Cross sections on the rise Robert Leverett Dec 22, 2005 06:12 PST
 Ed, Yes, I'm unquestionably obsessed. Last night Will Blozan and I discussed the idea of computing the cross-sectional area of trunk and limbs at different heights. Will likes the idea. It is another way to assess how much wood exists at different heights. So we visualize the tree cut by horizontal planes at a set of chose heights and calculating the area of the wood that intersects each plane. Near the base of the tree it is all trunk. Then perhaps a split trunk, and then trunk and limbs or all limbs. More later. Bob
 Re: Cross sections on the rise Lee E. Frelich Dec 22, 2005 11:25 PST
 Bob: No, I didn't do wood cross sectional area at different levels, and I haven't seen any such analyses before--so your analysis will be unique. What we did do, is cross sectional area of the crown at different levels, to calculate the amount of space the tree occupies, so that we could get the relative amount of area and volume each species occupied in the forest.  The oak tree I am going to see next time I visit Sweden is thought to be 1000 years old, and has appeared in various historical records for at least 600 years. It has a CBH of 45 feet, and DBH of 14 feet.  Lee
 Re: Cross sections on the rise Jess Riddle Dec 22, 2005 17:33 PST
 Hi Bob, Your exploration of total cross-sectional area at various heights sounds intriguing. I remember Will Blozan mentioning the idea to me a several months ago, and I immediately thought the idea fascinating although I couldn't see any direct applications. I'm looking forward to reading about your results, and what conclusions you come to through your exploration. Jess Riddle
 First look Robert Leverett Dec 23, 2005 07:18 PST
 Jess, Will, et al:     The idea for computing the cross-sectional area, which I'll here after refer to as CSA was in part an attempt to concentrate on what I could measure easiest. I was very pleased when Will told me he had been thinking about it. Handling complex limb structures requiring modeling of 15 to 20 main limbs and perhaps as many secondary branches is a daunting job. To do it justice, limb modeling must await the new instrument, i.e. the reticled microscope-telescope. The Rd 1000 is just not accurate enough to handle complex limb structures.     Passing several horizontal planes through the tree and calculating the CSA of wood that emerges through each plane would give a 3-dimensional view of the tree's architecture that might prove highly valuable to characterizing differences among species and how the young trees of a species differ from the old growth forms. Well, so much for my justifications.     My first crack at the pin oak visible from my window has yielded some crude measures. They are summarized in the table below. Hgt = 90 CBH=11.8 Max Spread = 97 Hgt-ft No Trunks/limbs CSA-ft^2 % of Hgt % of 2.5-CSA 2.5 1 12.57 3% 100% 4.5 1 11.09 5% 88% 48 12 8.34 53% 66% 65 7 1.67 72% 13% 90 0 0 100% 0%          As time goes on, I'll refine them and we'll see how the numbers change with the refinements. For example, I measured the tree with my D-tape this morning. It's 11.8-foot CBH (45.1" DBH) is at variance with what I got with the RD 1000 with magnifier which could be read as either 46.7 or 47.4. Had I not measured the tree with the D-tape, I would have chosen 47.4". So it appears that the magnifier produces high numbers on large diameters at long distances. This is what I first discovered in early tests with the magnifier. The absolute magnitude of the error does not carry over to small diameters. Otherwise most of my limb measurements would disappear. Now you see them, subtract a 1.3" correction factor, and now you don't. Bob Robert T. Leverett Cofounder, Eastern Native Tree Society
 RE: What Difference Seven Years? Robert Leverett Dec 27, 2005 12:51 PST
 Ed,     BTW, implementing the horizontal slice concept to profile the cross-sectional amount of wood in a tree at different heights is presenting some challenges. From a single vantage point, locating the spot on different trunks/limbs/branches that are at the same height requires a lookup table and some experimentation. I will soon send you and others an Excel table showing my approach and soliciting ideas for improvement. Bob
 RE: Cross sections on the rise Roman Dial Dec 28, 2005 02:48 PST
 Jess and Bob, One application of cross sectional area by height would be the computation of leaf area index by height, giving a vertical profile of foliage density. Roman
 RE: Cross sections on the rise Robert Leverett Dec 28, 2005 07:00 PST
 Roman,    Does this suggest that the foliage density could be predicted by the cross-sectional area of the wood at any specified height - perhaps with an offset? This would seem to be the case high in the canopy, but it wouldn't apply at lower heights. Would you shoot for the middle of the canopy to apply the technique?    From a practical standpoint, the amount of work needed to identify the spots on many limbs that are at a prescribed vertical height above base is daunting. The features of the RD 1000 that allow one to quickly scan up a particular height applies only along the vertical line which has at its horizontal distance, the value set into the RD 1000. There is no way to quickly compensate as one moves from limb to limb unless shooting at eye level. One can alternately shoot sufficiently low and high on the limb to encompass the point that is at the prescribed height. One can gradually zero in on the spot, but it isn't just a point and shoot proposition. So computing the cross-sectional area of wood at a prescribed height must remain a labor intensive job. Oh well.    One long term use of this kind of measuring might be to develop characteristic profiles for different species in open and closed growing environments. I don't know. At this point, I'm more concerned with just developing the measuring technology and leaving it up to the Lee Frelichs, Bob Van Pelts, Roman Dials, Tom Diggins, Don Braggs, etc. to figure out how to make good scientific use of the data. Bob
 RE: Cross sections on the rise Robert Leverett Dec 28, 2005 07:00 PST
 Roman,    Does this suggest that the foliage density could be predicted by the cross-sectional area of the wood at any specified height - perhaps with an offset? This would seem to be the case high in the canopy, but it wouldn't apply at lower heights. Would you shoot for the middle of the canopy to apply the technique?    From a practical standpoint, the amount of work needed to identify the spots on many limbs that are at a prescribed vertical height above base is daunting. The features of the RD 1000 that allow one to quickly scan up a particular height applies only along the vertical line which has at its horizontal distance, the value set into the RD 1000. There is no way to quickly compensate as one moves from limb to limb unless shooting at eye level. One can alternately shoot sufficiently low and high on the limb to encompass the point that is at the prescribed height. One can gradually zero in on the spot, but it isn't just a point and shoot proposition. So computing the cross-sectional area of wood at a prescribed height must remain a labor intensive job. Oh well.    One long term use of this kind of measuring might be to develop characteristic profiles for different species in open and closed growing environments. I don't know. At this point, I'm more concerned with just developing the measuring technology and leaving it up to the Lee Frelichs, Bob Van Pelts, Roman Dials, Tom Diggins, Don Braggs, etc. to figure out how to make good scientific use of the data. Bob