MA Data Set   Robert Leverett   May 29, 2007 06:34 PDT  ENTS,     On Saturday evening I started to examine my Massachusetts tree data with the intention of testing its relevance for teasing out species height patterns and also to look for under-measured species. Twenty-five species were chosen. The following table reveals the current state of my Massachusetts data for the selected 25 species. Species abbreviations are WP=white pine, TT=tuliptree, WA=white ash, HM=hemlock, ABW=American basswood, CW=cottonwood, AB=American beech, SY=American sycamore, NRO=northern red oak, BC=black cherry, SM=sugar maple, BTA=bigtooth aspen, BLCT=black locust, AE=American elm, RM=red maple, BB=black birch, WO=white oak, BO=black oak, SVM=silver maple, PO=pin oak, YB=yellow birch, BW=black willow, GA=green ash, BNH=bitternut hickory, HH=hop hornbeam Species Avg Hgt Township Avg Cir Township # Townships Tot # trees Avg Hgt All Impact WP 124.20 9.90 32 653 134.70 MTSF TT 113.60 10.50 18 128 116.90 RSP WA 112.20 7.70 18 253 124.10 MTSF HM 108.30 7.70 19 169 109.10 ABW 105.60 6.20 6 29 111.40 MTSF CW 105.00 9.90 25 178 107.10 AB 105.00 7.30 8 41 107.00 SY 104.60 13.30 31 110 106.10 NRO 102.50 9.80 21 172 105.20 BC 101.20 8.20 10 68 106.50 SM 100.90 9.00 15 153 109.90 MTSF BTA 99.00 5.00 5 25 109.70 MTSF BLCT 98.80 7.10 7 18 99.10 AE 98.70 12.20 4 8 98.10 RM 95.00 6.90 13 87 105.00 MTSF BB 93.70 6.30 15 50 98.40 MTSF WO 93.70 9.20 10 34 94.50 BO 92.90 10.20 7 9 93.40 SVM 92.80 14.90 14 65 97.10 PO 92.50 10.40 5 10 96.30 YB 86.00 6.40 9 36 89.90 BW 73.00 18.90 5 6 74.40 GA 99.30 6.90 7 11 99.70 BNH 109.30 5.50 7 34 113.50 MTSF HH 66.60 3.10 6 14 62.50 MTSF Total 2360       Relative to the whole, looks like I've overdone it on one species, i.e white pine. But beyond my deniable attraction to the great whites, the data set prompted me to ask what have I really captured – if anything? For example, is the computed average of 124 feet representative of the average of the tallest white pines in the townships of western Massachusetts? Remembering that the 124 is the average of the separate township averages, this average of averages for the white pine is interesting to follow. It will likely go down as more towns in the eastern half of Massachusetts are added where 120-foot+ white pines are less common. But truth be teased out, I’m probably not after broad averages and after thinking about the average of averages by species, a second approach seemed to make more sense.       In the table, the townships are weighted equally even though some townships are barely represented in terms of the number of trees measured. That is problematic. But when the heights of all the Massachusetts pines are averaged without reference to township (no weighting), the average jumps to 134.7 feet. What is the reason? The 10-foot jump reflects the impact of the large number of pines measured for MTSF, Ice Glen, and the Bryant Homestead. That seems very biased. However, if we take the single tallest pine in each township and average just the maximums, interestingly, the average goes to 135.3. This last average (average of township maximums) provides a good feel for the distribution of the individually tall pines across the Massachusetts landscape. What does this tell us about the growth performance of the species? Gotta think about this one a while.       Interestingly, the tuliptree shows up in the data as the tallest hardwood when working with the township averages. This surprised me. I thought the white ash would claim first spot among the hardwoods because the maximum heights of the white ash in Massachusetts exceed those of the tuliptree. The super ash trees of MTSF, MSF, and Ice Glen skew the average when all ash heights are averaged. Similarly, Robinson SP skews the tuliptree average when all trees are weighted equally because of the large number of tall tuliptrees that have been measured in Robinson. Interestingly, the average of the maximum heights by township for the tuliptree is 119.7. The corresponding average for the white ash is 118.1. That's close enough for a healthy competition.      The American sycamore profile is one of the best in terms of representing what one encounters across the landscape. Big scyamores are commonly encountered and most of the big ones are in the 100 to 110-foot height range. Slender sycamores growing in stiff competition are commonly between 111 and 120 feet with a few in the 121 to 130-foot range. Actually, I have measured only one tree over 130 feet. The average of the township maximums is 109.9 feet. The sycamore and cottonwood are locked in close competition. Bob Robert T. Leverett Cofounder, Eastern Native Tree Society   Home