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, Im 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