Details of the
Hubbard Brook Phytosociology programThis page contains Tom's notes about the details of the phytosociology programming for the Valley plots. They are here as much for our remembrance of what we did as for the benefit of anyone else who needs to know the minutia.
There are a lot of quick notes:
1. Snags are "standing dead trees" without branches but with a bole left above dbh. Dead trees are "standing dead trees" which still have most of their branches.
2. "All live trees" includes healthy and sick trees. "All dead trees" includes standing dead and snags.
3. The intention of the sampling design was to only tag and record trees >10 cm dbh. However, there are 7 trees ranging from 7.4 to 9.8 cm dbh that were accidentally tagged and thus are a permanent part of the record in the 1995-98 data. These trees were not included in the calculations of our interactive program.
4. The program is written such that an aspect range can only be selected between 0 and 360, and cannot "wrap around" past zero (e.g. 270 to 90 will not work).
5. You should study the year-specific data documentation for the special details and access to the original raw tree by tree data.
6. There are several ways of selecting plots which are redundant, and all the various selection processes are here because the author was trying to learn how to create all these options. The answers should cross check - so if you select plot 44 in option 2 and or enter plot 44 under the single plot option you should get the same results!!
More detailed notes:1. There is some "fudging" in the calculations involved with filling out the 10 cm size class and care must be taken in selecting a diameter range that splits the 9.5 to 10.4 range (see Footnote 6). Since small tree data are not available for the Valley plots, this is not so much of an issue as with the some of the watersheds where you might want to enter a range of, say 5 to 10 cm. Using a lower diameter of 10 cm is fine so long as you understand that program automatically adds in an estimate for trees 9.5 to 9.9 cm dbh.
2. In designing the diameter distribution per hectare graph, again some "fudging" was necessary to even out diameter classes. The program lumps all the trees that belong in each 1 cm diameter class (e.g. 13.5 to 14.4 for the 14 cm class, 14.5 to 15.4 for the 15 cm class, etc.), and when run with the default size class choice of >10 cm dbh, the lower end of the range (10 cm) was already doubled to account for missing trees as explained above (and in Footnote 6). However, if the "select a diameter" option is used and the selected lower or upper diameter is an integer, then really only half of the diameter class for these endpoints is included in the calculation (e.g. 20 to 30 includes only 20.0 to 20.4 for the 20 cm class and 29.5 to 30.0 for the 30 cm class). So that the 1 cm classes on the ends of the selected range don't come up short, the program doubles the stem count for the lower diameter and upper diameter values (unless it is10, because this was already doubled earlier in the program). This doubling is based on the assumption that there will be about the same number of stems in either half of a 1 cm diameter class. It was assumed most users will enter integers in the "select a diameter class" option, so this only works if the entered value is an integer. If the selected range is 19.5 to 30.4, nothing will be doubled, but because this choice includes whole 1 cm diameter classes (19.5 to 20.4 for the 20 cm class and 29.5 to 30.4 for the 30 cm class), the graph will be correct anyway. However, if the selected range is 19.8 to 30.1, nothing will be doubled and both the 20 cm and 30 cm diameter classes will look short in the graph (19.5 to 19.7 trees are not accounted for, nor are 30.2 to 30.4 trees). Therefore, it is recommended to use either integers or whole 1 cm diameter classes (X.5 to X.4) in the "select a diameter" option.
3. The Valley plots have not been categorized into vegetation zones as the watersheds have been. The "identify where a species is dominant" option allows you to more or less do this yourself, but the calculator is not programmed to then do the calculations for the resulting plots. To get results for just those plots, you must return to the program and select those plots manually in the "choose individual plots" option.
4. The following table includes tree species found in our vegetaion surveys.
# Letter code Acronym Common name Scientific name 1 sm ACSA Sugar maple Acer saccharum 2 ab American beech Fagus grandifolia 3 yb Yellow birch Betula alleghaniensis 4 wa White ash Fraxinus americana 5 mm Mountain maple Acer spicatum 6 stm Striped maple or moose wood Acer pensylvanicum 7 pc Pin or fire cherry Prunus pensylvanica 8 -- Choke cherry Prunus virginiana 9 bf Balsam fir Abies balsamea 10 rs Red spruce Picea rubens 11 pb White or paper birch Betula papyrifera 12 ma Mountain ash Sorbus americana 13 rm Red maple Acer rubrum 14 eh Eastern hemlock Tsuga canadensis 15 uk unknown, used for unidentifiable rotten snags 16 qa Quaking aspen Populus tremuloides 17 bc Black cherry Prunus serotina 18 jb Shadbush Amelanchier sp. 19 ba Big-tooth aspen Populus grandidentata 20 -- Willow Salix sp. 21 -- Alternate-leaved dogwood Cornus alternifolia 22 -- Cherry (unspecified) Prunus sp. 23 bw TIAM Basswood Tilia americana 24 bla FRNI Black ash Fraxinus nigra 25 gb BEPO Gray birch Betula populifolia
For any further questions, please email thomas.siccama@yale.edu.
Web page created November 2003
by Thomas Siccama and Ellen Denny