Details of the
Hubbard Brook Growth rate programThis page contains Tom's notes about the details of the growth rate 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 does not yet exist a page describing the general process of acquiring tree ring data, so here is a brief summary: Cores are generally taken from a tree with an increment borer at a height of about 1.4 meters (a.k.a. "breast height") on the bole. In most of our samplings at Hubbard Brook, they are taken from a random spot around the tree rather than from a specific face (e.g. the south-facing side). Once out of the tree, cores are stored in drinking straws for safe keeping. We are careful to keep the bark (which often breaks away) from each core to convince ourselves we have the whole core and are not missing a few of the first rings that broke off with the bark. Back in the lab the cores are dried, mounted and sanded to expose the rings. Measuring is done under a dissecting microscope with an eyepiece reticle, each measurement converted according to the magnification factor in use. Starting with the year the core was taken from the tree and assuming one ring per year (generally we think we can identify which are false rings and ignore them), each successive ring is assigned the next year back in time and its width measured until the rings are no longer clearly discernable. One missed ring means the years are off and any sort of correlation analysis is meaningless. Therefore, once we come to a ring we are not sure of, we stop taking measurements. Hardwood trees that have had slow growth and narrow rings can be very hard to read and sometimes we can only read back a few years. If cores are taken during the growing season, the first ring is not complete and is therefore not used in analysis.
Some quick notes:
1. Most tree cores in this dataset were taken from live trees, although there are a few from dead trees and snags. Only cores from live trees are included in the calculations of the interactive program.
2. 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.
3. Tree rings were measured as far back as they were discernable on each tree core. Sometimes this means there are only a few readable rings. If a tree does not have enough measured rings to cover the requested number of years to include, then the tree is not used in calculation.
4. Since this dataset includes data collected over four years, tree cores were taken in different years and therefore the measured rings do not start on the same year for each core. We decided not to write the program to pick out rings from specific calendar years, but rather to use the last X years for each core (X selected by the user). Be aware that this is not the same set of calendar years for each tree.
5. Elevation in the "radial growth by elevation" graph is of the plot center for each tree's plot and not the elevation of individual trees.
6. 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).
7. You should study the year-specific data documentation for the special details and access to the original raw tree by tree data.
8. 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!!
# 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 December 2003
by Thomas Siccama and Ellen Denny