Dendrometers and Dendrographs
An excellent place to begin your tutorial about dendrometer bands is this excellent web site titled "Construction and Installation of Dendrometer Bands for Periodic Tree-Growth Measurements," by Bobby D. Keeland and Patricia Joy Young through the U.S. Geological Survey.
Band dendrometers have long been used to monitor and record the growth of trees on practically all time scales, from hourly to annually. The principle here is to gain a better understanding of the interactions between physiological and environmental mechanisms, so that we can better understand to which environmental factors the trees are generally responding. For example, did we notice that growth became enhanced during an especially cool week? Perhaps tree growth is more related to edaphic (soil) conditions than to actual rainfall amounts.
Dendrometers are usually bands that encircle the tree with some type of measurements indicated and either manual or automatic recording devices. They are very sensitive, and they can be very expensive. Dendrographs are similar, but they also provide a visual record of the tree growth over time via graph paper attached to a rotating drum. Modern instruments are sometimes attached to real-time data loggers, such that we can have actual hard data to input into spreadsheets or statistical packages for more detailed analyses.
Corporation specializes in the design and implementation of
recording dendrographs and dendrometers. Founded by Bill
Gensler, this company has been working with various members
of the Laboratory of Tree-Ring Research in Tucson Arizona to
measure various aspects of tree growth and electrochemistry
throughout the growing season. They can be reached at:
Agricultural Electronics Corporation
P.O. Box 50291
Tucson, AZ 85703-1291 USA
Recent years have seen a large number of companies now making band dendrometers of all types and all levels of instrumentation. I list some companies below and provide links to their web sites:
Matthias Dobbertin at the Swiss Federal Institute of Forestry Research provided information on two European suppliers of band dendrometers:
UMS-electronic: A compound of the dendrometer DIAL-DENDRO
(FOB Salzburg) with a compact sized electrical sensor with
automatic acquisition of data. The "tape" is an invar steel
cable with extremely low dependence on temperature; it is
gliding on a Teflon-net around the bark of the stem to
reduce friction and to protect against icing, resin and
callousing - suitable for trees from 15 up to 120 cm
diameter; the accuracy of measurement of the variation of
trees circumference is 0.01mm. The instrument is fixed at
the tree with 2 stainless screws; it is advisable to use a
drill for preparing the holes for the screws for to reduce
their influence on the tree. These are compatible with
datalogger, field-bus, handheld or PC data acquisition
boards, and time for adaption of the tape is about 6 - 8
weeks, shorter when installing during the winter (dormancy)
period. Their address is:
D6 Strain-Gauge Dendrometer: A recent developed instrument for continuous high-resolution and automated measuring of circumferencial variation of trees, by using electrical signals caused by resistance change on a thin metal strip used as a flexure device. Uses invar steel cable with extremely low dependence on temperature, gliding on a Teflon-net around the bark of the stem to reduce friction and to protect against icing, resin and callousing. Has easy mounting without screws or other fixings, and is applicable on trunks as well as on branches with small diameter. The accuracy of measurement of the variation of trees circumference is 0.005 mm, and is compatible with datalogger, field-bus, handheld or PC data acquisition boards.
I have installed both types of
dendrometer bands in 1997 on one of our study plots and
connected them to a CR-10 logger from Cambell Co. The
results so far are very promising for the hourly readings
with the strain gauge based dendrometer. The DIAL-DENDRO, on
the other hand, records the daily stem expansion well, but
reacts slow or not at all to daily stem shrinkage. So if you
are very interested in daily changes the D6 would be your
choice. The D6 has the other advantage that it needs not to
be screwed into the tree stem. It can, however, only record
changes up to 2 cm circumference changes before needing
adjustment. Prices a piece are now by 622,- DM for the
DIAL-DENDRO and 542,- for the D6 Strain Gauge. However, if
you order more you will get a discount.
Dr. Limin Xiong described how he used a "dendrometer band produced at the University of Melbourne. You could contact them to obtain more information. I have used their electric bands and a datalogger to collect data from Libocedrus bidwillii during my PhD study with Dr. J. Palmer in New Zealand.
School of Physics
University of Melbourne
Fax: 61-3-9347 4783
Regarding development of band dendrometers, Kari Mielikainen of the Finish Forest Research Institute METLA writes: "Referring to the discussion about girth bands I have the pleasure to inform you that our team has developed a girth band financed partly by the EU (pilot project). A couple of weeks ago we sent our annual report to Brussels. Hoping to find some individuals willing to read our 8-page paper we want to send the text to everyone interested in the use of girth bands. (Matthias Dobbertin writes "It is a girth band and has been tested for at least 2 years. Uses also a rotating potentiometer. Supposedly measures changes down to 0.03 mm. Needs only 1 nail to attach the band. The temperature expansion factor, however, seems to be 10 times the one for the Dial-Dendro and you may have to adjust for temperature changes. Price between $250 and 300.) Please, send your address (postal and fax) to me by e-mail."