Allometry is a standard method of determining biomass and Net Primary Production of many trees. One of the standard variables used in such allometric regressions is bole diameter. On straight trunk trees measurements at breast height (DBH) taken using a DBH tape is adequate for quantifying changes in diameter over time. However, in scrub forests such as the Pinon Juniper PJ woodlands, common on the Sevilleta, both the pinon and particularly the junipers are relatively short and multi-trunked so that measurements must be taken near the ground and the consistency between measurements often lead to erroneous growth analysis. To reduce such discrepancy in readings, dendrometer bands were installed on 20 pinons and 20 junipers in the Cerro Montoso area where understory ANPP has been measured for some time. These dendrometers quantify the expansion (and contraction) of the tree bole through time. The beginning diameter at the time of installation was also measured and recorded. Heights of the 40 trees were also measured. The diameter of the foliage was measured across these trees at the widest point and then again on an axis perpendicular to this first reading. Readings of the dendrometers are repeated on about a monthly basis through the growing season. Heights of the trees are done on an annual basis. Measurements are collected to quantify the increase in bole diameter for a set of Pinons and Junipers in this area over time.
Readings of the dendrometers are done on a semi-systematic basis. The most frequent readings are done during the growing season. It is attempted to take monthly readings during the period from April through October. A few readings have been taken during the period when the trees are presumed to be dormant. The trees have been GPS'd so this makes it easiest to find individual trees. Measurements are recorded on data sheets with tree numbers and the previous readings collection's readings. Readings are taken to the nearest 0.1 mm. When the dendrometer readings reach 20 mm the value is recorded and then the screw is loosened to allow expansion of the band so that vernier scale is returned to a value close to zero and the screw is retightened. The value should not be set at zero as the tree may shrink during the subsequent period. Rather a value of about 3 is preferable. This new value should then be noted in the comment section of the data sheet.
Sampling Dendrometer Installation
The dendrometers used are not designed to actually measure the diameter of the tree but rather to record the change in the diameter from reading to reading. Each dendrometer includes 2 all-thread bolts that are inserted into the tree, a springed hinge on which is mounted a vernier scale, a metal tape that passes around the tree and is anchored on to the housing of the vernier scale with the other end attached to the spring loaded carriage the slides within the housing as the tree expands. Dendrometers are installed as near the ground as possible but on regions of the tree that do not show any noticeable swelling. It was decided to limit the application of dendrometers to single-stem trees as this made both reading of the dendrometers and interpretation of results simpler. A portable drill was used to drill holes into the bole of the trees. The all-thread bolts were inserted into the trunks several inches. The hinge supports are mounted at a distance away from the tree which will allow the metal tape that passes around the tree to pass smoothly into the carriage housing so that the carriage will slide smoothly. The band is anchored on the housing and then passed around the tree and run through the housing and a screw-down clamp anchors the tape to the sliding carriage with the scale measurement being at least a few mm above the zero. These dendrometers do not measure the actual diameter. Instead they measure the change in diameter actually circumference from time of installation until time of reading. Standard DBH tapes were used to take initial diameters at the time that the dendrometers were installed. These were measured just above or below the path of the metal band. The height of the dendrometer band above the ground was also recorded. Metal tags with numbers from 160 to 200 were attached to each tree. Some of trees had tags from Roman Zlotins mast study and these were recorded as well. All trees were GPSs although those inside the mast study plot would have been GPSd at the beginning of the mast study.
JMM: qa/qc'd 2009 data and combined to previous years. 7 Dec 2009
YX. 1/28/2009. this metadata was created and entered on 1/12/2009 based on the file 11/21/2008 D.M.; and Checked and orgnized files to the correct Formate file. Notes: 04/05/06 tree #189 current demrometer5? and then checked the measurments (06/29/06/06) is 6.1, So enter 6.1 instead of 5?.
Additional Information on the Data Collection Period
Initial readings were made when the dendrometers were installed in early April 2006. Subsequent measurements are recorded on approximately a monthly basis during the most active growing period i.e. March-Nov
Additional Study Area Information
The trees with the dendrometers are located in or near the 1 ha plot established by Roman Zlotin in 1998 for quantify berry and mast production (Sev163) just west of the Cerro Montoso Met station.
North Coordinate:34.369South Coordinate:34.368East Coordinate:-106.54West Coordinate:-106.536