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.
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.