Average Taper Research Articles

Stem form and growth in picea abies (L.) karst, in response to water and mineral nutrient availability

Change of stem shape as a result of increased and/or decreased availability of water and mineral nutrients was studied in a Norway spruce (Picea abies (L.) Karst.) stand in southern Sweden. Water availability was correlated inversely with average taper, defined as the ratio between diameter at breast height and height of the tree. When moving from drought via control to irrigation, average taper gradually decreased. Fertilization without irrigation had no influence on average taper. Stem form measurements indicated a decrease in diameter in the upper half of the stems following irrigation, whereas ammonium sulphate application resulted in increased diameter in the upper half of the stems, compared with the control. The results emphasize the necessity of creating stand‐ and treatment‐specific allometric relationships when estimating production in terms of volume or biomass, and of interpreting growth based on basal area with caution.

Long-term effects of superphosphate fertilization on stem form, taper and stem volume estimation of Pinus radiata

The long term effects of superphosphate fertilization on stem form, taper and stem volume estimation of Pinus radiata on a phosphorus-deficient site was examined using data from a fertilizer experiment which had been maintained for 30 years. The application of superphosphate resulted in long term and statistically significant changes in stem form. Mean cylindrical form factor ranged from 0.33 for the control trees up to 0.40 for trees fertilized with 100 kg P ha −1. Stem form was also examined through taper curves which provided detailed depiction of average relative stem profiles. The increase in cylindrical form factor of fertilized trees was largely attributed to a significantly broader profile of the lower third of the stem. In comparison with the control trees, the fertilized trees also had a broader, although not statistically significant, profile of upper and middle stem which could also contribute to the increase in their cylindrical form factor. With increased form factor a greater proportion of the stem became merchantable because of increased log length to tree height ratio. Mean average taper of trees did not show a consistent trend with increasing lelevels of superphosphate application. It largely reflected the differential response of DBH and height growth to the treatments. The volume equation based on control trees underestimated the underbark stem volume of fertilized trees by 5–12% on average. Developing separate volume equations for the fertilized trees is warranted.

New guidelines for preparation taper.

The purpose of this article is to provide new guidelines for minimally acceptable preparation taper by developing a theoretical mathematical foundation based on principles of resistance form. Yes and no are the possible answers to the question, "Does a preparation have resistance form?" This dual nature is useful because in graphing resistance form as a function of taper, potential tapers on the x axis are divided into two groups with an exact dividing point. Tapers less than this dividing point provide resistance form; tapers larger or equal do not provide resistance form. This dividing point makes a reasonable standard for minimally acceptable taper. Average tapers are defined as the limiting average taper and are mathematically determined to equal 1/2 arcsin (H/B), where H is the height of the preparation and B is the base. From this equation, the taper required to provide resistance form for an individual preparation can be calculated by using the preparation's height to base ratio. The equation can also be used to provide guidelines by tooth group. Dies of a prosthodontist were saved and sorted by group (incisors, canines, premolars, and molars). Measurements of 30 dies from each of these groups were used to calculate the average (H/B) ratios and standard deviations. Calculating the limiting average taper by using the average height-to-base ratio minus two standard deviations provides the dividing point taper that is acceptable for over 97% of the preparations. The values calculated are: 29 degrees for incisors, 33 degrees for canines, 10 degrees for premolars, and 8.4 degrees for molars.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth and stem form changes in Picea abies as affected by stand nutrition

The changes in basal area, volume and tree shape in an ‘optimum fertility trial’ in Norway Spruce were studied after the treatments had been applied for 15 years. There was a marked response to N and a lesser response to P. Increased average tree taper was associated with the N application. Form factors tended to show less change, but, even allowing for tree height responses, there was up to a 10% reduction. Phosphate fertilizer in the presence of N increased form factor slightly; applying a ‘complete’ fertilizer reduced form factor and increased taper while the trees were under about 6 m tall. The use of individual treatment regressions of volume on basal area resulted in increased precision in estimating the volume of individual treatment means.

CONSTRUCTION OF A TAPER TABLE FOR JACK PINE IN SASKATCHEWAN (Pinus Banksiana—Lamb.)

A taper table has been developed for jack pine of average form in Saskatchewan. The table is strongly weighted for diameters up to 12 inches and heights up to 70 feet. Beyond these limits the reliability of the table is limited because of the lack of data.The average taper of jack pine in Saskatchewan has proven to be quite similar to that of the Lake States. Therefore, much of the volume table work done in the Lake States should be applicable in Saskatchewan.From the taper table developed for Saskatchewan, volume tables may be constructed on the basis of any desired standard: board foot or cubic foot; any specified top diameter limit; total height or merchantable height. Also, it is possible to determine how many bolts of different diameters, poles or ties can be utilized from each height-diameter class. The table represents average conditions where the average form class of the stand is approximately 65. No allowances for defect have been made.