|
ception to this rule. Many species of trees display annual growth rings. These rings allow the observer to glimpse back into the life of the tree and determine how the climate affected tree growth. The climate can be seen in the story of the tree rings. The life story of the tree is in close symbiosis with its environment.
Trees grow in areas that they have evolved to be best suited for survival. Trees are a part of an ecological system and in that system they are in constant interaction with the environment. Trees react to environmental stimuli almost immediately (Schweingruber, 1989). The events that cause the tree to react, however, do not necessarily appear in the tree ring record. The tree ring record is the sum of all of the events that affect the tree over each years growing period (Stokes and Smiley, 1996). The health of the tree one year will affect its performance of growth in the following years. The condition of a tree is related to a variety of environmental constraints. These constraints include latitude, elevation, topography, influence of mechanical movement, geology of the area and light (Schweingruber, 1987).
Tree rings have been used to reconstruct the climates of a region. Tree ring analysis, or dendrochronology, has been used in a variety of disciplines. A principal use of dendrochronology is in the field of archeology, where ancient buildings are dated to establish their origin. Tree rings can also be attained from petrified wood and charcoal from ancient fires to reconstruct past climates. The tree ring records from specific sites are cross-dated with other tree ring chronologies to form a master chronology of the region (Grissino-Mayer, 2000). The master chronology shows the observer the yearly climate trends of the region.
Tree rings are formed by the physiological growth of a tree. The two distinct zones of growth within a tree ring are earlywood and latewood. Earlywood begins to develop when the frost from the winter has left the ground and water becomes available to the subsurface. This process leads to the reactivation of the cambial growth (Bannan, 1962). The beginning growth in a tree, which produces earlywood, is called periclinal growth. Periclinal growth lasts until early summer and accounts for 35-40% of a rings width growth for a year (Bannan, 1962). In the early summer, the growth activity is reduced. This growth is called aestival growth. By the middle of the summer nearly all of the growth has already taken place. Until the end of the growing season, the tree will grow only slightly. The period of aestival growth is also called latewood. The latewood in a tree ring marks the end of one year and the beginning of a new one.
Methods: Tree Ring Samples
Materials:
Increment Borer
Carrying case for tree core samples
Phloroglucinol (dye)
Mounting for samples
Methods:
Five different White Oak (Quercus alba) trees were used in the study due to the pronounced ring structure. The White Oak selected for the study were located off of route 27, near Western Campus across from Peiffer Park. The five samples were growing in a site of flat topography. All five of the trees were within a 50-yard radius of one another. The site was selected because the effects of growth on a steep slope were non-existent. Four-mile creek was located 50 yards to the west of the site. Trees were then sampled using the increment borer. The borer was placed perpendicular to the trunk of the oak. It is important to have the borer enter the tree at the perpendicular to obtain accurate tree rings. If the borer enters the tree skewed the resulting rings will also be skewed and give the observer unreliable data. Each core sample was taken on the west side of the tree trunk. The borer was pressed into the tree where the bark was at a minimum. The tree borer was then screwed in until the handle was approximately three inches from the bark of the tree. The extractor was then inserted into the tree borer shaft upside down (upside down 'u'). The extractor was then twisted until the 'u' faced up and then the tree core sample was removed. The tree core sample was then labeled and placed into the carrying case. Tree core samples are fragile and when they are removed from the tree the samples break easily. If the sample did break, the sample was taped together, so as to not lose the chronology of the rings. The tree borer was then quickly removed from the tree. This preceding process was repeated twice in each tree to assure accurate ring analysis.
When all of the samples were attained the tree cores were then mounted. The mounting keeps the samples safe from breaking and stable. The next step is to coat the trees in dye. It is a clear dye that slightly accentuates the tree cells. All of the tree samples were mounted and labeled.
|
|
