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Honkala, M - Pacific yew

Page history last edited by PBworks 12 years, 7 months ago

Taxus brevifolia ~ Pacific Yew

 
Introduction
The Pacific Yew has a deep attachment to many people due to the connection that many people have with the lives that this plant has helped save. I chose the Pacific Yew because cancer runs in the genetics of my family tree. There have been members of my family that have taken medication from these trees. I feel that it is important to inform people of the good that natural medications do for humankind. It is also a relatively common plant in the Pacific Northwest.
Description
Taxus brevifolia is commonly known as the Pacific Yew.   It is a small perennial conifer tree or shrub, and grows to a height range of 15-25m. The wood of the tree is strong and resistant to decay. The young shoots are green and covered with a layer of leaf bases. The bark of the Pacific Yew forms within the first few years and is colored a red-brown. These trees grow with a straight alignment, however many are found to have a ‘mangled’ alignment due to external forces. The taller trees that have been recorded have a straight alignment. These trees tend to grow in dyer environments with warmer temperatures. These trees are usually found in the under story of forests in the Pacific Northwest, and grows best (trunk diameter) in shaded areas with moist soil.
Figure 2 USGS 1999

Life History

The Pacific Yew is found generally in moist environments and can be found in a range of temperature climates. However, in dryer environments, the tree is found growing along the side of streams and rivers. The average growing season for the Pacific Yew is anywhere form 60-300 days depending on the low temperature for the area.

Figure 3 from www.cnr.vt.edu
Both the male and female storbili appear on the under side of the branches. The males appear in May and June, the female stoblili are in the form of berrylike objects. The pollen is dispersed by the wind during the spring season. The growing season ranges from 60 to 300 days a year. Depending on the climate, most Pacific Yews grow slowly, it takes over 120 years for the diameter of the tree to become 9 inches.

Reproduction
There are both male and female parts to the Pacific Yew trees. The fruits are developed and pollinated in the spring of the year. The pollen is generally wind dispersed. The fruits ripen and fall or are taken by birds in the months of August, September, and October. The birds void the seeds to disperse them. The seeds germinate best in nighttime temperature and on beds of forest litter.
The Pacific Yew is also capable of vegetative reproduction. Sprouts have been recorded from the stumps of killed yew trees. These trees are also capable of layering, which occurs when branches of the tree have been pressed to the ground for long periods of time. However, the layered yews are not as hearty or strong as the sprouts from the stumps of former yews.
Other Interesting Facts

Figure 4 from www.cnr.vt.edu
The Pacific Yew has been used by humans since the beginning of their race. There have been artifacts found in burial sites for various humans that are made from yew trees. The wood from these trees has been used to make bows throughout history. The bark of the yew tree contains a drug called taxol. Taxol is used in a drug that is being used in cancer research by the NationalCancer Institute

 

HABITAT

The Pacific Yew grows best in a habitat that contains an old growth forest that acts as a canopy for the yew trees. These typically grow in forests that are mainly conifers. These trees do not react well in direct sunlight for long periods of time and therefore grow best underneath a canopy. However, they are able to grow in the sunlight, they will remain at a shorten stature and resemble a shrub. Within these forests the yews are found typically along ravines, in moist flats, on slopes, or in deep ravines or coves. In the United States the Pacific Yew grows mostly between the elevations of 0 and 2200 ft in the states of Washington and Oregon, and northern California. They are also native to Canada and British Columbia. 
            The Pacific Yew grows best in deep moist soil or rich rocky soils. These yews can grow in varying climates types. They have been found in areas with as little of 470mm of precipitation in a year to 4000mm of precipitation in a year. These yews can survive in minimum temperatures of -15 degrees Celsius.
There are multiple threats that are apparent in the region that the Pacific Yew occurs in. The natural habitat if the Pacific Yew is most at risk to the logging industry. The Pacific Northwest has had a history of old forests that have been devastated by the logging industry. When a logging company moves into the area it brings in the potential for multiple disasters and changes to the environment that can have devastating effects on the natural flora. One disaster that has a history with the logging industry as well as recent fire repression, as in the last hundred years, is fire. The excess in natural litter that layers the ground now burns at a hot and rapid rate. These fires often burn uncontrollably due to the massive amount of fuel that is lying on the forest floor. The fires are also hard to control due to the windy nature of the climate in the areas that these forests exist. These fires can be devastating to this type of forest that was traditionally full of old growth, which didn’t burn in small fires. However, with the increased intensity of the fires, the old growth is burning away. This is a problem for the environmental factors of many of the natural plants, such as the Pacific Yew.
            Another threat that is brought in with the logging industry is the complete removal of the old growth. While the logging industry does this because it is economically smart, ecologically it is devastating. When the old growth is removed, soil erosion and downstream silting occurs. These make regeneration of the old growth nearly impossible to happen. The nutrient rich soil is washed away and what is left is not able to sustain the life of a tree to reach old growth.
            Logging is not the only industry that is affecting the area. There are many other commercial industries that are taking the natural resources from this area and in turn are leaving the ecological system broken. Hard-rock mining and oil and gas development are also stripping areas of this environment to the ground. Clearing for residential and recreational land use is also a growing threat in the area due to the beauty of the surroundings. With the introduction of residential life to the area, more clearing has been done in past years for land suited for cattle grazing, and other agricultural processes.
            One final threat that many people do not realize exists is the introduction of new species into the area. Many times this occurs due to the urbanization or the recreational use of the land. In parts of the habitat that are located near the edge of residential land, people often will landscape with plants that are not native to the habitat and often spread into the natural environment. Invasive species have been known to wreak havoc on other species and resources that are natural to the environment.
            In order to help protect the temperate coniferous forests, we need to stop or more closely regulate the logging and other industries that are using the resources in the area. Old growth needs to be protected, and clear cutting needs to be prohibited because it can be so devastating to the surrounding environment. People need to be educated about where and how their resources are being harvested from. The public needs to be informed about all of the possibilities that are out their in all of the forests. Many people believe that the rainforest should be saved because there may be a cure for cancer in it. There is a drug that is taken from the Pacific Yew that is grown in the temperate coniferous forest that is being chopped down as well. This drug does help save lives.
            Fire suppression is something that ecologists, environmentalists and the general public do not agree on. However, throughout history fire suppression has caused more devastating fires. Forest fires need to be able to burn naturally. Unfortunately, the damage of excess fuel has already been building up and thus needs to be dealt with before fires can be let natural.
Bibliography
Goodman J. 2001. The story of taxol : nature and politics in the pursuit of an anti-cancer drug. Cambridge (NY): Cambridge University Press.
Taxus Brevifolia Nutt (Pacific Yew) [Internet]. [Updated 2008 Jan 28]. Washington D.C.:United States Department of Agriculture; [cited 2008 Feb 14]. Available from: http://www.na.fs.fed.us/spfo/pubs/silvics_manual/Volume_1 /taxus/brevifolia.htm
Taxus brevifolia Nuttall 1849 [Internet]. [Updated 2002 Nov 7]. Gymnosperm Database; [cited 2008 Feb 14]. Available from: http://www.conifers.org/ta/ta/ brevifolia.htm
The Pacific Yew (Chemical Landmarks) [Internet]. [Updated 2007]. Washington DC: American Chemical Society; [cited 2008 Feb 14]. Available from: http://center.acs.org/landmarks/landmarks/taxol/yew.html

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