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... t an advantage because it doesnt need to wait for a male to fertilize a female. The amount of time it takes for seed dispersal to occur is greatly reduced. All of these factors combine to make the poplar a successful plant that can adapt to almost every habitat.
The poplar is very light dependent; it needs lots of light for its leaves to achieve enough photosynthesis so growth can occur properly. Poplar roots are shallow, especially on wet soils. Most poplars may have extensions called root hairs that increase root surface area and increase nutrient and water uptake. The seed dispersal is more intense in the spruce because seeds do not regularly travel very far. The seeds are also naked which provides less protection against animals such as birds and squirrels than the poplar. Temperature extremes and drought can also harm these exposed seeds.
Although the adult trees can withstand such circumstances, seedlings are vulnerable to them. Light competition is much more intense in the poplar tree than in the spruce. The spruce prefers to have a lot of light but it can deal with having to live in shade. If theres not enough light available for the poplar tree it will start to lose nutrients and water and the leaves will begin to turn yellow, or even dry up. This would lead to an healthy tree that might eventually die. Root space basically has the same intensity of competition in each tree.
However, since most poplars have root hairs they have the ability to take up more nutrients and water than spruce trees. This could cause increased competition in the poplar because each tree would try to increase its surface area in order to absorb more from the soil. If there is limited space complications could arise. Light and soil moisture are two of the most important resources in growth and therefore, have many affects on intra specific competition. Soil can determine how much water and nutrients there are available for a trees roots to absorb. Light comes primarily from above and is depleted when it is intercepted by plant canopies, competition for light is usually strong: taller individuals can decrease the amount of light received by their shorter neighbors (David A Comes and Peter J.
Grubb 2000). As mentioned earlier the deciduous trees rely on lots of light to grow efficiently. Conifers would elect to have light but when without it they can tolerate shade. The more light made available the more photosynthesis can occur, which will provide more sugars to the tree for growth.
Soil moisture is related to light in Comes and Grubbs journal article. It states that, penetration of light is least in forests on moist soils. Dry woodland typically allows 20 times as much light to penetrate as do wet forests. Differences in the ability of varying soil types to store water do exist. Clay soil can hold the most water, next would be the loamy soils and last the sandy soils. The rate at which water penetrates the soil depends mainly on soil texture.
There are large pore spaces in sandy soils through which water will move quickly and easily, clay soils have smaller pore spaces causing water to move more slowly. Decreased or insufficient water in the soil can cause rootlets to cease to grow before reaching their potential full length. Another problem for a tree would be too much water; it can cause the air spaces in the soil to fill with water and restrict oxygen uptake. Spruce are able to grow on a wide range of soil conditions. It grows well on loams, silt loams, and clays, but rather poorly on sandy soils. (Earl J. S.
Rook 1998). It is somewhat demanding, often restricting it to sites with well-drained mineral soils, mostly acid, with a pH of 4. 0 - 5. 5; it grows poorly on sites with high water tables (Earl J. S. Rook 1998). Poplar trees grow well on alluvial floodplains, including gravel, deep sand, clay loam, silt, and silty loam (Steve Strauss 1997).
They have an extensive need for soil moisture and high nutrient requirements, particularly for calcium and magnesium. They do not tolerate deep acidic peat's and humus with slow release of nutrients (Steve Strauss 1997). The ability of roots to take up nutrients can be decreased at low water potentials. In all, because of the great need for both light and moisture trees will compete to try and get the essential amount needed for further growth, and for overall fitness. With all of this information in mind, our results should have shown greater intensity in competition as well as a significant correlation. This experiment doesnt reflect a large enough population size and thus, that is the most probable reason for the outcome.
Another problem with this experiment is that we didnt check to see if any of the trees were dead before measuring them. If some of the trees were dead, it would be assumed that no competition would be going on between it and its neighbor. Nonetheless, it could still be shading the other tree and therefore, be blocking it from a good source of light. If the trees happened to be decomposing they might have released nutrients for the neighbor to use, which in turn might compete for those nutrients with other neighbors.
In summary, it would have been more accurate to examine each tree pair before measuring, to see if any were dead. There are other factors that could have been considered in determining the location and size of the trees. The age of a tree or plant would tell us if it was still able to grow any bigger or if it was already at its maximum width or size. The study of the presence of animals could help to determine if any bark, leaves, branches, or any other parts of a tree / plant were consumed for food. This could affect the size of a tree / plant . It could also cause more competition between it and other trees / plants , which would also affect the size.
The presence and amount of other trees and plants near the individuals being tested could indicate how much space was available for new trees / plants and therefore, the location. Other things such as climate, vegetation, and pollution would further be helpful in determining the size and location of trees and other plants. In conclusion, it is known and that intra specific competition does exist between trees and their neighbors, and that this competition can vary between species. It is also known that extreme competition on nutrient-poor soil with an assured water supply leads to a dense array of miniaturized plants, whereas extreme competition in a dry climate leads to widely spaced dominants and a lack of interstitial plants (David A Comes and Peter J. Grubb 2000). Competition is an important factor affecting the composition of many plant communities.
Measuring the effects of competition on plant growth in these communities is critical to examining present ideas about how it relates to tree size and location. LITERATURE CITED Cahill Jr. , James F. 1999. Fertilization effects on interactions between above and below ground competition in an old field. Ecological Society of America 80; 466 - 480.
Comes, A. David, Grubb, J. Peter. 2000. Impacts of root competition in forests and woodlands: A theoretical framework and review of experiments. Ecological Monographs 70; 171 - 207. Krone, T.
David. 2001. General Ecology. Brooks/Cole. Pacific Grove, California, U.
S. A. Park, Magdalena. 2001. An Introduction to Ecology and Evolution. Mount Royal College. Calgary, AB, Canada.
Rindels, Sherry. 1992. Tree Root Systems. Horticulture Home Pest News, April issue; 43 - 44. Rook, J. S.
Earl. 1998. Picea Glauca: White Spruce. Pacific Northwest Networks. web Strauss, Steve. 1997. Report of the Poplar Working Group. Oregon State University.
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