- Abstract Description and Proposal of Project.
This project is based on the structural and compositional dynamics of a local forest. The type of forest that is used for this research is Oak-Hickory. A local forester invited our group to conduct a Continuous Forest Inventory (CFI) in the forest. The process involved the setting up of Continuous Forest Inventory plots in this forest. A total of three fifth-acres CFI plots were set of up. The process of setting up these plots involved the random selection of a site within the forest and the identification of a plot center. All trees within 52.7 feet from the plot center were considered as being inside the plot. The distance of each tree from plot center was measured, and the species of each tree was identified. A metal tag bearing a number was also hammered on each tree for future identification. Only trees with a DBH greater than 10 cm were measured. The diameter of the trees was measured 4.5feet above the ground, which is diameter at breast height (DBH). The azimuth measurements of each tree from the plot center were also taken. Tree identification and measurements were conducted in a clockwise direction. All the data collected was recorded on a sheet of paper and was then entered into an excel spreadsheet for graphical and tabular analysis.
The purpose of this CFI study was to explain the structural and compositional forest dynamics of the forests. This purpose was achieved through the analysis of key ecological parameters which included relative density, relative dominance, basal area, and importance value. Relative density refers to the total number of trees of a given species divided by the total number of trees within the entire plot. Basal area measures to the cross-sectional area occupied by the trunk and stem of a given tree. Relative dominance is derived by dividing the total basal area of a given tree species by the total basal area of all the tree species present in a given plot. Importance value is calculated by dividing the sum of the relative density and relative dominance of a particular tree species by two and then multiplying the result by one hundred.
The major findings of this research were that Acer saccharum was the dominant species in the forest. A.saccharum had the highest overall relative density, relative dominance, and important values. The dominance of A.saccharum indicates the forest is in mid succession levels, and is moving towards late succession. Despite being in the mid-succession, the forest also consist of patches of early succession tree species. A good example is Prunus serotina which was dominant species in plot 1. Another major finding that was evident from this research was that the oaks identified, Quercus spp., within the study area had the largest diameters averaging at about 47.88cm. This means that Oak tree species are the oldest species within the forest but have over time been out competed by Acer saccharum. This therefore indicates that there are structural and compositional dynamics taking place within the forest.
- Introduction to Project Details
The forest is approximately 180 acres in size. The type of forest is Oak-Hickory with elements of Acer saccharum, Quercus rubra, Quercus alba, Quercus verutina, Celtis occidentalis, and Prunus serotina. The frequency of these trees and their sizes varies within different portions of the forests according the topoedaphic conditions and disturbance history. In order to determine the structural and compositional dynamics at the forest, our group conducted a continuous Forest Inventory (CFI study) at the forest. The CFI study involved the setting up of three-fifth acre CFI plots at different locations within the forest. The process of setting up the CFI plots involved the random selection of a site and the identification of a plot center. A tag bearing a number was hammered on each tree for future identification, and all trees within a 52.7 feet radius were considered as being inside the plot. The species of the trees within the plot were identified, and the DBH of the trees was measured. Other measurements that were taken included, the distance of each tree from the plot center, and the azimuth. The process of measuring and identification was conducted in a clockwise direction. The obtained results from the CFI study were entered into excel spreadsheet for analysis.
The analysis involved four ecological parameters. These include basal area, relative density, relative dominance, and importance value. Basal area is the cross-sectional area of stems and trunks of a tree. Relative density refers to the total number of trees of a particular species divided by the total number of trees from all species. Relative dominance refers to the total basal area of all the trees of a given species divided by the total basal area of all the trees in a given plot. Importance value refers to the role that a given tree species plays in an ecosystem. Importance value is obtained by summing relative density and relative dominance and then dividing the result by two. Results are converted to percentage by multiplying them by one hundred. The ecological dynamics discussed above are important in explaining the successional phases of the forests. Different trees are associated with different forest succession levels. For instance, Prunus serotina is an early succession species, while Acer Saccharum is a late successional species. Therefore, the purpose of this paper is to use the ecological parameters derived from the data collected during the CFI study to determine the structural and compositional forest dynamics taking place at the forest.
- Methodology and Data Collection
The CFI study required the following tools and materials: a hammer, metal tags, DBH tape, measuring tape, a red tape, a compass, metal rods, spray paint, paper, and a pen. The site of the plot was randomly selected to avoid a bias towards specific areas that seemed more accessible and convenient. After the identification of a random site, a metal rod was hammered to the ground to mark the plot center. The metal rod was wrapped with red tape in order to make easily identifiable from a far in the case of future research. A tape measure was then tied onto the metal rod and all trees within a 52.7 feet radius were considered to be inside the plot. The species of each tree was identified in a clockwise direction. A metal tag bearing a number was also hammered into each tree to ease tree identification during future studies. The DBH of each tree was measured 4.5feet above the ground in order to avoid the elongations at the bottom of trees created by the roots. The distance of each tree from the plot center was also measured. The azimuth measurements of each tree from the plot center were also taken. All this data was recorded on sheet of paper. The data obtained from all the three plots was then entered into an excel spreadsheet for graphical and tabular analysis. Among the ecological parameters that were calculated include basal area, relative density, relative dominance, and importance value. Basal area was calculated using the formula {π × (DBH/2)2}. The list below shows how relative density, relative dominance, and importance values were calculated.
List of Formulas used in the CFI study
- Basal Area (A) = π × r2
- Relative Density = Number of individuals in a species ÷ total number of individuals in particular plot
- Relative Dominance = Sum of Basal Area of a species ÷ Sum of the Basal Area of all species
- Importance Value = 0.5(Relative Density + Relative Dominance) X 100
- Statistical Data Obtained from the Research
The study showed that Acer saccharum was the most dominant tree species overall. A.saccharum had the highest relative dominance, relative density, and importance values compared to all the other tree species in the forest. The overall importance value of A.saccharum in the three CFI plots was 47.2 percent. Despite A.saccharum being the dominant species, there was an abnormality in plot 1 whereby Prunus serotina was the dominant species with an importance value of 42.06 percent within the plot. Plot 1 was located at the forest opening compared to plot 2 and 3, which were located in the forest interior.
The oak species -Quercus alba, Quercus rubra, Quercus verutina- which were found in the forest were larger and older trees. All the oak trees on the three plots had an average DBH of 47.88.see fig 1.1 below. There were also lots of Course wood debris (CWD) and leaf litter on the forest floor. In addition, there were a few trees fallen trees that still had leaves in them, and a tree that had snapped in half.
Figure 1.1 showing the average DBH of oak species on the 3 CFI plots.
Fig 1.2: Graph showing the Relative Dominance of Tree Species
Fig 1.3: Graph showing the Relative Density of Tree Species in the Forest
Fig 1.4 Graph showing the Importance values of tree Species
- Analysis of the Statistical Data
Acer saccharum was the overall dominant tree species A.saccharum had the highest relative dominance of 0.57, the highest relative density of 0.38, as well as the highest importance value of 47.2 percent. This indicates that the climatic conditions and the topoedaphic factors at the Oblates are favorable to A.saccharum making this tree species the major winner in the forests. According to Burns and Honkala (1990), A.saccharum is native to the Midwest. This means that it is highly adapted to the climatic conditions in forests within Illinois such as the Oblates. In addition, Burns and Honkala (1990) explain that A.saccharum tends to do better in soils that have a pH between 5.5 to 7.3. This pH is maintained and modified by heavy leaf litter. This means that the heavy leaf litter witnessed in the forest during fall is advantageous to the A.saccharum in terms of modifying soil pH to the levels. In addition, the A.saccharum is the major winner in the forest because its seeds are dispersed by wind. Burns and Honkala(1990) explain that the seeds of A.sacchraum are large and paperly.Seeds of the A.saccharum have 20-27mm samara which allows them to be carried by wind around the forest to distances as large as 100M(Burns and Honkala, 1990).
Perry et al (2008) writes that species which have widely dispersed seeds, as is the case with A.saccharum, become the colonizing species of a given area. This means that the ability to widely disperse seeds makes it easier for the A.saccharum to colonize the forests. In addition, Burns and Honkala explain that A.saccharum has very high germination rates of about 95 percent. This means that the likelihood of A.saccharum seeds to germinate is higher compared to other tree species. In addition, Quercus alba and other oaks produce acorns at their old ages. In the case of Quercus alba, acorns are produced when the trees are between 50 and 200 years(Burns and Honkala, 1990).This means that oak species within the Oblate forests cannot be able to compete with A.saccharum, which flowers and fruits at about 22 years. This is half the age of flowering in the case of Quercus alba. The presence of more A.saccharum indicates that the forest is at mid succession and is moving toward late succession. The lower flowering age of A.saccharum compared to oak species, wide range seed dispersal, and high germination rates accounts for the reason why A.saccharum has dominated the three plots. Since oak species have lower seed production levels, and flowers at an older age their new saplings cannot be able to compete with Acer saccharum. This means that A.saccharum has many young trees compared to oaks (Quercus spp.) which have older trees. This explains the reason why oaks have an average DBH of 47.88cm compared to A.saccharum that have an average DBH of 30.17.
In addition, the interference with historical disturbances such as forest fires has contributed to the decline of oak species the forests of La vista. The survival of is dependent on mineral soils (Burns and Honkala, 1990). Forest surface fires play a key role in burning organic matter and easing the accessibility of mineral soils by oak saplings. Due to the reduction of these historical fires, the forest floor has been covered by organic matter, which makes it more difficult for oak saplings to survive (Balliett, 2010, p.44). This accounts for the reason why most of the oak trees are large old trees. On the other hand, A.saccharum has taken advantage of the inability of oak species to compete, thereby colonizing the forest.
A.saccharum has also been able to dominate the forest because the species is shade tolerant. This tree species is able to survive under low light intensities with Oak Hickory Forests. The low intensity is caused by the overlapping canopies and the positioning of the slope. South facing slopes tend to have more light compared to the north facing slopes. Other species such as oaks are either intermediate shade tolerant or entirely light intolerant. The ability of A.saccharum to survive and compete under low light intensities makes them more adaptable to the forest compared to other species such the oaks. This accounts for reason why the A.saccharum continues to dominate the forest.
However, there was an abnormally in plot 1 where the dominant species was Prunus serotina. Plot 1 was located at the opening of the forest and was adjacent to an open plot, which might have been used for agricultural purposes in the past. Burns and Honkala(1990) explain that P.serotina grows well in soils that are highly acidic, and infertile. Considering that agriculture, mostly monoculture depletes soil nutrients and that increased use of inorganic fertilizers lowers soil pH (Tan, 2010), it is likely that the soil properties at the opening of the forest are almost similar to those of the adjacent open field, which makes it favorable for P.serotina. This has caused this tree species to take advantage of the topoedaphic conditions causing the tree species to colonize the forest opening. The forest opening might also be an ecotone, where two soil types meet meaning that the soils at the opening are not very different from the soils in the open field (Casper, 2007, p.79). In addition, forest openings have more access to direct sunlight.
Burns and Honkala (1990) write that P.serotina has high productivity in drier soils. Considering that the forest opening has more sunlight, the soils at this part of the forests are drier compared to those in the interior that have more shading due to canopies. This means that Plot 1 located at the forest opening provides a favorable habitat for the P.serotina, thereby accounting for the abnormality accounted for on plot number 1. The large number of Course wood debris on the forest floor, and incidences of trees snapping in half indicates that forests has some disturbances. However, the most prevalent disturbance at the forest is wind.
- Conclusions of Project.
In conclusion, the type of forest studied is Oak-Hickory. The forest covers an approximate size of about 200 acres. The CFI study conducted on three randomly selected fifth-acre plots at the forest indicate that A.saccharum is the most dominant species in the forest. It has the highest relative density, relative dominance, and importance value. Most of the A.saccharum trees are young trees with an average of 30.17cm. The oak species at the oblates are large old trees with an average of 47.88cm. These dynamics indicates that forest is at the mid-succession period and is moving towards late succession. Despite these dynamics, there was an abnormally on plot 1 where P. serotina was the dominant species. This was highly influenced by the location of the plot at the opening of the forest, and the previous land use of the adjacent open field. It is also evident that there are disturbances within the forest. The major disturbance at the forests is wind, which has led to the breaking of branches and the snapping of young trees into half. These forest dynamics paint a big picture about the structural and compositional forest processes taking place at the local forest.
- Margin of Error
Despite the success of this project, there were a few shortcomings. First, time constraint did not allow the setting up of more plots at the forest. This would have been helpful in capturing more forest dynamics within the forest. Secondly, great attention was not given to trees below10cm in DBH and the understory species within the forest. This information would also play an important role in giving a more detailed explanation about the structural and compositional dynamics within the forest.
Literature Cited
Balliett, J. F. (2010). Forests. Armonk, N.Y.: M.E. Sharpe.
Burns R and Honkala B. (1990). Silvics of North America. United States Department of Agriculture, Forest Service: Washington, DC. http://www.na.fs.fed.us/spfo/pubs/silvics manual/table of contents.htm.
Casper, J. K. (2007). Forests: more than just trees. New York: Chelsea House Publishers.
Perry D, Oren R, Hart S. (2008). Forest ecosystems. Baltimore, MD: Johns Hopkins University Press.
Tan K. (2010). Principles of soil chemistry. Boca Raton, FL: Taylor & Francis Group.
