Distinguishing Two Forest Communities in North Jersey by Tree Density, Species, Dominance, Importance, Diversity and Richness
Abstract
This is a study undertaken to compare and contrast richness, dominance and importance of sixteen tree species between two tree communities. The sixteen tree species have been listed in the appendix at the end of this paper. This study is a continuation of what was done earlier by ecology students in their previous year of study. The methods applied are absolutely the same, in order to make collected data comparable with each other. The three specific factors studies are relative dominance, relative density, and relative importance of the species occurring in these two forest areas.
Introduction
There are many advantages of studying the physical structure of a plant community, one of them being the fact that it can tell us something about the biological structure of the community, the interactions of species and how the community works to gather energy by cycling nutrients. This structure is crucial in determining the kind of animals present in the ecosystem and is very important in wildlife management. For example; animals that feed of nuts will generally live near an oak-hickory forest that has a lot of nuts. Such animals will include turkeys, squirrels and blue jays (Kricher, 1988). Biologists have been able to understand the ecological succession; replacement of species by other species, by studying plant communities over long periods of time.
Other community structures apart from importance and dominance include relative abundance of species, ecology laboratory and other characteristics such as the number of species (Krebs, 1985). The species’ richness is simply the number of species of organisms that can be found in a community. The measuring of species heterogeneity, relative abundance of species or even species diversity is a little bit complex. The relative number of each species in a community is termed as species heterogeneity. The word ‘hetero’ is a Greek word meaning ‘similar’. A forest with one species of trees would be called homogenous. A lawn with grass and a few dandelions in it would be less homogenous and more heterogeneous.
An ecological community is composed of interacting species that live in the same locations that rely on the nutrients and resources of one another. Many of these communities are similar to each other but can also be differentiated from one another by examining several variables. A branch of ecology studies these communities by using methods that can describe and compare these communities. These methods have been done in previous studies in the past. For our project we will collect data of trees in the forest community in South Mountain Reservation which is located in Essex County, New Jersey. This data will be compared to a previous sampled forest community of the Watchung Reservation located in Union County, New Jersey that was done the previous year by other ecology students. A study done in the upper Amazonia Terra firme forests was conducted using dominance and distribution of tree species in order to determine the distribution and abundance of tree species in the lowland terra firme forests there (Nigel et al. 2001.) In another study, richness and dominance was analyzed in order to measure the biodiversity and structure of the different districts in Beijing, China (Jie et al. 2010.) These are some variables that we can also use to determine if there is any difference in terms of richness, dominance and tree species in our two forest communities.
Since we will be using tree data in our experiment to compare the two forest communities it is significant that we consider the importance of the density and size of the tree because trees provide many resources such as being a home for many animal species and the canopy cover in that area. A study was conducted to compare the Yosemite Forest and the Wind River Forest by analyzing the importance of large diameter trees to forest structural heterogeneity (Lutz et al. 2013) The studied concluded by indicating that the large diameter trees function as organizers of tree demography over decadal timescales through competitive interactions (Lutz et al.2013) A study was done by researchers of the Smithsonian Tropical Research Institute in where ecologist examined every inch of a 125- acre area in the lowlands of Malaysia 100 miles southeast of Kuala Lumpur (Faridah et al 2008). The studied concluded by finding which type of trees can be used for lumber or energy because of the high diversity of those trees found in the area and the other different kinds of trees that need to be cultivated because of their low diversity. This can help us in our project by seeing the different kinds of trees in our communities and analyzing if the diversity in the forests are the same or different. With the data gathered by trees in the two types of forest communities they will be used as our method for conducting the experiment.
Methods
The forest communities we will attempt to compare and distinguish are the South Mountain Reservation & Watchung Reservation. The fieldwork was conducted in South Mountain Reservation in Essex County, New Jersey at the lower part of the SE-facing slope in the northwestern ridge of the reserve. The Watchung Reservation is located in a park in Union County, on the NW-facing slop of the southeaster ridge. There are residential communities around the park as well as the I-78 road and Route 22 highway.
The first ecology lab section began with the first sections gathering information at the lower part of the slope and the following sections working up the slope. Each group of all lab sections had a circular quadrat center. From this center each group was 20m away from one another. Among all the lab sections there was a total of 13 plots recorded, this paper analyses the data collected on plot #12. Each circular quadrat was approximately 254 meters squared and the total area that was sampled for SMR was about 3306 meters squared.
The following week, preliminary data from South Mountain Reservation Park was analyzed. Several factors considered included density, dominance and the importance value of the plot in hectare. This information was used to calculate the density of each tree species.
Density=Number of trees
Total area of plot in hectare
We then added all the densities for each tree species; this gave us the total density of trees per hectare. Once the density was calculated we then found the relative density for each tree species.
Relative Density = Number of individuals of one species × 100%
Total number of all individuals counted
After this was done the dominance and relative dominance was calculated using the DBH in cm. To calculate BA, the formulae (3.14r^2/10000) was used and results given in meters squared. Once BA was calculated we used this to find the dominance
Relative Dominance = Basal Area per species
Total Basal Area
After the relative density and relative dominance was found we used this information to figure out the importance value by adding these together.
Importance value = relative density + relative dominance.
Final results are in the table below.
Total Dominance-42.7
Total Density-117.8
H`-1.0986
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