The following is adapted from a vegetation sampling lab I did in college.
In order to properly study an area, one has to know certain characteristics of that area. Studying the vegetation of an area has its many benefits. These include allowing us to understand the difference between communities, describe habitat, and understand how vegetation reacts to certain environmental gradients. In this lab, we focused on using the point-centered quarter method to characterize a forested slope.
From the data collected we can calculate average density per hectare, relative density, density, basal area, relative basal area, frequency, relative frequency, importance value, and relative importance value. These values allow us to compare characteristics among different species. This was the main objective of this lab.
This study took place on Pine Hill Alfred, NY on September 9th, 2013. Following the gas pipeline trail behinds Ann’s House on the bearing N10Wo we walked 5 meters off the gas pipeline trail. At that point we placed the center of a quadrant composed of 90o quarters. Quarters 1 and 2 faced North, 1 being on the East side. Quarters 3 and 4 faced South, with 3 being on the East side. We determined the four closest trees to the quadrant, with a diameter at breast height over 10 cm. For each tree we calculated the distance from the quadrant, diameter at breast height, and the tree’s species. The same process was repeated for a quadrate located 25 meters from the path.
Table 1. Original measurements of trees on Pine Hill from 09/12/13.
|Species||Basal Area at Breast Height||Distance from Quadrant||Quadrant||5 meter or 25 meter|
|Red Oak (Quercus rubra)||298.65 cm2||2.5 m||1||5 m|
|Bigtooth Aspen (Populus grandidentata)||471.44 cm2||5.7 m||1||5 m|
|Red Oak||132.73 cm2||6.2 m||1||5 m|
|Blue Beech (Carpinus caroliniana)||78.54 cm2||9.4 m||1||5 m|
|Black Locust (Robinia pseudoacacia)||754.77 cm2||8.4 m||2||5 m|
|Sugar Maple (Acer saccharum)||380.13 cm2||19.5 m||2||5 m|
|White Pine (Pinus strobus)||268.80 cm2||17.1 m||2||5 m|
|Red Oak||283.53 cm2||18.7 m||2||5 m|
|Hop Hornbeam (Ostrya virginiana)||143.14 cm2||4.5 m||3||5 m|
|Black Locust||629.02 cm2||3.8 m||3||5 m|
|Hop Hornbeam||78.54 cm2||5 m||3||5 m|
|Black Locust||283.53 cm2||5 m||3||5 m|
|Hop Hornbeam||283.53 cm2||2.4 m||4||5 m|
|Black Locust||1625.97 cm2||3 m||4||5 m|
|Hop Hornbeam||78.54 cm2||5.5 m||4||5 m|
|Black Locust||706.86 cm2||5.9 m||4||5 m|
|Black Locust||510.71 cm2||9.6 m||1||25 m|
|Hop Hornbeam||165.13 cm2||6.1 m||1||25 m|
|Hop Hornbeam||13.5 cm2||9.7 m||1||25 m|
|Black Locust||1075.21 cm2||9.7 m||1||25 m|
|Black Locust||452.39 cm2||4.9 m||2||25 m|
|Hop Hornbeam||176.71 cm2||5.9 m||2||25 m|
|Hop Hornbeam||78.54 cm2||6.3 m||2||25 m|
|Black Cherry (Prunus serotina)||78.54 cm2||8.05 m||2||25 m|
|Black Locust||113.10 cm2||2.8 m||3||25 m|
|Red Oak||426.38 cm2||4.2 m||3||25 m|
|Sugar Maple||330.06 cm2||6 m||3||25 m|
|White Pine||176.71 cm2||6.6 m||3||25 m|
|Black Locust||201.06 cm2||4.7 m||4||25 m|
|Black Locust||254.47 cm2||5.8 m||4||25 m|
|Red Oak||86.59 cm2||6.9 m||4||25 m|
|Black Locust||572.56 cm2||8.3 m||4||25 m|
From the field data it was calculated that the average density per hectare was 1405 trees (table 1). This data was then used to determine relative density and density for each species (table 2), basal area and relative basal area (table 3), frequency and relative frequency (table 4), and importance value and relative importance value (table 5).
In addition the data from table 1 shows that most of the basal areas lay between 100 cm2 and 500 cm2 (table 1). Most trees were also located within 10 meters of the quadrant. A few trees where fairly far away from the quadrant as we had to cross the gas pipeline trail to sample them. Lastly 2 Black Locusts had a basal area over 1000 cm2. Therefore when analyzing the rest of the data this will need to be taken into account.
Table 2. Relative density and density by species of trees on Pine Hill from 09/12/13.
|Species||Number of Individuals||Relative Density||Density|
|Red Oak||5 trees||16 %||224.8|
|Bigtooth Aspen||1 trees||3 %||42.2|
|Blue Beech||1 tress||3 %||42.2|
|Black Locust||12 trees||38 %||534|
|Sugar Maple||2 trees||6 %||84.3|
|White Pine||2 trees||6 %||84.3|
|Hop Hornbeam||8 trees||25 %||351.3|
|Black Cherry||1 trees||3 %||42.2|
From this table we can see that most tree species have fairly few numbers of individuals (table 2). Therefore most tree species had relative densities under 6 %. In fact only 3 tree species had values over this amount. Those species were Red Oak, Black Locust, and Hop Hornbeam.
Table 3. Basal area and relative basal area by species of trees on Pine Hill from 09/12/13.
|Species||Average Basal Area||Basal Area||Relative Basal Area|
|Red Oak||245.21 cm2||55123.21 cm2||11 %|
|Bigtooth Aspen||471.44 cm2||19894.77 cm2||4 %|
|Blue Beech||78.54 cm2||3314.39 cm2||1 %|
|Black Locust||598.30 cm2||319492.2 cm2||64 %|
|Sugar Maple||355.10 cm2||29934.93 cm2||6 %|
|White Pine||222.76 cm2||18778.67 cm2||4 %|
|Hop Hornbeam||143.41 cm2||50379.93 cm2||10 %|
|Black Cherry||78.54 cm2||3314.39 cm2||1 %|
The majority of the data in this table has very small values. In fact when it came to relative basal area the only species that had values over 11 % were Red Oak and Black Locust. Table 4. Frequency and relative frequency by species of trees on Pine Hill from 09/12/13.
|Red Oak||0.16||16 %|
|Bigtooth Aspen||0.03||3 %|
|Blue Beech||0.03||3 %|
|Black Locust||0.38||38 %|
|Sugar Maple||0.06||6 %|
|White Pine||0.06||6 %|
|Hop Hornbeam||0.25||25 %|
|Black Cherry||0.03||3 %|
From this table we can see that most tree species have fairly low relative frequencies (table 4). Therefore most tree species had relative frequency under 6 %. In fact only 3 tree species had values over this amount. Those species were Red Oak, Black Locust, and Hop Hornbeam.
Table 5. Importance value and relative importance value by species of trees on Pine Hill from 09/12/13.
|Species||Importance Value||Relative Importance Value|
|Red Oak||43||14 %|
|Bigtooth Aspen||10||3 %|
|Blue Beech||7||2 %|
|Black Locust||140||47 %|
|Sugar Maple||18||6 %|
|White Pine||16||5 %|
|Black Cherry||7||2 %|
This table shows the relative diversity of trees (table 5). This data is more balanced than the data of the other calculations. Black Locust accounts for only 47% of relative importance value. The figure below allows us to visually see the data (figure 1).
Figure 1: Relative importance values for species of trees found on Pine Hill on 09/12/13.
A Red Oak was cored. From that core sample the age of the tree was determined by counting the lines to the mid-point of the tree. The cored tree was 53 years old and had a breast height basal area of 706.86 cm2.
From this lab we learn a great deal about the plant community on Pine Hill. The statistics of the most value to us is arguable the relative importance value. Relative density, relative basal area, and relative frequency are all attempts to quantify the data coinsuring the abundance and dominance of each species. While they are great number to have relative importance value takes each of these values into account when trying to determine the importance of each species. Therefore, it is the most reflective of the population. However relative basal areas tells us about the size of each tree trunk, relative density tells us how the trees are distributed across space and relative frequency tells us how common each species is to Pine Hill.
From the numbers calculated diversity of the forested slope can be determined. From the relative basal area for example we see when it comes to just area size the forest is dominated by Black Locust which has a relative basal area of 64 % (table 3). However when we look at other factors besides size, like relative frequency and relative density, we see that the forest is not that dominated by Black Locust as we think as it makes up just 38% of relative frequency and relative density (tables 2 and 4). The different between these three numbers appears to be an issue of size. Black Locusts are may be just larger than the other species. This may also be due to the fact that two of the Black Locusts had basal areas of 1000 cm2. Relative importance value eliminates these conflicts by balancing all of the values.
From figure 1 we can visualize the diversity of the forested slope behind Ann’s House by using the relative importance value (figure 1). It is clear from this graph that the dominant trees are Black Locust, followed by Hop Hornbeam, and Red Oak. It is also clear that the other species make up just a faction of the forest.
The core sample also provides us with valuable information about our forest. The red oak was 53 years old and had a breast height basal area of 706.86 cm2. We can determine that all red oaks with around a basal area of 706.86 cm2 are around 53 years old. If there are a number of trees around the same size and species as that tree we can determine that the forest is at least 53 years old. In addition we could also examine different ages along the core sample by counting annuli backwards from the center. From there we can determine basal area. That data would allow us to make guess about the different ages of trees that are red oaks.
This data has allowed us to draw a number of conclusions about Pine Hill. We now know the dominate trees, the trees with the largest basal area, the density of trees, and can estimate the ages of our Red Oaks. This information is extremely important if any future studies are to be done on the plant community of Pine Hill.
ENVS240. 2013. Laboratory Handout: Lab #2: Vegetation sampling. Alfred University, Alfred, New York, USA.
PBIO425. 2013. Laboratory Handout: Forest Vegetation Sampling and Point-centered Quarter Sampling Method. Ohio University, Athens, Ohio, USA.