Adeline Payne
Biology 320 (Lab)
24 September 2018
Specie Similarity of Old and Secondary Growth Forests in Wesselman Woods Nature Preserve
Methods
Study site & Species¬—The experiment was conducted at Wesselman Woods Nature Preserve (WWNP), a state nature preserve located in Evansville, Indiana. Consisting of trees over 400 years of age, WWNP has prevailing populations of sweetgum and tulip poplar trees along with high numbers of the classic oak and maple species (Karns et al., 2008). The average basal area of Wesselman’s is 187 square feet per acre, which is the highest of any recorded comparative woods in Indiana (Lindsey et al., 1969). The acres consist of both old growth (OGF), due to it never having been harvested, and secondary growth forest (SGF), due to its natural spreading of seeds via human and animal interaction. The difference in diversity, through evaluations of species richness and evenness as well as total basal area alludes to a significant distinction between OGF and SGF.
Experimental Design—In the summer of 2015, twenty-seven (50 m x 4 m) transects in each forest type were evaluated throughout Wesselman Woods. Within these rectangular transects, diameter at breast height (dbh) was measured on tree species with a diameter of 10 cm or above and a trunk mostly within the transect. Breast height was determined to be 1.3 meters up from the base of the tree. The circumference at this height was measured in centimeters then divided by to attain the true diameter. Upon acquiring a dbh, the tree was identified and recorded by deducing physical characteristics like leaf shape, branching pattern and stem length, to a specific species (Shaw, 1981).
Analysis¬—The purpose of this experiment is to evaluate tree species diversity between the old growth forests and secondary growth forest of WWNP using a series of measurements and calculations. One such calculation being basal area yields data that quantifies the amount of woody biomass that makes up the transect using the dbh measurement (Opie, 1970). Once dbh was gathered, it was then used in the basal area (Ba) calculation to compute any differences among transects. The basal area equation is as follows:
BA=*(dbh/2)2
There are two key aspects to diversity, one of which being species richness, or the number of species in a given community and the other being species evenness. For the experiment, species richness was a necessary calculation used to evaluate the relationship between the number of species and the number of individuals within that given species. Species richness can be calculated using Margalef’s Index (Da) which can then aid in the quantitative comparison between the old and secondary growth forests (Margalef, 1958). Margalef’s Index is as follows:
Da =(s-1)/log10N
To calculate species evenness, the Shannon Wiener Diversity Index (H’) was utilized. This equation formulates the relative abundance and evenness of a specific species within a community (Shannon, 1948). Each transect for each forest type has its own H’ value based off the total number of species within the transect and their relative abundance. The Shannon Wiener Diversity Index (H’) calculation is as follows:
H’= - (pi*lnpi)
The Jaccard coefficient (CCJ) is another tool used to calculate overlapping similarities between forest types in a given environment. The equations can quantify, as a percentage, the number of certain species (c) that reside in a given forest and compare it to the total number of those species (S) in both forest types (Vargas, 1996). This information is relevant when discussing species diversity in a community because it exhumes significant differences between comparative areas. The Jaccard coefficient (CCJ) equation is as follows:
CCJ = c/S *100
Results
To differentiate between old growth forest and secondary growth forests tree species diversity, all of these calculations are imperative. A significant difference between OGF and SGF gives insight into the innerworkings of communities and how they come to be as well as what sets them apart from each other. Data collected across all 54 transects was evaluated using Microsoft Excel and AVONA in the JMP software, version 2018. Twenty-three species were identified and utilized in the calculations of diversity. Once computed, the secondary growth forest yielded the most abundant amount of Ash trees, while the old growth forest was overshadowed by American elms (Table 1).
Table 1. Species occurrence and number of individuals within a given species in old growth and secondary growth forests.
SPECIES # in OGF # in SGF
American elm 31 12
Ash 8 88
Blackgum 8 /
Black Cherry 1 2
Bitternut Hickory 1 /
Boxelder / 9
Chinkapin Oak 1 /
Hackberry 18 2
Mockernut Hickory 5 /
Musclewood 14 /
Northern Red Oak 1 /
Pawpaw 1 /
Pin Oak 1 /
Red Oak / /
Red Maple 17 11
Sassafras 14 3
Shagbark Hickory 5 /
Shumard Oak 1 /
Sugar Maple 49 /
Swamp White Oak 1 /
Sweetgum 22 /
Sycamore / 87
Tulip Poplar 7 15
The two different forest types could have their evenness differentiated by use of the Shannon Wiener Diversity Index (H’) calculation since it considers the number of individuals within a given species. The Shannon Wiener Diversity Index (H’) was 1.54 ± 0.059 (x̅±SE) in the old growth forest and 1.05 ± 0.06 in the secondary growth forest (Figure 1). Thus, the old growth forest has significantly more diversity than the secondary growth forest in Wesselman Woods Nature Preserve.
Figure 1. Bar graph depicting mean species diversity between old growth forest and secondary growth forest. Error Bars represent standard error. The data suggests that the old growth forest had significantly greater diversity than the secondary growth forest (F1,48=31.5, P=0.0001)
Using the subtotal of a transects multiple diameter at breast height (DBH) calculations, basal area was able to be manipulated and evaluated in JMP. The basal area (Ba) was 48.9 ± 5.5 for old growth forest (x̅±SE) and 29.2 ± 2.4 for secondary growth forest (Figure 2). This data concludes that the OGF has significantly more overall basal area than the SGF.
Figure 2. Bar graph depicting mean Basal Area (Ba) between old growth forest and secondary growth forest. Error Bars represent standard error. The data suggests that the old growth forest had significantly greater basal area than the secondary growth forest (F1,48=10.7, P=0.002)
The Margalef’s Index (Da) was computed by using the number of species in a given transect to evaluate evenness. The Margalef’s Index (Da) for old growth forest was 5.3 ± 0.27 (x̅±SE) and 3.65 ± 0.21 for secondary growth forest (Figure 3). With this, richness is significantly greater in the old growth forest than the secondary growth forest.
Figure 3. Bar graph depicting mean species richness between old growth forest and secondary growth forest. Error Bars represent standard error. The data suggests that the old growth forest had significantly greater richness than the secondary growth forest (ANOVA, F1,48=47.1, P=0.0001)
The Jaccard Coefficient (CCJ) when accounting for all 23 species was computed to 39%. This equation represents the similar species shared between the old and secondary growth forest of WWNP. The percentage is relatively small, therefore there is a low level of shared tree species between the two forest types, furthering the discrepancy amidst the two.
Works Cited
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