“The impact of disturbance on the trees with its understory plant and how it cause of changing species density, frequency and dominant species.” November 16, 2012
Have you seen films that to re-enact the past? There are huge grasslands and wildflower-filled landscapes from the past that are restored in the movies. Today, however, as industrialization and agricultural land grows, the ecosystem is decreasing. People tried reconstruction of ecosystem to make up for the reduction of it. However, initial attempts failed because people were not aware of the fact that natural disturbance had importance in maintaining the ecosystem communities. For succession in restoring communities, people began thinking and asking themselves: What adjusts the relative abundance of species within the communities? What relates to the physical environment and the communities? How do the communities change over time? People explore and understand these questions to develop community ecology. We specifically will study the relationship between disturbances and species diversity within communities. A disturbance is a physical environment changing that interferes in community structure and function. (Heather, 2012) In a forest, disturbance results in open space or gap. In our case, the canopy trees were removed which affects the Herbaceous layer. This disturbance causes increasing light and soil temperature while soil moisture and relative humidity is reduced. So we investigated how this disturbance affects community structure and what patterns in the landscape will appear. To understand what disturbance is, and its effects on species diversity, we compared and contrasted two plots, one plot that has been disturbed recently by removal of the canopy trees and the other which is covered by mature forest. The data of the highest dominance (trees only), frequency (understory only), and density were collected for this study to figure out similarities and differences between two plots. Also Jaccard’s coefficient of similarity and Shannon-Weiner index of diversity values are calculated to help to understand species diversity of the two plots. We would expect that there are differences of dominance species, density and frequency in the trees and Herbaceous layer because the disturbance results in open space or gap in forest. Method
Two plots that measure 10m by 20m were prepared on the University of New Brunswick campus in Saint John, New Brunswick on October 9, 2012 on a sunny day after 1:30pm. The temperature was between 7 and 13 degrees and humidity was approximately 70percent. New Brunswick is located between deciduous forest zones and boreal evergreen forest and also Saint John is located with Fundy Coastal. Each plot was marked off with flagging tape on the corners to help to indicate the valid area. The 1m2 quadrats are laid out five times in each disturbed plot and undisturbed plot. The quadrat should be distributed as much as possible in order to capture as much of variability of the plot. Within each 1m2 quadrat, all individuals of each species were counted and identified to get a measure of species diversity (frequency) and density. Also the life form of each species was recorded.
Each tree species were counted and identified and also its diameter breast height were recorded that only for trees > 1cm to get a measure of dominance and density. The condition of the tree was also recorded (living or dead). After recording data of each tree, they were marked with a piece of chalk to prevent measuring the same tree twice. If sapling tree that between 1 ~ 3 cm in diameter is found, then all sapling tree is indicated. All trees were grouped 1-5 cm, 5-10 cm, 10-15 cm, 15-20 cm,20-30 cm, >30cm to get some helpful information of the successional stage and age structure of the tree. (Figure 1, 2)
Figure 1: A size frequency diagram of the most abundant tree species which is Trembling aspen in 20m x...