The Effect of Human Disturbance on insect abundance and the total number of different plants and insects

Method: Group members: Afra, Maham, Farinaz and Sana The purpose of this experiment is to assess the effect of high, intermediate and low human disturbed land on the insect & plant abundance and on the number of different plant and insect species present. Human activities have long been known to impose both spatial and temporal patterns on insect abundance and diversity. According to the Intermediate Disturbance Hypothesis (IDH), species diversity is maximized when the ecological disturbance including human influences like forest deforestation is neither too uncommon nor too frequent (Roxburgh et al 2004). Thus, I hypothesize, that the site with intermediate human disturbance would possess the greatest amount of different plant and insect species. Whereas, I hypothesize that the site with high human disturbance will possess the least number of different plant and insect species in the quadrat. I also hypothesize that the highest insect abundance will be found in the site with low human disturbance while the lowest insect abundance will be present in site with high human disturbance This data could be used for conservation purposes as human activity directly impacts the environment. The data can help quantify how the number of plants and insects vary with each disturbed site (high, low or intermediate). Furthermore, the data also allows us to determine if human disturbance negatively impacts plant and insect diversity. Data collection from these three sites took place on Oct. 17, 2014 from 3:00pm to 4:30pm and Oct 24 from 3:00pm to 5:00pm. The temperature on Oct. 17 was about 16°C and was associated with periods of light rain prior to the sampling while on Oct. 24, it was sunny with a temperature of about 17°C. For this experiment three 20m x 20m sampling sites, with a total area of 400 m² /site, were selected and differentiated based on the level of human disturbance present. To measure the 20m x 20m sampling area transects were laid down perpendicular to each other to give an area of 400 m² /site. Vegetation cover was used to assess the level of human disturbance present. The percent cover of all vegetation, including grass, was estimated by observing how much the ground was covered by grass and any other vegetation in each site using quadrats (1m x 1m). The percent cover of all vegetation was also estimated based on how much of soil was visible in each quadrat. A vegetation cover of 80% or higher classified the sampling site as having low disturbance. A vegetation cover of 50-79% classified the sampling site as having intermediate disturbance while a vegetation cover below 50% was classified as a highly disturbed site. Using this criteria, the Grassland near Danby woods of York University, keel campus was selected as the site with intermediate level of human disturbance while the forest near the Pond Road was selected as the site with low human disturbance. Lastly, area near Vanier College at York University was selected as the site with high human disturbance. All 3 sites were sampled 25 times. Randomness of data collection from each 20m x 20m sampling site was achieved by making a numbered grid of each sampling site with 1m x 1m blocks giving a total of 400 possible blocks for sampling. The numbers on the grid (1-400) were then put into a random number generator which then selected the 25 random sites where the quadrats were placed. Within each quadrat placed, the total cover of all vegetation, insect abundance and the different number of plant and insect species was determined. Within the 1m x 1m quadrat, a sweep nets (with a 35 cm diameter) placed 10cm above the ground was used to determine insect abundance and total number of different insect species. The sweep net was swept back and forth for 1.5 minutes to collect the insect data within each quadrat. The insect abundance and the total number of different insect species was the noted based on what was captured in the sweep net. Different number of plants was determined by observing the plants in the quadrat. Only those plants that had their roots within the quadrat were included. References Roxburgh, S.H., Shea, K. and Wilson, J.B. 2004. THE INTERMEDIATE DISTURBANCE HYPOTHESIS: PATCH DYNAMICS AND MECHANISMS OF SPECIES COEXISTENCE. Ecology. 85(2): 359–371.