AGEC 2370 Intra & Interspecific Plant Competition Adam Borton Student #7695780, Group 7 Introduction: Plant growth and development depends on a variety of environmental factors. This includes nutrient availability, available sunlight and competition between plants. Competition between plants of the same species and plants of different species can affect the plant structure of a community. Competition between differing plant species is known as interspecific competition. Interspecific competition usually causes an increase in biomass of one species, while decreasing population biomass or density in another (Tilman, 1997). In this lab, we observed how seed density and plant competition effect parameters of plant growth and survivorship of plants. Materials and Methods: We began this experiment on October 7th, 2014 in the Animal Sciences Building. On this day we planted 9 pots of barley and canola using varying seed densities. The seed densities for the pots were 10 seeds/pot, 30 seeds/pot and 90 seeds/pot. The amounts of each type of plant were altered in each pot with some pots having just one type of plant and others having both. This was done to simulate interspecific competition and intraspecific competition in order to gain understanding of how each type of competition may effect plant growth. Interspecific competition between the barley and canola always involved equal amounts of both (for example, in the 90 seed density pot, 45 barley plants and 45 canola plants were planted). After the seeds were planted, the pots sat for 5 weeks and underwent 16 hours of light and 8 hours of darkness daily. On November 18th, 2014 we recorded the proportion of plants which survived in each pot. 1 The plants were given a numerical value and then 10 were selected using a random digits table. Once the 10 plants were chosen, plant height, number of leaves and leaf area were measured and recorded. When measuring plant height, the length was recorded based on the distance from the bottom of the stem, to the bottom of the uppermost, dominant leaf. When recording number of leaves, dry, brown leaves were excluded and small cotyledons were included. After the data was obtained, the entire class pooled the results and means for proportion of survivors and each parameter of growth were calculated. Standard error of the mean was also calculated for each. Results: For barley planted with interspecific competition, it appears the mean proportion of survivors decreases as seed density goes up (Table 1). The same was true for canola under interspecific competition, which also decreased as seed density went up (Table 1). For intraspecific competition, the proportion of survivors for barley changed very little as seed density went up. Proportion of survivors fluctuated a little for canola intraspecific, as it decreased at 30 seeds but then increased again in the 90 seed pot (Table 2). Mean plant height decreased as seed density went up for interspecific barley and interspecific canola (Table 1). Mean plant heights of intraspecific barley and canola appeared to fluctuate a little but did not decrease as much (Table 2). When observing the mean number of leaves and mean area of leaves for both canola and barley, interspecific competition resulted in a decrease in leaves and a strong decrease in leaf area as seed density increased (Table 1). The same was true in the intraspecific pots for canola and barley, with number of leaves and mean leaf area strongly decreasing as seed density increased (Table 2). When comparing the graphs of plant height for barley under interspecific and intraspecific competition conditions, there appears to be relatively little interaction. This is 2 because the mean plant height calculated at each of the three seed densities show approximately the same amount of decrease in both interspecific and intraspecific tests which suggests little interaction (Figures 1 and 2). This differed from the canola plants which were subjected to interspecific and intraspecific competition. Plant height increased from a seed density of 10 to a seed density of 30 in intraspecific competition, but decreased in interspecific competition. The means moving in opposite direction suggests there is some interaction between the two test subjects (Figures 3 and 4). Discussion: I think both intraspecific competition and interspecific competition were observed in this laboratory based on the fact that for most growth parameters, as seed density went up, many of the values decreased. Whether the competition be between the plant of the same species or that of another species, many of the growth parameters decreased as plant biomass increased possibly due to the lack of availability of water and nutrients or access to adequate light. On average, based on the data calculated in this laboratory, both intraspecific competition and interspecific competition had similar effects on how well the plants did. When comparing both barley and canola, often times interspecific competition would result in higher values for most plant parameters. However, the inverse was true where intraspecific values would be higher than interspecific values for both plants. This idea makes sense in the fact that interspecific differences between plants may cause different plant species to behave differently (Tilman et al. 1997). This idea may explain why such differences in values are observed between canola and barley for intraspecific and interspecific competition. As plant biomass increases, competition for availability of light becomes the key factor as light powers many of the plants essential functions. (Aerts, 1999). The plants were exposed to 16 3 hours of light a day, meaning they were getting plenty of sunlight. As the seed densities rise, many of the mean growth parameters begin to decrease. This could be a direct result of some plants becoming outcompeted for sunlight leading to less growth. This hypothesis could be tested by altering the amount of sunlight the plants received daily and then comparing the results to this experiment. If you decreased the light available from 16 hours to possibly just 8 hours and then observed less growth for all parameters, you could potentially conclude that sunlight is a critical factor in how well the plants do. You could test the opposite as well, perhaps increasing the sunlight and then observing what effect it has on the plants as well. A source of error when calculating leaf area could have occurred when determining the length and width of the leaves. Getting the precise spot where the leaf begins to determine the length was often times left to our judgment. Similarly, when determining the width, you would need to measure the point which maximizes the width, by measuring the leaf at is widest point. Variability in these locations may cause slight variability in answers. Another source of error could be the formulas used to calculate the area of the leaves. Leaves vary in shape considerably. Because of this, I would conclude that it is highly unlikely that the formulas used for both barley and canola can calculate perfect area of the leaves because of the variation of shape amongst the leaves. This would lead to overestimation and underestimation of total areas leading to more of an estimate on leaf area then a reliable precise calculation. 4 References: Aerts, Rien. "Interspecific competition in natural plant communities: mechanisms, trade-offs and plant-soil feedbacks." Journal of Experimental Botany 50.330 (1999): 29-37. Tilman, David, Clarence L. Lehman, and Kendall T. Thomson. "Plant diversity and ecosystem productivity: theoretical considerations." Proceedings of the National Academy of Sciences 94.5 (1997): 1857-1861. Tilman, David. "8: Mechanisms of Plant Competition", Plant Ecology, 2nd Ed.; Blackwell Science, Oxford, England (1997). Pp 239-261. 5 Tables and Figures: Table 1 Seed Density Barley Interspecific Canola Interspecific Barley Interspecific Canola Interspecific Barley Interspecific Canola Interspecific Mean plant height Mean # of leaves / plant Mean leaf area 10 Mean proportion surviving 0.91 18.38 4.38 97.92 10 0.89 14.29 4.06 40.28 30 0.87 18.72 4.16 72.97 30 0.83 9.99 3.83 16.14 90 0.84 17.28 3.63 41.06 90 0.65 9.15 3.60 10.44 Seed Density Mean plant height Mean # of leaves / plant Mean leaf area 10 Mean proportion surviving 0.93 18.96 4.68 87.75 10 0.86 12.82 4.81 56.83 30 0.90 15.52 3.76 51.44 30 0.75 13.26 4.46 29.91 90 0.91 15.17 3.43 31.64 90 0.83 11.50 3.54 16.16 Table 2 Barley Intraspecific Canola Intraspecific Barley Intraspecific Canola Intraspecific Barley Intraspecific Canola Intraspecific 6 Table 3 Seed Density Barley Interspecific Canola Interspecific Barley Interspecific Canola Interspecific Barley Interspecific Canola Interspecific SEM for plant height SEM for # of leaves / plant SEM for leaf area 10 SEM for proportion surviving 0.022 1.324 0.089 2.825 10 0.032 0.871 0.195 2.758 30 0.025 0.590 0.073 2.889 30 0.013 0.440 0.083 0.923 90 0.007 0.851 0.076 1.727 90 0.028 0.247 0.104 1.059 Seed Density SEM for plant height SEM for # of leaves / plant SEM for leaf area 10 SEM for proportion surviving 0.007 0.594 0.098 3.398 10 0.046 1.124 0.101 3.732 30 0.008 0.460 0.058 1.716 30 0.027 0.625 0.039 1.578 90 0.010 1.039 0.055 1.025 90 0.019 0.449 0.086 0.83003 Table 4 Barley Intraspecific Canola Intraspecific Barley Intraspecific Canola Intraspecific Barley Intraspecific Canola Intraspecific 7 Barley Interspecific Competition 40.00 Plant Growth (cm) 35.00 30.00 25.00 20.00 15.00 10.00 5.00 0.00 0 10 20 30 40 50 60 70 80 90 100 Seed Density Figure 1: Barley Interspecific Competition effect on Plant Height Barley Intraspecific Competition 35.00 Plant Height (cm) 30.00 25.00 20.00 15.00 10.00 5.00 0.00 0 20 40 60 80 100 Seed Density Figure 2: Barley Intraspecific Competition effect on Plant Height 8 Canola Interspecific Competition Plant Height (cm) 25.00 20.00 15.00 10.00 5.00 0.00 0 20 40 60 80 100 Seed Density Figure 3: Canola Interspecific Competition effect on Plant Height Canola Intraspecific Competition 30.00 Plant Height (cm) 25.00 20.00 15.00 10.00 5.00 0.00 0 20 40 60 80 100 Seed Density Figure 4: Canola Intraspecific Competition effect on Plant Height 9 Appendix: Sample Calculation for calculating mean: Calculation uses data from Barley Interspecific: mean proportion surviving (10 seeds) Mean proportion surviving = Mean proportion surviving = ๐ ๐ข๐ ๐๐ ๐๐๐ ๐๐๐๐๐๐๐ก๐๐๐๐ ๐๐ ๐ ๐ข๐๐ฃ๐๐ฃ๐๐๐ # ๐๐ ๐ก๐๐๐๐๐ 0.60+1+0.80+1+1+1+1 7 ๐ก๐๐๐๐๐ Mean proportion surviving = 0.91 Sample Calculation for calculating SEM: Calculation uses data from Barley Interspecific: mean proportion surviving (10 seeds) SEM = √s2 / n Variance = ∑ (Ni – Mean N)2 / n – 1 Variance = (0.61 – 0.91)2 / 7 – 1 Variance = (-0.3)2 / 6 Variance = 0.015 Calculations remain the same for each group’s data Variance = ∑ 0.015 + 0.00135 + 0.002017 + 0.00135 + 0.00135 + 0.00135 + 0.00135 Variance = 0.023767 SEM = √0.023767 / 7 SEM = 0.022 10 Sample Calculation for calculating leaf area for Canola: Area calculated below is for one leaf: π Area = ( 4 ) ( ๐ค๐๐๐กโ+๐๐๐๐๐กโ ๐๐ ๐๐๐๐ 2 ) 2 π Area = ( 4 ) (3.8 + 3.9)2 / 2 Area = 11.6 Continue to calculate area for each leaf for all 10 plants Sum areas together and divide by number of plants Area = ∑ of all leaf area for 10 plants / 10 plants Sample Calculation for calculating area for barley plants: A = length x width A = 16.2 x 3.4 A = 55.08 Continue to calculate area for each leaf for all 10 plants Sum areas together and divide by number of plants Area = ∑ of all leaf area for 10 plants / 10 plants 11 Initial of all members group (copy in all rows) Group # (copy in all rows) Seed density treatment mean proportion surviving mean plant height mean number of leaves / plant total leaf area / plant MT, KA, AB, JP 7 90 Barley Intraspecific 0.9 9.7 3.2 27.74 MT, KA, AB, JP 7 90 Canola Intraspecific 0.76 12.8 3.5 13.9 MT, KA, AB, JP 7 90 Barley Interspecific 0.96 13.81 2.9 29.32 MT, KA, AB, JP 7 90 Canola Interspecific 0.71 10.64 3.7 5.03 MT, KA, AB, JP 7 30 Barley Intraspecific 0.93 13.81 3.7 57.2 MT, KA, AB, JP 7 30 Canola Intraspecific 0.83 12.68 4.7 31 MT, KA, AB, JP 7 30 Barley Interspecific 0.67 12.3 3.9 64.55 MT, KA, AB, JP 7 30 Canola Interspecific 0.73 10.8 3.6 13.6 MT, KA, AB, JP 7 10 Barley Intraspecific 0.9 14.97 3.7 67.64 MT, KA, AB, JP 7 10 Canola Intraspecific 0.7 16.7 4.5 47.9 MT, KA, AB, JP 7 10 Barley Interspecific 1 17.68 3.4 90.5 MT, KA, AB, JP 7 10 Canola Interspecific 0.8 14.95 5.5 26.78 12 Group # 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 Seed density 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 30 30 30 30 30 30 30 30 30 30 treatment Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific mean proportion surviving 0.60 1.00 0.80 1.00 1.00 1.00 1.00 0.90 0.90 0.90 0.90 1.00 1.00 0.90 1.00 0.40 1.00 1.00 1.00 1.00 0.80 0.90 1.00 1.00 1.00 0.60 0.80 0.70 1.00 1.00 0.60 1.00 0.80 1.00 0.67 0.93 0.87 0.83 mean plant height (cm) 17.88 8.70 14.00 18.08 14.30 38.00 17.68 19.28 19.80 18.22 19.17 14.30 27.00 14.97 13.87 21.52 5.40 13.56 8.70 22.00 14.95 9.67 8.84 7.65 18.29 26.60 22.00 16.70 20.82 17.19 17.50 18.61 18.63 26.00 12.30 16.40 10.00 17.81 mean number of leaves / plant 4.20 4.50 3.75 4.80 5.00 5.00 3.40 4.33 4.56 4.67 4.78 6.00 4.71 3.70 4.00 4.20 3.60 4.80 1.33 5.00 5.50 5.56 4.40 3.80 5.80 4.50 5.10 4.50 4.10 3.90 4.40 3.70 3.90 5.20 3.90 3.40 3.20 4.40 13 total leaf area / plant (cm2) 97.84 136.65 96.25 70.36 93.20 100.62 90.50 76.80 126.88 106.46 85.48 57.00 94.00 67.64 41.46 37.26 40.37 20.87 34.52 80.70 26.78 31.95 45.67 52.62 35.66 79.12 104.89 47.90 67.34 59.49 67.34 55.26 114.68 82.12 64.55 37.32 57.63 66.37 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Interspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Barley Intraspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Interspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific 0.80 0.93 1.00 0.93 0.80 0.87 1.00 0.80 0.73 0.86 0.73 0.97 0.47 0.57 0.97 0.73 0.73 0.83 0.84 0.78 0.64 0.91 0.96 0.77 0.96 0.94 0.92 0.76 0.92 0.93 0.98 0.90 0.44 0.38 0.91 0.80 0.76 0.57 0.71 0.98 0.61 0.73 14.60 15.85 20.20 13.81 7.77 10.53 6.70 10.17 7.96 16.00 10.80 11.00 10.92 7.50 16.53 13.19 21.00 12.68 14.21 13.95 16.60 19.02 13.39 30.00 13.81 10.72 11.92 14.55 12.70 15.62 31.00 9.70 7.68 8.77 8.75 9.32 6.90 12.00 10.64 11.02 9.50 9.40 4.00 3.60 4.00 3.70 4.50 3.70 3.40 3.30 3.50 4.80 3.60 4.90 4.50 4.40 4.20 4.10 4.42 4.70 3.40 3.50 4.10 3.20 3.90 4.42 2.90 2.90 3.40 4.00 3.30 3.30 3.89 3.20 4.50 4.30 3.30 2.80 2.60 4.00 3.70 3.60 3.10 2.70 14 60.37 35.26 45.93 57.20 15.46 5.78 18.70 22.31 24.87 12.26 13.60 31.45 25.15 37.42 28.20 45.98 10.20 31.00 45.51 41.91 41.45 27.62 37.65 63.99 29.32 35.25 42.71 37.33 30.95 24.53 23.00 27.74 7.45 5.78 5.32 16.82 24.51 8.19 5.03 10.92 16.29 11.73 4 5 6 7 90 90 90 90 Canola Intraspecific Canola Intraspecific Canola Intraspecific Canola Intraspecific 0.96 0.79 0.95 0.76 15.66 7.10 15.00 12.80 4.10 3.30 4.50 3.50 15 17.37 28.26 14.67 13.90