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Evaluating the Effects of Competition and Quantification of the Lotka-Volterra Competition Coefficients
Allegheny College Department of Biology and Environmental Science

By:  Albrando Lorenzo Lucino Jr, B.S,B.A


Biological populations of terrestrial plants, just like terrestrial animals are affected by competition and this can be manifested by a change in population number in the positive or negative aspect, particularly as a negative effect the first population has on the growth rate on the second population. If there are two populations in a given environment and if both are competing for a common resource pool, then the better competitor will get the larger share and the weaker competitor gets a lesser share; thus translating into a reduced growth rate. The use of the Lotka-Volterra method will allow one to examine the competitive interaction between two species and to predict the outcome.  This particular method requires the knowledge of how each population affects one another, particularly the competition coefficient quantifies the effect of an individual of one species on the growth rate of the population of the second species as if the first species were an individual of the second species. We will be the observing two terrestrial plants, particularly oats and radishes and observe the two have intraspecific as well as interspecific competition. The purpose of the paper is to test the hypothesis that test the hypothesis that oats are superior competitors than radish early in early growth. The reason for this is that biologically speaking, radish plants invest too much energy on the growth of root production, which would benefit them in later growth years, but as of consequence, they are not as effective in competing for light. 

The importance of understanding population competition because it is critical in understanding how one population will be affected by another population in terms of reproduction and growth rate. The hypothesis that was presented in the introduction of this paper was that oats are superior competitors over radish in their early growth period because radish plants commit too much of an enormous amount of energy to rood production, which are the edible part of their physiology  and as a result they are not as effective in competing for light. This hypothesis has been supported from analyzing the data results, which indicate that radishes are indeed k-strategists, which means that they place a great deal of emphasis on strategic growth and longevity and individual survivalship whereas oats are more of a r strategists, which means that these terrestrial plants place greater resource emphasis on reproduction. From the observance of Table 2, one can observe that the per capita intraspecific competition was higher in radishes than it was on oats with radish per capita at .0094 and oats at .0080. Additionally, the data from Table 3 also indicates that radishes have a higher interspecific competition per capita than oats with radish per capita at .0043 and oats at .0032. The Lotka-Volterra competition coefficients also indicate that radishes have a higher frequency of .4574 than oats, which had a rate of .4000. The graph shown in Figure 1 also indicates that radishes do poorly in the beginning, but eventually last longer than the oats, due to the investment radishes have in their roots, which allow them to compete better with oats when soil nutrients became a limiting factor. Due to the time constraints of this lab, we were not able to observe the eventual long term dominance of radish, but only see the short term dominance of oats. Both populations can coexist, but only with periodic disturbances.



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