The Biological Competitive Exclusion Principle

For a species to survive and flourish within a given environment, it not only needs to replace itself but also all the other species around it exclusively. Hence, if one species completely replaces another species, the result is a single dominant species, a monoculture (source 2). According to Gause’s law, every species in a given environment occupies different niches for survival. Therefore, two separate species competing for similar resources cannot fundamentally coexist (source Gause). This is known as the competitive exclusion principle. When comparing animal niche’s to that of different autotrophic plants, one can rather easily differentiate adequate ecological niches for the animal species merely based on food-requirements (P.J. Grubb). On the contrary, many autotrophic plants contradict the competitive exclusion principle by sharing similar ecological niches such as sunlight, carbon dioxide, water, and alike mineral nutrients (p.j. grubb).

Many old-growth forests across the landscape of northern Lower Peninsula of Michigan contain a mixture of tree species rather than a monoculture. Many researchers have put forward ideas to explain the competition and co-existence of tree species in such communities. A theory explaining competition and co-existence between two species is gap regeneration. Gap regeneration is when a gap is created upon death of a plant individual and a new individual, sometimes of the same species as died and sometimes not dependent on environmental heterogeneity, takes its place (Kenneth Lertzman). Canopy gaps during gap regeneration can be explained by either reciprocal replacement or habitat preference . In a reciprocal replacement, seedlings of one species would be found predominately under large trees ...

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...le would be more than that of American beech because sugar maple produce more seeds than American beech. Furthermore, we study whether the two species co-exist via reciprocal replacement, habitat preference or merely by chance. We believe that habitat preference may be the mechanism of coexistence here and therefore we hypothesize that there will be more American beech tree neighbors as they may represent the most biomass as per our third hypothesis. Thereafter, root sprouting is effective in American beech to give them a greater horizontal growth than sugar maple. Hence, we hypothesize that sugar maple canopies will be less asymmetrical than American beech. Finally, because a nearby canopy may restrict a tree canopy growth in the same direction, we hypothesize that a tree will grow its respective canopy away from its neighboring canopy to receive maximum sunlight.