Plant Competition

Plant Competiton By Tobi Ojelade Competition is a natural occurrence between organisms occupying the same space at the same time, competition can occur with organisms of the same species or different ones, density dependency is one of the main types of completion between plants that can transpire this equal relationship between slowing down a population and increasing one with amount cover between these given species, this idea can directly correlate with ideas from an experiment by Wendy Ridenour of how noxious invasive weeds can decrease or affect plant growth rate of a native species by density dependant factors and chemical mechanisms.

Competition is defined as the reduction of fitness to the sharing of resources. Plants compete for many different resources in the environment, like water, minerals, mates and room. Different plants need different amounts of these resources. Plants also can compete for sunlight. Even though, plants can always acquire sunlight, when neighboring plants overpower and over tower you, they tend to use up the light energy before it gets to ground level. There are many mechanisms and means behind the study of competition.

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Competition can be depicted as inter-specific or intraspecifically, meaning competition between same species and different species. Studies have later classified competition in three forms: Interference competition, which is a direct interaction between species for resources. This direct interaction limits both species abilities and fitness. Resource competition is the non contact interaction, in which two species compete but in different ways for the same resource. For example, if one tree grows taller than the other, and uses this to exploit sunlight from the other one, this is resource competition.

Finally, is apparent competition, which shows how a third species can prey on two species and affect either’s population or fitness. Competition can be measured in different ways and has been the source of research for many years. Relative Competitive Index (RCI) is the first system used, where the plants performance is subtracted and divided by the population in the monoculture. Similar to this equation is the ACI, absolute competition index, which simply measures the difference between the performance and the population. These two equations however aren’t very accurate as they give relative ratios not definite stats.

Nevertheless, the log phase, denoted (LRR) and the relative efficiency index (REI) give a more accurate competitive assessment, by actually utilizing absolute figures instead of relative statistics. Ridenour and Callaway measured competition using different mechanisms. In the article, they seek out to investigate the specific roles of root allelopathy in overall plant to plant competition between Centaurea and Festuca species. Also, a goal was to figure out how some invasive species so easily dominate over a native one. Their experiment sampled herbaceous vegetation in a prairie with both species present.

They had three cites, categorized as low, moderate and high invasion of Centaurea. They mainly exhibited and explained how the presence of Centaurea affects the population of other native plants. Analyzing the graph, you can see how as the population of Centaurea increase the native plants decrease. They use the Shannon Weiner index to measure diversity as a correlation between competition. They indicated that when Festuca is grown next to each other in chambers, they grow normal regardless of carbon’s presence. However when grown in contact with Centaurea, their growth is interfered with.

They showed how active carbon affects both plants. Centaurea grown with Festca with carbon present showed Centaurea doesn’t grow well because the allelopathy and low chemical influence doesn’t help its growth. So in essence, Festuca grows regular. This shows the competitive shift because Festuca can compete better without a disadvantage. Centaurea was the better competitor according to this experiment, but all the measures were not taken. Water’s influence on the soil wasn’t taken into consideration and could have played a role in the results and how the Festuca roots grew.

Another aspect that could have affected the results was how and what “active” means in terms of plant growth. She defines active as growth; however, there could be other means to measure activity instead of growth. Also, there could have been other bacteria and fungi around the sampling cite that wasn’t taken into consideration. Even though these small experimental errors could have played a role, the overall idea was still displayed that the overall effect of one plant is the results of multiple interacting mechanism. .


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