Plant Community Ecology-Plant Interactions (competition/facilitation). Competition. Reduction in fitness (how an organism apportions resources among competing demographic functions (survival, growth, reproduction) due to shared use of a resource that is in limited supply Intraspecific
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Plants can tell the difference between the shade of an inanimate object and the shade of another plant. When a plant detects competition from neighboring plants, it initiates a set of responses, called collectively the shade avoidance syndrome, that alter its growth and physiology. A rapid and transient increase of newly synthesized auxin via a newly discovered auxin synthesis pathway allows plants to elongate and grow toward the sun.
DEBATE between Grime and Tilman (1980s) regarding the effects of competition on species coexistence and community composition
Resource competition-tendency of neighboring plants to utilize the same quantum of light, ion of a mineral nutrient, molecule of water, or volume of space
Both believe that understanding plant traits, resource acquisition and loss by plants and the effect of disturbance on individuals holds the key to understanding patterns of diversity
GRIME CRS Theory regarding the effects of competition on species coexistence and community composition
TILMAN R* (Resource-Ratio ) Theory regarding the effects of competition on species coexistence and community composition
Change in resource levels over time occurs because of incorporation of resources into the biomass of the plant population. (1) The population starts at a high resource level. Growth by the population results in the uptake of resources which are incorporated into standing biomass. This in turn results in the (2) decrease of available resources in the environment. This process continues until there is a (3) dynamic balance between resource uptake due to growth and resource release due to mortality. Essentially b=d and the population size remains fairly constant and resource levels are held at the level of R*, the minimum resource level for the maintenance of the population.
If two species are competing for the same resource, the species that can grow at the lowest resource levels will be able to drive the other species out of the system. Species B above will outcompete species A, since it can exist at lower resource levels
Craine 2005 Journal of Ecology-critiqued Grime and Tilman’s theories
General Overview of effects of competition on species coexistence and community composition
Plants influence their environments in many ways—altering balance of nutrients, acidifying the rhizosphere, secreting materials, and shedding parts. Plant can also affect soil microbes that affect other plants (indirect)
Allelopathy? balance of nutrients, acidifying the rhizosphere, secreting materials, and shedding parts. Plant can also affect soil microbes that affect other plants (indirect)
Eucalyptus benefitted at high P to be near Falcataria but had negative competition interactions with Eucalyptus at low P