Post on 24-Dec-2015
competition
What a wondrous problem it is, what a play of forces, determining the kind and proportion of each plant in a square yard of turf!!
10.1 Relationships between yield of dry matter (g) and plant density for two pasture plants
At some point, individuals start competing for resources. Greater density of seeds does not = greater total, final, dry weight.
Increasing soil fertility = greater final biomass…but that is also density dependant.
Do you see why??
10.2 Average individual plant weight (g) for Trifolium subterraneum
At some point, individuals start competing for resources.
Variable are density and time.
Do you see why??
10.3 Frequencies of dry weights of individual seedlings of Tagetes patula
Timing is everything!!
10.5 The effect of relative order of emergence on seedling dry weight (mg)
Timing is everything!If you emerge first you have a big advantage.
Asymmetric competition
Role of propagules & regeneration niche
10.7 A transect through a natural population of Myosotis micrantha
Competition, but…for what?
And, how?
Neighborhood concept…
10.8(A) A strangler fig, (B) Pueraria lobata
Direct competition…wrestling!!
10.9 Separate root and shoot competition while keeping total soil volume constant
10.10 Ratio of biomass in intraspecific competition for Panicium maximum and Hyparrhenia hirta
Outcome of competition of often resource dependant.- The “winner” often the species that can persist at the lowest levels of whatever resource is most limiting
Liebig’s Law of the Minimum:plant growth is limited by the essential nutrient in lowest supply…
not by the total nutrient compliment available
F. arundinacea
Day
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Ger
min
atio
n (
%)
0
20
40
60
80
100
ControlKalmia latifoliaRhododendron maximumLonicera maackiiLonicera japonica
Allelopathy vs. other forms of interference
D) C. lanceolata
Day
0 2 4 6 8 10 12 14 16 18 20 22
B) P. pratensis
C) I. wallerana
Day
0 2 4 6 8 10 12 14 16 18 20 22
Ger
min
atio
n (
%)
0
20
40
60
80
100
A) F. arundinacea
Ger
min
atio
n (
%)
0
20
40
60
80
100
LoniceraAsiminaLinderaControl
Allelopathy is a form of chemical interference. Suppression of one plant, by another, via chemical suppression. There is great variation among the kinds of species , and the particular chemical. Allelopathy seems to have been “invented” evolutionarily many times. One important question is whether the compounds’ primary purposes is this suppression of competitors, or….whether it is a useful side benefit of a compound that does a different job.
Allelopathy has a long, and tortuous, history in ecology. Cornelius Muller published a paper in 1964 focused on shrubs. It made the cover of Science. These shrubs became the essential example of allelopathy- this led to significant recognition for Muller. It was a revolution in the field….
This finding was later challenged, and allelopathy remains a controversial topic. At least, for a while- allelopathy lost favor as an explanation of plant dominance.
In 2004 Ray Callaway published a paper drawing attention to the idea that invasive species may use allelopathy as a “novel weapon” during invasion. I will come back to this.
A closing word on facilitation…
competition