Lab 6: Intraspecific Competition in the Field

Question 1

What can be used to examine the nature of competition?

Answer 1

carefully controlled field experiments (species exclusions and additions, and/or removals or thinnings)

Question 2

What may develop when organisms are in intense competition?

Answer 2

size and reproductive inequalities (heiarchies) may develop

Question 3

Why can size and repro inequalities result from intense competition?

Answer 3

at high densities, “winners” can supress “losers”, thus increasing the degree of inequality within the population

Question 4

What is one method of estimating inequality within a population experiencing intraspecific competition?

Answer 4

Gini coefficient

Question 5

What is the Gini coefficient based upon?

Answer 5

the Lorenz curve

Question 6

What does the Lorenz curve graph?

Answer 6

the rank of individuals within a population vs the cumulative percent of some size, growth, or reproductive parameter

Question 7

What is the gini coefficient?

Answer 7

the area between the Lorenz curve and a line showing perfect equality (slope of 1.0)

Question 8

The greater the inequality,

Answer 8

the deeper the Lorenz curve and thus the Gini coefficient goes up as population inequality increases

Question 9

What was the dependent variable?

Answer 9

diameter growth

Question 10

What trees were sampled?

Answer 10

trees were sampled at the edge of the stand and on the inside of the stand

Question 11

What is competition like at the edge of the stand?

Answer 11

lower competition since all exposed to sunlight and root resources from one side

Question 12

What is competition like on inside of the stand?

Answer 12

higher competition since trees may overlap and shade others and compete for root resources

Question 13

Where should Gini coefficient be higher if interference competition was important?

Answer 13

higher in the interior than edge

Question 14

If resource competition was more important, what should the gini coefficient be?

Answer 14

smaller in the interior

Question 15

What should tree size and mortality rate be like for interior?

Answer 15

tree size smaller and mortality rate higher

Question 16

If the planting density was ideal, what should intraspecific competition be like?

Answer 16

should be minimized and no different between the trees on the edge and interior should be found

Question 17

What did the 2022 results show?

Answer 17

• the edge had higher Gini indicies than the interior trees, suggesting that root resource comp on the interior
• edges were larger and had lower mortality
• trees primarily competing for root resources rather than light

Question 18

What did the 2023 results show?

Answer 18

• a much lower Gini index than either of the 2022 sites
• trees at stretch road not competing strongly

Question 19

What would complete equality show as in gini index?

Answer 19

0

Question 20

What does the 2024 data show?

Answer 20

• recent growth is starting to show development of hierarchies
• gini index is much higher for recent growth rate in comparison with overall growth rate across all years