1. The Science of Plant Ecology

2. Warning!
Lab lectures will be included on Lecture Exam #1!

3. Research Secondary research: Gathering data about facts already known
Primary research: Generates new knowledge

4. Scientific Method
Fig.
1.1

5. Scientific Method
Hypothesis: Possible explanation. Must be “testable” by experiment
Experiment: Test of idea by observation or collection of data

6. Experiments
Manipulative experiment: Compare treated condition (manipulated) against “control”
Control: Keeps other conditions same
Fig. 1.2
Konza Prairie (KS)

7. Experiments
Natural experiment: “Manipulative” experiment occurring due to natural process
1980 eruption
Mt. Saint Helens, OR

8. Experiments
Observational experiment: Study variation occurring under differing natural conditions
Fig
Tree species richness (# species)
across N. America
(in standard area plots)
AU!

9. Theory
Theory: Broad, comprehensive explanation of large body of information. Essentially equivalent to “scientific fact”
Examples: Theory of gravity, Theory of relativity, Theory of evolution, Atomic theory

10. Plant Sampling Techniques

11. Sampling: Why?
Best way to find answer is to take 100% sample (count/measure everything)
Usually not practical
Ex, describe vegetation of Lee County AL

12. Accuracy vs. Precision Accuracy: how close to “true value” samples are
Precision: similarity measurements to each other

13. Accuracy vs. Precision Accuracy: not known unless 100% sample taken
Precision: standard error of mean (S)
Standard deviation

14. Sampling Choosing technique depends on:
1) Desire for accuracy/precision
2) Objective of study
3) Time/money
4) Tradition!
Solution: Be reasonable! (compromise often needed)

15. Importance
Often we want to know how “important” plant species are in area
3 measures of importance of a species (sp. A)
Density of A = No. inds. per unit area (reflects abundance of A)
Frequency of A = No. of times sp. A found in samples divided by total number of samples taken (reflects pattern of A)
Cover of A = Percent of area occupied by A in sampled area (reflects biomass of A)

16. Focus on Cover Many ways to get cover (biomass) data:
1) harvest & measure biomass
2) visual estimation
Note how canopy edges “filled in” by observer

17. Focus on Cover Many ways to get cover (biomass) data:
1) harvest and measure biomass
2) visual estimation
3) point frame

18. Focus on Cover Many ways to get cover (biomass) data:
1) harvest and measure biomass
2) visual estimation
3) point frame
4) moosehorn crown closure estimator

19. Focus on Cover Many ways to get cover (biomass) data:
5) Trees: basal area (area tree trunk per unit area). Bitterlich method.

20. Focus on Cover Many ways to get cover (biomass) data:
6) Trees: DBH (diameter at breast height: 4.5 feet or 1.3 m)

21. Other Challenges Clonal plants: density (how determine individual?)
Canopy overlap: where boundaries?
Border calls: in or out?
Solution: Be reasonable!

22. Importance
Often we want to know how “important” plant species are in area
3 measures of importance of a species (sp. A)
Density of A=No. inds. per unit area (reflects abundance of A)
Frequency of A=No. of times sp. A found in samples divided by total number of samples taken (reflects pattern of A)
Cover of A=Percent of area occupied by A in sampled area (reflects biomass of A)

23. Importance Calculate Importance Value (IV)
Sum of Relative Density, Relative Frequency, and Relative Cover
IV= Rel. density + Rel. frequency + Rel. cover
<300%= < 100% + < 100% + < 100%

24. Sample Techniques 1) Quadrat methods
2 dimensional sample unit used: quadrat
Quadrant?

25. Quadrat Method a) Shape?
Oblong better: picks up more variation per sample
But: less perimeter means less in/out decisions (source error)
Compromise: be reasonable!

26. Quadrat Method
b) Size?
VITAL for determining plant pattern (and important for density measurement as well)
Can use species-area curve

27. Quadrat Method c) Number? Suggestions include: A) Sample 1-20% of area
B) Include 95% of species
C) Use Running Mean Graph (Quadrat Sampling Lab #4)

28. Belt Transect Method Also 2 dimensional method Useful dense vegetation
Useful sampling along sharp environmental gradient 2m 2m
Environmental gradient 2m 2m
4 species: A = red, B = turquoise, etc.

29. Belt Transect Method
Example diagram and calculation of Importance Value of species A 2m 2m
Environmental gradient 2m 2m
4 species: A = red, B = turquoise, etc.

30. Belt Transect Method Density of A = 10/40m2 = 0.25/m2
Frequency of A = 9/10 = 0.9
% Frequency of A = 0.9 X 100% = 90% 2m 2m
4 species: A =red, B= turquoise, etc.

31. Belt Transect Method
Cover of A: Assume we visually estimate covers of each species in each unit of transect
Assume values for A are:
10%, 15%, 15%, 10%, 0%, 10%, 5%, 5%, 10%, 10%
Mean cover of A= Sum of covers/10 = 9% 2m 2m
4 species: A = red, B = turquoise, etc.

32. Belt Transect Method
Do density, frequency, cover calculations for all other species (B, C, D)
IV= Rel. density + Rel. frequency + Rel. cover
For sp. A:
Rel. density = density of A/density of all species X 100%
Rel. frequency = frequency of A/frequency of all species X 100%
Rel. cover = cover of A/cover of all species X 100%
Can then calculate IV for other species (B, C, D)

33. Belt Transect Method
You will do IV calculations for species in lab #1 (plotless sampling) and lab #4 (quadrat sampling)
Quadrat lab
Plotless lab

34. Line Intercept Method 1 dimensional method (line has no width)
Useful for dense vegetation: scrub
Scrub in Australia

35. Line Intercept Method
Cover: record distances along line covered by canopies of species
Cover frequency: Divide line into units. Determine frequency of species in those units
Density?

36. Sampling Techniques THE SEQUEL

37. Plotless (distance) methods
Based on points
Points have no dimensions: 0 dimensional method
Often used with trees: sampling along transect through forest

38. Plotless (distance) methods
Information Collected:
1) tree identity
2) tree size (reflects biomass or cover)
3) distance measurement (from something to something)

39. Plotless (distance) methods
Method 1: Nearest individual method

40. Plotless (distance) methods
Method 2: Nearest neighbor method

41. Plotless (distance) methods
Method 3: Random pairs method
A) find nearest tree
B) draw line from pt to tree
C) make exclusion zone
D) measure distance to nearest tree outside zone

42. Plotless (distance) methods
Method 4: Point centered quarter method

43. Plotless (distance) methods
Information Collected:
1) tree identity
2) tree size (reflects biomass or cover)
3) distance measurement (from something to something)
IV= Rel. density + Rel. frequency + Rel. cover
<300%= <100% + < 100% + < 100%
How get rel. density, rel. frequency, rel. cover values?

44. Plotless (distance) methods
Cover: have DBH values
Convert DBH to area trunk for each species
% relative cover of species Y:
Cover of Y/Cover of all species X 100%

45. Plotless (distance) methods
Frequency: Have tree identities for each point
% frequency of species Y:
No. pts. with species Y/Total number pts. X 100%
% rel. freq. of sp. Y:
Freq. of Y/Freq. all species X 100%
IV= Rel. density + Rel. frequency + Rel. cover

46. Plotless (distance) methods
Density: ?? No areas were measured??
Geometric principle: as density increases distances measured decrease
Note importance of random placement of points!

47. Plotless (distance) methods
Steps:
1) Calculate mean distance (D) for all trees sampled
2) Use magic formula:
Density (all species) = A/(correction factor)(D)2
To express results in metric units:
A=10,000 m2/hectare (ha)
D should be in meters (m)
Correction factor?

48. Plotless (distance) methods
Steps:
Correction factor?
2 for nearest individual method
1.67 for nearest neighbor method
0.8 for random pairs method
1 for point centered quarter method
3) Calculate density of species Y:
No. Y/No. all species X Density all species
4) % rel. density of Y:
Density of Y/Density all species X 100%

49. Plotless (distance) methods
Can now calculate IV of species Y
IV= Rel. density + Rel. frequency + Rel. cover
<300%= <100% + < 100% + < 100%
Repeat calculations for all other species

50. Plotless (distance) methods
Note on Point Centered Quarter method
1) More data per point
2) Relatively simple
3) No correction factor in density formula (correction factor = 1)

51. How place sample units? Generally, random best How define?
All potential sample units have equal chance of inclusion
Why best?
Eliminates bias by sampler
May be required for statistics or equations (e.g., density formula for plotless methods)

52. How place sample units? Random not same as:
Arbitrary: Choosing while attempting to eliminate conscious bias
Systematic: Choosing using numeric pattern (ex, every 5th tree along transect)
Deliberate: Choosing with criteria (ex, all trees > 30 cm dbh)

53. How place sample units?
But, random may not always give representative sample
Example: X X X X X X X X X X X

54. How place sample units? Techniques: Random vs.
Stratified random (subdivide area & sample randomly in each division)

55. How place sample units?
Techniques:
Systematic

56. How place sample units? Techniques:
Random-Systematic (select start randomly, place points on transect systematically: or vice versa)
systematic
random
systematic
random OR