Lab 5: Basic Techniques for Quatitative assessment of vegetation abundance or importance

Question 1

Most of the methods for quantitative description of vegetation as distinct from flora has been based on one or more of the following prarameters:

Answer 1

1. ) Cover
2. ) Frequency of Occurrence
3. ) Density or numbers of individuals per unit area
4. ) Biomass or weight per unit area

Question 2

Flora:

Answer 2

Is a list of plant species that occur in a given area where the order of species is related to ease of use. Often the flora for a given area will be arranged in alphabetical order by scientific name. Usually in a design for use.

Question 3

What information does flora not provide?

Answer 3

Gives no indication of the importance or abundance of the species present.

Question 4

Vegetation:

Answer 4

Is a list of plant species that occur in a given area where the order of species is related to importance or abundance of each species present.

Question 5

What does it say about a species if it is listed first in a vegetation list?

Answer 5

Is the species that has been assessed to be most abundant or important to the area.

Question 6

The value for each species can be expressed in one of two ways:

Answer 6

1. ) As an absolute value such as density (#of individuals of a species per unit area)
2. ) Or a relative value, usually in percent, such as relative density (density of species X/total density for all specieis present)

Question 7

Selection of a measure of abundace is subjective and is based on….

Answer 7

The goals of the research project or use composite values arrived at summing multiple measures.

Question 8

What is the most common techique for measuring plant abundance?

Answer 8

Transects: Setting up a series of straight lines, either parallel or perpendicular to one another in the study area. Sample reference fames of known area are then placed along the transects and data is gathered within the frame.

Question 9

What are the sample reference frames called?

Answer 9

Quadrats.

Question 10

Areal Cover and how is it measured:

Answer 10

The vertical projection of the above-ground parts of each plant onto the ground. In some circumstances it is the leaf projetion that is measured and in other the area at the base of the plant.
Measure the amount of ground covered by individual species and by the whole vegetation.

Question 11

Why does many ecologists emphasize that cover is of greater ecological significance than density?

Answer 11

Because cover gives a better measure of plant biomass than does the number of individuals.

Question 12

Leaf Area Index (LAI)-

Answer 12

the ratio between the total leaf area above the soil surface and the soil surface area.

Question 13

Cover is important and related to-

Answer 13

• Leaf Area Index (LAI)
  and
• Photosynthetically Active Radiation (PAR)

Question 14

In a forest community what plants get the most PAR?

Answer 14

The trees have access to all available PAR while the shrubs received only the PAR that has not been absorbed or reflected by the canopy leaves.

Question 15

Frequency:

Answer 15

relates to the number of times a specieis occurs in a given number of repeatedly placed small sample plots.

Question 16

Sample plots can be placed in one of two ways:

Answer 16

• Systematically (following a regular pattern)
  or
• randomly

Question 17

Is frequency an absolute measurement?

Answer 17

No, it provides an objective assessment but it is a non-absolute measure. Results, therefore have meaning only in relation to a particular frame size and shape selected for a determination. Decrease the qudrat size increase error of frequency

Question 18

2 types of freqeuncy are used:

Answer 18

1. ) Shoot Frequency: obtained by recording as present all foliage overlapping into a quadrat.
2. ) Rooted Frequency: which records a specieis being present only when it is actually rooted in the quadrat.

Question 19

Density:

Answer 19

refers to the number of individuals per unit area usually obtained by a simple count of plants in a series of random quadrats.

Question 20

What are some difficulty with density counting?

Answer 20

1. ) recognizing individual species apart from one another
2. ) rhizomatous and stoloniferous forms can hardly be counted accuratly.
3. ) The marginal effect of the qudrat. If a species lies half in and half out of the boundary whether we count it or not.

Question 21

Biomass:

Answer 21

refers to the total dry weight of biological material per unit area and is usually obtained by harvesting plants in a series of random quadrats.

Question 22

Examining additions to and losses from biomass can be used to measure….

Answer 22

energy flow rates in an ecosystem.

Question 23

What system of rapid cover count did we used?

Answer 23

Braun-Blanquet scale of cover abundance.

Question 24

Average % Cover =

Answer 24

E mid-points of Braun- Blanquet Classes (or total column)/ Number of quadrays in sample X 100

Question 25

Braun Blaquett class covers and mid points

Answer 25

5- covers >75% midpoint= 87%
4- Covers 50-75% Mindpoint = 62%
3- Covers 25-50% Mindpoint = 37%
2- Covers 5-25% midpoint= 15%
1- Covers

Question 26

Line intersect method:

Answer 26

Measure the physical intersection of a species with a line (transect effectively become a long skinny quadrat)

Question 27

Point intercept method

Answer 27

Drop a series of pins and record the # of pins in contact with each species.

Question 28

What does line and point method give you and what does it not give you?

Answer 28

Gives you cover or frequency data but not density. Not absolute value only relative!

Question 29

Why is basswood tightly clumped?

Answer 29

Adaptation to survive fire. Root crowning survives sens up shoots that develop into trees and therefore get clumps. This is an adaptation to deal with disturbances.

Question 30

Why are hemlocks in straight lines?

Answer 30

Germinate on fallen logs (nurse logs)

Question 31

Average density=

Answer 31

Total column / number of qudrats

Question 32

What effect would using larger quadrat have on density values for species?

Answer 32

Increased quadrat size and you increase the #of individuals of a species proportionally AND THEREFORE THE RATIO OF INDIVIDUALS TO AREA remains constant.