L14 Forest fragmentation

Question 1

What is habitat fragmentation?

Answer 1

where a large expanse of habitat is transformed into q number of smaller patches of smaller total area, isolated from each other by a matrix unlike the original

Question 2

What are the three stages to the fragmentation process?

Answer 2

Initial habitat loss
Isolation of blocks of habitat
Increased isolation due to further land use change

Question 3

What factors are considered when clearing habitat?

Answer 3

Geography

Physical accessibility

Question 4

How does non ransom deforestation affect fragmentation?

Answer 4

Some habitats cleared preferentially
Fragments are often a non-random subset of original habitats and microhabitats
Some species are absent or poorly represented in fragments from outset

Question 5

What is the extent of fragmentation seen in the Brazilian amazon?

Answer 5

18000 fragments of 1-100ha, 25% of the forest is now within 1km of an edge

Question 6

What is the extent of fragmentation seen in the Brazilian Atlantic?

Answer 6

230000 fragments of 1-100ha, 91% of the forest is now 1km of an edge

Question 7

What are species area relationships?

Answer 7

Relationship between the area of a habitat, or of part of a habitat, and the number of species found within that area

Question 8

What do islands and mountain tops have in common?

Answer 8

Both demonstrate relationships between area of habitat and number of species that survive in that area

Question 9

What equation characterises the species are relationship curve?

Answer 9

Arrhenius equation

Question 10

What is the theory of island biogeography?

Answer 10

MacArthur and Wilson postulated that the number of species on an island is a dynamic equilibrium between the opposing forces of extinction and colonisation

Question 11

What are the basic tenets of island biogeography theory?

Answer 11

Local extinction rate is a function of island size

Colonization rate is a function of island isolation from the mainland

Question 12

What would you expect for the number of species on bigger islands?

Answer 12

Can have larger population sizes, so lower extinction rate and hence more species

Question 13

What would you expect for the number of species on islands far from the mainland?

Answer 13

Lower rates of colonisation, hence a fewer number of species

Question 14

How can IBT be applied to the biodiversity impacts of fragmentation in tropical forests?

Answer 14

Look at the area and isolation effects - see if there is an impact on species richness from area.

Question 15

What are the species area effects sen in borneo and the neotropics?

Answer 15

number of species increases with forest patch size, as well as a change in composition of species

Question 16

Which species are likely to be lost as a consequence of fragmentation

Answer 16

Rapid loss of species with large area requirements, such as predators, large bodied species and elevational migrants. Also see a loss of forest interior specialists

Question 17

What makes a forest fragment more isolated

Answer 17

Increased distance from contiguous forest

Question 18

What is the habitat Matrix?

Answer 18

The habitat that surrounds forest fragments and connects them to other fragments or contiguous forest, may support populations of some species found in the forest. Fragments are connected for these species

Question 19

What occurs if there is a large disparity between forest and matrix?

Answer 19

Matrix is inhospitable for forest species, and colonisation rate declines, and the amount of useable habitat shrinks

Question 20

What occurs if there is only a small disparity between matrix and forest?

Answer 20

Matrix is hospita ble for some forest species, so colonisation rate increases and useable habitat expands

Question 21

What is extinction debt?

Answer 21

the future extinction of species due to events in the past, occurs because of time delays between the impacts on a species and the species ultimate disappearance from the habitat

Question 22

When is extinction debt seen in fragmentation?

Answer 22

Immediately after fragmentation many species remain, however, many are committed to extinction over time

Question 23

What does extinction debt look like for fragments in the amazon?

Answer 23

100 ha fragments see a loss of half of their species in <15 years

Question 24

How can extinction debt be reduced?

Answer 24

Increasing fragment size

Question 25

Why is it difficult to reduce extinction debt by fragmentation?

Answer 25

To reduce species loss but 10-fold requires a 1000-fold increase in fragment area

Question 26

What is an edge effect?

Answer 26

A disturbance that penetrates into the fragment, changes in population or community structures that occur at the boundary of two or more habitats

Question 27

What are the changes seen in habitats due to abiotic and biotic edge effects?

Answer 27

Myriad changes, such as differences in the microclimate and wind, in vegetation structure, in floristic composition and in animal composition - can cause a reduction in fragment area for many species

Question 28

How do edge effects impact tree composition?

Answer 28

Plots close to an edge have a higher rate of species turnover that plots far from an edge

Question 29

Whatare the different roles species play in an ecosystem?

Answer 29

Predators
Seed dispersers and pollinators
Carbon storage
Forest structure

Question 30

What happens if you remove predators from an environment?

Answer 30

no top down regulation, so unlimited expansion of herbivores means herbivores able to overexploit vegetation,
seed predators and herbivores increase, which causes a reduced number of saplings and seeds

Question 31

What does removing predators in fragments mean for forest composition?

Answer 31

Reduced wood density

Question 32

What does fragmentation tell is about protected area management?

Answer 32

It is important to maintain connectivity

IBT stresses the importance of isolation to colonisation rates

Question 33

What is the value of corridors?

Answer 33

Corridor is a linear habitat remnant, surrounded by modified matrix, that facilitates the movement of wildlife between fragments, number of surviving species increases with corridor width