IB ESS 2.5 Zonation, Succession and Change

Practise distinguishing spatial zonation from temporal succession, using transect and case-study evidence to explain soil development, diversity and resilience after disturbance.

Exam points

distinguish spatial zonation from temporal succession using gradients, transects and primary or secondary examples
explain how colonisation, humus, nutrient cycling and roots increase soil fertility, diversity and resilience
compare gross and net productivity across pioneer and climax stages using respiration and biomass change
classify r- and K-strategists from offspring, maturity, survivorship and colonisation evidence
evaluate how climate, soils, consumers or human activity redirect succession and challenge a single climax state

Covered syllabus points

2.5.1—Zonation definition 2.5.2—Transect use 2.5.3—Succession definition 2.5.4—Seral communities 2.5.5—Primary succession 2.5.6—Secondary succession 2.5.7—Succession changes over time 2.5.8—Ecosystem disturbance tolerance 2.5.9 (HL)—Community development influences 2.5.10 (HL)—Productivity patterns in succession 2.5.11 (HL)—r- and K-strategist species 2.5.12 (HL)—Climax community concept 2.5.13 (HL)—Plagioclimax

[Maximum number: 1]

Figure:Vegetation map of New Zealand

Key:

Figure:Topographic map of New Zealand

With reference to Figures: Topographic map of New Zealand and Vegetation map of New Zealand, identify a relationship between altitude and type of vegetation.

a. Low/lower altitude is associated with bog/swamp/grass steppe/shrub steppe/subtropical laurel forest/subtropical rainforest/temperate broadleaf forest;
b. High/higher altitude is associated with alpine shrubland/highland steppe/temperate rainforest;
c. Mid/middle altitude is associated with temperate rainforest/temperate broadleaf forest;
d. Low/lower altitudes are associated with subtropical forests / mid/middle altitudes with temperate forests / high/higher altitudes are associated with grasslands;
e. The higher the altitude, the more grass steppe there is;
f. Zonation;

Note to examiners: accept any other reasonable responses. Do not accept just "steppe" or "rainforest", it must be specifically named for the appropriate altitude. Do not accept responses which simply state at which height range a specific vegetation type is located (e.g. Temperate broadleaf forest is located at $1000 \mathrm{~m}-1249 \mathrm{~m}$ ) as this is not a relationship.

[Maximum number: 3]

Figure:Beaver-dam succession sequence — panel A

Figure:Beaver-dam succession sequence — panel B

Figure:Beaver-dam succession sequence — panel C

Figure:Beaver-dam succession sequence — panel D

Suggest how an ecologist might measure the changes in one abiotic factor along a transect from a beaver marsh, through beaver meadow to the adjoining forest.

[Maximum number: 9]

Figure:Stages of ecological succession after fire

(a)

Outline two reasons why the species within pioneer communities in the succession model shown above are more likely to be r-strategists than K-strategists.

[ 2 ]

(b)

Outline two reasons why the climax community in the succession model shown above is more stable than the intermediate community.

[ 2 ]

(c)

Distinguish between zonation and succession.

[ 1 ]

(d)

Outline two ways in which the food web is likely to change as a result of succession.

[ 2 ]

(e)

Outline two ways in which the soil quality in the pioneer stages of the succession model shown above will differ from that in the climax ecosystem.

[ 2 ]

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Covered syllabus points

2.5 Zonation, succession and change question 1

2.5 Zonation, succession and change question 2

2.5 Zonation, succession and change question 3

Question (a)

Question (b)

Question (c)

Question (d)

Question (e)