Describe the change in biomass over the 100 year period.

Outline the evidence from the graph that the area had plentiful rainfall.

Explain the changes in biomass.

Explain why biomass continues to increase after the respiration levels plateau.

Increases

At a greater rate early on

Seems to plateau/levels off

Forest developed

Increase in biomass «over years» requires rainfall

Water is a limiting factor to photosynthesis

Initially there is low competition for sunlight/resources

Photosynthesis allows accumulation of biomass

Biomass rises as larger plants replace smaller plants

«In later stages» biomass increase limited due to competition for resources
OR
biomass stabilizes as climax community reached

Development of mature trees requires xylem/wood

Xylem/wood contributes to biomass but not respiration

Photosynthesis/production greater than respiration

Photosynthesis/production continues to accumulate biomass
OR
accumulated biomass remains/increases

Many candidates received the full 2 marks for seeing both the increase in biomass as well as the change in rate of increase as well.

Many candidates were able to score one mark for indicating that the increasing biomass was evidence for plentiful rainfall but seldom was a second point made. A few noted that a forest could not develop without rainfall or that water is a limiting factor for photosynthesis. 

A few candidates realized that succession was occurring and the biomass increased as larger plants replaced smaller ones. Carrying capacity was sometimes mentioned when climax community is what they should have been referring to. Others seemed to have no idea as to why biomass was increasing.

Candidates did not seem to understand what was being asked in this question so marks for this were seldom seen.