Consider this northern site of primary succession following the retreat of a glacier. as we move from left to right, describe some improvements in the abiotic factors that support plant growth.

a) change in climate over time
b) less competition for water resources due to biodiversity
c) improved soil quality: increased humus and water retention
d) increased population density resulting in decreased pathogens

C. improved soil quality: increased humus and water retention.

Explanation:

An ecological succession brings change in the type of living species residing in an ecosystem with respect to changes that occur in the abiotic (non-living factors) with respect to time.

A region affected by a retreating glacier will not be suitable for the growth of living species. The soil may be lacking minerals and will be in the permafrost condition. So for the initiation of succession the improvement in soil an important abiotic factor is required. The improved soil quality will allow the accumulation of organic and inorganic minerals by physical and biological processes. This will help in formation of humus and water retention.

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.