Combine the given two facts to write a concluding fact. Note that there should be some parts of the first and second facts that are not mentioned in this conclusion fact. Your combined fact should be the result of a chain between the two facts. Chains form when two facts connect together to produce a concluding fact. An example of a chain is: "pesticides cause pollution" (fact1) + "pollution can harm animals" (fact2) → "pesticides can harm animals" (conclusion fact). Parts of the concluding fact overlap with the first and the second fact. To construct such a  concluding fact, a useful way is to borrow the subject from one fact and the ending conclusions from another fact.

Fact 1: Plants that shed their leaves seasonally each year are called deciduous plants. 
Fact 2: Trees here are largely deciduous, shedding their leaves in the dry season.
Plants shed their leaves in the dry season each year.

Fact 1: Mollusks are a major food source for other organisms, including humans. 
Fact 2: Many organisms are omnivores with variable diets.
Humans have variable diets and some consume mollusks as a major food source.

Fact 1: a valley is formed by a river flowing. 
Fact 2: Canyon formed as a consequence of river erosion.

a valley is formed by erosion.