Baby Names Beginning With "I": Meaning: Rational?

Questions

a ---------- of russia is covered by forest?

a quarter of russia is covered by----------?

a sizable ---------- tree, during the typical growing season, gives off 28,000 gallons of moisture?

a sizable oak tree, during the typical growing season, gives off ---------- gallons of moisture?

all ---------- in venice, italy must be painted black, unless they belong to a high official?