Replacing 'y' with 'e' before words beginning with 'i', 'hi','hierba'

Question

When reading a book published in Madrid, I came across something that looked like a possible mistake. The issue is cacophony, replacing a preposition so when spoken the sounds are better formed.

The sentence read “El bosque estaba formada predominantemente por pinos y píceas con macizos de algunos arbustos de escasa altura formand manchas aquí y allá, y hierba espesa…”

My previous understanding was the ‘y’ becomes and ‘e’ when it precedes a word that begins with ‘i’ or ‘hi’.

So in the same sentence it should have been written “…formand manchas aquí y allá, e hierba espesa…”

What would be the correct preposition to use when the next work that follows begins with an ‘i’ or ‘hi’?

Answer 1

y to e, o to u

Y does not change before words, such as hierba, that begin with the ia, ie, io or iu sound, regardless of spelling.

Answer 2

"Hie.." actually has the sound of "ye", so the rule for changing "y" to "e" doesn't apply.

Look at Lesson 4.2...