This is the 13773rd most frequent Russian word.
низких
"Низких" means "low" (genitive or accusative plural form).
Here, 'низких' is used as an adjective modifying the plural noun 'деревьев', describing their height as low.
Дом стоял в окружении низких деревьев.
The house stood surrounded by low trees.
In this sentence, 'низких' is an adjective modifying the plural noun 'моральных принципов', conveying a metaphorical low character.
Мы говорили о людях низких моральных принципов.
We talked about people of low moral principles.
Here, 'низких' describes the plural noun 'показателей', indicating that the metrics for his height were low.