The study looked at how different types of rocks in a hilly area in Iran affect the amount of carbon and nitrogen in the soil. They found that soil on hills made of loess had more carbon and nitrogen than soil on hills made of marl. This is because plants can grow better in loess soil. The researchers also found that overgrazing on steep slopes made of marl can cause carbon to be lost into the air. Overall, the type of rock in an area can affect how much carbon and nitrogen is stored in the soil, and it's important to protect the soil to keep these nutrients in place.