What is the name for the type of graph shown in the image below?

i think it's a cumulative graph but i could be wrong (sry if i am).

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.