Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Sentence1: a wildfire changes an ecosystem drastically. 
Sentence2: Forest fires change an ecosystem drastically.
changes

Sentence1: Trees have woody stems covered with bark. 
Sentence2: Evergreens have woody stems covered with bark.
bark

Sentence1: Food for the plant is made in the leaves. 
Sentence2: A plant requires leaves for survival.

leaves