1348年的黑死病是由森林树木下腐殖质的逐渐丧失引起的。
The Black Death of 1348 was caused by gradual loss of the humus fertility found under forest trees.
原始森林树木种类繁多，是一座真正的宝库，从缅因州向南一直延伸至乔治亚州。
The virgin forest with its richness and variety of trees was a veritable real treasure-house which extended from Maine all the way down to Georgia
农民就有钱维护森林树木，还有他们的巧克力。
Farmers would then get money for preserving forest trees, as well as for their chocolate.
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