4、Drought decreases growth, producing a narrower ring.
5、Species of tree do differ in their response to weather changes. One might respond strongly to changes in overall rainfall, another might be more sensitive to the amount of rain during the late summer, and another to a temperature change that alters the length of the growing season.
6、Crowding from neighboring trees. This causes a series of narrow rings. Crowding is suspected when the series of narrow rings is more than three, because droughts are usually only one to three years.
7、If the rings are narrow on one side of a tree with wide rings on the other, the tree was crowded on the side of the tree where the rings are narrow.
8、A series of many narrow rings followed immediately by wide rings probably means that an encroaching neighbor died, releasing the crowded tree into a growth spurt.
9、Fire scars suggest past forest fires. The number of annual rings between fire scars shows the period between fires.
10、Scars due to insect plagues indicate insect infestations.
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