1906 



FORESTRY AND IRRIGATION 



447 



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Permanent Sample Plot. Crown Cover in a Stand that has been Heavily Thinned. 

 As the Trees Develop the Crowns Enlarge and Close the Openings. 



Suppose the question is, "Will west- 

 ern yellow pine in the pole stage grow 

 enough faster after a heavy thinning 

 to pay for the operation?" A piece of 

 forest is found in which the trees are 

 4 to 6 inches in diameter and stand 

 very close. In that a half acre is laid 

 off, preferably in the form of a rect- 



angle, and the boundaries are perma- 

 nently marked. Then the locality is 

 carefully described, and every fact re- 

 corded that can have the least bearing 

 upon the forest altitude, aspect, kind 

 and depth of soil, humus, and ground 

 cover. Next, the forest itself is meas- 

 ured and recorded. Each live tree 



