8 YIELD FROM EUCALYPTUS 



greater and of better quality in case thinnings are intelligently made. 

 The Webb grove near Hayward was the only managed stand of euca- 

 lyptus found in the State. Here the trees were set out in 1873-74 

 and spaced 8 by 8 feet. When ten years of age the grove was thinned 

 by taking out alternate rows of trees, leaving a present stand spaced 

 16 by 16 feet. The grove is now thirty-six years old, averages 168 

 trees per acre, and shows a yield of 5,178.8 cubic feet, or 17,600 board 

 feet per acre. This yield is exceeded by several unmanaged stands. 

 The poor showing made by the Webb grove is probably due to the 

 poor soil and the depth of the water table. 



YIELD. 



The yield from existing groves was obtained by means of sample 

 plots and volume tables by the following methods : 



1. Diameter of the tree. The diameters were measured outside the 

 bark at a point 4J feet above the ground. This is known as the 

 "breast-high diameter," and is the standard used almost universally 

 by foresters. As has already been mentioned, the measurements were 

 made with a diameter tape. 



2. Height of the tree. This refers to the total height of the tree 

 from the ground to the topmost point in the crown. It was obtained 

 by means of an instrument known as the hypsometer-grademeter. 



3. Number of trees per acre. All trees 1^ inches or more in diam- 

 eter were measured. When a tree forks at a point less than 4^ feet 

 above the ground, each fork was measured as a separate tree; when 

 the tree forks at a point higher than 4^ feet above the ground, it was 

 measured as a single individual. Eucalyptus trees, when grown in 

 an open stand, are apt to fork close to the ground. Many trees 

 when injured send out numerous shoots or suckers, some of which 

 develop into merchantable size. It often happens, therefore, that the 

 number of trees per acre when a plantation is five years or more of 

 age is greater than the number originally planted, in spite of the fact 

 that many trees may have been crowded out and killed in the natural 

 struggle for existence. 



4. The volume table. After the diameter and the height of a tree 

 were ascertained, its volume was obtained by means of tables which 

 show the average volume or contents of trees of various sizes. Two 

 of the same species having the same diameter and the same height 

 give practically the same volume wherever grown and whatever system 

 of management is used, provided they are approximately of the same 

 age. 



