6.7 Summary Questions

1. Determine if each of the cores shown below represents a suitable site index tree.

Top core sample shows even annual rings. Middle core sample shows a black growth ring halfway to the center. Bottom core sample shows tight growth rings halfway to the center.

 

2. For each tree illustrated, decide if it is a suitable site index tree.

Tree one has a sucker limb on the main trunk. Tree two has a burl on the trunk. Tree 3 has a swollen butt. Tree four has no visible defect. Tree 5 has a fork.

 

3. Using the site index graph for Douglas-fir, determine the average site index of trees A, B and C.

Tree Total Tree Height (ft.) Breast Height Age (yrs.) Site Index
A 60 35
B 118 60
C 115 65
Avg. SI

 

Growth curves. Tables with this information can be found in Section 6.8.

 

Answers to Summary Questions

1.  Top Core: This core sample appears fine.  It shows a gradual transition from large growth rings to smaller growth rings from pith to bark, which is normal.

Middle Core:  This core sample has a black spot, which could indicate rot, pitching in response to insect attack or prior fire.  I would choose another tree for site index.

Bottom Core:  This core sample appears to have several tight rings in the center.  This could indicate previous suppression followed by release.  I would choose another tree.

 

2. Moving from left to right, I would answer as follows:

image

Tree 1:  No, it has a large sucker limb, a weak spot in a tree that often has rot associated with it.

Tree 2:  No, it has a burl or canker on the stem, which indicates malfunctioning of the wood growth.

Tree 3:  No, this has a bell-shaped swelling at the base of the tree, which indicates butt rot.

Tree 4:  Looks fine for site index.

Tree 5:  No, this tree has a fork, a weak spot in the tree that often results from top breakage.

 

3.  Using the site index graph for Douglas-fir, determine the average site index of trees A, B and C.

Tree Total Tree Height (ft.) Breast Height Age (yrs.) Site Index
A 60 35  76
B 118 60 106
C 115 65 98
Total SI 280
Avg. SI ≈93

Graph showing site index values of three trees. Similar values can be obtained from tables in section 6.8.

The site index of each tree is determined, using the graph. To obtain the average, sum up the site index values and divide by three.

 

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Forest Measurements Copyright © 2016 by Joan DeYoung is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.