1. and Other Related Measurements
Site and Stocking
and Other Related Measurements

2. Height as a Measure of Site Quality
Tree Height in relation to tree age has been found to be the most practical, consistent and useful indicator.
What was discussed earlier as the limiting factor to fast growth?

3. Site Index
The average total height and age of dominant and co-dominant trees in well-stocked, even-aged stands at a given age.
Typically the base age for hardwoods is 50. Some softwoods use 25 years for the reference age.
For example, if the SI50 for a tree is 75, we are saying that the average height of dominant trees at age 50 for this stand is 75 feet.

4. Crown Class
Dominants - Crowns receive full light from above, and partly from the side. Trees extend above the general crown levels
Co-dominants - Crowns form at the general level of the canopy. Crowns receive full light from above, but little from the sides.
Intermediates - Crowns generally below the dominants and co-dominants, but extending up into the general canopy level. They receive little or no direct light from above, nor the sides.
Overtopped or Suppressed - Crowns entirely below the general level of the canopy. They receive no direct light from above, nor the sides.

5. Crown Class

6. Crown Closure
Measured by what?

7. Crown Closure Spherical Densiometer Hemispherical photography
Aerial photography
CLASSES
Very Sparse 1-9%
Sparse 10-29%
Low 30-49%
Medium 50-69%
Dense 70-84%
Very Dense %

8. Tree Age
Even-aged - The range of tree ages generally does not exceed 20% of the rotation age assumed.
Uneven-aged - Three or more distinct age classes, either intimately mixed, or in clumps.

9. Increment Borer

10. Site Index
Total Heights and Ages of dominant and/or co-dominant trees are measured and curves are fitted. Varies by species and region.

11. Site Index Limitations
Exact Stand age is often difficult to determine (diffuse porous wood, false rings and drought rings, skill with borer), and small errors can cause relatively large changes in the site-index estimate.
Alternate methods of determining stand age can include counting branch whorls (if applicable species) or historical information

12. Site Index Limitations - continued
Not well suited to uneven-aged stands, areas of mixed-species composition, or open lands.
Stand volume variables (DBH, stem form) are not taken into account.
Site-Index is not a constant, it changes periodically with climate and management.
Varies by species within the same site. So if you plan to change the site to a new species, it is difficult to predict.

13. Factors that Influence SI

14. SI Alternatives Growth index Output from a mechanistic growth model
Tree diameter
Stand volume
Output from a mechanistic growth model
Indicator plants
NPP, evapotranspiration
Leaf area index
Can be assessed remotely

15. Site Index real world use
Growth Intercept Models: These species-specific models are designed explicitly for young stands (5-50 years breast height age). The growth intercept technique estimates site index from the average annual height growth of site trees, which is determined either from the distance between annual branch whorls or from the height and breast height age of the tree.
Site Index-Biogeoclimatic Ecosystem Classification (SIBEC) Models: This comprehensive tool correlates site index with site series within biogeoclimatic ecosystem classification (BEC) units and site series. The BEC system is designed specifically for British Columbia’s ecosystems. This model is best used for very young stands, very old stands, and stands not suitable for other methods. 

16. Indicator Plant Approach
Curves fitted to measured data relating the presence of certain plants to the site quality for trees on a given site.

17. Site Index from Soil

18. Soil Survey Forest lands
Site Index -  Measurements of site index are usually extended to a number of like soils where data are unavailable.
Erosion hazard
Equipment limitations
Seedling mortality
Windthrow hazard
Plant competition
Trees to plant

19. Site Productivity Measures

20. Principles and their implications
Tree Growth
Principles and their implications

21. General Growth Curve

22. Change in Tree Weight

23. Mean Annual Increment Increase in cubic-foot volume per acre per year
Curves fit to known data – usually takes the equation form below
MAI = Constant X Site Index +/- Intercept
Attempts to predict future Annual volume growth

24. Annual Growth Increment
Generalized Chart for conifers

25. The concept of forest site productivity in terms of current annual volume increment vs age.
The concept of forest site productivity in terms of current annual volume increment vs age. The full site potential for wood production (horizontal line) is only briefly realized by a given forest stand (bold line). Management practices may increase or decrease stand productivity (dashed lines) at any stage of stand development and these changes may be permanent or transient. For simplicity, the site potential is considered constant.
Skovsgaard J P , and Vanclay J K Forestry 2007;81:13-31
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26. Stocking
And Stand Density

27. Stand Density
Quantitative measurement of the stand describing the degree of stem crowding within a stocked area. As in: 150 stems/acre
Stocking refers to the adequacy of a given stand density to meet some management objective. Often expressed on a basal-area basis comparing current condition to ideal.

28. Growth vs. Growing stock

29. The thinning response hypothesis.
The thinning response hypothesis. For many tree species, stand volume growth is thought to be independent of thinning practice for a range of thinning grades stretching from the unthinned stand, down to a residual basal area of ∼50 per cent of maximum basal area. The accumulation of maximum basal area occurs in unthinned stands only.
Skovsgaard J P , and Vanclay J K Forestry 2007;81:13-31
© Institute of Chartered Foresters, All rights reserved. For Permissions, please

30. Assmanns theory of natural, optimal and critical basal area.
Assmanns theory of natural, optimal and critical basal area. For given site conditions and a given spacing or initial stem number at stand establishment, the unthinned stand or control plot will support the highest possible basal area of live trees at any stage of stand development. This is referred to as the natural basal area (NBA). The basal area at which the largest stand volume growth is achieved during the period concerned is referred to as the optimum basal area (OBA). The basal area at which volume growth is 5 per cent less than at the optimum is referred to as the critical basal area (CBA). In this example, optimum basal area is located at 83 per cent of the natural basal area. Here, volume growth is at 102 per cent. A 5 per cent reduction in volume growth, compared with that at the optimum, appears at a basal area of 60 per cent. Here, volume growth is at 96.9 per cent, compared with the unthinned stand.
Skovsgaard J P , and Vanclay J K Forestry 2007;81:13-31
© Institute of Chartered Foresters, All rights reserved. For Permissions, please

31. Stocking
A description of the number of trees, basal area, or volume per acre in a forest stand compared with a desired level for a management objective
Central Hardwood Stocking Chart 

32. Stocking Charts Vary by species Vary by site quality
Compare current stand conditions to desired in order to make prescriptions