Describing Stand Structure

1. Describing Stand Structure

2. What is Stand Structure? The horizontal and vertical distribution of components of a forest stand including the height, diameter, crown layers and stems of trees, shrubs, herbaceous understory, snags, and down woody debris. Source: September 1994, Society of American Foresters, Silviculture Working Group, Silviculture Terminology

3. Role of Forest Structure in Silvicultural Silvicultural Operations Canopy Structure

4. Role of Forest Structure in Silvicultural Silvicultural Operations Canopy Structure Forest Microenvironment

5. Role of Forest Structure in Silvicultural Silvicultural Operations Canopy Structure Species-Specific Growth Response Forest Microenvironment

6. Role of Forest Structure in Silvicultural Silvicultural Operations Canopy Structure Species-Specific Growth Response Forest Microenvironment

7. Describing Stand Height • Mean height of (sample) trees in the stand • Weighted-mean height of (sample) trees in the stand • Mean height of a predefined component of the stand • Some stand height descriptors select only the biggest trees to avoid the effects of thinning and tree mortality on stand height estimates • Top height: Mean height of the trees with the largest dbh in a stand (e.g., average height of the 40 largest trees per acre) • Dominant height: Mean height of the dominant (and sometimes some co-dominant) trees in a stand.

8. Describing Stand Density A quantitative, absolute measure of tree occupancy per unit of land area in such terms as numbers of trees, basal area, or volume. Source: September 1994, Society of American Foresters, Silviculture Working Group, Silviculture Terminology

9. Describing Diameter Structure of a Stand • Average diameter at breast height (dbh) is used to describe average tree size in relatively homogeneous stands • Arithmetic mean diameter: • Quadratic mean diameter: • Quadratic mean diameter (QMD) has a stronger correlation to stand volume than does the arithmetic mean. The basal area of a tree with dbh equal to the quadratic mean diameter is equal to the mean basal area of the stand.

10. Describing Diameter Structure of a Stand • Evaluating a stand’s diameter distribution may be more useful in stands with heterogeneous diameter structure

11. Describing Diameter Structure of a Stand • Calculating average diameter by crown class, size class, or product class may also assist with stands with a variable tree size distribution

12. Describing Canopy and Crown Structure • Canopy Stratum (Canopy Layer): A distinct layer of vegetation within a forest community • Crown Class: A class of tree based on crown position relative to the crowns of adjacent trees. • Dominant, co-dominant, intermediate, suppressed

13. Describing Canopy and Crown Structure Tree Live Crown Ratio

14. Describing Canopy and Crown Structure • Live Crown Ratio • Is the best simple indicator of tree vigor and ability to respond to release • Average live crown ratio of a stand is commonly calculated to determine potential vigor of stand with regard to thinning

15. Describing Canopy and Crown Structure • Canopy cover (i.e., crown cover) is the percentage of ground covered by a vertical projection of the outermost perimeter of the crowns in a stand. • Canopy cover is used as a measure of stand density and competition • Canopy cover is highly correlated with understory light availability