1 Density and Stocking

2 Potential of the land to produce wood is determined mainly by its site quality. The actual production or growth of wood fiber achieved on a given site is determined by the number, distribution and species of trees on the site. Two measures of the number and distribution of trees on a given site are "density" and "stocking". Density is a measurable "fact". Stocking is a "relative" assessment.

3 Measures of Stand Density 1.Number of trees per acre 2.Basal area per acre 3.Stand Density Index 4.Crown Competition Factor

4

5

6

7

8

9 BA/ac =  /

10

11 Stand Density Index Based on the observed maximum size- density relationship, using 1) number of trees per acre (TPA) and 2) mean quadratic tree diameter (D q ), a.k.a. diameter for tree of mean basal area Incorporates both number and basal area per acre measurements

12 Stand Density Index

13 Stand Density Index Slope ~ - 3 / 2

14 Stand Density Index Equates observed D q and TPA to an equivalent TPA for the indexed D q =10 in.

15 Crown Competition Factor Reflects the area available to the average tree relative to the maximum area it uses if it were open-grown

16 Crown Competition Factor CCF < 100

17 Crown Competition Factor CCF > 150

18 Stocking Involves the comparison of a given stand to a "normal", or fully-stocked stand. –Problem: "Has anyone ever seen a normal stand?" Assumes that "natural" mortality is solely a result of over- stocking. Concept of stocking is very subjective in nature. Stocking guides are the main method for assessing stocking.

19 Stocking 1) Stocking Guides 2) Stand Density Management Diagrams

20 1. Stocking Guides 1.Species Specific 2.Require that you know trees per acre and basal area per acre. 3.Usually have 2 or 3 lines that are important: the A-line, the B-line, and sometimes the C-line. Above the A-line: overstocked Between A-line & B-line: fully stocked Below the B-line: understocked C-line: lower limit of “understocking” to reach the B- line in 10 years on an average stand

21 Generic Stocking Guide

22 Generic Stocking Guide

23 White Pine Stocking Guide

24 2. Stand Density Management Diagrams What are they? Graphic tools which illustrate how DIAMETER, HEIGHT, DENSITY and VOLUME change over time for pure, even-aged stands Why use them? Lead to understanding of stand dynamics To plan/evaluate initial spacing and thinning regimes

25 2. Stand Density Management Diagrams

26 Spacing effects on tree size

27 Relationship between density and tree size

28 Baseline measurement 1st re-measurement 2nd re-measurement 9th re-measurement

29

30

31 Maximum size-density line Mortality initiation line Stands under-stocked Zone of Optimum Density Management Zone of Imminent Competition Mortality Crown closure line Stand trajectories

32