There are no published Yield Class tables for common walnut Juglans regia – at least that I am aware of. A search on the European Forest Yield Tables Database reveals that data are only available for black walnut Juglans nigra in Hungary.
I wrote previously about research that I undertook exploring the crown sizes of major hardwood species – Estimating tree crown size. This work provides the next best available data on managing a stand of common walnut, in the form of basal areas for common walnut ref.
The table below shows the stem diameter (dbh), crown diameter (cd), crown/stem ratio (cd/dbh), number of trees per hectare (Nha) and acre (Nac), and Basal Areas (G) in m2 per hectare. These data were collected from trees grown in open conditions, and calculated for stand densities with zero crown overlap.
dbh | cd | cd/dbh | N trees per ha | N trees per acre | Basal Area m2 per ha |
0.10 | 4.47 | 44.70 | 500 | 202 | 3.9 |
0.15 | 5.35 | 35.67 | 349 | 141 | 6.2 |
0.20 | 6.23 | 31.15 | 258 | 104 | 8.1 |
0.25 | 7.11 | 28.44 | 198 | 80 | 9.7 |
0.30 | 7.99 | 26.63 | 157 | 64 | 11.1 |
0.35 | 8.87 | 25.34 | 127 | 51 | 12.2 |
0.40 | 9.75 | 24.38 | 105 | 42 | 13.2 |
0.45 | 10.63 | 23.62 | 88 | 36 | 14.1 |
0.50 | 11.51 | 23.02 | 75 | 30 | 14.8 |
0.55 | 12.39 | 22.53 | 65 | 26 | 15.5 |
0.60 | 13.27 | 22.12 | 57 | 23 | 16.1 |
0.65 | 14.15 | 21.77 | 50 | 20 | 16.6 |
0.70 | 15.03 | 21.47 | 44 | 18 | 17.0 |
A growth rate of 1cm per year in stem diameter can be presumed, permitting this graph and data to be used in estimating suitable basal areas at different stand ages. If real dbh data is available, then the accurate growth rates will provide accurate basal area increase projections for a given site.
Gabriel Hemery
Reference
Hemery, G.E., Savill, P. & Pryor, S.N. (2005). Applications of the crown diameter – stem diameter relationship for different species of broadleaved trees. Forest Ecology and Management 215, 285-294. View abstract
