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Site quality
from PNGAF MAG ISSUE # 9 B-5B4D3 Dr John Davidson Accompaniment "RAINBOW EUCALYPT MAN" Part 6 of 8 parts
by rbmccarthy
It is clear the form factors rise with increasing spacing among trees in stands of this age (3 years). The rate of rise is greater at closer spacings where lateral competition is more intense. At wider spacings where competition among trees is less the rate of rise is slower.
VOLUME REGRESSIONS AND FORM FACTORS FOR TREES OF E. DEGLUPTA PLANTED AT FIVE INITIAL SPACINGS AT SEVERAL SITES+ IN PAPUA NEW GUINEA
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Initial Spacing (mxm) Volume Regression# Form Factor (X10-5)* No. of Trees Sampled Multiple Correlation Coefficient
2 x 2 2.5 x 2.5 3 x 3 4 x 4 V=3.596X10-5D2H 3.596 (0.46) V=3.715X10-5D2H 3.715 (0.47) V=3.731X10-5D2H 3.731 (0.49) V=3.770X10-5D2H 3.770 (0.49) 46 32 22 48 0.995 0.997 0.996 0.994
5 x 5 V=3.816X10-5D2H 3.816 (0.48) 50
0.990 + Sites were all on well drained terraces which formerly supported natural stands of E. deglupta but data for close comparison of sites were lacking. # V = total volume in cubic metres, D = diameter at breast height in centimetres, H = total height in metres. * The figures in brackets exclude a constant value of 0.785 x 10-4 derived from the term π/4 and the conversion of square centimetres to square metres for D2 .
Site quality
E. deglupta is very responsive to differences in site quality. Four site quality classes were distinguished on the basis of mean stand height at age ten years. Sampled trees were assessed in three overlapping site quality categories (classes 1-2, 2-3 and 3-4). Site quality 1 included the best sites available for E. deglupta, while site quality 4 produced very poor growth.
17
The volume regressions for each of the three categories are given in the table on the following page. From the limited data available there appeared to be only a slightly reduced form factor on the poorer site class. That is the trees are slightly slimmer on the poorer site quality.
17 For example, see Davidson J 1973 Decayed wood in living trees of Eucalyptus deglupta Blume. Proceedings of IUFRO-5 Meeting, South Africa, pp 208-224, and table of yields on different quality sites presented earlier.
