Unexplained Relationships of Height-Diameter of Three Tree Species in a Tropical Forest.

Associations between bivariate variables relative to the unexplained relationships of height-Dbh (diameter
at breast height) models were investigated. Seven permanent sample plots measuring 40m by 250m at
Omo Forest Reserve were used to assess the relationships between height and diameter at breast height of
three tree species as affected by the variables of neighbouring trees. The result showed differences in the
coefficient of determination of the bivariate models and multivariate models. The models arrived at for
each of the species and for the bivariate models are:
Scottelia coriaceae: Ht = 2.59 + 0.473D+ 0.0012D2 for 5cm ≤ D ≤100cm (R2 = 0.70)
Sterculia rhinopetala: Ht = 5.96 + 0.467D+ 0.00296D2 for 5cm ≤ D ≤100cm (R2 = 0.77)
Strombosia pustulata: Ht = 2.02 + 0.722D+ 0.00581D2 for 5cm ≤ D ≤ 60cm (R2 = 0.81)
Where both Ht and D are height and Diameter at breast height.
While on the other hand the multivariate models that considered the effect of neighbouring trees are:
Scottelia coriaceae: 2
1 2 3 4 Ht = 3.74 + 0.41x −1.14x + 0.205x +1.278x (R = 0.723)
Sterculia rhnopetala: 2
1 2 3 4 Ht = 6.18 + 0.2601x +1.163x + 0.438x − 0.442x (R = 0.608)
Strombosia pustalata: 2
1 2 3 4 Ht = 6.84 + 0.399x − 0.318x − 0.138x − 0.838x (R = 0.650)
x1 = diameter at breast height, x2 = Mean neighbouring tree distance, x3 = Frequency of the neighbouring
tree and x4 = Position of the crown.