Structural Characteristics

A total of 3544 live stems of ≥ 5 cm DBH and 1439 live stems ≥ 10 cm DBH were recorded in the study. The windward site presented the highest stem density in the ≥ 5 cm diameter class, the leeward site presented the highest density in the ≥ 10 cm class, while the windward site presented a vastly higher proportion of standing dead stems in the ≥5 cm and ≥10 cm diameter classes (21.9%, 17.9% respectively), followed by the leeward (3.6%, 4.9%) and ridge (2.0%, 3.9%) forests (Table 3.3.1.1).

The average canopy height was highest at the leeward forest (23.4 m, SD 4.4), followed by the ridge (15.8 m, SD 3.2) and windward (12.9 m, SD 2.7) forests. The total arboreal foliage and basal areas again reflect a large difference between the leeward forest and the relatively similar ridge and windward

forests, the latter two showing much lower and near identical basal areas in both diameter classes (Figure 3.3.2.1). In the ≥5 cm diameter class, basal area was significantly higher at the leeward site (P > 0.001), while stem height, stem incline and crown diameter were significantly different at all sites (P > 0.001). In the ≥10 cm class, basal area, stem height, stem incline and crown diameter were all significantly different at all sites (P > 0.001).

Figure 3.3.2.1: Arboreal foliage and basal area at the leeward, ridge and windward sites for both DBH ≥ 5cm and DBH ≥ 10cm classes.

These differences in total basal area mentioned above were obviously reflected in the distribution of stem diameters, where both the ridge and windward sites presented a high concentration of the narrowest diameter class, whereas the leeward forest showed a greater proportion of the large diameter classes and interestingly did not show the typical high frequency in the lowest class (Figure 3.3.2.2). This trend was also shown for the distribution of height classes, where again the ridge and windward forest sites show a similar pattern distinct to that of the taller leeward site, which also showed a bimodal distribution indicating to some degree a second understorey canopy level (Table 3.3.1.1, Figure 3.3.2.3). The distribution of crown diameters also showed this distinction between the leeward and other forests, of note is the lower frequency of the smaller crown diameter classes in the leeward forest, an indication of the lower light availability of a relatively closed canopy (Figure 3.3.2.4).

The leeward forest presented a relatively closed canopy in terms of montane forest on a slope, albeit still broken, as shown by the plotted crown diameters (Figure 3.3.2.5), the ridge forest presented a very open canopy (Figure 3.3.2.6), while the windward forest presented a broken canopy, with a wide range of density within the plot (Figure 3.3.2.7).

0 5 10 15 20 25 30 35 40 0 2000 4000 6000 8000 10000 12000 14000 16000 Basa l Area (m2/ ha) Arbore al Foliage Area (m2/ha)

Figure 3.3.2.2: Distribution of diameter classes of 5-cm intervals at the leeward, ridge and windward forest plots.

Figure 3.3.2.3: Distribution of height classes of 1-m intervals at the leeward, ridge and windward forest plots.

Figure 3.3.2.4: Distribution of crown diameter classes of 2-m intervals at the leeward, ridge and windward forest plots.

Figure 3.3.2.5: Distribution of physical features and crown diameters (m) in the leeward forest sub-plots categorized by cluster group. Positions of crowns are vertical from base of stem and does not account for stem height/incline. Orange represents cluster group 1, lime green represents cluster group 2 and green represents cluster group 3. Solid black line indicates direction of slope descent. Dotted black lines indicate direction of descent of micro-topographic features. Solid blue line indicates stream. Doted blue line indicates streamlet initiating from spring within plot. Red dot indicates canopy tower. Maximum and minimum altitude are 2447m (X100:Y0) and 2414m (X0:Y100).

Figure 3.3.2.6: Distribution of physical features and crown diameters (m) in the ridge forest sub-plots categorized by cluster group. Positions of crowns are vertical from base of stem and does not account for stem height/incline. Orange represents cluster group 6, lime green represents cluster group 4 and green represents cluster group 5. Solid black line indicates direction of slope descent. Dotted black lines indicate direction of descent of micro-topographic features. Red dot indicates canopy tower. Maximum and minimum altitudes are 2834m (X48:Y100) and 2797m to the east (X100:Y0) and 2804m to the west (X0:Y0).

Figure 3.3.2.7: Distribution of physical features and crown diameters (m) in the windward forest sub-plots categorized by cluster group. Positions of crowns are vertical from base of stem and does not account for stem height/incline. Orange represents cluster group 9, lime green represents cluster group 7 and green represents cluster group 8. Solid black line indicates direction of slope descent. Dotted black lines indicate direction of descent of micro-topographic features. Red dot indicates canopy tower. Maximum and minimum altitudes are 2427m (X05:Y100) and 2380m (X100:Y0).

The distribution of arboreal foliage in the canopy shows that as opposed to the more open and broken canopies of the ridge and windward sites, the leeward site distribution of arboreal foliage shows a bimodal distribution, indicating an understorey canopy level at around 8 m, distinct from that of the upper canopy at 16 to 20 m (Figure 3.3.2.8).

Figure 3.3.2.8: Total arboreal foliage area at 4-m canopy height intervals at the leeward, ridge and windward forest plots.

The patterns of stem inclination reflected the slope and orientation characteristics of each plot, with the ridge forest showing the broadest distribution in inclination direction, while both the ridge and windward forests showing a greater proportion of highly inclining stems (Figure 3.3.2.9). The leeward forest presented the lowest amount (5.96 %) of inclined (< 60°) stems, while the ridge (20.71 %) and windward (27.08 %) forests showed a much greater incidence.

Figure 3.3.2.9: Distribution of stem incline angle and direction at all sites.

The best fit for the crown radius (CR) and DBH relationship for all stems ≥5 cm DBH for all forests was described by the cubic model (Figure 3.3.2.10, Figure 3.3.2.11 & Figure 3.3.2.12), followed by the quadratic and linear

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 4 8 12 16 20 24 28 32 Arbore al Foliage Area (m 2) Canopy Height (m)

models. The average CR-DBH ratio decreases with increasing DBH class (Table 3.3.2.1), although there was no acceptable fit for the CR-DBH ratio and DBH relationship for any of the forests (Figure 3.3.2.13, Figure 3.3.2.14 & Figure 3.3.2.15). These data indicate that significant crown foliage areas develop before significant basal areas, and furthermore that the small stems in the leeward forest appear to have a larger foliage area than those in the ridge and windward forests.

Table 3.3.2.1: Average CR-DBH ratio (SD) per DBH class from the leeward, ridge and windward forest 1-ha plots.

DBH Class

(cm) Leeward Ridge Windward

10 0.20 (0.07) 0.13 (0.05) 0.14 (0.06) 20 0.14 (0.05) 0.11 (0.05) 0.14 (0.05) 30 0.11 (0.04) 0.12 (0.04) 0.12 (0.03) 40 0.10 (0.03) 0.11 (0.03) 0.09 (0.04) 50 0.10 (0.03) 0.11 (0.02) - 60 0.07 (0.02) 0.07 (0.02) 0.09 ( - ) 70 0.05 (0.02) 0.09 (0.04) - 80 0.06 (0.01) - - 90 0.08 ( - ) - - 100 0.05 ( - ) - - 110 0.04 ( - ) - - 120 0.09 ( - ) - - 130 0.01 ( - ) - - 140 0.07 ( - ) - -

Figure 3.3.2.11: Relationship between DBH and crown radius (Cubic model) at the ridge forest plot.

Figure 3.3.2.12: Relationship between DBH and crown radius (Cubic model) at the windward forest plot.

Figure 3.3.2.13: Relationship between DBH and the CR-DBH ratio (linear model) at the leeward forest plot.

Figure 3.3.2.14: Relationship between DBH and the CR-DBH ratio (linear model) at the ridge forest plot.

Figure 3.3.2.15: Relationship between DBH and the CR-DBH ratio (linear model) at the windward forest plot.