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Fig. 4. Four-year survival (proportion) of Eucalyptus tetrodonta and E. miniata averaged together: modelled values of survival as a function of tree diameter, for a range of pipe ratios. No eucalyptus <20 cm dbh had a pipe ratio >0.6.

Figure 4 Four-year survival (proportion) of Eucalyptus tetrodonta and E. miniata averaged together: modelled values of survival as a function of tree diameter, for a range of pipe ratios. No eucalyptus <20 cm dbh had a pipe ratio >0.6.

Related Figures (3)

Fig. 1. Frequency of piped stems for six tree size classes (5-10, 10-15, 15-20, 25-30, and >30 cm dbh) for Eucalyptus. tetrodonta (n = 165) and for E. miniata (n = 102) in northern Australia. There were no E miniata trees 5-10 cm dbh. Bars show actual numbers; lines show model-averaged proportion of piped stems. Generalised linear mixed effects models (GLMMs) and linear mixed effects models (LMEs) were used for all analyses. Plot was a random effect in all models, which allowed the use of all observations on individual trees whilst still accounting for the spatial grouping of the trees (Crawley, 2002). Binomial GLMMs with a logit link were used to investigate frequency of piping and tree survival, LMEs for piped diameter, pipe ratio and growth. The interaction between dbh and species was included in all the above analyses. The candidate model sets are listed in Tables 1 and 2. We used the weighted averaged coefficients of all models receiving >10% of the AlCc weight to calculate the predicted values presented in figures and tables. Overwhelmingly, termite-pipes were negatively correlated with size-dependent growth of Eucalyptus tetrodonta and with the probability of survival of either E. tetrodonta or E. miniata.
Fig. 1. Frequency of piped stems for six tree size classes (5-10, 10-15, 15-20, 25-30, and >30 cm dbh) for Eucalyptus. tetrodonta (n = 165) and for E. miniata (n = 102) in northern Australia. There were no E miniata trees 5-10 cm dbh. Bars show actual numbers; lines show model-averaged proportion of piped stems. Generalised linear mixed effects models (GLMMs) and linear mixed effects models (LMEs) were used for all analyses. Plot was a random effect in all models, which allowed the use of all observations on individual trees whilst still accounting for the spatial grouping of the trees (Crawley, 2002). Binomial GLMMs with a logit link were used to investigate frequency of piping and tree survival, LMEs for piped diameter, pipe ratio and growth. The interaction between dbh and species was included in all the above analyses. The candidate model sets are listed in Tables 1 and 2. We used the weighted averaged coefficients of all models receiving >10% of the AlCc weight to calculate the predicted values presented in figures and tables. Overwhelmingly, termite-pipes were negatively correlated with size-dependent growth of Eucalyptus tetrodonta and with the probability of survival of either E. tetrodonta or E. miniata.
Fig. 2. Growth (dbh increment) of canopy eucalypts of northern Australia as a function of tree diameter (dbh) across a range of pipe ratios: modelled values for Eucalyptu tetrodonta (a) and E. miniata (b) and field data for E. tetrodonta (c) and E. miniata (d). Eucalyptus miniata was unlike other savanna species investi- gated by Werner and Prior (2007) in that small trees were almost always piped, more than 85%, a frequency similar to that of large trees. Thus, even random selection of E. miniata trees for harvest would yield 85% piped trees. On the other hand, the frequency of piping in E. tetrodonta stems, while less overall than in E. miniata, was still high enough (>60% in all size classes) for this species to be attractive for harvesting for didgeridoo manufacture. While E. phoenicea F. Muell. (the third species important for didgeridoo manufacture; Whitehead et al., 2006) was not found in the study area, it is very closely related to E. miniata (Dunlop et al., 1995), and it would be interesting to investigate whether frequency of piping and relationships among size, pipe ratio, life history, and survival are similar. Lower survival rates were also associated with smaller diameters and with large pipe ratios (Figs. 3 and 4). These relationships were similar for the two species, with only slightly higher survival for E. tetrodonta. By way of example using modelled data for the two species averaged together (Fig. 4), the survival rate of the smallest (10 cm dbh) intact (unpiped) trees was 86%. This steadily decreased across trees with a greater degree of piping, down to 64% in those small trees with 80% piping. Among 25 cm (dbh) trees, the comparison in survival was 96% vs. 87%, for unpiped and 80% piping, respectively. Only among the largest trees
Fig. 2. Growth (dbh increment) of canopy eucalypts of northern Australia as a function of tree diameter (dbh) across a range of pipe ratios: modelled values for Eucalyptu tetrodonta (a) and E. miniata (b) and field data for E. tetrodonta (c) and E. miniata (d). Eucalyptus miniata was unlike other savanna species investi- gated by Werner and Prior (2007) in that small trees were almost always piped, more than 85%, a frequency similar to that of large trees. Thus, even random selection of E. miniata trees for harvest would yield 85% piped trees. On the other hand, the frequency of piping in E. tetrodonta stems, while less overall than in E. miniata, was still high enough (>60% in all size classes) for this species to be attractive for harvesting for didgeridoo manufacture. While E. phoenicea F. Muell. (the third species important for didgeridoo manufacture; Whitehead et al., 2006) was not found in the study area, it is very closely related to E. miniata (Dunlop et al., 1995), and it would be interesting to investigate whether frequency of piping and relationships among size, pipe ratio, life history, and survival are similar. Lower survival rates were also associated with smaller diameters and with large pipe ratios (Figs. 3 and 4). These relationships were similar for the two species, with only slightly higher survival for E. tetrodonta. By way of example using modelled data for the two species averaged together (Fig. 4), the survival rate of the smallest (10 cm dbh) intact (unpiped) trees was 86%. This steadily decreased across trees with a greater degree of piping, down to 64% in those small trees with 80% piping. Among 25 cm (dbh) trees, the comparison in survival was 96% vs. 87%, for unpiped and 80% piping, respectively. Only among the largest trees
Fig. 3. Four-year survival (proportion) of individual trees of Eucalyptus tetrodonta and E. miniata averaged together, for three diameter (dbh) classes (<15 cm dbh, 15- 25cm dbh, and >25 cm dbh) and four pipe ratio classes (zero piping, >0-0.10, >0.10-0.40, and >0.40.) Only classes containing >10 individual trees are shown. Bars show actual numbers; lines show the model-averaged proportion of trees that survived.
Fig. 3. Four-year survival (proportion) of individual trees of Eucalyptus tetrodonta and E. miniata averaged together, for three diameter (dbh) classes (<15 cm dbh, 15- 25cm dbh, and >25 cm dbh) and four pipe ratio classes (zero piping, >0-0.10, >0.10-0.40, and >0.40.) Only classes containing >10 individual trees are shown. Bars show actual numbers; lines show the model-averaged proportion of trees that survived.
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