2.3 Results
2.3.2 Cecropia species in Yasun´ı, Ecuador
Of the 586Cecropiatrees above 10 cm DBH in the 2007 census of the forest plot, in 2011, 222 were found to be dead or heavily damaged. Even thoughCecropiaare a fast growing pioneer species, this was an unexpectedly high loss of individuals within a period of only 4 years, which might be explained by heavy storms in the time between the 2007 census and my field work. Only very few individuals of the second most common speciesC. ficifolia were found to be flowering. This might be due to the population suffering from wide-spread parasites, because many C. ficifolia had damaged leaves. But it could also be related to the fact that smaller mid-canopy species such asC. ficifoliamay suffer from insufficient light exposure in such a closed canopy forest environment. Another possibility could be that it was not the main flowering season forC. ficifolia. Because of the large number of dead trees and because not manyC. ficifoliawere found flowering, only forC. sciadophyllacould sufficient data be collected to enable any form of statistical analysis. The number of individuals of different species flowering in the different health classes is recorded in Table 2.1.
The first notable result is that forC. sciadophyllathe number of male and female flow- ering individuals in the forest plot was nearly even. The data for other species is too sparse to draw any strong conclusions. However, I note that 5 out of 7 floweringC. ficifoliawithin the forest plot and 3 out of 4 along the road were female, whereas forC. herthae8 out of 9 flowering individuals in the plot and both individuals found along the road were male (see
100 200 300 400 500 600 700 800 900 1000 0.8
1 1.2 1.4 1.6 1.8 2 2.2
Abundance Mean aggregation log 10(1+Ω 0−10)
Figure 2.4: The graph shows the relationship between population abundance and aggregation for simulated dioecious species (solid line) with equal chance for individuals to be male or female, and non-dioecious species (dashed line). The dotted lines show the 5 and 95 percentile of the simulation results for the dioecious species. All results are showing the meanΩ0,10at the end of 1000 runs of the simulation after generation 200.
Species code Number of trees with that health level (top total, left female, right male)
0 1 2 3 4 P
C. sciadophylla 134 4 18 16 171 343
0 0 0 0 2 1 2 6 52 51 56 58
C. ficifolia 46 10 10 6 80 152
0 0 0 0 0 0 0 0 5 2 5 2
C. herthae 9 0 3 1 24 37
0 0 0 0 0 0 0 0 1 8 1 8
C. engleriana 9 0 1 2 22 34
0 0 0 0 0 0 2 0 5 8 7 8
C. putumayonis 3 1 0 0 5 9
0 0 0 0 0 0 0 0 0 0 0 0
C. marginalis 2 1 0 0 1 4
0 0 0 0 0 0 0 0 0 0 0 0
C. membranacea 3 0 0 0 1 4
0 0 0 0 0 0 0 0 0 0 0 0
Table 2.1: Cecropiasurveyed within the 50 ha forest dynamic plot in Yasun´ı National Park, Ecuador. Health levels were defined as: 0 for dead/disappeared; 1 for severely damaged [broken and/or completely covered in lianas without leaves left]; 2 for damaged individuals [broken, liana covered or which had lost many/most leaves]; 3 for individuals with minor damage [tilted, with one liana, or which had lost some leaves], and 4 for individuals for which no damage was recorded.
2.3. Results 38
100 200 300 400 500 600 700 800 900 1000
0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8
Mean aggregation log 10(1+Ω 0−10)
(Expected) number of seed producing individuals in population
Figure 2.5: The graph shows the relationship between sex ratio and aggregation for simulated non-dioecious species with varying abundance (solid black line), and for dioecious species with a total abundance of 1000 individuals and varying sex-ratio (black dotted line show the aggregation for only the male individuals of the dioecious species, the dashed line for only the females, and the dashed-dotted line for all individuals). All results are showing the mean Ω0,10at the end of 1000 runs of the simulation after generation 200.
Species code Number of trees with that health level (top total, left female, right male)
0 1 2 3 4 P
C. sciadophylla 0 3 15 23 77 118
0 0 0 0 2 3 3 4 16 35 21 42
C. ficifolia 0 0 0 2 7 9
0 0 0 0 0 0 1 0 2 1 3 1
C. herthae 0 0 1 1 5 7
0 0 0 0 0 0 0 0 0 2 0 2
C. engleriana 0 0 0 2 4 6
0 0 0 0 0 0 1 1 3 1 4 1
CECR?? 0 1 0 0 4 5
0 0 0 0 0 0 0 0 0 2 0 2
Table 2.2: Cecropiasurveyed along the road. Health levels were defined as as shown in Table 2.1. The line marked CECR?? reports the results for all individuals with undetermined species identity.
100 200 300 400 500 600 700 800 150
200 250 300 350 400 450 500 550 600 650
DBH measured at 2007 census
DBH measured in 2011
Figure 2.6: The Figure shows the DBH in 2007 compared to the DBH in 2011 for all flow- eringC. sciadophyllatrees within the 50 ha forest dynamic plot as Yasun´ı, Ecuador. Female individuals for which DBH was measured in 2011 are represented by a black O, males with a. For individuals that could not be measured in 2011, the DBH value for 2011 was es- timated by a linear fit to the data of the individuals that could be measured (one outlier for which the DBH measured in 2011 was much smaller than the DBH in 2007 was excluded for the fit). Females with estimated 2011 DBH values are depicted by a black∗, males with a+.
Table 2.2 for the results of the road census). This suggest that sex ratios and flowering fre- quency of the two sexes might differ between the species. Along the road there were twice as many flowering male compared to female C. sciadophyllatrees (42 males compared to 21 females). This suggests that the flowering frequency of different sexes might be differ- entially affected by light availability. There is no large difference with respect to the DBH of the flowering individuals between male and femaleC. sciadophylla(see Figure 2.6). The mean DBH of flowering females within the plot was 34.9 cm (s.d. 10.3), for males it was 34.1 cm (s.d. 10.7). The mean DBH of the floweringC. sciadophylla along the road was slightly lower (33.0 cm for females and 33.7 cm for males), but there was no indication that the larger proportion of males flowering could be explained by an earlier onset in flowering for the males. As expected from the simulation model we found males to be slightly less aggregated than females. TheΩ0,10relative neighbourhood co-association measure was 7.8 within all individuals, but 10.2 within the female sub-population and only 6.6 within the male sub-population.
2.3. Results 40
1.5 2 2.5 3 3.5 4 4.5
-1 -0.5 0 0.5 1 1.5 2
log abundance residual log 10(1+Ω 0-10)
Figure 2.7: The graph shows the residual aggregation of the linear regression model after accounting for current abundance. Non-dioecious species are represented by ∆; dioecious species by O. There does not seem to be a systematic difference in aggregation related to breeding system.