Field Studies

Accelerometers provided a proxy for frond motion [26]. Time series of water elevation data and accelerometer data (Figure 3.12) showed marked differences. The forcing of the tested individuals by the waves was obviously complex (Figure 3.12a). Despite the wave field being visually well ordered with contiguous crests arriving at regular intervals, the direct observations revealed a complicated distribution of peaks and troughs. There were substantial differences in response of the two species to waves as well as differences in how the regions of the frond reacted. In particular, D. antarctica (Figure 3.12, samples 1 and 2) exhibited far sharper "shock-like" responses, lasting only a fraction of a second (sampling at 10 Hz) than those exhibited by D. willana (Figure 3.12, samples 3 and 4). The D. antarctica response was not particularly different on the palm compared with the blade. In contrast, the accelerometers attached to D. willana on the palm (Figure 3.12, samples 3) and blade

FIGURE 3.11 Correlation between the mass and buoyancy for 10 individuals of D. antarctica. The black oblique line indicates the regression, while the black dashed lines are the 95% CI for the linear regression. The gray horizontal line indicates the mean for all tested individuals, while the dashed horizontal lines represent the 95% CI.

FIGURE 3.11 Correlation between the mass and buoyancy for 10 individuals of D. antarctica. The black oblique line indicates the regression, while the black dashed lines are the 95% CI for the linear regression. The gray horizontal line indicates the mean for all tested individuals, while the dashed horizontal lines represent the 95% CI.

(Figure 3.12, samples 4) showed a slower response than D. antarctica and differed from one another. The palm response of the D. willana sample could only weakly be visually correlated with the wave gauge record.

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