A Linear Analysis of the Interaction Between the Atmosphere and an Underlying Compliant Plant Canopy

We summarise the results of a theoretical investigation of the interaction between the lower atmosphere and a compliant plant canopy. In this investigation, plant collisions were modelled as simple spring or dashpot interactions between adjacent plants. Linearised canopy models show that dashpot collisions and spring collisions are effective at reducing the amplitude of a canopy’s response to wind forcing, and may thus serve to stabilise plants against lodging and windthrow. Both types of collisions can also induce shifts in the stand resonance frequency and may thus serve to stabilise stands even further by shifting the canopy resonance frequency away from the most energetic frequencies in the atmospheric power spectrum. We also include a linear analysis of the shear layer instability over a waving canopy, and show that canopy drag has a strong effect on the instability. However, stem stiffness and inter-plant collisions have only minor effects on the wavenumber, growth rate, and frequency of the most unstable wave.