Aerodynamic scaling for estimating the mean height of dense canopies

We used an aerodynamic method to objectively determine the representative canopy height, using standard meteorological measurements. The canopy height may change if the tree height is used to represent the actual canopy, but little work to date has focused on creating a standard for determining the representative canopy height. Here we propose the ‘aerodynamic canopy height’ ha as the most effective means of resolving the representative canopy height for all forests. We determined ha by simple linear regression between zero-plane displacement d and roughness length z0, without the need for stand inventory data. The applicability of ha was confirmed in five different forests, including a forest with a complex canopy structure. Comparison with stand inventory data showed that ha was almost equivalent to the representative height of trees composing the crown surface if the forest had a simple structure, or to the representative height of taller trees composing the upper canopy in forests with a complex canopy structure. The linear relationship between d and z0 was explained by assuming that the logarithmic wind profile above the canopy and the exponential wind profile within the canopy were continuous and smooth at canopy height. This was supported by observations, which showed that ha was essentially the same as the height defined by the inflection point of the vertical profile of wind speed. The applicability of ha was also verified using data from several previous studies

Key residues on microtubule responsible for activation of kinesin ATPase

Microtubule (MT) binding accelerates the rate of ATP hydrolysis in kinesin. To understand the underlying mechanism, using charged-to-alanine mutational analysis, we identified two independent sites in tubulin, which are critical for kinesin motility, namely, a cluster of negatively charged residues spanning the helix 11–12 (H11–12) loop and H12 of α-tubulin, and the negatively charged residues in H12 of β-tubulin. Mutation in the α-tubulin-binding site results in a deceleration of ATP hydrolysis (kcat), whereas mutation in the β-tubulin-binding site lowers the affinity for MTs (K0.5MT). The residue E415 in α-tubulin seems to be important for coupling MT binding and ATPase activation, because the mutation at this site results in a drastic reduction in the overall rate of ATP hydrolysis, largely due to a deceleration in the reaction of ADP release. Our results suggest that kinesin binding at a region containing α-E415 could transmit a signal to the kinesin nucleotide pocket, triggering its conformational change and leading to the release of ADP