Abstract:
The damage caused by strong wind to individual tree and forest systems is huge, which cannot be ignored. The primary issue to ensure the wind-induced safety of trees is to understand the characteristics of tree-wind interaction during strong wind, especially the wind-induced response of trees. For this reason, the deciduous broadleaved forest of the National Field Scientific Observation and Research Station of the Maoershan Forest Ecosystem in Heilongjiang was taken as the research object, and the characteristics of average and fluctuating wind of the forest during the three strong wind periods were measured and studied, as well as the fluctuating wind load and wind-induced response of a
Betula platyphylla Suk in the forest were analyzed. The results show that the disturbance effect of trees causes the average wind to deflect with height of measurement point. The deflection gradient is large within the range of the canopy height, and the deflection gradient outside the canopy height is small. The maximum wind deflection angle is approximately 67°. The disturbance effect of the trees increases the turbulence intensity of the wind field in the canopy, and this influence increases with the intensity of the incoming wind. During the three strong wind periods, the trees exhibited complex random vibrations under the action of fluctuating wind. The peak frequency of the vibration response was consistent with that of the free vibration of the trees, and irrelevant to the fluctuating wind characteristics of the incoming wind. The peak frequency of the mechanical transfer function of broadleaved trees is identical with that of the response power spectrum. The mechanical transfer function of the wind-induced response of the
Betula platyphylla Suk is almost the same as that of the forced damped harmonic oscillator, which is similar to conifer.