On the Potential of Using Air Pressure Fluctuations to Estimate Wind-Induced Tree Motion in a Planted Scots Pine Forest

Abstract

This paper reports statistical relationships between measured airflow, air pressure fluctuations, and the wind-induced motion of planted Scots pine trees (Pinus sylvestris L.). The results presented illustrate the potential of low-cost, ground-based air pressure measurements for monitoring wind-induced tree response. It is suggested that air pressure fluctuations can be used as surrogate information for above-canopy airflow, often used to estimate wind loads on forest trees. We demonstrate that air pressure fluctuations can be measured representatively at the forest floor and correlate very well with wind speed and direction at mean canopy-top (18 m a.g.l.) and above the 18 m high, 56-year-old forest. Their strong correlation (coefficient of determination R2 > 0.77) allows a good approximation of airflow conditions above the canopy, and, with some limitations, in the below-canopy space. Air pressure fluctuations also correlate very well with wind-induced tree motion with a similar correlation to that between wind speed and tree motion. Furthermore, the main directions of wind-induced tree motion agree very well with the propagation direction of air pressure waves. Above-canopy airflow measurements in forests with a large vertical extent are rare, and often require tall wind measurement towers. Therefore, we consider the estimation of airflow conditions over forests using ground-based air pressure measurements a promising option for monitoring the airflow conditions of relevance for predicting wind-induced tree response over large areas using a minimum of measurement infrastructure.