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

Sven Kolbe,Manuel Mohr,Laurin Osterholt,Martin Maier,Dirk Schindler,Barry Gardiner

doi:10.3390/f13020225

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.

Highlights

Publisher’s Note: MDPI stays neutralThe characteristics of near-ground wind fields are important physical site factors that contribute to the development and survival of trees and forests [1,2]
The presented results show that ground-based measurements of air pressure fluctuations are suitable for estimating the temporal dynamics of mean and extreme tree response in a planted Scots pine forest
The results demonstrate that one air pressure measurement is sufficient to obtain spatially representative estimates of wind conditions over the forest in the presented measurement grid

Summary

Introduction

The characteristics of near-ground wind fields are important physical site factors that contribute to the development and survival of trees and forests [1,2]. Information on above- and below-canopy wind characteristics is limited because the standard weather stations operated in the networks of the national weather services are located outside forests. Within stand wind characteristics are mainly known from specialized sites of forest research institutes [7,8], research networks such as the European Integrated Carbon Observation System [9], and the International Cooperative Programme on Assessment and Monitoring of Air pollution Effects on Forests [10]. Little systematic information and data are available on the wind fields in and over forests. The reasons for the lack of wind measurement sites in forests are the great effort required to make such measurements, the lack of infrastructure, and the low spatial representativeness of below-canopy measurements. Due to large vertical extent of forests, it is with regard to jurisdictional claims in published maps and institutional affiliations

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Conclusion