Foliage Canopy Influences on Diurnal Temperatures

Deciduous forests experience seasonal changes of foliage cover with leaf growth in the spring and leaf loss in the autumn. These changes in foliage cover can substantially influence the atmospheric microclimate of the forest. This study examines the influence that spring transition from no foliage to full foliage has on under-canopy forest temperatures by comparing interior forest to adjacent field atmospheric measurements. Data was collected during two multi-month spring seasons by weather stations located at the Hanley Biological Preserve in the New York State Finger Lakes region. In addition to atmospheric measurements, hemispherical fisheye photographs were collected to quantify forest foliage cover throughout the measurement periods. The periods of transition in foliage cover were determined through fisheye image analysis and examination of the ratio of solar radiation between the field and forest. As the foliage cover increased throughout the season, the amount of solar radiation that was received at the forest site decreased and the range between the daily maximum and minimum temperatures became notably different than the range measured at the field site. During the no foliage period, the daily temperature range between the field and forest sites were similar. During foliage transition and full foliage periods, the daily temperature range in the field became greater compared to the daily temperature range in the forest. Future research on this project will explore the influence of foliage cover on the variability of other microclimate variables, such as moisture and winds.