Continuous quantification of forest microclimate temperatures in space and time using fibre-optic technology

Abstract

Most species experience microclimate temperatures, that is, variable and fine-grained thermal conditions determined by atmospheric conditions interacting with biotic and abiotic components of the earth's surface. Unfortunately, measuring microclimates at biologically meaningful grain sizes is challenging. We showcase the potential of fibre-optic distributed temperature sensing (DTS) to quantify diurnal variation in microclimatic air temperatures during the growing season along a 135-m forest edge-to-interior transect at 25-cm horizontal resolution. We benchmark DTS measurements against the microclimate quantified with ultrafine wire thermocouples and more conventional sensors at 15-m intervals along the transect. Diurnal measurements from DTS indicate maximal cooling of forest floor temperatures (up to −6°C) in the morning (around 8:00 AM) and well away from the forest edge. Negative offset values gradually increased during the day reaching zero (0°C) in the evening (around 21:00 PM). Synthesis. While both DTS and discrete point sampling with microclimate loggers allow to quantify diurnal cycles of microclimate gradients with unified spatial and temporal patterns, DTS provides accurate temperature measurements at a spatial detail nearly impossible to achieve with discrete point sampling. When applied over transects of several hundreds of meters—up to kilometres—fibre-optic DTS is a cost-efficient alternative offering substantial potential to advancing microclimate research.