Radiation Heat Transfer and Microclimate in and Around Isolated Conifers

Radiation transport to and from plant canopies plays a central role in a wide variety of ecosystem processes including urban environments where radiation directly impacts building energy use and thermal comfort and natural and managed plant canopies where radiation impacts water use, plant growth, and pest/pathogen viability. In general, in all of these environments knowledge the role of radiation transport and microclimate at the individual tree scale on wider scale processes is critical. In most plant canopy studies and modeling efforts two linked components are missing: the importance of species type and the effect of sub tree scale features. Understanding the role of these components on microclimate within the larger domain of energy use in cities and management in agricultural and natural plant canopies is critical to developing strategies for sustainable management. This study extends the research of Bailey et al. [Bailey, B. N., Overby, M., Willemsen, P., Pardyjak, E. R., Mahaffee, W. F., and Stoll, R. (2014). A scalable plant-resolving radiative transfer model based on optimized GPU ray tracing. Agric. For. Meteorol. 198-199: 192-208] , which described how microclimate quantities such as radiation components and surface temperatures are modeled in complex broad leaf canopies, to coniferous canopies. Bailey et al. (2014) provide a methodology for describing the impact of sub-plant heterogeneity on radiative heat transfer in broad leaf canopies, which is still lacking for conifers. As a first step, we present analysis of new experimental field data taken in and around a Blue Spruce (Picea pungens) tree. The goal was to determine the dominant radiative heat transfer variables in conifer canopies both at the plant and sub-plant scales. Components of radiative heat transfer were measured in two separate P. pungens trees using an array of radiation and temperature sensors. Using sensors placed at various points throughout the conifer trees, the fluxes were measured for incoming and outgoing longwave, shortwave and photosynthetically active radiation bands. In addition needle temperature in both trees and ground and air temperature around the trees was also recorded. Analysis of these data can be used to direct which factors are key to radiative heat fluxes in conifer species.