# Parallel Seasonal Patterns of Photosynthesis, Fluorescence, and Reflectance Indices in Boreal Trees
## Materials and Methods  
Six different tree species were grown on the rooftop of the Biological Sciences Building at the University of Alberta, Canada (53.528861, \(-\)113.525972), and were exposed to a seasonally changing boreal climate. The trees used for this study included three winter deciduous species--trembling aspen (_Populus tremuloides_) and balsam poplar (_Populus balsamifera_) as broad-leaf species, and tamarack (_Larix laricina_), a deciduous conifer--and three evergreen species: black spruce (_Picea mariana_), white spruce (_Picea glauca_), and jack pine (_Pinus banskiana_). Trees were potted in deep pots and arranged in monocultural plots in the spring of 2015. The trees were potted in 2.83 L pots (TP414, Stuewe & Sons, Tangent, OR, USA) in the spring of 2015. One-year-old seedlings of each species, except white spruce seedlings, which were 2 years old, were planted in a mixture of 3:1 potting soil (Sunshine Mix 4, Sun Gro Horticulture, Agawam, MA, USA) and topsoil. The mix was supplemented with a slow-release fertilizer (Nutricote 14-14-14, Sun Gro Horticulture, Agawam, MA, USA), at ca. 150 g per 60 L of soil. To help the trees overwinter in the first year, plants were placed in 1.2 m \(\times\) 1.2 m plywood frames. The trees were repotted into 6.23 L pots (TP616, Stuewe & Sons, Tangent, OR, USA) in April 2016, to allow for adequate moisture and nutrient availability, avoid potential root restriction, and provide greater spacing of the plants. To provide insulation during the winter, the tree-pots were surrounded by small pots of peat. During the 2015 growing season, the trees were watered daily and fertilized periodically with a 400 ppm mixture of 20-20-20 fertilizer. In June 2016, the plants were fertilized with a 200 ppm mixture of 20-20-20 fertilizer to provide additional nutrients for the growing season. Data were collected from December 2015 to January 2017, covering a full yearly growth cycle. Measurements were taken approximately every 2 weeks (weather permitting) between 12:30 and 14:30 UTC-06 (within \(\sim\)1 h of solar noon); to ensure maximal sunlight and reduce potential cloud-cover impacts, data were collected on mostly sunny days. When all data could not be collected on a single day, due to the small window for sampling around solar noon, sampling occurred on sequential days under near-identical conditions. An automated weather station provided air temperature (S-THB-M002, Onset, Bourne, MA, USA) and PPFD (S-LIA-M003, Onset, Bourne, MA, USA) data, collected every minute on a data logger (U30-NRC, Onset, Bourne, MA, USA). Temperature and PPFD were aggregated into 15 min averages. PPFD was expressed as midday averages (13:00-14:00; UTC-06) and temperature was expressed as daily averages. Daily average temperature expressed as 30-year climate normals (1981-2010) by month were obtained from the Edmonton City Centre A Climate Normals Station (Climate ID 301228) [36]. Canopy-level reflectance measurements were collected using a dual-detector field spectrometer (UniSpec-DC; PP Systems, Amesbury, MA, USA) equipped with two fibre-optics. A downward-looking fibre (UNI684; PP Systems), fitted with a field-of-view restrictor (UNI688; PP Systems) to limit the field of view to ca. 15\({}^{\circ}\), measured target reflectance, while an upward-facing fibre (UNI686; PP Systems), attached to a cosine receptor (UNI435; PP Systems), detected incoming irradiance. Five measurements were taken at different locations above each monoculture and mixed plot (center, NW, NE, SW, and SE) ca. 1 m above the top of the canopy. Canopy reflectance was calculated by referencing the downward-looking target radiance (\(R_{\lambda}\)) spectrum to the upward-looking irradiance (\(I_{\lambda}\)) spectrum.