Table 1. Samples of broadleaved species. Time series measurements are in bold. Time series measurements were used only when analyzing the seasonal variations in the spectra.
Species Location Date(s) N trees Tree height,
m
Canopy positions* N samples per each canopy position in a tree Leaf
sides**
N measured spectra
Acer platanoides Otaniemi 8.7.2016 2 6.2, 13.2 E/S 3 A/B 24
Alnus glutinosa Otaniemi 8.7.2016 2 13.6, 22.1 E/S 3 A/B 24
Alnus incana Otaniemi 6.7.2016 2 6.2, 18.0 E/S 3 A/B 24
Betula papyrifera Kumpula 12.7.2016 2 13.7, 17.1 E/S 3 A/B 24
Betula pendula Otaniemi 16.–17.5.2016 3 5.6, 6.1, 7.2 E/S 3 A/B 36
20.5.2016 1 7.2 E/S 3 A/B 12
2.-3.6.2016 3 5.6, 6.1, 7.2 E/S 3 A/B 36
29.6.2016 3 5.6, 6.1, 7.2 E/S 3 A/B 36
28.7.2016 3 5.6, 6.1, 7.2 E/S 3 A/B 36
25.8.2016 3 5.6, 6.1, 7.2 E/S 3 A/B 36
7.10.2016 3 5.6, 6.1, 7.2 E/S 3 A/B 36
Populus balsamifera Kumpula 12.7.2016 1 4.8 E 12 A/B 24
Populus tremula Otaniemi 17.5.2016 3 8.2, 8.9, 10.3 E/S 3 A/B 36
20.5.2016 1 8.2 E/S 3 A/B 12
2.-3.6.2016 3 8.2, 8.9, 10.3 E/S 3 A/B 36
29.–30.6.2016 3 8.2, 8.9, 10.3 E/S 3 A/B 36
28.–29.7.2016 3 8.2, 8.9, 10.3 E/S 3 A/B 36
25.8.2016 3 8.2, 8.9, 10.3 E/S 3 A/B 36
10.7.2016 3 8.2, 8.9, 10.3 E/S 3 A/B 36
Populus tremuloides Ruotsinkylä 21.7.2016 1 17.8 E/S 6 A/B 24
Prunus padus Otaniemi 8.7.2016 2 8.5, 9.1 E/S 3 A/B 24
Quercus robur Otaniemi 6.7.2016 2 3.1, 21.6 E/S 3 A/B 24
Salix caprea Otaniemi 4.7.2016 2 11.9, 16.7 E/S 3 A/B 24
Sorbus aucuparia Otaniemi 6.7.2016 2 11.5, 13.0 E/S 3 A/B 24
Tilia cordata Viikki 24.8.2016 2 5.8, 16.7 E/S 3 A/B 24
* E = Sun-exposed, S = shaded
** A = adaxial, B = abaxial
Table 2. Samples of coniferous species. Time series measurements are in bold. These were only used when analyzing the seasonal variations in the spectra.
Species Location Date(s) N trees Tree height,
m
Canopy positions* Age cohorts** N samples per each canopy position and age cohort in a tree Needle sides*** N
measured spectra
Abies balsamea Viikki 20.7., 17.8.2016 2 11.1¸12.7 E/S c0/c1 3 A/B 48
Abies sibirica Viikki 23.8.2016 1 23.7 E/S c0/c1 3 A/B 24
Larix gmelinii Viikki 4.8.2016 1 14.1 E/S c0 6 A/B 24
Larix laricina Viikki 22.8.2016 1 16.7 E/S c0 6 A/B 24
Larix sibirica Viikki 3.8.2016 1 26.7 S c0 12 A/B 24
Picea abies Otaniemi 14.–23.6.2016 2 16.4, 22.6 E/S c0/c1 3 - 24
26.7.–1.8.2016 2 16.4, 22.6 E/S c0/c1 3 - 24
12.–13.9.2016 2 16.4, 22.6 E/S c0/c1 3 - 24
Picea glauca Viikki 30.8.2016 2 11.4, 14.9 E/S c0/c1 3 - 24
Picea mariana Viikki 18.–19.8.2016 2 8.4, 9.0 E/S c0/c1 3 - 24
Pinus banksiana Viikki 19.8., 24.8.2016 1 13.7 E/S c0/c1 6 A/B 48
Pinus contorta Viikki 18.7., 17.8.2016 2 17.1, 19.7 E/S c0/c1 3 A/B 48
Pinus sylvestris Otaniemi 17.–22.6.2016 2 13.3, 14.2 E/S c0/c1 3 A/B 48
22.–25.7.2016 2 13.3, 14.2 E/S c0/c1 3 A/B 48
12.–14.9.2016 2 13.3, 14.2 E/S c0/c1 3 A/B 48
Pseudotsuga menziesii Viikki 11.7., 16.8.2016 2 20.7, 26.2 E/S c0/c1 3 A/B 48
* E = Sun-exposed, S = shaded
** c0 = current year needles, c1 = previous year needles
*** A = adaxial, B = abaxial
1

Fig. 1. Mean reflectance, transmittance, and albedo spectra by genus in broadleaved (a,c) and coniferous (b,d) trees. View larger in new window/tab.

2

Fig. 2. Coefficients of determination (R2) when variability of reflectance, transmittance, and albedo spectra of broadleaved tree leaves were explained by species, genus, leaf side (adaxial/abaxial), and canopy position (sun-exposed/shaded) in one-way ANOVA. Statistically non-significant regions (p > 0.05) are highlighted in gray. The x-axis denotes wavelength (nm) and y-axis coefficient of determination (0–1).

3

Fig. 3. Coefficients of determination (R2) when variability in reflectance, transmittance, and albedo spectra of coniferous needles were explained by species, genus, needle side (adaxial/abaxial), and canopy position (sun-exposed/shaded) in one-way ANOVA. Statistically non-significant regions (p > 0.05) are highlighted in gray. The x-axis denotes wavelength (nm) and y-axis coefficient of determination (0–1).

Table 3. Coefficients of determination (R2) when variability of red edge inflection point (REIP) were explained by species, genus, leaf or needle side (adaxial/abaxial), canopy position (sun-exposed/shaded), and needle age in one-way ANOVA. Corresponding p-value is given in brackets.
REIP
(reflectance)
REIP (transmittance) REIP
(albedo)
Broadleaved
  Species 0.12 (0.00) 0.24 (0.00) 0.23 (0.00)
  Genus 0.07 (0.00) 0.12 (0.00) 0.09 (0.00)
  Leaf side 0.45 (0.00) 0.03 (0.00) 0.16 (0.00)
  Canopy position 0.02 (0.03) 0.07 (0.00) 0.07 (0.00)
Coniferous
  Species 0.45 (0.00) 0.67 (0.00) 0.61 (0.00)
  Genus 0.29 (0.00) 0.46 (0.00) 0.41 (0.00)
  Leaf side 0.14 (0.00) 0.00 (0.70) 0.02 (0.01)
  Canopy position 0.00 (0.84) 0.00 (0.38) 0.00 (0.39)
  Needle age 0.07 (0.00) 0.11 (0.00) 0.09 (0.00)
4

Fig. 4. Mean spectral differences between abaxial vs. adaxial sides of leaves and needles (a,b) and between shaded vs. sun-exposed canopy positions (c,d).

5

Fig. 5. Spectral differences between two age cohorts of coniferous needles (new i.e. current year – previous year).

6

Fig. 6. Seasonal trends in silver birch (Betula pendula) (a,c) and European aspen (Populus tremula) (b,d) reflectance, transmittance, and albedo spectra. The color denotes time of measurement (last day if the measurements were obtained within two days). View larger in new window/tab.

7

Fig. 7. Differences in mean reflectance (a,b) and transmittance (c,d) of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) needles between June and September. Difference was calculated as (mean in September – mean in June), separately for current year and previous year needles.