Open Access

Development of a footprint description tool utilizing SMEAR Estonia eddy-covariance data and footprint modelling in combination with remote sensed forest species and land cover data

Joonas Kollo
Joonas Kollo
, 
Allar Padari
Allar Padari
, 
Alisa Krasnova
Alisa Krasnova
, 
Ahto Kangur
Ahto Kangur
 and 
Steffen M. Noe
Steffen M. Noe
   | Apr 13, 2024
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Article Category: Research paper
Published Online: Apr 13, 2024
Page range: 90 - 104
DOI: https://doi.org/10.2478/fsmu-2023-0014
Keywords
© 2023 Joonas Kollo et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1.

Scheme of the workflow to reach from flux tower raw data to the FFP description product.
Scheme of the workflow to reach from flux tower raw data to the FFP description product.

Figure 2.

A representation of the cumulative FFP contours at the 10%, 50%, 60%, 70%, 80% and 90% contours of source weights for each year at the height of 70 m.
A representation of the cumulative FFP contours at the 10%, 50%, 60%, 70%, 80% and 90% contours of source weights for each year at the height of 70 m.

Figure 3.

The contours of the FFP area for the years 2015–2020. It is visible that the change in the FFP area differs year to year and that these changes introduce also changes in the fraction of the land cover elements (e.g. clear-cut, road) or tree species. Coloured areas stand for clear-cuts. Blue, dark blue and purple colours show areas that were clear-cut in 2018, 2019 and 2020, respectively. The red sign in the middle indicates the location of the flux tower.
The contours of the FFP area for the years 2015–2020. It is visible that the change in the FFP area differs year to year and that these changes introduce also changes in the fraction of the land cover elements (e.g. clear-cut, road) or tree species. Coloured areas stand for clear-cuts. Blue, dark blue and purple colours show areas that were clear-cut in 2018, 2019 and 2020, respectively. The red sign in the middle indicates the location of the flux tower.

Figure 4.

Heterogeneity in the annual wind direction and speed (m s−1) measured at the SMEAR Estonia atmospheric tower at 30 m. The dominant wind directions ranged from the west to the south in 2015 to 2017 and in the more recent years from southwest to southeast. The darker colour on the figure denotes a higher density in wind direction and speed which means a higher contribution from those directions to the overall FFP.
Heterogeneity in the annual wind direction and speed (m s−1) measured at the SMEAR Estonia atmospheric tower at 30 m. The dominant wind directions ranged from the west to the south in 2015 to 2017 and in the more recent years from southwest to southeast. The darker colour on the figure denotes a higher density in wind direction and speed which means a higher contribution from those directions to the overall FFP.

Figure 5.

The contours of the FFP area in 2015–2020. It is visible that the change in the FFP area differs year to year and that these changes introduce also changes in the fraction of the land cover elements (e.g. clear-cut, road, forest area) or tree species. Different colours and filling patterns mark thinning and clear-cut areas in different years.
The contours of the FFP area in 2015–2020. It is visible that the change in the FFP area differs year to year and that these changes introduce also changes in the fraction of the land cover elements (e.g. clear-cut, road, forest area) or tree species. Different colours and filling patterns mark thinning and clear-cut areas in different years.

Figure 6.

Heterogeneity in the annual wind direction and speed (m s−1) measured at the SMEAR Estonia atmospheric tower at 70 m. The dominant wind directions ranged from the west to the south in 2015 to 2017 and in the more recent years from the southwest to the southeast. The darker colour on the figure denotes a higher density in wind direction and speed, which means a higher contribution from those directions to the overall FFP.
Heterogeneity in the annual wind direction and speed (m s−1) measured at the SMEAR Estonia atmospheric tower at 70 m. The dominant wind directions ranged from the west to the south in 2015 to 2017 and in the more recent years from the southwest to the southeast. The darker colour on the figure denotes a higher density in wind direction and speed, which means a higher contribution from those directions to the overall FFP.

Basic input parameters and definitions for the Kljun et al. (2004) FFP model.

Input Description
zm measurement height above ground (m)
z0 roughness length (m)
d displacement height (m)
u_mean mean wind speed at zm (m/s)
L Obukhov length (m)
sigma_v standard deviation of lateral velocity fluctuations after rotation (m/s)
u* friction velocity (m/s)

Land categories of the FFP area over the period of 2015–2020 at a height of 30 m.

Land type Species Area (ha) Increment (m3/ha/y) Growing stock (m3) % of the FFP
Forest land Alnus incana 0.1 0.5 7.6 0.2
Forest land Alnus glutinosa 0.2 0.8 22.7 0.4
Forest land Populus tremula 4.3 8.9 368.6 6.9
Forest land Betula spp. 6.8 34.1 1179.5 11.1
Forest land Picea abies 15.4 99.6 4234.5 25.0
Forest land Pinus sylvestris 28.2 100.2 8448.0 45.8
Forest land Unknown 2.8
Isle in the forest - 0.4 0.6
Buildings - 0.0 0.0
Electric power lines - 1.4 2.4
Roads - 0.2 0.4
Ditches - 0.6 1.0
Clear area Clear-cut 1.0 1.6
Total - 61.5 100.0
Total forest area - 55.0 89.4

Forest site types in the FFP measured at a height of 30 m.

Forest site type 2015 2016 2017 2018 2019 2020 Average area (ha) % of FFP area Average increment (m3/ha/a) % of FFP area Average stock (m3) % of FFP area
Mineral dump 3.5 3.9 3.6 3.9 3.8 3.5 3.7 6.0
Filipendula 8.4 8.6 9.1 8.8 9.0 8.8 8.8 14.3 35.9 14.7 1560.1 10.9
Oxalis 1.9 2.0 1.8 1.7 1.9 1.6 1.8 2.9 4.6 1.9 282.4 2.0
Oxalis-Myrtillus 1.5 3.2 2.6 2.8 1.9 2.1 2.3 3.8 16.0 6.5 660.0 4.6
Oxalis drained swamp 3.9 6.4 4.0 5.4 4.5 3.9 4.7 7.6 26.2 10.7 925.9 6.5
Myrtillus 22.8 22.9 22.0 22.3 22.8 21.2 22.3 36.3 99.8 40.9 6622.5 46.4
Uliginosum 14.2 13.1 11.7 12.7 12.4 12.2 12.7 20.7 45.9 18.8 2916.4 20.5
Oxycoccus 5.4 5.4 5.3 4.8 5.1 5.0 5.2 8.4 15.6 6.4 1293.5 9.1
Total 61.6 65.4 60.2 62.3 61.4 58.3 61.5 100.0 244.0 100.0 14260.9 100.0

Growing stock (m3/ha) and increment (m3/ha/y) changes during the six-year period.

Characteristic Unit Year
2015 2016 2017 2018 2019 2020
Area ha 2888.86 2891.82 2864.11 2938.29 2914.90 2886.02
Stock in summer m3 605713 603467 592571 618805 607847 610235
Thinning & harvesting m3 8481 10666 5577 9394 5943
Increment m3 9187 9335 9134 9500 9551 9701
Stock in next summer m3 606418 602136 596127 618910 611455
Stock in summer m3/ha 209.67 208.68 206.90 210.60 208.53 211.44
Thinning & harvesting m3/ha 2.94 3.69 1.95 3.20 2.04
Increment m3/ha 3.18 3.23 3.19 3.23 3.28 3.36
Stock in next summer m3/ha 209.92 208.22 208.14 210.64 209.77

Forest site types in the FFP measured at a height of 70 m.

Forest site type 2015 2016 2017 2018 2019 2020 Average area (ha) % of FFP Average increment (m3/ha/a) % of FFP Average stock (m3) % of FFP
Mineral dump 418.0 445.5 397.4 415.5 429.0 406.6 418.7 12.703
Myrtillus 564.2 567.9 553.1 578.1 576.1 554.3 565.6 17.161 848.4 18.0 77460.9 25.4
Vaccinium 36.4 34.1 36.6 36.5 39.3 36.8 36.6 1.111 39.6 0.8 6332.8 2.1
Raised bog 42.9 45.7 36.2 25.3 52.6 18.0 36.8 1.116 19.5 0.4 414.8 0.1
Uliginosum 73.2 75.7 73.3 74.5 75.4 73.6 74.3 2.253 71.9 1.5 9110.2 3.0
Transitional bog 87.0 95.0 85.0 93.0 89.8 85.3 89.2 2.706 63.0 1.3 10211.7 3.3
Filipendula 1233.1 1254.7 1205.3 1296.9 1236.7 1231.0 1242.9 37.711 2024.0 42.9 122544.0 40.1
Oxalis 160.4 133.1 129.4 109.5 129.1 134.1 132.6 4.024 364.6 7.7 12762.4 4.2
Oxalis-Myrtillus 172.0 207.5 198.4 206.6 180.1 222.9 197.9 6.005 488.1 10.3 19911.9 6.5
Oxalis drained swamp 489.7 448.3 517.3 487.7 506.7 499.7 491.6 14.914 759.6 16.1 44217.1 14.5
Aegopodium 7.769 6.710 6.730 5.983 5.995 6.990 6.7 0.203 21.2 0.4 1866.7 0.6
Hepatica 2.982 2.982 2.982 2.982 2.982 2.982 3.0 0.090 21.2 0.4 414.6 0.1
Cladonia 0.280 0.000 0.222 0.000 0.000 0.000 0.1 0.003 0.1 0.0 21.9 0.0
Total 3296.0 100.0 4721.2 100.0 305268.8 100.0

Land categories of the FFP area over the period of 2015–2020 at a height of 70 m.

Land type Species Area (ha) Increment (m3/ha/y) Growing stock (m3) % of FFP
Forest Alnus incana 37.2 186.9 3251.9 1.1
Forest Alnus glutinosa 464.5 1693.0 76381.2 14.1
Forest Populus tremula 242.7 786.6 20652.5 7.4
Forest Betula spp. 1007.9 3449.5 224027.0 30.6
Forest Picea abies 450.0 2205.8 135347.7 13.7
Forest Pinus sylvestris 470.5 1027.0 145716.4 14.3
Forest Other species 0.1 0.1 58.0 0.0
Forest (bog) Pinus sylvestris 40.7 52.5 1004.7 1.2
Forest Clear-cut 183.6 5.6
Bog Without forest 35.5 1.1
Fen Without forest 9.8 0.3
Agricultural land - 120.4 3.7
Clear area - 83.8 2.5
Buildings - 2.3 0.1
Standing water - 3.8 0.1
Isle in the forest - 30.4 0.9
Roads - 37.1 1.1
Watercourse - 40.1 1.2
Yard - 11.8 0.4
Other land - 0.3 0.0
Power lines - 23.5 0.7
Total forest land - 2897.3 87.9
Total area - 3296.0 100.0
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