Figure 1.
The location of the research area in eastern Ukraine and the spatial distribution of sample plots
Figure 2.
Representative fragments of two SPs selected for model validation (left: SP 1; right: SP 2); photographs were taken in 2021. SPs: sample plots
Figure 3.
Block diagram of the UFB model (Kozak et al. 2023), the full term of DBH given in the figure: diameter at breast height
Figure 4.
Percentage of drying of assimilation apparatus of Scots pine as depicted in the UFB model: a) 0%, b) 100%
Figure 5.
Percentage distribution of the NDVI index in the Luhansk region, as obtained for two dates: 06.27.2020 (dark green) and 07.06.2024 (light green)
Table 1.
Statistical results of model validation
| SP No. | R2 | RMSE, m | ME, m | BIAS |
|---|---|---|---|---|
| 1 | 0.9579 | 0.0264 | 0.9580 | 0.0013 |
| 2 | 0.9601 | 0.0305 | 0.9392 | 0.0164 |
Figure 6.
Graphical visualization of statistical calculations: linear regressions for modeled versus observed tree height: A – for SP 1, C – for SP 2; residual plots for tree height associated with the linear models in the preceding graph: B – for SP 1, D – for SP 2
Table 2.
Climatic scenarios and major simulation results for two sample plots (SP 1 and SP2) differing in terms of the initial seedling density
| Sample plot | Initial (in 2014) number of planted trees, ind./ha | Climatic scenario | Annual degree-day, °C | Precipitation, mm | Modeled No. of trees, ind./ha | No. of dead trees | ||
|---|---|---|---|---|---|---|---|---|
| 2014 | 2030 | ind./ha | % | |||||
| SP 1 | 10,000 | Control | 1750 | 450 | 10,000 | 6756 | 3244 | 32.4 |
| Warm-dry | 1975 | 350 | 10,000 | 2161 | 7839 | 78.4 | ||
| SP 2 | 3,333 | Control | 1750 | 450 | 3,333 | 2597 | 736 | 22.1 |
| Warm-dry | 1975 | 350 | 3,333 | 2342 | 991 | 29.7 | ||
Figure 7.
Visualization of Scots pine seedlings in simulations performed by the UFB model: A – SP 1 in 1 year; B – SP 2 in 1 year; C – SP 1 in the year 2030 (control variant); D – SP 2 in the year 2030 (control variant); E – SP 1 in the year 2030 (warm-dry variant); F – SP 2 in the year 2030 (warm-dry variant); size of the plots 25 × 25 m