Table 3. Results of principal component analysis using abiotic, present-day and historical sets of variables.
| OLD PATCHES | ||
|---|---|---|
| Abiotic variables | PC1 | PC2 |
| TWI | 0.703 | 0.081 |
| slope | -0.702 | -0.082 |
| elevation | 0.086 | -0.701 |
| Pdsi_June | 0.077 | -0.703 |
| Proportion of variance (%) | 41.76 | 30.59 |
| Cumulative Proportion (%) | 41.76 | 72.35 |
| Present-day variables | PC1 | PC2 |
| Log A | -0.707 | -0.707 |
| I2000 | 0.707 | -0.707 |
| Proportion of variance (%) | 66.88 | 33.13 |
| Cumulative Proportion (%) | 66.88 | 100 |
| Historical variables | PC1 | PC2 |
| Age | -0.451 | 0.081 |
| I1843 | 0.504 | -0.308 |
| I1980 | 0.479 | 0.415 |
| A1843 | -0.357 | 0.663 |
| A1980 | -0.429 | -0.534 |
| Proportion of variance (%) | 40.65 | 23.69 |
| Cumulative Proportion (%) | 40.65 | 64.34 |
TWI (topographic wetness index), PDSI_June (potential direct solar irradiation June), LogA (logarithm patch area), IA (Isolation based on the area of the surrounding dry grasslands in 2000), Age (number of years of continuous existence), I1843 (Isolation based on the area of the surrounding potential grassland habitats in 1843), I1980 (Isolation based on the area of the surrounding potential grassland habitats in 1980), A1843 (Area of the patch calculated as percentage of its present-day area covered by potential grassland habitats in 1843), A1980 (Area of the patch calculated as percentage of its present-day area covered by potential grassland habitats in 1980).