From: Variables related to nitrogen deposition improve defoliation models for European forests
Variable | Description | PLS regression model | Range of values | ||
---|---|---|---|---|---|
Beech (n = 20) | Norway spruce (n = 33) | Scots pine (n = 18) | |||
Response | |||||
F 25 | Mean percentage of trees of the selected species with defoliation > 25 % | All models | 0–43.3 % | 0–72.0 % | 0–32.7 % |
Predictors | |||||
Null model | |||||
Tree density | Trees per hectare | All models | 161–1322 | 247–1060 | 254–1780 |
Latitude | All models | 38°25′–55°57′ N | 45°45′–67°59′ N | 46°17′–66°21′ N | |
Longitude | All models | 0°39′ W–16°10′ E | 1°48′ E–29°19′ E | 7°42′ E–29°20′ E | |
Altitude | All models | 25–1525 m a.s.l. | 25–1775 m a.s.l. | 25–475 m a.s.l. | |
Pr | Annual precipitation amount (mm) | All models | 641–2038 mm year−1 | 543–2845 mm year−1 | 577–1551 mm year−1 |
SummerPr | Percentage of precipitation during the growing season | All models | 32.7–69.9 % | 45.6–82.2 % | 48.7–80.7 % |
BADoAP | Mean reported BADoAP on foliage of trees of the selected species | Reference + BADoAP | 0–2.0 | 0–2.7 | 0–0.7 |
Reference + BADoAP + Nthrdep | |||||
Soil | |||||
Soil_pH | pH (CaCl2) of the mineral top soil, pH unit | Reference + soil | 3.10–6.95 | 2.91–4.68 | 2.93–4.33 |
BCE | Exchangeable Base Cations in mineral top soil | Reference + soil | 0.57–51.2 cmol+ kg−1 | 0.24–7.78 cmol+ kg−1 | 0.17–2.29 cmol+ kg−1 |
C/N | C/N ratio of mineral top soil | Reference + soil | 12.9–22.1 | 14.5–29.8 | 2.8–53.8 |
Tree foliar nutrition | |||||
N/P | N ratio to P, Ca, Mg, K concentrations in foliage (current year for evergreen species) | Reference + foliar | 16.2–30.1 | 6.0–21.8 | 8.4–15.2 |
N/Ca | Reference + foliar | 1.8–8.1 | 2.1–11.6 | 2.9–8.3 | |
N/Mg | Reference + foliar | 11.2–38.7 | 7.7–25.1 | 11.0–30.4 | |
N/K | Reference + foliar | 2.6–4.9 | 1.6–30.4 | 1.5–4.1 | |
N deposition | |||||
Nthrdep | Throughfall N deposition | Reference + NNthrdep Reference + BADoAP + NNthr dep | 10.4–24.8 kg ha−1 year−1 | 1.5–32.3 kg ha−1 year−1 | 2.1–26.7 kg ha−1 year−1 |