On the Ecology of Mountainous Forests in a Changing Climate: A ...
On the Ecology of Mountainous Forests in a Changing Climate: A ...
On the Ecology of Mountainous Forests in a Changing Climate: A ...
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80 Chapter 3<br />
80<br />
60<br />
40<br />
D (°C*d)<br />
20<br />
0<br />
T m,y,l ≥ 15.5: D = -31.8 + 2.377·T m,y,l r 2 = 0.77<br />
-20 5.5 ≤ T m,y,l ≤ 15.5: D = 187.2·10 -0.0908·T m,y,l r 2 = 0.99<br />
T m,y,l ≤ 5.5: D = 8.52·10 0.165·T m,y,l r 2 = 0.98<br />
-40<br />
-10 0 10 20 30<br />
T<br />
m,y,l<br />
(°C)<br />
Fig. 3.9: Average difference (D) <strong>of</strong> estimated monthly degree-days between <strong>the</strong> more<br />
precise estimation method by Allen (1976) and <strong>the</strong> formula used <strong>in</strong> conventional forest gap<br />
models (Botk<strong>in</strong> et al. 1972a,b) as a function <strong>of</strong> monthly mean temperature (T m,y,l ). The data<br />
are from <strong>the</strong> sites Bern, Bever, and Locarno.<br />
Next, <strong>the</strong> monthly degree-day sums were recalculated tak<strong>in</strong>g <strong>in</strong>to account <strong>the</strong> error terms<br />
given <strong>in</strong> Fig. 3.9. A verification test for <strong>the</strong> site Bern and a validation test for <strong>the</strong> site<br />
Basel are shown <strong>in</strong> Fig. 3.10. It can be concluded that <strong>the</strong> correction formula provides an<br />
accurate estimate <strong>of</strong> Allen's monthly degree-day sums.<br />
F<strong>in</strong>ally, <strong>the</strong> effects <strong>of</strong> <strong>the</strong> correction formula on <strong>the</strong> annual sum <strong>of</strong> degree-days were evaluated<br />
at all six sites (Fig. 3.11). The new formula provides estimates <strong>of</strong> <strong>the</strong> annual sum<br />
500<br />
2<br />
y = 2.86 + 0.993x r = 0.996<br />
600<br />
2<br />
y = - 1.45 + 0.969x r = 0.992<br />
ForClim degree-days<br />
400<br />
300<br />
200<br />
100<br />
500<br />
400<br />
300<br />
200<br />
100<br />
0<br />
0<br />
100 200 300 400<br />
Allen's degree-days<br />
500<br />
0<br />
0<br />
100 200 300 400 500<br />
Allen's degree-days<br />
600<br />
Fig. 3.10: Performance <strong>of</strong> <strong>the</strong> empirical correction formula for estimat<strong>in</strong>g <strong>the</strong> monthly<br />
sum <strong>of</strong> degree-days from monthly mean temperature. Left: Verification test for <strong>the</strong> site<br />
Bern. Right: Validation test for <strong>the</strong> site Basel.