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 ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
132 Chapter 5<br />
where ∆T m is <strong>the</strong> average deviation <strong>of</strong> <strong>the</strong> monthly mean temperature from <strong>the</strong> annual<br />
mean temperature (Fig. 5.2), and <strong>the</strong> equation is scaled so that at <strong>the</strong> average precipitation<br />
sum <strong>of</strong> all sites (P l<br />
* = 1180 mm/yr) <strong>the</strong>ir average temperature amplitude is reached<br />
(A l<br />
* = ∆T Jul – ∆T Jan = 18.4 °C, Fig. 5.2). The monthly precipitation sum and <strong>the</strong><br />
standard deviations <strong>of</strong> temperature and precipitation are calculated from <strong>the</strong> data presented<br />
<strong>in</strong> Fig. 5.2.<br />
Simulation studies were conducted with <strong>the</strong> FORECE model and two FORCLIM variants,<br />
FORCLIM-E/P and -E/P/S. The annual mean temperature was varied from -2 to 13 °C,<br />
and one simulation experiment was performed every 0.5 °C. The annual precipitation<br />
sum was varied from 400 to 2000 mm/yr, with one experiment every 100 mm/yr, yield<strong>in</strong>g<br />
a total <strong>of</strong> 31·17 = 527 simulation experiments. For each <strong>of</strong> <strong>the</strong>se po<strong>in</strong>ts <strong>in</strong> <strong>the</strong> (T,P)<br />
space, <strong>the</strong> equilibrium species composition was estimated us<strong>in</strong>g n = 200 po<strong>in</strong>ts and an<br />
<strong>in</strong>terval (∆t) <strong>of</strong> 150 years, discard<strong>in</strong>g <strong>the</strong> first 1000 years (cf. section 4.4).<br />
The field capacity parameter (kFC) was assumed to be 30 cm throughout <strong>the</strong> (T,P) space<br />
and <strong>in</strong> all models. For <strong>the</strong> model variant FORCLIM-E/P, available nitrogen was assumed<br />
to be 100 kg/ha throughout <strong>the</strong> (T,P) space. For both FORCLIM variants <strong>the</strong> cross-correlation<br />
coefficients were assumed to be -0.6 <strong>in</strong> summer (April–Sept.), and 0 <strong>in</strong> w<strong>in</strong>ter<br />
(Oct.–March). For FORECE, <strong>the</strong> additional site parameters were taken from Tab. 2.2<br />
(Bern), and <strong>the</strong> 200 samples with ∆t = 150 years were extracted from <strong>the</strong> default output<br />
file. The simulation studies with <strong>the</strong> FORCLIM models were executed on Mac<strong>in</strong>tosh computers;<br />
because simulation studies with FORECE require much more comput<strong>in</strong>g time, <strong>the</strong>y<br />
had to be performed on a Sun SS630 workstation and still took more than three weeks.<br />
Data process<strong>in</strong>g for creat<strong>in</strong>g three-dimensional plots was done with <strong>the</strong> s<strong>of</strong>tware Micros<strong>of</strong>t<br />
EXCEL V4.0, and unsmoo<strong>the</strong>d contour plots were drawn us<strong>in</strong>g MATHEMATICA<br />
V2.03 on an Apple Mac<strong>in</strong>tosh computer model Quadra 700.<br />
5.3.2 Results & discussion<br />
First, let us exam<strong>in</strong>e <strong>the</strong> pattern <strong>of</strong> total aboveground biomass simuated by <strong>the</strong> three<br />
models (Fig. 5.3): The most strik<strong>in</strong>g feature is that FORECE simulates <strong>the</strong> highest biomass<br />
close to <strong>the</strong> alp<strong>in</strong>e treel<strong>in</strong>e, whereas both FORCLIM variants predict a steady <strong>in</strong>crease<br />
with <strong>in</strong>creas<strong>in</strong>g temperature and precipitation. It may be argued that <strong>the</strong> assumption<br />
<strong>in</strong> FORECE that <strong>the</strong> SOILQ parameter is constant throughout <strong>the</strong> (T,P) space is unreal-