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Report - ICP Forests

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78 3. Intensive Monitoring<br />

Figure 3.4.4-1 is the biplot of the model of Table 3.4.4-2. There seem to be two main gradients:<br />

one that is determined by soil chemistry and runs from acid and nutrient-poor to neutral and<br />

nutrient-rich; and an other that is determined by tree species, mainly the contrast coniferous vs.<br />

deciduous. These ecological gradients are at an angle of c. 45 o with the CCA axes (which is<br />

usual if the two gradients are more or less equally important). The third and fourth axis mainly<br />

seem to separate the mediterranean plots from all other plots. There is no single axis that clearly<br />

represents the effect of N deposition; this is also apparent from the canonical coefficients and<br />

their t-values (not shown). Therefore an extra analysis was run where the effect of N deposition<br />

was forced through the first axis. This is achieved by declaring N deposition as the only<br />

environmental variable and moving all other variables with a significant effect in Table 3.4.4-2<br />

to the covariables. The resulting biplot is difficult to interpret and not shown, however the<br />

sample scores on this axis are just significantly correlated with the mean Ellenberg N values (R<br />

= 0.19, N = 111, P = 0.045). The effect of N deposition in the model of Table 3.4.4-2 is<br />

therefore not considered as a spurious effect but most probably represents a real ecological<br />

effect.<br />

A<br />

B<br />

-3 3<br />

Axis 2<br />

Querccer<br />

Mespiger<br />

Fallocon<br />

Prunuspi<br />

Castasat<br />

Cratalae<br />

Quercpet SorbutorLathyven<br />

Alliapet<br />

Ranunaur<br />

Carpibet<br />

Pinussyl<br />

Cratamon<br />

Pinusstr<br />

Stellhol<br />

Ilex aqu<br />

Prunuser Quercrob<br />

Prunuavi<br />

Betulpen<br />

Acer cam<br />

Potenste<br />

Corylave<br />

Geum urb<br />

Anemonem<br />

Sorbuauc<br />

Dryopcar<br />

Rosa can<br />

Rosa arv<br />

Piceaabi<br />

Rubusida Dryopfil<br />

Fagussyl<br />

Oxaliace<br />

Dryopdil<br />

Rubusfru Acer pla<br />

Fragaves<br />

Athyrfil<br />

Abiesalb<br />

Impatnol<br />

Pseudmen<br />

Geranrob<br />

Hepatnob<br />

Viciasep<br />

Acer pse Mercuper<br />

Ulmusgla<br />

Lathyver<br />

Silendio<br />

Lathypra<br />

Equisarv<br />

Cardafle Chrysalt<br />

Stellnem Cardaama<br />

Ribesalp<br />

Aruncdio<br />

Cardahep Cardapen<br />

Rosa pen<br />

Axis 1<br />

Ranunfic<br />

-1.0 1.0<br />

conf_Tr<br />

Axis 2<br />

Qurp_Tr<br />

AtlS_Cli<br />

AtlN_Cli<br />

Pins_Tr<br />

Lat<br />

Ndep00_EMEP<br />

QurM_Tr<br />

deci_Tr<br />

Age<br />

Lon<br />

Bor_Cli<br />

Ca_org pH_org<br />

P_org<br />

N/C_org<br />

K_org<br />

Pice_Tr<br />

Fags_Tr<br />

CEC_min<br />

Axis 1<br />

-2 3<br />

-0.6 1.0

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