Geoscience Reference
In-Depth Information
Table 12.2
Values of the Spearman's
correlation coefficient between
environmental parameters of segment
characterization (see Table 12.1 for
abbreviations) and percentage values
of coverage of bedrock by moss and
liverwort species (Cob M
Parameter
Cob M
+
L
S
HB
Cob Macro
EROS
−
0.301
TMARm
−
0.314
COND
−
0.303
POLU
−
0.465
−
0.379
+
L);
bryophyte (mosses and liverworts)
species richness (S); Brillouin Index
for the stream segment (HB); Total
coverage of macrophytes
(Cob Macro). Only significant
Spearman correlations greater than
0.3 and with p
0.001 are shown.
LUMI
−
0.393
−
0.378
TEMP
−
0.310
LARG
−
0.320
HETC
0.373
0.346
0.350
DECL
0.310
HETS
0.301
FONV
0.321
CMAR
0.377
0.370
Discussion
are between 0.897 and 0.978, it suggests that
floristic composition is influenced by multiple
gradients. The first axis is related mainly to climatic
variables (runoff, precipitation and temperature),
altitude, light incidence, water column features
(e.g. the presence of dams; channel width)
and especially to water quality and soil acidity
parameters (r
0.3) (Figure 12.3; Table 12.4).
The second axis has weaker correlations with the
environmental variables.
Bryophyte groups, species richness
and diversity
Bryophytes associated with water are generally
positively associated with diverse, steep, shaded
watercourses in natural landscapes; they become
less prominent with increasing water pollution,
temperature and incident light and also in
slower-flowing rivers where higher plants become
187 segments
Cinclidotus fontinaloides
Racomitrium aciculare
Leptodyctium riparium
Thamnobryum alopecurum
Chiloscyphus polyanthus
Brachythecium rivulare
Racomitrium lamprocarpum
Polytrichum commune
Scapania undulata
Hyocomium armoricum
Fontinalis squamosa
Fissidens polyphyllus
Platyhypnidium lusitanicum
Bryum capillare
Ceratodon purpureus
Bryum alpinum
A
(8 segments)
B
(11 segments)
C
(89 segments)
D
(62 segments)
E
(6 segments)
F
(11 segments)
Figure 12.2
Summary dendrogram derived from TWINSPAN classification of the stream segments (number of
segments in each group; for each dichotomy, the species names used to divide the TWINSPAN groups are indicated;
TWINSPAN group name codes A to F shown in bold).
