Figure 1.
Sampling sites across Switzerland. Overall, 74 springs were sampled on the Swiss Plateau, and in the Alpine foothills and alpine zones. The sites cover an elevation gradient from 491 to 2482 m above sea level (a.s.l.). Squares overlap when spring sites are located in close proximity. The axes refer to the Swiss coordinate system (Swiss grid).
Figure 1.
Sampling sites across Switzerland. Overall, 74 springs were sampled on the Swiss Plateau, and in the Alpine foothills and alpine zones. The sites cover an elevation gradient from 491 to 2482 m above sea level (a.s.l.). Squares overlap when spring sites are located in close proximity. The axes refer to the Swiss coordinate system (Swiss grid).
Figure 2.
Bar charts showing the total number of species in the respective frequency classes on the different substrates: (A) stones; (C) surface sediment; (E) bryophytes; (G) filamentous green-algae; and (I) leaf litter. Box plots show the distribution of percentages per sampling site for each frequency class on the different habitats: (B) stones; (D) surface sediment; (F) bryophytes; (H) filamentous green-algae; and (J) leaf litter. The boundary of the box shows the 25th and 75th percentile, the line within the box shows the median, and the whiskers the maxima and minima. Frequency classes refer to the abundance in the DI-CH dataset. NS = not found in the DI-CH, VR = very rare (<2%), RA = rare (2–5%), MF = moderately frequent (5–20%), FR = frequent (20–50%), VF = very frequent (>50%).
Figure 2.
Bar charts showing the total number of species in the respective frequency classes on the different substrates: (A) stones; (C) surface sediment; (E) bryophytes; (G) filamentous green-algae; and (I) leaf litter. Box plots show the distribution of percentages per sampling site for each frequency class on the different habitats: (B) stones; (D) surface sediment; (F) bryophytes; (H) filamentous green-algae; and (J) leaf litter. The boundary of the box shows the 25th and 75th percentile, the line within the box shows the median, and the whiskers the maxima and minima. Frequency classes refer to the abundance in the DI-CH dataset. NS = not found in the DI-CH, VR = very rare (<2%), RA = rare (2–5%), MF = moderately frequent (5–20%), FR = frequent (20–50%), VF = very frequent (>50%).
Figure 3.
Biodiversity variables and elevation in relation to the Spring Alteration Degree (SAD) for samples taken from stones. (A) Species rareness weighting; (B) species richness; and (C) elevation of the springs. There is a significant negative association between species rareness weighting and SAD (F(3, 43) = 8.4, p = 0.006; τ(47) = −0.34, p = 0.004). No difference was found between number of species per spring and SAD (F(3, 43) = 1.48, p = 0.231; τ(47) = −0.19, p = 0.101). The SAD decreased significantly with elevation (m a.s.l.) (F(3, 43) = 6.8, p = 0.001; τ(47) = −0.44, p < 0.001). Red List status proportions in relation to the SAD on the substrate stone (N = 47); (D) Abundance of species with a threat status (RL) on the Red List; (E) Per cent abundance of species that are considered as not threatened (NT) on the Red List; (F) Per cent abundance of species with a not specified threat status (NS). The boundary of the box shows the 25th and 75th percentile, the line within the box shows the median, and the whiskers the maxima and minima.
Figure 3.
Biodiversity variables and elevation in relation to the Spring Alteration Degree (SAD) for samples taken from stones. (A) Species rareness weighting; (B) species richness; and (C) elevation of the springs. There is a significant negative association between species rareness weighting and SAD (F(3, 43) = 8.4, p = 0.006; τ(47) = −0.34, p = 0.004). No difference was found between number of species per spring and SAD (F(3, 43) = 1.48, p = 0.231; τ(47) = −0.19, p = 0.101). The SAD decreased significantly with elevation (m a.s.l.) (F(3, 43) = 6.8, p = 0.001; τ(47) = −0.44, p < 0.001). Red List status proportions in relation to the SAD on the substrate stone (N = 47); (D) Abundance of species with a threat status (RL) on the Red List; (E) Per cent abundance of species that are considered as not threatened (NT) on the Red List; (F) Per cent abundance of species with a not specified threat status (NS). The boundary of the box shows the 25th and 75th percentile, the line within the box shows the median, and the whiskers the maxima and minima.

Figure 4.
Percentages of species belonging to the respective DI-CH frequency classes in relation to the SAD on the substrate stone. NS = not found in the DI-CH, VR = very rare (<2%), RA = rare (2–5%), MF = moderately frequent (5–20%), FR = frequent (20–50%), VF = very frequent (>50%). The boundary of the box shows the 25th and 75th percentile, the line within the box shows the median, and the whiskers the maxima and minima.
Figure 4.
Percentages of species belonging to the respective DI-CH frequency classes in relation to the SAD on the substrate stone. NS = not found in the DI-CH, VR = very rare (<2%), RA = rare (2–5%), MF = moderately frequent (5–20%), FR = frequent (20–50%), VF = very frequent (>50%). The boundary of the box shows the 25th and 75th percentile, the line within the box shows the median, and the whiskers the maxima and minima.
Table 1.
Threat categories and frequency classes of the diatom species found in the different data sets (stones, all substrates per spring, and DI-CH). Coding for Red List status of species follows Lange-Bertalot (1996). Frequency classes refer to the abundancy in the DI-CH dataset. NS = not found in the DI-CH, VR = very rare (<2%), RA = rare (2–5%), MF = moderately frequent (5–20%), FR = frequent (20–50%), VF = very frequent (>50%).
Table 1.
Threat categories and frequency classes of the diatom species found in the different data sets (stones, all substrates per spring, and DI-CH). Coding for Red List status of species follows Lange-Bertalot (1996). Frequency classes refer to the abundancy in the DI-CH dataset. NS = not found in the DI-CH, VR = very rare (<2%), RA = rare (2–5%), MF = moderately frequent (5–20%), FR = frequent (20–50%), VF = very frequent (>50%).
| | Stones | Springs | DI-CH |
---|
No of datasets (n) | 47 | 175 | 6008 |
No of recorded taxa | 346 | 540 | 903 |
Average number of species per sample | 33 | 55 | 26 |
Red List of endangered species (%) | RL (=threatened) | 35.3 | 33.93 | 39.8 |
NT (=not threatened) | 33.5 | 32.74 | 41.4 |
NS (=not specified) | 31.2 | 33.33 | 18.8 |
0 = extinct | 0 | 0 | 0 |
1 = close to extinction | 0 | 0 | 0.5 |
2 = critically endangered | 1.2 | 1.2 | 2.1 |
3 = endangered | 10.4 | 10.1 | 9.2 |
G = probably endangered | 10.1 | 9.9 | 7 |
R = very rare | 4.3 | 4 | 9.5 |
V = nearly threatened | 9.2 | 8.7 | 11.5 |
* = not threatened | 18.8 | 17.5 | 21.3 |
** = not threatened | 14.7 | 15.3 | 20.2 |
not specified | 31.2 | 33.3 | 18.8 |
DI-CH (%) | not specified | 31.5 | 36.7 | 0 |
very rare | 46.2 | 43.3 | 76.7 |
rare | 6.4 | 6.2 | 7.4 |
moderately frequent | 7.5 | 6.7 | 9 |
frequent | 5.8 | 5.2 | 5.7 |
very frequent | 2.6 | 2 | 1.2 |
Table 2.
Species richness, frequency-class proportions, and Red List status per substrate. Sall = all substrates accumulated, Ssto = stones, Ssed = sediment, Sbry = bryophytes, Sepi = filamentous green algae, and Slea = leaf litter. SP = number of unidentified species, but identification to genus level was possible. NS = not found in the DI-CH, VR = very rare (<2%), RA = rare (2–5%), MF = moderately frequent (5–20%), FR = frequent (20–50%), and VF = very frequent (>50%). Red List status refers to the threat status of the diatom Red List (Lange-Bertalot 1996): RL = species with threat status, NT = species not threatened, NS = threat status not specified. Species and SP are counted species numbers, frequency class DI-CH and Red List status are percentages.
Table 2.
Species richness, frequency-class proportions, and Red List status per substrate. Sall = all substrates accumulated, Ssto = stones, Ssed = sediment, Sbry = bryophytes, Sepi = filamentous green algae, and Slea = leaf litter. SP = number of unidentified species, but identification to genus level was possible. NS = not found in the DI-CH, VR = very rare (<2%), RA = rare (2–5%), MF = moderately frequent (5–20%), FR = frequent (20–50%), and VF = very frequent (>50%). Red List status refers to the threat status of the diatom Red List (Lange-Bertalot 1996): RL = species with threat status, NT = species not threatened, NS = threat status not specified. Species and SP are counted species numbers, frequency class DI-CH and Red List status are percentages.
| | | Frequency Class DI-CH (%) | Red List Status (%) |
---|
Species | SP | NS | VR | RA | MF | FR | VF | RL | NT | NS |
---|
Sall | 540 | 36 | 36.7 | 43.3 | 6.2 | 6.7 | 5.2 | 2 | 33.9 | 32.7 | 33.3 |
Sstone | 369 | 23 | 31.5 | 46.2 | 6.4 | 7.5 | 5.8 | 2.6 | 35.3 | 33.5 | 31.2 |
Ssediment | 382 | 21 | 31.9 | 47.1 | 6.1 | 6.6 | 5.5 | 2.8 | 36 | 34.9 | 29.1 |
Sbryophytes | 389 | 21 | 32.9 | 46.5 | 6 | 6.5 | 6 | 2.2 | 34.8 | 33.7 | 31.5 |
Sfilamentous green-algae | 237 | 12 | 29.3 | 44.9 | 5.3 | 8 | 8.9 | 3.6 | 33.8 | 37.8 | 28.4 |
Sleaf litter | 134 | 12 | 23 | 47.5 | 7.4 | 9 | 7.4 | 5.7 | 32.8 | 35.2 | 32 |
Table 3.
Results of the ANOVA and correlation test between the single variables for each substrate. One-way analysis of variance (ANOVA) shows F- and p-values (level of significance = 5%). Kendall’s rank correlation coefficient shows the coefficent τ and the significance (p) depending on the SAD. Highlighted in bold are significant results (p < 0.05), and a grey background indicates a significant difference of the means by ANOVA and significant correlation by Tau-test. Frequency classes refer to the occurrence of species in the DI-CH (regional species pool): VR = very rare, RA = rare, MF = moderately frequent, FR = frequent, VF = very frequent, NS = not found in the DI-CH. Red List status refers to the German diatom Red List (Lange-Bertalot 1996): RL = species are considered as threatened, NT = species are considered as not threatened, NS = threat status not specified.
Table 3.
Results of the ANOVA and correlation test between the single variables for each substrate. One-way analysis of variance (ANOVA) shows F- and p-values (level of significance = 5%). Kendall’s rank correlation coefficient shows the coefficent τ and the significance (p) depending on the SAD. Highlighted in bold are significant results (p < 0.05), and a grey background indicates a significant difference of the means by ANOVA and significant correlation by Tau-test. Frequency classes refer to the occurrence of species in the DI-CH (regional species pool): VR = very rare, RA = rare, MF = moderately frequent, FR = frequent, VF = very frequent, NS = not found in the DI-CH. Red List status refers to the German diatom Red List (Lange-Bertalot 1996): RL = species are considered as threatened, NT = species are considered as not threatened, NS = threat status not specified.
Substrate | Analysis | | Species Rareness Weighting | Species Richness | Frequency Classes | Red List Status |
---|
VR | RA | MF | FR | VF | NS | RL | NT | NS |
---|
Stone | ANOVA | F(3, 43) | 2.96 | 1.48 | 2.35 | 1.51 | 0.39 | 2.49 | 3.05 | 1.48 | 5.60 | 3.09 | 2.17 |
p | 0.042 | 0.231 | 0.085 | 0.225 | 0.758 | 0.073 | 0.039 | 0.232 | 0.002 | 0.037 | 0.105 |
Kendall τ | τ(47) | −0.34 | −0.19 | −0.27 | 0.16 | 0.08 | 0.28 | 0.30 | −0.19 | −0.34 | 0.11 | 0.28 |
p | 0.004 | 0.101 | 0.022 | 0.160 | 0.467 | 0.015 | 0.010 | 0.104 | 0.003 | 0.327 | 0.015 |
Sediment | ANOVA | F(3, 41) | 3.37 | 2.39 | 2.78 | 1.12 | 2.28 | 1.75 | 3.62 | 1.59 | 4.57 | 1.04 | 5.06 |
p | 0.027 | 0.083 | 0.053 | 0.350 | 0.093 | 0.171 | 0.021 | 0.206 | 0.007 | 0.386 | 0.004 |
Kendall τ | τ(45) | −0.30 | −0.24 | −0.29 | 0.15 | 0.15 | 0.24 | 0.35 | −0.14 | −0.39 | 0.17 | 0.27 |
p | 0.012 | 0.043 | 0.013 | 0.214 | 0.214 | 0.042 | 0.003 | 0.223 | 0.001 | 0.152 | 0.022 |
Bryophytes | ANOVA | F(2, 54) | 3.26 | 0.51 | 5.10 | 1.46 | 0.78 | 2.77 | 6.35 | 0.05 | 3.52 | 0.83 | 3.16 |
p | 0.046 | 0.605 | 0.009 | 0.241 | 0.465 | 0.071 | 0.003 | 0.948 | 0.037 | 0.444 | 0.050 |
Kendall τ | τ(57) | −0.19 | −0.09 | −0.30 | 0.03 | −0.03 | 0.21 | 0.38 | 0.00 | −0.19 | 0.11 | 0.19 |
p | 0.080 | 0.379 | 0.005 | 0.797 | 0.750 | 0.054 | 0.000 | 0.975 | 0.075 | 0.319 | 0.077 |
Filamentous green-algae | ANOVA | F(3, 13) | 1.03 | 0.65 | 4.59 | 0.52 | 0.80 | 2.81 | 1.46 | 0.52 | 4.43 | 2.35 | 0.46 |
p | 0.412 | 0.595 | 0.021 | 0.667 | 0.516 | 0.081 | 0.271 | 0.674 | 0.024 | 0.120 | 0.716 |
Kendall τ | τ(17) | −0.35 | −0.06 | −0.34 | 0.00 | 0.06 | 0.43 | 0.30 | −0.38 | −0.50 | 0.45 | 0.16 |
p | 0.081 | 0.754 | 0.088 | 1.000 | 0.754 | 0.032 | 0.128 | 0.060 | 0.012 | 0.023 | 0.420 |
Leaf litter | ANOVA | F(2, 6) | 0.23 | 1.75 | 0.89 | 0.00 | 0.33 | 0.83 | 0.33 | 0.06 | 0.26 | 0.19 | 1.55 |
p | 0.805 | 0.251 | 0.458 | 0.999 | 0.734 | 0.481 | 0.732 | 0.947 | 0.781 | 0.836 | 0.287 |
Kendall τ | τ(9) | 0.03 | 0.36 | −0.24 | 0.03 | −0.21 | 0.17 | 0.24 | −0.03 | 0.17 | 0.07 | −0.49 |
p | 0.906 | 0.233 | 0.408 | 0.906 | 0.477 | 0.555 | 0.408 | 0.906 | 0.555 | 0.812 | 0.097 |