Corresponding author: Mateusz Rybak (
Academic editor: K. Manoylov
Although many studies have examined the algae associated with various habitats in tree trunks, the diatoms in these environments are still poorly studied. Studies of corticolous algae mainly focus on green algae and cyanobacteria, which are usually immediately visible, while diatoms are mostly overlooked or not reported. During the research, 143 species of diatoms were identified, including two new representatives of the genus
Rybak M, Czarnota P, Noga T (2023) Study of terrestrial diatoms in corticolous assemblages from deciduous trees in Central Europe with descriptions of two new
Despite over a century of study on terrestrial algae (
Many different terms are used to name algal assemblage in their terrestrial environments depending on environmental conditions and available water sources (
Bark surfaces create special microclimatic niches for algae. Thanks to cracks, they retain moisture, protect against wind, and provide shade and nutrients that are compounds from accumulated dust which dissolve in rainwater (
The aim of the study was to investigate the taxonomic diversity and ecological requirements of diatoms inhabiting various microhabitats on trunks of deciduous trees in Central Europe in areas confronting various degrees of human impact. Additionally, preferences of diatoms for host tree species and microhabitats within trunks were determined.
Samples were collected in 2017 and 2018 four times each year in the first half of April and June, and the second half of August and October from heights of 20 cm (referred to as trunk base) and 150 cm above ground level from several tree trunk microhabitats, i.e., bare bark, moss clumps, bark covered with lichens, bark with visible mats of algae (Fig.
Types of studied microhabitats on the example of sycamore maple. Bare bark (
List of studied sites with the sampled tree taxa and microhabitat type over their trunk.
Site | Tree species | Coordinates | Studied microhabitat |
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1 |
|
bare bark, lichens | |
|
bare bark, lichens | ||
|
bare bark, mosses, lichens | ||
2 |
|
lichens | |
|
lichens | ||
|
bare bark, mosses, lichens | ||
3 |
|
bare bark, mosses, green algae mats | |
|
bare bark, mosses | ||
|
bare bark, mosses | ||
4 |
|
bare bark, lichens | |
|
bare bark, lichens | ||
|
bare bark, mosses, lichens | ||
5 |
|
bare bark, mosses | |
|
bare bark, mosses | ||
|
bare bark, mosses, lichens, green algae mats | ||
6 |
|
bare bark, mosses | |
|
bare bark, mosses | ||
|
bare bark, mosses, green algae mats | ||
7 |
|
bare bark, mosses, green algae mats | |
|
bare bark, mosses, lichens | ||
|
bare bark, mosses | ||
8 |
|
bare bark, mosses, lichens | |
|
bare bark, mosses, lichens | ||
|
bare bark, mosses, lichens |
The samples were also used to prepare filtrates for pH and conductivity analyses. The filtrates were obtained by soaking bare bark pieces in deionized water (1:10 by weight) for 24 hours. The intact pieces of bark were used to obtain a solution similar to that forming on the bark surface that is a source of water and nutrients for corticolous organisms; in the case of trees completely covered by epiphytic mosses, the material together with them was used to obtain filtrates. Electrolytic conductivity and pH were measured with a MARTINI pH56 pH meter and a MARTINI EC59 conductometer (Milwaukee Electronics Kft.). The ions’ content was determined using a Thermo scientific DIONEX ICS–5000+DC device in the Departmental Laboratory of Analysis of Environmental Health and Materials of Agricultural Origin at the University of Rzeszów.
A modified method by
Light microscope slides were prepared by applying the cleaned diatom suspension to cover-slips that were left to dry. The dried material was mounted in synthetic Pleurax resin, Brunel Microscopes ltd. (refractive index 1.75). To better define the species composition of the assemblages analyzed, two microscope samples on coverslips were mounted on a single slide. In total, 647 samples were collected and analyzed. The diatoms were identified under a Carl Zeiss Axio Imager.A2 light microscope (
Two microscope slides were made from each collected sample. Diatoms were identified in both slides by observations in all possible adjacent transects. During species identification, all identified valves were counted until a number of 400 was reached. Identification of species was continued for species composition also after reaching the assumed limit of 400 valves. The dominance structure and similarity analysis were determined only for samples for which a minimum of 200 valves were counted. Species with a minimum share of 10% in the assemblages were considered dominants. The remaining samples were considered unrepresentative because of the insufficient development of assemblages or their complete absence. To present the morphological variability of the observed taxa, valves dimensions were measured under light microscope using AxioVision SE62 Rel. 4.9.1 software. For range dimension of commonly occurred taxa ca. 50 specimens were measured including the biggest and the smallest observed specimens. In the case of rare taxa (observed in <10 samples) each observed specimen was measured.
Diatom diversity was analyzed using the Shannon diversity index (H’) and the Evenness index (J’). Principal Component Analysis (
Student’s t-test was used to analyze the significance of differences in the chemical parameters of the samples, and values at p<0.05 were considered statistically significant. All calculations were performed using Statistica 13.3 software.
Diatom terminology and identification were based on
The pH of the analyzed filtrates indicated slightly acid to neutral condition of the barks of the tree species examined. The electrolytic conductivity values measured in the filtrates of all the trees analyzed indicated a very wide range (from 49 µm cm-1 to 5 846 µS cm-1), regardless of sampling height (Table
Chemical parameters measured in filtrates obtained from bark of studied trees, given range (minimum and maximum), and median (brackets), bold indicates value for samples from trunk bases. * – indicates a parameter in which differences between the studied heights were statistically significant (p> 0.05).
Tree taxon |
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|
|
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|
5.3–7.3 (6.3) | 4.7–7.3 (6.0)* | 4.8–7.5 (6.3)* |
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|||
49–2305 (167)* | 49–462 (202) | 52–2305 (323.1) | |
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||
0.5–29.9 (3.3) | 1.1–20.7 (6.3) | 0.442–103.7 (9.4) | |
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|
|
<0.001–4.6 (1.5) | <0.001–4.6 (2.5) | <0.001–159.3 (3.4) | |
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|
<0.001–44.8 (11.1) | <0.001–34.8 (10.1)* | <0.001–36.7 (8.8)* | |
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|||
0.7–55.5 (7.2) | <0.001–61.5 (18.6) | <0.001–400.9 (20.9) | |
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|
0.3–12.4 (2.5) | 0.4–12.2 (3.1)* | 0.273–59.2 (6.8) | |
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||
10.2–137.9 (33.7) | 9.509–68.1 (35.9) | 7.8–752.2 (86.3) | |
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|
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0.6–48.2 (6.7) | 0.1–26.4 (10.6) | 0.3–56.5 (8.5) | |
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0.2–18.5 (2.4) | 0.3–10.6 (2.7) | 0.1–37.1 (3.5) | |
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<0.001–28.5 (3.8)* | 0.1–23.7 (5.6) | <0.001–12.3 (2.3)* | |
|
Rectangular in girdle view. Valves linear to linear lanceolate with weakly protracted and moderately rounded apices, smaller specimens without protracted apices. Valve length 10–25 µm, and valve width 4–6 µm. Axial area narrow linear, slightly expanded near central area. Central area wide and rounded, bordered by 3–4 areolae. Ghost areolae commonly present in central area. Round isolated pore located half way between valve center and margin. Raphe branch straight with both endings clearly curved to site opposite to isolated pore. Distal raphe endings short, not continuing onto mantle. Internal raphe slit simple and straight, distal endings form slightly developed helictoglossae. Striae number 18–20 in 10 µm composed of 2–3 same sized, rounded to slightly elongated areolae. Single row of areolae present also on valve mantle. Internally areolae covered by hymen forming continuous strip, separated by not thickened virgae. Internally small lipped opening of isolated pore visible. Marginal channel located on valve face/mantle junction occluded by hymenes and visible internally.
Stalowa Wola, Podkarpacie Province, Poland,
The name refers to the occurrence of the species mainly in terrestrial bryophytes.
Species observed at most of the sites studied, always in single specimens, mainly in samples of bryophytes from trunk bases.
Valves elliptic to elliptic-lanceolate with rounded apices, rectangular in girdle view. Valve length 9–22 µm, and valve width 4.5–5.5 µm. Axial area narrow and linear, central area elliptic bordered by 3–4 areolae. Round isolated pore located halfway between valve center and margin. Raphe branch straight. Proximal raphe endings deflected to site opposite to stigma with small rounded depressions. Distal raphe endings hooked continuing onto valve mantle. Internally raphe slit simple and straight, distal endings form slightly developed helictoglossae. Striae number 20–22 in 10 µm composed mainly of 4 areolae, single row of areolae also present on valve mantle. On apices row of mantle areolae interrupted by distal raphe endings. Internally areolae covered by hymen forming continuous strip, separated by not thickened virgae. Internally small lipped opening of isolated pore visible. Marginal channel located on valve face/mantle junction occluded by hymenes and visible internally.
Number of diatom taxa identified during the research on each of the examined trees on each site and value of Eveness index (J’) and Shannon index (H’). 1–8 number of sampling site.
Stalowa Wola, Podkarpacie Province, Poland,
The name refers to possible past confusions in identification of the species described with other small taxa with elliptic-lanceolate valves.
Species observed at all sites studied, always in the form of individual specimens. It mainly occurred in samples taken from the base of the trunks of the trees studied.
During the study 143 diatom taxa representing 39 genera were identified (Table
Complete list of documented diatom taxa with measured dimension ranges (
Taxa | Dimensions |
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Freq. | Min-Max | Freq. | Min-Max | Freq. | Min-Max | ||
15–32 / 4–7; | 21 | 0.21–0.48 | 22 | 0.31–0.32 | 27 | 0.22–1.42 | |
11–13 |
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5–18 / 3; | 11 | 0.24–0.48 | 4 | + | 8 | – | |
21–22 |
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7–10 / 2.7–3; | – | – | – | – | – | – | |
17–18 |
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+ | |
– | 14 | 0.25–0.31 | 9 | 0.20 | 5 | 0.12–0.34 | |
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12–19 / 3.5–4.5; | 1 | + | |||||
19–23 | – | – | |||||
13–25 / 4–4.5; | 4 | 0.37–0.48 | 1 | + | 2 | – | |
23–26 |
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+ |
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17–26 / 4.5–5; | 1 | 0.31 | – | + |
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+ | |
26 | – |
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23.5–32.5 / 5–6; | – | – | – | – | |||
14–16 |
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+ | |||
12–18 / 4–4.5; | 1 | + | |||||
27–30 | – | – | |||||
21–23.5 / 10; | 1 | 0.30 | |||||
27 | – | – | |||||
8–15 / 7–10; | 1 | + | 1 | + | |||
14–22 |
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+ | – | – | |||
8–15 / 8–11; | 5 | 0.26–0.37 | 4 | + | 2 | 0.32 | |
14–26 |
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17–26 / 8–11; | 2 | + | – | – | |||
18 |
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7–20 / 7–11; | – | – | 2 | + | – | – | |
15 |
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+ |
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22.5–26 / 13–15; | 1 | + | |||||
15–16 | – | – | |||||
– | 22 | 0.16–0.50 | 19 | + | 14 | 0.22–0.37 | |
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17–22.5 / 7–9; | 3 | 0.21–0.33 | – | – | 1 | + | |
14 |
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6–26 / 3–3.5; | – | – | – | – | |||
16–19 |
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+ | ||||
12.5–31.5 / 4–6; | 1 | + | – | – | |||
10–12 | – | – |
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8.8 / 2–2.2; | – | – | 2 | – | |||
not visible in |
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+ | – | + | |||
6.5–21 / 4.5–6.5; | 2 | 0.31–0.66 | 1 | – | 2 | 0.47 | |
22–25 |
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22.5–24 / 5; | – | – | |||||
13–14 |
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12–23 / 5–6; | 1 | 0.32 | – | – | – | – | |
10–11 | – | – |
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+ |
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+ | |
22 / 7; | 1 | 0.24 | – | – | |||
12 | – | – |
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+ | |||
30–35 / 9–10; | 1 | 0.31 | – | – | |||
10–11 |
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20–24.5 / 6.5–7; | – | – | |||||
11 |
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+ | |||||
20–26 / 7–7.5; | 2 | 0.13 | 1 | + | 1 | + | |
10–12 |
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10–15 / 6–7; | 1 | 0.24– | – | – | 2 | – | |
11–13 | – |
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+ |
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12–20 / 3.5–5.5; | 18 | 0.20–0.34 | 13 | 0.31–0.32 | 16 | 0.17–3.79 | |
not visible in |
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1 |
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35–74.5 / 6–9.5; | 47 | 0.21–2.81 | 51 | 0.30–0.61 | 51 | 0.12–6.16 | |
19–20 |
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12–45 / 4.5–7; | 88 | 0.20–23.13 | 84 | 0.30–2.76 | 87 | 0.12–93.90 | |
21–27 |
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28–85 / 6.5–7.7; | 18 | 0.21–23.18 | 20 | + | 18 | 0.17–0.47 | |
16–19 |
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60 / 6.7; | – | – | |||||
18–19 |
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+ | |||||
33 / 5; | – | – | |||||
25 |
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+ | |||||
26.7–81 / 6.7–9; | 9 | 0.25–0.66 | 10 | + | 13 | 0.35–0.95 | |
14–17 |
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8–19.5 / 6–6.5; | 1 | – | 1 | + | 2 | – | |
not visible in |
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+ |
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5–13 / 2.5–3.2; | 53 | 0.20–23.13 | 32 | 7.50–58.51 | 40 | 0.56–59.25 | |
not visible in |
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4–10 / 2–3; | 2 | 0.31 | 9 | 0.20 | 10 | 0.35–10.90 | |
not visible in |
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+ |
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15–21 / 6.2–6.5; | 6 | 0.24–0.31 | 2 | + | 2 | 0.24 | |
not visible in |
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6–13.5 / 4–5; | 1 | + | 5 | 0.84 | |||
not visible in |
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+ |
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8–13 / 4–6; | – | – | 1 | + | – | – | |
18–21 |
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+ |
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10–32 / 4.8–8.7; | 81 | 0.31–98.77 | 50 | 2.50–38.21 | 55 | 1.02–97.33 | |
18–23 |
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12–15.5 / 4–4.5; | – | – | |||||
21–22 |
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18–21 / 6.5; | – | – | – | – | |||
20–21 |
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+ |
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+ | |||
10–25 / 4–6; | 5 | 0.26 | 8 | + | 5 | 0.24 | |
18–20 |
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15–18 / 6.5; | – | – | |||||
20–21 |
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0.16 | |||||
17.5–28.5 / 8.5–10; | – | – | – | – | |||
20–21 |
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0.31 |
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+ | |||
9–22 / 4.5–6; | 20 | 0.24–0.32 | 13 | – | 20 | 0.35–3.32 | |
20–22 |
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15–17 / 5.5–7; | – | – | 1 | + | – | – | |
20 |
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+ |
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+ | ||
12–16 / 5.6–7; | 2 | – | – | 2 | + | ||
20–22 | – |
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+ |
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15–23.5 / 7–8; | 1 | + | 1 | + | |||
20–21 | – | – |
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+ | |||
7.5–13 / 3.8–4.5; | 6 | 0.24–0.32 | 5 | 0.30–0.31 | 7 | 0.24–0.28 | |
22–24 |
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10–21 / 5.8–7.5; | 16 | 0.28–0.36 | 15 | 0.32 | 21 | 0.17–0.95 | |
19–21 |
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15–23.5 / 6.5–8; | 1 | 0.48 | 1 | + | 6 | 0.47 | |
18–19 | – | – |
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10–24.5 / 5–7; | 20 | 0.48–0.48 | 28 | 0.30–0.31 | 15 | 0.34 | |
19–22 |
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15–22.5 / 5.5–6.5; | – | – | |||||
20–22 |
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22 / 6; | – | – | |||||
21 |
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+ | |||||
10–20 / 5.9–6.4; | 1 | 0.32 | 7 | 0.31 | 15 | 1.90 | |
20–24 |
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13.2–16.5 / 5–6; | 4 | + | 2 | 0.31 | 1 | 0.47 | |
24 |
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– | – | – | – | |
12–15.5 / 6–6.5; | 2 | 0.20–0.31 | 1 | + | 2 | – | |
19–20 |
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+ |
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9.5–27 / 4.5–7; | 14 | 0.28–0.40 | 19 | 0.31 |
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0.12–1.42 | |
18–20 |
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12–14 / 7–8; | 1 | + | |||||
16 | – | – | |||||
19–22.5 / 7.5–7.8; | – | – | – | – | |||
24–25 |
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+ |
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14.5–19 / 5.5–7.3; | 10 | + | 6 | + | |||
18–21 |
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10–23 / 5.5–7; | 20 | 0.23–0.40 | 16 | 0.30–0.31 | 15 | 0.24–3.79 | |
19–22 |
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9.2–22 / 5–7; | 10 | 0.26–0.61 | 23 | 0.30–0.31 | 35 | 0.12–1.42 | |
19–22 |
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10–23.7 / 5–7.2; | 8 | 0.16–0.25 | 7 | + | 9 | 0.12–0.34 | |
20–24 |
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14–18 / 5.5–7; | – | – | 1 | 0.31 | 2 | 0.25 | |
18–23 |
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- | – | + | – | – | – |
+ | |
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+ |
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12–16.5 / 5.5–6; | 1 | 0.32 | 2 | + | 4 | + | |
16–18 |
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+ |
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7–13 / 4–5; | 5 | + | 9 | 0.31 | 7 | 0.22–0.95 | |
18–22 |
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11–14.5 / 5–7; | 2 | 0.22 | – | – | 1 | + | |
16–17 |
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+ |
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9–11.5 / 3–4; | 1 | + | 1 | + | 1 | + | |
17–19 |
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+ |
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9–11 / 4.5; | – | – | |||||
18 |
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7–12 / 3.5–4.5; | 1 | + | 1 |
1 | 2 | + | |
ca. 35 |
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13–24 / 5–6 | 3 | 0.20–0.31 | 7 | + | 2 | 0.24 | |
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+ |
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+ | ||
6–9.5 / 2.5–3.5; | 1 | + | – | – | |||
not visible in |
– | – |
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+ | |||
19.5–30 / 6.7–7.7; | 2 | + | 2 | + | 3 | + | |
22–25 |
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+ |
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+ | |
22.5–29.5 / 5.8–6.2; | – | – | 3 | + | 1 | – | |
23–24 |
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+ |
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23.5–26 / 5.2–6; | 3 | 0.24 | 2 | + | 3 | + | |
18–19 |
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v | |
12–22 / 4.3–5; | 3 | + | 1 | + | – | – | |
26–28 |
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– | – |
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+ | ||
17–18 / 3; | 1 | + | – | – | 1 | 0.34 | |
18 | – | – |
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+ |
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15.5–22 / 6–7; | – | – | 1 | + | 1 | 0.12 | |
16 | 1 |
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14–25 / 4.2–6; | – | – | 1 |
0.47 | |||
15 |
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12–32 / 4.5–6; | 38 | 0.16–0.80 | 36 | 0.20–0.32 | 43 | 0.12–5.69 | |
11–13 |
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40 |
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38 |
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11–24 / 4–5; | 30 | 0.16–0.62 | 21 | 0.18–0.24 | 22 | 0.12–1.12 | |
11–13 |
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14–18 / 3–3.5; | – | – | 1 | + | 1 | + | |
16 |
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– | – | |
12–25.5 / 4.5–5.5; | 1 | + | – | – | 1 | 0.12 | |
13–16 |
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15–29 / 4.5–5; | – | – | |||||
ca. 37 |
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+ | |||||
15.5–26 / 4.5–5.5; | 2 | 0.31–0.33 | |||||
21–23 |
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9–28 / 4–5.5; | 9 | 0.21–0.48 | 6 | 0.31 | 8 | 0.34–0.47 | |
15–18 |
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12–15 / 3.5–4; | 1 | – | – | – | – | ||
18–20 | – |
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+ | ||
15–20 / 4; | 1 | 0.24 | 1 | + | |||
not visible in |
– | – |
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19–36 / 3–4; | 1 | 0.25 | |||||
not visible in |
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7–22 / 2.5–3.5; | 5 | 0.21–0.36 | 5 | 0.20 | 2 | + | |
not visible in |
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4–16.5 / 3; | 15 | 0.25–0.36 | 9 | – | 4 | 0.12 | |
25–27 |
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11.5–24 / 3–4; | 1 | 0.24 | – | – | 3 | 0.33 | |
21–23 |
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+ |
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10–20 / 2.5–3.5; | – | – | 2 | 1.42 | |||
27–30 |
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+ | – | – | |||
50–55 / 6; | – | – | |||||
28–29 | 2 | ||||||
Ø – 7–26; | 36 | 0.24–95.69 | 7 | + | 9 | 0.17–3.59 | |
20–22 |
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16 |
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Ø – 8–24; | 4 | 0.24–0.71 | 2 | + | 1 | 0.17 | |
8–12 |
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– | – |
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– | 6 | 0.24–0.34 | 2 | + | 6 | 0.12–0.33 | |
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+ |
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22–42 / 8–9.5; | 68 | 0.21–58.21 | 52 | 0.30–1.81 | 57 | 1.63–97.80 | |
ca. 5 |
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35–40 / 8.5–9; | – | – | 1 | + | 1 | 0.47 | |
ca. 5 |
|
|
|
|
|
||
10–34 / 9–12; | 1 | + | 1 | + | 2 | + | |
10–13 |
|
|
|
+ |
|
||
24.5–30 / 7–8; | 9 | 0.28–0.34 | 3 | + | 9 | 0.34 | |
10–11 |
|
|
|
|
|
||
40 / 9; | – | – | |||||
ca. 5 |
|
+ | |||||
13–22 / 4–4.5; | 3 | + | 1 | + | 2 | + | |
17–18 |
|
|
+ |
|
|
||
30–45 / 7–9; | 2 | 0.28–0.36 | 2 | + | 1 | 0.24–0.47 | |
10–12 | – | – |
|
|
|
||
42–44 / 6.5–7; | 1 | + | |||||
12–13 | – | – | |||||
35 / 6.5; | 1 | + | |||||
11 | – | – | |||||
9–35 / 3–5; | 55 |
0.21–1.95 | 29 | 0.20–0.31 | 3 | 0.24–1.90 | |
10–13 |
|
|
|
|
|
||
12–25 / 4; | – | – | 1 | + | |||
16–18 |
|
|
|
||||
19–34 / 5–6.5; | 10 | 0.22–0.50 | 11 | + | 6 | 0.33 | |
14–16 |
|
|
|
|
|
||
17–35 / 4.5–6; | 3 | 0.21–0.36 | 1 | + | 2 | + | |
11–13 |
|
|
|
|
|
+ | |
14–22 / 5–7; | 1 | + | – | – | |||
13–16 |
|
|
|
||||
4–25 / 3.5–6; | 6 | 0.16–0.36 | 5 | 0.31 | 8 | 0.22–2.37 | |
14–17 |
|
|
|
|
|
|
|
7–25 / 4–6.5; | 5 | 0.21–0.30 | 5 | 0.30 | 2 | 0.12 | |
13–15 |
|
|
|
|
|
|
|
– | – | – | – | – | |||
|
+ |
|
+ | ||||
9–14 / 3.5–5.5; | – | – | – | – | |||
9–13 |
|
|
|
+ | |||
6–12 / 3–4; | 5 | 0.31–0.36 | 7 | + | 4 | 0.12–1.42 | |
22–25 |
|
|
|
|
8 |
|
|
5.5–12 / 3–4; | – | – | – | – | 1 | + | |
32–35 |
|
|
|
+ | – | – | |
15–18.5 / 4–4.5; | 2 | 0.30 | – | – | 1 | 0.47 | |
38 |
|
|
|
+ | – | – | |
5–10 / 4; | 1 | 0.47 | |||||
28–30 |
|
+ | |||||
7–14 / 3.2–3.8; | 1 | + | 2 | 0.31 | 1 | + | |
23–25 |
|
|
|
|
|||
10–26 / 3.8–5; | 19 | 0.22–0.33 | 22 | 0.20 | 18 | 0.17–0.95 | |
22–26 |
|
|
|
|
|
|
|
19–26 / 6.5–8.5; | – | – | 5 | + | |||
17–20 |
|
|
+ | ||||
20–22 / 4.5; | – | – | |||||
24 |
|
|
|||||
14–19 / 4–5; | 2 | 0.20 | 4 | + | 4 | 0.17–0.22 | |
23–24 |
|
|
|
|
|
||
16–20 / 3–4; | 1 | + | 2 | – | – | ||
22–26 |
|
|
|
|
+ | ||
15–28 / 6–8; | 1 | + | 3 | + | 2 | + | |
19–23 |
|
|
|
|
+ | ||
8–18 / 3–4.5; | 2 | 0.32–0.34 | 1 | + | 2 | + | |
20–23 |
|
|
|
|
|
||
30–35/ 8.5–9.5; | 3 | 0.48 | 1 | + | 3 | + | |
15–17 | 2 |
|
|
+ |
|
||
13–14 / 3.8–4.2; | 1 | 0.30 | 1 | + | |||
ca. 28 |
|
|
|
+ | |||
8–18 / 3–4.5; | 18 | 0.21–0.37 | 7 | + | 2 | 0.12 | |
20–23 |
|
|
|
|
|||
16.5–42.5 / 6–9; | 3 | + | 1 | + | 2 | 0.12–0.47 | |
24–27 | – | – |
|
|
|
|
|
9–34.5 / 8–10; | – | – | 2 | + | 2 | + | |
26–28 |
|
|
|
|
|
||
11–18.1 / 6.4; | 10 | 0.21–0.36 | 9 |
+ | 2 | + | |
18–23 |
|
|
|
|
|||
20–24 / 4.5–5.5; | – | – | |||||
17 |
|
||||||
12–23.5 / 7–8.5; | – | – | 1 |
+ | – | – | |
not visible in |
|
+ | + |
|
|||
35–42 / 5.2–6; | – | – | – | – | |||
8–10 |
|
|
|
Of the 647 samples collected, only in 197 were numerous occurrences of diatoms observed. Diatoms did not occur, or occurred only, as individual valves in all samples from barks covered with lichens or algal mats. Numerous diatom assemblages were observed in 74 of 283 samples from bare bark (27 from 20 cm above ground level and 47 from 150 cm above ground level). Numerous assemblages were also observed in 123 of 231 moss samples collected (43 from 20 cm above ground level and 80 from 150 cm above ground level).
Higher values of both indices studied (H’ and J’) were usually recorded for bare bark samples, and higher values of both of these indices were also recorded for samples collected from trunk bases (Fig.
Principal component analysis (
Tree barks, thanks to their porosity, can absorb rainwater; therefore the solution on its surface is usually slightly acidic. On the other hand, pH reactions often depend on bark structures, which differ depending on tree species (
Of the 647 samples collected, only 197 had developed diatom communities, and only single valves were found in the remaining samples. The almost complete or complete absence of diatoms was observed in bark samples covered with visible mats of green algae. Other studies focusing on corticolous algae assemblages, in which only a few species of diatoms have been found (
Although trees growing as close as possible to each other were selected at the sites and materials from analogous microhabitats were collected from them, differences in the frequency of occurrence of diatom assemblages were clearly notable. On bare bark, diatom assemblages were found mainly in materials collected from maples and poplars at locations closest to natural sites (parks and national park buffer zones). However, diatoms were not found or only single specimens were observed in bare bark samples from site 7 (the buffer zone of Magura National Park). This was the only site where samples were collected from aspen poplar (
Materials from moss microhabitats were more than half of the samples in which large numbers of diatoms were found (123 out of 197 samples). This result is similar to the study by
The developed diatom assemblages in the microhabitats analyzed were more often recorded in samples taken from trunk bases than from a height of 150 cm above ground level, and more species were also noted in samples collected from trunk bases (Table
Both of the newly described
During the study 143 diatom taxa were identified, but most of them were found in single samples and often their share did not exceed 1% of communities. Only 16 species were common in the samples studied (in over 20% of the samples), of which 13 species formed numerous populations (from 10% in assemblages to practically monocultures). The vast majority of the species recorded were taxa commonly identified in various terrestrial environments, mainly in soils (
Assemblages noted on the trunks of all the trees studied growing in city centers and small peripheral estates were dominated by species able to develop in low moisture habitats with high osmotic stress (
Similar assemblage structures were also noted on linden and poplar at sites located in suburban park complexes and national park buffer zones. It seems that corticolous assemblages consisting mainly of drought-resistant diatom taxa are typical of these tree species regardless of the degree of tree cover in the area in which they grow.
Assemblages from sycamore maple (except those from city centers) were distinctly different from those inhabiting linden and poplars because of the strong domination of just one species, which often formed near monocultures (Fig.
Additionally, many diatom species often common in terrestrial and aerophytic habitats (numerous representatives of the genera
Except for taxa commonly reported from terrestrial habitats, diatoms that usually occur in aquatic environments were noted. The most common were centric taxa such as
The present research showed that the occurrence of diatom assemblages on tree trunks is influenced by many factors, such as host tree species and the area in which these trees grow, high above soil as well as the presence of suitable microhabitats within trunks. Additionally, diatom assemblage composition was mainly influenced by the tree species.
The current research focused on communities developing on only a few tree species occurring naturally in Europe. Further research involving other tree taxa is necessary for developing a better understanding of corticolous diatom assemblages.
The first author would like to acknowledge prof. Agata Z. Wojtal and prof. Małgorzata Bąk for a detailed review of his doctoral thesis, which was the basis for the preparation of this article. The authors would also like to acknowledge Dr Kalina Manoylov (editor) and an anonymous reviewers for their work with the manuscript and their suggestions which helped to prepare the final version. The work was supported by the program of the Minister of Science and Higher Education under the program “Regional Initiative of Excellence” 2019–2023, project number 026/RID/2018/19.