Phytosociological Ranks and Nomenclature

Abstract vegetation units defined by floristic-sociological criteria are termed syntaxa. They are positioned in a hierarchy of different ranks (Table 5), which is meant to make the multitude of units manageable and offers the opportunity to vary the conceptual resolution of analysis, maps, and graphs. The association is considered as the basic unit, comparable to species in taxonomy. Ranks below the association level are often used to express edaphic (subassociations and variants), climatic (altitudi-nal forms), geographic (vicariants or races), structural (facies of dominant species), and successional variation (phases).

Like other fields of biological systematics, syntax-onomy is an open-ended process that is carried out by a large community of independent researchers and requires unequivocal rules for naming classification units. Therefore, the Nomenclature Commission of the International Association for Vegetation Science (IAVS) and the Federation Internationale de Phytosociologie (FIP) have established the International Code of Phytosociological Nomenclature (ICPN), similar to the nomenclature codes used in botanical and zoological taxonomy.

The ICPN regulates the scientific nomenclature of four principal and four supplementary ranks of syntaxa. Neither synusial nor symphytosociological units (see the section entitled 'Symphytosociological approaches'), nor informally named syntaxa (e.g., Elymus repens community) fall under the ICPN. The ICPN provides precise instructions for the formation of syntaxon names, their valid publication, and the decision about which of several available names from the earlier literature to apply. According to the ICPN, every syntaxon of a certain circumscription and rank has only one correct name. However, the ICPN only regulates the nomenclature and does not define rules for proper delimitation and classification of syntaxa. Aiming to provide unambiguity and stability of syntaxon names, the ICPN is based on two major principles: (1) among several names for a syntaxon, the oldest valid (published) name is the correct one (priority); (2) each syntaxon name is connected to a nomenclatural type (a single releve for associations, a validly described lower-rank syntaxon for higher syntaxa), which determines the usage of the name when this syntaxon is split off, merged with others, or otherwise changed in its delimitation.

Syntaxon names are formed of the scientific names of one or two (in the case of subassociations, up to three) plant species or infraspecific taxa, which usually are, but

Table 4 (a) Worked example (I): Releve table containing three associations of three alliances and two classes of the subalpine heathland and grassland vegetation of the Czech Republic (see Table 6 for their position in the syntaxonomic hierarchy). Species of the cryptogam layer are marked with 'C', the other species belong to the herb layer. Blocks of diagnostic species are shaded. Within blocks, diagnostic species are ranked by decreasing fidelity to the given syntaxon. Fidelity was measured with the phi coefficient of association and was based on the comparison of species occurrences within the syntaxa of this table only; species with <fi > 0.25 were considered as diagnostic. As each association belongs to a different alliance, diagnostic species of the associations can be partly considered as diagnostic of the alliances. Companion species are ranked by decreasing constancy within the entire table. Data were taken from the Czech National Phytosociological Database. Species occurring in a single releve are not shown. (b) Worked example (II): Synoptic table based on the same data as Table 4a. The numbers in the table are percentage constancies

Table 4 (a) Worked example (I): Releve table containing three associations of three alliances and two classes of the subalpine heathland and grassland vegetation of the Czech Republic (see Table 6 for their position in the syntaxonomic hierarchy). Species of the cryptogam layer are marked with 'C', the other species belong to the herb layer. Blocks of diagnostic species are shaded. Within blocks, diagnostic species are ranked by decreasing fidelity to the given syntaxon. Fidelity was measured with the phi coefficient of association and was based on the comparison of species occurrences within the syntaxa of this table only; species with <fi > 0.25 were considered as diagnostic. As each association belongs to a different alliance, diagnostic species of the associations can be partly considered as diagnostic of the alliances. Companion species are ranked by decreasing constancy within the entire table. Data were taken from the Czech National Phytosociological Database. Species occurring in a single releve are not shown. (b) Worked example (II): Synoptic table based on the same data as Table 4a. The numbers in the table are percentage constancies

(a) Releve table

(b) Synoptic table

Association

Junco trifidi-Empetretum hermaphroditi

Cetraro-Festucetum supinae

Carci-Nardetum

J-E

C-F

C-N

Releve number

1 2 3 4 5 6

7 8 9 10

11

12

13

14 15 16 17 18 19

20

21

22

23

24 25 26 27

28

29

n = 13

n=10

n = 6

Diagnostic species of the association Junco trifidi-Empetretum hermaphroditi

Empetrum hermaphroditum

5 S S S 5 4

S S S S

4

4

4

. . . . + .

100

10

Hylocomium splendens (C)

. . 1 r . 2

. . 1 .

r

SB

Vaccinium myrtillus

112 2 12

112 2

1

2

2

1 + . . + 1

+

. . + +

+

100

50

50

Melampyrum sylvaticum

. . + . . +

. . . +

+

S1

Pleurozium schreberi (C)

. . 1 r . 2

. . S r

r

. . . +

46

17

Polytrichum piliferum (C)

2 +

2 + . .

2

. . . 1 . .

SB

10

Diagnostic species of the association Cetrario-Festucetum supinae

Cladonia bellidiflora (C)

. . . . + +

+

S0

Thamnolia vermicularis (C)

. + . .

. + . . + +

+

B

40

Diagnostic species of the association Carici bigelowii-Nardetum strictae

Nardus stricta

. . . . 1 .

2

+

1

S 4 4 4

4

5

40

100

Galium saxatile

2 . + .

2

50

Anthoxanthum alpinum

1

. r . 1

2

10

50

Deschampsia cespitosa

. + . 1

SS

Festuca rubra agg.

. . . 1

+

SS

Luzula campestris agg.

. . . 1

+

SS

Potentilla erecta

. . . 1

+

SS

Diagnostic species of the class Juncetea trifidi

Calluna vulgaris

2 1 + 11 +

2

+

2

. + 1 r

90

50

Bistorta major

+ ...

1 + 1 + + +

1

1

+

+ . + +

B

90

50

Agrostis rupestris

. 1 . . . +

1

1

. + . .

40

17

Carex bigelowii

4 + . S + .

1

1

1

1 + . +

+

70

67

Hieracium alpinum agg.

1 . . .

+

. + 2 . + +

1

2

1

+

+ 1 + +

+

15

B0

BS

Companion species

Avenella flexuosa

+ + + 1 1 1

2 11 +

1

1

1

1 + 1 S + .

S

1

2

2

4 + S 2

2

100

90

BS

Vaccinium vitis-idaea

. 2 12.2

. 1 2 1

+

1

2

11... +

. + + +

2

77

S0

67

Cetraria islandica (C)

. + 1 r . 1

. + 2 r

2

r

. + 2 . + .

2

S

+

69

60

Festuca supina

. . . 1 . .

. . 1 .

1

2 2 S 1 . S

2

+

. . + .

1

+

2S

70

50

Solidago virgaurea Homogyne alpina Huperzia selago Calamagrostis villosa Juncus trifidus Trientalis europaea Vaccinium uliginosum Racomitrium lanuginosum (C) Cladonia arbuscula (C) Cladonia rangiferina (C) Dicranum fuscescens (C) Polytrichastrum alpinum (C) Alectoria ochroleuca (C) Campanula bohémica Pulsatilla alpina ssp. austríaca Pohlia nutans (C) Polytríchum strictum (C) Silene vulgaris Cetraria cucullata (C) Diphasiastrum alpinum Polytríchum juniperinum (C) Cladonia pyxidata (C) Veratrum album subsp. lobelianum

31

40

50

15

40

50

23

50

23

10

50

23

20

31

17

31

10

15

20

8

30

8

30

23

15

10

8

20

20

17

20

17

8

17

15

10 17 10 17

Table 5 Syntaxonomic ranks whose names are regulated by the International Code of Phytosociological Nomenclature (ICPN)

Rank Termination Example (without author citation)

Table 5 Syntaxonomic ranks whose names are regulated by the International Code of Phytosociological Nomenclature (ICPN)

Rank Termination Example (without author citation)

Classa

-etea

Koelerio-Corynephoretea

Subclassb

-enea

Koelerio-Corynephorenea

Order5

-etalia

Phragmitetalia australis

Suborderb

-enalia

Oenanthenalia aquaticae

Alliancea

-ion

Fagion sylvaticae

Suballianceb

-enion

Cephalanthero-Fagenion

Associationa

-etum

Corniculario aculeatae-Corynephoretum canescentis

Subassociationb

-etosum or 'typicum' or 'inops'

Corniculario aculeatae-Corynephoretum canescentis cladonietosum

aPrincipal rank (obligatory). bSupplementary rank (optional).

aPrincipal rank (obligatory). bSupplementary rank (optional).

Table 6 Worked example (III): Syntaxonomic hierarchy including all principal ranks and full syntaxon names with author citations for the syntaxa presented in Table 4

Class: Loiseleurio-Vaccinietea Eggler ex Schubert 1960 Order: Rhododendro-Vaccinietalia Braun-Blanquet in Braun-Blanquet et Jenny 1926

Alliance: Loiseleurio procumbentis-Vaccinion Braun-Blanquet in Braun-Blanquet et Jenny 1926 Association: Junco trifidi-Empetretum hermaphroditi Smarda 1950

Class: Juncetea trifidi Hadac in Klika et Hadac 1944 Order: Caricetalia curvulae Braun-Blanquet in Braun-Blanquet et Jenny 1926 Alliance: Juncion trifidi Krajina 1933

Association: Cetrario-Festucetum supinae JenÍk 1961 Alliance: Nardo strictae-Caricion bigelowii Nordhagen 1943 Association: Carici bigelowii-Nardetum strictae (ZlatnÍk 1928) Jeník 1961

need not be, characteristic in the respective vegetation type. The formation of the scientific syntaxon names involves connecting vowels, the declination of the taxon epithets, and addition of terminations indicating syntaxonomic rank (Table 5). An 'author citation' (i.e., the author(s) and year of the first valid publication) also forms part of the complete syntaxon name (see Table 6).

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