Plant Communities Invaded by Heracleum mantegazzianum

An alternative and more detailed perspective on habitats of H. mantegazzianum is provided by phytosociological analysis of vegetation relevés. We made 202 vegetation relevés in the 20 study areas in Germany during 2002 and 2003. The size of relevé plots was 25 m2. We recorded all vascular plant species in the plots and estimated their abundance based on the modified Braun-Blanquet scale (Braun-Blanquet, 1965; Wilmanns, 1989). The relevés were classified according to the Central European system of plant communities (Ellenberg, 1988; Oberdorfer 1993). Species names follow Wisskirchen and Haeupler (1998). The floristic composition, basic parameters of vegetation structure and species numbers of plant communities with H. mantegazzianum are presented in Table 8.1.

Table 8.1. Composition of plant communities with H. mantegazzianum based on 202 vegetation relevés from 20 study areas in Germany. Constancy of plant species (% of the number of vegetation relevés in which they were recorded) is presented for the types of communities distinguished. Cover (%) and height of the vegetation layers were assessed separately for H. mantegazzianum and the remaining resident herbaceous plant species. Height refers to the main leaf canopy of the vegetation layers. FQ = total frequency of the species in the data set. Species are arranged according to their affinity to particular community types; those which did not exceed a constancy of 10% in at least one community type were omitted. Species names follow Wisskirchen and Haeupler (1998).

Table 8.1. Composition of plant communities with H. mantegazzianum based on 202 vegetation relevés from 20 study areas in Germany. Constancy of plant species (% of the number of vegetation relevés in which they were recorded) is presented for the types of communities distinguished. Cover (%) and height of the vegetation layers were assessed separately for H. mantegazzianum and the remaining resident herbaceous plant species. Height refers to the main leaf canopy of the vegetation layers. FQ = total frequency of the species in the data set. Species are arranged according to their affinity to particular community types; those which did not exceed a constancy of 10% in at least one community type were omitted. Species names follow Wisskirchen and Haeupler (1998).

Managed

Ruderal

Tall-herb

Other open

grasslands

grasslands

communities

Woodlands

vegetation

FQ

Number of relevés

36

53

78

19

16

Average cover (%)

Total

93.5

93.3

87.8

83.7

72.6

Heracleum mantegazzianum

16.5

44.2

48.1

23.2

16.7

Herb layer

88.5

73.1

52

39.6

64.3

Tree layer

-

-

-

66.1

-

Average height (m)

Heracleum mantegazzianum

0.6

1.0

1.2

1.0

0.7

Herb layer

0.4

0.6

0.7

0.5

0.6

Tree layer

-

-

-

15.1

-

Species number

24.5

22.1

14.3

16.8

22.1

Heracleum mantegazzianum

100

100

100

100

100

202

Grasslands

Dactylis glomerata

92

87

36

58

37

124

Holcus lanatus

78

68

12

16

32

81

Arrhenatherum elatius

58

75

22

19

81

Alopecurus pratensis

86

49

22

13

76

Ranunculus repens

75

47

19

21

43

78

Galium mollugo agg.

47

51

9

11

24

57

Taraxacum officinale agg.

69

30

8

5

19

51

Festuca rubra agg.

31

40

3

5

24

39

Rumex acetosa

42

32

3

24

Continued

Table 8.1. Continued.

Managed

Ruderal

Tall-herb

Other open

grasslands

grasslands

communities

Woodlands

vegetation

FQ

Anthriscus sylvestris

36

36

13

11

6

45

Phleum pratense

47

23

4

5

33

Veronica chamaedrys s.l.

22

36

1

5

29

Heracleum sphondylium

39

19

4

6

28

Achillea millefolium agg.

39

19

3

6

27

Agrostis stolonifera

33

21

8

16

24

36

Lathyrus pratensis

33

19

6

24

31

Festuca pratensis

47

8

21

Poa pratensis s.str.

25

21

3

5

23

Trifolium repens

36

11

5

20

Angelica sylvestris

17

23

3

43

27

Bistorta officinalis

39

8

4

6

22

Plantago lanceolata

33

9

1

18

Cirsium palustre

14

21

5

32

25

Agrostis capillaris

33

8

8

5

37

29

Vicia cracca

14

19

3

19

20

Cerastium holosteoides

28

9

15

Lolium perenne

36

2

1

6

16

Leucanthemum vulgare

11

17

13

15

Trisetum flavescens s.str.

19

11

3

6

16

Trifolium pratense

25

6

6

13

Myosotis nemorosa

19

6

16

19

16

Prunella vulgaris

14

9

1

6

12

Lotus pedunculatus

11

11

32

15

Ranunculus acris agg.

17

6

9

Anthoxanthum odoratum

22

2

9

Centaurea jacea

19

4

9

Tall herb communities

Urtica dioica dioica

22

60

97

84

32

137

Galium aparine agg.

8

60

74

53

19

106

Poa trivialis

83

75

69

63

32

141

Aegopodium podagraria

39

19

51

37

6

72

Glechoma hederacea

22

30

42

42

65

Impatiens glandulifera

3

2

40

32

39

Symphytum officinale

11

2

37

16

6

38

Stellaria nemorum

6

4

32

21

33

Alliaria petiolata

31

11

26

Calystegia sepium

6

17

26

5

13

34

Galeopsis tetrahit

3

42

22

32

13

48

Geum urbanum

6

26

21

47

6

42

Elymus repens

47

45

17

19

57

Solidago gigantea

6

17

5

17

Carduus crispus

4

15

14

Filipendula ulmaria

22

21

14

5

13

33

Petasites hybridus

11

8

14

19

Stachys sylvatica

3

19

12

11

22

Table 8.1. Continued

Managed

Ruderal

Tall-herb

Other open

grasslands

grasslands

communities

Woodlands

vegetation

FQ

Cirsium oleraceum

14

G

12

17

Humulus lupulus

2

12

13

12

Phalaris arundinacea

3

11

10

2G

13

22

Poa nemoralis

G

10

47

20

Moehringia trinervia

2

10

11

6

12

Lamium album

3

4

10

11

Woodlands

Acer pseudoplatanus

3

6

a2

19

15

Fraxinus excelsior

6

G

10

2G

18

Stellaria holostea

3

11

6

21

6

17

Alnus glutinosa

5

21

8

Festuca gigantea

6

9

1G

12

Elymus caninus

4

10

11

12

Salix fragilis

8

11

8

Salix eleagnos

1

11

a

Alnus incana

11

2

Populus nigra

11

2

Companion species

Cirsium arvense

58

42

12

43

5g

Rubus fruticosus agg.

25

18

a7

32

ag

Deschampsia cespitosa

17

1g

9

2G

43

a5

Hypericum perforatum

19

28

3

5

32

a0

Rubus idaeus

3

17

12

11

56

30

Vicia sepium

14

aG

4

5

6

2g

Plant communities of H. mantegazzianum in its Central European invaded range predominantly belong to the vegetation classes of semi-natural grasslands and nitrophilous tall-herb communities (Kolbek et al., 1994; Ochsmann, 1996; Otte and Franke, 1998; Sauerwein, 2004; Thiele and Otte, 2006b). Woodlands with H. mantegazzianum belong partly to more or less natural alluvial forests (Kolbek et al., 1994; Sauerwein, 2004; Thiele and Otte, 2006b), but anthropogenic woodlands often do not match with the system of plant communities and, therefore, are not described in detail here. The same applies to some pioneer plant communities of H. mantegazzianum at severely disturbed sites, e.g. sand pits, and other anthropogenic vegetation types (Ochsmann, 1996; Thiele and Otte, 2006). Klauck (1988) classified the stands with dominant H. mantegazzianum as a separate association Urtico-Heracleetum mantegazzianii, but this proposal has been rejected by the majority of authors studying these plant communities (Schwabe and Kratochwil, 1991; Ochsmann, 1996; Otte and Franke, 1998; Sauerwein, 2004; Thiele and Otte, 2006b).

Within the class of semi-natural grasslands (Molinio-Arrhenatheretea) H. mantegazzianum is confined to communities of nutrient rich, mesic to moist sites. These belong to the order Arrhenatheretalia, which comprises oat grass meadows (Arrhenatherion) and rye grass-white clover pastures (Cynosurion). Principally, these communities are characterized by regular agricultural land use (mowing, pasturing). However, H. mantegazzianum is more prevalent in variants without regular land-use regimes. These are, on the one hand, ruderal grasslands maintained by rather irregular mowing or removal of shrubs, such as neglected road verges and grassland margins, and on the other hand, abandoned former agricultural grasslands.

Nitrophilous tall-herb communities of the class Galio-Urticetea which feature H. mantegazzianum are mainly terrestrial ground elder (Aegopodium podagraria L.) communities at mesic to moist sites (Aegopodion) and riparian tall-herb communities (Calystegion). In addition to these, H. mantegazzianum occasionally occurs in the alliance Alliarion, which comprises communities of shady fringes. Within the class Galio-Urticetea, H. mantegazzianum has the highest affinity to plant species that are especially typical or characteristic of Aegopodion communities. Apart from the name-giving species, ground elder, these are most frequently Urtica dioica L., Galium aparine L. and Glechoma hederacea L. In riparian tall-herb communities, H. mantegazzianum is usually confined to zones that are only inundated during floods but otherwise offer aerated top soils (Ochsmann, 1996; Thiele and Otte, 2006b). Therefore, from the phytosociological point of view, H. mantegazzianum is a species of terrestrial tall herb communities of the alliance Aegopodion (Sauerwein, 2004; Thiele and Otte, 2006b).

According to Sauerwein (2004), H. mantegazzianum can also establish in ruderal annual communities of the alliance Sisymbrion (class Stellarietea mediae) in urban areas. However, a precondition for occurrences in annual communities is that frequent disturbances, essential for such vegetation types, have stopped.

Alluvial woodlands with H. mantegazzianum can partly be classified as alder-ash-gallery forests (Alnenion glutinoso-incanae, class Querco-Fagetea) along colline (100-200 m a.s.l.) to montane (500-900 m a.s.l.) rivers, or grey willow scrub (Salicion elaeagni, class Salicetea purpureae) along montane to subalpine (up to 2000 m a.s.l.) rivers. These are the most natural vegetation types of H. mantegazzianum described from Central Europe. Other woodlands in which H. mantegazzianum occurs include young forestry plantings in river valleys and pioneer forests of Populus tremula L. or Salix caprea L., for example (Sauerwein, 2004; Thiele and Otte, 2006b). It is noteworthy that almost all woodlands with H. mantegazzianum that were found during our field studies had developed from abandoned grasslands during the last 50 years (see later sections). Generally, H. mantegazzianum in woodlands is restricted to sparse canopies, gaps or margins where the species can benefit from increased light supply compared with closed canopies of forest interiors.

The frequencies of plant communities with H. mantegazzianum in the sites that we studied are presented in Fig. 8.2. H. mantegazzianum occurs with about the same frequency in grasslands and tall-herb communities, which accounted for most of the relevés, while other open vegetation types and woodlands are less represented.

Fig. 8.2. Relative frequencies of plant communities with H. mantegazzianum found at 202 sites in 20 study areas in Germany. Simplified from Thiele and Otte (2006b).

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