Soil diaspore reserves above the timberline in the Austrian Alps

ARTICLE IN PRESS

Flora 203 (2008) 292–303 www.elsevier.de/flora

Soil diaspore reserves above the timberline in the Austrian Alps Brigitte Klug-Pu¨mpela,, Gabriele Scharfetter-Lehrlb a

Department of Integrative Biology and Biodiversity Research, Institute of Botany, BOKU, University of Natural Resources and Applied Life Sciences, Gregor-Mendel-Straße 33, A-1180 Vienna, Austria b Plankenmaisstr.15, A-1220 Vienna, Austria1 Received 1 February 2007; accepted 30 April 2007

Abstract Soil diaspore reserves are considered to support self-healing processes after vegetation disturbances. Therefore, the stratified reserves of viable diaspores in superimposed soil layers of four sites above the timberline in the Austrian Alps were assessed. At each site, a semi-natural (‘‘undisturbed’’) extensive alpine pasture and the disturbed vegetation on hiking trails were investigated. Eighty soil cores in total (corresponding to 400 slices, each representing a 1-cm layer between 0 and 5 cm depth) were taken in autumn and subjected to germination tests after vernalization. The total diaspore numbers in disturbed and undisturbed plots did not differ significantly, but all undisturbed soils contained higher species numbers than disturbed ones. Seed shape and size clearly influenced the vertical distribution. Intact soils showed a significant decrease in big/long diaspores with increasing soil depth. Disturbances influenced the aboveground species composition and therefore the distribution of seeds of different size. In case of disturbances, the restriction of most big seeds to superficial layers means a threat for small populations of rare and protected species such as Viola lutea subsp. sudetica with relatively big seeds near the soil surface. When the disturbances stop, the diaspore communities might initiate a first, but with respect of landscape protection and preservation of species diversity insufficient step of vegetation restoration. r 2008 Elsevier GmbH. All rights reserved. Keywords: Disturbances; Restoration; Seed bank structure; Subalpine/alpine pasture vegetation; Trampling; Viola lutea ssp. sudetica

Introduction Seed banks and seed dispersal are important not only in population biology (Bakker et al., 1996), but especially also in restoration ecology at high altitudes (Chambers et al., 1987; Urbanska and Fattorini, 1998a, b). One issue of subalpine and alpine restoration ecology is to establish – as quickly and sustainably as Corresponding author. Tel.: +43 1 47654 3158; fax: +43 1 47654 3180. E-mail address: [email protected] (B. Klug-Pu¨mpel). 1 Private address.

0367-2530/$ - see front matter r 2008 Elsevier GmbH. All rights reserved. doi:10.1016/j.flora.2007.04.005

possible – a plant layer fit for the extreme conditions of areas tending to erosion. Florineth (1992) and Krautzer et al. (2000) showed the importance of adapted seed mixtures for eco-engineering in the alpine zone of Austria and South Tyrol. Welling (2002) stated that in subarctic Finland, the existence of a well-developed seed bank alone does not guarantee a successful local regeneration of a species; rather, factors as plant traits and vegetation structure must be taken into account. The longevity of seeds is considered to depend on seed size and therefore on phylogeny (Thompson et al., 1993), on life history, vertical distribution in the soil, resistance against pathogens, and seed predation

ARTICLE IN PRESS B. Klug-Pu¨mpel, G. Scharfetter-Lehrl / Flora 203 (2008) 292–303

(Thompson et al., 1998). Seed burial experiments (Schwienbacher and Erschbamer, 2001) revealed a marked reduction of germinability compared with unburied, ‘‘fresh’’ seeds. According to Bekker et al. (1998), the vertical distribution of seeds in the soil is correlated with shape and size of the seeds, and it seems logical to expect the oldest (germinable) seeds in the deepest soil layers. Hitherto, only a few studies have dealt with alpine or arctic soil seed banks, and hardly any with the vertical seed bank structure of autochthonous plant species that could regenerate their populations from their seed banks. Most likely these diaspore communities reflect not only the aboveground vegetation and the life traits and seed quality of its components, but probably also site-specific variables such as slope, aspect, soil properties, and anthropogenic impacts. Chambers (1993) gave an overview over life history strategies and seed fates of tundra species, and emphasized the importance of soil quality and burial depth for the germinability of buried seeds. Diemer and Prock (1993) compared two diaspore communities in the Alps to one of a Scandinavian subarctic plant community and found remarkable differences in the amount of viable seeds, yet without taking into account that seed density might depend on burial depth. Bernhardt (1996) reported on the diaspore community of a Seslerio-Caricetum sempervirentis in the Alps, but did not differentiate either between more superficially stored and buried seeds. The dominance of Sedum atratum in the investigated plots confirmed the findings of other authors that therophytes store many small seeds in the soil. Erschbamer et al. (2001) studied two superimposed soil layers of a glacier foreland in Tyrol, and found smaller species numbers in the deeper soil layer (2–6 cm) than in the uppermost layer. The total number of seeds per layer, however, did not differ substantially. According to the preliminary character of their study, the authors pointed out that high variability within sites and low overall seed store may indicate the absence of a real seed bank on younger moraine material. Hatt (1991) restricted the depth of soil sampling above 2300 m a.s.l. in the Swiss Alps to 5 cm, as alpine soils are usually very shallow and/or stony. His results show also a very uneven horizontal distribution of seeds. Recent research on an artificial ski run in St. Anton/Arlberg, Austria, revealed the accumulation of up to 30,000 seeds m2 in the uppermost 2 cm of the previously seed-free substrate within 5 years, whereas the soil layer from 2 to 4 cm contained roughly ten times fewer seeds (Klug, 2006). Increasing summer tourism provides several erosion hazards in connection with mountaineering or mountain biking (Cole and Monz, 2002; Klug et al., 2002; KlugPu¨mpel and Scharfetter, 1998). The loss of seed banks by erosion is one consequence, and one should be prepared for offering sustainable remedies.

293

In the present study, we wanted to test the hypothesis that burial depth is independent from seed size and shape. Homogenous burial would mean a certain advantage in case of beginning erosion. Therefore, this study aimed also to reveal trends in the vertical structure of soil diaspore communities in the central and eastern parts of the Eastern Alps where touristic activities and their impacts on vegetation and soils have steadily increased since more than 50 years.

Materials and methods In the autumn of two subsequent years, soil samples were taken in four regions above the present timberline of the Austrian Alps. Two regions (F ¼ Fischerhu¨tte, Niedere Tauern, and R ¼ Rax, Northern Calcareous Alps) had calcareous soils; two (S ¼ Stuhleck, Central Alps, and E ¼ Edelrautehu¨tte, Niedere Tauern) had siliceous substrate. In each of the regions, one sampling plot was chosen in semi-natural (‘‘undisturbed’’), extensively grazed vegetation, and one in disturbed areas with trampled, compacted and/or eroding soils. Table 1 gives an overview over the study sites, each of which was divided into two plots. All undisturbed plots were covered by semi-natural, extensively grazed vegetation. The disturbed plots had compacted or hardly any litter and compacted soils, and, in three of four cases, a markedly lower and more open plant cover than the undisturbed vegetation. At Edelrautehu¨tte, a trail led through a Deschampsia cespitosa–Festuca varia community on a flat terrace upon siliceous soil. The seminatural vegetation ended abruptly where the soil was compacted, tending towards pseudogley, with a compacted litter layer and reduced species number. At Stuhleck, the trail was steeper, and erosion had already washed away the humus. The geological and climatic peculiarities of the Rax plateau in the easternmost Northern Alps are responsible for the species-rich and attractive flora there (Dirnbo¨ck and Greimler, 1997). The more intensive cattle grazing of former times has been replaced more recently by other utilizations like summer tourism and skiing. The community of the undisturbed plot resembled a Seslerio-Semperviretum enriched by alpine pasture plants. Trampling had formed some parallel trails where the plants were crippled, and the cover was more open. At Fischerhu¨tte, a calcareous vein of rocks crossed underneath the hardly inclined trail. The vegetation was a mosaic of MolinioArrhenatheretea and Seslerietea species enriched by some tall herbs and Salicetea herbaceae species. The broad trail showed hardly any erosion and was covered by a dense layer of Poa supina. The vegetation around and on the trails was documented by phytosociological

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Table 1.

B. Klug-Pu¨mpel, G. Scharfetter-Lehrl / Flora 203 (2008) 292–303

The study regions, their characteristics, and plant species composition aboveground and in the soil diaspore bank

Geographic situation

Siliceous sites

Calcareous sites

Edelrautehu¨tte Rottenmanner Tauern, Central Alps, 1980 m a.s.l.

Stuhleck Easternmost Central Alps, 1780 m a.s.l.

Rax Easternmost Calcareous Alps, 1560 m a.s.l.

Festuca varia–Deschampsia cespitosacommunity Intact

Similar

Alpine pasture, wind-swept

Few turf tufts

Open

Intact

Brown soil

Compacted brown soil

Brown soil

Heavily disturbed Sandy gravel

Alpine pasture species rich Intact

Litter

Undisturbed

Undisturbed

Erosion Cover percentage (herb layer) Average vegetation height (cm) Approximate seed (diaspore) density, calculated for 1 m2

 95

Compacted, scarce + 40

25

21,000

Vegetation layer

Structure of vegetation Soil

Rendzina

Similar

Open

Fischerhu¨tte Radsta¨dter Tauern, Central Alps, 2050 m a.s.l. Alpine pasture with tall herbs Intact

Poa supina mat

Dense

Rendzina, compacted organic layer Scarce

Shallow rendzina

Intact

Rendzina, compacted organic layer Compacted

+ 85

 98

/+ 90

 100

Almost absent ++ 60

Absent shallow  100

4

20

7

15

5

15

3

11,000

26,000

34,000

14,000

7000

6000

30,000

Erosion: ++:-strong; +: initial; : hardly any erosion. ‘‘Similar’’: similar species composition but many species less frequent.

releve´s using the Londo (1976) scale (decimal scale: number ¼ 1/10 of average coverage of vegetation). Ten soil cores were taken from every undisturbed and disturbed plot using a cylindrical soil auger with 7 cm diameter. Total sampling depth did not exceed 5 cm because of the stony and shallow soils especially at the disturbed sites. The numerous stones in the underlying soil layers prevented the sampling of intact and stable cores with comparable soil volumen. The lateral distance between samples varied from 20 to 50 cm, maximum distance within one plot not exceeding 500 cm. The intact upright cores in open-top bags were placed in fridge boxes, transported to the laboratory and stored in the dark at 1 to 3 1C during winter. In spring, the cores were cut exactly into 1-cm slices. Loose litter particles were added to the uppermost slice, and loose soil particles to the slices they had fallen from. Each slice was evenly spread on fleece and sand in a styropores tray. Rhizomes and roots in the trays were rinsed and then removed to prevent re-sprouting. The soil layers in the trays were not thicker than 0.5 cm.

The 400 trays were placed in the greenhouse. Temperature was kept above 10 1C; during very hot days, it rose to 40 1C. To simulate mid summer day length, we added 16 h of artificial daylight. The samples were watered automatically, and their moisture was controlled frequently. For 100 days, the germination of seeds and sprouting of bulbs were recorded daily. After that time, the germination rates dropped. Thereafter, the samples were stirred to move buried seeds to the surface. Seedling emergence was then controlled every second day for two more months until germination ceased completely. Most of the seedlings were moved into bigger trays with sterilized substrate and placed in the garden before identification to species or genus level. For every seedling the day of emergence, sample, and layer were recorded. A few seedlings died before identification. After the germination experiment, the trays with highest and lowest seedling numbers were examined under a binocular to detect dead or dormant seeds. A subsequent germination test with these few seeds, however,

ARTICLE IN PRESS B. Klug-Pu¨mpel, G. Scharfetter-Lehrl / Flora 203 (2008) 292–303

Frequency of seed numbers per sample

300

250

200

150

100 Mean = 9,8797 Std. Dev. = 20,23991 N = 399

50

0 0

100 150 50 Frequency classes of seeds per sample

Fig. 1. Histogram of seed numbers of 399 out of 400 samples (i.e. five soil depths each from 10 undisturbed and 10 disturbed soil cores from actually four sites; one extremely outlaying sample from site Fischerhu¨tte containing 343 seeds is omitted). Total mean (9.9) is considerably lower than standard deviation (20.2), and evidently the most frequent seed numbers per sample are low, belonging to the two lowest frequency classes. This distribution pattern allows the application of nonparametric statistical tests. The line represents normal distribution.

showed that they were no longer viable. Seedlings were determined after Csapody (1968) and Muller (1978); nomenclature follows Fischer et al. (2005). Seed dimensions were either taken from seeds found in the experiment, or – where not enough intact seeds were available – taken from informations given by Hegi (1906–2003) and Beijerinck (1947). The attribution of species to phytosociological classes follows Mucina (1993) whenever possible. The data set was subject to various descriptive statistical procedures (Tremp, 2005); histograms and stem–leaf analyses showed that the data did not follow an ideal Gauss distribution (Fig. 1). Consequently, non-parametric rank um tests (Ko¨hler et al., 1996; Wilcoxon, 1945) were used for concluding procedures. For these, seed and species numbers were summed up for soil depth 0–2 and 2–4 cm to reduce cases without any seeds.

Results Table 1 shows average plant height and cover percentage of semi-natural and trampled vegetation, and the number of viable diaspores in the respective plots. Total diaspore numbers at the undisturbed sites

295

on calcareous bedrock varied between 6000 (Fischerhu¨tte) and 14,000 m2 (Rax). In siliceous soils, we found 21,000 and 26,000 m2 seeds, respectively. The trampled calcareous soils contained between 7000 and 30,000 seeds m2, and the disturbed siliceous soils 11,000 and 34,000 seeds m2. A closer inspection (see the appendix) shows that at Fischerhu¨tte many species, probably of the former, undisturbed vegetation, were found in a remarkably species rich diaspore community underneath the dense P. supina mat on the trail. At Stuhleck, where erosion had washed away the humus, only few species were found exclusively in the diaspore bank, above all Calluna vulgaris, with comparatively small seeds. In Table 2, the total number of germinated seeds in all 400 soil slices was attributed to either disturbed or undisturbed plots. Fifty-six percent of all seeds were big (41 mm), 44% small (o1 mm, independent of shape). Neither total number nor different size groups showed significant differences between disturbed vs. undisturbed plots. Highly significant differences, however, were noted between seed numbers in the uppermost 2 cm and the underlying 2 cm of soil, regardless of geological preconditions. Furthermore, higher portions of small seeds at a site led to non-significant differences between the seed numbers in the two superimposed layers. Especially at site E, where more than 80% of the seeds were small, the vertical distribution of seeds was more or less even; in cases with many big seeds, as for instance at plots F-D (Fischerhu¨tte, disturbed), there was a significant decrease in seed numbers with increasing soil depth (see also Fig. 2). Table 3 provides details on seed and species numbers at the eight plots. A drastic decrease with increasing soil depth was detected for species with big/long seeds but not for small-seeded plant species. The latter were only few, but many of them had produced a rich seed bank even in the deepest soil layer. Table 4 lists some selected species with different seed size and their presence as seeds in all five distinct soil slices. P. supina had a huge amount of big/long seeds in the superficial layers of the disturbed site F-D. This species, showing the above mentioned seed traits, revealed a more or less superficial bank recruited from fresh seeds almost throughout the growing season. Alchemilla spp. were present at three sites, and some of these big seeds could also penetrate to deeper layers. Potentilla aurea, a plant with big but more isodiametric seeds, was also widespread and could penetrate to all layers; yet it was 5–6 times more numerous in undisturbed soil. The seeds of the rare and potentially endangered Viola lutea ssp. sudetica found at the sampling site Edelrautehu¨tte occurred more superficially as well. Only 50% of the undisturbed samples contained V. sudetica seeds, and 80% of those were restricted to the uppermost layer. Only one seed (in one of 10 samples) was

ARTICLE IN PRESS 296

Table 2.

B. Klug-Pu¨mpel, G. Scharfetter-Lehrl / Flora 203 (2008) 292–303

Results of Wilcoxon rank sum tests. n seeds: refers to absolute seed numbers in the respective sample numbers

n n n n n n n n n n n n n n n n n n

Seeds total Big seeds Small seeds Seeds all sites Seeds siliceous sites Seeds calcareous sites Seeds site E total Seeds site E big Seeds site E small Seeds site S total Seeds site S big Seeds site S small Seeds site F total Seeds site F big Seeds site F small Seeds site R total Seeds site R big Seeds site R small

n n n n n n n n

Seeds Seeds Seeds Seeds Seeds Seeds Seeds Seeds

E disturbed E undisturbed S disturbed S undisturbed F disturbed F undisturbed R disturbed R undisturbed

n Seeds

% of total

Variables tested

N cases

Asymptotic significance

5739 3224 2525 5739 3508 2231 1210 151 1059 2298 1171 1127 1389 1259 130 842 643 199

100 56 44 100 61 39 100 12 88 100 51 49 100 91 9 100 76 24

Undist/disturbed Undist./disturbed Undist./disturbed Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm Soil depth 0–2/2–4 cm

80 40 40 160 80 80 40 20 20 40 20 20 40 20 20 40 20 20

0.198 0.112 0.840 0.000 0.001 0.000 0.261 0.002 0.492 0.004 0.000 0.632 0.000 0.000 0.003 0.001 0.005 0.153

n.s. n.s. n.s. *** ** *** n.s. ** n.s. ** *** n.s. *** *** ** ** ** n.s.

% Small seeds 91 86 70 22 7 24 14 28

Soil Soil Soil Soil Soil Soil Soil Soil

20 20 20 20 20 20 20 20

0.602 0.456 0.016 0.037 0.001 0.001 0.005 0.046

n.s. n.s. * * ** ** ** *

depth depth depth depth depth depth depth depth

0–2/2–4 cm 0–2/2–4 cm 0–2/2–4 cm 0–2/2–4 cm 0–2/2–4 cm 0–2/2–4 cm 0–2/2–4 cm 0–2/2–4 cm

Levels of significance: *po0.05; **po0.01; ***po0.001.

found 2–3 cm below the surface of the undisturbed plot, whereas six seeds originated from 0 to 1 cm. The disturbed samples contained no seeds of this species at all. C. vulgaris at Edelrautehu¨tte was rather evenly dispersed, horizontally as well as vertically. Its seed numbers were significantly higher in undisturbed soils. Attributing species to syntaxonomic classes (Table 5), we note that Molinio-Arrhenatheretea diaspores were well represented at all sites and in all soil types. Many of them occurred above- and belowground. On siliceous soils they were accompanied by mainly Caricetea curvulae species at the undisturbed sites. Trampling, however, had negative effects on the presence of species within the seed bank. On calcareous undisturbed soils Seslerietea species found above- and belowground contributed 14% to the total species number; 18.6% of all Seslerietea species at these sites, however, did not have a seed bank. Disturbance reduced the fraction of aboveground Seslerietea species markedly and increased the portion of species represented only by a seed bank. The few Salicetea herbaceae species present aboveground, but without noticeable diaspore reserves, were almost completely absent under disturbance.

Discussion Our results provide basic data about high-altitude seed reserves and their vertical and horizontal distribution in the soil. The diaspore densities in this experiment are higher than in the studies by Chambers (1993), Diemer and Prock (1993), or Niederfriniger Schlag and Erschbamer (1995) who ran their experiments in alpine/nival ecosystems. Taking into account that samples by Bernhardt (1996) from 2250 m a.s.l. in Liechtenstein comprised 10 cm depth (ours only 5 cm), the seed reserve there was nevertheless higher, as the samples contained excessively many small seeds of mainly S. atratum, a therophyte species. The seed density at higher altitudes (especially on recent substrates such as moraines or artificial ski tracks) can vary from a handful to some thousands per square meter (Klug, 2006; Niederfriniger Schlag and Erschbamer, 1995; Urbanska and Fattorini, 1998a, b). Our data support the assumption that soil diaspore communities above the timberline are structured very unevenly, not only horizontally, but also vertically. They strongly reflect anthropogenic impacts: Species that suffer from trampling develop less aboveground biomass and fewer or no generative ramets (Klug et al., 2002). Caricetea curvulae

ARTICLE IN PRESS B. Klug-Pu¨mpel, G. Scharfetter-Lehrl / Flora 203 (2008) 292–303

Stuhleck:

Edelrautehütte: 100 80 60

297

soil layer 0-2 cm soil layer 2-4 cm

120

soil layer 02 cm soil layer 24 cm

U

100 80

U D D

60 40

40

20

20 U 0

0 BIG

BIG

SMALL seed size

Rax:

Fischerhütte: 140

soil layer 02 cm soil layer 24 cm

120 100 80

SMALL seed size

U 60

40

U

60 40

soil layer 02 cm soil layer 24 cm

80

U

20

U U

20 0

0 BIG

SMALL seed size

BIG

SMALL seed size

Fig. 2. Box plots showing median and out layers for diaspore reserves at four sites in two superimposed soil layers (0–2 and 2–4 cm soil depth) for two seed size classes in disturbed and undisturbed soils; y-axis represents seed numbers derived from 20 soil cores of 7 cm diameter at each site; out layers: U ¼ undisturbed, D ¼ disturbed. One extreme out layer at Fischerhu¨tte (D) is omitted.

and Loiseleurio-Vaccinietea species lose their diaspore reserves by erosion and their vitality by trampling and disappear with time from the disturbed vegetation. Others vanish from aboveground but their seed bank persists under trails with moderate trampling. When the disturbance ceases, the seed bank can – to a certain extent – provide natural restoration. Increasing erosion, however, will reduce the population of these species on trails by destroying also the superficially stored seeds. This has probably come true for Viola alpina ssp. sudetica, a rare and endangered species at Edelrautehu¨tte, as well as for the endemic Dianthus alpinus at site Rax. Robust species like D. cespitosa or the trampling-resistant P. supina and Sagina spp. invade the trails instead. At Rax, the disturbances have led to a reduction of species found exclusively in the diaspore community. Slightly less vegetated than the adjacent undisturbed

site, the trail may already have lost species by the first self-healing attempts of the vegetation: seedlings of pioneer species of the Seslerio-Semperviretum with a superficial seed bank may have been destroyed by repeated trampling until their seed bank was exhausted. Uneven vertical distribution in the soil of P. supina seeds – occurring mainly in calcareous soils – and deep penetration of the small Calluna or Sagina seeds into the siliceous soils support the opinion that seed size and shape are responsible for quality and quantity of the soil seed reserve. High amounts of seeds in the uppermost soil layer, however, can also be a consequence of intensive seed rain (Erschbamer et al., 2001; Klug, 2006). Seed rain of P. supina and Sagina occurs almost throughout the growing season. On the other hand, Calluna is not present in the adjacent undisturbed aboveground vegetation, let alone on the trails, but very abundant as seeds in

Subplot

298

Table 3.

Distribution of seed and species numbers found at four undisturbed and four disturbed plots, and their attribution to two seed size classes Seed size

n Species/ n Seeds/ Number of seeds in layer per plot plot plot Layer 0–2 cm

E disturbed Big/ long E disturbed Small

% Of plot

Layer 2–4 cm

% Of plot

Number of species in layer per plot

Layer 4–5 cm

% Of plot

Layer 0–2 cm

% Of total

Layer 2–4 cm

% Of total

Average number of seeds per species Layer 4–5 cm

% of total

Layer 0–2 cm

Layer 2–4 cm

Layer 4–5 cm

18

4

14

3

3

1

5

71

4

57

1

14

3.6

3.5

3.0

3

377

154

37

139

34

84

20

3

100

2

67

2

67

51.3

64.5

42.0

Sum 10 E Big/ 18 undisturbed long E Small 4 undisturbed

412 116

172 90

42 11

153 21

37 3

87 5

21 1

8 17

94

6 6

33

3 3

17

5.3

3.7

1.7

682

285

36

262

33

135

17

4

100

4

100

4

100

71.3

65.5

33.8

Sum 22 F disturbed Big/ 9 long F disturbed Small 5

798 1091

375 1035

47 89

283 49

36 5

140 7

18 1

21 6

67

10 7

78

7 3

33

172.5

7.0

2.3

77

47

4

21

2

9

1

4

80

4

80

3

60

11.8

5.0

3.0

Sum 14 F Big/ 12 undisturbed long F Small 6 undisturbed

1168 168

1082 133

93 60

70 27

7 12

16 8

2 4

10 10

83

11 7

58

6 4

33

13.3

3.9

2.0

53

39

18

14

6

0

0

6

100

5

83

0

0

6.5

2.8

0.0

Sum 18 R disturbed Big/ 14 long R disturbed Small 2

221 241

172 163

78 58

41 58

18 21

8 20

4 7

16 12

86

12 7

50

4 5

36

13.6

8.3

4.0

40

28

10

8

3

4

1

2

100

2

100

2

100

14.0

4.0

2.0

Sum 16 R Big/ 24 undisturbed long R Small 2 undisturbed

281 402

191 240

68 43

66 114

24 20

24 48

8 9

14 22

92

9 14

58

7 8

33

10.9

8.1

6.0

159

85

15

56

10

18

3

1

50

2

100

1

50

85.0

28.0

18.0

561 400

325 310

58 24

170 70

30 5

66 20

12 2

23 10

91

16 7

64

9 5

45

31.0

10.0

4.0

916

273

21

421

32

222

17

3

75

4

100

4

100

91.0

105.3

55.5

1316 771

583 591

44 60

491 146

37 15

242 34

19 3

13 12

92

11 11

85

9 5

38

49.3

13.3

6.8

211

59

6

133

14

19

2

1

25

3

75

4

100

59.0

44.3

4.8

982

650

66

279

29

53

Sum 26 S disturbed Big/ 11 long S disturbed Small 4 Sum 15 S Big/ 13 undisturbed long S Small 4 undisturbed Sum 17

Figures refer to a soil surface area of 384 cm2 (surface area of 10 samples).

5

13

14

9

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ARTICLE IN PRESS B. Klug-Pu¨mpel, G. Scharfetter-Lehrl / Flora 203 (2008) 292–303

Table 4.

299

Distribution of seeds of selected species in different layers of undisturbed and disturbed soils

Undisturbed L+0–1 cm

Disturbed 1–2 cm

Poa supina (big, long) E 0 0 S 0.26 0 R 0.52 0 F 4.68 1.56

2–3 cm

L+0–1 cm

1–2 cm

0 0.26 0.26 0.26

0 12.73 19.49 230.74

5.2 0 10.13 1.82

0.78 0 4.94 0.78

0 0 0 0.26

Potentilla aurea (big,+/isodiam.) E 3.19 1.82 3.38 S 0.52 0.52 0 R 2.86 2.86 8.58 F 1.56 1.56 1.56 Alchemilla spp. (big) E 0 S 36.9 R 6.24 F 0

3–4 cm 0 0 0 0

4–5 cm

2–3 cm

3–4 cm

4–5 cm

0 4.94 3.9 31.96

0 3.9 1.04 7.02

0 3.9 6.5 3.12

0 3.38 3.64 1.04

0.52 0 0.26 0.26

0.52 0 1.3 0

0.26 0 7.8 0

0.26 0 0 0.52

0 0 0.26 0.52

0 1.56 1.04 0

0 0.26 0.52 0

0 42.62 5.46 0.78

0 10.13 2.08 0.26

0 1.56 2.34 0

0 1.3 4.42 0

0 6.76 1.82 0

0 1.82 7.8 0.26

0 4.16 1.04 0.52

Calluna vulgaris (small) E 37.42 27.02

28.84

27.54

27.28

19.49

16.11

15.85

16.9

21.57

Viola lutea subsp. sudetica (big) E 1.56 0

0.26

0

0

0

0

0

0

0

Dianthus alpinus (big) R 0.52

0.26

0

0

0

0

0

0

0

0

Figures are calculated as average values for a soil surface of 100 cm2. E, S: sites with siliceous bedrock; R, F: sites with basic bedrock. L: litter layer.

Table 5. Percentage of species with diaspore reserves (‘‘+D’’), without diaspore reserves (‘‘D’’), and present in the seed bank only (D only), at siliceous and calcareous sites, and their attribution to syntaxonomic classes Syntaxonomic class

Siliceous soils

Calcareous soils

Undisturbed

Disturbed

Undisturbed

Disturbed

‘‘+D’’ ‘‘D’’ D only ‘‘+D ‘‘D’’ D only ‘‘+D’’ ‘‘D’’ D only ‘‘+D’’ ‘‘D’’ D only Molinio-Arrhenatheretea 15.4 Caricetea curvulae 21.2 Calluno-Ulicetea 1.9 Loiseleurio-Vaccinietea 1.9 Scheuchzerio-Caricetea fuscae 1.9 Mulgedio-Aconitetea 0 Salicetea herbaceae 0 Festuco-Brometea 0 Seslerietea albicantis 0 Thlaspietea rotundifolii 0 Carici rupestris–Kobresietea bellardii 0 Asplenietea 0 Without attribution 3.8

7.7 11.5 3.8 1.9 1.9 0 0 0 0 0 0 0 1.9

13.5 5.8 3.8 3.8 0 0 0 0 0 0 0 0 1.9

25.6 15.4 0 0 0 0 0 0 0 0 0 0 0

12.8 17.9 5.1 0 0 0 0 0 0 0 0 0 0

7.7 2.6 7.7 2.6 0 0 0 0 0 0 0 0 2.6

18.6 1.4 2.9 0 1.4 0 4.3 0 14.3 0 1.4 0 0

14.3 2.9 1.4 0 1.4 0 2.9 1.4 18.6 5.7 0 0 2.9

0 0 1.4 0 1.4 1.4 0 0 0 0 0 0 1.4

16.7 0 4.2 0 2.1 0 2.1 0 6.3 0 0 0 4.2

20.8 0 0 0 0 2.1 2.1 2.1 10.4 4.2 0 2.1 2.1

6.3 2.1 0 0 0 2.1 0 0 4.2 0 2.1 0 2.1

Figures show percentages of species number per plot.

the siliceous soils. Like other dwarf shrubs, Calluna is sensitive to mechanical disturbance (Bayfield, 1979; Cole and Monz, 2002). Sagina spp., however, adapted to

disturbances, are found in the seed bank and in the aboveground vegetation of disturbed subalpine/alpine substrates (Klug, 2006).

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The restoration of plant covers on eroding subalpine/ alpine soils could be initiated by species with persistent seed banks. In many cases, however, these species are neither characteristic for the adjacent vegetation nor rare and endangered. Being aware of that, one should not rely only on the self-healing capacity of subalpine and alpine turfs, which recover very slowly. Without preventing new shortcuts, and without applying welladapted seeds or sods of the autochthonous vegetation on eroding trails, one will be confronted with problems similar to artificial ski tracks sooner or later.

At the siliceous sites, dense trail vegetation is absent and erosion stronger. The uppermost disturbed soil layers are decapped remainders of the former profile and represent a formerly deeper stratum. Deeper layers, however, are hardly reached by grass achenes and bigger dicot seeds. This means hazards for, e.g., V. lutea ssp. sudetica: Bonn and Poschlod (1998) mention only a few meters as maximum seed dispersal distance for Viola species when the capsule opens. Clumped dispersal and superficial diaspore banks are bad preconditions for endangered plants in times of increasing disturbances and shrinking refugial areas. Seeds of V. lutea ssp. sudetica, quite frequent in the undisturbed vegetation, are completely absent in disturbed soil. Our findings confirm the statement by Jensen (1998) on abandoned wet meadows that ‘‘rare or endangered species are scarcely ever found in the seed bank.’’ Similar findings are reported by Eichberg et al. (2006) for inland sand vegetation. Poschlod (1993) emphasized that Potentilla species can show innate or induced dormancy, the latter due to unfavorable environmental conditions. Most likely, P. aurea and Alchemilla species belong to this group. Yet whereas P. aurea plants are evenly distributed in the undisturbed (and partly in the disturbed) aboveground vegetation, Alchemilla species display high sociability and thus a more uneven distribution. The total amount of Alchemilla seeds is therefore higher than that of Potentilla and highest in the uppermost layers. Moderate trampling may serve as scarification for their hard-coated seeds, or it may drive them into deeper layers.

Acknowledgments We dedicate this paper to Ernst Scharfetter and thank him for his indispensable help in the field. Fonds zur Fo¨rderung der wissenschaftlichen Forschung in O¨sterreich (FWF) provided financial support for Project No. 10143-BIO. H. Strelec and B. Spangl helped with statistics; H. Richter, P. Hietz, and M. Koch contributed useful comments, our garden staff (namely G. Wagner) and many eager students helped with practical work. Thanks to all!

Appendix Aboveground species cover (estimated after Londo 1976) and species presence in soil diaspore reserves (D) are shown in Table A1.

Table A1 Species

Attribution to phytosociological class

Undisturbed vegetation Sites E

(A) On siliceous soils Leontodon helveticus Juncus trifidus Carex sempervirens Festuca varia Agrostis rupestris Potentilla aurea Alchemilla monticola, A. xanthochl. Cardaminopsis halleri Avenella flexuosa Luzula spp. Cerastium holosteoides Campanula scheuchzeri Avenula versicolor Deschampsia cespitosa Poa supina

Caricetea curvulae Caricetea curvulae Seslerietea albicantis Nardetea/Caricetea curvulae Caricetea curvulae Caricetea curvulae Molinio-Arrhenatheretea Molinio-Arrhenatheretea Nardetea strictae Molinio-Arrhenatheretea Molinio-Arrhenatheretea Caricetea curvulae Molinio-Arrhenatheretea Molinio-Arrhenatheretea

2 1 2 2 0.4 0.1

S

2

0.4 2

D (E) Y Y Y Y

0.2

Y YY YY

0.1 0.1

0.1 0.1

0.1 0.1

0.2

Sites E

4 0.4 1 2

2 0.2 0.2

Disturbed vegetation

Y Y Y Y Y Y Y Y

S

0.1

D (E )

(S)

0.1 0.2

0.1 0.1 2 0.2

0.1

0.2

0.1

Y Y Y

7

Y YY YY

0.2

Y

0.1

Y Y Y

1 0.2

Y Y

0.2 0.1 0.1 0.1 2 0.1

1 1

0.4

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301

Table A1. (continued ) Species

Attribution to phytosociological class

Undisturbed vegetation Sites E

Trifolium repens Anthoxanthum alpinum Poa chaixii Taraxacum officinale s.l. Ranunculus acris Vaccinium myrtillus Viola lutea ssp. sudetica Gentianella germanica agg. Euphrasia picta Sagina procumbens Festuca nigrescens Leontodon autumnalis Plantago major Hypericum maculatum Calluna vulgaris Campanula barbata Leucanthemum vulgare Loiseleuria procumbens Agrostis capillaris Nardus stricta Veronica alpina Epilobium sp. Poa annua Pulsatilla alpina s.l. Gentiana acaulis Calamagrostis villosa

Molinio-Arrhenatheretea Caricetea curvulae Molinio-Arrhenatheretea Molinio-Arrhenatheretea Molinio-Arrhenatheretea Loiseleurio-Vaccinietea Nardetea strictae Nardetea/Seslerietea Molinio-Arrhenatheretea Molinio-Arrhenatheretea Molinio-Arrhenatheretea Molinio-Arrhenatheretea Molinio-Arrhenatheretea Nardetea strictae Loiseleurio-Vaccinietea Nardetea strictae Molinio-Arrhenatheretea Loiseleurio-Vaccinietea Molinio-Arrhenatheretea Nardetea strictae Molinio-Arrhenatheretea

Soldanella sp. Plantago major Sagina procumbens

D (E)

1 0.1 0.2 0.1 0.4 0.1 * 0.2 0.1 1

Sites E

Y Y Y Y Y Y Y Y Y Y Y

(E )

1

0.1 0.1

0.2 0.4

YY Y Y Y Y Y Y Y Y Y Y Y F

R

D

F

Molinio-Arrhenatheretea

0.2

3

YY

*

Seslerietea albicantis Molinio-Arrhenatheretea Molinio-Arrhenatheretea Caricetea curvulae Molinio-Arrhenatheretea Molinio-Arrhenatheretea Caricetea curvulae Molinio-Arrhenatheretea Seslerietea albicantis Molinio-Arrhenatheretea Seslerietea albicantis

1 0.2 3 0.4 0.4 1 0.1 0.4 0.1 0.4

0.1 1

Y YY Y Y Y Y Y Y Y Y Y

Molinio-Arrhenatheretea Molinio-Arrhenatheretea Caricetea curvulae Molinio-Arrhenatheretea Stellario nemorum– Geranietea sylvat.

* 0.2 * * 1

Molinio-Arrhenatheretea Molinio-Arrhenatheretea

S

D (S) 0.4 0.1 0.4 0.1 0.2

Y

1 2

Y Y Y Y Y YY Y Y Y Y Y Y

0.1

Molinio-Arrhenatheretea Caricetea curvulae Nardetea strictae Loiseleurio-Vaccinietea

(B) On calcareous soils Alchemilla micans, A. monticola Carex sempervirens Campanula scheuchzeri Leontodon hispidus Anthoxanthum alpinum Agrostis capillaris Deschampsia cespitosa Campanula barbata Festuca nigrescens Carex capillaris Persicaria vivipara Cerastium arvense ssp. strictum Cerastium holosteoides Agrostis stolonifera Potentilla aurea Ranunculus montanus Poa supina

S

Disturbed vegetation

0.1

0.2 1

1 0.2 0.2 0.1 0.1 * 1 1

* * *

0.1

0.2 *

YY Y YY Y Y

*

Y Y YY

0.4

5

R

(R)

D Y

0.1 0.1 0.1 0.1 0.1

0.1 * * 0.1 0.1

0.1

0.1

0.1

0.1

0.1

*

0.1 3

* 0.1

0.1

0.1

0.1

*

Y Y

Y Y Y Y Y

Y Y Y Y YY Y Y YY

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Table A1. (continued ) (B) On calcareous soils Tofieldia calyculata Sesleria albicans Gentiana verna Leontodon autumnalis Ranunculus acris Agrostis alpina Dianthus alpinus Euphrasia salisburgensis Galium anisophyllon Gentiana clusii Luzula alpinopilosa Luzula campestris Trifolium badium Gentiana nivalis Thymus praecox ssp. polytrichus Luzula sp. Hieracium cf. lactucella Hypericum maculatum Saxifraga sp. Parnassia palustris Calluna vulgaris

F Scheuchzerio-Caricetea nigrae Seslerietea albicantis Seslerietea albicantis Molinio-Arrhenatheretea Molinio-Arrhenatheretea Molinio-Arrhenatheretea Seslerietea albicantis Seslerietea albicantis Seslerietea albicantis Seslerietea albicantis Loiseleurio-Vaccinietea Molinio-Arrhenatheretea Molinio-Arrhenatheretea Seslerietea albicantis Festuco-Brometea

0.2 0.1

R

D

F

0.2

Y

*

0.2 * 0.2 0.1 0.2

0.2 0.2 0.1

0.1 *

Y Y Y Y Y Y Y Y Y Y

0.1 2 0.1 0.4

Molinio-Arrhenatheretea Loiseleurio-Vaccinietea

(R)

D Y Y

0.1

0.1 0.1 0.1 0.2

0.1 0.1 * *

0.1 0.1 0.1

* * 0.1

0.1 0.1

* 0.1

*

0.1 2 0.1 0.1

Nardetea strictae

R

Y Y Y Y

Y Y Y Y Y Y Y Y

*Species present at the site but not in the releve´ (in brackets: releve´s near, but not at the soil sampling plots). YY: over 1000 seeds m2 of species in respective diaspore bank; Y: less than 1000 seeds m2 in diaspore bank. E: Edelrautehu¨tte; S: Stuhleck (siliceous sites). F: Fischerhu¨tte; R: Rax (calcareous sites). Species without D in siliceous soils: 14. Species without D in calcareous soils: 37.

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