**3. Life on barren ground: The pioneer animals**

Several invertebrate groups are present on barren, vegetation-free ground close to the glacier boarder (Figs. 2-3). Typical representatives are springtails (Collembola) and mites (Acari), which are collectively named microarthropods, as well as beetles (Coleoptera), spiders (Araneae) and harvestmen (Opiliones). Since there is no organic layer, the pioneer invertebrates are surface active species, but they can find shelter in the crevices among stones, gravel and sand grains.

Primary Succession in Glacier Forelands:

*Agrenia bidenticulata* 84.6 24.7

activity. Flotation was used close to the ice boarder.

close to the Hardangerjøkulen glacier (Bråten & Flø, 2009).

**3.2 Pioneer mites (Acari)** 

primary succession.

**3.3 Pioner spiders (Araneae)** 

*Desoria infuscata* 15.4 1.5 6.5 *Bourletiella hortensis* 59.9 1.1

How Small Animals Conquer New Land Around Melting Glaciers 155

 Age (year) 0 3 32-36 41-47 Sampling method Flotation Pitfall Pitfall Pitfall

*Isotoma viridis* 5.2 28.3 21.3 *Lepidocyrtus lignorum* 0.4 50.0 65.3 *Desoria olivacea* 8.0 8.7 4.5 *Desoria tolya* 0.2 4.3 3.0 *Ceratophysella scotica* 0.1 1.1 6.1 NUMBER OF ANIMALS 26 1465 92 66

Table 1. Collembola sampled from young sites near the Midtdalsbreen glacier snout,

Norway. Percentage dominance of various species are given. Pitfall catches illustrate surface

Pitfall trapping near Midtdalsbreen glacier snout in Norway documented a considerable surface activity of small mites after 3 years, belonging to Actinedida (earlier called Prostigmata). Pitfalls and soil samples at 32-47 year age showed that other mite groups had then been added: Oribatida and Gamasina (Hågvar et al., 2009). Also on Svalbard and in the Alps, mites were recorded after only 2-4 years (Hodkinson et al., 2004; Kaufmann et al., 2002). Interestingly, the small, generalist oribatid species *Tectocepheus velatus* was a pioneer species both at Midtalsbreen, in another foreland at Jostedalsbreen glacier in south Norway (Skubala & Gulvik, 2005), as well as in two forelands on Svalbard (Hodkinson et al., 2004). Moreover, the species was found to be a characteristic pioneer on vegetation-free postindustrial dumps in Poland (Skubala, 2004). Also certain small species of the oribatid family Brachychthoniidae were early colonisers both in Norwegian forelands and in the industrial dumps. Maybe the pioneer community is more predictable for mites than for springtails in a

Also spiders are among the first colonisers on barren ground, both on Svalbard, in Norway and in the Alps. Pioneer spiders often belong to the family Lycosidae (wolf spiders) or Linyphiidae (sheet web spiders). Wolf spiders are robust and agile night hunters with good eyesight and hunt without constructing a web. In the Italian Alps, the wolf spider *Pardosa saturatior* is in fact living among debris on the glacier surface (Gobbi et al., 2006a). In the foreland of the Austrian Rotmoos glacier this species is a typical pioneer together with *Pardosa nigra* (Kaufmann, 2001). In several South-Norwegian glacier forelands, the genus *Pardosa* was recognized as a pioneer by Vater (2006). The species *Pardosa trailli* (Fig. 4) was identified both in several young forelands in the Jotunheimen area by Vater (2006), and

The large group of sheet web spiders are small, delicate animals which weave horizontal, sheet like webs under which they are hanging. Above the sheets the spider inserts strands, into which insects fly and fall onto the web. In two Svalbard forelands, *Erigone arctica* was found after 16 years (Hodkinson et al., 2004). The same species is also a pioneer at the

Fig. 3. Pitfall traps (with visible lids) on this barren, three year old moraine trapped many species of spiders, beetles, springtails and mites. Photo: Sigmund Hågvar.

### **3.1 Pioneer springtails (Collembola)**

Table 1 lists pioneer springtails collected close to Midtdalsbreen glacier snout, which is a part of Hardangerjøkulen glacier in alpine south Norway. Pitfall catches from young ground illustrate the relative surface activity at ages 3, 36 and 47 years, while flotation a few meters from the ice edge (age 0 years) proved the presence of two species on freshly exposed ground (Fig.2). One of these, *Agrenia bidenticulata*, is characteristic for cold, moist habitats in arctic and alpine areas (Fjellberg, 2007). This specialized species disappeared already after 30-40 years, at which time two generalist species dominated the surface activity: *Lepidocyrtus lignorum* and *Isotoma viridis*. Table 1 also shows an intermediate phase after 3 years, where the surface activity was dominated by the large, sphere-formed species *Bourletiella hortensis,*  and as much as eight species were already present. This case illustrates the great colonisation ability of springtails, how both specialists and generalists participate, and how the community structure may undergo rapid changes during the first few years. Although the Collembola fauna is different in forelands on Svalbard (Hodkinson et al., 2004) and in the Austrian Alps (Kaufmann et al., 2002), the colonisation pattern has certain features in common in these threes geographical sites: Springtails were among the earliest colonisers with a documented presence after only 2-4 years, and Isotomidae and Hypogastruridae were often pioneer families.


Table 1. Collembola sampled from young sites near the Midtdalsbreen glacier snout, Norway. Percentage dominance of various species are given. Pitfall catches illustrate surface activity. Flotation was used close to the ice boarder.

#### **3.2 Pioneer mites (Acari)**

154 International Perspectives on Global Environmental Change

Fig. 3. Pitfall traps (with visible lids) on this barren, three year old moraine trapped many

Table 1 lists pioneer springtails collected close to Midtdalsbreen glacier snout, which is a part of Hardangerjøkulen glacier in alpine south Norway. Pitfall catches from young ground illustrate the relative surface activity at ages 3, 36 and 47 years, while flotation a few meters from the ice edge (age 0 years) proved the presence of two species on freshly exposed ground (Fig.2). One of these, *Agrenia bidenticulata*, is characteristic for cold, moist habitats in arctic and alpine areas (Fjellberg, 2007). This specialized species disappeared already after 30-40 years, at which time two generalist species dominated the surface activity: *Lepidocyrtus lignorum* and *Isotoma viridis*. Table 1 also shows an intermediate phase after 3 years, where the surface activity was dominated by the large, sphere-formed species *Bourletiella hortensis,*  and as much as eight species were already present. This case illustrates the great colonisation ability of springtails, how both specialists and generalists participate, and how the community structure may undergo rapid changes during the first few years. Although the Collembola fauna is different in forelands on Svalbard (Hodkinson et al., 2004) and in the Austrian Alps (Kaufmann et al., 2002), the colonisation pattern has certain features in common in these threes geographical sites: Springtails were among the earliest colonisers with a documented presence after only 2-4 years, and Isotomidae and Hypogastruridae

species of spiders, beetles, springtails and mites. Photo: Sigmund Hågvar.

**3.1 Pioneer springtails (Collembola)** 

were often pioneer families.

Pitfall trapping near Midtdalsbreen glacier snout in Norway documented a considerable surface activity of small mites after 3 years, belonging to Actinedida (earlier called Prostigmata). Pitfalls and soil samples at 32-47 year age showed that other mite groups had then been added: Oribatida and Gamasina (Hågvar et al., 2009). Also on Svalbard and in the Alps, mites were recorded after only 2-4 years (Hodkinson et al., 2004; Kaufmann et al., 2002). Interestingly, the small, generalist oribatid species *Tectocepheus velatus* was a pioneer species both at Midtalsbreen, in another foreland at Jostedalsbreen glacier in south Norway (Skubala & Gulvik, 2005), as well as in two forelands on Svalbard (Hodkinson et al., 2004). Moreover, the species was found to be a characteristic pioneer on vegetation-free postindustrial dumps in Poland (Skubala, 2004). Also certain small species of the oribatid family Brachychthoniidae were early colonisers both in Norwegian forelands and in the industrial dumps. Maybe the pioneer community is more predictable for mites than for springtails in a primary succession.

#### **3.3 Pioner spiders (Araneae)**

Also spiders are among the first colonisers on barren ground, both on Svalbard, in Norway and in the Alps. Pioneer spiders often belong to the family Lycosidae (wolf spiders) or Linyphiidae (sheet web spiders). Wolf spiders are robust and agile night hunters with good eyesight and hunt without constructing a web. In the Italian Alps, the wolf spider *Pardosa saturatior* is in fact living among debris on the glacier surface (Gobbi et al., 2006a). In the foreland of the Austrian Rotmoos glacier this species is a typical pioneer together with *Pardosa nigra* (Kaufmann, 2001). In several South-Norwegian glacier forelands, the genus *Pardosa* was recognized as a pioneer by Vater (2006). The species *Pardosa trailli* (Fig. 4) was identified both in several young forelands in the Jotunheimen area by Vater (2006), and close to the Hardangerjøkulen glacier (Bråten & Flø, 2009).

The large group of sheet web spiders are small, delicate animals which weave horizontal, sheet like webs under which they are hanging. Above the sheets the spider inserts strands, into which insects fly and fall onto the web. In two Svalbard forelands, *Erigone arctica* was found after 16 years (Hodkinson et al., 2004). The same species is also a pioneer at the

Primary Succession in Glacier Forelands:

Photo: Oddvar Hanssen.

**3.6 Other pioneer groups** 

**4. Dispersion: How to get there?** 

How Small Animals Conquer New Land Around Melting Glaciers 157

Vater (2006) found the following carabid species in various foreland sites younger than 20 years: *Amara alpina, A. quenseli, Nebria nivalis,* and *Bembidion fellmanni.* The same species were pioneers close to Hardangerjøkulen glacier, except for another *Bembidion* species: *B. hastii* (Bråten & Flø, 2009, Fig. 5). In the Austrian Alps, Kaufmann (2001) recorded *Amara quenseli*, four *Nebria* species and a *Bembidion* species as early colonisers, and also Gobbi et al.

Fig. 5. *Bembidion hastii,* a pioneer predatious Carabidae beetle in Norwegian glacier foreland.

On a four year old barren moraine at Hardangerjøkulen glacier in South Norway, extraction of soil samples revealed the presence of Rotatoria and at least five different Nematoda genera. Tardigrada was found close to a single plant of *Poa alpina* (Christer Magnusson, pers. comm). In Austria, Kaufmann et al. (2002) found both Nematoda and Enchytraeidae in soil samples younger than 40 years. On Svalbard, Hodkinson et al. (2004) recorded larvae

Pioneer invertebrate species must be good dispersers, but our knowledge in this field is limited. The easiest dispersion would be by air, either by active flight, by passive wind transport, or a combination. On Svalbard, areal dispersal of invertebrates over the foreland of Midtre Lovénbreen glacier was studied by Coulson et al. (2003). Large numbers of Diptera, Hymenoptera and Araneae were caught in water and sticky traps, some only 15 m

of terrestrial Chironomidae after 2 years and Enchytraeidae after 37 years.

(2006a) recorded *A. quenseli* as a pioneer species in the Italian Alps.

Hardangerjøkulen glacier in South Norway, being recorded on a three year young moraine (Bråten & Flø, 2009). A related species, *Erigone tirolensis*, is a common pioneer at the Hardangerjøkulen glacier and in the Rootmostal foreland in Austria (Bråten & Flø, 2009; Kaufmann, 2001).

Fig. 4. The large and fast-running wolf spider *Pardosa trailli* is a pioneer species in Norwegian glacier forelands. Photo: Sigmund Hågvar.

#### **3.4 Pioneer harvestmen (Opiliones)**

*Mitopus morio* is a large and very active species which is common on newly exposed ground, less than 20 years old, in several South-Norwegian forelands studied by Vater (2006). Bråten & Flø (2009) found it abundantly on a three year old moraine close to Hardangerjøkulen glacier in south Norway. Together with *M. glacialis*, the species is also a pioneer in the Alps (Kaufmann, 2001).

#### **3.5 Pioneer beetles (Coleoptera)**

While beetles were absent in the forelands studied on Svalbard (Hodkinson et al., 2004), they belonged to the pioneers in all studies in Norway and the Alps. A characteristic picture is that species within the family Carabidae are present on barren ground close to the glacier. Moreover, certain genera, and even species, are common pioneers in these two geographical areas. Typical genera in this respect are *Nebria, Amara* and *Bembidion*. In South Norway,

Hardangerjøkulen glacier in South Norway, being recorded on a three year young moraine (Bråten & Flø, 2009). A related species, *Erigone tirolensis*, is a common pioneer at the Hardangerjøkulen glacier and in the Rootmostal foreland in Austria (Bråten & Flø, 2009;

Fig. 4. The large and fast-running wolf spider *Pardosa trailli* is a pioneer species in

*Mitopus morio* is a large and very active species which is common on newly exposed ground, less than 20 years old, in several South-Norwegian forelands studied by Vater (2006). Bråten & Flø (2009) found it abundantly on a three year old moraine close to Hardangerjøkulen glacier in south Norway. Together with *M. glacialis*, the species is also a pioneer in the Alps

While beetles were absent in the forelands studied on Svalbard (Hodkinson et al., 2004), they belonged to the pioneers in all studies in Norway and the Alps. A characteristic picture is that species within the family Carabidae are present on barren ground close to the glacier. Moreover, certain genera, and even species, are common pioneers in these two geographical areas. Typical genera in this respect are *Nebria, Amara* and *Bembidion*. In South Norway,

Norwegian glacier forelands. Photo: Sigmund Hågvar.

**3.4 Pioneer harvestmen (Opiliones)** 

**3.5 Pioneer beetles (Coleoptera)** 

(Kaufmann, 2001).

Kaufmann, 2001).

Vater (2006) found the following carabid species in various foreland sites younger than 20 years: *Amara alpina, A. quenseli, Nebria nivalis,* and *Bembidion fellmanni.* The same species were pioneers close to Hardangerjøkulen glacier, except for another *Bembidion* species: *B. hastii* (Bråten & Flø, 2009, Fig. 5). In the Austrian Alps, Kaufmann (2001) recorded *Amara quenseli*, four *Nebria* species and a *Bembidion* species as early colonisers, and also Gobbi et al. (2006a) recorded *A. quenseli* as a pioneer species in the Italian Alps.

Fig. 5. *Bembidion hastii,* a pioneer predatious Carabidae beetle in Norwegian glacier foreland. Photo: Oddvar Hanssen.
