**3.1. Succession in species numbers**

**Figure 5** illustrates the cumulative species number for oribatid mites [24], springtails [25], and beetles and spiders [26], with increasing age of the ground. All groups showed a rapid addition of species during the first 80 years. Later, relatively few new species colonised among beetles and springtails. Oribatid mites and spiders, however, increased their cumulative species number considerably during the following 150 years. The five plots in 10,000-year-old soil had about the same number of springtail species as in 200-year-old soil, and with very few new species. Among oribatid mites, six new species were added. Beetles and spiders were not sampled in 10,000-year-old soil.

#### **3.2. Succession in dominance structure**

Another way of presenting succession is to examine the relative dominance among species. To illustrate the main changes among mites and springtails, data were lumped into the four mentioned age groups A–D (**Figure 2**), each with a similar number of sampling sites. In zone A (32–48 years), oribatids as a group made up about 80% of all mites, but this value later stabilised around 55%. The mite group Actinedida correspondingly increased their dominance in older soil, while predatory Gamasina mites were rare throughout the age gradient. In 10,000-year-old soil, the pioneer species *Tectocepheus velatus* was still present, but *Oppiella neerlandica* was now the dominant oribatid species [24].

**Figure 5.** Cumulative species number of different arthropod groups, with increasing age of the ground. Surface active beetles (Coleoptera) and spiders (Araneae) were pitfall-trapped in various vegetation types, while springtails (Collembola) and oribatid mites (Oribatida) were extracted from soil in *Salix herbacea* vegetation. From Ref. [26].

Also, the springtail community showed considerable changes in dominance structure as the soil aged [25]. Two *Folsomia* species took over the dominance in zone B (52–66 years), and later *Tetracanthella brachyura* became the most abundant species. In short, there was a '*Folsomia* front' approaching the pioneer ground, and behind it followed a '*Tetracanthella* front'. The dominance structure of springtails was surprisingly similar in zone C (72–227 years) compared to the very old soil of 10,000 years in zone D [25].

Pitfall catches of beetles and spiders indicated clear changes in community structure during the 200-year study period. This is illustrated for beetles in **Table 1**, which shows the relative catches of the 13 most common species. *Bembidion hastii* dominated the catches strongly on 3-year-old ground but was still well represented on 40-year-old ground, for then to disappear on older ground. On 63- and 79-year-old ground, the community structure was very similar, being dominated by *Amara quenseli* and *Patrobus septentrionis*. While *A. quenseli* became very rare in older sites, *P. septentrionis* increased its dominance further and represented more than half of the catches on 160-year-old ground. However, on 205-year-old ground, *Liogluta alpestris* from the Staphylinidae family took over the dominance.

**Table 2** lists the 14 most common spider species in the pitfall material. The catches on newly deglaciated ground was dominated by *Pardosa trailli, Erigone tirolensis* and *E. arctica*, while *Collinsia holmgreni* and *Hilaira* cf. *frigida* took over the dominance after 40 years. As in beetles,


**Table 1.** Dominance structure of the beetle community on the ground of different age, expressed by pitfall catches. For each species, the highest dominance value is shown in bold numbers. Species with dominance values below 5% are collectively listed under 'Other species'.



**Table 2.** Dominance structure of the spider community on the ground of different age, expressed by pitfall catches. For each species, the highest dominance value is shown in bold numbers. Species with dominance values below 5% are collectively listed under 'Other species'.

spiders showed a similar community structure on 63- and 79-year-old ground, being dominated by *Tiso aestivus, Arctosa alpigena* and *E. arctica*. After 160 years, *Scotinotylus evansi* dominated the catches, and *P. paludicola* dominated after 205 years.

#### **3.3. Do species persist after colonisation?**

**Species Family 3 yr 40 yr 63 yr 79 yr 160 yr 205 yr** *Bembidion hastii* Carabidae **81** 22 0 0 0 0 *Nebria nivalis* Carabidae **10 10** 1 2 <1 <1 *Amara alpina* Carabidae 4 **23** 4 4 4 10 *Geodromicus longipes* Staphylinidae 2 **10** 6 4 2 2 *Simplocaria metallica* Byrrhidae 1 **9** <1 <1 0 0 *Amara quenseli* Carabidae 2 0 **30** 21 <1 1 *Curimopsis cyclolepidia* Byrrhidae 0 0 **9** 3 0 0 *Nebria rufescens* Carabidae 0 1 2 **9** <1 <1 *Patrobus septentrionis* Carabidae 0 23 29 32 **54** 13 *Cymindis vaporariorum* Carabidae 0 0 5 1 **13** 1 *Liogluta alpestris* Staphylinidae 0 0 7 11 6 **34** *Anthophagus alpinus* Staphylinidae 0 0 0 1 6 **13** *Chrysomela collaris* Chrysomelidae 0 0 0 <1 2 **8** Other species 0 2 6 10 10 **16** Total percentage 100 100 100 100 100 100

Also, the springtail community showed considerable changes in dominance structure as the soil aged [25]. Two *Folsomia* species took over the dominance in zone B (52–66 years), and later *Tetracanthella brachyura* became the most abundant species. In short, there was a '*Folsomia* front' approaching the pioneer ground, and behind it followed a '*Tetracanthella* front'. The dominance structure of springtails was surprisingly similar in zone C (72–227 years) com-

Pitfall catches of beetles and spiders indicated clear changes in community structure during the 200-year study period. This is illustrated for beetles in **Table 1**, which shows the relative catches of the 13 most common species. *Bembidion hastii* dominated the catches strongly on 3-year-old ground but was still well represented on 40-year-old ground, for then to disappear on older ground. On 63- and 79-year-old ground, the community structure was very similar, being dominated by *Amara quenseli* and *Patrobus septentrionis*. While *A. quenseli* became very rare in older sites, *P. septentrionis* increased its dominance further and represented more than half of the catches on 160-year-old ground. However, on 205-year-old ground, *Liogluta alpes-*

**Table 2** lists the 14 most common spider species in the pitfall material. The catches on newly deglaciated ground was dominated by *Pardosa trailli, Erigone tirolensis* and *E. arctica*, while *Collinsia holmgreni* and *Hilaira* cf. *frigida* took over the dominance after 40 years. As in beetles,

pared to the very old soil of 10,000 years in zone D [25].

154 Glacier Evolution in a Changing World

*tris* from the Staphylinidae family took over the dominance.

**Table 1.** Dominance structure of the beetle community on the ground of different age, expressed by pitfall catches. For each species, the highest dominance value is shown in bold numbers. Species with dominance values below 5% are

collectively listed under 'Other species'.

A study of macroarthropod succession in several Norwegian glacier forelands at different altitudes and environmental conditions concluded that most species persisted after colonisation [19, 20, 22, 23]. This was regarded as a fundamental difference as compared to plant succession patterns. However, the taxonomic resolution in these studies was low in certain animal groups. For instance, in the beetle family Staphylinidae, which was represented by a high number of species in our study (21 out of 40 beetles), most species were unidentified in the studies by Vater and Matthews. The number of traps used in their studies was also low in some cases.

The more extensive material from the present case study, where all beetles and spiders were identified to species, confirmed to a large degree the hypothesis of 'adding and persistence' of species [26]. However, there were some exceptions. Among beetles, *B. hastii* disappeared when vegetation became more or less closed after about 60 years. *Simplocaria metallica* became very rare at the same time, and was not recorded after about 80 years. Likewise, the cold-adapted *Nebria nivalis* nearly disappeared after 80 years. *Curimopsis cyclolepidia* was only recorded in the range of 60–80 years. This range was also the clearly preferred for *A. quenseli*. It is interesting to note that the two last-mentioned species were not found in an extensive pitfall trapping in various neighbouring habitats of 10,000 years of age during 3 years (1969–1971) [36].

Among spiders, *P. trailli* and *E. arctica* nearly disappeared after 80 years. *A. alpigena* was numerous between 60 and 160 years but was absent after about 200 years. At 160 years, two new species appeared as very common: *P. septentrionalis* and *Ozyptila arctica*, but the first one disappeared in 200-year-old soil, and the second one nearly so.

Most soil microarthropods seemed to persist after colonisation. Among oribatid mites, the pioneer species *Liochthonius* cf. *sellnicki* was barely present after about 70 years [24]. Among springtails, the cold-loving pioneer species *Agrenia bidenticulata* gave up after about 50 years. There were several examples of rare species which 'disappeared' in older soils, but the small data do not allow firm conclusions about the presence or absence.

A general persistence of both macro- and microarthropods during succession indicates that these species have a high tolerance for each other and for changes in vegetation. Obviously, the concept of tolerance is as important as facilitation and inhibition when we try to understand succession.

#### **3.4. Relations to environmental parameters**

### *3.4.1. Parameters related to age*

A detrended correspondence analysis (DCA) showed that terrain age was strongly correlated to the distance to the glacier, increased organic content in soil and falling pH values [24]. A species biplot of a DCA for mites sorted pioneer species, seral species and late seral species rather well into groups, confirming a successional process [24]. Correspondingly, a non-metric multidimensional scaling (NMDS) plot for springtails separated well the pioneer species. However, in contrast to the mite succession, which showed considerable difference between 72–227 years and 10,000 years, the NMDS plot for springtail communities confirmed a great similarity in these two age groups [25]. Concerning beetle and spider succession, an NMDS plot showed a clear succession, and the pioneer species were best separated. Also, vegetation cover was correlated with age and distance from the glacier [26].

**Figure 6** shows a linear relation between age and thickness of the organic layer (*R* = 0.83, *F* = 38.4, *P* < 0.001). However, the variation was large. In **Figure 7**, species numbers of springtails and oribatid mites were related to the depth of the organic layer, and adapted curves indicated that species numbers tended to flatten out at about 10-mm organic layer. Pioneer microarthropod species have to be independent of an organic layer, and able to live on or close to the surface. Surface-living species are called epedaphic, litter-dwellers hemiedaphic and deeper-living species euedaphic. The two first groups typically contain larger species with eyes and pigmented body, while euedaphic species are often small, white and blind. **Figure 8** shows the number of springtail species from each of these categories (or transition

Animal Successional Pathways for about 200 Years Near a Melting Glacier: A Norwegian Case Study http://dx.doi.org/10.5772/intechopen.68192 157

**Figure 6.** Relationship between the age of soil and the thickness of the organic layer.

rare at the same time, and was not recorded after about 80 years. Likewise, the cold-adapted *Nebria nivalis* nearly disappeared after 80 years. *Curimopsis cyclolepidia* was only recorded in the range of 60–80 years. This range was also the clearly preferred for *A. quenseli*. It is interesting to note that the two last-mentioned species were not found in an extensive pitfall trapping in various neighbouring habitats of 10,000 years of age during 3 years (1969–1971) [36].

Among spiders, *P. trailli* and *E. arctica* nearly disappeared after 80 years. *A. alpigena* was numerous between 60 and 160 years but was absent after about 200 years. At 160 years, two new species appeared as very common: *P. septentrionalis* and *Ozyptila arctica*, but the first one

Most soil microarthropods seemed to persist after colonisation. Among oribatid mites, the pioneer species *Liochthonius* cf. *sellnicki* was barely present after about 70 years [24]. Among springtails, the cold-loving pioneer species *Agrenia bidenticulata* gave up after about 50 years. There were several examples of rare species which 'disappeared' in older soils, but the small

A general persistence of both macro- and microarthropods during succession indicates that these species have a high tolerance for each other and for changes in vegetation. Obviously, the concept of tolerance is as important as facilitation and inhibition when we try to under-

A detrended correspondence analysis (DCA) showed that terrain age was strongly correlated to the distance to the glacier, increased organic content in soil and falling pH values [24]. A species biplot of a DCA for mites sorted pioneer species, seral species and late seral species rather well into groups, confirming a successional process [24]. Correspondingly, a non-metric multidimensional scaling (NMDS) plot for springtails separated well the pioneer species. However, in contrast to the mite succession, which showed considerable difference between 72–227 years and 10,000 years, the NMDS plot for springtail communities confirmed a great similarity in these two age groups [25]. Concerning beetle and spider succession, an NMDS plot showed a clear succession, and the pioneer species were best separated. Also, vegetation

**Figure 6** shows a linear relation between age and thickness of the organic layer (*R* = 0.83, *F* = 38.4, *P* < 0.001). However, the variation was large. In **Figure 7**, species numbers of springtails and oribatid mites were related to the depth of the organic layer, and adapted curves indicated that species numbers tended to flatten out at about 10-mm organic layer. Pioneer microarthropod species have to be independent of an organic layer, and able to live on or close to the surface. Surface-living species are called epedaphic, litter-dwellers hemiedaphic and deeper-living species euedaphic. The two first groups typically contain larger species with eyes and pigmented body, while euedaphic species are often small, white and blind. **Figure 8** shows the number of springtail species from each of these categories (or transition

disappeared in 200-year-old soil, and the second one nearly so.

data do not allow firm conclusions about the presence or absence.

cover was correlated with age and distance from the glacier [26].

stand succession.

156 Glacier Evolution in a Changing World

*3.4.1. Parameters related to age*

**3.4. Relations to environmental parameters**

**Figure 7.** Adapted curves for the relationship between the thickness of the organic layer in soil and species numbers of springtails (Collembola) and oribatid mites (Oribatida).

**Figure 8.** Structure of the springtail (Collembola) community at different age groups of the soil. E = Edaphic species, which are surface-living. H = Hemiedaphic species, which are litter dwellers. EU = Euedaphic species, which are deeperliving soil species.

categories) in soil of different age groups. It is a bit surprising that some hemiedaphic, and even two euedaphic species were recorded already in soil of 32–48 years of age. However, their presence may not be permanent. The organic layer was absent up to 36 years, and 1–3-mm thick in 41–48-year-old plots [24]. Later, the hemiedaphic species gradually became numerous, with 14 species in the very old soil. About five euedaphic species were established already at the age of 52–66 years, and the species number in this category changed little with further age.

#### *3.4.2. A 'wet' and a 'dry' successional pathway*

Local variation in soil moisture modified the succession pattern, among both surfaceactive macroarthropods and soil-living microarthropods. Direct correlation between soil moisture measured close to single traps, and the species collected there showed that the following beetles significantly preferred moist soil*: P. septentrionis, Geodromicus longipes* and *L. alpestris*. Three other species were clearly dry-ground dwellers: *Byrrhus fasciatus, Cymindis vaporariorum* and *A. quenseli* [37]. Among spiders, *T. aestivus* is an example of a dry-ground dweller, as all of 102 specimens were collected on dry ridges with lichendominated vegetation.

In **Figure 9**, the 'noise' from varying moisture conditions was identified by separating catches of beetles from typical 'wet' and typical 'dry' traps. We see how *P. septentrionis* dominated strongly in wet sites, while *A. quenseli* dominated the catches in dry sites nearby.

Earlier studies have considered soil moisture to be the most important ecological factor for ground-living beetles in Norwegian alpine areas [38]. This is in accordance with our results. We conclude that surface-active macroarthropods followed two parallel successional trends in the foreland: a dry and a moist pathway.

Also, the succession of soil animals was affected by moisture. In the same glacier foreland, oribatid mites have been studied on dry moraine ridges of known age [18]. This allows for a comparison of the oribatid community in dry soil with neighbouring, moist snow bed soil at two age groups: 45–47 years and 66–72 years. While the generalist *T. velatus* was well represented in both dry and wet habitats, *L. lapponicus* and *Camisia horrida* occurred only on dry ridges, and *L*. cf. *sellnicki* and *C. foveolata* only in the wet snow bed. This illustrates that species within the same genus may have quite different moisture preferences.

**Figure 10** illustrates schematically wet and dry succession. Both pathways were reflected in the vegetation mosaic of the foreland. This is in accordance with studies in the Rotmoos foreland in the Austrian Alps, where the effect of local topography and exposure on various invertebrate groups was studied. The moisture regime was an important factor on a local scale, for all site ages [7].

categories) in soil of different age groups. It is a bit surprising that some hemiedaphic, and even two euedaphic species were recorded already in soil of 32–48 years of age. However, their presence may not be permanent. The organic layer was absent up to 36 years, and 1–3-mm thick in 41–48-year-old plots [24]. Later, the hemiedaphic species gradually became numerous, with 14 species in the very old soil. About five euedaphic species were established already at the age of 52–66 years, and the species number in this category changed little with

**Figure 8.** Structure of the springtail (Collembola) community at different age groups of the soil. E = Edaphic species, which are surface-living. H = Hemiedaphic species, which are litter dwellers. EU = Euedaphic species, which are deeper-

Local variation in soil moisture modified the succession pattern, among both surfaceactive macroarthropods and soil-living microarthropods. Direct correlation between soil moisture measured close to single traps, and the species collected there showed that the following beetles significantly preferred moist soil*: P. septentrionis, Geodromicus longipes* and *L. alpestris*. Three other species were clearly dry-ground dwellers: *Byrrhus fasciatus, Cymindis vaporariorum* and *A. quenseli* [37]. Among spiders, *T. aestivus* is an example of a dry-ground dweller, as all of 102 specimens were collected on dry ridges with lichen-

In **Figure 9**, the 'noise' from varying moisture conditions was identified by separating catches of beetles from typical 'wet' and typical 'dry' traps. We see how *P. septentrionis* dominated

strongly in wet sites, while *A. quenseli* dominated the catches in dry sites nearby.

further age.

living soil species.

158 Glacier Evolution in a Changing World

dominated vegetation.

*3.4.2. A 'wet' and a 'dry' successional pathway*

**Figure 9.** Effect of wet and dry ground on the structure of the beetle community. Both on 63- and 79-year-old plots, *Patrobus septentrionis* (Pa. se.) dominated on wet ground, and *Amara quenseli* (Am. qu.) on dry ground. Full names of the other species are *Amara alpina* (Am. al.), *Curimopsis cyclolepidia* (Cu. cy.), *Cymindis vaporariorum* (Cy. va.), *Geodromicus longipes* (Ge. lo.), *Liogluta alpestris* (Li. al.) and *Nebria rufescens* (Ne. ru.).

**Figure 10.** While the pioneer community is rather predictable, the further succession pattern differs in dry and wet patches. The figure shows a characteristic beetle and oribatid mite for a 'dry' and 'wet' succession, respectively.

#### **3.5. Succession of surface animals versus soil animals**

Among both surface-active macroarthropods and soil-living microarthropods, species numbers increased markedly during the first 80 years. Both groups had species that were favoured by the glacier retreat, because either they were cold-adapted (the springtail *A. bidenticulata* and the carabid beetle *N. nivalis*) or they preferred open space (the springtail *B. hortensis* and the carabid beetle *B. hastii*). Furthermore, both surface-living and soil-living animals were split into a 'dry' and a 'moist' succession pattern.

The two groups were, however, differently related to the development of vegetation. Soilliving microarthropods were favoured by the gradual development of an organic soil layer. Surface-active macroarthropods were influenced by the gradual closing of vegetation, and for some, to the appearance of food plants. While predators dominated throughout succession among macroarthropods, there were fewer predator species among microarthropods.

#### **3.6. Comparison between plant and animal succession**

Several investigators have detected a peak in plant richness early in primary succession, followed by a decline due to increased competition [4]. For instance, in the nearby foreland of Blåisen, there was an early diversity peak in proximal slopes [34]. Most arthropods, however, tend to persist after colonisation (see below), and there is no early peak in species richness.

Plant and animal succession have several features in common. Both plants and animals respond to local soil moisture, resulting in a 'dry' and a 'wet' succession. In the foreland of Blåisen, microtopography and moisture clearly affected plant succession [34].

Another similarity between botanical and zoological succession in the Finse area is that it takes at least 200 years to establish a stable "climax" community. Near Blåisen, only communities of simple structure, such as snow beds, reached a mature state after 220 years of succession [39].

Furthermore, plants with very narrow niches could attain local optima during early succession on glacier forelands and nunataks [35, 40]. Examples were *Draba cacuminum, Poa herjedalica, P. jemtlandica* and *Sagina intermedia* in the Finse area. Corresponding arthropod examples are two open space-living species: the carabid beetle *B. hastii* and the springtail *B. hortensis*, as well as two cold-loving species: the carabid beetle *N. nivalis* and the springtail *A. bidenticulata*.

A general similarity between plant and animal succession in Norwegian forelands is that the process is markedly affected by altitude and local climate. Glacier forelands in a harsh climate at high altitudes create a slow and species-poor succession, while the succession in both plants and animals is rapid and species-rich in forelands situated below the tree line [4, 19, 20, 22, 23].

## **3.7. Pioneer arthropods—a heterogenic group**

**3.5. Succession of surface animals versus soil animals**

split into a 'dry' and a 'moist' succession pattern.

**3.6. Comparison between plant and animal succession**

microarthropods.

160 Glacier Evolution in a Changing World

in species richness.

Among both surface-active macroarthropods and soil-living microarthropods, species numbers increased markedly during the first 80 years. Both groups had species that were favoured by the glacier retreat, because either they were cold-adapted (the springtail *A. bidenticulata* and the carabid beetle *N. nivalis*) or they preferred open space (the springtail *B. hortensis* and the carabid beetle *B. hastii*). Furthermore, both surface-living and soil-living animals were

**Figure 10.** While the pioneer community is rather predictable, the further succession pattern differs in dry and wet patches. The figure shows a characteristic beetle and oribatid mite for a 'dry' and 'wet' succession, respectively.

The two groups were, however, differently related to the development of vegetation. Soilliving microarthropods were favoured by the gradual development of an organic soil layer. Surface-active macroarthropods were influenced by the gradual closing of vegetation, and for some, to the appearance of food plants. While predators dominated throughout succession among macroarthropods, there were fewer predator species among

Several investigators have detected a peak in plant richness early in primary succession, followed by a decline due to increased competition [4]. For instance, in the nearby foreland of Blåisen, there was an early diversity peak in proximal slopes [34]. Most arthropods, however, tend to persist after colonisation (see below), and there is no early peak

Plant and animal succession have several features in common. Both plants and animals respond to local soil moisture, resulting in a 'dry' and a 'wet' succession. In the foreland of

Another similarity between botanical and zoological succession in the Finse area is that it takes at least 200 years to establish a stable "climax" community. Near Blåisen, only

Blåisen, microtopography and moisture clearly affected plant succession [34].

The pioneer community was an interesting mix of generalists and specialists, and of various life strategies [26, 32]. Among early springtails and mites, there were both parthenogenetic and bisexual species, and species with either a short or a long life cycle [24, 25]. Furthermore, there were open-ground species as the springtail *B. hortensis* and the carabid beetle *B. hastii*, and 'cold-loving' species represented by the springtail *A. bidenticulata* and the carabid beetle *N. nivalis*. Several generalists colonised the pioneer ground. The harvestman *Mitopus morio* is a generalist predator, with high catches throughout the whole foreland [27]. Among oribatid mites, *T. velatus* is a well-known generalist, and among springtails we can point at *Desoria olivacea* and *Isotoma viridis*. The carabid *A. alpina* and the staphylinid *G. longipes* are habitattolerant beetles, and *E. tirolensis* is a spider example. Despite differences in ecology, pioneer arthropods have certain key abilities in common: they are good dispersers and can live, eat and reproduce on barren or nearly barren ground [32].
