**2.3. Macroarthropod sampling**

**2.2. Microarthropod sampling**

150 Glacier Evolution in a Changing World

in Southern Norway. Modified from Ref. [26].

For the study of soil-living microarthopods, which are springtails (Collembola) and mites (Acari), we chose to keep the vegetation factor as constant as possible. All soil samples were taken in *S. herbacea* vegetation, which was found throughout the gradient. This tiny shrub belongs to the pioneer plants and shows no preference for snow cover on relatively young terrain [34, 35]. However, after about 70 years, it is mainly restricted to patches where snowmelt

**Figure 2.** Aerial photograph of the glacier foreland, showing the position of moraines from 1750, 1934 and 2005. Beetles, spiders and harvestmen were sampled on the six numbered plots with the following ages: 3, 40, 63, 79, 170 and 205 years. Springtails and mites were sampled from eight plots in zone A (32–48 years), five plots in zone B (52–66 years), seven plots in zone C (72–227 years) and five plots in zone D (10,000 years). The small map shows the position of the foreland A different sampling strategy was chosen for surface-active macroarthropods, which were beetles (Coleoptera), spiders (Aranea) and harvestmen (Opiliones). Here, we aimed at collecting as many species as possible at each age, by covering a span of vegetation types. Pitfall traps were used at six sites with the following ages: 3, 40, 63, 79, 170 and 205 years. Twenty traps with a diameter of 6.5 cm were operated at each site and emptied every 2 weeks during two snowfree seasons (2007 and 2008) [26]. Traps were usually distributed in a topographic gradient from dry, lichen-dominated vegetation via an *Empetrum hermaphroditum* heath, to moist snow bed. In a nearby foreland of the same glacier (Blåisen glacier snout), these plant communities were characteristic products of succession [35]. Vegetation and the degree of cover were noted around each trap, a number of soil moisture data were taken, and catches from each trap and period were kept separate. Pitfall traps measure surface activity and not density, but they catch a high number of species and may be used in comparison between sites.

**Figure 3.** A small pond, 8 years old, in which larvae of chironomid midges assimilated ancient carbon from the sediments. From Ref. [30].

Aquatic invertebrates, for instance larvae of Chironomidae midges, were sampled from young ponds using a sieve. **Figure 3** shows a pond on an 8-year-old moraine.

#### **2.4. Sticky traps and fallout traps**

We performed extensive sampling of airborne arthropods on 3–6-year-old ground on the 2005 moraine [28]. Two types of traps were used: sticky traps and fallout traps. The sticky traps were placed on poles, up to 1-m height, and turned towards different directions. Fallout traps had their rim 5 or 11 cm above the ground to prevent surface-active arthropods to drop into them (**Figure 4**).

## **2.5. Gut content analyses**

The food choice of different species was studied by analysing their gut contents under the microscope. Crop and gut contents of beetles and harvestmen were dissected out and spread on slides, embedded in glycerol. In most springtails, gut contents could be observed in ordinary slides for species identification. The large, spherical species *Bourletiella hortensis* was squeezed on the slide to spread the gut content.

**Figure 4.** Sticky traps on a 6-year-old moraine, collecting airborne invertebrates from different directions, up to 1-m height. Inserted: open fallout trap with diameter 6.5 cm. From Ref. [28].
