Labelling samples and shipping them to Davos (Experimental study)

Soil processing and labelling

In each of the 24 plots, collect two soil cores (soil corer 2.5 x 10 cm) and homogenize the soil into a single sample per site. Please sieve the soil through a 2 mm mesh. Soils should be air-dried. Please send us a subsample of 200 g dry soil. Add the soil in a paper bag, label it as indicated below in Fig. 1 , and place it in two ziplock bags, which is also labelled.

**Fig. 1:** Label for soil samples. Optionally also add your own sample ID for future reference.

Aboveground biomass processing and labeling

As annual measures of productivity in each of the 24 plots, clip the aboveground plant material to 2 cm above ground level, in two 10cm x 50cm strips in one of the small plots dedicated for destructive sampling (ii, iii or iv), as described in the main experimental protocol. Collect the total aboveground biomass, dry it for 3 days at 70 °C and weigh it. Once they are dried and preferable ground a subsample of homogenized biomass of ca. 50 ml in volume (ca. 20 g of dry weight) per plot should be placed in sealed containers (ziplock bags or vials or tubes) and labelled as indicated in Fig. 2 (24 bags/vials). If you cannot grind the biomass samples you can cut the biomass sample in pieces and send us a well-mixed subsample of ca. 20 g dry weight per plot. Once bags/vials are labelled place them in a second airtight container (for example a ziplock bag), labelled with the same requirements (just without the plot information) and send it to the project coordinators. We would like to have your biomass samples every year.

**Fig. 2:** Label for biomass samples. Optionally also add your own sample ID for future reference.

Phytometer leaf samples

Dry the aboveground biomass of each phytometer in labelled paper bags, and weigh the dry biomass (as described in the protocol). Please do then combine the five replicates per species and plot (3 combined samples per plot, 72 in total), grind each of them, and send the ground biomass to Anne Kempel in Davos (ideally ground to a powder, stored in air-tight sample vials. If you do not have a grinding machine just send the combined biomass sample per species and plot). We will then measure nutrient contents in the biomass.

**Fig. 3:** Label for phytometer biomass samples.

Sending samples to the SLF Institute

Please note that a customs declaration is required for import into Switzerland. This must be attached to the outside of the parcel together with the authorisation no. 077/23 in a shipping bag. The following information is usually required for customs clearance and needs to be provided in the customs declaration:

Customs tariff number:	9999.9999 or leave field blank
Content (description, number of samples, total weight of package):	Plant material for scientific research / soil material for scientific research
Value of goods:	Transport and declaration costs
Tax rate:	0 (tax-free import)

Please enquire with your carrier if further information is required. Additionally add a copy of the permit also inside your package. Then send your samples back to the SLF Institute in Davos, Switzerland:

Anne Kempel / Julien Bota
WSL Institute for Snow and Avalanche Research SLF
Flüelastrasse 11
7260 Davos
Switzerland

Shipping should be done using a courier or post service with a tracking number. Express shipping is not required, but we need to be able to track the parcel during the shipping. Once the parcel is shipped, please write us an email to let us know about the shipment and include the tracking information. If you have any questions, do not hesitate to contact Anne or Julien.