Below ground studies of roots using minirhizotrons

by Marie Frost Arnda

Minirhizotron and ITEX chamber, Disko Island. Photo Marie Forst Arndal July2013

Research into climate change effects has focussed much on the aboveground effects, while belowground effects are less studied. Especially root studies in the Arctic are difficult and few have looked into root dynamics. The root:shoot ratio in Arctic is 6.6, hence roots are an extremely important component of arctic ecosystems, and belowground competition is likely greater than aboveground.

The aim of the project is to investigate the effects of increased snow accumulation, removal of aboveground shrub biomass and seasonal warming on root dynamics. In order to investigate this, minirhizotrons and ingrowth cores will be used.

In the summer of 2012 and 2013 we installed minirhizotrons in the experimental site in Disko, West Greenland (96 minirhizotrons in total), and in Svalbard, Norway (24 minirhizotrons).

Minirhizotron, Svalbard. Photo Marie Forst Arndal, summer 2013

Minirhizotrons are transparent acrylic tubes installed in the soil, and are a non-destructive method where birth and death of individual roots can be followed through time with a root scanner. The use of minirhizotrons makes it possible to measure root diameter, length, branching, orientation and root hairs on individual roots, and by repeated measurements it is possible to follow roots for several years and estimate longevity.

Schematic drawing of minirhizotron installed in soil

All minirhizotrons were installed at an angle of 45 degrees, and the maximum vertical depth was 70 cm. In the ‘Dry snowfence site’ in Disko is was only possible to reach a max depth of 30 cm due to stones, while in the other sites the minirhizotrons were installed into the permafrost.

Soil samples were taken in connection with minirhizotron installation, to get an estimate of the root biomass in the beginning of the experiment.

In June and in August 2013 we scanned all 24 minirhizotrons in Svalbard. In Disko we did our measurements in June, July and August, covering the mail growing season. The images will be digitized in Copenhagen and the individual roots can then be followed through time. The root scanning will continue in 2014, where we also hope to see some effect of the experimental treatments.

If you want to know more, contact Marie Frost Arndal.