Do earthworms protect soil fauna from drought?

Background

Climate change (i.e. high temperature, low precipitation) is bringing more extensive soil droughts more often. During dry periods, many species inhabiting the soil retreat to deeper, moister soil layers to avoid drought stress. This vertical migration may be facilitated by earthworm activity. Earthworms dig burrows and as a result create pore volume and pore connectivity. This might allow for much more rapid vertical migration of other soil fauna through the soil. Earthworm burrowing has been researched quite extensively, especially in relation to soil structure and plant production. However, little is known about the effect of earthworms on other soil fauna. In addition, earthworms affect soil fauna in different ways which are sometimes hard to disentangle. For instance, casts and mucus produced during digging may acts as a resource for microbes and Collembola.

To understand the interaction between earthworm and soil fauna, in this project you will experiment with methods to expel earthworms from soil samples. You will design an experiment to compare the resistance of soil fauna to drought in three situations: unaffected soil, earthworm-worked soil from which earthworms are expelled and earthworm-worked soil still containing the worms. In these three situations, you will add springtails, let them settle a bit, and hit them with the drought hammer.

The aim of this internship is to assess if presence of earthworms, via their ecosystem engineering effect, affects springtail community composition.

Project goals

  • Perform an manipulative mesocosm experiment with different earthworm treatments.
  • Analyze the impact of earthworms on soil physical conditions as well as springtail community composition and functional traits.

Student responsibilities

  • Learn appropriate techniques to collect and identify earthworm species.
  • Set-up and maintenance of mesocosm experiment.
  • Add and extract springtail communities as a function of earthworm treatment.
  • Learn how to identify springtails using a microscope.
  • Perform statistical analysis of the difference in springtail communities between treatments.

Location and Timeframe

  • Laboratory work will be conducted at the VU. The VU has all the proper facilities for such manipulative mesocosm experiments.

Supervision and information

Dr. Matty Berg (Department of Ecological Science / section Animal Ecology)
E-mail:  m.p.berg@vu.nl
M: 06-12530372

Drs. Anne Krediet (Department of Ecological Science / section Animal Ecology)
E-mail: a.f.krediet@vu.nl
M: 06-26693163