Effects of elevated temperature and precipitation on the diversity and functioning of the microbial communities in temperate soils.

 

Aim:

 

The aim of the project is to make an experimental investigation of effects of global heating on bacterial and protozoan diversity in soil and the accompanying changes in the degradation of indigenous soil organic matter and xenobiotics (pesticides).

 

Background:

 

The continuing emisssion of greenhouse gasses, which leads to an increasing global heating, is expected to cause higher mean annual temperatures as well as higher precipitation levels in the northern temperate areas. The combination of these factors will result in significantly changed life conditions for the soil microbial communities. Microbial communities in Denmark are subject to regular freezing/thawing and drying/rewetting cycles, which are known to kill microbial biomass and to stimulate degradation of physically protected organic matter. The climate changes will reduce the amplitude and frequency of these cycles; we expect that these changes will cause an altered microbial community, and a slower degradation of organic substances in soil. Conversely, the generally higher mean annual temperature will tend to stimulate this breakdown. Hence, the effects of global heating on microbial diversity and functioning are not straightforward to predict and need to be investigated experimentally.

 

Project Description

 

The purpose of the project is to perform laboratory experiments with artificially induced freezing/thawing and drying/rewetting cycles, as well as various moisture regimes on material from topsoil layers collected from arable land. The diversity changes of the microbial communities in the soil, mainly bacteria and their protozoan grazers, will subsequently be examined. Part of the diversity studies will specifically address pesticide-degrading organisms. Functional studies will deal with the mineralization of indigenous soil organic matter as well as selected pesticides in soils subdued to the treatments described above. Parallel to the diversity studies, the soil ability to mineralise indigenous soil organic matter and added pesticides will be investigated. The project will form a natural part of an ongoing collaboration between Department of Terrestrial Ecology, (Zoological Institute, University of Copenhagen, Associate Professor Flemming Ekelund), and the Department of Geochemistry, Geological Survey of Denmark and Greenland (GEUS. Senior Scientist Carsten Suhr Jacobsen).

 

Methodology

 

The diversity among soil microorganisms will initially be examined by means of conventional culture-based techniques, combined with typing and microscopy. Major emphasis will be on molecular work: Extraction of soil DNA, PCR-amplification of relevant genes - mostly SSU rDNA -, DGGE, cloning and sequencing. The mineralization studies will be based on gas chromatography and mass spectrometry as well as liquid scintillation counting of radiolabelled material.

 

Contact person: Flemming Ekelund, Department of Terrestrial Ecology, Zoological Institute, Universitetsparken 15, DK-2100 Copenhagen , phone: 35 32 12 75, Email: [email protected]