The overall goal of our research is to identify the mechanisms that drive the selection and activity of the bacterial community active in Arctic soils, which are characterized by extreme conditions, such as long periods of low temperatures and multiple episodes of freezing and thawing. Global climate warming is predicted to affect these environments most severely and temperature-induced changes in the soil and wetland microbial activities are expected to have a profound impact in the future. Increased mineralization of accumulated carbon may make these environments as additional sources of carbon dioxide, but the consequences of elevated temperatures may be far more complex than can currently be predicted. Despite the critical role of Arctic and boreal soil microbial communities, very little is known about their composition, activity and distribution. Freeze-thaw cycles are thought to be a major physical driving force for microbial activity in polar, soil environments. However, it is not known which members of the microbiota are active in carbon turnover, for example during the burst of respiration typically observed after freeze-thaws. The microbial community that survives and is active will likely have a profound impact on the type and amount of organic carbon and nitrogen being mineralized.
We are investigating the seasonal and spatial variations of microbial communities in Arctic soils of Finnish Lapland. Molecular and cultivation-based analyses suggest that the bacterial communities in Arctic fjeld and forest soils of northern Finland are stable and highly resilient. Members of the Acidobacterium, Bacteroidetes and Alphaproteobacteria, among others, are key members of the dominant and resilient heterotrophic soil microbiota (Männistö and Häggblom 2006; Männistö et al. 2007). Analysis of soil microcosms after freeze-thaw cycles indicated that there was not a major die-off of the dominant members of the soil community. Freeze-thaw cycles thus appear to have limited direct effect on the overall bacterial community structure, which corresponds to the relatively stable communities observed at some sites over many years. However, there appears to be a major difference in which bacteria were active in carbon utilization. We are currently assessing the selection mechanisms promoting the dominance of key species in changing temperature regimes. Our research will advance our knowledge of the relationship between microbial community composition and activity and environmental conditions in Arctic soil environments. This study will also have broader impact by providing a basis for predicting the effect of long-term temperature changes and global warming on microbial activity in Arctic soils.
Researchers: Minna Männistö, Naglaa Mohammed, Suman Rawat and Jennifer McConnell
Publications:
Männistö MK, Tiirola M, Häggblom MM (2007) Microbial communities in Arctic fjelds of Finnish Lapland are stable but highly pH dependent. FEMS Microbiology Ecology 59:452-465.
Männistö MK, Häggblom MM (2006) Characterization of psychrotolerant bacteria from Finnish Lapland. Systematic and Applied Microbiology 29:229-243.
Funding: Academy of Finland and
National Science Foundation
Collaborators:
Minna Männistö, Finnish Forest Research Institute, Finland
http://www.metla.fi/pp/5620/index-en.htm
Marja Tiirola, University of Jyväskylä, Finland
Pia Vuorela, Åbo Akademi University, Finland
Lee Kerkhof, Rutgers, Institute of Marine and Coastal Sciences
http://marine.rutgers.edu/main/IMCS-People-Details/People-Details-Lee-J.-Kerkhof.html
Nikolai Panikov, Dartmouth College, Thayer School of Engineering
