ROOT ASSOCIATED FUNGI IN THE ECOSYSTEM

Current position
Associate professor at SLU, Uppsala, Sweden
Visiting scholar at Indiana University, Bloomington, 2010-2012

Research description
Fungi mediate biogeochemical processes in soil, such as carbon sequestration, decomposition, nitrogen cycling and phosphorus availability. These processes determine the long-term fertility of soils and ultimately the health of our planet. Soil fungal communities are diverse and remain largely unknown. In my research I combine molecular ecology tools with traditional culture based methods to explore the link between ecosystem functions and fungal biodiversity. This approach recently allowed us to describe the ubiquitous ancient fungal class Archaeorhizomycetes, a.k.a. Soil Clone Group 1, (Science 333, 876-879). These fungi are diverse and occur in roots and soil from most terrestrial ecosystems. Download reference sequences for Archaeorhizomycetes (Fig S3) here.

Plant symbiotic fungi, mykorrhiza, form the interface of nutrient and carbon transfer between photosynthesizing plants and the soil they grow in. As such root symbiotic fungi are central to how ecosystems respond to changing environmental conditions, i.e. moisture regimes, temperature, and nitrogen deposition.

Much of my professional interest over the last 10 years has been focused on the expansive field of Geomycology. Focusing chiefly on mechanisms of fungal weathering and the degree to which these are induced in response to nutrient limiting growth conditions. In this context, phosphorus is interesting with its low availability in soil. Phosphorus occurs in different forms from complex organic material, simpler organic compounds, adsorbed to oxides, precipitated as secondary minerals or in the form of primary minerals. These different forms of P occur in different parts of stratified soil profiles and fungi must thus employ different strategies to obtain P depending on where in the soil profile they grow. This may be an important factor forming fungal diversity below ground and functional differences between arbuscular and ectomycorrhizal fungi are interesting in the context of phosphorus availability.

Brief description of some ongoing projects
* During late 2007 and early 2008 we performed two field studies in Northern California. The overall aim was to develop a sampling and analysis procedure that allows for simultaneous analysis of fungal community composition and soil nutrient availability in small soil samples. This would enable us to analyze how fungal species diversity, functional differences between species and resource availability co-vary in soil on a scale relevant to both mycelial size and soil heterogeneity in the field. The first project was performed in collaboration with Karelyn Cruz and Prof Jill Banfield . It examines spatial and temporal variation of bacterial as well as fungal communities during a natural drying and rewetting cycle in meadow in the Angelo Coast Range Reserve. The second project was performed in collaboration with Nick Rosenstock andProf Tom Bruns. The project was performed at Point Reyes National Seashore  where the even aged Bishop Pine forest grows on different parental materials. The aim was to examine vertical distribution of ectomycorrhizal fungi in relation to soil chemical variables.

* LitCoast is a EU funded knowledge transfer project to promote exchange between forestry practice and researchers in Sweden and Lithuania. In 2008 we performed a field study, examining the correlation between fungal community and soil phosphorus though soil profiles along a transect of maturing soil profiles at the Lithuanian coast north of Palanga. Along the Lithuanian coast, beaches and dunes are planted with pine forests to prevent the movement of sand. These even aged forest stands provide an ideal setting to examine below ground community preferences in relation to organic and mineral soil substrates. Fungal communities are being analyzed by 454 sequencing.

* Developing a model system of fungal weathering using Serpula lacrymans, in collaboration with Assoc. Prof. Nils Högberg at SLU. In pilot studies we examining the demand for calcium in relation to wood degradation and found no correlation between Ca and wood decay. On the other hand we found a strong relation between Fe and wood decay. This makes sense since Fe is directly involved in the Fenton’s reaction used by fungi during wood decay (Science 333, 762-765). We now think that Serpula lacrymans weather concrete and other mineral construction materials to obtain traces of Fe rather than bulks of Ca. In parallel with the genome sequencing of Serpula lacrymans a weathering study is performed to identify the genes involved in dissolution of Goethite.

Funding
FORMAS, Carl Trygger foundation, KSLA, KVA, CF Lundström, Längmans kulturfond, Magn Bergvalls foundation.