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Recently, we have also begun to study the release of carbon dioxide (CO2) from orchard and vineyard soils.  Carbon dioxide is a major greenhouse gas and we are using subtle differences in the naturally-occurring ratios of carbon isotopes to determine the source of the carbon being released from these soils. By understanding this, we can advise orchardists on management practices that will help retain carbon in the soil and reduce release of carbon dioxide to the atmosphere.


When we harvest a forest or a field crop, growth of new plants in that location depends on the soil.  Soil is a fascinating ecosystem and we have new molecular tools to help us understand it. Roots and leaf litter supply energy and organic nutrients to support a complex food web in the soil, based primarily on microbes - archaea, bacteria, and fungi.  Because soil contains three times more carbon than the atmosphere, understanding the flow of energy and carbon through these food webs  is crucial for predicting whether the changing climate will increase or decrease carbon storage in the soil .

In my lab, we use molecular and isotopic tools to study a major component of forest soil ecosystems: mycorrhizal fungi. Ectomycorrhizal fungi are symbionts of the roots of many trees; ericoid mycorrhizal fungi associate with plants in the heather family.  The fungi receive fixed carbon as sugars from the tree and provide mineral nutrients back to the roots. Because they excrete hydrolytic and oxidative enzymes into the soil, and because they can represent 30% of soil microbial biomass, ecto- and ericoid mycorrhizal fungi contribute to the breakdown of soil organic matter and the cycling of nitrogen and phosphorus. These activities influence plant/forest productivity and nutrient cycling.


Ectomycorrhizae and tree seedling nitrogen nutrition in forest restoration.
Hawkins BJ, Jones MD, Kranabetter JM. 2015.

NEW FORESTS  46: 747-771. DOI 10.1007/s11056-015-9488-2

Species turnover (β diversity) in ectomycorrhizal fungi linked to NH4+ uptake capacity.


Kranabetter JM, Hawkins B., Jones, MD., Robbins S., Dyer T., Li T. 2015.



Ectomycorrhizal fungal exoenzyme activity differs on spruce seedlings planted in forests versus clearcuts.
Walker JKM, Ward V, Jones MD.

TREES: STRUCTURE AND FUNCTION DOI: 10.1007/s00468-015-1239-7    


How does delivery of irrigation water and orchard floor management (compost, mulch) affect release of greenhouse gases, especially CO2? We are measuring carbon isotopes in CO2 released from soil to determine the contribution of various pools of soil C to the efflux. Initial results indicate that application of carbonate-rich irrigation water contributes to CO2 efflux from soils.

Oidiodendron maius is a fungus that forms ericoid mycorrhizas with plant roots, but can also grow as a free-living saprotroph where it would acquire most of its carbon by breaking down soil organic matter. We are interested in understanding whether O. maius also takes up a significant amount of carbon from soil when growing in symbiosis.  For example, this might happen during winter months when the plant symbiont is not photosynthesizing.  We will study gene regulation and isotopic composition of the fungus when growing symbiotically to address this question.

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