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Title: ARTIFICIAL CLIMATE WARMING POSITIVELY AFFECTS ARBUSCULAR MYCORHIZAE BUT DECREASES SOIL AGGREGATE WATER STABILITY IN AN ANNUAL GRASSLAND

Author
item RILLIG, MATHIAS - UNIV. OF MONTANA
item Wright, Sara
item SHAW, M - CARNEGIE INSTI. OF WASH.
item FIELD, CHRISTOPHER - CARNEGIE INSTI. OF WASH.

Submitted to: Oikos
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2001
Publication Date: 3/2/2002
Citation: RILLIG, M.C., WRIGHT, S.E., SHAW, M.R., FIELD, C.B. ARTIFICIAL CLIMATE WARMING POSITIVELY AFFECTS ARBUSCULAR MYCORHIZAE BUT DECREASES SOIL AGGREGATE WATER STABILITY IN AN ANNUAL GRASSLAND. OIKOS. 2002. 97:52-58.

Interpretive Summary: Arbuscular mycorrhizal fungi grow on plant roots and provide benefits to plants and soil. Increased atmospheric carbon dioxide results in more fixation of carbon by plants, and some of this carbon is transported by roots to the arbuscular mycorrhizal fungi. Nourished by the carbon from plant roots, the fungal growth is greater under increased atmospheric carbon dioxide. This is important because the fungi produce a glue-like substance that stabilizes soils. The current paper shows what happens when there is no increase in carbon dioxide in the atmosphere, only warming of the atmosphere. Fungal growth increased, but the glue-like substance produced by the fungi decreased. Measures of soil stability also decreased. The results suggest that although there was evidence of greater production of the glue due to warming, the glue was degrading at a greater rate under higher temperature. The results could have important consequences for soil carbon storage and erosion in a warmed climate.

Technical Abstract: Despite the importance of arbuscular mycorrhizae to the functioning of terrestrial ecosystems (e.g., nutrient uptake, soil aggregation), and the increasing evidence of global warming, responses of arbuscular mycorrhizal fungi (AMF) to climate-warming are poorly understood. In a field experiment using infrared heaters, we found effects of warming on AMF after one growing season in an annual grassland, in the absence of any effects on measured root parameters (weight, length, average diameter). AMF soil hyphal length was increased by over 40% in the warmed plots, accompanied by a strong trend for AMF root colonization increase. Concentration of the soil protein glomalin, a glycoprotein produced by AMF hyphae with importance in soil aggregation, was decreased in the warmed plots, possibly suggesting an increased rate of decomposition of this protein. Soil aggregate water stability, measured for five diameter size classes, was also decreased significantly. These results indicate that ecosystem warming may have stimulated carbon allocation to AMF, but that other factors (e.g. decomposition) were important in determining the role of these symbionts in soil aggregation. These changes in soil aggregation, if widespread among terrestrial ecosystems, could have important consequences for soil carbon storage and erosion in a warmed climate.