Nitrophobic ectomycorrhizal fungi are associated with enhanced hydrophobicity of soil organic matter in a Norway spruce forest

[摘要] In boreal forests an important part of the photo assimilates are allocatedbelowground to support symbiosis of ectomycorrhizal fungi (EMF). Theproduction of EMF extramatrical mycelium can contribute to carbon (C)sequestration in soils, but the extent of this contribution depends on thecomposition of the EMF community. Some species can decrease soil C stocks bydegrading soil organic matter (SOM), and certain species may enhance soil Cstocks by producing hydrophobic mycelia which can reduce the rate of SOMdecomposition. To test how EMF communities contribute to the development ofhydrophobicity in SOM, we incubated sand-filled fungal-ingrowth mesh bagsamended with maize compost for one, two or three growing seasons innon-fertilized and fertilized plots in a young Norway spruce ( Picea abies ) forest. Wemeasured hydrophobicity as determined by the contact angle and the C / N ratiosin the mesh bags contents along with the amount of new C entering themesh bags from outside (determined by C 3 input to C 4 substrate), and relatedthat to the fungal community composition. The proportion of EMF speciesincreased over time to become the dominant fungal guild after three growingseasons. Fertilization significantly reduced fungal growth and altered EMFcommunities. In the control plots the most abundant EMF species was Piloderma olivaceum , which was absent in the fertilized plots. The hydrophobicity of themesh bag contents reached the highest values after three growing seasons onlyin the unfertilized controls plots and was positively related to theabundance of P. olivaceum , the C / N ratios of the mesh bag contents and the amount of new Cin the mesh bags. These results suggest that some EMF species are associatedwith higher hydrophobicity of SOM and that EMF community shifts induced byfertilization may result in reduced hydrophobicity of soil organic matter,which in turn may reduce C sequestration rates.

[学科分类] 大气科学