Effects of long-term temperature and nutrient manipulation on Norway spruce fine roots and mycelia production

Aims and methods

The effects of changing climate on ectomycorrhizal (EcM) fine roots were studied in northern Sweden by manipulating soil temperature for 14 years and/or by fertilizing for 22 years. Fine root biomass, necromass, EcM root tip biomass, morphology and number as well as mycelia production were determined from soil cores and mesh bags.

Results and conclusions

The fine root biomass and necromass were highest in the fertilized plots, following similar trends in the above-ground biomass, whereas the EcM root tip biomass per basal area decreased by 22 % in the fertilized plots compared to the control. Warming increased the fine root biomass, live/dead-ratio and the number of EcM root tips in the mineral soil and tended to increase the production of EcM mycelia. Greater fine root biomass meant more EcM root tips, although the tip frequency was not affected by fertilization or warming. Significantly higher specific root length of EcM root tips indicated an increased need for nutrients in warmed and in unfertilized plots. Better nutrient supply and warmer soil temperature provide a potential to increase the flow of carbon into the soil via increased fine root biomass, but the carbon balance also depends on root turnover.