PARENT SESSION
Tuesday, August 8, 8:00-11:30 am
OOS 3 - Functional roles of fine roots and mycorrhizal fungi in carbon and nutrient cycling
Ballroom C, Ballroom Level, Cook Convention Center
Organized by: EA Hobbie (erik.hobbie@unh.edu) and JE Hobbie

This session will address techniques for quantifying the roles of fine roots and mycorrhizal fungi in carbon/nutrient cycling.

Carbon flux to soil via ectomycorrhizal fungi in different ecosystems.

Wallander, Håkan^*,1, ¹ Department of Microbial Ecology, Lund University, Lund, Sweden

ABSTRACT- Most forest trees are forming symbiotic relationship with ectomycorrhizal (EM) fungi. A substantial proportion of photosynthetic products are allocated to the fungal symbionts which form an extensive mycelial network in the soil fuelled by the photosynthetic activity of the trees. The fertility of the soil is a major factor determining the carbon allocation to the EM fungi. In general, a low availability of N and P results in more carbon allocated to the EM fungi and a more extensive external mycelial network produced in the soil, which improves N and P uptake. We have developed an in-growth mesh bag method to quantify production of EM mycelia in different forest ecosystems. Our main objectives have been to 1) quantify the production of EM mycelia in different forest ecosystems 2) estimate the influence of different mineral sources on growth of EM mycelia, 3) estimate the effects of different nutritional status of the forest on growth of EM mycelia. We have found that up to 600 kg of ectomycorrhizal mycelia can be produced per ha in a Norway spruce forests as well as in a mixed Norway spruce Pedunculate oak forest on an annual basis. Similar estimates in another Norway spruce forests with a more intensive sampling strategy demonstrated a daily production of 7 kg EM mycelia per hectare. Further estimates from this study will reveal to what extent this mycelia decompose during the winter. Recent studies indicate that EM mycelia can be the dominant pathway through which carbon enter the soil organic matter pool exceeding both the input via leaf litter and fine root turnover in a Poplar plantation. Investigations of Norway spruce forests on peaty soil in Finland have revealed that forests with low K and P status produce more EM mycelia than forests with adequate P and K status.

Key words: boreal forest, mycorrhiza, carbon flux