This study was undertaken to investigate an effect of soilcovering on survival rate of spring wheat (Triticum spp. Cv. Haruyokoi) which were sown with a broadcaster in early winter. Effects of seed position (below or at soil surface) and the number of seminal roots penetrating into soil at thawing period on survival rate and yields were also investigated. The field experiment was conducted in 2003 and 2004 at the National Agriculture Research Center for Hokkaido Region. The laboratory experiment additionally investigated the effects of soil moisture (drought or wet) and root penetration into the soil on the survival rate of wheat plants in a growth chamber. In the field trial, the survival rate of the seedlings that sprouted from soil was over 90% in both years. The survival rate of the seedlings that sprouted at the soil surface were generally low, but ones that had more than two seminal roots penetrating into the soil survived better (76-90%). Yields of these plants were nearly equal to that of the plants sprouted from soil. In the laboratory experiments, drought treatment decreased not only the number of the roots that penetrated into the soil but also the survival rate of the wheat plant. These results suggested that the increasing in number of seminal roots that elongates under snow cover and roots that penetrates into the soil will decrease seedling death and increase yield of wheat that sprouted at the soil surface. Furthermore covering the seeds with soil will also increase and stabilize yield of spring wheat seeded in early winter.

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At the first report of this series, we reconfirmed the importance of the study to quantify the role of mycorrhizal fungi in forest carbon cycling. In this report, we focused on the ergosterol analysis method, a general method to quantify the biomass of fungi in ectomycorrhizal fine roots, and its procedure was detail described. Concentration of the ergosterol in ectomycorrhizal fungi is used as a conversion factor and this value has the great influence on the estimation of fungal biomass in ectomycorrhizal fine roots. We reviewed the data about conversion factor and recognized that the necessity of further data accumulations.

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We estimated the role of mycorrhizal fungi quantitatively in a Japanese red pine (Pinus densiflora) forest. We directly estimated several parameters to calculate the amount of carbon consumed by mycorrhizal fungi, such as the biomass of fungi in ectomycorrhizal fine roots and fine root biomass, and drew other parameters from the literature. Our study site, a Japanese red pine forest, was characterized by a very small ectomycorrhizal fine root biomass (only 91.0gm^-2) and small fungal content in ectomycorrhizal fine roots (2.2%) compared with the literature data. The ectomycorrhizal fine root biomass has a greater influence than the fungal content of ectomycorrhizal fine roots on the difference in fungal biomass in ectomycorrhizal fine roots among forests. The total biomass of ectomycorrhizal fungi in ectomycorrhizal fine roots and in soil was estimated to be only 10.0gm^-2. However, the total amount of carbon consumed by the production-death decomposition cycle of ectomycorrhizal fungi was estimated to be 117.0g C m^-2 year^-1, which corresponds to about 24% of carbon release from soil as soil respiration. Our estimation reconfirmed the importance of ectomycorrhizal fungi in forest carbon cycling. The carbon consumed by ectomycorrhizal fungi is not negligible, even in a stand having a very small biomass of ectomycorrhizal fungi.

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