Elements and ectomycorrhizal symbiosis affecting the growth of Japanese larch seedlings regenerated on slopes of an active volcano in northern Japan

Key message The growth of Japanese larch seedlings is regulated by the presence of nutrients as well as ectomycorrhizal symbiosis. The mountain slope of an active volcano is a severe environment for the regeneration of larch ( Larix kaempferi Sarg. hereafter larch) seedlings. To determine parameters affecting the growth of larch seedlings, we analyzed stoichiometry of elements in the soils and plant organs, ectomycorrhizal (ECM) colonization, and photosynthetic abilities. These parameters were compared with two different elevations. From nutrient analysis of plant organs from larch seedlings grown on the slope of a volcano, potassium (K) was insufficient compared with the seedlings grown in other habitats. Symbiosis with ECM fungi enabled the uptake of nutrients, especially phosphorous (P) and nitrogen (N). The main factor affecting the differences in relative height growth rate (RHGr) of larch was attributed to ECM colonization. There was a positive relationship between ECM colonization and concentrations of P or N in needles. Larch seedlings with high rates of ECM colonization showed high concentrations of P and N, and had high photosynthetic rates. At lower elevation sites, concentrations of N and K in needles were low with high density of individuals. Moreover, larch showed a high accumulation of aluminum (Al) and iron (Fe) even though the amount of these elements in the soil was small. These seedlings exhibited a suppressed photosynthetic rate and RHGr. Symbiosis with ECM fungi could suppress the excessive uptake of Al and Fe.