Mycorrhizae and growth of white fir seedlings in mineral soil with and without organic layers in a California forest

Abstract

White fir (Abiesconcolor (Gord. et Glend.) Lindl.) seedlings appear to survive and grow better in mineral soil alone than in mineral soil with organic layers. To determine whether the better growth observed in seedlings in mineral soil (M), compared with those in mineral soil with organic layers (MO), could be related to the incidence of mycorrhizae in their root systems, natural M and MO seedlings were examined from five sites in the north central Sierra Nevada. Statistical analysis of the data showed that seedling dry weight was significantly related to total length of roots, number of main lateral roots, and presence of mycorrhizae on the roots. Dry weight, total length of roots, total number of mycorrhizal tips, and number of mycorrhizal tips per centimetre of roots were significantly higher for M compared with MO seedlings. Age, number of main lateral roots, and number of mycorrhizal tips per centimetre of roots are highly significant in distinguishing M from MO seedlings. The data indicate that mycorrhizae play an important role in the growth of white fir seedlings, and that both growth and presence of mycorrhizae are favored by the absence of organic layers.