Ineffective Frankia strains in wet stands of Alnus glutinosa L. Gaertn. in The Netherlands

Nodulation experiments using Alnus glutinosa L. Gaertn. (black alder) seedlings as hosts and soil suspensions as inoculants were made to determine the presence and relative amounts of ineffective (non-nitrogen fixing but infectious) Frankia strains in 10 waterlogged soils of natural alder stands in the Netherlands. Ineffective nodules were formed with soil from six locations, while effective nodules were found at all sites. From three of these locations the majority of the nodules formed were of the ineffective type. These results suggested that ineffective strains form an important fraction of the Frankia population of wet soils under black alder vegetation. No correlation (r2, P < 0.05) was found between the distribution of these Frankia strains and single soil chemical components.