Sample Collection and Processing
In early and late succession sites, six individual A. tenuifoliaplants were haphazardly selected for sampling. At each plant, a 1 x 1m plot was established with the plant at the center. Within each quadrant of this plot, two soil cores (3 x 15 cm) were collected from randomly selected locations, for a total of eight cores from each plant. In the late succession site six 1 x 1 m areas of open forest floor not occupied by A. tenuifolia were also sampled in the same way to examine the effect of alder presence vs. absence on the structure of Frankiaassemblages. In the lab, all nodules and roots were removed and soil from each core was homogenized through a 1 mm sieve. Sieved soil was then lyophilized to constant weight and ball-milled on a vortexer. Milled soils were pooled by location by combining 1.000 g samples from each core and homogenizing on a roller mill for ≥24 hours. In mid-succession sites, ten soil cores (2.5 cm x 15 cm) were collected from random locations within each 20 m x 20 m plot (CTL, +N, +P), and pooled using the same method as for the soil cores from the other sites.