Soil nitrogen availability varies with plant genetics across diverse river drainages

Understanding covariance of plant genetics and soil processes may improve our understanding the role of plant genetics in structuring soils and ecosystem function across landscapes. We measured soil nitrogen (N) and phosphorus (P) availability using ion exchange resin bags within three river drainages across Utah and Arizona, USA. The three drainages spanned more than 1,000 km in distance, 8° of latitude, and varying climatic regimes, but were similarly dominated by stands of Populus fremontii (S. Watts), P. angustifolia (James), or natural hybrids between the two species. Soil N availability was consistently greater in P. fremontii stands compared to P. angustifolia stands, and hybrid stands were intermediate. However, we found that the influence of overstory type on soil P availability depended on the river drainage. Our study suggests that, even with a near doubling of mean soil N availability across these drainages, the relative genetic-based effects of the dominant plant on N availability remained consistent. These results expand upon previous work by: 1) providing evidence for linkages between plant genetic factors and ecosystem function across geographic scales; and 2) indicating that plant genetic-based effects on nutrient dynamics in a given ecosystem may differ among nutrients (e.g., N vs. P).