DOI: 10.5061/dryad.4f4qrfjbt
title: Isotopic data from: Coupled shifts in ectomycorrhizal communities and plant uptake of organic nitrogen along a soil gradient: an isotopic perspective

description: Plants associating with mutualistic ectomycorrhizal (ECM) fungi may
 directly obtain nitrogen (N) bound in soil organic matter (N-SOM).
 However, the contribution of N-SOM to plant growth under field conditions
 remains poorly constrained. We tested the hypothesis that turnover in ECM
 communities along soil inorganic N gradients mediates a functional
 transition from plant reliance on N-SOM in low inorganic N soils, to
 primarily inorganic N uptake in inorganic N rich condition soils. We
 quantified the d15N of Q. rubra foliage and roots, organic and inorganic
 soil N pools, and used molecular sequencing to characterize ECM
 communities, morpho-traits associated with N-foraging, and a community
 aggregated sporocarp d15N. In support of our hypothesis, we document the
 progressive enrichment of root and foliar d15N with increasing soil
 inorganic N supply; green leaves ranged from -5.95‰ to 0.16‰ as the supply
 of inorganic N increased. ECM communities inhabiting low inorganic N soils
 were dominated by the genus Cortinarius, and other fungi forming hyphal
 morphologies putatively involved in N-SOM acquisition; sporocarp estimates
 from these communities were enriched (+4‰), further supporting fungal
 N-SOM acquisition. In contrast, trees occurring in high inorganic N soils
 hosted distinct communities with morpho-traits associated with inorganic N
 acquisition and depleted sporocarps (+0.5‰). Together, our results are
 consistent with apparent tradeoffs in the foraging cost and contribution
 of N-SOM to plant growth, and demonstrate linkages between ECM community
 composition, fungal N-foraging potential and foliar d15N. The functional
 characteristics of ECM communities represents a mechanistic basis for
 flexibility in plant nutrient foraging strategies. We conclude that the
 contribution of N-SOM to plant growth is likely contingent on ECM
 community composition and local soil nutrient availability.
description: This represents raw isotopic values for<em> Quercus
 rubra</em> foliage, roots, soil, and inorganic N pools. Details
 regarding processing and instrumentation are fully described in the main
 text.
description: Three files are uploaded. 1). Soil_Foliage contains N15 isotope
 values for Quercus rubra green leaves, Oi horizon leaves, and bulk SOM
 underneath each individual tree. N concentrations ug/mg are also presented
 for each measured component. 2). Diffusions file contains N15 isotope
 values for Ammonium, Nitrate, and Dissolved orgnaic nitrogen, as described
 and processed in the main text. Total N yield is also presented, and
 recommendations suggest that samples with less than 20ug total nitrogen
 may represent poor quality measures 3). Roots contains three replicate
 measures of N15 at the 'stand' level because individual tree
 sampling was not possible. The coding as designated, is Stand-Tree,
 whereas for the Roots dataset, only Stand is presented with replicate
 number listed. A total of 12 stands were studied, with 5 individual trees
 in each stand.