Increased forest ecosystem carbon and nitrogen storage from nitrogen rich bedrock

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Nitrogen (N) limits the productivity of many ecosystems worldwide, thereby restricting the ability of terrestrial ecosystems to offset the effects of rising atmospheric CO2 emissions naturally1, 2. Understanding input pathways of bioavailable N is therefore paramount for predicting carbon (C) storage on land, particularly in temperate and boreal forests3, 4. Paradigms of nutrient cycling and limitation posit that new N enters terrestrial ecosystems solely from the atmosphere. Here we show that bedrock comprises a hitherto overlooked source of ecologically available N to forests. We report that the N content of soils and forest foliage on N-rich metasedimentary rocks (350–950mgNkg−1) is elevated by more than 50% compared with similar temperate forest sites underlain by N-poor igneous parent material (30–70mgNkg−1). Natural abundance N isotopes attribute this difference to rock-derived N: 15N/14N values for rock, soils and plants are indistinguishable in sites underlain by N-rich lithology, in marked contrast to sites on N-poor substrates. Furthermore, forests associated with N-rich parent material contain on average 42% more carbon in above-ground tree biomass and 60% more carbon in the upper 30cm of the soil than similar sites underlain by N-poor rocks. Our results raise the possibility that bedrock N input may represent an important and overlooked component of ecosystem N and C cycling elsewhere.

At a glance


  1. Total nitrogen in rock, soil and foliage pools for SFM and BWDC forests.
    Figure 1: Total nitrogen in rock, soil and foliage pools for SFM and BWDC forests.

    ac, Total nitrogen in rock (mgNkg−1, n = 18) (a), soil (%N, n = 34) (b) and plant foliage (%N, n = 80) (c) in the BWDC (black) and SFM (grey) forests. d, Foliar nitrogen expressed in μgN per needle, to account for biomass dilution. Calocedrus decurrens is not presented in d because of scale-leaf rather than needle-leaf morphology. Error bars represent s.e.m. Species sampled: Ac, Abies concolor; Pl, Pinus lambertiana; Pp, Pinus ponderosa; Cd, Calocedrus decurrens. Asterisk, P<0.05; two asterisks, P<0.01; three asterisks, P<0.001.

  2. Nitrogen isotope values of the rock-soil-plant system.
    Figure 2: Nitrogen isotope values of the rock–soil–plant system.

    a, SFM forest; b, BWDC forest. The median and range are plotted for each component. The dashed line represents the approximate isotope value for total atmospheric N inputs.

  3. Carbon in above-ground tree biomass for forests growing on N-rich and N-poor lithology.
    Figure 3: Carbon in above-ground tree biomass for forests growing on N-rich and N-poor lithology.

    Plot of carbon (Mgha−1) against stand age for FIA plots (n = 88) on N-rich (crosses) and N-poor (triangles) lithologies used in the model. To account for model axes not shown, we present detransformed model estimates for sites on N-rich (solid line) and N-poor (dashed line) lithologies, holding other model parameters constant at nominal values to illustrate differences in carbon storage attributable to lithology. The grey area indicates lithology s.e.m. Our analysis estimates that sites on N-rich lithology contain 42% more C in above-ground tree biomass than sites on N-poor lithology (P = 0.009; adjusted R2 = 0.66) after accounting for confounding state factors.


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  1. Department of Land, Air and Water Resources. University of California – Davis, California 95616, USA

    • Scott L. Morford,
    • Benjamin Z. Houlton &
    • Randy A. Dahlgren


S.L.M., B.Z.H. and R.A.D. contributed to the experimental design and collection of field samples. S.L.M. performed sample processing and laboratory analysis. S.L.M. designed and implemented the FIA modelling component. S.L.M., B.Z.H. and R.A.D. contributed to the interpretation of laboratory data, modelling results and manuscript preparation.

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