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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-81
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-81
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 23 Apr 2019

Submitted as: research article | 23 Apr 2019

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Biogeosciences (BG) and is expected to appear here in due course.

Strong correspondence between nitrogen isotope composition of foliage and chlorin across a rainfall gradient: Implications for paleo-reconstruction of the nitrogen cycle

Sara K. E. Goulden1, Naohiko Ohkouchi2, Katherine H. Freeman3, Yoshito Chikaraishi2, Nanako O. Ogawa2, Hisami Suga2, Oliver Chadwick4, and Benjamin Z. Houlton1 Sara K. E. Goulden et al.
  • 1University of California at Davis, Davis, CA 95616, USA
  • 2Japan Agency for Marine Earth-Science and Technology (JAMSTEC) Yokosuka, Kanagawa 237-0061, Japan
  • 3The Pennsylvania State University, University Park, State College, PA 16801, USA
  • 4University of California Santa Barbara, Santa Barbara, CA 93106, USA

Abstract. Nitrogen (N) availability influences patterns of terrestrial productivity and global carbon cycling, imparting strong but poorly resolved feedbacks on Earth's climate system. Central questions concern the timescale of N cycle response to elevated CO2 concentration in the atmosphere, and whether availability of this limiting nutrient increases or decreases with climate change. Nitrogen isotopic composition of bulk plant leaves provides information on large-scale patterns of N availability in the modern environment. Here we examine the utility of chlorins, degradation products of chlorophylls, hypothesized to persist in soil subsequent to plant decay, as proxies for reconstructing past plant δ15N. Specifically, we test the hypothesis that δ15N of plant leaves (δ15Nleaf) is recorded in δ15N of pheophytin a15Npheo) along the leaf-litter-soil continuum across an array of ecosystem climate conditions and plant functional types (C3, C4, legumes, and woody plants). The δ15N of live foliage and bulk soil display marked declines with increasing rainfall, consistent with past studies in Hawaii and patterns worldwide. We find measurable chlorin concentrations along soil-depth profiles at all sites, with pheophytin a present in amounts required for isotopic analysis (> 10 nmol). δ15Npheo in leaves, litter, and soil track δ15Nleaf of plant leaves. We find potential for δ15Npheo records from soil to provide proxy information on δ15Nleaf.

Sara K. E. Goulden et al.
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Sara K. E. Goulden et al.
Sara K. E. Goulden et al.
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Short summary
We investigate whether soil organic compounds preserve information about nitrogen availability to plants. We isolate chlorophyll degradation products in leaves, litter, and soil and explore possible species and climate effects on preservation and interpretation of values. We find that compound-specific nitrogen isotope measurements in soil have potential as a new tool to reconstruct changes in nitrogen cycling on a landscape over time, avoiding issues that have limited other proxies.
We investigate whether soil organic compounds preserve information about nitrogen availability...
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