Vertical distribution of carbon and nitrogen stable isotope ratios in topsoils across a temperate rainforest dune chronosequence in New Zealand
- 619 Downloads
Chronosequences can provide valuable insights into carbon (C) and nitrogen (N) dynamics across natural gradients with C and N stable isotopes serving as powerful tool investigating these dynamics. We studied changes in δ13C and δ15N values in litter, organic layer and mineral soil on dunes across the Haast chronosequence (New Zealand), which spans 120 to 2870 years of pedogenesis beneath a temperate rainforest. Decomposition was approximated from linear regression slopes between C concentrations and δ13C values and termed betaC. Similarly we calculated betaN values to test the relationship between vertical N decrease and δ15N increase. Decreasing δ13C values of litter with age suggests a physiological response of plants to decreased litter N concentrations. A decrease of litter δ15N in the early succession stages and a second decline after 1300 years indicates reduced N2 fixation. BetaC values increased during early ecosystem development and at old sites, and were lowest at the intermediate stages (1500 years), which suggests decomposition did not decrease constantly with time. BetaN values were lowest at the youngest site and increased within the first 200 years, likely because litter as the uppermost part of the vertical depth profile reflected an increased supply of N depleted in 15N provided by fungi. We found relations between betaC and betaN values suggesting that there might be shared processes shaping δ13C and δ15N vertical depth profiles, e.g. microbial cycling, transport or sorption.
Keywordsδ13C and δ15N depth profile Natural abundance stable isotopes N2 fixation Nutrient limitation Organic layer Organic matter decomposition
We thank G. Guggenberger, L. Sauheitl and S. Bokeloh (Leibniz University Hanover, Germany) for providing isotopic analysis, U. Bange, M. Kraft and A. Bell (University of Koblenz-Landau, Germany) for laboratory assistance, A. Torky and N. Franks (Lincoln University, New Zealand) for organizing the sample transport and W. Wilcke (Karlsruhe Institute of Technology, Germany) and F. Brunn (University of Mainz, Germany) for facilitating this work. We gratefully acknowledge research funding by the German Academic Exchange Service (DAAD Grant D/12/45516).
- Keeling CD, Piper SC, Bacastow RB, Wahlen M, Whorf TP, Heimann M, Meijer HA (2005) Atmospheric CO2 and (CO2)-C-13 exchange with the terrestrial biosphere and oceans from 1978 to 2000: observations and carbon cycle implications. In: Ehleringer JR, Cerling TE, Dearing MD (eds) Ecological studies: analysis and synthesis. Springer, New York, pp 83–113Google Scholar
- Martinelli LA, Piccolo MC, Townsend AR, Vitousek PM, Cuevas E, McDowell W, Robertson GP, Santos OC, Treseder K (1999) Nitrogen stable isotopic composition of leaves and soil: tropical versus temperate forests. Biogeochemistry 46(1–3):45–65Google Scholar
- Menge DNL, Wolf AA, Funk JL (2015) Diversity of nitrogen fixation strategies in Mediterranean legumes. Nat Plants 1(6):1–5Google Scholar
- Pickett STA, White PS (1985) The ecology of natural disturbance and patch dynamics. Academic Press, Orlando, p 472Google Scholar
- Reed SC, Cleveland CC, Townsend AR (2011) Functional ecology of free-living nitrogen fixation: a contemporary perspective. In: Futuyma DJ, Shaffer HB, Simberloff D (eds) Annual review of ecology, evolution, and systematics, vol 42. Annual Reviews, Palo Alto, pp 489–512Google Scholar
- Stockmann U, Adams MA, Crawford JW, Field DJ, Henakaarchchi N, Jenkins M, Minasny B, McBratney AB, de Courcelles VD, Singh K, Wheeler I, Abbott L, Angers DA, Baldock J, Bird M, Brookes PC, Chenu C, Jastrow JD, Lal R, Lehmann J, O’Donnell AG, Parton WJ, Whitehead D, Zimmermann M (2013) The knowns, known unknowns and unknowns of sequestration of soil organic carbon. Agric Ecosyst Environ 164:80–99CrossRefGoogle Scholar
- Vitousek P (2004) Nutrient cycling and limitation: Hawai’i as a model system. Princeton University Press, PrincetonGoogle Scholar