Slowing of nitrogen cycling and increasing nitrogen use efficiency following afforestation of semi-arid shrubland

I. Gelfand*, J. M. Grünzweig, D. Yakir

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Nitrogen (N) and water availability are important factors affecting ecosystem productivity that can be influenced by land-use change. We hypothesized that the observed increase in carbon (C) sequestration associated with afforestation of semi-arid sparse shrubland must also be associated with an increase in N input. We tested this hypothesis by reconstructing the ecosystem N budget of two ecosystems, a semi-arid shrubland and a nearby planted pine forest, using measurements augmented with literature-based estimates. Our findings demonstrate that, contrary to our hypothesis, massive C sequestration by the pine forest could be accounted for without a change in the net N budget (i. e., neither elevated N inputs nor reduced N losses). However, in comparison to the shrubland, the forest showed an almost tripling in aboveground N use efficiency (NUE; 235 vs. 83 kg dry mass kg -1 N) and a doubling in ecosystem level C/N ratio (16 vs. 8, for the forest and shrubland, respectively). Nitrogen cycling slowed in the forest compared to the shrubland: net N mineralization rates in soils decreased by approximately 50%, decomposition rates decreased by approximately 20%, and NO x loss decreased by approximately 64%. These adjustments in N cycling provide a possible basis for increased NUE and subsequent C sequestration without net change in the overall N budget, which should be addressed in future investigations.

Original languageAmerican English
Pages (from-to)563-575
Number of pages13
JournalOecologia
Volume168
Issue number2
DOIs
StatePublished - Feb 2012

Bibliographical note

Funding Information:
Acknowledgments We are grateful to Leon Peters, Uri Shapira, and Nitai Zecharia for technical assistance and help with field sampling, Marcelo Sternberg, Dina Kanas, and Yael Fried-Shaked for information on S. spinosum and pine fine roots biomass, and the KKL for cooperation in the field site. We thank two anonymous reviewers for thoughtful and helpful comments and I. A. Cooper for the editing of the manuscript. This research was supported in part by a grant from the Israeli Ministry of Science and Technology and the German BMBF (GLOWA––Jordan River), the KKL, and JNF-Alberta. The long-term operation of the Yatir Forest Research Field Site is supported by the Cathy Wills and Robert Lewis Program in Environmental Science.

Keywords

  • Land-use change
  • Mediterranean ecosystem
  • N budget
  • Pinus halepensis
  • Semi-arid climate

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