Alleviating nitrogen limitation in Mediterranean maquis vegetation leads to ecological degradation

Teresa Dias, Casparus J. Crous, Dario Liberati, Silvana Munzi, Catarina Gouveia, Florian Ulm, Ana Catarina Afonso, Raul Ochoa-Hueso, Esteban Manrique, Lucy Sheppard, Maria Amelia Martins-Loucao, Anabela Bernardes da Silva, Cristina Cruz

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Soils are being degraded at an alarming rate and thereby also crucial ecosystem goods and services. Nitrogen (N) enrichment is a major driver of this degradation. While the negative impacts of N enrichment on vegetation are well known globally, those on various ecological interactions, and on ecosystem functioning, remain largely unknown. Because Mediterranean ecosystems are N limited, they are good model systems for evaluating how N enrichment impacts not only vegetation but also ecological partnerships and ecosystem functioning. Using a 7-year N-manipulation (dose and form) field experiment running in a Mediterranean Basin maquis located in a region with naturally low ambient N deposition (<4kgNha(-1)y(-1)), we assessed the impacts of the N additions on (i) the dominant plant species (photosynthetic N-use efficiency); (ii) plant-soil ecological partnerships with ectomycorrhiza and N-fixing bacteria; and (iii) ecosystem degradation (plant-soil cover, biological mineral weathering and soil N fixation). N additions significantly disrupted plant-soil cover, plant-soil biotic interactions, and ecosystem functioning compared with ambient N deposition conditions. However, the higher the ammonium dose (alone or with nitrate), the more drastic these disruptions were. We report a critical threshold at 20-40kg ammonium ha(-1)y(-1) whereby severe ecosystem degradation can be expected. These observations are critical to help explain the mechanisms behind ecosystem degradation, to describe the collective loss of organisms and multifunction in the landscape, and to predict potential fragmentation of Mediterranean maquis under conditions of unrelieved N enrichment.
Original languageEnglish
Pages (from-to)2482-2492
Number of pages11
JournalLand Degradation and Development
Volume28
Issue number8
DOIs
Publication statusPublished - 2017

Keywords

  • ammonium
  • ecosystems
  • nitrogen
  • soil degradation

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