Alleviating nitrogen limitation in Mediterranean maquis vegetation leads to ecological degradation

Dias, Teresa; Crous, Casparus J.; Liberati, Dario; Munzi, Silvana; Gouveia, Catarina; Ulm, Florian; Afonso, Ana Catarina; Ochoa-Hueso, Raúl; Manrique, Esteban; Sheppard, Lucy; Martins-Loução, Maria Amélia; Bernardes da Silva, Anabela; Cruz, Cristina. 2017 Alleviating nitrogen limitation in Mediterranean maquis vegetation leads to ecological degradation. Land Degradation & Development, 28 (8). 2482-2492.

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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 (<4 kg N ha−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 20–40 kg 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.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: UKCEH Fellows
ISSN: 1085-3278
Additional Keywords: ammonium, ecosystem degradation, ecosystem functioning, Mediterranean, plant–soil ecological partnerships
NORA Subject Terms: Ecology and Environment
Date made live: 23 Nov 2017 13:00 +0 (UTC)

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