Ammonium as a driving force of plant diversity and ecosystem functioning: observations based on 5 Years' manipulation of N dose and form in a mediterranean ecosystem

Dias, Teresa; Clemente, Adelaide; Martins-Loução, Maria Amélia; Sheppard, Lucy; Bobbink, Roland; Cruz, Cristina. 2014 Ammonium as a driving force of plant diversity and ecosystem functioning: observations based on 5 Years' manipulation of N dose and form in a mediterranean ecosystem. PLoS ONE, 9 (4), e92517. 10, pp. 10.1371/journal.pone.0092517

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Abstract/Summary

Enhanced nitrogen (N) availability is one of the main drivers of biodiversity loss and degradation of ecosystem functions. However, in very nutrient-poor ecosystems, enhanced N input can, in the short-term, promote diversity. Mediterranean Basin ecosystems are nutrient-limited biodiversity hotspots, but no information is available on their medium- or long-term responses to enhanced N input. Since 2007, we have been manipulating the form and dose of available N in a Mediterranean Basin maquis in south-western Europe that has low ambient N deposition (,4 kg N ha21 yr21) and low soil N content (0.1%). N availability was modified by the addition of 40 kg N ha21 yr21 as a 1:1 NH4Cl to (NH4)2SO4 mixture, and 40 and 80 kg N ha21 yr21 as NH4NO3. Over the following 5 years, the impacts on plant composition and diversity (richness and evenness) and some ecosystem characteristics (soil extractable N and organic matter, aboveground biomass and % of bare soil) were assessed. Plant species richness increased with enhanced N input and was more related to ammonium than to nitrate. Exposure to 40 kg NH4 +-N ha21 yr21 (alone and with nitrate) enhanced plant richness, but did not increase aboveground biomass; soil extractable N even increased under 80 kg NH4NO3-N ha21 yr21 and the % of bare soil increased under 40 kg NH4 +-N ha21 yr21. The treatment containing less ammonium, 40 kg NH4NO3-N ha21 yr21, did not enhance plant diversity but promoted aboveground biomass and reduced the % of bare soil. Data suggest that enhanced NHy availability affects the structure of the maquis, which may promote soil erosion and N leakage, whereas enhanced NOx availability leads to biomass accumulation which may increase the fire risk. These observations are relevant for land use management in biodiverse and fragmented ecosystems such as the maquis, especially in conservation areas.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1371/journal.pone.0092517
UKCEH and CEH Sections/Science Areas:	UKCEH Fellows
ISSN:	1932-6203
NORA Subject Terms:	Ecology and Environment
Date made live:	08 Apr 2014 11:15 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/506978

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