Impact of long-term nitrogen deposition on the response of dune grassland ecosystems to elevated summer ozone

Hayes, Felicity ORCID:; Lloyd, Bethan; Mills, Gina; Jones, Laurence ORCID:; Dore, Anthony J.; Carnell, Edward ORCID:; Vieno, Massimo ORCID:; Dise, Nancy; Fenner, Nathalie. 2019 Impact of long-term nitrogen deposition on the response of dune grassland ecosystems to elevated summer ozone. Environmental Pollution, 253. 821-830.

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Nitrogen deposition and tropospheric ozone are important drivers of vegetation damage, but their interactive effects are poorly understood. This study assessed whether long-term nitrogen deposition altered sensitivity to ozone in a semi-natural vegetation community. Mesocosms were collected from sand dune grassland in the UK along a nitrogen gradient (5–25 kg N/ha/y, including two plots from a long-term experiment), and fumigated for 2.5 months to simulate medium and high ozone exposure. Ozone damage to leaves was quantified for 20 ozone-sensitive species. Soil solution dissolved organic carbon (DOC) and soil extracellular enzymes were measured to investigate secondary effects on soil processes. Mesocosms from sites receiving the highest N deposition showed the least ozone-related leaf damage, while those from the least N-polluted sites were the most damaged by ozone. This was due to differences in community-level sensitivity, rather than species-level impacts. The N-polluted sites contained fewer ozone-sensitive forbs and sedges, and a higher proportion of comparatively ozone-resistant grasses. This difference in the vegetation composition of mesocosms in relation to N deposition conveyed differential resilience to ozone. Mesocosms in the highest ozone treatment showed elevated soil solution DOC with increasing site N deposition. This suggests that, despite showing relatively little leaf damage, the ‘ozone resilient’ vegetation community may still sustain physiological damage through reduced capacity to assimilate photosynthate, with its subsequent loss as DOC through the roots into the soil. We conclude that for dune grassland habitats, the regions of highest risk to ozone exposure are those that have received the lowest level of long-term nitrogen deposition. This highlights the importance of considering community- and ecosystem-scale impacts of pollutants in addition to impacts on individual species. It also underscores the need for protection of ‘clean’ habitats from air pollution and other environmental stressors.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: Atmospheric Chemistry and Effects (Science Area 2017-)
Soils and Land Use (Science Area 2017-)
UKCEH Fellows
ISSN: 0269-7491
NORA Subject Terms: Ecology and Environment
Date made live: 01 Aug 2019 10:31 +0 (UTC)

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