Using lichen functional diversity to assess the effects of atmospheric ammonia in Mediterranean woodlands

Abstract

Summary1. Atmospheric ammonia (NH 3 ) is one of the main drivers for ecosystem changes world-wide, including biodiversity loss. Modelling its deposition to evaluate its impact on ecosystems has been the focus of many studies. For that, universal indicators are needed to determine and compare the early effects of NH 3 across ecosystems. 2. We evaluate the effects of atmospheric NH 3 in ecosystems using lichens, which are one of the most sensitive communities at the ecosystem level. Rather than measuring total diversity, we use a functional diversity approach because this is potentially a more universal tool. 3. We evaluated the spatial and temporal patterns of atmospheric NH 3 concentrations ([NH 3 ] atm ) emitted from a point-source over a 1-year period in a cork oak Mediterranean woodland. We observed a temporal pattern of [NH 3 ] atm , with maximum concentrations during autumn. 4. The distribution of lichen species was c. 90% explained by [NH 3 ] atm . The tolerance of lichen species to atmospheric NH 3 , based on expert knowledge from literature, was tested for the first time against direct measurements of atmospheric NH 3 . Most species were well classified, with the exception of Lecanora albella and Chrysothrix candelaris, which were more tolerant than expected. Our updated lichen classification can be used to establish lichen functional groups that respond to atmospheric NH 3 , and these can be used in other Mediterranean countries. 5. Increasing [NH 3 ] atm led to a complete replacement of oligotrophic by nitrophytic species within 65 m of the NH 3 source. The geostatistical analysis of functional diversity variables yielded a spatial model with low non-spatial variance, indicating that these variables can cope robustly with high spatial variation in NH 3 . 6. Synthesis and applications. Our results support the use of functional diversity variables, such as a lichen diversity value, as accurate and robust indicators of the effects of atmospheric NH 3 on ecosystems. The spatial modelling of these indicators can provide information with high spatial resolution about the effects of atmospheric NH 3 around point-and diffuse sources. As this methodology is based on functional groups, it can be applied to monitor both the impact of atmospheric NH 3 and the success of mitigation strategies.

Critical loads of nitrogen deposition and critical levels of atmospheric ammonia for semi-natural Mediterranean evergreen woodlands

“…For correlating LDVs with [NH 3 ] atm , an interpolation of one of those variables was necessary, because they were not Species with * had their classification corrected after Pinho et al (2011). None of the species found is known to fix nitrogen.…”

Consequence of altered nitrogen cycles in the coupled human and ecological system under changing climate: The need for long-term and site-based research

“…The sensitivity of terrestrial biodiversity to the deposition of oxidized and reduced N provides the basis for setting critical loads for N deposition both in Europe and North America (Cape et al 2009;Bobbink and Hettelingh 2011;Pinho et al 2011Pinho et al , 2012. Independently derived critical levels for lichens and moss diversity have been found to be similar for northern and southern Europe, thus emphasizing the universal applicability of these plant groups as ecological indicators of N deposition.…”

“…For example, some previous studies have suggested that very sensitive organisms, such as lichens and mosses, could be effective early-warning indicators of atmospheric Nr pollution in the early stages of anthropogenic disturbance of N cycles in an ecosystem (Pinho et al 2011). The functional diversity of lichens and/or mosses coupled with measures of their nitrogen content and isotopic composition has the potential to be explicit spatial indicators of the early effects of Nr pollution.…”

Carbon-Water-Nitrogen relationships between lichens and the atmosphere: Tools to understand metabolism and ecosystem change

“…In this work, the dispersion and the distance of influence of eutrophication/NH 3 in lichens was found to be of short-range. However, the areas affected by it were found to be widespread in the territory, and always associated to agricultural sources (Pinho et al 2011(Pinho et al , 2012b.…”

“…The green-algal lichens were positively related to potential solar radiation whereas cyanolichens were negatively related (Pinho et al 2010). It this study it has been proved that lichen communities can be used to: i) model long-term microclimatic conditions with high spatial resolution and ii) model the disturbance caused by neighborhood areas, even in natural parks with low-intensity human activities, for conservation purposes (Pinho et al 2011(Pinho et al , 2012a.…”