Pedro Pinho

Species richness of lichen functional groups in relation to land use intensity

Changing land use has a major impact on lichen diversity. This study attempts to identify patterns or trends of lichen functional groups along a land use gradient, ranging from natural forests to open agricultural landscape. In eight countries, covering six main European biogeographic regions, lichen vegetation was assessed according to a standardized scheme. Data on reproductive, vegetative and ecological traits was compiled and relative species richness for all classes of all traits calculated. Relationships between the land use gradient and relative species richness of trait classes were analysed. Open and intensively managed landscapes harbour more fertile species while sterile species are relatively more important in forests. This finding is also supported by analyses of different classes of dispersal propagules. The importance of species with the principal photobiont Trebouxia s.l. increases linearly with intensification of land use. A converse pattern is revealed by species with Trentepohlia. Concerning substratum specialization only generalists show an effect along the land use intensity gradient. Their relative species richness decreases from landscapes dominated by forests to open agricultural landscape. A considerable decline in the rare lichen species richness as a result of land intensification is predicted.

Lichen traits responding to aridity

Summary 1. Climate change is expected to cause several impacts at the global scale, and drylands will be amongst the most affected areas. Thus, investigating how these changes will affect the composition, structure and functioning of dryland ecosystems has become a priority. From an ecological indicator point of view, several works have shown that functional diversity is better than species richness to understand ecosystem functioning or response to environmental factors. However, most of these works focus on plants, while those of other organisms remain largely unknown. Lichens are amongst the ecosystem components more sensitive to climatic changes due to several physiological and ecological characteristics. Their poikilohydric nature (therefore highly dependent on the atmosphere for water supply) and their ubiquity on terrestrial ecosystems underlie their potential as indicators of climate. Nonetheless, works specifically aiming to identify lichen functional traits that respond to aridity remain poorly explored, particularly in drylands. 2. We proposed to identify lichen functional traits and respective functional groups responding to aridity in a Mediterranean drylands ecosystem. 3. Lichen diversity was sampled in open holm oak woodlands along an aridity gradient in SW Europe (Iberian Peninsula). Lichen functional traits that could be easily identified and related to water uptake were selected to be tested: type of photobiont, growth form and reproduction strategy. 4. Lichen species composition was related to the aridity gradient. The three traits chosen were related with the community’s response to aridity, but with contrasting responses in different functional groups. More specifically crustose and fruticose lichens, isidiate species and the ones with Trentepohlia as photobiont were related to the less arid part of the gradient. Foliose species and cyanolichens, on the contrary, were associated with the most arid areas. 5. Synthesis. We were able to identify lichen traits responding to aridity. Type of photobiont was particularly responsive, with Trentepohlia and cyanobacteria functional groups, responding clearly in contrasting ways to aridity in this drylands ecosystem. This work emphasizes functional diversity role on understanding and assessing the response to environmental factors, namely to climate. It also highlights the potential use of lichen functional groups as ecological indicators of climate change.

Assessment of Critical Levels of Atmospheric Ammonia for Lichen Diversity in Cork-Oak Woodland, Portugal

The effect of atmospheric ammonia on ecosystems has been the subject of ongoing research. Its adverse effects as an air pollutant are well characterised, and may be even more widespread than previously thought (see Aber et al. 2003; Erisman et al. 2003; Krupa 2003; Purvis et al. 2003). The most important sources of NH3 in Europe are agricultural activities, mainly crop fertilization and cattle management (Galloway et al. 2003; EPER 2004). Livestock housing facilities are recognised to be large point sources of NH3 emissions. Close to such facilities, atmospheric NH3 concentrations are very high, decreasing rapidly with distance over a few hundreds of meters to a few kilometres (Sutton et al. 1998). Measurement of atmospheric NH3 in the vicinity of livestock housing include those by Pitcairn et al. (1998, 2003), with reported values in Scotland of 24 –59 μg m−3 close to source, which declined to background values of 1.6 –5 μg m−3 at 1 km. In order to assess the range of effects of NH3 in natural ecosystems, that can be used for effective NH3 mitigation policies (Dragosits et al. 2006), one can rely on two distinct approaches: (i) direct measurements of atmospheric NH3 concentrations, which provide an estimate of dry NH3-N deposition, but require intensive and costly operations; (ii) monitoring of effects on the biotic component. The latter approach should be carried out using groups of biota that are more sensitive to the pollutant of interest. Lichens have been reported as the most sensitive group to NH3 emissions (e.g. Wolseley et al. 2006a; van Herk 1999). Lichens are symbiotic organisms widely used as biomonitors of environmental changes (e.g. Nimis et al. 1991; Vokou et al. 1999; Geebelen and Hoffmann 2001; Giordani et al. 2002; Pirintsos and Loppi 2003; Geiser and Neitlich 2007). nMonitoring atmospheric pollutants using lichens may be undertaken in three ways: (1) measuring variations in lichens diversity and/or abundance, (2) using variations in physiological parameters, and/or using lichens as accumulators of pollutants (Branquinho 2001), and (3) considering functional groups related to nutrients tolerance, such as the division between nitrophytic/oligotrophic (or nitrophytic/ acidophitic) groups (see van Dobben and ter Braak 1999; Ruisi et al. 2005; Wolseley et al. 2006b).

Lichens as ecological indicators in urban areas: beyond the effects of pollutants

Summary 1. In this work, we hypothesized that in urban areas with reduced pollution levels, local climatic conditions can be an important driver of lichen diversity. Thus, lichen functional groups could be used to study the effects of the urban heat island, characterized by higher temperature and lower humidity in urban than in peri-urban areas. To test this hypothesis, we sampled functional groups of epiphytic lichens in 48 forest remnants of a Mediterranean urban area (Almada, Portugal). 2. Of all tested functional groups (including those most closely associated with air pollution), groups related to water requirements showed the most significant correlations with surrounding artificial areas, roads and forest. These results suggest that the current major driver of lichen diversity is the climate within the urban area rather than air pollution, as frequently assumed. 3. The analysis of local climate using meteorological data of temperature and humidity confirmed the existence of urban heat island in the study area. 4. Synthesis and applications. The analysis of lichen functional groups gave an integrated response to the climatic modifications occurring in urban areas, namely to the urban heat island, suggesting that lichens can be used as a tool to evaluate the impact of urban areas on local climate and the effectiveness of mitigation and adaptation strategies if pollution levels are low.

Ecological impacts of atmospheric pollution and interactions with climate change in terrestrial ecosystems of the mediterranean basin: Current research and future directions

Mediterranean Basin ecosystems, their unique biodiversity, and the key services they provide are currently at risk due to air pollution and climate change, yet only a limited number of isolated and geographically-restricted studies have addressed this topic, often with contrasting results. Particularities of air pollution in this region include high O3 levels due to high air temperatures and solar radiation, the stability of air masses, and dominance of dry over wet nitrogen deposition. Moreover, the unique abiotic and biotic factors (e.g., climate, vegetation type, relevance of Saharan dust inputs) modulating the response of Mediterranean ecosystems at various spatiotemporal scales make it difficult to understand, and thus predict, the consequences of human activities that cause air pollution in the Mediterranean Basin. Therefore, there is an urgent need to implement coordinated research and experimental platforms along with wider environmental monitoring networks in the region. In particular, a robust deposition monitoring network in conjunction with modelling estimates is crucial, possibly including a set of common biomonitors (ideally cryptogams, an important component of the Mediterranean vegetation), to help refine pollutant deposition maps. Additionally, increased attention must be paid to functional diversity measures in future air pollution and climate change studies to establish the necessary link between biodiversity and the provision of ecosystem services in Mediterranean ecosystems. Through a coordinated effort, the Mediterranean scientific community can fill the above-mentioned gaps and reach a greater understanding of the mechanisms underlying the combined effects of air pollution and climate change in the Mediterranean Basin.

Tools for determining critical levels of atmospheric ammonia under the influence of multiple disturbances

Critical levels (CLEs) of atmospheric ammonia based on biodiversity changes have been mostly calculated using small-scale single-source approaches, to avoid interference by other factors, which also influence biodiversity. Thus, it is questionable whether these CLEs are valid at larger spatial scales, in a multi- disturbances context. To test so, we sampled lichen diversity and ammonia at 80 sites across a region with a complex land-cover including industrial and urban areas. At a regional scale, confounding factors such as industrial pollutants prevailed, masking the CLEs. We propose and use a new tool to calculate CLEs by stratifying ammonia concentrations into classes, and focusing on the highest diversity values. Based on the significant correlations between ammonia and biodiversity, we found the CLE of ammonia for Mediterranean evergreen woodlands to be 0.69xa0μgxa0m(-3), below the previously accepted value of 1.9xa0μgxa0m(-3), and below the currently accepted pan-European CLE of 1.0xa0μgxa0m(-3).

Evaluating green infrastructure in urban environments using a multi-taxa and functional diversity approach.

Forested areas within cities host a large number of species, responsible for many ecosystem services in urban areas. The biodiversity in these areas is influenced by human disturbances such as atmospheric pollution and urban heat island effect. To ameliorate the effects of these factors, an increase in urban green areas is often considered sufficient. However, this approach assumes that all types of green cover have the same importance for species. Our aim was to show that not all forested green areas are equal in importance for species, but that based on a multi-taxa and functional diversity approach it is possible to value green infrastructure in urban environments. After evaluating the diversity of lichens, butterflies and other-arthropods, birds and mammals in 31 Mediterranean urban forests in south-west Europe (Almada, Portugal), bird and lichen functional groups responsive to urbanization were found. A community shift (tolerant species replacing sensitive ones) along the urbanization gradient was found, and this must be considered when using these groups as indicators of the effect of urbanization. Bird and lichen functional groups were then analyzed together with the characteristics of the forests and their surroundings. Our results showed that, contrary to previous assumptions, vegetation density and more importantly the amount of urban areas around the forest (matrix), are more important for biodiversity than forest quantity alone. This indicated that not all types of forested green areas have the same importance for biodiversity. An index of forest functional diversity was then calculated for all sampled forests of the area. This could help decision-makers to improve the management of urban green infrastructures with the goal of increasing functionality and ultimately ecosystem services in urban areas.

Can ammonia tolerance amongst lichen functional groups be explained by physiological responses

Ammonia (NH3) empirical critical levels for Europe were re-evaluated in 2009, based mainly on the ecological responses of lichen communities without acknowledging the physiological differences between oligotrophic and nitrophytic species. Here, we compare a nitrogen sensitive lichen (Evernia prunastri) with a nitrogen tolerant one (Xanthoria parietina), focussing on their physiological response (Fv/Fm) to short-term NH3 exposure and their frequency of occurrence along an NH3 field gradient. Both frequency and Fv/Fm of E.xa0prunastri decreased abruptly above 3xa0μgxa0m(-3) NH3 suggesting direct adverse effects of NH3 on its photosynthetic performance. By contrast, X.xa0parietina increased its frequency with NH3, despite showing decreased capacity of photosystem II above 50xa0μgxa0m(-3) NH3, suggesting that the ecological success of X.xa0parietina at ammonia-rich sites might be related to indirect effects of increased nitrogen (NH3) availability. These results highlight the need to establish NH3 critical levels based on oligotrophic lichen species.

Declining trends of PCDD/Fs in lichens over a decade in a Mediterranean area with multiple pollution sources

Lichens are one of the most useful environmental biomonitors, due to their ability to clearly reflect atmospheric deposition of pollutants. Dioxin and furan (PCDD/F) emissions have been reported to be decreasing in North European countries as a consequence of European regulations. This reduction has been perceptible across several environmental matrices, but it hasnt yet been shown in lichens as typical biomonitors of atmospheric pollution. In this work we compared concentrations of PCDD/Fs in two lichen species collected in a Mediterranean area with mixed land-uses, encompassing urban, industrial and natural areas, in 2009 and 2011 with the ones obtained in the same species collected in the same region in 2000. We found that PCDD/F concentrations in both lichen species have decreased approximately 70% since 2000 whereas industrial emissions have only decreased 25% for the same period. This substantial greater reduction observed in lichens may be due to several causes; after excluding fires as a possible explanation, we point out that possible causes could not only be the overall decrease in industrial emissions but also other causes such as traffic reduction and/or increase efficiency in the use of fuels. Capsule: PCDD/F concentrations in lichens have decreased 70% over the last decade, whereas industrial emissions have only decreased 25%.

Modeling the long-term natural regeneration potential of woodlands in semi-arid regions to guide restoration efforts

Understanding forest regeneration at sites previously used for agriculture underlies the establishment of science-based woodlands management policies. This is especially relevant in semi-arid areas, where the tree cover is critical in ameliorating the effects of aridity and in preventing desertification and land degradation. Natural regeneration in semi-arid areas occurs very slowly, which in part explains why it has hardly been studied. In the present work, we sought to devise a method to predict the natural regeneration potential of woodlands in semi-arid areas, to be used in guiding restoration efforts. Specifically, we evaluated holm oak coverage at a long-term ecological research site and then designed and validated a model to predict the natural regeneration of holm oak based on a few environmental variables. Unlike available studies, we obtained long-term information on tree regeneration (making use of >60xa0years of aerial photography) and climate (using long-term climate and microclimate data). We found that microclimate, measured using the potential solar radiation as a proxy, was a key driver of natural regeneration: after 60xa0years of agricultural abandonment, less sun-exposed areas attained a tree cover >90xa0%, whereas in more sun-exposed areas it remained below 20xa0%. We then used the model to map the natural regeneration potential, first in the study area and then in an area where holm oak plantations had been unsuccessfully introduced. In the latter case, the model successfully predicted the failure of this reforestation effort. Our results support the use of this model by decision makers to optimize management practices, as it will encourage the concentration of efforts in areas more prone to successful reforestation and allow the identification of areas more likely to benefit from natural regeneration processes.