Luisa Frati

Influence of Tree Substrate on the Diversity of Epiphytic Lichens: Comparison Between Tilia platyphyllos and Quercus ilex (Central Italy)

Abstract A comparison between lime (Tilia platyphyllos) and holly oak (Quercus ilex) as substrate trees for epiphytic lichens was carried out in Siena (central Italy). The purpose of this study was to investigate the influence of these phorophytes on the diversity of epiphytic lichens, at a similar climatic regime and at the same air pollution status. The diversity values measured on Tilia were on the average 1.5 times higher than those on Quercus. No difference between the two tree species appeared for bark pH and bark concentrations of NO3−, SO42−, NH4+, Cu, and Pb. Bark concentrations of Mn were higher for Quercus. The water-holding capacity of the bark of Tilia was higher than that of Quercus. The amount of incident light radiation was similar for the two trees in summer, when both species have leaves, but was higher on deciduous lime in winter, when only the evergreen Q. ilex has leaves. Influx light in winter is the most important factor for determining differences in the biodiversity of epiphytic lichens on Tilia and Q. ilex.

Rapid biodiversity assessment in lichen diversity surveys: implications for quality assurance

Rapid Biodiversity Assessments (RBAs) of lichen communities, obtained by means of simplified sampling lists based on morphospecies, showed good correlations with Lichen Diversity Values (LDVs), based on the complete identification of lichen species only when performed by operators with high levels of taxonomic knowledge. Furthermore, the use of highly simplified sampling lists did not lead to significant advantages in terms of time needed for field operations. This approach proved to be especially unreliable in high diversity ecological contexts where variation of morpho-structural composition within lichen communities is frequent (i.e. co-occurring crustose- and foliose-dominated communities); it may also lead to weak results if applied for conservation purposes. Hence, the use of simplified RBA sampling lists in lichen monitoring has to be carefully evaluated and, in any case, should be based on sound taxonomic knowledge on the part of those in charge of data collection. The proper assessment of descriptors of lichen abundance and/or frequency, however, strictly depends on the skill, taxonomic knowledge, and willingness to learn of the lichenologist-in-training.

Effects of reduced nitrogen compounds on epiphytic lichen communities in Mediterranean Italy

The effects of reduced nitrogen compounds on epiphytic lichen vegetation have been largely investigated in northern Europe. This paper reports for the first time results of a study carried out on pine trees in the Mediterranean basin. Contrary to the usual acidophytic lichen colonization of pine bark, in this case a nitrophytic lichen vegetation was found, suggesting that the study area is characterized by a diffuse eutrophication. Tree circumference, distance from the stock farms, bark pH and bark electrical conductivity emerged as the main factors influencing the distribution and abundance of epiphytic lichens in the study area. Both Hyperphyscia adglutinata and Xanthoria parietina were suitable local indicator species of high pine bark pH values. However, while X. parietina indicated high nitrogen dust pollution, H. adglutinata occurred also where there was an additional increase in bark pH caused by the release of high amounts of ammonia. The increased nitrogen availability caused by ammonium apparently had no effect on the occurrence of nitrophytes.

Lettuce plants as bioaccumulators of trace elements in a community of central Italy

A survey, based on the use of vascular plants to describe the distribution of selected elements (21 in total) was performed in 11 sites in the area of Castelfiorentino (Tuscany, Central Italy) differing for land use, from urban to industrial and rural areas. Lettuce plants grown under standardized conditions were positively used as biodeposimeters of airborne trace elements. Washing was found to be highly significant in reducing concentrations of many elements in the samples, suggesting a general surface contamination of leaves. The typical crustal element Al showed good correlations with Co, Fe, Li and V; on the contrary, Zn and Cd were intercorrelated and showed no connection with crustal indicators. Lead was still a relevant environmental presence, as the experiments were carried out before the ban of leaded gasoline. Source apportionment by factor analysis put in evidence a major contribution of crustal materials, followed by man-related activities; a minor role was ascertained for marine aerosol. A comparison was made between analytical data of lettuce plants grown in our experimental sites and a bulk of commercial lettuce purchased at a local supermarket. It should be stressed how Cu concentrations of commercial material were significantly higher than those found in our plants; this is likely caused by phytosanitary treatments.

Mapping environmental effects of agriculture with epiphytic lichens

The present paper reports the results of a study designed to check the feasibility of epiphytic lichens as biomonitors of the effects of agriculture in an area of central Italy without heavy industrialization and with an economy mainly based on agricul-ture. The exclusion of nitrophytic species (objectively selected using the on-line check-list of Italian lichens) from the calculation of the index of lichen diversity, which is supposed to reflect air quality, led to more realistic results. Conversely, the use of only nitrophytic species allowed us to map the eutrophication in the area, which resulted in lichens heavily affected by agricultural activities. Mapping using only strictly nitrophytic species showed two “hot spots” where ammonia emission from animal husbandry plays an important role. Two sites emerged as suffering at the same time from ammonia and NOX pollution. It is concluded that epiphytic lichens are an effective tool to detect and map the effects of agriculture also in Mediterranean countries, at least in areas without heavy industrialization, given the proper species selection.

Biomonitoring urban air pollution using transplanted lichens: element concentrations across seasons

We investigated the bioaccumulation of selected trace elements in samples of the lichen Evernia prunastri (L.) Ach. transplanted across two seasons in the urban area of Genoa (NW Italy), which is heavily affected by traffic and industrial pollution. Total concentration of most elements did not exhibit differences between seasons, exceptions being Al and Na, higher in summer, and As, Cd, and Ti, higher in winter. Differences emerged in the initial concentrations of some elements in control samples, and this was accounted for by the use of exposed-to-control (EC) ratios, which allowed interpretation of changes in element concentrations. The study area resulted highly polluted, likely by particulate matter, as suggested also by the higher concentrations of airborne PM10 during winter months. Bioaccumulation of particulate matter seems to be affected by differences in rainfall regimes across seasons, since element solubilization and leaching due to precipitation may vary considerably.

Fragmentation of Mediterranean oak forests affects the diversity of epiphytic lichens

The present study investigated a fragmented Mediterranean oak forest to evaluate so called edge effect on species richness and composition of epiphytic lichen communities colonizing tree trunks. The results showed that in Mediterranean oak forest patches, epiphytic lichen diversity and communities are significantly influenced by microlimatic variables related to the edge effect. Light influx rather than atmospheric humidity and temperature was the main driving factor affecting lichen diversity along the forest edge-interior gradient, while humidity is the prevailing factor inside the forest. It is concluded that forest fragmentation may have a heavy impact of epiphytic lichens, with the reduction and disappearance of typical forest species and the appearance of ubiquitous tolerant species, with an overall impoverishment and banalization of the lichen flora.

Spatial scales of variation in lichens: implications for sampling design in biomonitoring surveys

The variability of biological data is a main constraint affecting the quality and reliability of lichen biomonitoring surveys for estimation of the effects of atmospheric pollution. Although most epiphytic lichen bioindication surveys focus on between-site differences at the landscape level, associated with the large scale effects of atmospheric pollution, current protocols are based on multilevel sampling, thus adding further sources of variation and affecting the error budget. We test the hypothesis that assemblages of lichen communities vary at each spatial scale examined, in order to determine what scales should be included in future monitoring studies. We compared four sites in Italy, along gradients of atmospheric pollution and climate, to test the partitioning of the variance components of lichen diversity across spatial scales (from trunks to landscapes). Despite environmental heterogeneity, we observed comparable spatial variance. However, residuals often overcame between-plot variability, leading to biased estimation of atmospheric pollution effects.

Bioaccumulation with lichens: the Italian experience

Biological monitoring by means of lichens as accumulators of trace elements is a very suitable tool to assess and monitor air pollution and it has been adopted in several surveys in Italy in the last 30 years. In this paper, we try to make a critical analysis of this topic in order to understand the state of research and applications in this field. For this purpose, a database of the main field studies carried out in the last 30 years in Italy was prepared. The paper reports a survey of the characteristics of these studies. The aim is to take stock of the situation at present and to give a boost to the scientific community’s efforts to standardize the method at national and international level.

Accumulation of nitrogen and changes in assimilation pigments of lichens transplanted in an agricultural area

The results of a survey aimed at testing the hypothesis that the lichen Evernia prunastri, when transplanted in an agricultural area with high atmospheric NH3 concentrations, would respond to NH3 air pollution accumulating nitrogen in its thalli and showing changes in the concentration of assimilation pigments are presented. The results confirmed the hypothesis and showed that all lichen transplants accumulated nitrogen, suggesting that besides the release of atmospheric ammonia by animal stockfarms, the use of N-based fertilizers and the deposition of N-rich dust also may contribute to the high nitrogen availability to lichens in the study area. The result indicated that in the study area both the critical level of NH3 and the critical load of N for lichens are exceeded and physiological damage is to be expected in sensitive species. The results of assimilation pigments in E. prunastri, with a decrease in the concentration of chlorophylls a and b and carotenoids, as well as chlorophyll degradation to phaeophytin, confirmed this hypothesis. However, owing to the limited data set and pending further studies, these conclusions should be considered as limited to the study area.