Soil crust lichens in the El Cautivo badlands, SE Spain

Bevan, J. (1), Alexander, R. (1) & Lazaro Suau, R. (2)
(1) Dept. of Geography, University College Chester, Parkgate Rd. Chester, CH1 4BJ, UK; (2) EEZA, CSIC, c/ General Segura, 1, 04001, Almería, Spain

The El Cautivo badlands, in Almería province, SE Spain, experience a climate characterised by high temperatures and low, but very variable, precipitation. The site developed episodically through the late Quaternary producing a contemporary landscape of steep-sided gullies and more gentle pediments. Gradient and aspect strongly influence microclimatic conditions and, together with surface age, determine regolith depth and surface stability.
Vegetation reflects these, often sharp, environmental gradients. Vascular vegetation is sparse and patchy and lichen distribution seems, at first sight, eclectic. Their ability to cope with environmental stress enables lichens to occupy the least favourable sites where interaction with erosion processes produces an intense microtopography. Surfaces, inhospitable to vascular plants, develop a lichen crust variably dominated by Endocarpon pusillum, Diploschistes diacapsis, Squamarina lentigera and Lepraria crassissima. To establish whether such localised variations reflect distinct, recurring lichen communities, a stratified random survey was conducted. Multivariate analysis suggests that distinct assemblages can be identified and, on this basis, permanent monitoring and experimental plots have been established to investigate habitat and microclimatic relationships, physical site limitations and erosion resistance/recovery. Results of the survey and subsequent investigations are discussed.
This work forms part of project PECOS (Precipitation Patterns and Living Crusts in the Semi-Arid Mediterranean: A Sensor for Climate Change) funded by the Spanish Ministry of Science and Technology.


Lichen strategy-types on non-calcareous soils with a consideration of species richness

Bültmann, H.
Institute of Plant Ecology, University of Münster, Hindenburgplatz 55, D-48143 Münster, Germany

In this study, Grime´s CSR-model, well known for vascular plants, and During´s strategy-system, developed for bryophytes, were adjusted to terricolous lichens and lichen vegetation. 244 taxa were classified to 3 main and 4 subtypes of the Grimes and 5 types of the Durings model strategy-types. Lichen vegetation was studied using small plots (50cm x 50cm). In all, 488 plots were analyzed in temperate, boreal and low-arctic areas (N-Germany, N-Denmark, Finland, SE-Greenland) within vegetation of different disturbance and stress regime and different succession stages. Both strategy-systems are shown to fit for lichens. In the CSR-model nearly all known strategy-types could be found. In temperate and boreal study areas most terricolous lichens are Ruderals or Competitors. In the Arctic Stress-Tolerators gain importance. In During´s system most lichen species are Colonists, followed by Perennial Stayer, which are usually dominant in cover. The two strategy-systems were found to be partly overlapping and partly complementary: Grime´s focuses on the vegetative, During´s on the generative phase; Grime´s on intensity of stress and disturbance and During´s on periodicity. Vegetation of different succession stages showed the expected development respectively from Grime´s Ruderals to Competitors and from During´s Colonists to Perennial Stayers. In temperate and boreal areas, respectively Competitors and Perennial Stayers gain nearly 100% cover in late stages, which results in a strong decline in species richness. In the Arctic, respectively Competitors and Perennial Stayers also gain high cover values but only about 80 %, due to some amount of stress and especially small-scale disturbance. Thus species richness remains rather high. In general, species richness is positively correlated with strategy-type richness. The Low-Arctic study area shows by far the highest values of lichen richness (absolute max./mean per plot: Germany 19/8,5; Denmark 22/10; Finland 29/10,6; Greenland with impressive 47/18,6).


Ecology of endolithic Antarctic lichens

de los Ríos, A. (1), Wierzchos, J. (2), Sancho, L. G. (3) & Ascaso, C. (1)
(1) Centro de Ciencias Medioambientales (CSIC), Serrano 115 bis, 28006 Madrid, Spain; (2) Servei de Microscopia Electronica, UdL, Rovira Roure 44, Lleida, Spain; (3) Biologia vegetal II, Universidad Complutense de Madrid, 28040 Madrid, Spain

Fungi and algae living in symbiotic association as lichens are common internal colonizers of the lithic substrate and very frequent in the most extreme environments on Earth such as continental Antarctica. At the rock-atmosphere interface, lichenized alga and fungi along with free-living microorganisms are able to form biofilms (de los Ríos et al. 2002). The set of microbial communities comprising these biofilms, their biotopes and interelationships constitute an ecosystem which, given its small size, is denoted a microecosystem (de los Ríos et al., 2003). The different relationships existing among the lichenized and free-living microorganisms and the surrounding environment must be analysed from an microecological perspective. In situ microscopy is essential for these studies.
Chasmoendolithic and cryptoendolithic lichen thalli were the predominant organisms in endolithic biofilms of some Antarctic zones, while unlichenized cyanobacteria appeared as key components of endolithic biofilms in other zones where there were no lichen thalli nearby. Mycobionts were the biological component, which showed the most intense geophysical weathering on the lithic substrate. Biomobilization and biomineralization processes were also frequently observed in the proximity of lichen mycobionts. Within these biofilms, Temperature, relative humidity, pH and other factors diffiered from those of the external environment. Live/dead microbial fluorescence stains, such as BacLight Kit and FUN1, were used to identify the state of the microorganisms in diverse antarctic biofilms. Fungal hyphae showing different physiological state appeared intermixed in the lichen-dominated communities. The results demonstrate the predominance of living cells and confirm the protective role of biofilm structure.
References:
De los Ríos, A. et al. (2002). Microbial ecology 43, 181-188.
De los Ríos, A. et al. (2003). Environ. Microbiol. 5, 231-237.


The influence of environmental variables on epiphytic lichen diversity in Liguria (NW-Italy)

Giordani, P.
DIP.TE.RIS., University of Genova, Corso Dogali 1/c, I-16136 Genova, Italy

Lichen monitoring surveys mainly regard the effects of atmospheric pollution. This method is based on the observation that lichens are extremely sensitive to the main atmospheric pollutants. However, lichen diversity is a complex variable, also depending on other environmental factors, and it is not always possible to discern the causes of its variability. Here, the results are provided for a case study carried out in Liguria (NW-Italy) for assessing the lichen diversity in relation to different kinds of environmental factors. A total of 165 sampling stations were releved on the basis of a stratified random sample, based on habitat and altitude. At the selected coordinates, all the standard trees within 30 m radius plots were considered. At each of the selected trees, the Index of Lichen Diversity was releved, by means of four 10 x 50 cm grids placed systematically on cardinal points N, E, S, W at 100 cm above the ground level. As a result, macroclimatic variables, namely average yearly rainfall and temperature, are shown to be the most important factors related to lichen diversity in Liguria, together with different kinds of habitat. Further, multivariate analysis allowed to detect the effects of several anthropogenic alterations: atmospheric pollution is the most important disturbance factor in lowlands and coastal areas; forest management and fires threat lichen diversity in remote areas. Finally, the results obtained also provide useful information for different applications: 1) to improve the interpretation of biomonitoring data in different bioclimatic regions; 2) to establish priority conservation areas on the basis of quantitative data; and 3) to plan long-term monitoring of global change using indicator species.


Manganese as a site factor for epiphytic lichens

Hauck, M. & Paul, A.
A. v. Haller Institute of Plant Sciences, University of Goettingen, Germany

Cover of the epiphytic lichen Hypogymnia physodes decreases with increasing Mn content of bark or stemflow in coniferous forests of Europe and North America. Multiple experimental evidence suggests that these correlations are causal. Excess Mn reduces, e.g., soredia viability, chlorophyll content, chloroplast integrity, autospore formation by the Trebouxia photobiont as well as the frequency of mesosome-like vesicles and concentric bodies. Ca, Mg, and Fe alleviate Mn-caused damage in H. physodes, e.g., by reducing chlorophyll degradation.
Cover of Lecanora conizaeoides is not correlated with Mn concentrations in bark or stemflow. This agrees with experimental results that, e.g., Mn does not cause chlorophyll degradation in this species. Total intracellular Mn uptake is the same in H. physodes and L. conizaeoides, but the latter is capable of maintaining a significantly lower level of free Mn. This is because L. conizaeoides immobilizes Mn more effectively than H. physodes in polyphosphate bodies as well as in sulphur-contain deposits, which may be phytochelatines.
The Mn that influences epiphytic lichens via bark and stemflow is primarily soil-borne. It is taken up by the tree roots and deposited, after xylem transport and radial translocation, in the bark. Mn in stemflow primarily derives from leaching from needles and bark. On balance, our results suggest that excess Mn is an important site factor for epiphytic lichens, at least in coniferous forests of Europe and North America, that has been overlooked, so far. This site factor is natural, but may have become even more significant due to anthropogenic soil acidification, which increases Mn availability.


Spatial distribution of epiphytic lichens on aspen, at stand and landscape level

Hedenås, H.
Department of Ecology and Environmental Science, University of Umeå, Umeå, Sweden

Two correlative studies in which the distribution of a set of three epiphytic lichens with contrasting dispersal strategies, has been carried out. One sexually dispersed species, Collema curtisporum and two asexually dispersed species, C. furfuraceum and Leptogium saturninum, were investigated, all living on aspen (Populus tremula). The habitat is composed of discrete patches (trees) with a limited life-span both as individual units and as stands in the landscape. The epiphytes therefore depend on repeated colonization both within and between stands.
In the first study, we examined the spatial distribution of the three lichens species in two aspen stands in the forest. In the second study, we examined the occurrence of the three lichen species in four aspen rich and four aspen poor landscapes.
At stand level, it was revealed that the sexually dispersed species, C. curtisporum, was more aggregated than the host trees, while the distribution of the asexually dispersed species mirrors the distribution of their host.
At landscape level, the frequency, of the two Collema species decreased with the decline of aspen in the landscapes. C. furfuraceum, population size decreased in a higher proportion than predicted from percent of aspen in the landscape, while the decline of C. curtisporum in a stand was proportional to the percent of aspen in the landscape. L. saturninum was not affected by the amount of aspen in the landscape.
Our results indicate that data derived from one spatial scale are not necessary applicably on another scale. However, altogether, the observed patterns in our data are consistent with suggestions that species with spores are adapted to long distance dispersal allowing colonization of suitable sites. Species with isidia are instead adapted to short distance dispersal within habitats with small-scale disturbances and may build up large local populations.


Impacts on lichens and bryophytes of alternative silvicultural regimes in Tasmania's wet forest: preliminary results

Kantvilas, G. & Jarman, S. J.
Tasmanian Herbarium & Forestry Tasmania, Hobart, Tasmania, Australia

Logging in Tasmania's wet eucalypt forests has traditionally been based on a clearfell, burn and sow regime, a process that has become increasingly controversial in recent years. The managing authority for these forests, Forestry Tasmania, has designed a Silvicultural Systems Trial in Tasmania's Southern Forests to explore alternative methods for harvesting and regenerating eucalypts. One of the components of this Trial is a study of lichens and bryophytes. This work is based on 12 study plots representing four silvicultural treatments plus a control. Pre-logging surveys have been completed and revealed a diverse flora comprising 134 lichen taxa and 144 bryophyte taxa. Re-sampling of the study plots following logging is now underway, based at this stage on approximately one-year, three-year and five-year intervals. The post-logging lichen and bryophyte flora is dominated by new incursions that represent transient fire-weeds, but survivors or re-colonisers that represent components of the pre-logging flora are also present. Floristic differences between the treatments could be detected from the time of the first post-harvest sampling and are directly attributable to the type of habitats for cryptogams that are available.


Epiphytic lichens in a fragmenting boreal forest landscape

Kivistö, L.
University of Helsinki, Finland

Many forest species are subjected to increasing habitat fragmentation. The ultimate consequences of this may not be easily observed in the slowly developing lichen flora. We studied two regions in Finland with different forest utility histories. In the southern region most forests have been effectively managed for decades and the remaining old-growth stands are isolated, whereas in the middle-eastern region the more numerous and comparatively large old-growth stands have not been as effectively isolated. Lichen diversity in 41 old-growth forest fragments was recorded by mapping the occurrence and abundance of old-growth forest indicator species and all epiphytic lichens growing on Picea abies. Explanatory data on stand characteristics, including information on fragmentation history, were also recorded. The data was analysed with non-metric multidimensional scaling (NMS). The ordination analyses indicated that the two regions differed in species composition, and that especially old-growth forest indicator species in southern Finland had been negatively affected by habitat fragmentation. Early phases of a similar trend were observed in effectively isolated old-growth forest stands in middle-eastern Finland. It seems that conserving small, isolated old-growth stands will not be enough for maintaining a high epiphyte diversity in the forests of our region. In managed boreal forests the continuous availability of certain key substrates, like trunks of old deciduous trees, could significantly improve the survival of sensitive old-growth indicator species.


Populations of epiphytic lichens under stress conditions: survival strategies

Mikhailova, I.
Institute of Plant and Animal Ecology UD RAS, Ekaterinburg, Russia

Spatial, dimensional and functional structures of populations of Hypogymnia physodes and Tuckermanopsis sepincola were studied in undamaged stands and in the vicinity of a copper smelter in the Middle Urals. The species are similar in their sensitivity to air pollution but differ in their life strategies. In undamaged stands, asexually reproduced H. physodes is a strong competitor and dominates in all epiphytic communities. Sexually reproduced T. sepincola is a pioneer species and is often overgrown by H. physodes at the next stage of succession. However, high mortality rates are compensated by high dispersal ability, so the background population of T. sepincola is "permanently young": 58% of thalli are sterile, and only 22% of thalli bear developed apothecia and sustain the population density. Emissions from the smelter inhibit development of H. physodes thalli so that functional structure of the population shifts toward esorediate and poor-sorediate thalli (= younger individuals). Insufficiency of soredia producers causes a sharp decrease in the population density. On the contrary, the density of T. sepincola population at the polluted site exceeds the background level in spite of an obvious decrease in the developmental rates of thalli (direct effect of the stress factor). In the absence of competition, longevity of thalli increases, which is evident from the population structure (52% of thalli bear developed apothecia, and only 17,7% are sterile). Thus, two species with different life strategies differ in their population structure both at the background site and at the border of the "lichen desert." The pioneer species proves to be more successful under an abiotic stress factor (toxic load) due to competitive release, a secondary effect of the stress factor. "Cost" of spore production appears to be lower as compared to that of soredia, and this probably plays a decisive role in survival under stress conditions. Two opposite patterns of population response to air pollution (shift toward either young or old individuals) are similar to those found for higher plants though their mechanisms can differ between lichens and plants.


Epiphytic cyanolichens: ecology, conservation, and directions for future research

Sillett, S. C. & Antoine, M. E.
Department of Biological Sciences, Humboldt State University, Arcata, California, USA

Lichens containing cyanobacterial photobionts occupy intermediate positions along moisture gradients at multiple scales. The richness and abundance of cyanolichens peak in moist forests with a summer dry season. In drier forests, chlorolichens dominate epiphyte communities, while bryophytes overwhelm lichens in rain forests. The vertical distribution of cyanolichens shifts during forest development. Dispersal limitation delays cyanolichen colonization of young forests. They accumulate slowly, moving upwards in the canopy at rates proportional to moisture availability. In very old rain forests, cyanolichens become restricted to the upper canopy, having been excluded elsewhere by aggressive, colonial bryophytes. Slow dispersal and an intolerance of prolonged hydration may also explain their horizontal distribution along tree branches in wet forests, where they tend to be flanked by chlorolichens distally and bryophytes basally. Cold temperatures limit cyanolichen accumulation by precluding nitrogen fixation, explaining their low abundances in boreal forests and high-elevation temperate forests. In tropical rain forests as well as temperate forests with rainy summers, cyanolichens are also scarce, because they cannot achieve the high photosynthetic rates necessary to overcome respiratory energy losses during warm, wet periods. Even in old-growth forests where they are abundant, the crowns of some tree species are relatively inhospitable to cyanolichens. Efforts to conserve epiphytic cyanolichens in managed forests will benefit from recognition of their dispersal limitations and substrate preferences. Now that access to forest canopies is easy and safe, the causal factors underlying patterns of cyanolichen distribution and abundance should be addressed with manipulative experiments. Transplanting thalli and propagules, irrigation of substrates, and microclimatic monitoring have great potential to advance our global understanding of these important lichens.

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