Fine spatial pattern of an epiphytic lichen species is affected by habitat conditions in two forest types in the Iberian Mediterranean region

Persistence and abundance of species is determined by habitat availability and the ability to disperse and colonize habitats at contrasting spatial scales. Favourable habitat fragments are also heterogeneous in quality, providing differing opportunities for establishment and affecting the population dynamics of a species. Based on these principles, we suggest that the presence and abundance of epiphytes may reflect their dispersal ability, which is primarily determined by the spatial structure of host trees, but also by host quality. To our knowledge there has been no explicit test of the importance of host tree spatial pattern for epiphytes in Mediterranean forests. We hypothesized that performance and host occupancy in a favourable habitat depend on the spatial pattern of host trees, because this pattern affects the dispersal ability of each epiphyte and it also determines the availability of suitable sites for establishment. We tested this hypothesis using new point pattern analysis tools and generalized linear mixed models to investigate the spatial distribution and performance of the epiphytic lichen Lobaria pulmonaria, which inhabits two types of host trees (beeches and Iberian oaks). We tested the effects on L. pulmonaria distribution of tree size, spatial configuration, and host tree identity. We built a model including tree size, stand structure, and several neighbourhood predictors to understand the effect of host tree on L. pulmonaria. We also investigated the relative importance of spatial patterning on the presence and abundance of the species, independently of the host tree configuration. L. pulmonaria distribution was highly dependent on habitat quality for successful establishment, i.e., tree species identity, tree diameter, and several forest stand structure surrogates. For beech trees, tree diameter was the main factor influencing presence and cover of the lichen, although larger lichen-colonized trees were located close to focal trees, i.e., young trees. However, oak diameter was not an important factor, suggesting that bark roughness at all diameters favoured lichen establishment. Our results indicate that L. pulmonaria dispersal is not spatially restricted, but it is dependent on habitat quality. Furthermore, new spatial analysis tools suggested that L. pulmonaria cover exhibits a distinct pattern, although the spatial pattern of tree position and size was random.     

Remnants fragments preserve genetic diversity of the old forest lichen <Emphasis Type="Italic">Lobaria pulmonaria</Emphasis> in a fragmented Mediterranean mountain forest

Fragmentation represents a serious threat to biodiversity worldwide, however its effects on epiphytic organisms is still poorly understood. We study the effect of habitat fragmentation on the genetic population structure and diversity of the red-listed epiphytic lichen, Lobaria pulmonaria, in a Mediterranean forest landscape. We tested the relative importance of forest patch quality, matrix surrounding fragments and connectivity on the genetic variation within populations and the differentiation among them. A total of 855 thalli were sampled in 44 plots (400 m²) of 31 suitable forest fragments (beeches and oaks), in the Sierra de Ayllón in central Spain. Variables related to landscape attributes of the remnant forest patches such as size and connectivity and also the nature of the matrix or tree species had no significant effects on the genetic diversity of L. pulmonaria. Values of genetic diversity (Nei’s) were only affected by habitat quality estimated as the age patches. Most of the variation (76%) in all populations was observed at the smallest sampled unit (plots). Using multiple regression analysis, we found that habitat quality is more important in explaining the genetic structure of the L. pulmonaria populations than spatial distance. The relatively high level of genetic diversity of the species in old forest patches regardless of patch size indicates that habitat quality in a highly structured forest stand determines the population size and distribution pattern of this species and its associated lichen community. Thus, conservation programmes of Mediterranean mountain forests have to prioritize area and habitat quality of old forest patches.     

西双版纳片段化石灰岩森林附生兰科植物多样性研究

西双版纳石灰岩地区拥有丰富的兰科植物资源,但近年来随着橡胶树的大面积种植,使得该地区很多石灰岩森林呈片段化。为了解片段化石灰岩森林中附生兰科植物多样性状况以及片段化对附生兰科植物的影响,该研究选取了生境片段化的青岩寨和曼纳览,以及连续生境的绿石林和巴卡新寨等4个样地的29个样方进行多样性调查和对比研究。结果表明:4个石灰岩森林样共记录到附生兰科植物34属76种1 528株(丛)。通过对坡向、坡度、海拔、地形、郁闭度和森林类型等6个环境因子与附生兰科植物丰富度进行CCA分析,发现石灰岩地区附生兰科植物的分布主要受海拔和森林类型2个因素的影响,在海拔较高的青岩寨和巴卡新寨附生兰科植物物种丰富度高于低海拔的绿石林和曼纳览,而片段化对附生兰科植物的物种多样性和多度均无显著影响,这可能与片段化的历史较短有关。虽然目前来看生境片段化对石灰岩地区的附生兰科植物多样性无显著影响,但生境脆弱的石灰岩森林植被的保护对于兰科植物多样性保护则更具重要性。     

Non-dominant trees significantly enhance species richness of epiphytic lichens in subtropical forests of southwest China

Host species has an important influence on the distribution of epiphytic lichens in forests. However, the importance of non-dominant trees in shaping lichen communities has been poorly studied owing to the relative rarity of individuals. The importance of dominant and non-dominant trees for distribution of epiphytic lichens was determined in eight subtropical forests in southwestern China. Dominant trees supported more abundant total and exclusive lichen species only in secondary forests. The occurrence of non-dominant trees promoted lichen diversity within forest types and influenced lichen communities on both tree groups. The effects of total tree species on lichen distribution largely resulted from the presence of non-dominant trees. Dominant and non-dominant trees supported distinct lichen assemblages within forest types, and ordination analyses showed a clear separation. Our study, therefore, reinforces the importance of non-dominant trees for conserving epiphytic lichens, and highlights that lichen assemblages are shaped by both dominant and non-dominant trees.     

Is local distribution of the epiphytic lichen <Emphasis Type="Italic">Lobaria pulmonaria</Emphasis> limited by dispersal capacity or habitat quality?

By surveying and re-surveying 12 forest sites in southern Sweden for the epiphytic lichen Lobaria pulmonaria with a 9-year interval, and measuring tree-related habitat quality variables, we have investigated whether the local distribution of the lichen is limited by poor dispersal capacity or by habitat quality. Dispersal distances were measured indirectly as the distances between colonised trees and the nearest trees occupied by L. pulmonaria in both 1992 and 2001. To compare habitat quality between trees occupied by L. pulmonaria and neighbouring control trees, we recorded tree species and measured age and growth rate of trees, light conditions, bark structure and bryophyte cover. The estimated mean dispersal distance was 35 m, with a recorded maximum of 75 m. Occupied trees were larger and had a larger cover of bryophytes than unoccupied trees of similar size. The results indicate that dispersal capacity probably is the most important factor in limiting the local distribution of L. pulmonaria, but habitat-quality factors may be important on a smaller spatial scale.     

Small mammal assemblages in a disturbed tropical landscape at Pozuzo,Peru

Deforestation in the Peruvian pre-montane forests has increased alarmingly in recent years. Particularly, fragmentation in these forests takes place against a background of very extensive continuous forest. Until now, no studies have detailed how Peruvian small mammals responded to forest fragmentation. In this paper, we report the results of an assessment of nonvolant small mammal fauna in forest remnants (one large fragment and one small fragment) and cattle pasture in a disturbed landscape at Pozuzo, formerly a pre-montane tropical forest in central Peru. In each forest remnant, we quantify habitat parameters and identified small mammals to know if there is a relationship between forest remnant size or microhabitat structure and small mammal assemblages. In addition, we investigated the influence of habitat structure on the presence of small mammal species. We did not find any evidence that habitat structure in large fragment was greater than small fragment. Actually, both forest remnants presented habitat features typical of forests subject to higher levels of disturbance. We found that abundance of small trees (10 - 19 cm DBH) was positively associated with the presence of Marmosops noctivagus, but negatively with the presence of Oecomys bicolor. Likewise, the presence of the arboreal Rhipidomys leucodactylus was associated with the abundance of larger trees (DBH > 50 cm). We recorded 12 small mammal species in large fragment, 9 in small fragment and 3 in cattle pasture. No significant differences were found in species richness between both fragments, but marsupial abundance in the small fragment was greater than large fragment. At Pozuzo, we recorded 9 species restricted to forest habitat and 3 to forest and cattle pastures. However, it is necessary to assess more fragments to improve our knowledge about species survival in this landscape.     

Epiphytic and epixylic lichen species diversity in Estonian natural forests

The epiphytic and epixylic lichen flora of natural forests was recorded in different parts of Estonia. Altogether 232 taxa of lichens, lichenicolous fungi, or non-lichenized fungi were recorded, 10 of them listed in the Estonian Red Data Book. We found regional differences in lichen species composition and diversity caused by differences in the forest types. The tree-species-rich boreo-nemoral forests had the most diverse lichen flora, while the boreal forest dominated by coniferous trees or birch had the lowest diversity. The stand age proved to be significant in regard to the number of lichen species in a forest. The most remarkable effect on the diversity of forest lichen species was caused by the presence of Populus tremula. Aspen had the highest number of lichen species on the basal trunk and twigs, and also the highest number of host-specific lichen species.     

Forest edge-interior differentiation in the epiphytic lichen diversity of the forest steppe in the Khangai Mountains,Mongolia

Aims The effects of traditional land use by mobile livestock keepers on biodiversity in forest steppe ecotones are insufficiently studied. Epiphytes are an important part of forest plant diversity. Here we analyze differences in the diversity and composition of the epiphytic lichen vegetation between the edge and the interior of Siberian larch forests in the Khangai Mountains, western Mongolia, which are highly subdivided into patches. We asked whether the epiphytic lichen vegetation at the forest edge differs significantly from that in the interior, whether the edge is inhabited by more nitrophilous species than the interior and whether the density of nomad camps around the forest affects epiphytic lichen diversity.Methods Cover percentages of epiphytic lichen species were recorded from 20 trees per plot on 6 plots in the interior and 6 plots at the edge of Larix sibirica forests. The position of nomad summer camps was surveyed using Global Positioning System. Data were analyzed with pairwise significance tests, analysis of similarities, nonmetric multidimensional scaling and canonical correspondence analysis.Important findings The composition of the epiphytic lichen vegetation clearly differed between the two habitats, with more species being more frequent at the edge than in the interior. However, there was no difference in species richness (α-diversity). The epiphyte vegetation at the edge was more uniform and characterized by lower variation of tree-level α-diversity and lower β-diversity than in the interior. At the edge, only nitrophytic lichens were dominant, whereas in the interior, nitrophytes and acidophytes were among the dominant species. This pattern is probably attributable to the spatial heterogeneity of the intensity of forest grazing and was shown to be influenced by the density of nomad summer camps in the vicinity of the forests. Tree-level α-diversity increased with stem diameter, but high-diameter trees were rare. The results suggest that the present level of forest patchiness and the effect of forest grazing increases the diversity of epiphytic lichens on the landscape level, while logging of high-diameter trees reduces lichen diversity.     

Spatial pattern in the occurrence of the lichen Lobaria pulmonaria in managed and virgin boreal forests

Two populations of the lichen Lobaria pulmonaria. growing on aspens and goat willows in 12 and 20 km² study areas of boreal forest in Finland, were surveyed thoroughly to investigate the factors influencing the spatial distribution of the lichen. In one study area, where forestry has been intensive and old-growth forest is highly fragmented, L, pulmonaria was sparse and grew mostly on willows. In contrast, a large and continuous virgin forest area supported a higher incidence of L. pulmonaria. with the lichen being common on both aspens and willows. In both study areas, the distributions of aspen and willow were clumped over the scales of 100-1000 m. The spatial pattern of L pulmonaria was more clumped in the managed forest than in the virgin forest. The reduced incidence of the lichen on aspens in the managed area was attributed to a disruption of habitat continuity and small average tree size. There was no comparable reduction in the incidence on willows, probably because the willow had a very aggregated distribution in the managed area, which probably facililated local colonization of the lichen. Presence of the lichen was significantly related to size-corrected local density of aspen and willow trees as well as to spatial connectivity to neighboring lichen-occupied trees.     

Landscape-level gene flow in Lobaria pulmonaria, an epiphytic lichen

Epiphytes are strongly affected by the population dynamics of their host trees. Owing to the spatio-temporal dynamics of host tree populations, substantial dispersal rates--corresponding to high levels of gene flow--are needed for populations to persist in a landscape. However, several epiphytic lichens have been suggested to be dispersal-limited, which leads to the expectation of low gene flow at the landscape scale. Here, we study landscape-level genetic structure and gene flow of a putatively dispersal-limited epiphytic lichen, Lobaria pulmonaria. The genetic structure of L. pulmonaria was quantified at three hierarchical levels, based on 923 thalli collected from 41 plots situated within a pasture-woodland landscape and genotyped at six fungal microsatellite loci. We found significant isolation by distance, and significant genetic differentiation both among sampling plots and among trees. Landscape configuration, i.e. the effect of a large open area separating two forested regions, did not leave a traceable pattern in genetic structure, as assessed with partial Mantel tests and analysis of molecular variance. Gene pools were spatially intermingled in the pasture-woodland landscape, as determined by Bayesian analysis of population structure. Evidence for local gene flow was found in a disturbed area that was mainly colonized from nearby sources. Our analyses indicated high rates of gene flow of L. pulmonaria among forest patches, which may reflect the historical connectedness of the landscape through gene movement. These results support the conclusion that dispersal in L. pulmonaria is rather effective, but not spatially unrestricted.     

Functional composition and phenology of fruit-feeding butterflies in a fragmented landscape: variation of seasonality between habitat specialists

For butterflies, tolerance to the matrix may be an important criterion of habitat occurrence in fragmented landscapes. Here we examine the relative effects of habitat fragmentation and the surrounding agricultural matrix on the functional composition of fruit-feeding butterflies of the Atlantic rain forest in southeastern Brazil. Generalized linear models were used to detect the effects of landscape metrics on butterfly richness and abundance of the total assemblage and functional groups. Circular statistics were used to analyze the patterns of monthly abundance of the total assemblage and functional groups in the forest remnants and the surrounding matrices. In total, 650 butterflies representing 57 species were captured; species composition differed significantly between the forest fragments and the surrounding matrices. We recorded 22 forest specialists, 18 matrix specialists, 11 common species with matrix preference and six common species with forest preference. Forest connectivity favored the richness of forest specialists, while habitat fragmentation enhances the richness and abundance of matrix-tolerant species. Circular analysis revealed that forest specialists were more abundant in the rainy season while matrix-tolerant species proliferated in the dry season. Although maintaining connectivity of forest fragments may increase the mobility and dispersion of forest species, our results showed that landscape fragmentation modify butterfly assemblage by promoting an increase of matrix tolerant species with detriment of forest specialists.     

云南哀牢山原生林及次生林群落附生地衣物种多样性与分布

附生地衣是森林附生植物的重要类群之一, 在维护森林生态系统的物种多样性以及水分和养分循环等方面发挥着重要作用。作者于2005年12月至2006年5月利用树干取样法调查了云南哀牢山徐家坝地区原生山地常绿阔叶林及其次生群落栎类萌生林、滇山杨(Populus bonatii)林和花椒(Zanthoxylum bungeanum)人工林中525株不同种类和径级树木距地面 0–2.0 m处附生地衣的组成和分布, 并收集了各个群落地面上凋落的地衣, 分析了林冠层附生地衣的物种组成。研究结果表明, 该区森林中附生地衣物种比较丰富。共收集到附生地衣61种, 分属17科29属, 其中原生林、栎类萌生林、滇山杨林和花椒人工林分别有51、53、46和23种。在树干距地面 0–2.0 m位置, 各群落中的附生地衣组成明显不同;但在林冠层中, 各群落内的附生地衣基本相似。原生林中附生地衣种类较多, 但分布不均匀。树干附生地衣的Shannon-Wiener和Simpson多样性指数以栎类萌生林最高, 分别为2.71和0.89;花椒林和滇山杨林次之, 分别为2.43–2.45和0.88–0.89;原生林最低, 为1.25和0.67。树干方位、宿主种类和宿主径级等都对附生地衣的物种组成和多样性有着重要影响, 附生地衣更多地出现于树干南向方位, 云南越桔(Vaccinium duclouxii)的附生地衣最为丰富, 胸径5.0–25.0 cm的树木上附生地衣较多。哀牢山山地森林群落中丰富的附生地衣种类及物种多样性在维系本区山地森林生态系统生物多样性格局方面具有重要的作用。     

Diversity and abundance of birds in relation to forest fragmentation,habitat quality and heterogeneity

This study investigated the importance of habitat quality and habitat heterogeneity for the abundance and diversity of breeding birds in continuous forest and in forest fragments surrounded by farmland in central Sweden. Positive correlations were found between species number and area, volume of Aspen Populus tremula and habitat heterogeneity. Spatial segregation of habitats at a relatively fine-grained scale is suggested to allow for the co-occurrence of more species. The abundance of at least 18 of the species in this study was influenced by fragmentation, and nine of these species preferred fragments to forest sites. The total density of birds was higher in fragments than in forest sites, probably because several fragment species forage in farmland surrounding the sites and a few also forage at edges. Nine species were more common in forest sites than in fragments, but only one species was restricted to continuous forest. However, several fragments were relatively close to forests (150 m) and forest was common in larger scale contexts. The abundance of most species (25 of 33 species) in this study was correlated with habitat quality variables (i.e. variables measuring the size, volume and diversity of ‘tree species’). Among these habitat variables the most important was the occurrence of deciduous trees which seemed to be important for 14 species. The second most important habitat factor seemed to be the diameter of trees, which was positively correlated with the abundance of eight species of which five are hole-nesters. Among coniferous trees, six species were positively correlated with the volume of Norway Spruce Picea abies, whereas no species seemed to be correlated with the volume of Pine Pinus sylvestris.     

Responses of the distribution of four epiphytic cyanolichens to habitat changes in subtropical forests

 蓝藻地衣是附生植物类群的重要组成部分, 在森林生态系统的环境监测和养分循环中发挥着重要作用。该研究在云南哀牢山亚热带森林系统的2种原生和6种次生森林群落中, 以粉缘绵毛衣(Leioderma sorediatum)、天蓝猫耳衣(Leptogium azureum)、网肺衣(Lobaria retigera)和双缘牛皮叶(Sticta duplolimbata) 4种常见蓝藻地衣为对象, 共设立120个样地, 调查了它们在3 600株树木0–2 m树干上的分布, 探讨其分布特征及与森林类群、宿主种类以及林龄等生境因子的关系。研究发现4种蓝藻地衣在森林群落间的分布模式明显不同。除双缘牛皮叶的盖度和频度在原生苔藓矮林中最高外, 其他3种蓝藻地衣的最高值均出现于次生林如厚皮香(Ternstroemia gymnanthera)林和滇山杨(Populus bonatii)林中; 而哀牢山地区广布的原生木果柯(Lithocarpus xylocarpus)林中, 4种蓝藻地衣极为少见。4种地衣都能生长于10多个树种上, 但明显表现出对厚皮香、滇山杨和硬壳柯(Lithocarpus hancei)等树种的偏好性, 以及对小花山茶(Camellia forrestii)等的排斥性。森林群落的林龄、胸径、最大胸径、林冠开阔度、基面积、树木密度和树种多样性等因子的变化均对4种附生蓝藻地衣的分布产生重要影响, 但在景观尺度上影响程度相对较小, 在不同森林群落内部却有各自的重要作用。其中, 林龄、林冠开阔度和宿主胸径是影响蓝藻地衣分布的最重要的生境因子。     

Tree and stand-scale factors affecting richness and composition of epiphytic bryophytes and lichens in deciduous woodland key habitats

Conservation and sustainable forestry are essential in a multi-functional landscape. In this respect, ecological studies on epiphytes are needed to determine abiotic and biotic factors associated with high diversity. The aim of the present study was to evaluate relative sensitivity of conservation targets (epiphytic bryophytes and lichens) in relation to contrasting environmental variables (tree species, tree diameter at breast height, bark crevice depth, pH, tree inclination, pH, forest stand age, area and type) in boreo-nemoral forests. The study was conducted in Latvian 34 woodland key habitat (WKH) boreo-nemoral forest stands. Generalized linear mixed models and canonical correspondence analysis showed that tree species and tree bark pH were the most important variables explaining epiphytic bryophyte and lichen composition and richness (total, Red-listed, WKH indicator species). Forest stand level factors, such as stand size and habitat type, had only minor influence on epiphytic species composition and richness. The results of the present study indicate a need to maintain the diversity of tree species and large trees, particularly Acer platanoides, Carpinus betulus, Fraxinus excelsior, Populus tremula, Tilia cordata, Ulmus glabra and Ulmus laevis in conservation of epiphytic bryophyte and lichen communities in the future.     

Tree species and microhabitat influence the population structure of the epiphytic lichen Lobaria pulmonaria

Detailed knowledge of the habitat requirements of species is required because habitat greatly affects the persistence of species. We investigated the effects of tree species and microhabitat heterogeneity on the population of the locally threatened lichen Lobaria pulmonaria. We studied four L. pulmonaria populations in Central Spain and collected microhabitat data for individuals growing on beech and oak. The microhabitat affected the life stages of L. pulmonaria; being a phorophyte species the location of the lichen was the most important factor generating different patterns of establishment, abundance, thallus size and reproductive capacity. Although oak forests favoured the establishment and recruitment of new L. pulmonaria individuals, they apparently provided adverse environmental conditions for lichen growth, thus affecting the reproductive capacity since this is size-dependent. By contrast, beech forests offered a more favourable microclimate, because L. pulmonaria individuals reached larger sizes in these forests. In conclusion, our results indicate that habitats hosting large populations, with high rates of establishment and recruitment do not necessarily favour other life-cycle stages.     

Gastropod grazing of epiphytic lichen-dominated communities depends on tree species

Tree species differ in longevity, canopy structure, and bark texture, chemistry and water storage. Tree species-specific traits play a role in shaping epiphytic vegetation and likely influence the community assembly of organisms feeding on epiphytes. Lichenivorous gastropods, species with calcium-rich shells in particular, need calcium and likely occur more abundantly in and around tree species with high available calcium. We quantified gastropod grazing on the epiphytic lichens Lobaria pulmonaria and Lobaria scrobiculata transplanted to blocks of adjacent trunks of Acer platanoides, Quercus robur and Tilia cordata. We tested the hypothesis that tree species known to have more available Ca, exhibit more grazing damage on transplanted lichens than trees with lower Ca-availability. The grazing pressure was 1.6–1.8 times higher for lichen transplants on Acer and Tilia known to produce litter with easily soluble Ca than on Quercus, which binds Ca as oxalate. Trees with a high grazing pressure on transplants had greater natural abundance of Lobaria virens than of L. pulmonaria. Gastropods preferred L. scrobiculata to L. pulmonaria, evidenced by more observed grazing marks and greater measured biomass loss. We attribute this difference to the lower concentration of carbon-based secondary compounds in L. scrobiculata. However, the strength of the preference varied between the three tree species receiving lichen transplants and was strongest on A. platanoides, while gastropods on T. cordata grazed equal amounts of each transplanted lichen. In conclusion, tree species influenced grazing patterns of gastropods on epiphytic lichens. In addition to bark pH and other factors, we have shown that tree species-specific differences in grazing pressure play a role in shaping the epiphytic macrolichen community.     

Hitchhiking with forests: population genetics of the epiphytic lichen Lobaria pulmonaria in primeval and managed forests in southeastern Europe

Availability of suitable trees is a primary determinant of range contractions and expansions of epiphytic species. However, switches between carrier tree species may blur co‐phylogeographic patterns. We identified glacial refugia in southeastern Europe for the tree‐colonizing lichen Lobaria pulmonaria, studied the importance of primeval forest reserves for the conservation of genetically diverse populations and analyzed differences in spatial genetic structure between primeval and managed forests with fungus‐specific microsatellite markers. Populations belonged to either of two genepools or were admixed. Gene diversity was higher in primeval than in managed forests. At small distances up to 170 m, genotype diversity was lower in managed compared with primeval forests. We found significant associations between groups of tree species and two L. pulmonaria genepools, which may indicate “hitchhiking” of L. pulmonaria on forest communities during postglacial migration. Genepool B of L. pulmonaria was associated with European Beech (Fagus sylvatica) and we can hypothesize that genepool B survived the last glaciation associated within the refuge of European Beech on the Coastal and Central Dinarides. The allelic richness of genepool A was highest in the Alps, which is the evidence for a northern refuge of L. pulmonaria. Vicariant altitudinal distributions of the two genepools suggest intraspecific ecological differentiation.     

Edge and land-use effects on epiphytic lichen diversity in the forest-steppe ecotone of the Mongolian Altai

Epiphytic lichen diversity was studied in forests of Siberian larch (Larix sibirica) in the forest-steppe ecotone of the Mongolian Altai. These forests are utilized for livestock grazing, fuelwood collection and occasional logging by pastoral nomads. The density of nomad households in the proximity of the forests influences epiphytic lichen diversity more strongly than the position of sample trees in the forest interior or at the forest line to the steppe. This suggests that land use exerts a stronger effect on lichen diversity than the distinct gradient in microclimate between the forest interior and the forest edge. The co-occurrence of nitrophytes with anitrophytic acidophytes on a small spatial scale as well as higher N and Ca concentrations and pH values in the bark of larch trees at the forest edge than in the forest interior indicate that moderate livestock grazing increases the epiphytic lichen diversity due to an increase of the diversity of chemically different microhabitats. Preference of many lichen species (and of rare species in particular) for overmature and decaying trees suggests that logging and fuelwood collection has adverse effects on epiphytic lichen diversity. This adverse effect is likely to be more crucial for lichen diversity than the putatively positive effect of livestock grazing, since more lichens with a preference for old and decaying trees than for nitrogen-enriched bark were found. The present study is the first one investigating the impact of pastoral nomadism in Central Asia on epiphyte diversity.     

Isolation affects tree‐scale epiphytic lichen community structure on New Zealand mountain beech trees

Question: Is epiphytic lichen community structure significantly affected by isolation from source community? Location: Foothills of the Southern Alps, South Island, New Zealand. Methods: Epiphytic lichen richness and environmental variables were measured on 382, young Nothofagus solandri var. cliffortioides (Hook. f.) Poole (mountain beech) trees that had recently colonized grassland adjacent to a forest remnant. Richness and the presence of individual lichen taxa were modelled as a function of isolation from the forest fragment, tree size and other habitat conditions. Results: Richness of epiphytic lichen communities was negatively related to tree isolation, although this effect was much smaller than the effects of tree size and other local (tree‐scale) habitat conditions. Different lichen taxa responded in different ways to isolation, area effects and local habitat conditions. Conclusions: This study shows that many epiphytic lichens on mountain beech are limited in their ability to colonize new substrate, even over distances of less than 1 km, which may be due to limitation in dispersal and/or establishment. Lichens are greatly influenced by local habitat conditions, such as tree size, and in this particular environment their negative interaction with sooty moulds is an important driver of community structure.