91454462
Beyond forest habitat qualities: Climate and tree characteristics as the major drivers of epiphytic macrolichen assemblages in temperate mountains
Co-ordinating Editor: Hans Henrik Bruun Abstract Questions: How are epiphytic macrolichen assemblages shaped by forest habitat quality as reflected by the availability of latedevelopmental forest attributes (i.e., stand maturity) and the temporal continuity of the wooded state (i.e., forest continuity)? Are these two forest habitat features the main drivers of lichen assemblages, and if so, at which spatial scale? Study Site: Temperate mountain forests in the French Northern Alps. Methods: In our sampling design, we defined treatments by crossing forest continuity (ancient vs recent) and stand maturity (mature vs overmature), then quantified lichen response to the treatments at the stand (n = 70) and tree scales (n = 420). We distinguished between total macrolichen and Lobarion species alone. Finally, we assessed the influence of tree, standand landscapescale variables, as well as climatic variables. Results: Neither total macrolichen nor Lobarion diversity and composition were influenced by forest continuity, stand maturity or by standor landscapeassociated variables. Instead, climatic variables, light availability at the stand scale and host tree characteristics were the major drivers of lichen assemblages. In our mountain forests, this clearly shows that macrolichen were more influenced by local abiotic and biotic factors than by present or past humaninduced activities. Conclusions: Overall, we show that assemblage patterns in forest ecosystems may be driven by parameters that are not directly related to habitat quality. The influences of forest continuity and stand maturity on diversity and composition thus appear to be contextdependent. In the ecological context of alpine forests, these findings highlight the benefits of selectivecutting practices and illustrate the importance of structural heterogeneity, in terms of both improved accessibility to light and tree diameter diversity. Finally, the importance of temperature in shaping assemblage patterns suggests that global warming is probably the most significant threat to macrolichen conservation in temperate mountain forests.
86011897
An integrated analysis of the effects of past land use on forest herb colonization at the landscape scale
Summary 1 A framework that summarizes the direct and indirect effects of past land use on forest herb recolonization is proposed, and used to analyse the colonization patterns of forest understorey herbaceous species in a 360-ha mixed forest, grassland and arable landscape in the Dijle river valley (central Belgium). 2 Fine-scale distribution maps were constructed for 14 species. The species were mapped in 15 946 forest plots and outside forests (along parcel margins) in 5188 plots. Forest stands varied in age between 1 and more than 224 years. Detailed land-use history data were combined with the species distribution maps to identify species-specific colonization sources and to calculate colonization distances. 3 The six most frequent species were selected for more detailed statistical analysis. 4 Logistic regression models indicated that species frequency in forest parcels was a function of secondary forest age, distance from the nearest colonization source and their interaction. Similar age and distance effects were found within hedgerows. 5 In 199 forest stands, data about soils, canopy structure and the cover of competitive species were collected. The relative importance of habitat quality and spatio-temporal isolation for the colonization of the forest herb species was quantified using structural equation modelling (SEM), within the framework proposed for the effects of past land use. 6 The results of the SEM indicate that, except for the better colonizing species, the measured habitat quality variables are of minor importance in explaining colonization patterns, compared with the combination of secondary forest age and distance from colonization sources. 7 Our results suggest the existence of a two-stage colonization process in which diaspore availability determines the initial pattern, which is affected by environmental sorting at later stages.
28209467
Ecological perspectives for the restoration of plant communities in European temperate forests
Simultaneously with increasing afforestation efforts in western Europe, among conservationists the consciousness is growing that protecting areas to conserve biodiversity will not be sufficient in the long term, and that also the ecological restoration of more or less severely altered areas will be necessary. The probability that recently established forest stands develop towards their ecological reference (i.e. ancient forest) depends largely on the possibility of the target species to colonize them. We focused on the colonization ability of forest plant species and particularly on so-called ancient forest plant species. Major constraints for ecological forest restoration are the spatial characteristics of the target site (isolation, shape and area), imposing dispersal limitations, and in the duration and intensity of the historical land use, leading to changes in habitat characteristics influencing recruitment probability. We reviewed the ecological literature with respect to these constraints and conclude that it takes at least a century to restore the understorey layer of recent forests, even when the target stand is adjacent to a well-developed ancient forest. Both recruitment and dispersal limitation of the target species are responsible for this. Newly established forests should therefore be situated at a minimal distance of the ancient forest source. In other cases, forest plant species will not be able to colonize the newly established forest on a measurable time scale and artificial introduction of forest plant species can be taken into consideration. The negative effects of habitat characteristics, and mainly high soil nutrient values in the recent forest stand can be mitigated by soil nutrient lowering measures. Disturbances in the recent forest should be minimized to maintain a high canopy closure level, preventing light demanding, high competitive species from establishing a stable population. An additional negative consequence of soil disturbances is that it stimulates germination of species from the soil seed bank, which is mainly composed of highly competitive or ruderal species.
84014363
Does forest continuity matter in conservation? : A study of epiphytic lichens and bryophytes in beech forests of southern Sweden
Abstract The effects of forest continuity at local scale for red-listed and indicator species of epiphytic lichens and bryophytes were investigated in 150 Fagus sylvatica stands in southern Sweden. Stands having forest continuity (n = 106) had continuous forest cover more than 350 years, whereas stands lacking continuity (n = 44) had forest cover less than 160 years. Forest continuity was identified by comparing a sequence of historical maps with a modern survey of beech forests. In the field woody beech substrates were searched for the epiphytes of interest. A number of environmental and spatial variables were inventoried and compiled for each stand. In all 64 species (51 lichens, 13 bryophytes) were found in the stands having continuity, and 21 (14 lichens, 7 bryophytes) in the stands lacking continuity. Controlling for the different number of surveyed stands, stands having continuity had significantly more species of lichens, but not of bryophytes. In the stands lacking continuity we did not find lichens associated with the very late succession stage. The quantity of substrates, stand age and forest continuity were the three most important factors explaining species richness as well as composition of studied epiphytes. The effect of continuity was probably due to a combination of a higher substrate quality, mainly old beeches, and a longer time available for colonization. Also, we found strong positive correlations between number of indicator and red-listed epiphyte species. In short-term conservation old stands having continuity, containing suitable substrates and indicator species are target areas.
8926639
Using forest history and spatial patterns to identify potential high conservation value forests in Romania
Naturally dynamic forests have a high proportion of biotopes with old large trees, diverse vertical and horizontal structure at multiple scales, and much dead wood. As such, they provide habitat to species and ecosystem processes that forests managed for wood production cannot provide to the same degree. Whether termed old-growth, ancient, virgin, intact, primeval or continuity forests, a major challenge and need is to map such potential high conservation value forest for subsequent inclusion in functional habitat networks for biodiversity conservation in forest landscapes. Given that the delivery time of natural forest properties is much longer than of industry wood, we explore the usefulness of using historical maps to identify forests that have been continuously present for 220 years (potential old-growth) versus 140 years (potential aging forest) in a case study in the Romanian Carpathian Mountains (see Online Resource 1). While the total forest cover increased by 35 % over the past two centuries, the area of potential aging and potential old-growth forest declined by 56 and 34 %, respectively. Spatial modelling of edge effects and patch size for virtual species with different requirements indicated an even greater decrease in the area of functional habitat networks of old-growth and ageing forest. Our analyses show that compared to simple mapping of potential high conservation forests, the area of functional habitat patches is severely overestimated, and caution is needed when estimating the area of potential high conservation value forests that form functional habitat networks, i.e. a green infrastructure. In addition, the landscape and regional scale connectivity of patches needs to be considered. We argue that the use of historical maps combined with assessment of spatial patterns is an effective tool for identifying and analyzing potential high conservation value forests in a landscape context.
85237790
Lichen epiphyte diversity: A species, community and trait-based review
The forest canopy is fundamentally important in biodiversity conservation and ecosystem function. Cryptogamic epiphytes are dominant tree bole and canopy elements in temperate and boreal forests, though remain neglected by mainstream forest ecology. This review makes ecological information on cryptogamic epiphytes available to a non-specialist audience, to facilitate their integration in forest biodiversity and ecosystem studies more generally. The review focuses specifically on lichen epiphytes, highlighting their diversity and ecosystem role. A principal task is to explore pattern and process in lichen epiphyte diversity – species composition and richness – therefore demonstrating the utility of lichens as an ecological model system. The review examines key themes in previous research. First, the extensive literature used to resolve species response to, and community turnover along environmental/resource gradients, consistent with the habitat niche. Second, the evidence for dispersal-limitation, which may constrain community composition and richness in isolated habitats. Third, these two processes – the habitat niche and dispersal-limitation – are used to explain stand-scale diversity, in addition to the role of neutral effects (habitat area). Fourth, the review moves from a taxonomic (pattern) to a functional (process) perspective, considering evidence for autogenic succession evidenced by competition and/or facilitation, and non-random trends in life-history traits. This functional approach provides a counter-point to an assumption that lichen epiphyte communities are unsaturated and non-competitive, a situation which would allow the long-term accumulation of species richness with temporal continuity. Finally, the review explores landscape-scale impacts on lichen epiphytes, with recommendations for conservation.
43992374
Lichen diversity in temperate montane forests is influenced by forest structure more than climate
Although the effect of forest management on lichens in temperate forests has been widely examined, little is known about the influence of management-related factors on their biodiversity relative to factors that cannot be altered by management. Here we determined whether forest structure or climate determines lichen diversity in the Bavarian Forest National Park in southeastern Germany, taking spatial variables into account. We investigated 517 single tree stems along 4 transects in 113 pre-stratified plots (8 m in diameter) in this montane forest. We grouped environmental variables into three sets: climate (macroclimate, non-manageable), forest structure (manageable), and space. The explanatory powers of these sets of variables for lichen diversity were compared using variance partitioning for the lichen community, species density, and threatened species density. The relationships of single characteristics of forest structure with lichen species diversity were analyzed using generalized linear models (GLM). Lichen diversity was better explained by stand structures than by climate. Spatial effects influenced the number of species per plot. Among the structural features, the availability of dead wood and sycamore maple as well as forest continuity were most important for the enhancement of lichen diversity. Open canopy structures affected the total diversity positively. Although the availability of large trees was not an influential factor in the GLM at the plot level, high diversity levels were generally associated with large stem diameters at the level of single stems. We provide recommendations for sustainable forestmanagement practices that aim at specifically enhancing lichen diversity in temperate areas experiencing low levels of air pollution.
85377322
Effects of forest management on epiphytic lichens in temperate deciduous forests of Europe – A review
Abstract This review aims at summarizing literature on epiphytic lichens in relation with forest management in temperate deciduous forests of Europe, including suggestions for mitigating the impact of forestry and stimulating further research. The review is focused on environmental factors that directly depend on, or that are known to interact with forest management, such as tree (and forest) age and size, tree species composition, large scale factors (e.g. climate and air pollution), landscape context, and past forest history. The literature demonstrates the sensitiveness of epiphytic lichens to forestry: forest management, and especially the shelterwood system, is a source of threat for many forest-dwelling lichens. Several studies include explicit recommendations for mitigating the effect of forestry. The main ones are: (a) selective cutting should be preferred to the shelterwood system; (b) the negative effect of the shelterwood system could be mitigated by the extension of the rotation period and by the retention of groups of mature trees at the final harvest; (c) the creation of stands with intermediate canopy openness should be promoted; (d) logs and snags should be retained in production forests; (e) large old trees should be maintained in production forests and some of them left until dead and decomposed (“eternity trees”); (f) tree species diversity should be maintained in mixed stands; (g) forest fragments around existing species-rich oldgrowth remnants should be maintained, to create a network of set-aside areas; (h) indicator species could be used for a rapid assessment of forest sites worthy of conservation. However, some topics are still scarcely explored, such as the case of (a) coppice forests, (b) the evaluation of the landscape context and forest history, (c) dead wood-dwelling communities and the role of different types of dead wood for lichen conservation, (d) the effects of emerging infectious diseases, and (e) the use of indicator species to assess the conservation importance of forests. Other research approaches, that are still scarcely developed for lichens, may contribute further information for a more comprehensive understanding of the processes that are behind observed patterns of lichen diversity, such in the case of the evaluation of the role of species functional traits in determining the dispersal ability and the response of lichens to environmental factors.
85212869
Effects of forest continuity and tree age on epiphytic lichen biota in coniferous forests in Estonia
Epiphytic lichen biota on Picea abies and Pinus sylvestris in Estonia was studied. Twenty-one spruce and 21 pine sample plots were located in old forests with long forest continuity, and 12 spruce and 12 pine sample plots in young first-generation forests (<100 years). Altogether 103 lichen species were recorded on the 330 sampled trees. Lichen species richness per plot was significantly higher in old forests in case of both tree species; 31 lichen species, including red-listed and protected species, were found only in old forests. Tree age had a positive effect on lichen species richness on tree stem in old and young spruce forests and in young pine forests. Tree age also had an effect on the presence of several species. Both tree age and forest continuity affected lichen species composition. Arthonia leucopellaea, Chrysothrix spp. and Lecanactis abietina were found in at least every third old spruce or pine forest and in no young forests, and can be regarded as good indicators of old coniferous forests with long continuity in Estonia.
83956291
Species occurrences at stand level cannot be understood without considering the landscape context: Cyanolichens on aspen in boreal Sweden
A major challenge in conservation biology is to understand species’ responses to habitat loss. In Fennoscandia, the ongoing decline in aspen in forests is of particular concern, since aspen is the ...
83701374
Cyanobacterial macrolichens on Populus tremula as indicators of forest continuity in Finland
The frequency of cyanobacterial or cephalodial macro-lichens on old standing Populus trees in southern and middle boreal Finland was surveyed on 22 sample plots containing 22–41 trunks. The sample plots were divided into four main groups according to location and human impact: (A) middle boreal ± old-growth, (B) southern boreal old-growth, (C) southern boreal slightly managed and (D) southern boreal strongly managed plots. The number of cyanobacterial lichen species per tree was mainly 0–2 and only rarely exceeded 5 on some large old-growth trees. All cyanobacterial species occurred exclusively or more frequently on the old-growth plots. Thus the occurrence of cyanobacterial lichens proved to be a potential simple indicator of the continuity of the forest stand. The best indicator species were Lobaria pulmonaria, Nephroma spp., Pannaria pezizoides and Parmeliella triptophylla.
86192337
Changing climate and historic-woodland structure interact to control species diversity of the ‘Lobarion’ epiphyte community in Scotland
Abstract Question: How will changing climate and habitat structure interact to control the species diversity of lichen epiphytes? Location: Scotland. Method: Species richness (=diversity) of the epiphyte lichen community known as Lobarion (named after Lobaria pulmonaria) was quantified for 94 Populus tremula stands across Scotland, and compared in a predictive model to seven climate variables and eight measures of woodland structure. An optimum model was selected and used to project Lobarion diversity over the geographic range of the study area, based on IPCC climate change scenarios and hypothetical shifts in woodland structure. Results: Species diversity of the Lobarion community was best explained by three climate variables: (1) average annual temperature; (2) autumn and winter precipitation; in combination with (3) historic-woodland extent. Projections indicate a positive effect of predicted climate change on Lobarion diversity, consistent with the physiological traits of cyanobacterial lichens comprising the Lobarion. However, the general response to climate is modified significantly by the effect on diversity of historic-woodland extent. Conclusions: Historic-woodland extent may exert an important control over local climate, as well as impacting upon the metapopulation dynamics of species in the Lobarion. In particular, a temporal delay in the response of Lobarion species to changed woodland structure is critical to our understanding of future climate change effects. Future Lobarion diversity (e.g. in the 2050s) may depend upon the interaction of contemporary climate (e.g. 2050s climate) and historic habitat structure (e.g. 1950s woodland extent). This is supported by previous observations for an extinction debt amongst lichen epiphytes, but suggests an extension of simple climate-response models is necessary, before their wider application to lichen epiphyte diversity.
91719998
Performance of Macrolichens and Lichen Genera as Indicators of Lichen Species Richness and Composition
In the search for cost-effective methods for measuring and monitoring lichen diversity, we tested the performance of two possible indicators: lichen genus diversity and macrolichen diversity. We studied the lichen vegetation of eight European countries situated in six different biogeographic regions. In each country, six land-use units (each 1 km 2 )r epresenting a land-use gradient ranging from old-growth forest to farmland were sampled (n = 48) for terricolous, saxicolous, and epiphytic lichens at 16 plots each. We found 768 different lichen species belonging to 157 genera. Relationships between richness and density of genera and species, species and macrolichens, and crustose lichens and macrolichens were highly significant (p < 0.001) for all substrates combined and for epiphytic and saxicolous lichens. Richness and density of genera and macrolichens explained a large amount of variation of the species richness and density (R 2 : 71.9%-98.0%). Th er elationship between crustose lichens and macrolichens explained less of the variation (R 2 : 37.7%-70.1%). Effects of land-use intensity on the richness and density of genera, species, and crustose lichens were similar, except for a strong difference between the forested and the more open land-use units for epiphytic crustose lichens. For epiphytic macrolichens there were fewer significant effects. Detrended correspondence analysis indicated similar ordering of sites along the major gradients and similar length of these gradients for genera, species, macrolichens, and crustose lichens. Both genera and macrolichens are useful indicators of total lichen species richness and density. Macrolichens, however, are more suitable indicators than genera owing to (1) their
85627188
Influence of tree species on epiphytic macrolichens in temperate mixed forests of northern Italy
Tree species is a key factor in shaping epiphytic lichen communities. In managed forests, tree species composition is mainly controlled by forest management, with important consequences on lichen diversity. The main aim of this work was to evaluate the differences at tree level in macrolichen richness and composition between Abies alba Mill. and Fagus sylvatica L. in a temperate mixed forest in northern Italy, in addition to evaluating two different proportions of the two species at the stand level. Abies alba and F. sylvatica host lichen communities including several rare and sensitive species. Our findings indicate that both tree species were important for lichen diversity, since they hosted different communities. However, F. sylvatica proved to be a more favourable hosting tree for several rare and sensitive species. Species associated with A. alba were mainly acidophytic lichens, while those associated with F. sylvatica were foliose hygrophytic lichens, mainly establishing over bryophytes. The frequen...
85220496
Occurrence of epiphytic macrolichens in relation to tree species and age in managed boreal forest
For the maintenance of biodiversity some epiphytic macrolichens have been used to identify forests with high conservation value. To understand what these macrolichens indicate, we studied the relationships of tree species and age with the abundance of a set of 33 macrolichens (20 of them in use as indicator species) at 90 localities in a 150 km2 area in south-central Sweden. 
 
 
 
We sampled the four most common tree species Scots pine Pinus sylvestris. Norway spruce Picea abies, birch Betula spp, and aspen Populus tremula for macrolichens at 0-2 m from the base. Of the 33 target species we found 17, six of them were indicators in use for this region. In 30, out of 40 tested, cases there was a positive relation between lichen abundance and age of the tree. 
 
 
 
On all tree species the number of the studied lichen species increased with age. The colonisation rate of the species was fastest on birch. All species occurring on birch were also found on at least one of the coniferous trees, while aspen had six species not found on other trees. Pine and spruce with a slow growth rate had more signal lichen species than fast growing trees. 
 
 
 
We could not detect a competitive situation between common and rare species as the most abundant or largest lichens did not exclude other species. The length of the longest fruticose lichen was positively correlated with the number of species on the tree. Shade had a negative effect on the number of species. 
 
 
 
We conclude that the indicator macrolichens encountered in this study showed a preference for old trees or aspens. This result, and the low number of indicator species, points at the importance of promoting these trees for the preservation of biodiversity in the boreal forest.
37836673
Tree and stand level variables influencing diversity of lichens on temperate broad-leaved trees in boreo-nemoral floodplain forests
Tree and stand level variables affecting the species richness, cover and composition of epiphytic lichens on temperate broad-leaved trees (Fraxinus excelsior, Quercus robur, Tilia cordata, Ulmus glabra, and U. laevis) were analysed in floodplain forest stands in Estonia. The effect of tree species, substrate characteristics, and stand and regional variables were tested by partial canonical correspondence analysis (pCCA) and by general linear mixed models (GLMM). The most pronounced factors affecting the species richness, cover and composition of epiphytic lichens are acidity of tree bark, bryophyte cover and circumference of tree stems. Stand level characteristics have less effects on the species richness of epiphytic lichens, however, lichen cover and composition was influenced by stand age and light availability. The boreo-nemoral floodplain forests represent valuable habitats for epiphytic lichens. As substrate-related factors influence the species diversity of lichens on temperate broad-leaved trees differently, it is important to consider the effect of each tree species in biodiversity and conservation studies of lichens.
204153987
Reprint of: Patterns and drivers of species composition of epiphytic bryophytes and lichens in managed temperate forests
Epiphytic bryophytes and lichens are an important component of the endangered forest biota in temperate forests, their diversity and composition patterns being regulated by tree, stand and landscape scale factors. The aim of this study is to improve ecological understanding of such factors in managed coniferous–deciduous mixed forests of Hungary in the context of forest management. In particular, this study investigate the effect of tree species composition, stand structure (tree size distribution, shrub layer and dead wood), microclimate (light, temperature and air humidity), landscape and historical factors on the stand level and tree level composition of epiphytic bryophytes and lichens. The relationships were explored by multivariate methods (Redundancy Analysis, canonical correspondence analysis and variation partitioning) and indicator species analysis. Tree species is among the most important driver of species composition in both organism groups. For bryophytes, the continuity of forest microclimate and the presence of shrub layer are also important, while lichen assemblages are influenced by light availability. Landscape and historical variables were less influential than stand scale factors. On the basis of our results, the main strategy of management focusing on epiphyte diversity conservation should include: (1) the maintenance of tree species diversity in mixed stands; (2) increasing the proportion of deciduous trees (mainly oaks and hornbeam); (3) the maintenance of large trees within the stands; (4) the presence of shrub and regeneration layer; (5) the creation of heterogeneous light conditions.
84209939
Quantifying the recovery of old-growth attributes in forest reserves: A first reference for France
Abstract Over the past centuries in Western Europe, the long history of forest management has shaped both landscape- and local-scale forest structures. In France, a network of strict forest reserves was created in the 1950s to serve as a reference for nature conservation and forest dynamics. However, few studies to date have quantitatively compared the structural characteristics between managed stands and the reserves, where management has been (more or less recently) abandoned. In addition, the time needed for old-growth characteristics to restore themselves in strict forest reserves remains poorly known. We analysed the differences in stand characteristics between managed and unmanaged stands in 17 French forests (233 plots) located in both lowland and in mountainous regions. We quantitatively showed that overall basal area, very large trees and deadwood features were significantly higher in unmanaged forests, though this pattern was mainly found in the lowland forests while in mountainous regions, managed and unmanaged forests showed far fewer differences. In addition, most structural characteristics that were higher in unmanaged forests also increased with the time since last harvesting. Compared to the remaining old-growth forests elsewhere in Europe, the strict forest reserves in France often appear less mature, since they are still recovering from centuries of intensive management. Our results also show lower levels than those observed in other European studies on the restoration of old-growth characteristics over time; this indicates that it will take French reserves a very long time to reach values comparable to old-growth references in Europe. Our study constitutes one of the first references on unmanaged forests in France and may serve practitioners in their everyday management.
18838834
Are biodiversity patterns of saproxylic beetles shaped by habitat limitation or dispersal limitation? A case study in unfragmented montane forests
Understanding the processes that shape biodiversity patterns is essential for ecosystem management and conservation. Local environmental conditions are often good predictors of species distribution and variations in habitat quality usually positively correlate to species richness. However, beside habitat limitation, species presence-absence may be constrained by dispersal limitation. We tested the relative importance of both limitations on saproxylic beetle diversity, using forest continuity as a surrogate for dispersal limitation and stand maturity as a surrogate for habitat limitation. Forest continuity relies on the maintenance of a forest cover over time, while stand maturity results in the presence of old-growth habitat features. Forty montane beech-fir forests in the French pre-Alps were sampled, under a balanced sampling design in which forest continuity and stand maturity were crossed. A total of 307 saproxylic beetle species were captured using flight-interception traps and Winkler–Berlese extractors. We explored the response of low- versus high-dispersal species groups to forest continuity and stand maturity. Saproxylic beetle diversity increased significantly with stand maturity and was mostly influenced by variables related to deadwood diversity at the stand scale and suitable habitat availability at the landscape scale. Surprisingly, no evidence of dispersal limitation was found, as diversity patterns were not influenced by forest continuity and associated variables, even for low-dispersal species. Our study demonstrates that in an unfragmented forest landscape, saproxylic beetles are able to colonize recent forests, as long as local deadwood resources are sufficiently diversified (e.g. tree species, position, diameter and/or decay stage).
53619636
Effects of competition on tree radial‐growth vary in importance but not in intensity along climatic gradients
Summary 1. Plant interactions play a central role in regulating plant communities and this role can be altered by abiotic stress. With increasing stress, ecological theory predicts that the role of competition decreases whilst that of facilitation increases. Such predictions have been tested with short-term plant removal experiments using two distinct indices evaluating the role of plant interactions: the intensity (absolute impact) and the importance (impact relative to that of other abiotic constraints) of plant interactions. 2. Using data on individual tree radial growth from more than 17 000 forest plots covering the habitat conditions of 16 species in the Alps and the Jura mountains of France, we show that nonmanipulative estimates of plant interactions provide an alternative to this experimental approach. We developed a Bayesian neighbourhood growth competition model to test theoretical predictions about plant–plant interactions with a much larger spatio-temporal scope and set of study species than classically used in experimental studies of plant–plant interactions. 3. Our analyses revealed that competition – measured as neighbours effects on adult tree growth – varies in importance but not in intensity along two major bioclimatic gradients (degree-day sum and water availability). Observed patterns of competition importance differed between shade-tolerant and shade-intolerant tree species. First, the mean importance of competition was found to be much higher for shade-intolerant species. Second, for shade-intolerant species the importance of competition remained high even at low crowding indices (i.e. at a low competitor density), whereas for shade-tolerant species competition only became important at high crowding indices. 4. Synthesis. Our non-manipulative approach to the study of plant–plant interactions allows analysing interactions among many species over large climatic gradients. Our results clearly demonstrate that a quantitative estimation of density dependence effects is key to understanding how plant– plant interactions vary along abiotic gradients. Growth predictions derived from our model can easily be integrated with other results on tree regeneration and mortality in individual-based models to investigate how plant–plant interactions drive tree population and community dynamics under varying climatic conditions.
62229412
Model selection and multimodel inference : a practical information-theoretic approach
The second edition of this book is unique in that it focuses on methods for making formal statistical inference from all the models in an a priori set (Multi-Model Inference). A philosophy is presented for model-based data analysis and a general strategy outlined for the analysis of empirical data. The book invites increased attention on a priori science hypotheses and modeling. Kullback-Leibler Information represents a fundamental quantity in science and is Hirotugu Akaike's basis for model selection. The maximized log-likelihood function can be bias-corrected as an estimator of expected, relative Kullback-Leibler information. This leads to Akaike's Information Criterion (AIC) and various extensions. These methods are relatively simple and easy to use in practice, but based on deep statistical theory. The information theoretic approaches provide a unified and rigorous theory, an extension of likelihood theory, an important application of information theory, and are objective and practical to employ across a very wide class of empirical problems. The book presents several new ways to incorporate model selection uncertainty into parameter estimates and estimates of precision. An array of challenging examples is given to illustrate various technical issues. This is an applied book written primarily for biologists and statisticians wanting to make inferences from multiple models and is suitable as a graduate text or as a reference for professional analysts.
13031504
The coefficient of determination R2 and intra-class correlation coefficient from generalized linear mixed-effects models revisited and expanded
The coefficient of determination R2 quantifies the proportion of variance explained by a statistical model and is an important summary statistic of biological interest. However, estimating R2 for generalized linear mixed models (GLMMs) remains challenging. We have previously introduced a version of R2 that we called for Poisson and binomial GLMMs, but not for other distributional families. Similarly, we earlier discussed how to estimate intra-class correlation coefficients (ICCs) using Poisson and binomial GLMMs. In this paper, we generalize our methods to all other non-Gaussian distributions, in particular to negative binomial and gamma distributions that are commonly used for modelling biological data. While expanding our approach, we highlight two useful concepts for biologists, Jensen's inequality and the delta method, both of which help us in understanding the properties of GLMMs. Jensen's inequality has important implications for biologically meaningful interpretation of GLMMs, whereas the delta method allows a general derivation of variance associated with non-Gaussian distributions. We also discuss some special considerations for binomial GLMMs with binary or proportion data. We illustrate the implementation of our extension by worked examples from the field of ecology and evolution in the R environment. However, our method can be used across disciplines and regardless of statistical environments.
86439866
PERMANOVA, ANOSIM, and the Mantel test in the face of heterogeneous dispersions: What null hypothesis are you testing?
ANOSIM, PERMANOVA, and the Mantel test are all resemblance-based permutation methods widely used in ecology. Here, we report the results of the first simulation study, to our knowledge, specifically designed to examine the effects of heterogeneity of multivariate dispersions on the rejection rates of these tests and on a classical MANOVA test (Pillai's trace). Increasing differences in dispersion among groups were simulated under scenarios of changing sample sizes, correlation structures, error distributions, numbers of variables, and numbers of groups for balanced and unbalanced one-way designs. The power of these tests to detect environmental impacts or natural large-scale biogeographic gradients was also compared empirically under simulations based on parameters derived from real ecological data sets. 
 
Overall, ANOSIM and the Mantel test were very sensitive to heterogeneity in dispersions, with ANOSIM generally being more sensitive than the Mantel test. In contrast, PERMANOVA and Pillai's trace were largely unaffected by heterogeneity for balanced designs. PERMANOVA was also unaffected by differences in correlation structure, unlike Pillai's trace. For unbalanced designs, however, all of the tests were (1) too liberal when the smaller group had greater dispersion and (2) overly conservative when the larger group had greater dispersion, especially ANOSIM and the Mantel test. For simulations based on real ecological data sets, PERMANOVA was generally, but not always, more powerful than the others to detect changes in community structure, and the Mantel test was usually more powerful than ANOSIM. Both the error distributions and the resemblance measure affected results concerning power. 
 
Differences in the underlying construction of these test statistics result in important differences in the nature of the null hypothesis they are testing, their sensitivity to heterogeneity, and their power to detect important changes in ecological communities. For balanced designs, PERMANOVA and PERMDISP can be used to rigorously identify location vs. dispersion effects, respectively, in the space of the chosen resemblance measure. ANOSIM and the Mantel test can be used as more “omnibus” tests, being sensitive to differences in location, dispersion or correlation structure among groups. Unfortunately, none of the tests (PERMANOVA, Mantel, or ANOSIM) behaved reliably for unbalanced designs in the face of heterogeneity.
85876171
CANONICAL ANALYSIS OF PRINCIPAL COORDINATES: A USEFUL METHOD OF CONSTRAINED ORDINATION FOR ECOLOGY
A flexible method is needed for constrained ordination on the basis of any distance or dissimilarity measure, which will display a cloud of multivariate points by reference to a specific a priori hypothesis. We suggest the use of principal coordinate analysis (PCO, metric MDS), followed by either a canonical discriminant analysis (CDA, when the hypothesis concerns groups) or a canonical correlation analysis (CCorA, when the hypothesis concerns relationships with environmental or other variables), to provide a flexible and meaningful constrained ordination of ecological species abundance data. Called “CAP” for “Canonical Analysis of Principal coordinates,” this method will allow a constrained ordination to be done on the basis of any distance or dissimilarity measure. We describe CAP in detail, including how it can uncover patterns that are masked in an unconstrained MDS ordination. Canonical tests using permutations are also given, and we show how the method can be used (1) to place a new observation into...
37490105
Legacies of the past in the present-day forest biodiversity: a review of past land-use effects on forest plant species composition and diversity
Particularly in the temperate climate zone many forests have, at some moment in their history, been used as agriculture land. Forest cover is therefore often not as stable as it might look. How forest plant communities recovered after agriculture was abandoned allows us to explore some universal questions on how dispersal and environment limit plant species abundance and distribution. All studies looking at the effects of historical land use rely on adequate land use reconstruction. A variety of tools from maps, archival studies, and interviews to field evidence and soil analyses contribute to that. They allow us to distinguish ancient from recent forests and many studies found pronounced differences in forest plant species composition between them. A considerable percentage of our forest flora is associated with ancient forests. These ancient forest plant species (AFS) all have a low colonization capacity, suggesting that dispersal in space (distance related) and time (seed bank related) limit their distribution and abundance. However recent forests generally are suitable for the recruitment of AFS. There is clear evidence that dispersal limitation is more important than recruitment limitation in the distribution of AFS. Dispersal in time, through persistent seed banks, does not play a significant role. Ancient forests are not necessary more species-rich than recent forest, but if diversity is limited to typical forest plant species then ancient forests do have the highest number of plant species, making them highly important for nature conservation. The use of molecular markers, integrated approaches and modelling are all part of the way forward in this field of historical ecology.
85843443
Separating forest continuity from tree age effects on plant diversity in the ground and epiphyte vegetation of a Central European mountain spruce forest
Abstract Forest continuity has been identified as an important factor influencing the structure and diversity of forest vegetation. Primary forests with centuries of continuity are usually more diverse than young secondary forests as forest are colonized only slowly and because the former are richer in old tree individuals. In the present study, performed in unmanaged high-elevation spruce forests of the Harz Mountains, Germany, we had the unique opportunity to separate the effects of forest continuity and tree age on plant diversity. We compared an old-growth spruce forest with century-long habitat continuity with an adjacent secondary spruce forest, which had naturally established on a former bog after 1796 when peat exploitation halted. Comparative analysis of the ground and epiphyte vegetation showed that the plant diversity of the old-growth forest was not higher than that of the secondary forest with a similar tree age of >200 years. Our results suggest that a period of >200 years was sufficient for the secondary forest to be colonized by the whole regional species pool of herbaceous and cryptogam forest plants and epiphytes. Therefore, it is likely that habitat structure, including the presence of old and decaying trees, was more important for determining plant diversity than the independent effect of forest continuity. Our results are probably not transferrable to spruce forests younger than 200 years and highly fragmented woodlands with long distances between new stands and old-growth forests that serve as diaspore sources. In addition, our results might be not transferable to remote areas without notable air pollution, as the epiphyte vegetation of the study area was influenced by SO 2 pollution in the second half of the 20th century.
17774928
Factors influencing epiphytic bryophyte and lichen species richness at different spatial scales in managed temperate forests
The effect of management related factors on species richness of epiphytic bryophytes and lichens was studied in managed deciduous-coniferous mixed forests in Western-Hungary. At the stand level, the potential explanatory variables were tree species composition, stand structure, microclimate and light conditions, landscape and historical variables; while at tree level host tree species, tree size and light were studied. Species richness of the two epiphyte groups was positively correlated. Both for lichen and bryophyte plot level richness, the composition and diversity of tree species and the abundance of shrub layer were the most influential positive factors. Besides, for bryophytes the presence of large trees, while for lichens amount and heterogeneity of light were important. Tree level richness was mainly determined by host tree species for both groups. For bryophytes oaks, while for lichens oaks and hornbeam turned out the most favourable hosts. Tree size generally increased tree level species richness, except on pine for bryophytes and on hornbeam for lichens. The key variables for epiphytic diversity of the region were directly influenced by recent forest management; historical and landscape variables were not influential. Forest management oriented to the conservation of epiphytes should focus on: (i) the maintenance of tree species diversity in mixed stands; (ii) increment the proportion of deciduous trees (mainly oaks); (iii) conserving large trees within the stands; (iv) providing the presence of shrub and regeneration layer; (v) creating heterogeneous light conditions. For these purposes tree selection and selective cutting management seem more appropriate than shelterwood system.
84374440
Fragmentation alters beta-diversity patterns of habitat specialists within forest metacommunities
!e relative importance of local, regional and historical factors in controlling the spatial patterns of plant species distribution is still poorly known and challenging for conservation ecology. We conducted an empirical study to link the spatial variation of species and environments among forest patches embedded in contrasted agricultural matrices. We compared how forest herb communities responded to spatial environmental gradients and past forest cover. We found low values of B-diversity in both unfragmented and highly fragmented systems, independently from local and regional diversities. As fragmentation increased, the spatial structure of local plant communities was more complex and spatial e"ects explained an increasing proportion of B-diversity, suggesting that the importance of dispersal limitations increased and played out at broad spatial scales. However, where spatio-temporal isolation of forest patches was the highest, local species assemblages could not be explained, suggesting that the metacommunity functioning was disrupted. Where the historical continuity was high, local environmental characteristics explained a significant amount of species assemblages within metacommunities, suggesting habitat-selection processes. Beta-diversity and variations in presence‐absence of species were also influenced by the intensity of landscape management, via the permeability of both forest edges and the matrix. !is spatially-explicit analysis of metacommunities revealed that forest fragmentation impacts beta-diversity by altering not only the relative importance of deterministic and stochastic processes, but also the spatial scales at which they act. !ese results provide empirical support for the conservation of ancient forests and the maintenance of a high connectedness between fragments within agricultural landscapes.
54657181
Agricultural land abandonment and natural forest re-growth in the Swiss mountains: A spatially explicit economic analysis
Abstract Natural forest re-growth reflects a decline in traditional agricultural practices that can be observed worldwide. Over the last few decades, natural forest re-growth has replaced much of the agricultural land in the Swiss mountains. This is a region where forms of traditional cultivation have preserved unique landscapes and habitats of high ecological value. This study aimed to characterise the locations in the Swiss mountains where agricultural land has been abandoned and overgrown by trees and bushes. Therefore, multivariate statistical models based on geo-physical and socio-economic variables were developed. Land-use change data were taken from two nationwide land-use surveys carried out in the 1980s and 1990s. In order to obtain reliable models, neighbourhood effects and the group structure in our data were accounted for. For the latter a robust estimation technique known as cluster-adjustment was used. Results show that forest re-growth is largely restricted to former alpine pastures, land with grass and scrub vegetation and agricultural land with groups of trees at mid to high altitudes, steep slopes, stony ground and a low temperature sum. Some relationships were not as expected, e.g. many of the new forest areas were found to be relatively close to roads. A new finding from this study was that forest re-growth is largely restricted to regions with immigration, higher proportions of part-time farms as opposed to full-time farms and high farm abandonment rates. By accounting for neighbourhood effects, the model fit was improved. The considerable residual deviance of the models was interpreted as the result of undetected local characteristics, such as poor water availability, small-scaled topographic peculiarities (e.g. small trenches, stonewalls, soil damages by cattle) and the individual's motivation to abandon or maintain cultivation. The conclusion made was that general policy measures for the whole mountain area are not suitable for the prevention of land abandonment and forest re-growth, and that policy measures must pay more attention to local characteristics and needs.
84148829
Growth and morphological response of old-forest lichens transplanted into a young and an old Picea abies forest
This experimental study focuses on why old-forest lichens such as Lobaria scrobiculata and Platismatia norvegica are scarce in younger spruce stands. Understanding the factors limiting the distribution of species is important for developing appropriate methods for forest management aiming to maintain biodiversity. A successful growth of L. scrobiculata and P. norvegica was found in the young planted stand as the rate of growth did not differ between the young stand and the old spruce forest where they naturally occurred, during 14 months of transplantation. In the young forest environment, L. scrobiculata showed a significantly higher specific thallus weight, and a slightly higher water-holding capacity. This morphological response is probably due to a higher light exposure in the young stand and consequently a higher rate of desiccation. The ubiquitous species Platismatia glauca showed a significantly higher rate of growth in the young forest than in the old forest, and a positive relationship between growth rate and light exposure was found. This transplant study has shown that the environmental conditions in younger planted forests are not necessarily unfavourable for growth of old-forest lichens. Other factors, such as limited dispersal ability and poor diaspore production, are probably important for explaining the species scarcity in younger stands.
22438894
Quantifying dispersal and establishment limitation in a population of an epiphytic lichen.
Dispersal is a process critical for the dynamics and persistence of metapopulations, but it is difficult to quantify. It has been suggested that the old-forest lichen Lobaria pulmonaria is limited by insufficient dispersal ability. We analyzed 240 DNA extracts derived from snow samples by a L. pulmonaria-specific real-time PCR (polymerase chain reaction) assay of the ITS (internal transcribed spacer) region allowing for the discrimination among propagules originating from a single, isolated source tree or propagules originating from other locations. Samples that were detected as positives by real-time PCR were additionally genotyped for five L. pulmonaria microsatellite loci. Both molecular approaches demonstrated substantial dispersal from other than local sources. In a landscape approach, we additionally analyzed 240 snow samples with real-time PCR of ITS and detected propagules not only in forests where L. pulmonaria was present, but also in large unforested pasture areas and in forest patches where L. pulmonaria was not found. Monitoring of soredia of L. pulmonaria transplanted to maple bark after two vegetation periods showed high variance in growth among forest stands, but no significant differences among different transplantation treatments. Hence, it is probably not dispersal limitation that hinders colonization in the old-forest lichen L. pulmonaria, but ecological constraints at the stand level that can result in establishment limitation. Our study exemplifies that care has to be taken to adequately separate the effects of dispersal limitation from a limitation of establishment.
13662959
Specific Vicariance of Two Primeval Lowland Forest Lichen Indicators
To date, the lichens Chrysothrix candelaris and Varicellaria hemisphaerica have been classified as accurate primeval lowland forest indicators. Both inhabit particularly valuable remnants of oak-hornbeam forests in Europe, but tend toward a specific kind of vicariance on a local scale. The present study was undertaken to determine habitat factors responsible for this phenomenon and verify the indicative and conservation value of these lichens. The main spatial and climatic parameters that, along with forest structure, potentially affect their distribution patterns and abundance were analysed in four complexes with typical oak-hornbeam stands in NE Poland. Fifty plots of 400 m2 each were chosen for detailed examination of stand structure and epiphytic lichens directly associated with the indicators. The study showed that the localities of the two species barely overlap within the same forest community in a relatively small geographical area. The occurrence of Chrysothrix candelaris depends basically only on microhabitat space provided by old oaks and its role as an indicator of the ecological continuity of habitat is limited. Varicellaria hemisphaerica is not tree specific but a sufficiently high moisture of habitat is essential for the species and it requires forests with high proportion of deciduous trees in a wide landscape scale. Local landscape-level habitat continuity is more important for this species than the current age of forest stand. Regardless of the indicative value, localities of both lichens within oak-hornbeam forests deserve the special protection status since they form unique assemblages of exclusive epiphytes, including those with high conservation value.
83665607
Tree age is a key factor for the conservation of epiphytic lichens and bryophytes in beech forests.
Questions: What factors limit the distribution of epiphytic lichens and bryophytes at plot and tree level in beech forests? At what ages do epiphytic species, and species of conservation concern in particular, occur along a chronosequence of beech? 
 
Location: South-west Sweden. 
 
Method: Five hundred and seventy-one age-determined trees from 37 plots distributed among 29 beech-dominated stands were surveyed along with a number of environmental (16) and substrate (seven) variables in a landscape of ca. 550 ha. Non-metric multidimensional scaling (NMS) and indicator species analysis (ISA) were used for data analysis. 
 
Results: Plots containing old trees, confined to the base of slopes and with low impacts of recent forestry (thinning), generally had a high richness of species of conservation concern. Richness of common species and red-listed bryophytes were mostly related to the surveyed bark area. At tree level, primary factors explaining both species richness and composition were age, diameter at breast height and moss cover. There was a gradual replacement of tree age ranges for 58 lichens and 37 bryophytes along the chronosequence of beech. Red-listed lichens favoured damaged beech trees (≥180 years), whereas red-listed bryophytes were found on old and young stems in dense stands. 
 
Conclusions: Tree age exerts a profound influence on epiphytic lichens and bryophytes growing on beech. Many of the habitat specialists were found mainly on old beech because they inhabit specific substrates that occur on older trees. The association to high tree age commonly excludes red-listed lichens from conventionally managed beech forests with a 100- to 140-year rotation period.
53519951
The influence of tree age and microhabitat quality on the occurrence of crustose lichens associated with old oaks
Abstract Questions: How do tree age, microhabitat characteristics and epiphytic competitors affect the occurrence of crustose lichens associated with old oaks? How do microhabitat characteristics and microclimate affect the cover of competitors (bryophytes and macrolichens)? How do microhabitat characteristics correlate with microclimatic variables? Location: Southeast Sweden. Methods: Eight crustose lichen species were surveyed on 165 Quercus robur trees, 17–478 years old, at three study sites. The occurrence patterns of these species were examined at two spatial scales: among trees and within trees. Occurrence patterns within trees were examined in 10 cm × 10 cm plots at all four cardinal aspects at different heights from 0.5 to 4.5 m above the ground. Results: At the tree level, age-related factors were the most important predictors of species occurrence. All species were more frequent on trees > 100 years than on younger trees. At the plot level, the frequency of occurrence increased with increasing bark crevice depth. The frequencies of all study species decreased with increasing cover of bryophytes. Bryophytes were in turn more frequent in plots that were exposed to rainwater and showed a low evaporation rate. Patches most exposed to rainwater were directed upwards, and the lowest evaporation rates occurred on the northern side of the trunks. Conclusions: For many crustose lichens the association with old oak trees seems at least partly to depend on their preference for the deep bark crevices that only occur on old trees. Trees represent epiphyte habitat patches that differ in size due to within-tree variability in habitat quality, such as bark crevice depth and microclimate. This study shows that variability at a finer scale, within habitat patches, contribute to explain species occurrence patterns at habitat patch level. Nomenclature: Santesson et al. (2004).
17333120
Topographic and forest-stand variables determining epiphytic lichen diversity in the primeval beech forest in the Ukrainian Carpathians
Abstract
The Uholka-Shyrokyi Luh area of the Carpathian Biosphere Reserve is considered the largest and the most valuable primeval beech forest in Europe for biodiversity conservation. To study the impact of different topographic and forest-stand variables on epiphytic lichen diversity a total of 294 systematically distributed sampling plots were surveyed and 198 epiphytic lichen species recorded in this forest landscape, which has an uneven-aged structure. The obtained data were analysed using a non-metric multidimensional ordination and a generalized linear model. The epiphytic lichen species density at the plot level was mainly influenced by altitude and forest-stand variables. These variables are related to both the light availability i.e. canopy closure, and the habitat diversity, i.e. the developmental stage of the forest stands and the mean stem diameter. We found that lichen species density on plots with a relatively open canopy was significantly higher than on plots with a fairly loose or closed canopy structure. The late developmental stage of forest stands, which is characterized by a large number of old trees with rough and creviced bark, had a strong positive effect on lichen species density. In the Uholka-Shyrokyi Luh primeval forest the mean stem diameter of beech trees significantly correlated with lichen species density per plot. Similar trends in the species diversity of nationally red-listed lichens were revealed. Epiphytic lichens with a high conservation value nationally and internationally were found to be rather abundant in the Uholka-Shyrokyi Luh area, which shows its international importance for the conservation of forest-bound lichens.
83541717
Influence of forest management on epiphytic lichens in a temperate beech forest of northern Italy
The influence of forest management on species richness and composition of epiphytic macrolichens was studied on beech stems in two differently managed stands in northern Italy: (1) mixed-multilayered stand with silver fir, spruce and beech, managed by selective-cutting and (2) pure beech stand, intensively managed by shelterwood-cutting. Macrolichens and easily identifiable crustose lichens were surveyed on 150 randomly selected beech trees in 10 management units. Trees of the two stands significantly differed in lichen composition, but not in species richness. However, most of the rare species were exclusive of the sites managed by selective-cutting. The lichen flora of mixed stands mainly included suboceanic species-sensitive to forest management and habitat modification; that of pure stands was dominated by generalist species common in disturbed habitats. Lobaria pulmonaria is suggested as a signal species for rapidly assessing the conservation importance of forests. Some practical suggestions are given to enhance lichen conservation in intensively managed stands.
85352468
Contrasting responses of epiphytic and dead wood-dwelling lichen diversity to forest management abandonment in silver fir mature woodlands
Abstract In the Alps, many forests are under abandonment because of direct protection or the unprofitability of timber production. The objective of this study was to analyse the effect of silviculture abandonment on the species richness and composition of epiphytic and dead wood-dwelling lichens in silver fir woodlands. An abandoned and a currently non-intensively managed forest watershed of the eastern Italian Alps that were matched for topography, stand structure, plant community and history of use were selected and randomly sampled for the lichen diversity of their silver fir mature stands. Generalised linear mixed models were used for the analyses of the species richness, whereas the species composition patterns were explored by redundancy analysis. The diversity of both of the lichen guilds were explained by the microhabitat conditions related to the contrasting management regimes, but they had opposite responses to the abandonment of the silvicultural activities. The epiphytic lichen communities were richer in species in the managed than in the abandoned silver fir woodlands. However, the effect of a 50 year management cessation on the epiphytic lichens may change in the long term when natural disturbances create gaps and increase the attributes of old-growth forests. The dead wood-dwelling lichen species richness was higher in the abandoned forest because an increased availability of types of dead wood is usually rare in managed forests. The dead wood-dwelling lichen communities of the managed forests were a subset of a more diverse community that was developing in the abandoned forest. Our results indicated that, in non-intensively managed silver fir mature stands, lichen diversity may benefit from the retention of logs and snags, which provide habitat features typical of old-growth forests.
86691640
Retention Forestry to Maintain Multifunctional Forests: A World Perspective
The majority of the world's forests are used for multiple purposes, which often include the potentially conflicting goals of timber production and biodiversity conservation. A scientifically validated management approach that can reduce such conflicts is retention forestry, an approach modeled on natural processes, which emerged in the last 25 years as an alternative to clearcutting. A portion of the original stand is left unlogged to maintain the continuity of structural and compositional diversity. We detail retention forestry's ecological role, review its current practices, and summarize the large research base on the subject. Retention forestry is applicable to all forest biomes, complements conservation in reserves, and represents bottom-up conservation through forest manager involvement. A research challenge is to identify thresholds for retention amounts to achieve desired outcomes. We define key issues for future development and link retention forestry with land-zoning allocation at various scales, expanding its uses to forest restoration and the management of uneven—age forests.
85993977
Contrasting patterns of lichen functional diversity and species richness across an elevation gradient
Major environmental gradients co-vary with elevation and have been a longstanding natural tool allowing ecologists to study global diversity patterns at smaller scales, and to make predictions about the consequences of climate change. These analyses have traditionally studied taxonomic diversity, but new functional diversity approaches may provide a deeper understanding of the ecological mechanisms driving species assembly. We examined lichen taxonomic and functional diversity patterns on 195 plots (200 m²) together with forest structure along an elevational gradient of 1000 m in a temperate low mountain range (Bohemian Forest, Germany). Along this elevation gradient temperature decreased and precipitation increased, two macroclimatic variables critical for lichens. Elevation was more important than forest structure in driving taxonomic and functional diversity. While species richness increased with elevation, functional diversity decreased and revealed that community patterns shift with elevation from random to clustered, reflecting selection for key shared traits. Higher elevations favored species with a complex growth form (which takes advantage of high moisture) and asexual reproductive mode (facilitating establishment under low temperature conditions). Our analysis highlights the need to examine alternative forms of diversity and opens the avenue for community predictions about climate change. For a regional scenario with increasing temperature and decreasing availability of moisture, we expect a loss of specialized species with a complex growth form and those with vegetative organs at higher elevations in low mountain ranges in Europe.
84733631
Epiphytic lichen diversity along elevational gradients: biological traits reveal a complex response to water and energy
Aim 
Patterns of epiphytic lichen diversity along elevational gradients covering the range of Norway spruce forests were analysed. The roles of water and energy variables in shaping the observed species–elevation relationship were tested, as well as how growth form and photobiont type distribution varied along the gradient. 
 
Location 
South Tyrol, northern Italy. 
 
Methods 
Eight sites were selected spanning the elevational range of spruce forests (900–1900 m a.s.l.) and the regional rainfall gradient. At each site, a pair of forest stands (one mature even-aged and one multilayered) was selected at three elevation steps. Epiphytic lichens were surveyed according to European guidelines for lichen diversity monitoring. Explanatory variables indicative of both forest structure and climate were included in the models. 
 
Results 
A positive relationship was found between number of species and elevation. This reflected the physiological response of epiphytic lichens to the main climatic factors, trait selection being the mechanism that determined the response at community level. Nonlinear species–temperature and trait–temperature relationships predicted that major changes may be expected in the intermediate part of the gradient. Lichens with a Trentepohlia algal partner were more frequent at lower elevations and proved to be sensitive to environmental factors indicative of forest structure. Lichen growth forms had contrasting patterns related to temperature, crustose species richness being enhanced by increasing values, and alectorioid and foliose lichens by decreasing values. Alectorioid lichens were also negatively influenced by rainfall. 
 
Main conclusions 
In a climate change scenario, lichen diversity in alpine regions will probably not benefit from an increase in air temperature in the same way as flowering plants. Monitoring variations in the proportions of growth form and photobiont type may represent a tool for detecting the effects of climate change on lichen species.
84191816
The importance of macrolichen traits and phylogeny in forest community assemblage along a high elevation gradient in southwestern British Columbia
Abstract Macrolichen community structure and traits were examined across a high elevation gradient in southwestern British Columbia. To our knowledge, the current study is the first to examine lichen phylogeny and community traits along a gradient of elevation. Samples were collected from 13 plots, every 50 m from 1200 to 1800 m at Joffre Lakes Provincial Park. Species richness within this zone had a unimodel distribution from low to high elevation and peaked at an intermediate elevation. Canonical correspondence analysis (CCA) confirmed that a distinct lichen community structure and assemblage of lichens is represented across the gradient of elevation. The covariate for lichen phylogeny explained 9% of the variation in community assemblage along the gradient of elevation. Lichen traits explained 91% of the variation in community assemblage. The first CCA axis distinguishes between alpine and forest lichen communities, and identified important microhabitats and traits used to explain variation in the species associations. The second CCA axis makes a distinction between higher and lower elevations and is strongly correlated with variables such as the presence of specific microhabitats (i.e. rock, wood, or bark), and lichen traits. Within the elevation range assessed, the analysis indicated three distinct lichen communities, one in alpine ecosystems, one in higher elevations forests and one in mid elevation forests. These results provide forest managers with an increased understanding of lichen community structure across elevation gradients and of indicator species and their associated traits, which can assist with management strategies that include the preservation of biodiversity.
13012608
Environmental optimality, not heterogeneity, drives regional and local species richness in lichen epiphytes
Aim 
 
We evaluate the scale dependence of species richness–environment relationships with a continent-wide analysis of lichen epiphyte communities. Specifically, our goals are to assess: (1) the dependence of local richness on regional processes, (2) whether species richness is primarily influenced by heterogeneity in environmental conditions or the central tendency of those conditions, and (3) whether the relative influence of these different aspects of the environment differs between local communities and regional species pools. 
 
 
 
Location 
 
Forests of the contiguous United States. 
 
 
 
Methods 
 
We used variation partitioning and model averaging of linear models to relate macrolichen richness at 1923 forest inventory plots (c. 4000 m2) to measures of environmental heterogeneity and mean conditions at local and regional scales. Data included 17 local environmental variables and 11 regional-scale variables which were obtained from a national forest inventory, herbarium records and several climate data sources. 
 
 
 
Results 
 
Regional-scale variables explained more unique variation in local species richness and generally had stronger effects than variables measured locally. However, most variation in local richness was explained jointly by local and regional variables. At both local and regional scales, variables measuring environmental heterogeneity explained little variation in species richness and had weaker effects than variables characterizing mean environmental conditions. 
 
 
 
Main conclusions 
 
Species richness of epiphytic macrolichens is not regulated by environmental heterogeneity locally or regionally and instead tracks large-scale climate gradients of water availability and temperature. Richness in local communities is influenced by processes operating at both regional and local scales, highlighting the importance of determining large-scale drivers of lichen richness across the North American continent. This research demonstrates a general method for comparing the influence of different aspects of the environment on species richness across scales and should be applicable to many different taxonomic groups.
29479996
Large-scale patterns of epiphytic lichen species richness: photobiont-dependent response to climate and forest structure.
Lichens are composite organisms consisting of a symbiotic association of a fungus with a photosynthetic partner. Although the photobiont type is a key life-history trait, tests of the potential differential role of the main photobiont types in shaping large-scale patterns of lichen species richness are still absent. The aim of the study was to test the influences of forest structure and climate on epiphytic lichen species richness across Italy and to see whether these relationships change for groups of species sharing different photobiont types. Regional species richness of epiphytic lichens divided into three main photobiont types (i.e. chlorococcoid green algae, cyanobacteria, and Trentepohlia algae) was retrieved for each of the 20 administrative regions. Multiple linear regression was used to quantify the effect of climate and forest structure, and their potential interaction, on the regional species richness for the three photobiont types, accounting also for the effect of regional area. Regional species richness was associated with both climate and forest structure variables but the relationships with both factors were largely photobiont dependent. Regional area and precipitation were the only predictors included in all the models, confirming the strong dependence of lichens on atmospheric water supply, irrespective of the photobiont type. Number of species with chlorococcoid green algae were further positively associated with cover of high forest, whilst lichens with Trentepohlia were further enhanced by warm temperatures. Cyanolichen species richness was only related to area and precipitation. Our study shed light on the relative importance of climate and forest structure on lichen species richness patterns at the macroscale, showing a differential response of the photobiont types to various environmental determinants. This differential response suggested that the current and future impacts of global change on lichens cannot be generalized and that species richness response will be likely dependent on the photobiont type.
84058470
Does time or habitat make old-growth forests species rich? Bryophyte richness in boreal Picea mariana forests
The relative importance of time since disturbance and habitat variables in creating diversity in old-growth forests will influence conservation strategies. However, the independent roles of these factors are not well understood, as they are rarely examined independently. This study examines the respective roles of habitat variables and time (stand age) in determining bryophyte diversity in Picea mariana (Mill. (BSP)) forests. Bryophytes are frequently used as indicators of old-growth forest, but their true dependence on forest continuity is unknown. Bryophytes were classified into taxonomic-habitat guilds: true mosses (forest), forest liverworts, bog liverworts and sphagna (bog). Diversity increased with age and peaked at approximately 275 years since fire, driven by liverworts. Multiplicative habitat modeling indicated that time and habitat played different roles for the different taxonomic-habitat guilds. True mosses and forest liverworts were primarily influenced by habitat variables, while sphagna and bog liverworts were influenced by time and habitat variables. The models for sphagna were particularly strong, indicating that many important factors were included, while forest liverwort models were particularly weak. This unexplained variability may represent site specific random factors, such as secondary disturbances that create habitat in a fully occupied space. Overall, high richness was created by small species dependent on habitat variables and chance factors for establishment. Therefore, time since disturbance was not the primary factor limiting richness in these forests. These results suggest that in boreal North America, where forest fragmentation is limited and recent, conservation strategies that emphasize habitat variables rather than forest continuity may be effective for some bryophytes.
6193843
Conceptual problems of Ecological Continuity and its bioindicators
Very old, undisturbed forest stands may be important for biodiversity through their content of microhabitats or for the long periods available for colonisation, or for both. The term Ecological Continuity (EC) has been used to ascribe value to old forest stands. The relative importance of microhabitat and time for colonisation are usually not kept apart when EC is used as a conservation criterium. EC is broadly applied but poorly defined. Use of EC may lead to underestimation of the importance of forest dynamics and dispersal, and to overestimation of the importance of local land use history. If bioindicators of long-term habitat persistence are to be used, species with low dispersal capacity should be chosen. However, many lichens and other fungi, bryophytes and insects cited as indicators of EC, seem to have a patch-tracking lifestyle. They are 'colonists' according to life history strategy classification, and rather seem to indicate specific microhabitats. Terrestrial molluscs, some vascular forest plants, and those bryophytes and lichenized fungi classified as 'perennial stayers' in life history strategy classification, might be used to indicate long-term habitat persistence in forests, but more research is needed to evaluate such indicators.
89183150
Climate change fosters the decline of epiphytic Lobaria species in Italy
Similarly to other Mediterranean regions, Italy is expected to experience dramatic climatic changes in the coming decades. Do to their poikilohydric nature, lichens are among the most sensitive organisms to climate change and species requiring temperate-humid conditions may rapidly decline in Italy, such in the case of the epiphytic Lobaria species that are confined to humid forests. Our study, based on ecological niche modelling of occurrence data of three Lobaria species, revealed that in the next decades climate change will impact their distribution range across Italy, predicting a steep gradient of increasing range loss across time slices. Lobaria species are therefore facing a high extinction risk associated with reduction of their range. The current patterns indicate that only L. pulmonaria still has a continuous distribution across Italy, with potential contact between Apennine and Alpine populations. This situation is consistent with the wider climatic niche of this species, still offering a major opportunity for its successful long-term conservation. Results (a) support the inclusion of the three Lobaria species in European conservation policies, such as the Habitat Directive, and (b) warn against an over-estimation of the indicator power of single flagship species to establish conservation priorities for lichens, indicating that even lichens with peculiar and similar climatic envelopes may fail to co-occur within a given forest stand. A multiple indicator approach could provide more useful tools for a community-based conservation strategy for epiphytes.