Lichens — the biodiversity value of western woodlands

Summary

The Atlantic broad-leaved woodlands of Britain are of international renown for their lichen floras. They are inhabited by 517 lichens, representing 28.3% of the total lichen flora and 73.2% of all British woodland lichens, and they are the main habitat for 165 species. Of these, 31 have a marked southern distribution and do not reach Scotland, whereas 26 species are found in Scotland, but not England or Wales. Their British Red-listed species are outnumbered by the 86 species for which Britain has International Responsibility.

Within the Atlantic broad-leaved woodlands, only 30 lichens show a preponderance for oak. With the exception of some ancient oakwoods in southern England, a high lichen biodiversity is rarely dependent on a dominance of oak in the woodland canopy, more usually it is the result of a long ecological continuity, often a varied tree and shrub composition, a varied canopy density, and good air quality. Consequently, the oak stands within former ‘industrial’ woodlands have a much lower lichen biodiversity compared with woodlands that have a history as ‘pasture woodland’ or, as with some ravine woodlands, have otherwise escaped intensive management.

The life-history of an oak tree is considered in relation to the niches it provides for lichen colonisation with time. Some management scenarios are provided with the enhancement of the lichen interest of former ‘industrial’ oakwoods as an objective.     

Changing climate and historic‐woodland structure interact to control species diversity of the ‘Lobarion’ epiphyte community in Scotland

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 cyanobac‐terial 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.     

Ecological changes in the Loch Lomond region

Summary

The Lichen flora of Rhum is described with emphasis on its ecology. In general, the 387 species represent a fine example of eu-oceanic assemblages and contain many taxa typical of western Britain. The margins of freshwater lochs hold particularly rich communities; the flora of the serpentine is singular for its narrow range of species. There is some evidence that existing fragments of woodland have continuity with the ancient forest. Lecanactis plocina is reported new to Scotland.     

Biodiversity and ecology of the invertebrates of Atlantic Oakwoods

Summary

Woodland in general supports the richest invertebrate fauna of any habitat in Britain. The number of species depends on the structure of the wood and the age of the trees within it. The greatest biodiversity is associated with oaks although the difference between the communities found on the two oak species is not clearly understood, the Sessile Oak woods have been less well studied than their lowland equivalents, particularly so in Scotland. A number of minor habitats within the wood are important for many invertebrates and the presence of many of these may be due to past management. Every part of the oak tree, the leaves, flowers, acorns, bark and wood, supports invertebrates, herbivores, predators and parasites, and the fallen leaves and deadwood provides habitat for a complex of detritus feeders. Within the woodland the other trees, the fungi and the ground flora all have characteristic woodland invertebrates. Only a few studies, on beetles and spiders, have looked at which invertebrates are particularly associated with acidic oakwoods and there have been no specific studies of Atlantic oakwoods. It is known that there are some rare and local invertebrate species associated with western woods on ancient sites, including some recently discovered suggesting that the biodiversity of these sites and their management for invertebrates might be more important than currently thought.     

The impacts of beavers Castor spp. on biodiversity and the ecological basis for their reintroduction to Scotland,UK

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Local extent of old-growth woodland modifies epiphyte response to climate change

Aim To quantify the interaction between climate and woodland continuity in determining the bioclimatic response of lichen epiphytes. Location Northern Britain (Scotland). Methods Indicator‐species analysis was used to pre‐select lichen epiphytes along parallel gradients in climate and the extent of old‐growth woodland. Nonparametric multiplicative regression was used to describe in a predictive model the individualistic response of selected species, which were projected based on climate‐change scenarios and contrasting patterns of simulated woodland loss or gain. Species with a similar response were grouped using a novel application of cluster analysis to summarize the potentially huge number of projected outcomes. Projected patterns of occurrence under climate‐change scenarios were examined for different levels of old‐growth woodland extent. Results Forty‐two lichen species were statistically significant indicator species in oceanic woodlands, and old‐growth indicators under suboptimal climatic conditions. Responses to climate‐change scenarios were contrasting, with one group comprising species projected to increase in extent in response to climate warming, and other response groups projected to decrease in occurrence, possibly in response to shifting rainfall patterns. The occurrence of all response groups had a positive relationship with old‐growth woodland extent. Main conclusions An ‘oceanic’ biogeographical group of epiphytes identified using the baseline climatic and present‐day woodland setting comprised species with a cyanobacterial photobiont or tropical phytogeographical affinities. However, within this group the individual species responses to climate‐change scenarios were contrasting. Additionally, group responses may be poorly matched with simple ecological traits. However, the studied interaction between climate and habitat continuity suggests that the impact of climate change might be offset for certain lichen epiphytes by appropriate management of woodland resources, for example, expansion of native woodland around remnant old‐growth stands.     

Climate,landscape, habitat,and woodland management associations with hazel dormouse Muscardinus avellanarius population status

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A forest habitat network for the Atlantic Oakwoods in Highland region,Scotland

Summary

The need to conserve biological diversity and ensure the future viability and integrity of Atlantic oakwoods in a fragmented landscape has led to strategies that facilitate a more holistic view of biodiversity conservation across extensive areas. The Scottish Forestry Strategy contains a major aspiration to develop forest habitat networks through the restoration and improvement of existing woodland and the expansion of new woodland. The Forest Research landscape ecology model BEETLE (Biological and Environmental Evaluation Tools for Landscape Ecology) uses a focal species approach to assess the functional connectivity of habitat within the wider landscape matrix. This model has been used to predict the current habitat network for Atlantic oakwood specialists in the Highland region of Scotland. The analysis outputs are presented with an approach to help practitioners and planners visualise the opportunities to target expansion, conversion or restoration of Atlantic oakwoods and their intrinsic biodiversity.     

Contrasting functional traits maintain lichen epiphyte diversity in response to climate and autogenic succession

Aim Lichen epiphytes are important for biodiversity conservation and are also widely applied as environmental indicators. However, biogeographical and ecological knowledge underpinning lichen epiphyte conservation, and the use of lichens as indicators, is based primarily on a limited range of ‘macrolichen’ species. Wider trends in epiphyte biodiversity remain largely unexplored. This paper examines the community structure of lichen epiphytes on aspen (Populus tremula L.) in Scotland, including species across all functional groups and comprising, therefore, taxonomically difficult ‘microlichens’. Location Northern Britain (Scotland). Methods Epiphytes were sampled from 12 sites throughout Scotland and examined at two scales: between and within aspen stands. Species were classified into contrasting functional groups and ordination by detrended correspondence analysis was used to summarize community structure. Results Within aspen stands (between trees) epiphyte communities showed successional patterns related to tree age. These successional patterns changed predictably for stands aligned along a climatic gradient (between stands). Main conclusions A dual climatic–successional trend in epiphyte community structure is presented. Large‐scale trends in epiphyte diversity are explained as the local response of species with contrasting functional traits to climate and autogenic succession. Turnover of functional groups between stands is positively related to β‐diversity, and ecological limits to the frequency of contrasting functional groups are presented. Accordingly, the study and application of lichen species with similar functional traits may inadequately represent patterns of biodiversity. This prompts criticism of the currently accepted conservation strategy, i.e. (1) an emphasis in the conservation literature on ‘macrolichen’ species with similar ecologies and (2) the application of lichen indices over climatically variable geographical areas.     

Psammophytic woodlands of the steppe zone in Inner Mongolia

Originated from various vegetation types, psammophytic woodlands on sandy dunes of the steppe zone in Inner Mongolia are rather diverse. The commonest types are woodlands with Pinus sylvestris var. mongolica, P. tabulaeformis, Picea meyeri, Juniperus rigida, Populus davidiana, and Betula platyphylla. In Daqinggou of Horqin sandy land, a mixed broad-leaved woodland consists of Quercus, Acer, Fraxinus, Juglans, Chosenia, Populus, and Ulmus. Palaeoecological evidence demonstrates that these woodland stands are Middle Holocene remnants. The plant communities of psammophytic woodlands are simplified in floristic composition and structure. The relict woodland stands play an important role in the conservation and restoration of vegetation in Inner Mongolia. Only three nature reserves of relict woodland types in Inner Mongolia have been established. Based on this study, an additional reserve is suggested to conserve the complex of psammophytic woodlands.     

19th century woodland structure controls stand-scale epiphyte diversity in present-day Scotland

Axioms developed from island biogeography theory (i.e. species–area relationships, effects of fragmentation and isolation) are central to the development of conservation strategy. Within this context, the 'extinction debt' hypothesis brings into question an often assumed relationship between species richness and present-day spatial habitat structure (i.e. extent, fragmentation), suggesting instead that the richness and composition of biological communities may lag behind spatial changes in habitat. We examined evidence for an extinction debt among epiphytic lichens, a highly diverse biological group of significant conservation concern. Using sites in Scotland, we compared epiphyte species richness in smaller-scale habitat units (aspen stands) to larger-scale woodland structure (extent and fragmentation) measured at two spatial scales (1 km² and 4 km²) and for two timeframes, modern (1990s to 2000s) and historic (1860s to 1880s). Species richness was positively related to woodland extent and negatively related to woodland fragmentation; however, richness was explained better by historic woodland structure at a 1-km² scale, than by modern woodland structure. The results indicate: (1) a coupling of stand-scale epiphyte assembly and dynamics of the wider woodland ecosystem, and (2) a significant lag in the response of epiphyte species richness to habitat spatial structure. However, the effect of spatial habitat structure is different between species groups with contrasting traits. The effect of decreasing woodland extent on epiphyte richness is generally more severe for microlichens (comprising a greater number of rare and specialist species) than the more generalist macrolichens.     

Atlantic oakwoods in Great Britain: Factors influencing their definition,distribution and occurrence

Summary

Atlantic oakwoods are the oceanic oak-dominated woodlands that fringe the western coast of Britain and Ireland and, due to their high humidity and rich and luxuriant lower plant assemblages, have been regarded as ‘temperate rainforest’. However, unlike the similarly iconic Caledonian pinewoods, Atlantic oakwoods have no formal designation or associated woodland classification type, which gives some uncertainty to the extent of the oakwoods habitat on its fringes. This paper examines the various elements central to the concept of an ‘Atlantic oakwood’ and discuses their occurrence in Great Britain.     

山西稀有濒危植物脱皮榆的生态学特征

在总结相关文献资料的基础上 ,通过对山西南部中条山和霍山脱皮榆 (UlmuslamelloseT .WangetS .L .Chang)种群的样地调查 ,分析了脱皮榆的分布规律、生境特点、群落特征和种群结构以及其濒危现状及致濒原因 ,并提出了相应的保护对策。结果表明 :1)脱皮榆群落具有暖温带地带性植被的特点 ,区系成分具有北温带性质。 2 )种群结构具有严重的年龄缺失。 3)山西南部是脱皮榆的分布中心。 4 )致濒的原因是环境破坏和自身繁殖能力下降。     

The potential contribution of conifer plantations to the UK Biodiversity Action Plan

Summary

The detrimental effects of conifer plantations on open ground habitats have been well catalogued and discussed, but the potential contribution of planted forests to the conservation of woodland biodiversity has not been quantified to the same extent. This quantification is needed urgently to help forest managers fulfil commitments to biodiversity enhancement as outlined in the UK Biodiversity Action Plan, the UK Forestry Standard and the UK Woodland Assurance Scheme (UKWAS). Results are presented from a five-year programme of research aimed at obtaining baseline information on biodiversity in planted forests and evaluating the contribution of planted forests to the conservation of native flora and fauna. Fifty-two plots were surveyed in total, covering a range of different tree crops (Scots pine Pinus sylvestris L., Sitka spruce Picea sitchensis (Bong.) Carr., Norway spruce Picea abies L. and Corsican pine Pinus nigra var maritima (Aitón) Melville) and stand ages (pre-thicket, mid-rotation, mature and over-mature) in three contrasting bioclimatic zones (upland, foothills and lowlands) throughout Britain. Additional plots were established in semi-natural woodland to allow comparisons between the biodiversity of plantations and native stands. Over 2000 species were recorded in total, including 45 Red Data Book species. Planted stands had similar or richer fungal and invertebrate communities to those of the native stands but poorer lichen and vascular plant communities. The latter were strongly affected by shading, dense, mid-rotation Sitka spruce stands having the lowest species counts. In contrast, these stands had a high diversity of mycorrhizal fungi, including a number of rare and threatened species normally associated with native pine wood. Bryophyte species-richness was related more to climate than woodland type, with the wetter upland spruce and native oak stands having the most diverse communities. Compared to the younger planted stands, over-mature planted stands had a higher proportion of species characteristic of semi-natural woodland stands. This related to greater structural diversity and higher deadwood volumes in the over-mature stands. It is concluded that conifer plantations make a positive contribution to biodiversity conservation in the UK and hence to the UK Biodiversity Action Plan. No single stand or crop type provides ‘optimal’ conditions for biodiversity, but the habitat value of plantations could be enhanced by increasing the area managed under alternative systems to clear-felling, such as ‘continuous cover’ and/or non-intervention natural reserves.     

Winter bird communities in forest plantations in western England and their response to vegetation,growth stage and grazing

This paper presents the results of a study of wintering bird communities across a wide range of coniferous, broadleaved and mixed forest stands in the Forest of Dean, western England. Bird communities of broadleaved and coniferous woodland differed with respect to their species composition. The mean number of individual birds recorded increased linearly with woodland age and was not influenced by woodland type, stand size or the presence of grazing. Woodland age and type and the presence or absence of grazing all significantly influenced bird species richness and the proportions of the bird community made up by granivores, insectivores and omnivores. Broadleaved stands held more species than coniferous stands. Ungrazed stands held significantly more species, particularly seed-eating species, than grazed stands and this effect was independent of woodland type. Ordination was used to relate variation in tree species composition and stand structure to bird community composition. A larger number of species was associated with broadleaved stands and stands with abundant undergrowth than was associated with coniferous stands or stands with little undergrowth. Woodland age had less effect on bird community composition than the extent of undergrowth and the conifer to broadleaf ratio. The results of this work have relevance to the enhancement of winter bird communities in commercial forests.     

Bryophyte community composition and habitat specificity in the natural forests of Terceira,Azores

In order to characterize the main areas of natural forest on Terceira Island (Azores), some of the most interesting European forests due to their rich and diverse flora of endemic as well as relict species, six forest stands were studied and their flora inventoried using 226 randomized quadrats, which revealed one anthocerote, 64 liverworts, 41 mosses and 16 macrolichen taxa. The alpha-diversity of the samples is particularly species-rich, some quadrats (30 × 30 cm) including more than 25 bryophyte species. A quantitative analysis of the vegetationenvironment relationships consistently showed that the distributions of the native forest bryophytes and lichens of Terceira are governed by a complex set of factors related to water availability, the status of the substrata and the influences of the vascular plant community. Considering the generally high values of the Sørensen indices and the low number of specialist species found with Lloyd’s index, the differences are more in terms of dominance of species than in terms of species composition. In fact, substratum type was clearly important in the DCA and TWINSPAN analysis using species cover abundance values, largely explaining the distribution of bryophyte species between Juniperus brevifolia (Seub.) Antoine and Laurus azorica (Seub.) Franco bark. The eight putative plant community type groupings achieved with these multivariate methods were able to elucidate some major bryophyte – substratum relationships, that had not previously been considered and they offer a framework for future research.     

How isolated are Pleistocene refugia? Results from a study on a relict woodrat population from the Mojave Desert,California

Pleistocene vicariance is often invoked to explain the disjunct populations of animals in habitat refugia throughout the southwestern United States. The combined effects of small population size and isolation from the rest of the contiguous range are thought to result in genetic differentiation of relict organisms. Here, we describe a relict population of dusky‐footed woodrats (Neotoma fuscipes Baird) found in a pinyon‐juniper‐oak community in a small mountain range within the Mojave Desert. We compare morphological and genetic data for these individuals with two populations within the contiguous range, and with another species of woodrat (Neotoma lepida). We also examine the distributional overlap between contemporary oak species and dusky‐footed woodrats, and estimate the potential oak woodland habitat available during the late Quaternary. As expected, both the morphological and genetic analysis confirm that the relict population is N. fuscipes. Within the limitations of our data, we detect no evidence of differentiation. Instead, the relict population forms a paraphyletic group with the nearest population within the contiguous range. This may be explained by the combined influences of a shorter period of isolation and a greater effective population size than was originally expected. The linkage between contemporary oak and dusky‐footed woodrat distributions is very tight, reinforcing the idea of an obligate relationship between the two. We estimate that at ~8000 ybp, pinyon‐juniper‐oak woodlands may have covered ~53% of the central Mojave, forming large contiguous areas of habitat. Although considerably more fragmented, at present ~12% of the area consists of relict woodlands. Our results suggest that there may be numerous other woodrat refugia, with a relatively high degree of connectiveness between the larger ones. Animals within them may effectively function as a single metapopulation, buffering against occasional stochastic extinction events.     

Integrating multiple landscape-scale drivers in the lichen epiphyte response: climatic setting, pollution regime and woodland spatial-temporal structure

Aim To quantify the role of multiple biodiversity drivers – pollution, woodland structure and climate – controlling lichen epiphyte composition and diversity. Location  Scotland, north‐west Europe. Methods Four compatible datasets were assembled: site‐scale species distribution data (response) and base‐line modelled data on climate, pollution loads and extent of old‐growth woodland (explanatory variables). First, partial‐canonical correspondence analysis was used: (1) to compare the importance of environmental variables to pure spatial effects and (2) to partition the importance of environmental variables in explaining species composition. Secondly, patterns of species richness were investigated using multiple least‐squares regression. Results Old‐growth woodland was the most important control of species richness. Pollution was the most important explanatory variable for species composition. The impact of pollution on composition (and to a lesser extent on richness) is explained: (1) By recovery of lichens with declining SO₂ pollution, although with epiphyte composition shifted by the recent effects of N‐pollution and (2) By the limited spatial extent of severe pollution, and generally low‐to‐moderate pollution loads across our study area, combined with the positive effect of old‐growth woodland extent in controlling species richness. The effect of climate and old‐growth woodland on species composition covaried, supporting an interaction between habitat quality and climatic setting, which may be important in understanding the epiphyte response to climate change. Conclusions Advances in conservation planning will likely require an integrated approach to understanding simultaneous effects of multiple drivers, providing opportunities for integrated management strategies. Our study provides a preliminary example of this approach by combining three key biodiversity drivers into a single framework for lichen epiphytes. Thus, reducing pollution loads may make old‐growth woodland that currently exists in a polluted landscape available for colonization, thereby extending the available habitat for epiphytes, and facilitating an effective species response to climate change.     

The Importance of Acacia Trees for Insectivorous Bats and Arthropods in the Arava Desert

Anthropogenic habitat modification often has a profound negative impact on the flora and fauna of an ecosystem. In parts of the Middle East, ephemeral rivers (wadis) are characterised by stands of acacia trees. Green, flourishing assemblages of these trees are in decline in several countries, most likely due to human-induced water stress and habitat changes. We examined the importance of healthy acacia stands for bats and their arthropod prey in comparison to other natural and artificial habitats available in the Arava desert of Israel. We assessed bat activity and species richness through acoustic monitoring for entire nights and concurrently collected arthropods using light and pit traps. Dense green stands of acacia trees were the most important natural desert habitat for insectivorous bats. Irrigated gardens and parks in villages and fields of date palms had high arthropod levels but only village sites rivalled acacia trees in bat activity level. We confirmed up to 13 bat species around a single patch of acacia trees; one of the richest sites in any natural desert habitat in Israel. Some bat species utilised artificial sites; others were found almost exclusively in natural habitats. Two rare species (Barbastella leucomelas and Nycteris thebaica) were identified solely around acacia trees. We provide strong evidence that acacia trees are of unique importance to the community of insectivorous desert-dwelling bats, and that the health of the trees is crucial to their value as a foraging resource. Consequently, conservation efforts for acacia habitats, and in particular for the green more densely packed stands of trees, need to increase to protect this vital habitat for an entire community of protected bats.