Broadleaf Woodland Research Articles

Unravelling a hidden synergy: How pathogen-climate interactions transform habitat hydrology and affect tree growth

Interactions between multiple global change stressors are a defining characteristic of the Anthropocene. Tree-associated pathogens are affecting forested ecosystems worldwide and occur in the context of increased frequency and intensity of extreme climate events such as heat waves, droughts, and floods. The effects of these events, along with subsequent changes in environmental conditions, on remaining and regenerating trees, are not well understood but crucial for the restoration and conservation of forested habitats.In this study, we investigate ash (Fraxinus excelsior) dieback in a temperate broadleaf woodland as a case study to explore the processes influencing non-infected trees during pathogen-induced mortality events. Utilising an experimental setup, we examine tree growth rates at different chronological stages of the disease, including naturally progressing ash dieback (4–5 years since disease outbreak), accelerated ash dieback where ash trees have been girdled (10–15 years), and negligible ash dieback (<20 % ash trees).During a year with typical climatic conditions (2021), soils in accelerated ash dieback plots remained saturated throughout the summer due to insufficient transpiration (57 % higher in the accelerated dieback plots), suggesting a significantly increased risk of summer run-off and floods. However, tree growth rates in these plots were not affected (t-test, t = −0.3 to 1.2, p > 0.05). Conversely, anomalously dry years, such as the 2022 summer drought, saw higher soil moisture in the accelerated ash dieback plots (t-test, t = 4.8, p < 0.01) acting as a buffer, resulting in normal tree growth during drought compared to greatly reduced growth in plots with weaker dieback.These findings emphasise the complex interactions between extreme climate events and pathogen outbreaks. Better understanding of the relationships between pathogens and hydrology on tree growth is imperative and detailed long-term studies on tree growth and hydrology will facilitate and improve mitigation strategies.

Moths respond to key habitat structures in conifer plantations managed as irregular high forest

Conifer plantations need to deliver greater multi-functionality beyond the production of timber. This includes the support of biodiversity and associated ecosystem functioning. Forest managers are increasingly adopting novel, more sustainable forest management techniques such as irregular silviculture, a type of continuous cover forestry, to manage plantations, in response to climate change. This may confer benefits to important elements of woodland biodiversity such as moths, by creating plantations that have diverse vertical structure and a permanent canopy (called irregular high forest). In this study at two estates in south-west Britain we specifically tested whether moth species richness and abundance (at the guild and overall level) were associated with (1) surrounding land cover types and (2) habitat structures within stands undergoing transformation using irregular silviculture. A total of 268 species of 11,582 individuals were recorded. Moths responded to all four landscape cover types, negatively to arable and conifer woodland, positively for broadleaf woodland, and both positively and negatively for improved grassland. Moth richness and abundance had a positive association with basal area (albeit below standard even aged stocking rates with most plots around 40–45 m2ha) and a weak positive association with higher vertical structural complexity (indicated by a more developed understorey and sub-canopy layers). Moth abundance had a moderate positive association with broadleaf canopy where we recommend plantations should have at least 10–15 % broadleaf canopy cover. Moth richness and abundance were negatively associated to mean tree diameter and canopy openness. Many of these features are more prevalent in stands further progressed towards irregular high forest. We show how moth communities can be maintained via more sustainable forestry management techniques that increase overall habitat and structural complexity.

Variation in hazel dormouse (Muscardinus avellanarius) presence in hedge and scrub habitats

Abstract Habitat restoration at a landscape scale is key to reversing the loss of biodiversity arising from habitat destruction. In landscapes that are intensively used by people, such as for agriculture, valuable restoration efforts might be applied not just to ‘prime’ habitats that are known to have strong associations with target species, but also to ‘sub‐prime’ habitats that might nevertheless provide sufficient resources to support populations. Hazel dormouse (Muscardinus avellanarius) populations are in chronic decline in the UK. The species is typically associated with broadleaf woodland but restoration of this habitat at scale in agricultural landscapes is difficult. Other habitats used by dormice might, therefore, provide opportunities for restoration. We investigated the use by hazel dormice of hedgerow and scrub habitats in southwest England. From June–November 2022, using footprint‐recording tunnels, we surveyed 38 hedges and 21 scrub patches in the vicinity of 18 sites known to contain established dormouse populations. We found that dormice were frequently present in scrub (9.3 detections per 100 tunnel checks, 95% confidence interval 6.6–12.0) and less frequently in hedges (4.5 detections, 95% CI 3.2–5.8). In scrub patches, dormice were present more frequently as the abundance of dormice in the closest population increased, and less frequently where bracken (Pteridium aquilinum) was dominant. In hedges, dormice were detected more frequently where there was abundant hazel (Corylus avellana) and honeysuckle (Lonicera periclymenum), as frequency of intersections with other hedges increased, and where an earthen bank was not present. Understanding hazel dormouse association with a wide range of habitats, particularly scrub, offers more opportunities for habitat restoration as part of species conservation strategies.

Investigating the impact of woodland placement and percentage cover on flood peaks in an upland catchment using spatially distributed TOPMODEL

AbstractWoodlands can reduce downstream flooding, but it is not well known how the extent and distribution of woodland affects reductions in peak flow. We used the spatially distributed TOPMODEL to simulate peak flow during a 1 in 50 year storm event for a range of broadleaf woodland scenarios across a 2.6 km2 catchment in Northern England. Woodland reduced peak flow by 2.6%–15.3% depending on the extent and spatial distribution of woodland cover. Cross slope and riparian woodland resulted in larger reductions in peak flow, 4.9% and 3.3% for a 10‐percentage point increase in woodland cover respectively, compared to a 2.7% reduction for woodland randomly located across the catchment. Our results demonstrate that increased woodland cover can reduce peak flows during a large storm event and suggest that targeted placement of woodland can maximise the effectiveness of natural flood management interventions.

Applying genomic approaches to identify historic population declines in European forest bats

Abstract Anthropogenically driven environmental changes over recent centuries have led to severe declines of wildlife populations. Better tools are needed to assess the magnitude and consequences of these declines. Anecdotal evidence suggests European bat populations have suffered substantial declines in the past centuries. However, there is little empirical evidence of these declines that can be used to put more recent population trends into historic context. This study is a collaboration between academics and conservation practitioners to develop molecular approaches capable of providing evidence of historic population changes that can inform conservation status assessments and management. We generated a genomic dataset of 46,872 SNPs for the Western barbastelle, Barbastella barbastellus, a regionally Vulnerable bat species, including colonies from across the species' British and Iberian ranges. We used a combination of landscape genetics and model‐based inference of demographic history to identify both evidence of population size changes and possible drivers of these changes. Levels of genetic diversity increased and inbreeding decreased with increasing broadleaf woodland cover around the colony. Genetic connectivity was impeded by artificial lights and facilitated by rivers and broadleaf woodland cover. The demographic history analysis showed that both the northern and southern British barbastelle populations have declined by 99% over the past 330–548 years. These declines may be linked to the loss of large oak trees and native woodlands due to shipbuilding during the early colonial period. Synthesis and applications. Genomic approaches can provide a better understanding of the conservation status of threatened species, within historic and contemporary contexts, and inform their conservation management. Our findings of will directly influence the definition of the Favourable Conservation Status of the barbastelle, in turn influencing considerations of the conservation of the species in development plans. Knowledge gained will also help set species recovery targets. Policymakers are interested in using our approach for other species. This study shows how we can bridge the implementation gap between genomic research and direct conservation applications. There is an urgent need to carry out such collaborative studies for other priority species to enable informed species recovery interventions via policy mechanisms and project delivery.

Mapping the Late Miocene Pyrenean Forests of the La Cerdanya Basin, Spain

The Late Miocene palaeofloras of the La Cerdanya Basin represent a unique look into the Pyrenean Miocene forested areas of the Iberian Peninsula at a time when the European warm and humid climate was experiencing progressive cooling and aridification. Macrofossils (leaves, seeds, fruits and cones) and miospores from several outcrops revealed the composition and abundances of the different plant species present in the area during the Tortonian and early Messinian geological stages (ca. 11.1–5.7 Ma). These fossils were found in the sediment deposits of an ancient lake system situated in the southwestern part of the basin. Previous studies indicated the presence of highly diversified mixed mesophytic forests with broadleaved evergreen and deciduous trees and conifers. However, the spatial structure and distribution of these forest types remains unknown. In the present work, the biomization method was used to infer the different late Miocene vegetation types from the basin. The extent of these vegetation types was calculated using a methodology for mapping vegetation units from fossil and biome data. While previous attempts at mapping Miocene vegetation units had a broad geographical scale, the present work aimed to map the extent of the vegetation units at a small scale, recreating local and specific vegetation changes in an abrupt basin. Results showed similarly high scores between for four biome types, which represent the different types of vegetation that coexisted in the basin during the Tortonian and the early Messinian: warm-temperate evergreen broadleaf and mixed woodlands (WTEM biome), temperate deciduous forests (TEDE) and cool conifer forests (COMX and COEG). Their extent was depicted in two vegetation maps, which account for differences in palaeoaltitude and palaeoclimate. These forests occupied different vegetation belts, which shifted upwards and downwards with climatic variations and the progressive uplift of the Pyrenees during the late Miocene. Azonal riparian forests and wetland vegetation occupied the more humid areas in the centre of the basin. Nonetheless, dry conditions during the early Messinian and decrease in the lake area degraded the wetland environments, which were partially replaced by broadleaved evergreen mixed woodlands.

Can hydrological models assess the impact of natural flood management in groundwater‐dominated catchments?

AbstractNatural flood management (NFM) is widely promoted for managing flood risks but the effectiveness of different types of NFM schemes at medium (100–1000 km2) and large scales (&gt;1000 km2) remains widely unknown. This study demonstrates the importance of fully understanding the impact of model structure, calibration and uncertainty techniques on the results before the NFM assessment is undertaken. Land‐based NFM assessment is undertaken in two medium‐scale lowland catchments within the Thames River basin (UK) with a modelling approach that uses the Soil and Water Assessment Tool (SWAT) model within an uncertainty framework. The model performed poorly in groundwater‐dominated areas (P‐factor &lt;0.5 and R‐factor &gt;0.6). The model performed better in areas dominated by surface and interflow processes (P‐factor &gt;0.5 and R‐factor &lt;0.6) and here hypothetical experiments converting land to broadleaf woodland and cropland showed that the model offers good potential for the assessment of NFM effectiveness. However, the reduction of large flood flows greater than 4% in medium‐sized catchments would require afforestation of more than 75% of the area. Whilst hydrological models, and specifically SWAT, can be useful tools in assessing the effectiveness of NFM, these results demonstrate that they cannot be applied in all settings.

Optimizing forest canopy structure retrieval from smartphone‐based hemispherical photography

Abstract Hemispherical photography (HP) is a long‐standing tool for forest canopy characterization. Currently, there are low‐cost fisheye lenses to convert smartphones into highly portable HP equipment (smartphone‐based HP, hereafter SHP). However, there is an obstacle to having a close‐to‐ideal method for citizen science and large‐scale or opportunistic sampling: the known sensitivity of HP to illumination conditions. The purpose of this paper is to test a ready‐to‐use approach based on previous research and to contribute to quantifying the errors associated with choosing SHP in non‐recommended light conditions over well‐established HP practices. In 30 locations distributed in broadleaf and coniferous woodlands, a total of 1080 photographs were taken with two smartphone models, manipulating the exposure, and under varied sky conditions. After image binarization, accurate reference data was employed to evaluate the reliability of extracting canopy parameters from SHP. The proposed methodology can reliably quantify canopy openness (RMSE ~0.04) and plant area index (RMSE ~0.4). Results suggest that SHP, when used following the recommendations of the present study, allows retrieval of reliable canopy metrics independently of sky conditions and forest type.

Organic litter dynamics in headwater streams draining contrasting land uses

Climate change could alter fluxes of organic matter and macronutrients through freshwater ecosystems potentially affecting stream organisms. However, riparian controls on litter dynamics offer an opportunity to adapt headwaters to climate change by protecting or restoring riparian vegetation. We assessed how riparian land cover and climatic variability affected the supply, retention and downstream transport of particulate organic matter (POM) in headwaters—the most extensive small water bodies in temperate landscapes. Leaf litter inputs, benthic stocks and suspended organic matter were measured nominally monthly in second–third-order streams draining broadleaf woodland, conifer, acid moorland and circumneutral moorland over four years with varying discharge. Streams draining broadleaf woodland received more leaf litter from the riparian zone than conifer and moorland and transported higher concentrations of CPOM and FPOM at base flows. Broadleaf sites had higher CPOM stocks, even after hydrological events that reduced CPOM in conifer and moorland sites. In contrast, FPOM dynamics reflected hydrological conditions irrespective of land cover. These results show how some organic matter fractions in streams are sensitive to hydrological conditions, illustrating how wetter climates will influence FPOM exports. Nevertheless, riparian broadleaves have the potential to offset climatic effects on organic matter processing in headwaters through the replenishment and retention of CPOM.

Harnessing practitioner knowledge to inform the conservation of a protected species, the hazel dormouse Muscardinus avellanarius

Abstract Conservation decisions are typically constrained by the availability of published evidence. Practitioners and non‐academic experts often possess additional knowledge, including about the practical plausibility of conservation actions, which may lead to more effective planning and outcomes. However, practitioner knowledge is rarely considered during formal evidence syntheses. Alongside a formal literature review, we conducted 26 interviews involving 38 conservation professionals to elicit their knowledge of the conservation of a protected and declining species in England, the hazel dormouse Muscardinus avellanarius. Practitioners and non‐academic experts provided additional insights about dormouse ecology and conservation, beyond those synthesized from the published literature, though we found few contradictions between these different information sources. Instead, practitioner knowledge helped to verify, clarify and expand upon evidence from empirical studies. In general, practitioners emphasized that dormice are far more adaptable than traditionally perceived, with thriving populations found in hedgerows, scrub, road verges and railway verges, rather than solely within broadleaf woodlands. Proposed opportunities for restoring dormouse populations included improving hedgerow management, creating new woodlands, bringing existing woodlands back into management, setting aside unproductive land and improving habitat connectivity. However, participants emphasized the need for landscape‐scale approaches, accounting for the impacts of climate change, and better surveying and monitoring. Key practical considerations included overcoming time and financial constraints, providing better advice, knowledge and training, changing attitudes of land owners and managers and balancing other demands such as agricultural productivity and the requirements of other species. Despite the insights they provided, participants highlighted many remaining knowledge gaps. These included uncertainties arising from the published literature, as well as scarcely studied topics that are of major practical importance, namely the effectiveness of dormouse mitigation measures in planning and development, and the impacts of anthropogenic disturbance and pollution on dormice. Our findings improve the evidence base for restoring hazel dormouse populations and for further empirical evidence gathering. More generally, the study highlights how practitioner knowledge can help both to supplement traditional published evidence and to better frame conservation programmes, which may lead to more successful outcomes.

A preliminary survey of the ground-dwelling spider assemblages of the Ndumo Game Reserve, South Africa (Arachnida: Araneae)

Ground-dwelling spider assemblages were sampled by pitfall trapping in four contrasting biotopes in the Ndumo Game Reserve, South Africa, situated in the Maputaland-Pondoland-Albany biodiversity hotspot. Over two years (2006 and 2007) in two seasons (mid-summer and winter, 10 days each) 1261 spiders were collected, representing 31 families and 121 species. Twenty-five taxa were recorded from Ndumo for the first time. Spider activity densities and species richness were highest in the deciduous broadleaf woodland (BW, n = 538, S = 106), followed by Albizia adianthifolia-Vachellia tortilis woodland (AW, n = 358, S = 70), sand forest (SF, n = 188, S = 74), and Mahemane thicket (MT, n = 177, S = 53). The four most abundant species were Asemesthes ceresicola Tucker, 1923 (Gnaphosidae, 27.8%), Arctosa sp. (Lycosidae, 8.4%), Pardosa crassipalpis Purcell, 1903 (Lycosidae, 7.4%), and Stenaelurillus guttiger (Simon, 1901) (Salticidae, 5.2%). Species richness and activity densities were strongly seasonal, with sharp decreases in winter. Conservation assessments could not be carried out on a sizable proportion of the species collected, as they represent new taxa or were only represented by immatures (30.6%), but of the remainder the majority had a conservation status of Least Concern (64.5%), with very few being Data Deficient (4.1%) and a single vulnerable species being collected, Massagris natalensis Wesołowska & Haddad, 2009. However, among the new taxa not assessed there may be several Maputaland endemics.

Moth declines are most severe in broadleaf woodlands despite a net gain in habitat availability.

While agricultural intensification and habitat loss are cited as key drivers of moth decline, these alone cannot explain declines observed in UK woodlands – a habitat that has expanded in area since 1968.We quantified how moth communities changed across habitats and regions and determined how species traits interacted with habitat in predicting moth abundance change. We hypothesised that, in woodlands, species more vulnerable to shading and browsing by deer (species specialising on forbs, shrubs and shade‐intolerant plants) had declined more severely than other species, and that moth decline in woodlands was more severe at sites more susceptible to deer damage.We modelled abundance, biomass, species richness and diversity from 1968 to 2016 and explored how these interacted with habitat and region. We also modelled the interaction between habitat and two moth species traits: larval feeding guild and shade‐tolerance of hostplant.Moth declines were consistently highest in broadleaf woodland. Abundance, biomass, species richness and diversity declined significantly by −51%, −52%, −14% and −15% in woodlands, respectively, compared to national trends of −34%, −39%, −1% (non‐significant) and +10%. Declines were no greater in woodlands more susceptible to deer browsing damage. Traits based analysis found no evidence that shading and intensive browsing by deer explained moth declines in woodland.Moth decline was more severe in broadleaf woodlands than in intensively managed farmlands. We found no evidence that deer browsing or increased shading has driven these trends: the primary cause of the decline of moths in woodlands remains unclear.

Overland flow velocity and soil properties in established semi‐natural woodland and wood pasture in an upland catchment

AbstractManagement of upland land‐use has considerable potential for mitigating flood risk by increasing topsoil storage and slowing overland flow. Recent work has highlighted the potential for vegetation to impact the velocity of saturation‐excess overland flow. Woodland creation is widely proposed for Natural Flood Management (NFM), but data on saturation‐excess overland flow in woodland habitats is lacking. Here we measure soil properties and overland flow velocities in established broadleaf woodland and wood pasture with an understorey dominated by either grass or bracken. We show that wood pasture dominated by bracken has overland flow velocity 12–20% lower than established broadleaf woodland and 19–27% lower than grass‐dominated wood pasture. Established woodland soils exhibited eight times higher saturated hydraulic conductivity than bracken‐dominated wood pasture and 80 times higher than grass‐dominated wood pasture. We conclude that upland habitats can be managed to reduce flood risk, first by storing storm water in the soil and then by reducing overland flow velocity through rough surface vegetation. These factors combine to reduce floods by delaying the onset of overland flow runoff and slowing its delivery to streams. It is clear than Manning's n is far from constant in these shallow overland flows, the development of overland flow datasets is, therefore, also beneficial for improving the theory and practice of hillslope rainfall‐runoff modelling.

Habitat mediates coevolved but not novel species interactions.

Ongoing recovery of native predators has the potential to alter species interactions, with community and ecosystem wide implications. We estimated the co-occurrence of three species of conservation and management interest from a multi-species citizen science camera trap survey. We demonstrate fundamental differences in novel and coevolved predator–prey interactions that are mediated by habitat. Specifically, we demonstrate that anthropogenic habitat modification had no influence on the expansion of the recovering native pine marten in Ireland, nor does it affect the predator's suppressive influence on an invasive prey species, the grey squirrel. By contrast, the direction of the interaction between the pine marten and a native prey species, the red squirrel, is dependent on habitat. Pine martens had a positive influence on red squirrel occurrence at a landscape scale, especially in native broadleaf woodlands. However, in areas dominated by non-native conifer plantations, the pine marten reduced red squirrel occurrence. These findings suggest that following the recovery of a native predator, the benefits of competitive release are spatially structured and habitat-specific. The potential for past and future landscape modification to alter established interactions between predators and prey has global implications in the context of the ongoing recovery of predator populations in human-modified landscapes.

Hydrological impact of widespread afforestation in Great Britain using a large ensemble of modelled scenarios

Ambitious afforestation proposals in the last decade target potential flood mitigation and carbon storage benefits but without a systematic, large-scale (>1000 km2) quantitative evaluation of their impacts on streamflow. Here, we assess the impact of afforestation on streamflow across twelve diverse catchments (c.500-10,000 km2) using a high-resolution land-surface model with a large ensemble of afforestation scenarios. Afforestation consistently decreases median and low streamflow. Median modelled flow is reduced by 2.8% ± 1.0 (1 s.d.), or 10 mm yr−1 ± 2.1 (1 s.d.), for a ten-percentage point increase in catchment broadleaf woodland. We find no nationally-consistent reduction of extreme floods. In larger catchments, planting extent is a stronger control on streamflow than location. Our results suggest that despite its potential environmental and societal benefits, widespread afforestation may inadvertently reduce water availability, particularly in drier areas, whilst only providing a modest reduction in extreme flood flows.

The impact of semi‐natural broadleaf woodland and pasture on soil properties and flood discharge

AbstractWoodlands can reduce the risk of rainfall‐generated flooding through increased interception, soil infiltration and available storage. Despite growing evidence, there is still low confidence in using woodlands as a flood mitigation method due to limited empirical data, particularly for broadleaf woodlands. We measured soil properties and streamflow for nine small (&lt;0.2 km2) upland catchments and compared mature semi‐natural broadleaf woodland where no stock grazing occurs to pasture with varied grazing intensity. We compared streamflow across 28 storm events including a 1 in 10‐year event, two 1 in 4‐year events and five 1 in 1.5‐year events, identified over a 13‐month period. We found that semi‐natural broadleaf woodlands reduce specific peak discharge by 23%–60% and peak runoff coefficients by 30%–60% compared with pasture. Response to storm events took 14–50% longer in woodland compared to pasture. These differences in flood response are partly explained by more permeable woodland soils, 11–20 times greater than pasture soil. The more muted response of wooded catchments to storm events is consistent across the storms investigated, including Storm Ciara, a 1 in 10‐year event. Our analysis strengthens the argument that semi‐natural woodlands can reduce rainfall‐generated flooding contributing to the evidence base for natural flood management.

Large-scale citizen science survey of a common nocturnal raptor: urbanization and weather conditions influence the occupancy and detectability of the Tawny Owl Strix aluco

ABSTRACT Capsule Tawny Owl Strix aluco site occupancy and detectability are influenced by habitat and environmental variables. Aims: To determine factors influencing Tawny Owl occupancy and detectability around British homes and gardens using a large-scale citizen science survey across two main survey periods. Methods Surveys of 20 min duration were undertaken one evening a week from the homes and gardens of volunteers, for up to 26 weeks between October and March of 2005/2006 and 2018/2019, and analysed primarily using multi-season occupancy modelling. Results During two survey periods, more than 9000 sites were surveyed across the breeding range of the Tawny Owl within Britain. The main drivers of occupancy were found to be the extent of broadleaf woodland cover and the degree of urbanization. Detection probability was influenced by date, time, weather, and moon phase. Using the current method, a minimum of five to six survey visits per site would be required to have 95% confidence over the presence or absence of Tawny Owls at a given site, but it may be possible to optimize the survey method further to increase efficiency by surveying in the autumn or early spring, early after dusk, and on cloudless dry evenings close to the full moon. Conclusion The findings indicate that survey methodologies for surveying Tawny Owls can be optimized to increase the efficiency of detection, if present at a site. We highlight the need for further research on the effects of urbanization on Tawny Owls, particularly with regards to artificial light pollution and its effects on behaviour and settlement, along with the need for greater understanding of Tawny Owl activity budgets, which would aid the interpretation of survey results.

The Return of Wooded Landscapes in Wales: An Exploration of Possible Post-Brexit Futures

Changes in agricultural policy may have a rapid impact, even on landscapes which have taken millennia to form. Here we explore the potential impact of the UK leaving the EU as a catalyst for profound changes in the pastoral landscapes of Wales. Impending change of the trading regime governing agricultural produce, concurrent with public pressure to use agricultural subsidies for environmental goals, may lead to unforeseen consequences for the Welsh natural environment. We employ a combination of change demand modelling and a ‘story and simulation approach’ to project the effect of five hypothetical plausible scenarios on land use and land use change in Wales by 2030. We show that the most extreme trade scenario would result in a significant expansion of broadleaf woodland across much of Wales. By contrast, the ‘green futures’ scenario introduced to supersede the Common Agricultural Policy, results in significant expansion of woodland but not at the level seen with the more extreme trade scenarios.

Irregular silviculture positively influences multiple bat species in a lowland temperate broadleaf woodland

Changing economics in the 20th century led to losses and fragmentation of semi-natural woodland in Britain and to a reduction in active woodland management with many becoming increasingly neglected, even-aged and with closed canopy. Lack of woodland management is known to contribute to declines in some taxonomic groups, for example birds. However, the response of bats to changes in woodland structure are poorly understood. We compared two measures of bat activity, derived from static acoustic recorders across 120 sample plots in coppice, irregular high forest (uneven-aged, continuous cover) and limited intervention (under-managed, even-aged) management stands, within a large tract of ancient woodland in southern England. Bat species richness was highest in irregular high forest stands, and there were significant differences in occupancy rates for most bat species across stand management types. Coppice recorded low activity of several bat species and irregular high forest showed high occupancy rates, including for Barbastelle Barbastella barbastellus, which is IUCN listed as near threatened. The occupancy rates in stand management types differed for some bat species between mid- and late summer counts, suggesting seasonal variation in habitat use. Within stands, most bat species were associated with opened canopy, lower growing stocks and reduced densities of understorey, and to a lesser extent, with large-girthed trees and presence of deadwood snags. In some cases, species responded to a given habitat variable similarly across the three stand management types, whereas in others, the response differed among stand management types. For example, increased numbers of large-girthed trees benefitted a number of bat species within coppice where these were least common, but not in irregular stands. Irregular silviculture high forest appears to provide many of the structural attributes that positively influence occupancy of several woodland bat species, including Barbastella barbastellus.

Assessing the impact of land use and liming on stream quality, diatom assemblages and juvenile salmon in Wales, United Kingdom

Many freshwaters in base-poor upland areas of Britain continue to be affected by acidification as a result of deposition of air pollutants, and agricultural and forestry practices. The effects of land use and annual liming on stream chemistry, diatoms and salmon populations were investigated over eight years in the upper catchment of the River Wye, Wales, United Kingdom. Variations in water chemistry, diatom species composition and diversity, and in the index Diatom Acidification Metric (DAM) were compared between different types of land cover and flow conditions, and before and after applications of lime. Two methods of liming, hydrological source (catchment) liming and sand liming (in-stream liming), were used to reduce stream acidity. Electrofishing was carried out for several years before and after liming to monitor the recovery of salmon populations.Prior to liming, water chemistry differed between stream sub-catchments with differing land use. ANC, Ca concentrations and pH were lower, and Al concentrations were higher, in areas with conifers and acid grassland than in areas with improved grassland and broadleaf woodland. After liming pH increased, but the effects differed between sites and were dependent upon pH levels before any liming began, flow conditions, and the method of liming. An increase in pH during high flows was evident at many sites where acid episodes had occurred prior to liming.Diatom species richness and diversity were low, many sites supporting only 10–15 species. Correlations of richness and diversity with water chemistry were not significant but there was a tendency for low pH sites to support very few species. Species richness was highest in areas adjoining broadleaf woodland and improved grassland, and lowest in areas adjoining conifer plantations.Diatom species composition changed after liming and depended on the type of dominant land cover in the catchment areas and the method of liming. Species tolerant of low pH, in particular Eunotia exigua, became less abundant and were replaced by acid-sensitive species, predominantly Achnanthidium minutissimum. DAM index values and ecological quality ratios (EQR), which were both lower in conifer and acid grassland areas before liming than elsewhere, improved after liming and in many areas the ecological status class of limed streams became good or high. The change to diatom assemblages with predominantly acid-sensitive species after liming correlated with increasing numbers of juvenile salmon and their expansion upstream to sites that had lacked fish prior to liming.