Woodland Landscape Research Articles

Multiple ecosystem services in a working landscape.

Policy makers and practitioners are in need of useful tools and models for assessing ecosystem service outcomes and the potential risks and opportunities of ecosystem management options. We utilize a state-and-transition model framework integrating dynamic soil and vegetation properties to examine multiple ecosystem services—specifically agricultural production, biodiversity and habitat, and soil health—across human created vegetation states in a managed oak woodland landscape in a Mediterranean climate. We found clear tradeoffs and synergies in management outcomes. Grassland states maximized agricultural productivity at a loss of soil health, biodiversity, and other ecosystem services. Synergies existed among multiple ecosystem services in savanna and woodland states with significantly larger nutrient pools, more diversity and native plant richness, and less invasive species. This integrative approach can be adapted to a diversity of working landscapes to provide useful information for science-based ecosystem service valuations, conservation decision making, and management effectiveness assessments.

Informing climate adaptation pathways in multi-use woodland landscapes using the values-rules-knowledge framework

An emerging planning framework for climate adaptation focuses on interactions among societal values, institutional rules and scientific and experiential knowledge about biophysical impacts of climate change and adaptation options. These interactions shape the decision context that can enable or constrain effective adaptation. To illustrate the operationalisation of this ‘values-rules-knowledge’ (VRK) framework we developed biophysical adaptation pathways for agricultural landscapes of south-eastern Australia, which are expected to become warmer and drier under climate change. We used the VRK framework to identify potential constraints to implementing the pathways. Drawing on expert knowledge, published literature, biodiversity modelling and stakeholder workshops we identified potential adaptation pathways for (1) the production matrix, (2) high conservation value remnant eucalypt woodlands, and (3) woodland trees. Adaptation options included shifts from mixed cropping-grazing to rangeland grazing or biomass enterprises; promoting re-assembly of native ecological communities; and maintaining ecosystem services and habitat that trees provide. Across all pathways, applying the VRK framework elucidated fifteen key implementation constraints, including limits to farm viability, decreasing effectiveness of environmental legislation and conflicting values about exotic plants. Most of the constraints involved interactions among VRK; 13 involved rules, eight involved values, and seven involved knowledge. Value constraints appeared most difficult to address, whereas those based on rules or knowledge were more tangible. The lower number of knowledge constraints may reflect the scale of our analysis (which focused on decision points in pre-defined pathways); new knowledge and participatory approaches would likely yield a richer set of scenarios. We conclude that the VRK framework helps connect the biophysical knowledge-based view of adaptation with a perspective on the need for changes in social systems, enabling targeting of constraints to adaptation. Our focus on pathways and decision points in different sectors of the multi-use landscape highlighted the importance of group and higher level planning and policy for balancing the collective outcomes of multiple decisions by many land managers.

The Genesis and Exodus of Vascular Plant DOM from an Oak Woodland Landscape

Evaluating the collective impact of small source inputs to larger rivers is a constant challenge in riverine biogeochemistry. In this study, we investigated the generation of dissolved organic matter (DOM) in a small oak woodland catchment in the foothills of northern California, the subsequent transformation in lignin biomarkers and chromophoric DOM (CDOM) parameters during transport through the landscape to an exporting stream, and finally the overall compositional impact on the larger receiving stream and river. Our study included a natural leaching experiment in which precipitation passing through oak, pine, and grass litter and duff samples was collected after each of a series of storms. Also included were soil trench samples to capture subsurface flow, stream samples along with point-source reservoir inputs, and samples of canopy throughfall, stemflow, and gopher hole (bypass) flow. The litter/duff leaching study demonstrated changing DOM fractionation patterns throughout the season, as evidenced by changing lignin compositions in the leachates with each successive storm. This adds a necessary seasonal component to interpreting lignin compositions in streams, as the source signatures are constantly changing. Released DOM from leaching was modified extensively during transit through the subsurface to the stream, with preferential increases in aromaticity as evidenced by increases in carbon-normalized absorbance at 254 nm, yet preferential decreases in lignin phenols, as evidence by carbon-normalized lignin yields in the headwater stream that was less than half that of the litter/duff leachates. Our extensive number of lignin measurements for source materials reveals a much more complex perspective on using lignin as a source indicator, as many riverine values for syringyl:vanillyl and cinnamyl:vanillyl ratios that have previously been interpreted as degraded lignin signatures are also possible as unmodified source signatures. Finally, this study demonstrated that the impact of numerous small headwater streams can significantly overprint the DOM signatures of much larger rivers over relatively short distances spanning several to tens of kilometers. This finding in particular challenges the assumption that river studies can be adequately conducted by focusing only on the main tributaries.

Lateglacial to Late Holocene palaeoclimatic and palaeoenvironmental reconstruction of El Mirador cave (Sierra de Atapuerca, Burgos, Spain) using the small-mammal assemblages

El Mirador is a cave in the Sierra de Atapuerca (northern Iberian Peninsula) that contains 27 archaeological layers from the Lateglacial to the Late Holocene. A total of 4436 small-mammal remains have been analysed from these layers, and 19 taxa have been identified (three insectivores, seven chiropters and nine rodents). The palaeoenvironmental reconstruction based on a small-mammal analysis suggests that the entire sequence is dominated by a woodland landscape. Our climatic analysis characterises the climate in terms of an evolution from a cool and arid period in the Pleistocene layers (16,000 to 14,000calyr BP), probably related to Heinrich Event 1, to humid conditions and temperatures similar to nowadays in the Holocene layers in general. In MIR23 and MIR22 (7300 to 6800calyr BP) we detect an increase in temperature to levels above current values and an important decrease in rainfall. These climatic characteristics could be related to the end of the African Humid Period. Moreover, a short, slightly cooler event is registered in MIR11 (ca. 6300 to 5900calyr BP), coinciding with a change in the economic pattern in El Mirador. The results obtained on the basis of small-mammal studies are compared with multiproxy terrestrial data (pollen, charcoal, phytoliths, geochemistry, large mammals) and the Greenland ice-core record, as well as various other core records closer to the coasts of the Iberian Peninsula (MD95-2042, MD99-2331, MD95-2043 and SMP02-3). These comparisons show the agreement of the palaeoenvironmental and palaeoclimatic results with all the previous multiproxy and core-record data.

Assessing Threats and Conservation Status of Historical Centers of Oak Richness in California

Oak trees are emblematic of California landscapes, they serve as keystone cultural and ecological species and as indicators of natural biological diversity. As historically undeveloped landscapes are increasingly converted to urban environments, endemic oak woodland extent is reduced, which underscores the importance of strategic placement and reintroduction of oaks and woodland landscape for the maintenance of biodiversity and reduction of habitat fragmentation. This paper investigated the effects of human urban development on oak species in California by first modeling historical patterns of richness for eight oak tree species using historical map and plot data from the California Vegetation Type Mapping (VTM) collection. We then examined spatial intersections between hot spots of historical oak richness and modern urban and conservation lands and found that impacts from development and conservation vary by both species and richness. Our findings suggest that the impact of urban development on oaks has been small within the areas of highest oak richness but that areas of highest oak richness are also poorly conserved. Third, we argue that current policy measures are inadequate to conserve oak woodlands and suggest regions to prioritize acquisition of conservation lands as well as examine urban regions where historic centers of oak richness were lost as potential frontiers for oak reintroduction. We argue that urban planning could benefit from the adoption of historical data and modern species distribution modelling techniques primarily used in natural resources and conservation fields to better locate hot spots of species richness, understand where habitats and species have been lost historically and use this evidence as incentive to recover what was lost and preserve what still exists. This adoption of historical data and modern techniques would then serve as a paradigm shift in the way Urban Planners recognize, quantify, and use landscape history in modern built environments.

Scale Dependence of Oak woodland Historical Fire Intervals: Contrasting the barrens of Tennessee and Cross timbers of Oklahoma, USA

Characterization of scale dependence of fire intervals could inform interpretations of fire history and improve fire prescriptions that aim to mimic historical fire regime conditions. We quantified the temporal variability in fire regimes and described the spatial dependence of fire intervals through the analysis of multi-century fire scar records (8 study sites, 332 trees, 843 fire scars) derived from two historically post oak (Quercus stellata Wangenh.) woodland landscapes. Despite large differences in fire environment conditions, study sites (∼1 km2) burned frequently (mean fire interval [MFI] ≤10 yr) before Euro-American settlement (pre-EAS), with sites in Tennessee showing higher overall fire frequency than sites in Oklahoma, USA. Pre-EAS MFIs decreased exponentially with increasing spatial extent from individual trees (∼1 m2) to landscapes (∼100 km2). The relationship between MFI and spatial extent may help to explain how historical observations of annual burning could be recorded in woodlands, when experimental studies suggest that this is too frequent for tree recruitment. Further investigations of spatial dependence of fire intervals would improve our ability to relate historical and experimental fire data to present day fire prescriptions, and vice versa.

Spatiotemporal Patterns and Drivers of Forest Change from 1985–2000 in the Beijing-Tianjin-Hebei Region of China

Abstract: Forests are fundamental to maintaining ecological security and achieving regional sustainable development in China. Forest land change can result in many ecological problems including soil erosion, water shortages, drought and biodiversity loss. Based on landscape ecology and logistic regression we explored the spatiotemporal patterns and factors affecting forest land changes from 1985 to 2000 in the Beijing-Tianjin-Hebei Region of China. The results show decreased local fragmentation of woodland landscapes and that the shapes of forest patches have become more regular. For forest land cover change, soil organic matter content, slope type I (<5°), distance to the nearest village and per capita GDP were the most important independent variables from 1985 to 2000. This study indicates that spatial heterogeneity can affect the predictability of logistic regression models for forest land change.

Modelling future scenarios to improve woodland landscapes for birds in the Mediterranean

Agro-silvo-pastoral systems occupy much of the Mediterranean region. Promoting landscape heterogeneity in these systems is a potentially valuable management strategy to enhance woodland biodiversity. We evaluated the effects on birds of managing patches of olive groves and riparian galleries to promote heterogeneity of these systems in Portugal.For a large cork oak woodland we (i) used nesting season bird density estimates and habitat descriptors to generate suitability models for each studied species; (ii) identified areas suitable to establish new patches of riparian galleries and olive groves, and used this information to (iii) generate scenarios maps with different levels of cover of both habitats. Finally, (iv) the model of each bird species was applied over the future scenarios to estimate potential changes in its distribution and abundance.Future scenarios with greater availability of riparian vegetation resulted in major increases in projected populations of seven of the 21 studied species, but gains with increases of olive groves were predicted in just three species. Bird species predicted to increase the most with the recovery of riparian vegetation are presently among the least abundant in the region. Restoring riparian galleries would be highly beneficial for birds, whereas promoting traditional olive groves would have lower conservation implications.The methodology used proved helpful to select areas particularly appropriate for habitat management, generate simulated landscapes incorporating this management, and predict the population and spatial responses of species to these simulated scenarios, thus having a good potential to guide conservation management. Moreover, our results indicate that simple management measures should have substantial positive effects on the bird community of oak woodlands, without compromising the essential economic return of the system.

Earlier activity of Drosophila suzukii in high woodland landscapes but relative abundance is unaffected

Natural habitats can affect the population dynamics of mobile insects, and the spatial and temporal effects on agricultural pest species may be especially relevant for tailoring management strategies to the farm context. Drosophila suzukii Matsumura (Diptera: Drosophilidae) is suspected to utilize woodland habitat for wild hosts and overwintering with possible adverse effects of woods on adjacent fruit crops. A two-year study in the Upper Midwest, USA examined if the amount of woodland in the landscape affects early season activity and relative abundance of D. suzukii in raspberry fields. Thirty-five farms were selected to span a gradient of low-to-high woodland area at the 1.5 km scale. The first capture of D. suzukii occurred earlier at farms in high woodland landscapes. However, woodland area was not correlated with metrics of D. suzukii abundance in raspberry (growth rate, peak, fall, or total fly catch) suggesting similar crop infestation risk across landscapes. However, woodland area was negatively correlated with fall fly catch in the adjacent woods and significantly more flies were captured in the woods than raspberry. This study suggests woodland landscapes affect early season crop risk and the high numbers of D. suzukii in the woods have implications for understanding overwintering.

Germination of native and introduced plants from scats of Fallow Deer (Dama dama) and Eastern Grey Kangaroo (Macropus giganteus) in a south‐eastern Australian woodland landscape

SummaryIntroduced deer occur in many forests and woodlands in Australia and potentially play an important role in influencing the floristics and structure of these landscapes through eating plants and disseminating seeds. In a glasshouse trial, we tested whether field‐collected scats of Fallow Deer (Dama dama) contained viable plant seeds. Scats of deer obtained from a woodland study area in Kosciuszko National Park, New South Wales, produced seedlings from a range of native and introduced plant species. Forbs and herbs were dominant in these samples, confirming the grazing behaviour of deer at the time scats were collected. Samples of scats from Eastern Grey Kangaroos (Macropus giganteus), collected contemporaneously from the same sites as deer scats, also produced plant germinants. By volume, deer scats produced a greater diversity of plant germinants, including native and weed species, than did kangaroo scats. Although no weed species emanating from deer or kangaroo scats were of national significance, several species were of regional environmental significance, including Common Mullein (Verbascum thapsis), which was only found germinating out of deer scat, Stinkgrass (Eragrostis cilianensis) and Purpletop (Verbena bonariensis). In addition to dispersing viable seeds, Fallow Deer may also influence vegetation structure through their browsing. Further research is necessary to elucidate their respective role in dispersing native and introduced plants as well as any impacts that foraging behaviour might be having on woodland landscapes, to better inform management of the resident deer population.

How resilient are African woodlands to disturbance from shifting cultivation?

Large parts of sub-Saharan Africa are experiencing rapid changes in land use and land cover, driven largely by the expansion of small-scale shifting cultivation. This practice creates complex mosaic landscapes with active agricultural fields and patches of mature woodland, interspersed with remnant patches in various stages of regrowth. Our objective here was to examine the rate and extent to which carbon stocks in trees and soils recover after cultivation, and detail how this disturbance and regrowth affect patterns in tree species composition and diversity over 40 years of succession in a miombo woodland landscape in southeast Tanzania. We sampled 67 areas, including plots previously cleared for cultivation, active fields, and mature woodlands for reference purposes. Sites were further stratified by soil texture to test for associated effects. Tree carbon stocks accumulated at an average rate of 0.83 ± 0.10 Mg C x ha(-1) x yr(-1), with soil texture having no clear impact on accumulation rates. Bulk soil carbon stocks on both soil types appeared unaffected by both the initial land clearance and the subsequent regrowth, which resulted in no significant changes over time. Tree species diversity in regrowing plots developed rapidly and within -10 years was equivalent to that of mature woodland. Many of the species found in mature woodlands reappeared relatively quickly after abandonment, although species composition is expected to take considerably longer to recover, with at least 60-80 years required for the compositional similarity between regrowing and mature woodlands to reach levels similar to that among nearby mature woodlands. Through impacts on β-diversity, disturbance was also found to increase the total number of tree species present in the landscape, with many of the recorded species only found in regrowing woodlands. Our results are of relevance to carbon sequestration projects by helping to inform the potential future carbon and biodiversity benefits of restoring disturbed habitats (REDD+). At a time where the use of shifting cultivation is threatened by shifts to larger-scale, commercial agriculture, we show that secondary woodland habitats can retain considerable biodiversity value, and act as carbon sinks.

Crop yield is correlated with honey bee hive density but not in high-woodland landscapes

Honey bees are the most important managed pollinator worldwide and are vital to the success of modern agriculture. Native, wild bees are also important pollinators in both natural and agricultural systems, and are highly sensitive to habitat in the surrounding landscape. Few studies, however, have considered how managed honey bees, and their effectiveness as crop pollinators, may be influenced by variation in the surrounding landscape. If honey bees are influenced by areas outside of the crop fields in which they are placed, their effectiveness as crop pollinators could be diminished. The goal of this study was to determine whether the relationship between honey bee hive density and crop yield varies with the composition of the surrounding landscape. We collected historical (2000–2011) data on yield and honey bee hive stocking density from 38 commercial cranberry growers in central Wisconsin. Using mixed-model regression analyses we found that cranberry yield was strongly, positively correlated with hive density but this effect diminished as the proportion of the surrounding landscape in woodland increased. Thus, at cranberry marshes in low-woodland landscapes (e.g., <42% woodland within 1km), increasing the density of honey bees increased yields by about1000kg/hive, while cranberry marshes in high woodland landscapes saw no effect of adding honey bees. These results suggest that honey bees, like wild bees, are influenced by non-crop areas in the surrounding landscape and that landscape context should be considered when making management recommendations for the use of honey bees for crop pollination.

The relative importance of habitat quality and landscape context for reptiles in regenerating landscapes

Restoration activities are limited by funding and logistics. To optimise restoration efforts, we need to evaluate the effects of management actions on wildlife populations. In general, site-scale habitat quality has a stronger influence on habitat use by fauna than the landscape context. However, this is yet to be empirically tested for reptiles. In this study, we used model averaging and hierarchical partitioning to compare the relative importance of site-scale habitat quality and landscape context for reptile communities and species in a regenerating woodland landscape in semi-arid Queensland, Australia. Reptiles were surveyed at 55 sites. Habitat quality was assessed using relevant variables based on published habitat-associations for each species or group. Landscape context was assessed using binary, mosaic and continuous descriptions of vegetation cover within 250m of the survey sites. We found that, in comparison to site-scale habitat quality, the composition of the surrounding landscape had little influence on reptiles, despite testing three alternative approaches for describing landscape context. Nine out of eleven reptile species and groups responded to variation in habitat quality, whereas just one species responded to variation in landscape context. Species richness, diversity, and abundance were unaffected by landscape context, but were influenced by site-scale structural complexity and vegetation type. Our findings suggest that reptiles, in general, benefit from conservation and restoration activities that focus on improving site-scale habitat quality, with increasing the amount and connectivity of surrounding vegetation of lesser value. This study also highlights the importance of better understanding the drivers of reptile distributions and abundances in dryland landscapes.

Mapping Tree Canopy Cover and Aboveground Biomass in Sudano-Sahelian Woodlands Using Landsat 8 and Random Forest

Accurate and timely maps of tree cover attributes are important tools for environmental research and natural resource management. We evaluate the utility of Landsat 8 for mapping tree canopy cover (TCC) and aboveground biomass (AGB) in a woodland landscape in Burkina Faso. Field data and WorldView-2 imagery were used to assemble the reference dataset. Spectral, texture, and phenology predictor variables were extracted from Landsat 8 imagery and used as input to Random Forest (RF) models. RF models based on multi-temporal and single date imagery were compared to determine the influence of phenology predictor variables. The effect of reducing the number of predictor variables on the RF predictions was also investigated. The model error was assessed using 10-fold cross validation. The most accurate models were created using multi-temporal imagery and variable selection, for both TCC (five predictor variables) and AGB (four predictor variables). The coefficient of determination of predicted versus observed values was 0.77 for TCC (RMSE = 8.9%) and 0.57 for AGB (RMSE = 17.6 tons∙ha−1). This mapping approach is based on freely available Landsat 8 data and relatively simple analytical methods, and is therefore applicable in woodland areas where sufficient reference data are available.

Forest cover change in Miombo Woodlands: modeling land cover of African dry tropical forests with linear spectral mixture analysis

Dry tropical forests are experiencing some of the highest rates of change among the globe's forests. In sub-Saharan Africa, gross (loss, gain) and net changes in dry tropical forest areas are difficult to quantify at sub-national scales because of high spatio-temporal variability in land cover conditions due to vegetation phenology and land use practices. In this project, we developed new, field-validated remote sensing characterizations of dry season surface components to separate forest from non-forest land cover, and assessed forest changes from the 1990s–2010s in a Tanzanian Miombo Woodland landscape. Using a linear spectral mixture analysis (LSMA) approach with Landsat 5–8 data, we examined the hypothesis that higher proportions of substrate and non-photosynthetic vegetation (NPV) at non-forest regions distinguished them from forest cover against seasonally variable land cover conditions. Subsequently we evaluated the efficacy of multi-temporal classification and single-date image thresholding for identifying forest from non-forest cover. We found significantly greater proportions of substrate and NPV over non-forest compared to forest areas that enabled identification of forest cover across dry season images. Single-date, forest/non-forest maps based on an LSMA-derived metric attained overall accuracies of 81.0–85.3%, which approached multi-temporal unsupervised classifications (86.5% for forest/non-forest maps). Applying the LSMA-derived metric to study forest changes, our study region experienced a net 15.0% loss of 1995 forest area, and a 7.0% overall reduction in the total forest-occupied land cover from 1995–2011. Areas of gross forest gain were substantial, totaling 13.6% of the 1995 forest area. We found differing patterns in gross forest losses and gains among sub-regions and through time in our Tabora study area, which provide bases for testable hypotheses in future research on regional and localized drivers affecting forest cover. Our finding that non-green surface components distinguished forest from non-forest via an LSMA approach may be widely applicable to studying forest conversions in Miombo Woodlands and other dry tropical forests. This approach may also be useful for evaluating how land cover conditions change in response to potential land use or climate driving variables, or the impact of land changes for carbon balance and other ecosystem processes.

Gall wasp community response to fragmentation of oak tree species: importance of fragment size and isolated trees

We explore the impact of habitat fragmentation on interactions between keystone resources of forest trees—oaks, genus Quercus (Fagaceae)—and an associated radiation of specialist cynipid gall wasps. Habitat fragmentation is predicted to have bottom‐up impacts on cynipid communities through impacts on host plant quality (plant vigor hypothesis). We explored the bottom‐up impacts on cynipid communities of habitat fragment size, fragment edge effects and presence of isolated oaks. We quantified temporal and spatial variation of leaves produced in the canopy to quantify plant vigor, and surveyed cynipid gall species abundance and richness over three years using 15 permanent forest patches and 25 isolated oaks in a fragmented oak woodland landscape in central Mexico. Cynipid gall abundance and species richness were higher in isolated oaks and small woodland fragments than in larger ones. Cynipid abundance and species richness were also higher along fragment edges in comparison with fragment interiors. This contrasts with patterns observed in other taxa. In addition, host plant quality was higher in isolated trees, in smaller fragments and along fragment edges. We therefore hypothesize that observed patterns in cynipid abundance and species richness are driven by changes in host plant quality due to forest fragmentation. Our data represent a baseline for longer‐term monitoring of fragmentation effects at a landscape scale. Further work is required to explore alternative potential explanations for observed patterns, including the estimation of potential top‐down impacts of fragmentation mediated by natural enemies.

Relationship between spatial heterogeneity and wavelength in multisensor airborne images

Variogram has been utilized to exploring the spatial heterogeneity of remote sensing images, especially its association with spatial resolution. However, very few attentions have been drawn on evaluating the spatial heterogeneity of multisensor airborne imagery and its relationship with spectral wavelength. Therefore, an investigation was carried out on multisensor airborne images to determine the relation between spatial heterogeneity and spectral wavelength for woodland, grass, and urban landscapes by applying variogram modeling. The airborne thematic mapper (ATM), compact airborne spectrographic imager (CASI), and Specim AISA Eagle airborne images at Harwood Forest, Monks wood, Cambridge, and River Frome areas, UK, were utilized. Results revealed that (1) the red band contained greater spatial variability than near-infrared wavelengths and other visible wavebands; (2) there was a steep gradient at the red edge in reference to its spatial variability of multisensor airborne images; (3) only for natural landscape such as woodland and grass, near-infrared waveband contains greater within-scene variations than the blue and green bands; (4) compared with the discrepancy of spatial resolution introduced by multisensor images (ATM, CASI, and Eagle), the specific landscape and spectral bands were more important in determining heterogeneity by means of original visible, near-infrared bands, and normalized difference vegetation index (NDVI). These findings remained us to be caution when combining and interpreting spatial variability and spatial structures derived from airborne images with different spatial resolution and spectral wavelength. Additionally, the outcomes of this study also have considerable implications in terms of designing and choosing suitable images for different applications.

Environment, Society and Landscape in Early Medieval England, by Tom Williamson

Environment, Society and Landscape in Early Medieval England, by Tom Williamson. Woodbridge, The Boydell Press, 2013. viii, 270 pp. $80.00 US (cloth). Tom Williamson tackles a tried-and-true landscape history question in his latest book on early medieval England: why do regional settlement differences appear the way they do? Because of the paucity of written evidence from the period, Williamson blends historical documents, archaeological investigations, and modern landscape configurations to propose some answers to the question. His thesis is that the landscape patterns of the early Saxon settlement, particularly the fifth to eighth centuries, are largely due to environmental factors, rather than cultural or social ones. The first two chapters set up the background material. In chapter one, Williamson gives readers an overview of the historiography of early medieval settlement in England, including how ethnicity, demographics, and social structures have been treated. He is particularly keen to discredit the model, which deals with the breaking up of large estates into smaller and smaller units over time. In the second chapter, Williamson outlines the physical geography of England, including soil, rainfall, bedrock, and drainage basin information. In each of the following chapters Williamson argues against a prevailing settlement theory using environmental variables. Watershed boundaries are more important than military conquest in establishing settlement areas of immigrants (chapter three). Co-axial are the result of resource linkage in topographic contexts rather than evidence of planning (chapter four). The different landholding patterns in east and west, which are usually explained by Viking invasions, are more attributable to climatic factors that created more risk for agricultural production in the west (chapter five). The big issue Williamson wants to address is the supposed differences between champion landscapes of nucleated villages with communal agriculture and areas of individually worked property. This takes up the remainder of the book (chapters six through nine). Williamson takes issue with scholars who portray these types as homogenous landscapes dictated by tenurial or social factors. He believes that the typologies are far too simple since landscapes are variable and depend on local environmental factors. He attacks the dichotomy of champion/woodland landscape on multiple fronts. First, he forcefully argues that woodland landscapes do not indicate late or dispersed settlement. Second, he writes that the prominent theory of nucleation of settlement in the Saxon period is a myth, positing instead that seemingly planned settlements were much more irregular and gradually developed in place. …

Impacts of exotic spider spillover on resident arthropod communities in a natural habitat

1. The spillover of exotic predators from managed ecosystems into natural habitats may exacerbate the biodiversity losses caused by land‐use intensification.2. In the present study, the impacts of the exotic wandering spider Cheiracanthium mildei L. Koch in an oak woodland ecosystem adjacent to an intensively‐managed agricultural system were examined.3. Abundance and species richness of resident spiders and insects in oak branches were reduced in the presence of C. mildei. Contrary to expectations, C. mildei did not disproportionately affect other wandering spider species, but appeared to impact spiders from all tested functional groups. Numbers of herbivorous and predatory insects were also lower in the presence of C. mildei.4. Although the apparent effects of this spider extend to multiple trophic levels in oak woodland, its voracity and relatively large size may ultimately strengthen herbivore suppression in the vineyard–oak woodland landscape.

Habitat and Forage Associations of a Naturally Colonising Insect Pollinator, the Tree Bumblebee Bombus hypnorum

Bumblebees (Bombus species) are major pollinators of commercial crops and wildflowers but factors affecting their abundance, including causes of recent population declines, remain unclear. Investigating the ecology of species with expanding ranges provides a potentially powerful means of elucidating these factors. Such species may also bring novel pollination services to their new ranges. We therefore investigated landscape-scale habitat use and foraging preferences of the Tree Bumblebee, B. hypnorum, a recent natural colonist that has rapidly expanded its range in the UK over the past decade. Counts of B. hypnorum and six other Bombus species were made in March-June 2012 within a mixed landscape in south-eastern Norfolk, UK. The extent of different landscape elements around each transect was quantified at three scales (250 m, 500 m and 1500 m). We then identified the landscape elements that best predicted the density of B. hypnorum and other Bombus species. At the best fitting scale (250 m), B. hypnorum density was significantly positively associated with extent of both urban and woodland cover and significantly negatively associated with extent of oilseed rape cover. This combination of landscape predictors was unique to B. hypnorum. Urban and woodland cover were associated with B. hypnorum density at three and two, respectively, of the three scales studied. Relative to other Bombus species, B. hypnorum exhibited a significantly higher foraging preference for two flowering trees, Crataegus monogyna and Prunus spinosa, and significantly lower preferences for Brassica napus, Glechoma hederacea and Lamium album. Our study provides novel, quantitative support for an association of B. hypnorum with urban and woodland landscape elements. Range expansion in B. hypnorum appears to depend, on exploitation of widespread habitats underutilised by native Bombus species, suggesting B. hypnorum will readily co-exist with these species. These findings suggest that management could target bumblebee species with distinctive habitat requirements to help maintain pollination services.