Escaping the flames: large termitaria as refugia from fire in miombo woodland

At finer scales, spatial heterogeneity can influence fire intensity and severity. To test whether Macrotermes termite mounds act as fire refugia for woody plants, we assessed effects of fire on individual plants, woody plant structure and composition in a miombo woodland in Zimbabwe, where elephants have decreased tree cover, leading to increased grass cover, fuelling greater intensity fires. We compared exposure to fire on 47 paired mound-matrix plots at three sites. Mound-based woody plants were less exposed to fire than those in matrix positions. Woody species composition differed between mound and matrix, and there were more tall trees on mounds. We assessed grass cover, elephant damage, fire damage and resprouting response for all woody plants found on 10 paired mound-matrix plots that had been equally exposed to severe late dry season fires. Grass cover was three times greater for matrix sites, where 85 % of woody species experienced heavy fire damage, compared to 29 % for mounds. Matrix species were nearly 31 times more likely than mound species to exhibit a vigorous resprouting response after fire damage, all else being equal. The distinct composition of termitaria vegetation has been attributed to edaphic factors. To this should be added the fire-retardant properties of mounds, allowing woody species that might otherwise have been excluded, to persist in a fire-prone system. Thus, spatial pattern created by termitaria is reinforced through exclusion of fire, allowing different species composition and structure. Since termitaria are important for productivity and biodiversity, the refuge effect is significant for the system.     

Incidence of competitors and landscape structure as predictors of woodland-dependent birds

Globally, modification of landscapes for agriculture has had a strong influence on the distribution and abundance of biota. In particular, woodland-dependent birds are under threat across agricultural landscapes in Britain, North America and Australia, with their decline and extirpation attributed to the loss and fragmentation of habitat. Other native species have become over-abundant in response to anthropogenic landscape change and have strong interactive effects on avian assemblage structure. In eastern Australia, the hyper-aggressive noisy miner (Manorina melanocephala) often dominates woodlands in agricultural landscapes through interspecific competition, resulting in declines of species richness of woodland-dependent birds. We aimed to determine the relative influence and importance of interspecific competition, in situ habitat structure and landscape structure for woodland-dependent bird species at the landscape level. We recorded species-specific landscape incidence of woodland-dependent birds in 24 agricultural-woodland mosaics (25 km²) in southern Queensland, Australia. We selected extensively cleared landscapes (10–23 % woodland cover) where fragmentation effects are expected to be greatest. We applied generalised linear models and hierarchical partitioning to quantify the relative importance of the landscape-level incidence of the noisy miner, mistletoe abundance, shrub cover, woodland extent, woodland subdivision and land-use intensity for the incidence of 46 species of woodland birds at the landscape-scale. The landscape-level incidence of the noisy miner was the most important explanatory variable across the assemblage. Both in situ habitat structure and landscape structure were of secondary importance to interspecific aggression, although previous research suggests that the increasing incidence of the noisy miner in fragmented agricultural landscapes is itself a consequence of anthropogenic changes to landscape structure. Species’ responses to fragmentation varied from positive to negative, but complex habitat structure had a consistently positive effect, suggesting in situ restoration of degraded habitats could be a conservation priority. Landscape wide conservation of woodland-dependent bird populations in agricultural landscapes may be more effective if direct management of noisy miner populations is employed, given the strong negative influence of this species on the incidence of woodland-dependent birds among landscapes.     

Edge geometry influences patch-level habitat use by an edge specialist in south-eastern Australia

We investigated patterns in habitat use by the noisy miner (Manorina melanocephala) along farmland-woodland edges of large patches of remnant vegetation (>300 ha) in the highly fragmented box-ironbark woodlands and forests of central Victoria, Australia. Noisy miners exclude small birds from their territories, and are considered a significant threat to woodland bird communities in the study region. Seventeen different characteristics of edge habitat were recorded, together with the detection or non-detection of noisy miners along 129 500-m segments of patch edge. Habitat characteristics ranged from patch-level factors related to patch-edge geometry to site-level floristic factors. Backward (stepwise) logistic regression analyses were used to identify habitat characteristics that were associated with the occupancy of a site by noisy miners. After accounting for the effects of spatial autocorrelation on the occurrence of noisy miners along edges, we identified projections of remnant vegetation from the patch edge into the agricultural matrix (e.g., corners of patches, peninsulas of vegetation) and clumps of trees in the agricultural matrix within 100 m of the edge as significant predictors of the occupancy of edges by noisy miners. This relationship was also confirmed in two other geographically and floristically distinct habitats within Victoria. The use of edges with projections by noisy miners may confer advantages in interspecific territorial defence. In light of these results, we advocate revegetation strategies that attempt to enclose projections within 100 m of the edge, with fencing placed out to this new boundary, to reduce the likelihood of colonisation and domination of an edge by noisy miners. Our study highlights the need for greater consideration to be given to the patterns in habitat use by aggressive edge specialists, particularly in relation to patch-edge geometry and other human-induced components of landscapes.     

Effectiveness of corridor vegetation depends on urbanization tolerance of forest birds in central Tokyo,Japan

Vegetation corridors, such as street trees in urban areas, which connect patchy woodland and mitigate habitat isolation, are expected to enhance the persistence of birds in urban landscapes. However, the effectiveness of urban corridors on birds remains equivocal because vegetation corridor is often managed for human use with little consideration of wildlife. Here we compared the effects of three major corridors of varying vegetation structures (trees with a dense understory, trees with a sparse understory, and grassy areas with sparse trees) on the species richness and abundance of birds in 21 wooded patches in the center of Tokyo, Japan, during wintering and breeding seasons. Using generalized linear models and Akaike’s information criterion, we found that the effectiveness of corridors depended on the tolerance of birds to urbanization. Urban avoider species, having low tolerance to urbanization, demonstrated lower species richness and abundance in patches close to the corridor with a sparsely vegetated understory as compared with patches close to the understory-richer corridors during winter, although such an effect disappeared during the breeding season. The corridors did not have a significant effect on suburban adapter species with a high tolerance to urbanization. Our results suggest that corridors with scarce understory vegetation may limit the persistence of birds avoiding urban areas.     

Overwintering in a megacity: Urban green areas and migratory birds in Mexico City

Nearctic-Neotropical migratory birds are threatened by land-use change throughout their complex annual cycles. While urbanization is an essential driver of land-use change, it is unclear how it affects migrant birds. Although migratory birds are more diverse in non-urban patches of native vegetation than in urban areas, neotropical cities can host diverse assemblages of overwintering migrant birds. Migratory birds in neotropical cities tend to be closely associated with urban green areas (UGAs). However, how their presence and abundance are affected by the habitat elements of UGAs and the urban matrix of neotropical cities is poorly understood. In this study, we compared the migratory bird species richness and abundances among UGAs and the urban matrix of the southern section of the megacity of Mexico City and native vegetation sites outside the city. Our results show that UGAs in neotropical cities provide habitats capable of maintaining complex overwintering migratory bird assemblages with local trees as critical features. We also assess the role that UGAs' characteristics play in determining migrant bird assemblages. We conducted bird censuses and measured habitat traits to determine how migrant bird assemblages are related to the habitat features of our study sites. We measured local, buffer, and spatial habitat features of each UGA. We found 23 overwintering migrant species in the three habitats, with 22 present within UGAs. Both UGAs and urban matrix sites had higher estimated species richness of migrant birds than non-urban native vegetation sites located outside the city. Only local features of UGAs affected migrant birds. While tree abundance in UGAs was positively associated with migratory bird species richness, the proportion of tree coverage was positively related to bird abundance. Our results show that UGAs in neotropical cities can maintain complex overwintering migratory bird assemblages, with trees being the most critical habitat feature. As a result, UGA management focused on maintaining trees and increasing their numbers can improve habitat conditions for migratory birds overwintering in neotropical cities.     

Patterns of bird predation on reptiles in small woodland remnant edges in peri-urban north-western Sydney, Australia

The predator–prey relationship plays an integral role in community structure. In the presence of habitat fragmentation, the dynamic interaction among co-existing species may be disrupted. In this paper we investigated the interaction between small skinks resident in open woodland remnants and the predatory birds that cross-forage between the remnants and the surrounding peri-urban matrix. Skinks were found in significantly fewer numbers in the edge of remnants compared to their core. In contrast, predatory birds were in largest numbers at the edge compared to the core of remnants. We found that there was a strong negative correlation between skink numbers and predatory birds (individually and combined) consistent with higher predation pressure in the edge compared to the core of remnants. Strike rates on decoys that mimicked skinks were also higher in the edge compared to core habitats, consistent with higher predation rates in this edge habitat.     

Geometry of Large Woodland Remnants and its Influence on Avifaunal Distributions

In fragmented landscapes, remnant vegetation almost always occurs as irregular shapes and frequently with peninsulas or lobes of habitat extending into the surrounding agricultural matrix. Historical time-series of many landscapes indicate that such lobes tend to be lost through time, making remnants more regularly shaped as more habitat is lost. Although the biogeographic peninsular effect suggests that the biodiversity value of lobes should be less than remnant interiors, R.T.T. Forman has suggested that lobes in fragmented, human-dominated landscapes may provide positive ecological functions. We considered the distribution and occurrence of birds in medium-sized (ca. 2000 ha) remnants of the box-ironbark forests of central Victoria, Australia. We compared transects placed in the interiors, along edges and in lobes, finding that in general woodland-dependent species occurred throughout lobes and edges in densities substantially greater than the interiors of the remnants (often ca. 2 km from edges). We conducted analyses that weighted speciesȁ9 predilections to occupy the centres of large woodland areas using independent data. We found that: (1) species favouring centres of large woodland areas (measured using independent data) were distributed evenly throughout our study remnants; and (2) species capable of occupying smaller remnants (≤80 ha) were more prevalent in lobes and along the straight edges of remnants. These results indicate that preservation of lobes is likely to be important for maintaining avian biodiversity in fragmented landscapes, and that the addition of lobes in reconstructing landscapes through revegetation may favour birds.     

Landscape composition influences roe deer habitat selection at both home range and landscape scales

Understanding how patterns of habitat selection vary in relation to landscape structure is essential to predict ecological responses of species to global change and inform management. We investigated behavioural plasticity in habitat selection of roe deer (Capreolus capreolus) in relation to variable habitat availability across a heterogeneous agricultural landscape at the home range and landscape scales. As expected, woodland was heavily selected, but we found no functional response for this habitat, i.e. no shift in habitat selection with changing habitat availability, possibly due to the presence of hedgerows which were increasingly selected as woodlands were less abundant. Hedgerows may thus function as a substitutable habitat for woodlands by providing roe deer with similar resources. We observed a functional response in the use of hedgerows, implying some degree of landscape complementation between hedgerows and open habitats, which may in part compensate for lower woodland availability. We also expected selection for woodland to be highest at the wider spatial scale, especially when this habitat was limiting. However, our results did not support this hypothesis, but rather indicated a marked influence of habitat composition, as both the availability and distribution of resources conditioned habitat selection. There was no marked between-sex difference in the pattern of habitat selection at either scale or between seasons at the landscape scale, however, within the home range, selection did differ between seasons. We conclude that landscape structure has a marked impact on roe deer habitat selection in agricultural landscapes through processes such as landscape complementation and supplementation.     

Landscape structure and breeding bird distribution in a sub-Mediterranean agro-ecosystem

Richness, abundance and distribution of birds were investigated in the Aulella watershed,a mountainous area of 300 km², located in the extreme northwestern corner of Tuscany, Italy in spring and summer, 1995. The study area encompasses five vegetation types (from Mediterranean maqui to upland beech forest) and three main land use categories (woodlands, mixed cultivated + urban areas, montane prairies). The recent history of land abandonment in the study area has produced a rapid expansion of shrubland and woodland, reducing cultivated areas to small patches interspersed in a woodland matrix. Richness, abundance and distribution of birds recorded at 414 points, randomly selected along secondary roads, and located using a Global Positioning System (GPS), were compared with topography, vegetation type and land use in a Geographic Information Systems (GIS) with a grid cell resolution of 200 × 200 m. Bird richness (55 species in all) and abundance are correlated: (a) negatively with the increasing altitude and increasing distance from cultivated areas; (b) positively with the increasing distance from woodlands and mountain prairies. Slope orientation appears to have a negligible effect on bird assemblages. Bird richness and abundance are significantly correlated with vegetation type. Cultivated areas support the highest bird richness and abundance that increase with patch size of the cultivated areas. Local extinction and/or reduction in within-species abundance of birds are expected to continue if the process of land abandonment continues. This revised version was published online in July 2006 with corrections to the Cover Date.     

Distribution of the red imported fire ant,shape Solenopsis invicta,in road and powerline habitats

For early-successional species, road and powerline cuts through forests provide refugia and source populations for invading adjacent forest gaps. Within an 800 km² forest matrix in South Carolina, we determined if width, disturbance frequency or linear features of road and powerline cuts influenced the mound distribution of the red imported fire ant, Solenopsis invicta Buren. For each of five linear habitat types, differing in width and disturbance frequency, we mapped all mounds located within ten 500 m segments. Mean mound density was lowest in narrow, infrequently-disturbed closed-canopy dirt road habitats (8.8 mounds/ha). For types with an opening in the forest canopy (i.e., open dirt road, gravel road, paved road and powerline cut), mean mound density was highest in narrow habitats where disturbance was intermediate (open dirt roads, 86.5 mounds/ha). It was lowest in wide habitats where disturbance was infrequent (powerline cuts, 27.6 mounds/ha). Mean mound size was greater in infrequently-disturbed powerline cuts than in frequently-disturbed paved roads. Mounds were located significantly closer to road or forest edges than expected by random. In all types except dirt roads, mounds were more common toward northern edges, and more so as the orientation of the linear habitat changed from north/south to east/west. These data suggest that narrow, disturbed habitats are more suitable for fire ant establishment and success than wider ones, and that the distribution of fire ants in linear habitats is not as uniform as it has been shown to be in pastures. A decrease in roadside disturbance and an increase in shade, especially along the northern edge, may result in lower fire ant mound density in these linear habitats.     

Species richness and ecosystem services of tree assemblages along an urbanisation gradient in a tropical mega-city: Consequences for urban design

We assess how tree species richness and ecosystem services vary along a tropical urbanisation gradient in a rapidly expanding mega-city (Bangkok, Thailand). We conduct tree surveys in 150 1 km cells selected by random stratification across an impervious surface cover gradient. In each cell, surveys were conducted at the centre (representing typical conditions) and in the largest patch of trees (assessing woodland retention impacts). We estimated trees’ contributions to i) carbon storage, ii) food production for people, iii) biodiversity support (production of food for frugivorous birds), and iv) economic value (assessed using regulations for using trees as collateral for financial loans). Surveys detected 162 species (99 natives) indicating substantial species loss relative to nearby natural forests. Despite this, and contrasting with typical patterns in temperate cities, tree species richness (including of natives) and ecosystem service provision is relatively stable across the urbanisation gradient. This finding has two important consequences. First, growing cities through high intensity developments that require less space may benefit regional biodiversity without compromising ecosystem services. Second, even the typically very small woodlands present in highly urbanised locations contribute to supporting biodiversity and providing ecosystem services; thus such woodlands require protection. Species richness is not strongly positively associated with most of our focal ecosystem services. Urban planners must therefore pay attention to both biodiversity and ecosystem services as these do not automatically accrue from each other, partly because non-native species contributed substantially to most ecosystem services except biodiversity support. Finally, trees provide substantial value as collateral for financial loans (averages of £643 ha at random locations and £2282 ha in wooded locations). Policies promoting such valuations may reduce tree removal and encourage tree planting, but the list of eligible species warrants revision to include additional species that enhance biodiversity support, ecosystem services, and resilience against future environmental instability.     

Matrix effects on plant-frugivore and plant-predator interactions in forest fragments

Structural features of both habitat remnants and surrounding matrix can be important for explaining plant population dynamics and ecosystem functions in human-impacted landscapes. However, little is known about how the structural features of the adjacent matrix affect biotic interactions and whether such context effects are subject to temporal variations. Using the hawthorn Crataegus monogyna in northern Spain, we studied matrix effects on two sequential plant-animal interactions, frugivory by birds and postdispersal seed predation by rodents. Using Hierarchical Linear Models, we compared the magnitude of both interactions on trees located in two patch types that strongly differed in structural features of the adjacent matrix habitat: patches totally surrounded by a degraded, structurally contrasted pastures (unconnected patches), and trees growing in patches adjacent to a lowly degraded, structurally similar mature forests (connected patches). We compared outcomes for 2005 and 2006, which were years with strong differences in community-wide fruit and seed abundance. Frugivory rate did not differ between patch types in either year, likely related to high mobility of birds. Seed predation rates were higher in unconnected patches than in connected ones, but only in 2005. We conclude that strong interannual fluctuations in resource availability are not rare in temperate systems and that recruitment rates could be frequently reduced within unconnected patches, thus collapsing plant regeneration processes of hawthorn populations. Overall, our results suggest that generalizations about potential effects of the matrix on plant-animal interactions within remnant patches must consider: (1) species-specific habitat responses of the organisms, (2) suitability of neighbouring habitats in terms of food supply, and (3) temporal variations in plant-resource availability for interacting animals.     

Combined effects of area,connectivity, history and structural heterogeneity of woodlands on the species richness of hoverflies (Diptera: Syrphidae)

Context

Hoverflies are often used as bio-indicators for ecosystem conservation, but only few studies have actually investigated the key factors explaining their richness in woodlands.

Objectives

In a fragmented landscape in southwest France, we investigated the joint effects of woodland area, structural heterogeneity, connectivity and history on the species richness of forest-specialist hoverflies, and whether there was a time lag in the response of hoverflies to habitat changes, and tested the effect of spatiotemporal changes.

Methods

Current species richness was sampled in 48 woodlands using 99 Malaise traps. Structural variables were derived from a rapid habitat assessment protocol. Old maps and aerial photographs were used to extract past and present spatial patterns of the woodlands since 1850. Relationships between species richness and explanatory variables were explored using generalized linear models.

Results

We show that current habitat area, connectivity, historical continuity and the average density of tree-microhabitats explained 35 % of variation in species richness. Species richness was affected differently by changes in patch area between 1979 and 2010, depending on woodland connectivity. In isolated woodlands, extinction debt and colonization credit were revealed, showing that even several decades are not sufficient for hoverflies to adapt to landscape-scale habitat conditions.

Conclusions

These findings emphasise the importance of maintaining connectedness between woodlands, which facilitates the dispersion in a changing landscape. Our results also highlight the benefits of using a change-oriented approach to explain the current distribution patterns of species, especially when several spatial processes act jointly.

     

Multi-scale site and landscape effects on the vulnerable superb parrot of south-eastern Australia during the breeding season

The threatened superb parrot of south-eastern Australia exemplifies many of the challenges associated with research on wide-raging organisms which live ‘off-reserve’. Challenges include that most land is privately owned and that landscape use by such organisms does not always conform to traditional schematic and categorical landscape/fragmentation models. A multi-scale approach for embedding the detection of site-level and landscape context effects into landscape sampling design and subsequent statistical analysis is presented. The superb parrot was found scattered at varying densities throughout the agricultural landscapes of the South-West Slopes, much of which was privately owned. It responded to site-level variables and the surrounding landscape context. Overall, the superb parrot favoured lower elevation sites which were dominated by scattered, open woodlands, where Blakely’s red gum was a significant component. Mean plant productivity within 2 km, levels of woody tree cover within 3 km and (with caveats) length of roads within 3 km had a major effect on site-level response, indicating conditions in the surrounding local landscape are important to the superb parrot. This multi-scale response requires a multi-scale conservation and restoration strategy. The importance of open tree cover and amounts of Blakely’s red gum are a matter for concern, due to a general lack of tree regeneration and the particular susceptibility of Blakely’s red gum to dieback. The scattered trees in the agricultural matrix were important to the superb parrot, suggesting that it views these landscapes as a continuum of usable habitat. Strategies for restoration of larger habitat remnants should also include regeneration of trees in scattered pattern in the wider landscape, and Blakely’s red gum should be part of any strategy along with other key species such as yellow and white box. The landscape sampling approach successfully addressed the challenges of whole-landscape research. This highlights the value of ‘off-reserve’ studies across whole landscapes.     

Openness as a key-variable for analysis of management trade-offs in urban woodlands

There is currently increasing pressure on urban woodland in industrialised countries. Management of such areas is shifting towards multiple-use with focus on both recreation and biodiversity conservation. We examined the concept of “openness” as part of a possible tool for planners and decision makers. Our field studies were conducted in oak-dominated urban woodlands in southern Sweden with the focus on understory density. In a field experiment we found that understory density was greatly influenced by management, but effects appeared to be site-dependent. Photographs from the field sites were shown to panels of students to analyse recreational preferences in relation to openness. The photographs showed similar woodland types but with different understory density, although the quantification of this variation was not revealed to the participants. In general, open forests were considered most attractive for recreation but 74% of the respondents claimed that they preferred a mix of open and closed forest. Frequent forest visitors preferred relatively closed forests but infrequent visitors liked more open forests. As an example of management effects on biodiversity, we examined the density and diversity of woodland birds in relation to the management. We found that bird densities decreased in the plots with extensive removal of understory. We suggest that variables related to openness can be used in the planning process, especially at fine-grained scales, to analyse different management options and make trade-offs between interests in multiple-use woodland sites.     

Modeling fire and landform influences on the distribution of old-growth pinyon-juniper woodland

Expansion of Pinus and Juniperus species into shrub steppe in semi-arid regions of the western United States has been widely documented and attributed in part to fire exclusion. If decreased fire frequency has been an important cause of woodland expansion, one would expect to find age structures dominated by younger trees on more fire-prone sites, with old-growth pinyon-juniper woodland limited to sites with lower fire risk. We compared current old-growth distribution with spatial models for fire risk in a 19-km² watershed in central Nevada, USA. Multiple GIS models were developed to represent fire susceptibility, according to abiotic factors representing fuels and topographic barriers to fire spread. We also developed cellular automata models to generate fire susceptibility surfaces that additionally account for neighborhood effects. Rule-based GIS models failed to predict old-growth distribution better than random models. Cellular automata models incorporating spatial heterogeneity of site productivity predicted old-growth distribution better than random models but with low accuracy, ranging from 58% agreement at the single-pixel (0.09-ha) scale to 80% agreement for 20-pixel neighborhoods. The best statistical model for predicting old-growth occurrence included the negative effect of topographic convergence index (local wetness), and the positive effects of solar insolation and proximity to rock outcrops. Results support the hypothesis that old-growth woodlands in the Great Basin are more likely to occur on sites with low fire risk. However, weak relationships suggest that old-growth woodlands have not been confined to fire-safe sites. Conservation efforts should consider the landscape context of old-growth woodlands across a broad landscape, with an emphasis on conserving landscape variability in tree age structure.     

Rural depopulation and recent landscape changes in a Mediterranean region: Consequences to the breeding avifauna

We studied the vegetational and avifaunistic changes following rural depopulation in an area covering 2,600 ha north of Montpellier (Southern France). The study area is covered by a mosaic of Mediterranean habitats that includes cultivation, grasslands, shrublands, and woodlands and is representative of the natural features present and of the human usage practiced so far in this part of the Mediterranean. We sampled the vegetation and the bird fauna in the same 193 census plots in 1978 and in 1992. At both the habitat and landscape scales the cover of woody plants increased significantly. Open habitats tend to disappear. As a consequence the abundance of open-habitat bird species decreased significantly whereas the abundance of forest birds increased significantly. These changes favor a pool of forest species widespread in western Europe and reduce habitat availability for open habitat and shrubland species. Many of the latter are Mediterranean species whose distribution in Western Europe could become reduced under current landscape dynamics. Our observation of more woodlands and their typical birds and of less open habitats and their associated avifauna is not consistent with the traditional worry shown by the public and the managers about the regression of forests and woodlands in the Northern Mediterranean as a consequence of fire.     

Changes over time in tree cavity availability across urban habitats

In urban ecosystems, tree cavities provide critical habitat for a variety of wildlife, and their occurrence is influenced by tree health, management, and cavity excavators. Changes over time in vegetative structure, human use patterns, and built environment affect the formation and persistence of tree cavities, and these changes may differ in various urban habitats. Trees with some decay are often associated with tree cavities, however, parks and residential habitats which are highly managed often lack highly-decayed trees, and large trees which are dead and damaged are likely to be removed and replaced with saplings. We surveyed changes over seven years (in 2013 and 2020) in the abundance of both excavated woodpecker cavities and decay cavities, in three urban habitats (forest, park, and residential) in the Chicago region, IL, USA. We observed greater stability of cavity abundance in managed park and residential habitats over time. Low numbers of highly-decayed trees in park and residential habitats were associated with reduced excavated cavity presence compared to forests. As expected, in both 2013 and 2020, the probability of cavity presence for both excavated and decay cavities was increased with greater tree size and higher levels of tree decay, though the patterns of this association varied between habitat types and years. The continued replacement and maintenance of existing trees means that managed park and residential habitats were more stable than unmanaged forest remnants, which are vulnerable to large changes in tree characteristics which could foster unpredictable booms or busts in cavity supply. A stable inventory of tree-cavities depends on preserving large trees, and decay of urban trees benefits habitat quality for cavity-nesters. Pruning of branches or removal of dead trees curtails the life-cycle of tree cavities in decayed branches, so that more highly managed habitats contain fewer cavities than the number of trees could potentially support. Cavity abundance could be improved in stable habitats through reduced intervention where safe, allowing cavity development to occur in situ.     

The compositional and configurational heterogeneity of matrix habitats shape woodland carabid communities in wooded-agricultural landscapes

Context

Landscape heterogeneity (the composition and configuration of matrix habitats) plays a major role in shaping species communities in wooded-agricultural landscapes. However, few studies consider the influence of different types of semi-natural and linear habitats in the matrix, despite their known ecological value for biodiversity.

Objective

To investigate the importance of the composition and configuration of matrix habitats for woodland carabid communities and identify whether specific landscape features can help to maintain long-term populations in wooded-agricultural environments.

Methods

Carabids were sampled from woodlands in 36 tetrads of 4 km² across southern Britain. Landscape heterogeneity including an innovative representation of linear habitats was quantified for each tetrad. Carabid community response was analysed using ordination methods combined with variation partitioning and additional response trait analyses.

Results

Woodland carabid community response was trait-specific and better explained by simultaneously considering the composition and configuration of matrix habitats. Semi-natural and linear features provided significant refuge habitat and functional connectivity. Mature hedgerows were essential for slow-dispersing carabids in fragmented landscapes. Species commonly associated with heathland were correlated with inland water and woodland patches despite widespread heathland conversion to agricultural land, suggesting that species may persist for some decades when elements representative of the original habitat are retained following landscape modification.

Conclusions

Semi-natural and linear habitats have high biodiversity value. Landowners should identify features that can provide additional resources or functional connectivity for species relative to other habitat types in the landscape matrix. Agri-environment options should consider landscape heterogeneity to identify the most efficacious changes for biodiversity.