Passive brigalow (Acacia harpophylla) woodland regeneration fails to recover floristic composition in an agricultural landscape

Regrowth (secondary) vegetation is increasingly seen as an important conservation alternative where there is inadequate cover of intact remnant, and more recently, the focus of potential biodiversity offsets. However, little is known of the functioning and dynamics of regrowth in comparison to remnant vegetation. This research tests whether the floristic composition and stand structure of brigalow (Acacia harpophylla) regrowth woodlands return to that of endangered brigalow remnant woodlands and the relationships of patterns in composition and structure to environmental drivers in the agricultural landscape of southern Queensland, Australia. Thirty‐eight sites were sampled for species composition (frequency), stand structure (foliage projected cover of strata) and environmental variables (spatial/patch characteristics), encompassing ungrazed and grazed old‐growth brigalow remnants and different aged brigalow regrowth (<20, 20–30, 30–40, >40 years since clearing). There was no difference in structure observed between grazed remnant and older regrowth (>40 years); however, ungrazed old‐growth remnants were structurally different to older regrowth. Ungrazed and grazed old‐growth remnants were compositionally different to all regrowth woodlands. The proportion of surrounding vegetation, land‐use type, patch grazing intensity and soil properties were highly correlated with patterns in composition and stand structure observed across the brigalow woodlands. While the stand structure of brigalow regrowth returns to that of remnant brigalow, the distinct floristic species composition of older regrowth may indicate a longer time period is needed for equivalence or a possible alternate stable state in these highly modified agricultural landscapes. To ensure the long‐term persistence of brigalow communities, further investigation of the development trajectory of brigalow regrowth is required; however, it is critical that intact brigalow remnant vegetation remains a priority for conservation strategy and policy.     

How widespread is woody plant encroachment in temperate Australia? Changes in woody vegetation cover in lowland woodland and coastal ecosystems in Victoria from 1989 to 2005

Aim Encroachment or densification by woody plants affects natural ecosystems around the world. Many studies have reported encroachment in temperate Australia, particularly in coastal ecosystems and grassy woodlands. However, the degree to which published studies reflect broad-scale changes is unknown because most studies intentionally sampled areas with conspicuous densification. We aimed to estimate changes in woody vegetation cover within lowland grassy woodland and coastal ecosystems in Victoria from 1989 to 2005 to determine whether published reports of recent encroachment are representative of broad-scale ecosystem changes. Location All lowland grassy woodland and coastal ecosystems (c. 6.11 × 10⁵ ha) in Victoria, Australia. Four major ecosystems were analysed: Plains woodlands, Herb-rich woodlands, Riverine woodlands and Coastal vegetation. Methods Changes in woody vegetation cover from 1989 to 2005 were assessed based on state-wide vegetation maps and Landsat analyses of woody vegetation cover conducted by the Australian Greenhouse Office’s National Carbon Accounting System. The results show changes in woody cover within mapped patches of native vegetation, rather than changes in the extent of woody vegetation resulting from clearing and revegetation. Results When pooled across all ecosystems, woody vegetation increased by 18,730 ha from 1989 to 2005. Woody cover within Riverine woodlands and within Plains woodlands each increased by >7000 ha. At the patch scale, the mean percentage cover of woody vegetation in each polygon increased by >5% in all four ecosystems: Riverine woodlands (+9.2% on average), Herb-rich woodlands (+7.6%), Plains woodlands (+6.7%) and Coastal vegetation (+5.9%). Regression models relating degree of encroachment to geographic and climatic variables were extremely weak (r² ≤ 0.026), indicating that most variation occurred at local scales rather than across broad geographic gradients. Main conclusions At the scale of observation, woody vegetation cover increased in all lowland woodland and coastal ecosystems over the 16-year period. Thus, published examples of encroachment in selected coastal and woodland patches do appear to reflect widespread increases in woody vegetation cover in these ecosystems. This densification appears to be associated with changes in land management rather than with post-fire vegetation recovery and is likely to be ongoing and long-lasting, with substantial implications for biodiversity conservation and ecosystem services.     

Habitat selection and ranges of tolerance: how do species differ beyond critical thresholds?

Sensitivity to habitat fragmentation often has been examined in terms of thresholds in landscape composition at which a species is likely to occur. Observed thresholds often have been low or absent, however, leaving much unexplained about habitat selection beyond initial thresholds of occurrence, even for species with strong habitat preferences. We examined responses to varying amounts of tree cover, a widely influential measure of habitat loss, for 40 woodland bird species in a mixed woodland/grassland landscape in eastern North Dakota, USA. We used LOESS smoothing to describe incidence for each species at three scales: within 200, 400, and 1200 m around sample locations. For the 200‐m scale, we also calculated the most‐preferred range of tree cover (within which at least half of observations were predicted to occur) for each species. Only 10 of 40 species had occurrence thresholds greater than about 10% tree cover. After initial occurrence, species showed three general patterns: some increased monotonically with tree cover; some increased up to an asymptote; some peaked at intermediate amounts of tree cover and then declined. These patterns approximate selection for interior woodlands and for edge‐rich environments, but incidence plots provide greater detail in landscape‐scale selection than do those categories. For most species, patterns persisted at larger scales, but for some, larger scales had distinctly different patterns than local scales. Preferred ranges of tree cover varied from <20% tree cover (common grackle, Quiscalus quiscula) to >60% (veery, Catharus fuscescens). We conclude that incidence patterns provide more information on habitat selection than do threshold measures for most species: in particular, they differentiate species preferring concentrated woodlands from those preferring mixed landscapes, and they show contrasting degrees of selectiveness. [Correction added on 16 October 2012, after first online publication: the Abstract section has been reworded].     

Habitat attribute similarities reduce impacts of land‐use conversion on seed removal

Changes in land use strongly influence habitat attributes (e.g., herbaceous ground cover and tree richness) and can consequently affect ecological functions. Most studies have focused on the response of these ecological functions to land‐use changes within only a single vegetation type. These studies have often focused solely on agricultural conversion of forests, making it nearly impossible to draw general conclusions across other vegetation types or with other land‐use changes (e.g., afforestation). We examined the consequences of agricultural conversion for seed removal by ants in native grassland, savanna, and savanna‐forest habitats that had been transformed to planted pastures (Brachiaria decumbens) and tree plantations (Eucalyptus spp.) and explored if changes in seed removal were correlated with differences in habitat attributes between habitat types. We found that land‐use changes affected seed removal across the tree cover gradient and that the magnitude of impact was influenced by similarity in habitat attributes between native and converted habitats, being greater where there was afforestation (Eucalyptus spp in grassland and savanna). Herbaceous ground cover, soil hardness, and tree richness were the most important habitat attributes that correlated with differences in seed removal. Our results reveal that the magnitude of impact of land‐use changes on seed removal varies depending on native vegetation type and is associated with the type of habitat attribute change. Our findings have implications for biodiversity in tropical grassy systems: afforestation can have a greater detrimental impact on ecological function than tree loss.     

GIS interpolations of witness tree records (1839–1866) for northern Wisconsin at multiple scales

To construct forest landscape of pre‐European settlement periods, we developed a GIS interpolation approach to convert witness tree records of the U.S. General Land Office (GLO) survey from point to polygon data, which better described continuously distributed vegetation. The witness tree records (1839–1866) were processed for a 3‐million ha landscape in northern Wisconsin, U.S.A. at different scales. We provided implications of processing results at each scale. Compared with traditional GLO mapping that has fixed mapping scales and generalized classifications, our approach allows presettlement forest landscapes to be analysed at the individual species level and reconstructed under various classifications. We calculated vegetation indices including relative density, dominance, and importance value for each species, and quantitatively described the possible outcomes when GLO records are analysed at three different scales (resolution). The 1 × 1‐section resolution preserved spatial information but derived the most conservative estimates of species distributions measured in percentage area, which increased at coarser resolutions. Such increases under the 2 × 2‐section resolution were in the order of three to four times for the least common species, two to three times for the medium to most common species, and one to two times for the most common or highly contagious species. We mapped the distributions of hemlock and sugar maple from the pre‐European settlement period based on their witness tree locations and reconstructed presettlement forest landscapes based on species importance values derived for all species. The results provide a unique basis to further study land cover changes occurring after European settlement.     

Restoration of tree lines in an agricultural landscape: their effectiveness as a conservation management tool

As remnant vegetation covers <15% of the Australian sheep‐wheat belt, it is important to identify conservation strategies suitable for use in agricultural landscapes. Tree lines are widespread ecological structures in rural areas, and are now the subject of government subsidy schemes in New South Wales. However, the contribution of tree lines to biodiversity conservation is poorly understood. To identify the conservation value of tree lines, the bird communities in 36 tree lines in Cowra Shire, New South Wales, were surveyed 4 times each. The results demonstrated that tree lines were used by a large number of species, six of which were threatened. Different taxa were associated with different physical tree line attributes, with tree line age an important predictor of species occurrence. While mature tree lines tended to support more species, as was reflected in higher Shannon Diversity Index scores, they also harboured relatively more introduced species and nest predators, while young tree lines provided the best habitat for threatened species. However, these tree lines will mature, and as they do so they will provide increasingly suitable habitat for the hyperaggressive native honeyeater, the Noisy Miner (Manorina melanocephala), and introduced species. Therefore, tree lines in agricultural landscapes may only be serving an important role for conservation on short time scales, and the suite of threatened species young tree lines currently support appear likely to decline further in the future.     

Yellow‐throated miners Manorina flavigula homogenize bird communities across intact and fragmented landscapes

In Australia, the role of noisy miners Manorina melanocephala in biotic homogenization of the avifauna has been well established in modified landscapes, and is listed as a threatening process under national conservation legislation. However, less is known about the effect of the congeneric and more widely distributed yellow‐throated miner, M. flavigula. In this paper we investigate the relative roles of habitat loss and increased dominance by the yellow‐throated miner in avian homogenization and species functional group decline. We examined bird community data collected from 368 woodland sites across three bioregions. For each site there was a local and a landscape scale measure of remnant vegetation cover. We used both multivariate and regression analysis to test the relative influence of yellow‐throated miner abundance and vegetation on bird community composition. There was clear compositional change and homogenization of the avifauna where yellow‐throated miners were present and vegetation cover was low. The abundance of 40 bird species was predicted by combinations of vegetation cover or yellow‐throated miner abundance, and 31 of these regressions included the term yellow‐throated miner. Of these, there was a negative relationship with 23 species, and 19 of these were insectivores or nectarivores. We postulate that the combination of clearing and yellow‐throated miner abundance can interact to disrupt the ecological function of woodlands, by the depletion of insect‐ and nectar‐feeding species and the disturbance to mixed feeding flocks. We propose future research objectives that include a continental‐scale analysis of the determinants of yellow‐throated miner overabundance, the numerical and geographical thresholds of their potential impacts, and the ecological consequences on both avifauna and the woodlands they inhabit.     

Woodland recovery following drought‐induced tree mortality across an environmental stress gradient

Recent droughts and increasing temperatures have resulted in extensive tree mortality across the globe. Understanding the environmental controls on tree regeneration following these drought events will allow for better predictions of how these ecosystems may shift under a warmer, drier climate. Within the widely distributed piñon–juniper woodlands of the southwestern USA, a multiyear drought in 2002–2004 resulted in extensive adult piñon mortality and shifted adult woodland composition to a juniper‐dominated, more savannah‐type ecosystem. Here, we used pre‐ (1998–2001) and 10‐year post‐ (2014) drought stand structure data of individually mapped trees at 42 sites to assess the effects of this drought on tree regeneration across a gradient of environmental stress. We found declines in piñon juvenile densities since the multiyear drought due to limited new recruitment and high (>50%) juvenile mortality. This is in contrast to juniper juvenile densities, which increased over this time period. Across the landscape, piñon recruitment was positively associated with live adult piñon densities and soil available water capacity, likely due to their respective effects on seed and water availability. Juvenile piñon survival was strongly facilitated by certain types of nurse trees and shrubs. These nurse plants also moderated the effects of environmental stress on piñon survival: Survival of interspace piñon juveniles was positively associated with soil available water capacity, whereas survival of nursed piñon juveniles was negatively associated with perennial grass cover. Thus, nurse plants had a greater facilitative effect on survival at sites with higher soil available water capacity and perennial grass cover. Notably, mean annual climatic water deficit and elevation were not associated with piñon recruitment or survival across the landscape. Our findings reveal a clear shift in successional trajectories toward a more juniper‐dominated woodland and highlight the importance of incorporating biotic interactions and soil properties into species distribution modeling approaches.     

The value of paddock trees for regional conservation in an agricultural landscape

Summary Isolated trees and small patches of trees – paddock trees – are a prominent feature of agricultural landscapes in Australia, but are declining in many areas due to natural senescence, clearing, dieback and the general absence of recruitment. We assessed the importance of paddock trees for woodland conservation in a 30 000 ha sample of the New South Wales (NSW) South‐west Slopes using Satellite Pour l’Observation de la Terre (SPOT) panchromatic satellite imagery combined with models predicting the original distribution of vegetation communities. Tree‐cover occurred over 12% of the study area. The patch‐size distribution of vegetation in the study area varied between woodland types. For woodland communities that were confined to hills and ridges, most tree‐cover occurred as few, large remnants. For woodland communities of the foothills and plains (Blakely's Red Gum, Eucalyptus blakelyi and Yellow Box, Eucalyptus melliodora, or White Box, Eucalyptus albens and Red Stringybark), 54% of remnant tree‐cover occurred as patches < 1 ha. The loss of paddock trees will cause substantial reductions to some woodland communities. For example, the loss of patches < 1 ha in woodlands dominated by Blakely's Red Gum and Yellow Box would reduce this association from 7.4% to 3.4% of its predicted pre‐1750 distribution. Mean distance to tree‐cover across the study area increased almost fourfold if patches < 1 ha were removed from the landscape, which may have consequences for movements of some flora and fauna. Failure to protect and perpetuate paddock trees will diminish the likelihood of achieving the conservation objectives of comprehensiveness, adequacy and representativeness in agricultural landscapes.     

Influence of fire history on small mammal distributions: insights from a 100‐year post‐fire chronosequence

Aim Fire affects the structure and dynamics of ecosystems world‐wide, over long time periods (decades and centuries) and at large spatial scales (landscapes and regions). A pressing challenge for ecologists is to develop models that explain and predict faunal responses to fire at broad temporal and spatial scales. We used a 105‐year post‐fire chronosequence to investigate small mammal responses to fire across an extensive area of ‘tree mallee’ (i.e. vegetation characterized by small multi‐stemmed eucalypts). Location The Murray Mallee region (104,000 km²) of semi‐arid Australia. Methods First, we surveyed small mammals at 260 sites and explored the fire responses of four species using nonlinear regression models. Second, we assessed the predictive accuracy of models using cross‐validation and by testing with independent data. Third, we examined our results in relation to an influential model of animal succession, the habitat accommodation model. Results Two of four study species showed a clear response to fire history. The distribution of the Mallee Ningaui Ningaui yvonneae, a carnivorous marsupial, was strongly associated with mature vegetation characterized by its cover of hummock grass. The occurrence of breeding females was predicted to increase up to 40–105 years post‐fire, highlighting the extensive time periods over which small mammal populations may be affected by fire. Evaluation of models for N. yvonneae demonstrated that accurate predictions of species occurrence can be made from fire history and vegetation data, across large geographical areas. The introduced House Mouse Mus domesticus was the only species positively associated with recently burnt vegetation. Main conclusions Understanding the impact of fire over long time periods will benefit ecological and conservation management. In this example, tracts of long‐unburnt mallee vegetation were identified as important habitat for a fire‐sensitive native mammal. Small mammal responses to fire can be predicted accurately at broad spatial scales; however, a conceptual model of post‐fire change in community structure developed in temperate Australia is not, on its own, sufficient for small mammals in semi‐arid systems.     

The conservation of arboreal marsupials in the Albury‐Wodonga region of south‐eastern Australia

Urban expansion is a major cause of land use change and presents a significant threat to biodiversity worldwide. Agricultural land is often acquired by local councils and developers to expand urban growth boundaries and establish new housing estates. However, many agricultural landscapes support high biodiversity values, especially farmlands that feature mosaics of native vegetation and keystone habitat such as hollow‐bearing trees. In south‐eastern Australia, many arboreal marsupials including the threatened Squirrel Glider (Petaurus norfolcensis) have populations within peri‐urban zones of expanding rural cities. A key challenge to planners, developers and conservation organisations is the need to maintain habitat for locally rare and threatened species as land undergoes changes in management. Critical to the sustainable development of peri‐urban landscapes is a thorough understanding of the distribution, habitat requirements and resources available to maintain and improve habitat for species dependent on limited resources such as tree cavities. In this management report, we present background information on an integrated research programme designed to evaluate potential impacts of urban development on fauna in the Albury Local Government Area, NSW. We mapped hollow‐bearing trees, erected nest boxes and monitored arboreal marsupials. Information presented in this report provides a blueprint for monitoring arboreal marsupials, including threatened species in other developing regions, and will assist the Albury‐Wodonga local governments in future planning of sustainable living environments.     

Long‐term response of temperate canopy trees to removal of browsing from an invasive arboreal herbivore in New Zealand

Defoliation of forest tree canopies by herbivores and other agents, leading to tree mortality and reduced productivity, threatens the ecological stability of forests globally. This study shows that long‐term control of a mammalian arboreal folivore (brushtail possums; Trichosurus vulpecula Phalangeridae) reduces crown dieback and increases foliage cover in browsing‐damaged canopy trees. We monitored indices of possum density, possum browsing, tree foliage cover and crown dieback for 20 years following initiation of possum control in 1994 that repeatedly reduced possum densities to near zero every 5–6 years and kept the population below 35% of pre‐control levels over the entire period. Observable possum browsing was recorded on 20–49% of individuals of three palatable tree species at the time of first control. Those percentages fell to zero after control and never exceeded 2–10% for individual species over the next 19 years. We recorded significant increases in foliage cover attributable to recovery from defoliation by possums for all three species during the first 10 years. Large increases in foliage cover occurred on individuals that were heavily browsed in 1994 (mean increases: 36–89%), but mean population increases were modest (3–19%) because only 10–19% of trees were initially heavily browsed. Twenty‐year mortality rates were similar for plants with, or without, initial possum browsing, indicating no residual impact of pre‐control browsing on tree mortality. Times for full recovery of crown foliage cover varied from 10 years for the youngest trees and faster growing species to more than 20 years for mature individuals of the slowest growing species.     

Revegetation,restoration and reptiles in rural landscapes: Insights from long‐term monitoring programmes in the temperate eucalypt woodlands of south‐eastern Australia

Over the past decade, there has been a concerted effort to better understand the distribution and abundance of reptiles in agricultural landscapes and to specifically evaluate their response to revegetation (tree and shrub plantings) and habitat restoration in the wheat‐sheep belt of south‐eastern Australia. This article reviews the response of reptiles to revegetation and woodland management and provides ten insights and lessons that can be applied to help improve reptile conservation in temperate eucalypt woodlands and fragmented agricultural landscapes in Australia. The review focuses primarily on revegetation programmes conducted by Landcare and Greening Australia, and management interventions funded by Local Land Services in NSW and Catchment Management Authorities in Victoria.     

Effects of European colonization on indigenous ecosystems: post-settlement changes in tree stand structures in Eucalyptus–Callitris woodlands in central New South Wales, Australia

Aim There has been considerable debate about pre‐settlement stand structures in temperate woodlands in south‐eastern Australia. Traditional histories assumed massive tree losses across the region, whereas a number of recent histories propose that woodlands were originally open and trees regenerated densely after settlement. To reconcile these conflicting models, we gathered quantitative data on pre‐settlement stand structures in Eucalyptus–Callitris woodlands in central New South Wales Australia, including: (1) tree density, composition, basal area and canopy cover at the time of European settlement; and (2) post‐settlement changes in these attributes. Location Woodlands dominated by Eucalyptus species and Callitris glaucophylla, which originally occupied approximately 100,000 km² in central New South Wales, Australia. Methods We recorded all evidence of pre‐settlement trees, including stumps, stags and veteran trees, from 39 relatively undisturbed 1‐ha stands within 16 State Forests evenly distributed across the region. Current trees were recorded in a nested 900 m² quadrat at each site. Allometric relationships were used to estimate girth over bark at breast height, tree basal area, and crown diameter from the girth of cut stumps. A post‐settlement disturbance index was developed to assess correlations between post‐settlement disturbance and attributes of pre‐settlement stands. Results The densities of all large trees (> 60 cm girth over bark at breast height) were significantly greater in current stands than at the time of European settlement (198 vs. 39 trees ha^?1). Pre‐settlement and current stands did not differ in basal area. However, the proportional representation of Eucalyptus and Callitris changed completely. At the time of settlement, stands were dominated by Eucalyptus (78% of basal area), whereas current stands are dominated by Callitris (74%). On average, Eucalyptus afforded 83% of crown cover at the time of settlement. Moreover, the estimated density, basal area and crown cover of Eucalyptus at the time of settlement were significantly negatively correlated with post‐settlement disturbance, which suggests that these results underestimate pre‐settlement Eucalyptus representation in the most disturbed stands. Main conclusions These results incorporate elements of traditional and recent vegetation histories. Since European settlement, State Forests have been transformed from Eucalyptus to Callitris dominance as a result of the widespread clearance of pre‐settlement Eucalyptus and dense post‐settlement recruitment of Callitris. Tree densities did increase greatly after European settlement, but most stands were much denser at the time of settlement than recent histories suggest. The original degree of dominance by Eucalyptus was unexpected, and has been consistently underestimated in the past. This study has greatly refined our understanding of post‐settlement changes in woodland stand structures, and will strengthen the foundation for management policies that incorporate historical benchmarks of landscape vegetation changes.     

A conceptual model of vegetation dynamics for the unique obligate‐seeder eucalypt woodlands of south‐western Australia

Models of vegetation dynamics framed as testable hypotheses provide powerful tools for predicting vegetation change in response to contemporary disturbances or climate change. Synthesizing existing information and applying new data, we develop a conceptual model of vegetation states and transitions for the previously overlooked woodlands dominated by obligate‐seeder eucalypts of dry to semi‐arid south‐western Australia. These comprise the largest extant temperate woodland globally, are uniquely dominated by a high diversity of obligate‐seeder eucalypts (55 taxa), but are under threat from wildfire. Our conceptual model incorporates four critical ecological processes that also distinguish obligate‐seeder woodlands from temperate woodlands dominated by resprouting eucalypts: (i) a lack of well‐protected epicormic buds results in major disturbances (prominently fire) being stand‐replacing. The pre‐disturbance tree cohort is killed, followed by dense post‐disturbance recruitment from seed shed from a serotinous seed bank; (ii) competition between saplings leads to self‐thinning over a multi‐century timeframe, with surviving individuals having great longevity (regularly >400 years); (iii) multiple processes limit recruitment in the absence of stand‐replacement disturbances, leading to frequent single‐cohort stands. However, unlike the few other obligate‐seeder eucalypt communities, trickle recruitment in very long‐unburnt stands can facilitate indefinite community persistence in the absence of stand‐replacement disturbances; and (iv) discontinuous fuels, relatively low understorey flammability (low grass and often high chenopod cover) and topographic barriers to fire (salt lakes) allow mature woodlands to persist for centuries without burning. Notably though, evidence suggests that flammability peaks at intermediate times since fire, establishing a ‘flammability bottleneck’ (or landscape fire trap) through which regenerating woodlands must pass. Our model provides a framework to support management to conserve obligate‐seeder eucalypt woodlands. Research into reasons for exceptional tree heights relative to ecosystem productivity, the evolution of diverse and dominant obligate‐seeder eucalypts, the paucity of grass, and the recent spatial distribution of fires, will further inform conservation management.     

Evaluating Habitat Quality for the Dusky Flycatcher

Abstract: We studied the dusky flycatcher (Empidonax oberholseri) at 8 sites in central Idaho, USA, in 2002 and 2003 to examine relationships among vegetation cover, density of breeding conspecifics, and indicators of habitat quality. Number of breeding territories and number of fledglings per hectare were positively associated, suggesting that the dusky flycatcher experienced increased reproductive success where it bred at the highest densities. However, the relationships between nesting success, annual reproductive success, number of fledglings per hectare, and amount of understory cover showed substantial annual variation. Nesting success did not differ significantly across sites or between years. Both reproductive success, expressed as young produced per hectare (range: 0.34–3.09 in 2002 and 0.79–3.82 in 2003) and young produced per nesting attempt (range: 0.71–2.78 in 2002 and 1.11–3.10 in 2003), differed across study sites in each year. Mean clutch size did not differ significantly among sites or years. Mean egg weight showed significant variation across some sites within years and was associated negatively with the 3 measures of reproductive success in 2002, although small sample sizes prevented reliable inference about the appropriateness of this measure as an indicator of habitat quality. Mean clutch size and mean egg weight were not associated with vegetation cover variables. Thus, dusky flycatcher reproductive success showed inconsistencies with individual vegetation measurements at the site scale. Forest managers who use vegetation treatments to increase amounts of understory shrub cover (e.g., by removing portions of the overstory conifer canopy) should increase densities of this species and, in turn, increase number of fledglings produced, but these responses appear to be better measured at the territory or nest scales than at the stand or site scales.     

Landscape structure influences tree density patterns in fragmented woodlands in semi‐arid eastern Australia

Landscape and local‐scale influences are important drivers of plant community structure. However, their relative contribution and the degree to which they interact remain unclear. We quantified the extent to which landscape structure, within‐patch habitat and their confounding effects determine post‐clearing tree densities and composition in agricultural landscapes in eastern subtropical Australia. Landscape structure (incorporating habitat fragmentation and loss) and within‐patch (site) features were quantified for 60 remnant patches of Eucalyptus populnea (Myrtaceae) woodland. Tree density and species for three ecological maturity classes (regeneration, early maturity, late maturity) and local site features were assessed in one 100 × 10 m plot per patch. All but one landscape characteristic was determined within a 1.3‐km radius of plots; Euclidean nearest neighbour distance was measured inside a 5‐km radius. Variation in tree density and composition for each maturity class was partitioned into independent landscape, independent site and joint effects of landscape and site features using redundancy analysis. Independent site effects explained more variation in regeneration density and composition than pure landscape effects; significant predictors were the proportion of early and late maturity trees at a site, rainfall and the associated interaction. Conversely, landscape structure explained greater variation in early and late maturity tree density and composition than site predictors. Area of remnant native vegetation within a landscape and patch characteristics (area, shape, edge contrast) were significant predictors of early maturity tree density. However, 31% of the explained variation in early mature tree differences represented confounding influences of landscape and local variables. We suggest that within‐patch characteristics are important in influencing semi‐arid woodland tree regeneration. However, independent and confounding effects of landscape structure resulting from previous vegetation clearing may have exerted a greater historical influence on older cohorts and should be accounted for when examining woodland dynamics across a broader range of environments.     

Within‐stand spatial structure and relation of boreal canopy and understorey vegetation

Question: How do spatial patterns and associations of canopy and understorey vegetation vary with spatial scale along a gradient of canopy composition in boreal mixed‐wood forests, from younger Aspen stands dominated by Populus tremuloides and P. balsamifera to older Mixed and Conifer stands dominated by Picea glauca? Do canopy evergreen conifers and broad‐leaved deciduous trees differ in their spatial relationships with understorey vegetation? Location: EMEND experimental site, Alberta, Canada. Methods: Canopy and understorey vegetation were sampled in 28 transects of 100 contiguous 0.5 m × 0.5 m quadrats in three forest stand types. Vegetation spatial patterns and relationships were analysed using wavelets. Results: Boreal mixed‐wood canopy and understorey vegetation are patchily distributed at a range of small spatial scales. The scale of canopy and understorey spatial patterns generally increased with increasing conifer presence in the canopy. Associations between canopy and understorey were highly variable among stand types, transects and spatial scales. Understorey vascular plant cover was generally positively associated with canopy deciduous tree cover and negatively associated with canopy conifer tree cover at spatial scales from 5–15 m. Understorey non‐vascular plant cover and community composition were more variable in their relationships with canopy cover, showing both positive and negative associations at a range of spatial scales. Conclusions: The spatial structure and relation of boreal mixed‐wood canopy and understorey vegetation varied with spatial scale. Differences in understorey spatial structure among stand types were consistent with a nucleation model of patch dynamics during succession in boreal mixed‐wood forests.     

Contingent effects of water balance variation on tree cover density in semiarid woodlands

Aim The local distribution of woody vegetation affects most functional aspects of semiarid landscapes, from soil erosion to nutrient cycling. With growing concern about anthropogenic climate change, it has become critical to understand the ecological determinants of woody plant distribution in semiarid landscapes. However, relatively little work has examined the determinants of local variation in woody cover. Here we examine water balance controls associated with patterns of tree cover density in a topographically complex semiarid woodland. Location Los Pinos Mountains, Sevilleta National Wildlife Refuge LTER, New Mexico, USA. Methods To explore the relationship between local water balance variation and tree cover density, we used a combination of high‐resolution (1 × 1 m), remotely sensed imagery and quantitative estimates of water balance variation in space and time. Regression tree analysis (RTA) was used to identify the environmental parameters that best predict variation in tree cover density. Results Using six predictor variables, the RTA explains 39% of the deviance in tree cover density over the landscape. The relationship between water balance conditions and tree cover density is highly contingent; that is, similar tree cover densities occur under very different combinations of water balance parameters. Thus, the effect of one environmental parameter on tree cover density depends on the values of other parameters. After tree cover density is adjusted for water balance conditions, residual variation is related to tree cover density in the neighbourhood of a particular location. Conclusion In semiarid landscapes, vegetation structure is largely controlled by water supply and demand. Results presented here indicate that localized feedbacks and site‐specific historical processes are critical for understanding the responses of semiarid vegetation to climate change.     

Paddock trees, parrots and agricultural production: An urgent need for large-scale, long-term restoration in south-eastern Australia

Summary Scattered trees, or ‘paddock trees’, are keystone structures, which provide multiple ecological values. However, they are in decline in many places. This has serious implications for species that use them, such as the vulnerable Superb Parrot (Polytelis swainsonii) of south‐eastern Australia. We outline three key aspects of the ecology, biology and distribution of the species that illustrate the implications of scattered tree decline. These are that (i) it depends on trees; (ii) it lives across agricultural landscapes; and (iii) it uses scattered tree landscapes dynamically in response to climate variation. We outline the dual challenge of maintaining populations of both scattered trees and the Superb Parrot over large scales and over the long term. Without urgent restoration action, a narrow bottleneck (where there are few mature trees) will make the long‐term future of the Superb Parrot precarious in these landscapes. We outline a vision for future landscapes that addresses this challenge, including the development of a form of Australian ‘wood‐pasture’. We suggest some ways that might be implemented at two scales. At the farm scale, we suggest (i) protecting what remnant vegetation we currently have; (ii) recruiting future large, old trees; (iii) sequentially setting aside land to ensure whole‐of‐farm tree regeneration; (iv) use of incentives to encourage restoration actions; and (v) using a revolving land fund to purchase and reorganize farms into economically and ecologically sustainable units. At the landscape scale, we suggest (i) the need for coordination of long‐term landscape restoration plans; (ii) the possible collaborative management of adjacent farms to ensure economic and ecological sustainability. We conclude that addressing the large‐scale and long‐term challenges of restoring scattered trees in landscapes occupied by the Superb Parrot could restore lost or diminished ecological services. This challenge illustrates the need for action at both the farm and the landscape scale that is planned over the short, medium and long term.