Spatial Pattern of Attacks of the Invasive Woodwasp Sirex noctilio,at Landscape and Stand Scales

Invasive insect pests are responsible for important damage to native and plantation forests, when population outbreaks occur. Understanding the spatial pattern of attacks by forest pest populations is essential to improve our understanding of insect population dynamics and for predicting attack risk by invasives or planning pest management strategies. The woodwasp Sirex noctilio is an invasive woodwasp that has become probably the most important pest of pine plantations in the Southern Hemisphere. Our aim was to study the spatial dynamics of S. noctilio populations in Southern Argentina. Specifically we describe: (1) the spatial patterns of S. noctilio outbreaks and their relation with environmental factors at a landscape scale; and (2) characterize the spatial pattern of attacked trees at the stand scale. We surveyed the spatial distribution of S. noctilio outbreaks in three pine plantation landscapes, and we assessed potential associations with topographic variables, habitat characteristics, and distance to other outbreaks. We also looked at the spatial distribution of attacked trees in 20 stands with different levels of infestation, and assessed the relationship of attacks with stand composition and management. We found that the spatial pattern of pine stands with S. noctilio outbreaks at the landscape scale is influenced mainly by the host species present, slope aspect, and distance to other outbreaks. At a stand scale, there is strong aggregation of attacked trees in stands with intermediate infestation levels, and the degree of attacks is influenced by host species and plantation management. We conclude that the pattern of S. noctilio damage at different spatial scales is influenced by a combination of both inherent population dynamics and the underlying patterns of environmental factors. Our results have important implications for the understanding and management of invasive insect outbreaks in forest systems.     

Review of forest landscape models: Types, methods, development and applications

Forest landscape models simulate forest change through time using spatially referenced data across a broad spatial scale (i.e. landscape scale) generally larger than a single forest stand. Spatial interactions between forest stands are a key component of such models. These models can incorporate other spatio-temporal processes such as natural disturbances (e.g. wildfires, hurricanes, outbreaks of native and exotic invasive pests and diseases) and human influences (e.g. harvesting and commercial thinning, planting, fire suppression). The models are increasingly used as tools for studying forest management, ecological assessment, restoration planning, and climate change. In this paper, we define forest landscape models and discuss development, components, and types of the models. We also review commonly used methods and approaches of modeling forest landscapes, their application, and their strengths and weaknesses. New developments in computer sciences, geographic information systems (GIS), remote sensing technologies, decision-support systems, and geo-spatial statistics have provided opportunities for developing a new generation of forest landscape models that are increasingly valuable for ecological research, restoration planning and resource management.     

Review of forest landscape models: Types, methods, development and applications

Forest landscape models simulate forest change through time using spatially referenced data across a broad spatial scale (i.e. landscape scale) generally larger than a single forest stand. Spatial interactions between forest stands are a key component of such models. These models can incorporate other spatio-temporal processes such as natural disturbances (e.g. wildfires, hurricanes, outbreaks of native and exotic invasive pests and diseases) and human influences (e.g. harvesting and commercial thinning, planting, fire suppression). The models are increasingly used as tools for studying forest management, ecological assessment, restoration planning, and climate change. In this paper, we define forest landscape models and discuss development, components, and types of the models. We also review commonly used methods and approaches of modeling forest landscapes, their application, and their strengths and weaknesses. New developments in computer sciences, geographic information systems (GIS), remote sensing technologies, decision-support systems, and geo-spatial statistics have provided opportunities for developing a new generation of forest landscape models that are increasingly valuable for ecological research, restoration planning and resource management.     

Can hyperparasitoids cause large‐scale outbreaks of insect herbivores?

Synchronous population fluctuations occur in many species and have large economic impacts, but remain poorly understood. Dispersal, climate and natural enemies have been hypothesized to cause synchronous population fluctuations across large areas. For example, insect herbivores cause extensive forest defoliation and have many natural enemies, such as parasitoids, that may cause landscape‐scale changes in density. Between outbreaks, parasitoid‐caused mortality of hosts/herbivores is high, but it drops substantially during outbreak episodes. Because of their essential role in regulating herbivore populations, we need to include parasitoids in spatial modelling approaches to more effectively manage insect defoliation. However, classic host‐parasitoid population models predict parasitoid density, and parasitoid density is difficult to relate to host‐level observations of parasitoid‐caused mortality. We constructed a novel model to study how parasitoids affect insect outbreaks at the landscape scale. The model represents metacommunity dynamics, in which herbivore regulation, colonisation and extinction are driven by interactions with the forest, primary parasitoids and hyperparasitoids. The model suggests that parasitoid spatial dynamics can produce landscape‐scale outbreaks. Our results propose the testable prediction that hyperparasitoid prevalence should increase just before the onset of an outbreak because of hyperparasitoid overexploitation. If verified empirically, hyperparasitoid distribution could provide a biotic indicator that an outbreak will occur.     

LANDIS PRO: a landscape model that predicts forest composition and structure changes at regional scales

LANDIS PRO predicts forest composition and structure changes incorporating species‐, stand‐, and landscape‐scales processes at regional scales. Species‐scale processes include tree growth, establishment, and mortality. Stand‐scale processes contain density‐ and size‐related resource competition that regulates self‐thinning and seedling establishment. Landscape‐scale processes include seed dispersal and disturbances. LANDIS PRO is designed to be compatible with forest inventory data, thus extensive inventory data can be directly utilized to initialize and calibrate model parameters before predicting future forest changes. LANDIS PRO allows for exploring the effects of disturbances, management, climate change, and modeling the spread of invasive species. We demonstrate that LANDIS PRO successfully predicts forest successional trajectories and stand development patterns in the Central Hardwood Forest region in U.S.     

Bryophyte species richness and composition in young forests regenerated after clear-cut logging versus after wildfire and spruce budworm outbreak

The disturbance regime in mixed-wood forests of eastern Canada is characterized by both natural disturbances including wildfires and insect outbreaks as well as forestry. The understanding of how understorey plant assemblages respond to different disturbances is mostly limited to short-term wildfire-logging comparisons of vascular plants. Here, we compare patterns of species richness and composition of four bryophyte guilds in young forests (approx. 40 years old) regenerating after clear-cut logging, wildfire, and spruce budworm outbreak. In addition, young forests were compared with mature spruce-fir dominated stands (approx. 90 years old). Although similar in overall species richness at the scale of 1,000 m² all young forest types were compositionally distinct with fewer species than mature forests. Stands developed after spruce budworm outbreaks had the highest canopy cover values and the highest surface area of coarse woody debris. These stands had similar numbers of woody debris species as mature forests and were closest to mature forests in species composition. Wildfire-disturbed sites were dominated by deciduous trees and a high number of treebase species. Finally, young managed forest had the highest number of forest floor bryophytes at the scale of 100 m² among the three young forest types, but was compositionally far from mature forests in their woody debris flora. In conclusion, young forests regenerating after natural disturbances are distinctly different from young forests regenerated after clear-cutting and if natural disturbances are eliminated certain species (e.g., epixylic and treebase species) might become more restricted to older stands in the landscape.     

Does long‐distance pollen dispersal preclude inbreeding in tropical trees? Fragmentation genetics of Dysoxylum malabaricum in an agro‐forest landscape

Tropical trees often display long‐distance pollen dispersal, even in highly fragmented landscapes. Understanding how patterns of spatial isolation influence pollen dispersal and interact with background patterns of fine‐scale spatial genetic structure (FSGS) is critical for evaluating the genetic consequences of habitat fragmentation. In the endangered tropical timber tree Dysoxylum malabaricum (Meliaceae), we apply eleven microsatellite markers with paternity and parentage analysis to directly estimate historic gene flow and contemporary pollen dispersal across a large area (216 km²) in a highly fragmented agro‐forest landscape. A comparison of genetic diversity and genetic structure in adult and juvenile life stages indicates an increase in differentiation and FSGS over time. Paternity analysis and parentage analysis demonstrate high genetic connectivity across the landscape by pollen dispersal. A comparison between mother trees in forest patches with low and high densities of adult trees shows that the frequency of short‐distance mating increases, as does average kinship among mates in low‐density stands. This indicates that there are potentially negative genetic consequences of low population density associated with forest fragmentation. Single isolated trees, in contrast, frequently receive heterogeneous pollen from distances exceeding 5 km. We discuss the processes leading to the observed patterns of pollen dispersal and the implications of this for conservation management of D. malabaricum and tropical trees more generally.     

The value of timber quality forests for insect conservation on Tierra del Fuego Island compared to associated non-timber quality stands

Insect community studies related to forest management focus principally on timber-quality stands, and often omit the remainder of the landscape. This study aimed mainly to compare insect communities of primary timber-quality forests (Nothofagus pumilio) with associated non-timber-quality stands (wetland, edge, riparian and N. antarctica forests), and secondarily to characterize these insect assemblages throughout the growing season and at different vertical strata to evaluate the importance of each habitat type for insect conservation. A total of 18,800 individuals belonging to 231 RTUs (recognizable taxonomic units) were identified, of which Diptera, Hymenoptera, Lepidoptera and Coleoptera were the dominant orders. Lepidoptera RTUs were mostly generalists, while the other main orders were most frequently found in timber-quality forests and included many RTUs with specific environmental requirements. Timber-quality stands had higher richness and abundance than associated non-timber-quality forests and possessed more exclusive species (18%), while 39% of RTUs were shared between all sites. The spatial heterogeneity of timber-quality stands generated different niches and favored insect diversity, which would not have been maintained by protecting non-timber-quality stands alone. Consequently, the proper management of subantarctic Nothofagus forests must include the conservation of timber-quality stands, as protection of non-timber-quality areas alone will not be sufficient for insect conservation at the landscape scale.     

空间直观景观模型LANDIS Ⅰ．运行机制

空间直观景观模型是指在异质景观中模拟景观尺度上生态过程的空间直观模型．LANDIS是一个用于模拟森林景观干扰、演替和管理的空间直观景观模型．通过在样地尺度上跟踪以10年为间隔的物种年龄级,半定量化地描述火和风倒,及使用位数组表示物种年龄结构,LANDIS能同时在物种、样地和景观尺度上模拟各种生态过程及其相互关系．详细论述了LANDIS模型对种子传播、火、风倒和砍伐等生态过程的模拟,并讨论了模型中存在的一些不足．     

Simulating the Effects of Fire Reintroduction Versus Continued Fire Absence on Forest Composition and Landscape Structure in the Boundary Waters Canoe Area, Northern Minnesota, USA

The Boundary Waters Canoe Area (BWCA) Wilderness of northern Minnesota, USA, ememplifies how fire management and natural disturbance determine forest composition and landscape structure at a broad scale. Historically, the BWCA (>400,000 ha) was subject to crown fires with a mean rotation period of 50–100 y. Fires often overlapped, creating a mosaic of differently aged stands with many stands burning frequently or, alternatively, escaping fire for several centuries. The BWCA may never have reached a steady-state (defined as a stable landscape age-class structure). In the early 1900s, a diminished fire regime began creating a more demographically diverse forest, characterized by increasingly uneven-aged stands. Shade-tolerant species typical of the region began replacing the shade-intolerant species that composed the fire-generated even-aged stands. Red pine (Pinus resinosa) stands are relatively uncommon in the BWCA today and are of special concern. The replacement of early-to-midsuccessional species is occurring at the scale of individual gaps, producing mixed-species multiaged forests. We used LANDIS, a spatially explicit forest landscape model, to investigate the long-term consequences of fire reintroduction or continuing fire absence on forest composition and landscape structure. Fire reintroduction was evaluated at three potential mean fire rotation periods (FRP): 50,100, and 300 y. Our model scenarios predict that if fire reintroduction mimics the natural fire regime (bracketed by FRP = 50 and 100 y), it will be most successful at preserving the original species composition and landscape structure, although jack pine (Pinus banksiana) may require special management. With limited fire reintroduction, all of the extant species are retained although species dominance and landscape structure will be substantially altered. If fire remains absent, many fire-dependent species will be lost as local dominants, including red pine. The landscape appears to be in a state of rapid change and a shift in management to promote fire may need to be implemented soon to prevent further deviation from historic, presettlement conditions.     

Predicted range expansion of the invasive plant <Emphasis Type="Italic">Leucaena leucocephala</Emphasis> in the Hengchun peninsula,Taiwan

We integrated correlative (species distribution) and process-based (agent-based) modeling approaches—to predict future range expansion of an invasive plant (Leucaena leucocephala) in the lowland rainforest and tropical coastal forest ecosystems of the Hengchun peninsula, Taiwan. We simulated range expansion to the year 2027 using a spatially-explicit, agent-based model representing invasion rate as a function of habitat quality and propagule pressure. We developed an index of habitat quality by relating 1988 plant distribution data to geo-referenced data on climatic conditions, landscape features, and anthropogenic factors via logistic regression. We represented propagule pressure using a lognormal dispersal kernel. We evaluated model performance by simulating range expansion from 1988 to 2007 and comparing simulated distribution patterns to those observed in 2007. Results of logistic regression indicated that L. leucocephala is more likely to occur in warm, dry areas containing a higher percentage of natural landscape (forest or grassland), areas adjacent to the forest edge, and areas disturbed by human activities such as a main road or an abandoned sisal plantation. Model evaluation showed that the prediction performance is excellent with AUC > 0.9 and Mantel’s r = 0.77. Our results indicated that L. leucocephala will continue from the western portion toward the southern and central portions of Checheng township, and throughout the southern portion of Hengchun and Manjhou townships, with about 2500 ha of new area invaded within the next 20 years. Our predictions should allow managers to develop proactive management plans for the areas most likely to be invaded.     

Aridity indices predict organic matter decomposition and comminution processes at landscape scale

Microbial decomposition and invertebrate comminution of a particular organic substrate are largely regulated by temperature and water availability. Numerous metrics have been used to model decay processes at large regional-to-global scales. However, their use at smaller landscape scales might not be practical or feasible. Aridity, generally defined as the balance between long term annual precipitation (P) and potential evapotranspiration (PET), is a metric that synthesizes the major climatic drivers regulating ecosystem processes including the activity of microbes and invertebrates on the forest floor. Thus, aridity indices (AIs) can theoretically represent suitable predictors of decomposition and comminution processes at landscape scale.We investigated our hypothesis in a sclerophyll forest in south-east Australia, where decomposition and comminution rates of Eucalyptus globulus leaf litter were measured in eight sites positioned along an aridity gradient caused by variable exposure to solar radiation. Four sites were also instrumented to continuously monitor air, litter and soil microclimatic variables.We found that AIs were strongly related to above- and below-ground microbial decomposition rates, as well as above-ground comminution rates. Some microclimatic variables, such as shortwave radiation, air relative humidity and litter temperature were also significantly related to above-ground processes, but not below-ground decomposition. Among the AIs tested, the index calculated using the Priestley-Taylor equation for PET had consistently higher coefficients of determination with decomposition and comminution rates. Our case study suggests that AIs can represent robust predictors of both decomposition and comminution processes at landscape scale and useful surrogates for more expensive microclimatic predictors collected at site level. AIs could also be used across spatial scales (from local to continental) to improve biogeochemical and hydrological models by incorporating a spatially-explicit representation of decay processes.     

大尺度生态水文模型的构建及其与GIS集成

基于过程模拟手段揭示森林植被的生态水文功能和变化机制,已经成为生态水文学研究的重要手段。由于陆地生态水文过程的非线性和尺度问题的广泛性,基于过程的坡面或小流域尺度的分布式水文模型不适合大流域的水文过程的分析和预测;另外,传统的水文模型主要侧重水文物理过程,只有充分耦合植被生态过程,才能从机制上揭示森林植被参与水文循环的调控作用。依据大流域的水文过程特点,从5个方面阐述了大尺度生态水文模型构建过程中的主要问题：①大尺度生态水文模型的概念和结构;②尺度的界定与匹配;③离散化数据集的建立,着重分析了植被覆盖、土壤质地、山地气候等主要数据集的建立方法;④分布式与集总式模型,这两类模型可以从他们的基本空间单元上进行区分,数字流域的建立和空间分析手段使得集总式模型和分布式模型得到了很好的结合;⑤生态水文模型与GIS的集成。分析了4种不同的集成方式,“松散型”的集成方式因其编程工作量小而被广泛采用。集成的目的不仅是要提高模拟的技术水平,更要提高系统整体的概念化水平。     

Scale-Dependent Effects of Landscape Structure and Composition on Diurnal Roost Selection by Forest Bats

Abstract: Forest management affects the quality and availability of roost sites for forest-dwelling bats, but information on roost selection beyond the scale of individual forest stands is limited. We evaluated effects of topography (elevation, slope, and proximity of roads and streams), forest habitat class, and landscape patch configuration on selection of summer diurnal roosts by 6 species of forest-dwelling bats in a diverse forested landscape of the Ouachita Mountains, Arkansas, USA. Our objectives were to identify landscape attributes that potentially affect roost placement, determine whether commonalities exist among species in their response to landscape attributes, and evaluate the effects of scale. We modeled roost selection at 2 spatial scales (250- and 1,000-m radius around each roost). For each species, parameters included in models differed between the 2 scales, and there were no shared parameters for 2 species. Average coefficients of determination (R²) for small-scale models were generally higher than for large-scale models. Abundance of certain forest habitat classes were included more often than patch configuration or topography in differentiating roost from random locations, regardless of scale, and most species were more likely to roost in areas containing abundant thinned forest. Among topographic metrics, big brown bats (Eptesicus fuscus) were more likely to roost at higher elevations; roosts of big brown bats, northern long-eared bats (Myotis septentrionalis), and Seminole bats (Lasiurus seminolus) were influenced by slope; and big brown bats, evening bats (Nycticeius humeralis), and Seminole bats were more likely to roost closer to water than random. Northern long-eared bats and red bats (Lasiurus borealis) were more likely to roost closer to roads, whereas eastern pipistrelles (Perimyotis subflavus) were more likely to roost further from roads than random. Common parameters in most models included 1) positive associations with group selection (5 of 6 species) and thinned mature forest (4 species) at the small scale; 2) negative associations with unmanaged mixed pine-hardwood forest 50–99 years old at the large scale (4 species); 3) negative association with stands of immature pine 15–29 years old at the small scale (3 species); and 4) a positive association with largest patch index at the large scale (3 species). Our results suggest that, in a completely forested landscape, a variety of stand types, seral stages, and management conditions, varying in size and topographic location throughout the landscape, would likely provide the landscape components for roosting required to maintain a diverse community of forest bats in the Ouachita Mountains.     

Long‐term colonization ecology of forest‐dwelling species in a fragmented rural landscape – dispersal versus establishment

Species colonization in a new habitat patch is an efficiency indicator of biodiversity conservation. Colonization is a two‐step process of dispersal and establishment, characterized by the compatibility of plant traits with landscape structure and habitat conditions. Therefore, ecological trait profiling of specialist species is initially required to estimate the relative importance of colonization filters. Old planted parks best satisfy the criteria of a newly created and structurally matured habitat for forest‐dwelling plant species. We sampled species in 230 ancient deciduous forests (source habitat), 74 closed‐canopy manor parks (target habitats), 151 linear wooded habitats (landscape corridors), and 97 open habitats (isolating matrix) in Estonia. We defined two species groups of interest: forest (107 species) and corridor specialists (53 species). An extra group of open habitat specialists was extracted for trait scaling. Differing from expectations, forest specialists have high plasticity in reproduction mechanisms: smaller seeds, larger dispersules, complementary selfing ability, and diversity of dispersal vectors. Forest specialists are shorter, less nutrient‐demanding and mycorrhizal‐dependent, stress‐tolerant disturbance‐sensitive competitors, while corridor specialists are large‐seeded disturbance‐tolerant competitors. About 40% of species from local species pools have immigrated into parks. The historic forest area, establishment‐related traits, and stand quality enhance the colonization of forest specialists. The openness of landscape and mowing in the park facilitate corridor specialists. Species traits in parks vary between a forest and corridor specialist, except for earlier flowering and larger propagules. Forest species are not dispersal limited, but they continue to be limited by habitat properties even in the long term. Therefore, the shady parts of historic parks should be appreciated as important forest biodiversity‐enhancing landscape structures. The habitat quality of secondary stands can be improved by nurturing a heterogeneous shrub and tree layer, and modest herb layer management.     

Frugivore Behavioural Details Matter for Seed Dispersal: A Multi-Species Model for Cantabrian Thrushes and Trees

Animal movement and behaviour is fundamental for ecosystem functioning. The process of seed dispersal by frugivorous animals is a showcase for this paradigm since their behaviour shapes the spatial patterns of the earliest stage of plant regeneration. However, we still lack a general understanding of how intrinsic (frugivore and plant species traits) and extrinsic (landscape features) factors interact to determine how seeds of a given species are more likely to be deposited in some places more than in others. We develop a multi-species mechanistic model of seed dispersal based on frugivore behavioural responses to landscape heterogeneity. The model was fitted to data from three-years of spatially-explicit field observations on the behaviour of six frugivorous thrushes and the fruiting patterns of three fleshy-fruited trees in a secondary forest of the Cantabrian range (N Spain). With such model we explore how seed rain patterns arise from the interaction between animal behaviour and landscape heterogeneity. We show that different species of thrushes respond differently to landscape heterogeneity even though they belong to the same genus, and that provide complementary seed dispersal functions. Simulated seed rain patterns are only realistic when at least some landscape heterogeneity (forest cover and fruit abundance) is taken into account. The common and simple approach of re-sampling movement data to quantify seed dispersal produces biases in both the distance and the habitat at which seeds arrive. Movement behaviour not only affects dispersal distance and seed rain patterns but also can affect frugivore diet composition even if there is no built-in preference for fruiting species. In summary, the fate of seeds produced by a given plant species is strongly affected by both the composition of the frugivore assemblage and the landscape-scale context of the plant location, including the presence of fruits from other plants (from the same or different species).     

Landscape host abundance and configuration regulate periodic outbreak behavior in spruce budworm Choristoneura fumiferana

Landscape‐level forest management has long been hypothesized to affect forest insect outbreak dynamics, but empirical evidence remains elusive. We hypothesized that the combination of increased hardwood relative to host tree species, prevalence of younger forests, and fragmentation of those forests due to forest harvesting legacies would reduce outbreak intensity, increase outbreak frequency, and decrease spatial synchrony in spruce budworm Choristoneura fumiferana outbreaks. We investigated these hypotheses using tree ring samples collected across 51 sites pooled into 16 subareas distributed across a large ecoregion spanning the international border between Ontario (Canada), and Minnesota (USA). This ecoregion contains contrasting land management zones with clear differences in forest landscape structure (i.e. forest composition and spatial configuration) while minimizing the confounding influence of climate. Cluster analyses of the 76‐yr time‐series generally grouped by subareas found within the same land management zone. Spatial nonparametric covariance analysis indicated that the highest and lowest degree of spatial synchrony of spruce budworm outbreaks were found within unmanaged wilderness and lands managed at fine spatial scales in Minnesota, respectively. Using multivariate analysis, we also found that forest composition, configuration, and climate together accounted for a total of 40% of the variance in outbreak chronologies, with a high level of shared variance between composition and configuration (13%) and between composition and climate (9%). At the scale of our study, climate on its own did not explain any of the spatial variation in outbreaks. Outbreaks were of higher frequency, lower intensity, and less spatially synchronized in more fragmented, younger forests with a lower proportion of host species, with opposing outbreak characteristics observed in regions characterised by older forests with more concentrated host species. Our study is the first quantitative evaluation of the long‐standing ‘silvicultural hypothesis’ of spruce budworm management specifically conducted at a spatio‐temporal scale for which it was intended.     

Multi‐scale effects of habitat structure and landscape context on a vertebrate with limited dispersal ability (the brown‐throated sloth,Bradypus variegatus)

As human population, food consumption, and demand for forest products continue to rise over the next century, the pressures of land‐use change on biodiversity are projected to intensify. In tropical regions, countryside habitats that retain abundant tree cover and structurally complex canopies may complement protected areas by providing suitable habitats and landscape connectivity for a significant portion of the native biota. Species with low dispersal capabilities are among the most at risk of extinction as a consequence of land‐use change. We assessed how the spatial distribution of the brown‐throated sloth (Bradypus variegatus), a model species for a vertebrate with limited dispersal ability, is shaped by differences in habitat structure and landscape patterns of countryside habitats in north‐central Costa Rica using a multi‐scale framework. We quantified the influence of local habitat characteristics and landscape context on sloth occurrence using mixed‐effects logistic regression models. We recorded 27 sloths within countryside habitats and found that both local and landscape factors significantly influenced their spatial distribution. Locally, sloths favored structurally complex habitats, with greater canopy cover and variation in tree height and basal area. At the landscape scale, sloths demonstrated a preference for habitats with high proportions of forest and nearby large tracts of forest. Although mixed‐use areas and tree plantations are not substitutes for protected forests, our results suggest they provide important supplemental habitats for sloths. To promote the conservation and long‐term viability of sloth populations in the tropical countryside, we recommend that land managers retain structurally complex vegetation and large patches of native habitat.     

Combining Niche and Dispersal in a Simple Model (NDM) of Species Distribution

Predicting the distribution of species has become a crucial issue in biodiversity research. Two kinds of model address this question: niche models, which are usually based on static approaches linking species distribution to habitat characteristics, and dispersal models, which are usually dynamic and process-based. We propose a model (NDM: niche and dispersal model) that considers the local presence of a species to result from a dynamic balance between extinction (based on the niche concept) and immigration (based on the dispersal concept), at a given moment in time, in a spatially explicit context. We show that NDM correctly predicts observed bird species and community distributions at different scales. NDM helps to reconcile the contrasting paradigms of metacommunity theory. It shows that sorting and mass effects are the factors determining bird species distribution. One of the most interesting features of NDM is its ability to predict well known properties of communities, such as decreasing species richness with decreasing patch size and increasing distance to the mainland, and the mid-domain effect at the regional scale, contrasting with predictions of much smaller effects at the local scale. NDM shows that habitat destruction in the matrix around patches of forest can affect the forest bird community, principally by decreasing the occurrence of typical matrix birds within the forest. This model could be used as the starting point for applied ecological studies on the management of species and community distributions.     

Importance of semi-natural habitats for the conservation of butterfly communities in landscapes dominated by pine plantations

While the area of plantation forests continues to increase worldwide, their contribution to the conservation of biodiversity is still controversial. There is a particular concern on the central role played by natural habitat remnants embedded within the plantation matrix in conserving species-rich insect communities. We surveyed butterflies in maritime pine plantation landscapes in south-western France in 83 plots belonging to seven habitat types (five successional stages of pine stands, native deciduous woodlands and herbaceous firebreaks). The effect of plot, habitat and landscape attributes on butterfly species richness, community composition and individual species were analysed with a General Linear Model (GLM), partial Canonical Correspondence Analysis (CCA) and the IndVal method. The most important factors determining butterfly diversity and community composition were the presence of semi-natural habitats (deciduous woodlands and firebreaks) at the landscape scale and the composition of understorey vegetation at the plot scale. Pure effects of plot variables explained the largest part of community variation (12.8%), but landscape factors explained an additional, independent part (6.7%). Firebreaks were characterized by a higher species richness and both firebreaks and deciduous woodlands harboured species not or rarely found in pine stands. Despite the forest-dominated landscape, typical forest butterflies were rare and mainly found in the deciduous woodlands. Threatened species, such as Coenonympha oedippus and Euphydryas aurinia, were found in pine stands and in firebreaks, but were more abundant in the latter. In the studied plantation forest, the conservation of butterflies depends mainly on the preservation of semi-natural habitats, an adequate understorey management and the maintenance of soil moisture levels.