Increasing deterministic control of primary succession on Mount St. Helens,Washington

Question: Does the relative importance of stochastic and deterministic factors change during primary succession? Location: Small depressions (potholes) located on Mount St. Helens, Washington (46°13′51″N, 122°09′10″W, 1290 m). Methods: Pothole vegetation was described in 1993, 1997 and from 2001 to 2008. Explanatory variables included location and elevation (spatial factors), soil factors and Lupinus lepidus cover from prior years (a fertility surrogate). RDA assessed species‐variable relationships. DCA calculated β diversity and within‐year heterogeneity. Flexible sorting classified the vegetation. Species composition, richness, cover, H′ and evenness were also calculated. Results: Vegetation cover increased through 2001, and then fluctuated due to changes in L. lepidus cover. Richness peaked in 2005, after which pioneer species began to decline as persistent evergreen species increased. The six CTs recognized in 2008 were more scattered than were the six different CTs from 2001. DCA demonstrated that woody and rhizomatous species increased as pothole vegetation became less variable. RDA revealed weak spatial relationships in 1993, 1997 and 2001; thereafter, environmental and biological factors became important. The species‐explanatory data relationship increased during this study from 10.2% to 36.0%, leaving 64.0% of the variation unexplained. Conclusions: This is the first temporal study to demonstrate that deterministic control of vegetation development increases during succession. Pothole vegetation has converged somewhat due to deterministic factors, but the initial effects of chance, local disturbances and history remain large and may prevent strong convergence.     

Vegetation patterns 25 years after the eruption of Mount St. Helens, Washington, USA

In 2004, we surveyed the vegetation on Mount St. Helens to document changes since 1992. We asked how communities differentiate and if they develop predictable relationships with local environments. We sought evidence from links between species and environment and changes in community structure in 271 250-m(2) plots. The habitats of the seven community types (CTs) overlapped broadly. Ordination methods demonstrated weak correlations among species distributions and location, elevation, and surface variables. Comparisons to 1992 by habitat demonstrated a large increase in plant cover and substantial development of vegetation structure. Pioneer species declined while mosses increased proportionately leading to more pronounced dominance hierarchies in most habitats. In Lupinus colonies, dominance declined, and diversity increased due to the increased abundance of formerly rare species. On once barren sites, dominance increased, but diversity changed slightly, which suggested the incipient development of competitive hierarchies. Weak correlations between vegetation and the environment suggested that initially stochastic establishment patterns had not yet been erased by deterministic factors. A vegetation mosaic that is loosely controlled by environmental factors may produce different successional trajectories that lead to alternative stable communities in similar habitats. This result has implications for restoration planning.     

Subalpine vegetation pattern three decades after stand‐replacing fire: effects of landscape context and topography on plant community composition,tree regeneration,and diversity

Objective: Our purpose was to characterize vegetation compositional patterns, tree regeneration, and plant diversity, and their relationships to landscape context, topography, and light availability across the margins of four stand‐replacing subalpine burns. Location: Four 1977 to 1978 burns east of the Continental Divide in Colorado: the Ouzel burn, a burn near Kenosha Pass, the Badger Mountain burn, and the Maes Creek burn. Methods: Vegetation and environmental factors were sampled in 200 0.01‐ha plots on transects crossing burn edges, and stratified by elevation. We utilized dissimilarity indices, mixed‐effects models, and randomization tests to assess relationships between vegetation and environment. Results: Three decades after wildfire, plant communities exhibited pronounced compositional shifts across burn edges. Tree regeneration decreased with increasing elevation and distance into burn interiors; concomitant increases in forbs and graminoids were linked to greater light availability. Richness was roughly doubled in high‐severity burn interiors due to the persistence of a suite of native species occurring primarily in this habitat. Richness rose with distance into burns, but declined with increasing elevation. Only three of 188 plant species were non‐native; these were widespread, naturalized species that comprised <1% total cover. Conclusions: These subalpine wildfires generated considerable, persistent increases in plant species richness at local and landscape scales, and a diversity of plant communities. The findings suggest that fire suppression in such systems must lead to reduced diversity. Concerns about post‐fire invasion by exotic plants appear unwarranted in high‐elevation wilderness settings.     

Effects of spatial heterogeneity on butterfly species richness in Rocky Mountain National Park, CO, USA

We investigated butterfly responses to plot-level characteristics (plant species richness, vegetation height, and range in NDVI [normalized difference vegetation index]) and spatial heterogeneity in topography and landscape patterns (composition and configuration) at multiple spatial scales. Stratified random sampling was used to collect data on butterfly species richness from seventy-six 20 × 50 m plots. The plant species richness and average vegetation height data were collected from 76 modified-Whittaker plots overlaid on 76 butterfly plots. Spatial heterogeneity around sample plots was quantified by measuring topographic variables and landscape metrics at eight spatial extents (radii of 300, 600 to 2,400 m). The number of butterfly species recorded was strongly positively correlated with plant species richness, proportion of shrubland and mean patch size of shrubland. Patterns in butterfly species richness were negatively correlated with other variables including mean patch size, average vegetation height, elevation, and range in NDVI. The best predictive model selected using Akaike’s Information Criterion corrected for small sample size (AIC_c), explained 62% of the variation in butterfly species richness at the 2,100 m spatial extent. Average vegetation height and mean patch size were among the best predictors of butterfly species richness. The models that included plot-level information and topographic variables explained relatively less variation in butterfly species richness, and were improved significantly after including landscape metrics. Our results suggest that spatial heterogeneity greatly influences patterns in butterfly species richness, and that it should be explicitly considered in conservation and management actions.     

Climate and coastal dune vegetation: disturbance, recovery, and succession

The sand dune habitats found on barrier islands and other coastal areas support a dynamic plant community while protecting areas further inland from waves and wind. Foredune, interdune, and backdune habitats common to most coastal dunes have very different vegetation, likely because of the interplay among plant succession, exposure, disturbance, and resource availability. However, surprisingly few long-term data are available describing dune vegetation patterns. A nine-year census of 294 plots on St. George Island, Florida suggests that the major climatic drivers of vegetation patterns vary with habitat. Community structure is correlated with the elevation, soil moisture, and percent soil ash of each 1 m² plot. Major storms reduce species richness in all three habitats. Principle coordinate analysis suggests that changes in the plant communities through time are caused by climatic events: changes in foredune vegetation are correlated with temperature and summer precipitation, interdune vegetation with storm surge, and backdune vegetation with precipitation and storm surge. We suggest that the plant communities in foredune, interdune, and backdune habitats tend to undergo succession toward particular compositions of species, with climatic disturbances pushing the communities away from these more deterministic trajectories.     

宏生态尺度上景观破碎化对物种丰富度的影响

生物多样性的地理格局及其形成机制是宏生态学与生物地理学的研究热点。大量研究表明,景观尺度上的生境破碎化对物种多样性的分布格局具有重要作用,但目前尚不清楚这种作用是否足以在宏生态尺度上对生物多样性地理格局产生显著影响。利用中国大陆鸟类和哺乳动物的物种分布数据,在100 km×100 km网格的基础上生成了这两个类群生物的物种丰富度地理格局,进一步利用普通最小二乘法模型和空间自回归模型研究了物种丰富度与气候、生境异质性、景观破碎化的相关关系。结果表明,景观破碎化因子与鸟类和哺乳动物的物种丰富度都具有显著的关联关系,其方差贡献率可达约30%—50%(非空间模型)和60%—80%(空间模型),略低于或接近于气候和生境异质性因子。方差分解结果显示,景观破碎化因子与气候和生境异质性因子的方差贡献率的重叠部分达20%—40%。相对鸟类而言,景观破碎化对哺乳动物物种丰富度的地理格局具有更高的解释率。     

Effects of landscape and history on diversification of a montane, stream-breeding amphibian

Aim The aim of this study was to understand the roles of landscape features in shaping patterns of contemporary and historical genetic diversification among populations of the Andean tree frog (Hypsiboas andinus) across spatial scales. Location Andes mountains, north‐western Argentina, South America. Methods Mitochondrial DNA control region sequences were utilized to assess genetic differentiation among populations and calculate population pair‐wise genetic distances. Three models of movement, namely traditional straight‐line distance and two effective distances based on habitat classification, were examined to determine which of these explained the most variation in pair‐wise population genetic differentiation. The two habitat classifications were based on digital vegetation and hydrology layers that were generated from a 90‐m resolution digital elevation model (DEM) and known relationships between elevation and habitat. Mantel tests were conducted to test for correlations between geographic and genetic distance matrices and to estimate the percentage variation explained by each type of geographic distance. To investigate the location of possible barriers to gene flow, we used Monmonier’s maximum difference algorithm as implemented in barrier 2.2. Results At both geographic scales, effective distances explained more variation in genetic differentiation than did straight‐line distance. The least‐cost distances based on the simple classification performed better than the more detailed habitat classification. We controlled for the effects of historical range fragmentation determined from previous nested clade analyses, and therefore evaluated the effect of different distances on the genetic variation attributable to more recent factors. Effective distances identified populations that were highly divergent as a result of isolation in unsuitable habitats. The proposed locations of barriers to gene flow identified using Monmonier’s maximum difference algorithm corresponded well with earlier analyses and supported findings from our partial Mantel tests. Main conclusions Our results indicate that landscape features have been important in both historical and contemporary genetic structuring of populations of H. andinus at both large and small spatial scales. A landscape genetic perspective offers novel insights not provided by traditional phylogeographic studies: (1) effective distances can better explain patterns of differentiation in populations, especially in heterogeneous landscapes where barriers to dispersal may be common; and (2) least‐cost path analysis can help to identify corridors of movement between populations that are biologically more realistic.     

Primary succession trajectories on a barren plain,Mount St. Helens,Washington

Questions: Have predictable relationships between environmental variables and vegetation developed in primary succession following a volcanic eruption? Has the rate of succession changed? Have vegetation trajectories converged or diverged? Location: The Abraham Plain of Mount St. Helens, Washington, USA (46°12′42″N, 122°08′27″W, elevation 1360 m), was sterilized in 1980 by a blast, scoured by lahars and buried by pumice. Method: We monitored 400 100 m² contiguous permanent plots annually (1988–2008), and classified each plot from every year into ten community types (CTs). We characterized the terrain by topography and surface features. Redundancy analysis assessed relationships between vegetation and possible explanatory variables, which included sample location. We used detrended correspondence analysis (DCA) to assess successional rates and trends. Results: Relationships between species composition and explanatory variables were only significant after 1996, when position and presence of rills became significant. By 2006, explained variation remained low (13%) but significant. Species accumulated slowly, restricted by stress and isolation. Changes in mean DCA position slowed. Composition shifted from pioneer to persistent species and vegetation became more stable with time. Species accumulated for two decades and then stabilized, while cover has continued to increase. Diversity increased and then declined slightly as dominance developed and pioneer species became less common. Conclusions: We demonstrate weak but increasingly predictable trends in species composition using environmental variables. The rate of succession slowed and trajectories formed a reticulate network of transitions dominated by divergence. Convergence was not evident because vegetation responded distinctively to minor topographic features that allowed alternative stable communities to develop.     

Ecological correlates of the non-indigenous parasitoid assemblage associated with a Hawaiian endemic moth

Understanding what ecological factors might predispose indigenous habitats to invasion by invasive species is an important aspect of conservation and invasive species management, particularly when biological control is considered for suppression of the invasive species. This study seeks to identify ecological factors that might play a role in determining the structure of the parasitoid assemblage associated with caterpillars of the endemic Hawaiian moth Udea stellata (Crambidae). Parasitoids were reared from field-collected U. stellata larvae at 18 locations. Fourteen environmental variables were measured at each site. Two multivariate analyses, principal component analysis (PCA) and partial redundancy analysis (RDA), were used to analyze the parasitoid assemblage across a range of habitats varying in environmental characteristics. The PCA analysis showed that the occurrence of some species were highly correlated, and associated with less disturbed sites, whereas other species were associated with sites of medium and high levels of disturbance. The RDA analysis showed that only three of the measured environmental variables (U. stellata density, elevation, and level of habitat disturbance) significantly explained variability in the parasitoid assemblage among sites. There was greater parasitoid species richness associated with U. stellata larvae at higher elevation sites with a lower degree of habitat disturbance by exotic vegetation. The purposely introduced parasitoid species were associated with the non-target moth at sites located at higher elevations with low levels of disturbance. Multivariate analysis has the potential to provide valuable insights into the identification of important environmental factors that mediate parasitoid assemblage structure and level of parasitism on a particular target or non-target species, and therefore facilitate identification of suitable target habitats or susceptible non-target habitats.     

Spatial heterogeneity and habitat configuration overcome habitat composition influences on alpha and beta mammal diversity

The effects of habitat fragmentation on different taxa and ecosystems are subject to intense debate, and disentangling them is of utmost importance to support conservation and management strategies. We evaluated the importance of landscape composition and configuration, and spatial heterogeneity to explain α- and β-diversity of mammals across a gradient of percent woody cover and land use diversity. We expected species richness to be positively related to all predictive variables, with the strongest relationship with landscape composition and configuration, and spatial heterogeneity respectively. We also expected landscape to influence β-diversity in the same order of importance expected for species richness, with a stronger influence on nestedness due to deterministic loss of species more sensitive to habitat disturbance. We analyzed landscape structure using: (a) landscape metrics based on thematic maps and (b) image texture of a vegetation index. We compared a set of univariate explanatory models of species richness using AIC, and evaluated how dissimilarities in landscape composition and configuration and spatial heterogeneity affect β-diversity components using a Multiple Regression on distance Matrix. Contrary with our expectations, landscape configuration was the main driver of species richness, followed by spatial heterogeneity and last by landscape composition. Nestedness was explained, in order of importance, by spatial heterogeneity, landscape configuration, and landscape composition. Although conservation policies tend to focus mainly on habitat amount, we advocate that landscape management must include strategies to preserve and improve habitat quality and complexity in natural patches and the surrounding matrix, enabling landscapes to harbor high species diversity.     

Land-use history affects understorey plant species distributions in a large temperate-forest complex,Denmark

In Europe, forests have been strongly influenced by human land-use for millennia. Here, we studied the importance of anthropogenic historical factors as determinants of understorey species distributions in a 967 ha Danish forest complex using 156 randomly placed 100-m² plots, 15 environmental, 9 spatial, and 5 historical variables, and principal components analysis (PCA), redundancy analysis (RDA) as well as indicator species analysis. The historical variables were status as ancient (1805 AD) high forest, reclaimed bogs, ≤100 m from Bronze Age burial mounds, or former conifer plantation, and stand age. The PCA results showed that the main gradients in species composition were strongly related to the explanatory variables. Forward variable selection and variation partitioning using RDA showed that although modern environment was the dominant driver of species composition, anthropogenic historical factors were also important. The pure historical variation fraction constituted 13% of the variation explained. The RDA results showed that ancient-forest status and, secondarily, reclaimed bog status were the only significant historical variables. Many typical forest interior species, with poor dispersal and a strong literature record as ancient-forest species, were still concentrated in areas that were high forest in 1805. Among the younger forests, there were clear floristic differences between those on reclaimed bogs and those not. Apparently remnant populations of wet-soil plants were still present in the reclaimed bog areas. Our results emphasize the importance of historical factors for understanding modern vegetation patterns in forested landscapes.     

Concordance between plant species,oribatid mites and soil in a Mediterranean stone pine forest

Biological interactions between above-ground and below-ground organisms are not clearly defined among communities with regard to compositional patterns. The study investigates the concordance of species assemblages between vascular plants and oribatid mites and soil chemical properties with special attention to the role of vegetation structure, i.e. tree, shrub and herbaceous cover, for biological components. Data were collected in a Mediterranean coastal Nature Reserve using sampling design based on random selection of plots with cover of stone pine (Pinus pinea L.) exceeding 15%. Agreement of distribution patterns was verified by Spearman’s rank correlation coefficient applied to pairs of matrices of plot scores by principal component analysis (plants, mites and soil) and the Mantel test. The feasible role of vegetation cover on plant and mite assemblages was tested by redundancy analysis (RDA). Significant correlations were found for biological assemblages, indicating congruent plant–mite compositional patterns. On the other hand, the hypothesis of concordance between biological communities and soil was rejected. Moreover, RDA showed that vegetation cover was a driver of both plant and oribatid mite assemblages. In particular, herbaceous cover proved to be a good proxy for the two biological communities investigated, with different taxa linked to forest clearings and to areas with denser tree cover. Our results indicate that soil features were not of primary importance for below-ground and above-ground community assemblages in the study area. In the light of our findings and ongoing threats in coastal areas, we recommend that management measures be directed at maintenance of diversified vegetation structure, which may ensure above-ground and below-ground biodiversity with diverse biological community assemblages.     

High-elevation rock outcrop vegetation of the Southern Appalachian Mountains

Abstract. Species composition patterns and vegetation-environment relationships were quantified for high-elevation rock outcrops of the Southern Appalachian Mountains, an infrequent and insular habitat in a forested landscape. Outcrops occur over a wide geographic range encompassing extensive variation in both geology and climate. Geographic-scale factors interact with site-scale factors to produce variation in vegetation among outcrops. Similarly, site-scale factors interact with micro-scale factors to produce variation in vegetation within outcrops. To provide a quantitatively-based classification of outcrop vegetation we used a TWINSPAN analysis of 154 100-m² plots. We recognized nine communities that primarily correspond to different combinations of elevation, bedrock type, geography, and moisture. Within outcrops of a single bedrock type, vegetation composition of 100-m² plots was consistently correlated with elevation and solar radiation, but relationships to soil nutrients varied with bedrock type. Both site-scale (100 m²) factors (e.g. elevation, slope, aspect, and bedrock type) and plot-scale (1-m²) microsite factors (e.g. soil depth, vegetation height, soil nutrients) were strongly correlated with species composition at the 1-m² level. Environment can be used to predict composition more effectively for 100-m² plots on a single bedrock type than either across bedrock types or at a 1-m² scale. Composition-environment relationships resemble those described for outcrop systems from other regions with pronounced topographic relief more than they do those described for the nearby but flatter and lower-elevation outcrops of the Southeastern Piedmont. There is strong spatial autocorrelation in this community, perhaps owing to dispersal limitation. Consequently, a comprehensive conservation strategy must include reservation of both a range of geologic types and a range of geographic locations.     

Influence of within‐patch habitat quality on high‐Andean Polylepis bird abundance

Habitat restoration strategies for fragmented high Andean forest landscapes must consider the influence of within‐patch habitat quality on bird abundance. I examined vegetation and bird abundance at three locations within a highly fragmented Polylepis forest landscape in the Cordillera Vilcanota, southern Peru. Across the landscape, there was significant variation in the vegetation structure of Polylepis forest patches of different size categories, especially in terms of tree girth, tree height, tree density, and canopy vegetation structure. Principal Component Analysis extracted five factors of habitat quality, which together accounted for 74.2% of the variability within 15 habitat variables. Polylepis bird species differed in their responses to habitat quality but, overall, variation in Polylepis bird abundance was not fully captured by the range of habitat quality variables. Tall, dense vegetation cover was clearly important for 11 conservation‐important species, a high density of large trees was important for 10 species and primary forest ground cover was important for eight species. Habitat quality exhibited no significant influence on the abundance of only one species –Asthenes urubambensis. The abundance of seven species was associated with lower elevation forest, but only one species was associated with higher elevation forest. Management of habitat quality in large and medium remnant forest patches throughout the Cordillera Vilcanota, particularly in the 3800–4200 m elevation range, will be a cornerstone in ensuring the persistence of the majority of conservation‐important bird species populations.     

Effects of Vegetation Traits on Habitat Preferences of Frugivorous Birds in Atlantic Rain Forest

Structural and floristic components of vegetation and fruit production were examined to evaluate the relative importance of each vegetation aspect on patterns of habitat use and to determine whether differences in degree of frugivory would affect sensitivity of birds to vegetation components. Abundances of 12 bird species were quantified in four different habitat types in the Southeastern Atlantic rain forest of Brazil using captures with mist nets. Structural and floristic traits and fruit production were sampled within plots along the mist net lines. Best explanations for the variation in species abundance were obtained by different combinations of the vegetation components (generalized linear models, Akaike information criterion; R ² mean values = 0.48, Δ AIC c = 0). Although each species had a particular preference for some vegetation variables, floristic components stood out in those relationships, generating models with a stronger explanatory capacity ( R ² > 0.40) and higher levels of empirical support (Δ AIC c = minimum values). The variation in bird sensitivities to the floristic component was associated with bird dependence on a fruit diet: there was a correlation between the explanatory capacity of models built with only floristic composition and a species' degree of frugivory (Spearman rank correlation, r = 0.66, P = 0.04), indicating that floristics had a higher effect in more frugivorous birds. For the other vegetation components, there was no clear pattern with statistical support. These results indicate that sensitivities of bird species to vegetation aspects are associated with their dependence on a fruit diet.     

Tropical tree species diversity in a mountain system in southern Mexico: local and regional patterns and determinant factors

Mechanisms explaining patterns of biodiversity along elevation gradients in tropical mountain systems remain controversial. We use a set of climatic, topographic, and soil variables encompassing regional, landscape, and local‐level spatial scales to explain the spatial variation of tree species diversity in the Sierra Madre of Chiapas, Mexico. We sampled 128 circular plots (0.1‐ha each) in four elevational bands along four elevation gradients or transects encompassing 100–2200 m. A total of 12,533 trees belonging to 444 species were recorded. Diversity patterns along the elevation gradient and the explanatory power of independent variables were dependent on spatial scale (regional vs transect) and functional group (total vs late‐successional or pioneer species). Diversity of all species and late‐successional species (1 – proportion of pioneer species) showed a constant pattern at the regional and transect scales, with low predictive power of climatic variables and/or elevation. A linear decrease in either number or proportion of pioneer species diversity was observed with increasing elevation, which was correlated with temperature, rainfall, and human disturbance trends. Total species diversity showed an increase with rainfall of the warmest quarter, indicating a regional‐level limiting effect of seasonality (drought duration). Yet the explanatory power of climatic and topographic variables was higher at the individual transect level than at the regional scale, suggesting the parallel but differential influence of evolutionary and geological history factors on diversification not so far studied to explain elevation patterns of species diversity in tropical mountain systems.     

Effects of slope and riparian habitat connectivity on gene flow in an endangered Panamanian frog, Atelopus varius

Aim Understanding how heterogeneous landscapes shape genetic structure not only sheds light on processes involved in population divergence and speciation, but can also guide management strategies to promote and maintain genetic connectivity of populations of endangered species. This study aimed to (1) identify barriers and corridors for gene flow among populations of the endangered frog, Atelopus varius and (2) assess the relative contributions of alternative landscape factors to patterns of genetic variation among these populations in a hypothesis testing framework. Location This study took place in western Panama and included all nine of the remaining known populations of A. varius at the time of study. Methods The influence of landscape variables on gene flow among populations was examined by testing for correlations between alternative landscape‐resistance scenarios and genetic distance. Fifteen alternative hypotheses about the influence of (1) riparian habitat corridors, (2) steep slopes, and (3) climatic suitability on patterns of genetic structure were tested in a causal modelling framework, using Mantel and partial‐Mantel tests, along with an analysis of molecular variation. Results Only the hypothesis attributing resistance to dispersal across steep slopes (genetic isolation by slope distance) was fully supported by the causal modelling approach. However, the analysis of molecular variance and the paths of least‐slope among populations suggest that riparian habitat connectivity may influence genetic structure as well. Main conclusions These results suggest that patterns of genetic variation among A. varius populations are affected by the slope of the landscape such that areas with steep slopes act as barriers to gene flow. In contrast, areas of low slope, such as streams and mountain ridges, appear to be important corridors for gene flow, especially among high elevation populations. These results engender important considerations for the management of this critically endangered species.     

Congruence between floristic patterns of trees and lianas in a southwest Amazonian rain forest

The congruence in floristic patterns between different life-forms of woody plants remains poorly understood in tropical rain forests. We explored whether the floristic patterns of woody plants, divided into small trees 2.5–10 cm dbh, large trees ≥10 cm dbh, and lianas ≥2.5 cm dbh were associated with each other or with patterns in soil properties, elevation, and geographical distances between sample plots. We also tested whether ecological amplitudes in relation to environmental variables differed among the plant groups. Trees and lianas were inventoried in 44 0.1-ha plots, distributed among three lowland and two submontane sites in the Madidi National Park, Bolivia. Soil samples were analysed for physico-chemical properties. Floristic differences between sites (as measured with each plant group separately) yielded significant Mantel correlations with each other, and with pH, Ca, Mg, elevation and geographical distance. Mantel correlations with edaphic distances were higher for large trees than small trees, but for Mantel correlations with geographical distance the situation was reversed. Environmental and geographical distances explained 31% of the variation in floristic differences for large trees, 22% for small trees, and 10% for lianas. The ecological amplitudes of lianas were wider than those of all trees for pH, Mg and elevation. The amplitudes of the two size classes of trees did not differ. In principal coordinates ordination, the three plant groups produced similar overall floristic patterns that were explainable by environmental factors.     

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.