Showing papers in "Applied Vegetation Science in 2014"

Vegetation succession in restoration of disturbed sites in Central Europe: the direction of succession and species richness across 19 seres

Abstract: Questions (1) How do seres differ with respect to vegetation changes? (2) What are the directions of succession? (3) How do species numbers change? (4) How do target species, i.e. those typical of natural and semi-natural vegetation, participate in succession? (5) Are spontaneously developed successional stages acceptable from the point of view of ecosystem restoration? Location Extracted peatlands, bulldozed sites in forests destroyed by air pollution, an emerged bottom of a water reservoir, corridors of former Iron Curtain, artificial fishpond islands and barriers, sedimentary basins, spoil heaps from mining, stone quarries, forest clearings, road verges, sand and gravel-sand pits, ruderal urban sites, river gravel bars and abandoned arable fields, located in various parts of the Czech Republic in Central Europe. Methods Phytosociological releves were recorded in 10–25 m2 plots located in the centre of representative successional stages defined by their age, ranging from 1 to 100 yrs. In total, we obtained 2392 vegetation samples containing 951 species. We performed DCA ordination to compare 19 seres. Desirable target species were considered as those representing (semi)-natural vegetation and all Red List species. Results The seres studied are more similar in their species composition in the initial and early stages, in which synathropic species prevail, than in the later stages when the vegetation differentiates. This divergence is driven mainly by local moisture conditions. In most cases, succession led to woodland, which usually established after ca. 20 yrs. In very dry or wet places (with limited presence of woody species) open vegetation developed, often highly valuable from the restoration and conservation point of view. The total number of species and the number of target species increased in the majority of seres with successional age. Conclusions The vegetation in the sites studied formed a continuum along a moisture gradient and by successional age. The individual seres largely overlapped in their species composition; the sere identity was not significant. Spontaneous succession usually proceeded towards woodland, except at very dry or wet sites, and generally appeared to be an ecologically suitable way of ecosystem restoration of disturbed sites because target species became dominant over time.

Assessing vegetation change using vegetation-plot databases: a risky business

Abstract: Aim: Data from vegetation plots can be used for the assessment of past vegetation change in three ways: (1) comparison of old and new records from permanent plots established for vegetation monitoring; (2) revisiting historical phytosociological plots and subsequent comparison of old and new records; (3) comparison of large sets of old and new phytosociological records from the same area but different plots. Option (3) would be the cheapest in regions where large vegetation-plot databases are available, but there is a risk of incorrect results due to a spatial mismatch of old and new plots. Here we assess the accuracy of such analyses. Methods: We used three data sets of permanent plots from Czech mountain bogs and Dutch oak forests and heathlands to quantify vegetation change. We selected subsets to simulate analyses based on (1) data from permanent plots or revisited phytosociological plots, i.e. containing old and new records from the same plots, (2) vegetation-plot databases with old and new records from different, randomly selected sites, and (3) vegetation-plot databases with old and new records from different but close sites. We repeated each subset selection 1000 times and analysed vegetation change in each of the three data sets and each variant of subset selection using permutational multivariate analysis of variance. Results: For data sets with no actual vegetation change, analyses of some subsets simulating vegetation-plot databases incorrectly suggested significant changes. For a data set with real change, a change was detected in analyses of simulated vegetation-plot databases, but in several cases it had a different direction or magnitude to the real change. Conclusions: The assessment of vegetation change using vegetation-plot databases should be either avoided or interpreted with extreme caution because of the risk of incorrect results. Analyses such as these may be used to propose hypotheses about past vegetation change, but their results should not be considered valid unless confirmed using more reliable data. In many contexts, re-visitation studies of historical phytosociological plots may be the best strategy to assess past vegetation change, while new networks of carefully stratified permanent plots are preferable for monitoring future change.

Unmanned aircraft systems help to map aquatic vegetation

Abstract: Questions Do high-resolution (sub-decimetre) aerial images taken with unmanned aircraft systems (UASs) allow a human interpreter to recognize aquatic plant species? Can UAS images be used to (1) produce vegetation maps at the species level; and (2) estimate species abundance? Location One river and two lake test sites in northern Sweden, middle boreal sub-zone. Methods At one lake and at the river site we evaluated accuracy with which aquatic plant species can be identified on printouts of UAS images (scale 1:800, resolution 5.6 cm). As assessment units we used homogeneous vegetation patches, referred to as vegetation stands of one or more species. The accuracy assessment included calibration and validation based on field controls. At the river site, we produced a digital vegetation map based on an UAS orthoimage (geometrically corrected image mosaic) and the results of the species identification evaluation. We applied visual image interpretation and manual mapping. At one of the lake sites, we assessed the abundance (four-grade scale) of the dominating Phragmites australis and produced a cover map. Results We identified the species composition of vegetation stands at the lake and the river site with an overall accuracy of 95.1% and 80.4%, respectively. It was feasible to produce a digital vegetation map, albeit with a slight reduction in detail compared to the species identification step. At the site for abundance assessment, P. australis covered 20% of the total lake surface area, and 70% of the covered area had cover ≤25%. Conclusions The tested UAS facilitates lake and river vegetation identification and mapping at the species level, as well as abundance estimates.

Secondary succession in sandy old-fields: a promising example of spontaneous grassland recovery

Abstract: Question Based on the spontaneous vegetation development of old-fields in the Nyirseg and Kiskunsag sand regions (Hungary), we aimed to answer the following questions using the chronosequence method: (1) how do the proportions of different functional groups change during succession; (2) which target species establish successfully in the old-fields during the course of succession; and (3) how successful is spontaneous succession in the recovery of target grasslands? Location Two sand regions of the Great Hungarian Plain: (1) the Nyirseg sand region (East Hungary, acidic sand, moderately continental climate) and the Kiskunsag (Central Hungary, calcareous sand, continental climate) Methods Altogether 24 old-fields were classified into young (<10-yr-old), middle-aged (10–20-yr-old) and late-succession (20–40-yr-old) old-fields; four fields in each age category For baseline vegetation reference, three open and three closed sand grassland stands in both regions were sampled in the vicinity of the old-fields The percentage cover of vascular plants was recorded in five 2 × 2-m plots in each field, in early May and late June 2012 We used life forms, clonal spreading traits and Ellenberg indicator values for nutrients in the analysis Species of Festuco-Brometea class were considered as target species Results The cover of hemicryptophytes and geophytes increased, the cover of short-lived species decreased with time Cover of species without clonal spreading ability decreased, while cover of species with clonal spreading ability increased with increasing field age The cover of invasive species decreased with increasing field age The majority of target species had established already in the young and middle-aged old-fields, although their cover was significantly higher in the two older age groups Conclusion Spontaneous succession can be a vital option in recovery of sand grassland vegetation in Central Europe; the majority of the species pool of sandy grasslands can be recovered in the first 10–20 yrs However, the success of grassland recovery can be strongly influenced by the surrounding species pool and can be slow if seed dispersal is limited Spontaneous succession is most promising when the target species of grasslands immigrate at the very beginning of the succession, within the first few years

Use of multiple criteria in an ecological assessment of a prairie restoration chronosequence

Abstract: Was ecological fidelity (structure/composition, function and durability) restored in a series of tallgrass prairie restorations? Which factors influenced success? Can success be assessed in prairie restoration using indices of ecological fidelity? Nachusa Grasslands in Lee and Ogle Counties, Illinois, USA. To assess restoration of ecological fidelity, mean coefficient of conservatism (Mean C), floristic quality index (FQI), above-ground net primary productivity (ANPP), soil bulk density, total soil nitrogen (N) and total soil carbon of 19 restoration sites were recorded from 20 × 50 m modified Whittaker plots across a chronosequence, and compared to benchmark values acquired from both the literature and field observation of remnant prairies. Following assessment, multiple factors were examined through correlation analysis, Akaike's information criterion and multiple regression analysis to determine the relationship of these factors to restoration success. All restoration sites attained the benchmark value for Mean C, while only four attained the benchmark value for FQI. Mean C and FQI both decreased across the chronosequence. Frequency of prescribed fire and soil bulk density had significant positive relationships to Mean C. FQI was best explained by the FQI value of the seed mix sown. Thirteen restoration sites attained the benchmark value for ANPP, which remained stable across the restoration chronosequence. Abundance of exotic species and soil drainage had a negative relationship to ANPP. Few restoration sites attained benchmark values for soil bulk density, total N and total carbon, and none of the sites showed a trajectory towards benchmark values across the chronosequence. Our study demonstrates that high-quality seed mixes may aid in establishing prairie restorations with high scores of floristic quality. However, restoration of vegetation does not guarantee the successful restoration of ecological function. Long-term monitoring is needed to more effectively assess durability and the multiple factors that influence restoration quality. Overall, the three components of ecological fidelity related to structure/composition, function and durability provide a useful framework to assess restoration success and guide management. Our study can serve as a model for future research and assessment of restoration success. A chronosequence of restored prairies was evaluated to determine if benchmark levels of ecological fidelity had been achieved. Restoration success varied depending on the ecological attribute examined, but many prairies, especially those planted most recently with species-rich seed mixes, displayed high levels floristic quality. Our study can serve as a model for future research and assessment of restoration success.

Fifty years of tree line change in the Khibiny Mountains, Russia: advantages of combined remote sensing and dendroecological approaches

Abstract: Questions Tree line ecotone regions are expected to respond swiftly to climate changes. In this paper, remote sensing- and ground-based tree population data are used to examine past and on-going changes of the tree line ecotone in a sub-arctic region characterized by precipitation increase. Questions addressed are: (1) at what rate has the tree line ecotone changed since the mid-20th century; (2) can specific temporal dynamics be identified; and (3) do combined remote sensing and tree population analyses add essential knowledge for the interpretation of tree line changes? Location Khibiny Mountains, Kola Peninsula, northwest Russia. Methods Aerial photos from 1958, high-resolution satellite imagery from 2006/2008 and age structure data for dominant tree line species (birch and pine) were used to analyse rate of change and temporal and species-specific tree line recruitment patterns. This was accomplished using digital elevation models, resolution-merging procedures, visual interpretation and dendroecological methods. Results Mean tree line advance for birch and pine was recorded as 29 and 27 altitudinal metres (0.6 and 0.5 m·yr−1), respectively. The advance was accompanied by an apparent infilling of pre-established tree populations and by recruitment beyond the tree line. Evident increased recruitment occurred in the late 1980s for birch and in the 1970s and 1990s for pine. Establishment showed no strong correlations with climate variables, but the importance of non-growing season variables was indicated. Conclusions The recorded tree line advance is modest compared to global model predictions for advance at high latitudes, but in accordance with results from a number of high-latitude areas. Concomitantly, the apparent increased recruitment is indicative of a more rapidly advancing tree line zone. Studies combining remote sensing and ground-based data minimize the risk of under- or overestimating potential tree line advance. Low detectability of small seedlings and saplings by remote sensing can cause underestimation of the current potential, while ground-based data used alone can overestimate potential advance. A balance between the two approaches is beneficial and enhances quality in production of change scenarios related to high latitudinal tree line areas at local to large regional scales.

Restoration of Neotropical grasslands degraded by quarrying using hay transfer

Abstract: Abbreviations DSt = degraded stony substrate; DSa = degraded sandy substrate; DL = degraded Latosol substrate; Ca = pristine campos arenosos; Cp = pristine campos pedregosos; G = with geotextile; g = without geotextile; HCa = hay from donor campos arenosos; HCp = hay from donor campos pedregosos; h = without hay; GLM = Generalized linear model Nomenclature Lista de Esp ecies da Flora do Brasil (2012) Abstract Aim: The campos rupestres are species-rich tropical mountain grasslands in southeast Brazil that are threatened by mining and quarrying. Eight years following a strong disturbance (i.e. quarrying for gravel exploitation during the asphalting of highway MG-010), spontaneous succession did not occur on degraded areas. This study was therefore designed to test the restoration technique of hay transfer as a means of enhancing seed dispersal from the reference ecosystems to the degraded areas. Methods: Nine degraded areas representing three kinds of substrate (latosol, sandy and stony) were selected. Hay transfer was carried out using hay collected in two kinds of grassland (i.e. campos arenosos and campos pedregosos) year-round in 2010, in order to maximize the seed pool. The collected hay was distributed on 40 cm 9 40 cm quadrats among the three types of substrate, with and without geotextile, according to the following protocol: hay from campo arenoso grasslands was spread on all types of substrate, while hay from campo pedregoso grasslands was used on stony substrate only. Results: Few seedlings emerged within 14 mo of the treatment application, despite the large number of seeds contained in the hay, indicating that hay transfer may not be a useful method for restoring degraded areas of campos rupes-tres. The seedlings emerging on the degraded areas mainly belonged to ruderal species. Therefore, we suggest that, although poor soil conditions could limit seedling establishment, germination issues of the campo rupestre species are the first limitation for restoring degraded campos rupestres using hay transfer. Conclusion: Our results highlight the inherent difficulty in restoring degraded areas of campos rupestres; their protection must be made a high conservation priority.

Combining ecological, social and technical criteria to select species for forest restoration

Abstract: Question: How to evaluate and integrate relevant ecological, social and techni- cal criteria to select species to be introduced in restoration projects of highly diverse ecosystems such as tropical riparian forests. Location: Riparian forest, Marqude Comillas municipality, southeast Mexico (16°54'N, 92°05'W). Methods: We proposed a 'species selection index' (SSI) using five independent criteria related to ecological, social and technical information. SSI targeted spe- cies that (1) are important in the reference forest; (2) are less likely to establish following disturbance; (3) are not specific to a particular habitat; (4) are socially accepted; and (5) their propagation requires a reasonable time and financial investment. SSI may range between zero and 50, with higher values meaning higher potential for restoration purposes. Results: Out of a local pool of 97 species, we identified 30 target tree species that together represented >60% of total importance value index in the reference riparian forests. SSI averaged 28.3 1.0 over the studied species, suggesting that species with high values are not frequent. For 20 species, reintroduction by means of active forest restoration was deemed necessary. Species that estab- lished through natural regeneration, following secondary regrowth, had lower social value among local farmers. Nearly half of the identified species showed technical constraints for easy propagation and seeding. Conclusions: The proposed procedure is useful for selecting species to initiate forest restoration projects and of other woody ecosystems that harbour high bio- diversity, and is suitable for several stakeholders interested in restoration.

Mapping the local variability of Natura 2000 habitats with remote sensing

Abstract: Questions Can we map both discrete Natura 2000 habitat types and their floristic variability using multispectral remote sensing data? How do these data perform compared to full range imaging spectroscopy data? Which spectral and spatial characteristics of remote sensing data are important for accurate mapping of habitats and their variability? Location A mire complex in Bavaria, southern Germany. Methods To compare the performance of imaging spectroscopy and multispectral remote sensing data, airborne spectroscopy data (AISA Dual) were spectrally and spatially resampled to the characteristics of two state-of-the-art multispectral sensors (RapidEye and Sentinel-2), resulting in three data sets with different spectral and spatial resolution. Based on the three data sets, we used a combination of field surveys, ordination techniques (non-metric multidimensional scaling), as well as regression and classification techniques (Random Forests) to derive maps of the distribution of Natura 2000 habitat types and their compositional variability. Subsequently, we analysed effects of the spatial and spectral image resolution and spectral coverage on the mapping performance. Results Mire habitat types and their floristic composition could be accurately mapped with multispectral remote sensing data. In the case of accentuated floristic differences between habitats, the fits of the models for the three sensors differed only marginally. These effects and the importance of the spatial resolution are discussed. Conclusions The results are encouraging and confirm that multispectral data may allow the combined mapping of discrete habitats and their local variability. Still, questions with respect to the transferability of the approach to habitat types with less pronounced spectral differences, and with regard to bridging the gap between fine-scale vegetation records and coarse resolution imagery remain open.

Impact of mid‐successional dominant species on the diversity and progress of succession in regenerating temperate grasslands

Abstract: Questions (i) Which species dominate mid-successional old-fields in Hungary? How does the identity of these species relate to local (patch-scale) diversity and to the progress of succession? (ii) Which species have the strongest negative impact on diversity in spontaneous old-field succession and what generalizations are possible about traits of these species? (iii) Are these species dominant or subordinate components in mature target communities? (iv) Do native or alien species have stronger effects on the diversity and progress of succession? Location Abandoned agricultural fields (abandoned croplands, orchards and vineyards) at various locations throughout Hungary. Methods Vegetation patterns on 112 old-fields, in 25 sites varying in soil and climatic conditions, topography, landscape contexts and land-use histories were sampled. Most old-fields had appropriate seed sources in the immediate vicinity, i.e. natural or semi-natural grasslands (meadows steppes, closed and open sand steppes) as source and target habitats. Age of abandoned fields ranged from 1 to 69 yr, but most sites were between 15 and 60 yr. The cover of vascular plant species (%) was estimated in 2 × 2-m plots. Relationships between diversity, progress of succession (similarity to target communities) and identity of dominants were tested. Results A small portion of successional dominants (eight species) had strong negative impacts on diversity. These species belonged to Poaceae, Asteraceae and Fabaceae. Most of these species were wind-pollinated, and capable of lateral vegetative spread. Dominant species varied in size and had, on average, a low requirement for N but a high requirement for light. With one exception, Solidago gigantea, they were native to the Hungarian flora. Significant differences were found among the impact of successional dominants when dominant species were grouped according to their original role (dominants or subordinates) in natural communities. The overall effect of species identity was also significant. Bothriochloa ischaemum was identified as the species with the strongest negative effect on species diversity. Conclusions Our results suggest that mid-successional dominant species differ in their impact on diversity and progress of succession. Mid-successional plots dominated by alien species, or by native species that were originally subordinate in natural communities, regenerate less successfully and may temporarily arrest succession. Therefore, early colonization of native dominants should be enhanced with restoration measures.

Response of community‐aggregated plant functional traits along grazing gradients: insights from African semi‐arid grasslands

Abstract: Questions Plant communities fulfil key functions in the ecosystem, which can be characterized by their plant functional traits. In functional ecology, plant communities are considered to hold a set of trait attributes reflecting a specific plant strategy adapted to persist in the environment to which they are exposed. In semi-arid grasslands of the Republic of South Africa, we addressed the following questions: how are community-aggregated plant functional traits (CPFT) shaped by grazing gradients; which plant strategies are associated with the response of CPFTs; and are environmental factors, such as soil properties and grazing management, interrelated with the functional response of vegetation to grazing gradients? Location Semi-arid grasslands close to Thaba Nchu, Free State (Republic of South Africa). Methods Piosphere transects from a water point into the field were established to portray grazing gradients on two communal grazing areas with continuous grazing and two commercial farms with rotational grazing. Along each transect, six plots (5 × 5 m) were evenly distributed. The trait–transect sampling was applied to record 12 CPFT related to light capture and forage quality. A redundancy analysis was performed to derive relationship between CPFTs, grazing gradients and environmental conditions. Results Grazing intensity decreased along piosphere transects, from the water point into the field. Most CPFTs responded to this decreasing gradient of grazing intensity and so allowed derivation of trait syndromes that clearly reflect plant strategies of ruderal and competitive vegetation. Close to water points, plants had higher nitrogen concentrations, fewer cell wall components and higher specific leaf area, hence light capture might be faster and more efficient per leaf area and leaf mass. Plant communities exposed to intensive grazing were well adapted to defoliation, trampling and nutrient accumulation through fast growth rates and a quick return strategy. Conclusions In the sacrifice zone around water points, there is an ecological niche for vegetation communities exhibiting a strategy of fast growth, which is well adapted to intense and frequent grazing and is also associated with forage of high nutritional quality.

How to develop native plant communities in heavily altered ecosystems: examples from large‐scale surface mining in Germany

Abstract: Questions Does site alteration caused by mining impede spontaneous colonization of native species assemblies to the advantage of neophytic species at the landscape unit and plant community scale? To what extent can mined site conditions support the establishment of rare plant species assemblies that are locally novel but of regional conservation value? What effects have dispersal limitation and stochasticity on spontaneous succession trajectories and how does community structure and composition differ between actively restored sites and ancient grasslands? Location Central German Lignite Mining District. Methods We used comprehensive databases to compare floristic composition in mined sites and their surroundings. At the community level, we choose a chronosequence approach to analyse spontaneous colonization of target species into mined sites and the development of calcareous grasslands, compared to ancient as well as actively restored grasslands. Statistical analyses involved Mann–Whitney U-test, GNMDS and binary logistic regression. Results The proportion of neophytes in spontaneously developing mined sites was low and similar to the unmined surroundings at the landscape unit as well as plant community scale. Mined sites harbour an impressive number of native and even rare species. However, plant communities lacking immigration of target grasses typical for calcareous grasslands lead to divergences regarding species and functional composition compared to ancient calcareous grasslands. In contrast, plots with actively introduced target species at the onset of succession show a generally more rapid trajectory towards ancient grasslands. The probability of establishing in mined sites increases with higher abundance of calcareous dry grassland species in the vicinity, indicating the importance of high propagule pressure in a landscape context, whereas long-distance dispersal traits were significant, but less important. Conclusions Spontaneous succession supports the development of native plant communities. However, because of propagule limitation, colonization processes may lead to novel species assemblies. While dispersal stochasticity during spontaneous succession results in a higher γ-diversity, species introduction supports faster trajectories towards desired reference states providing important ecosystem services such as erosion control. The key decision of whether to rely on spontaneous succession or not mainly depends on the surrounding landscape matrix and history, the need for erosion control and/or rapid compensation for lost habitats.

Structural and floristic diversity of mixed tropical rain forest in New Caledonia: new data from the New Caledonian Plant Inventory and Permanent Plot Network (NC-PIPPN)

Abstract: Aims To describe the structural and floristic diversity of New Caledonian mixed tropical rain forest and investigate its environmental determinants. Location New Caledonia (SW Pacific), a biodiversity hotspot. Methods Structural (stem density, basal area) and floristic characteristics (composition, species richness and dissimilarity) were investigated along environmental gradients (elevation, rainfall and slope) on different substrates (ultramafic and non-ultramafic) through the New Caledonian Plant Inventory and Permanent Plots Network (NC-PIPPN, 201 plots each measuring 20 m x 20 m). Results A total of 28,640 trees (DBH ?5 cm) belonging to 749 species, 240 genera and 92 families were inventoried in the NC-PIPPN. The New Caledonian mixed rain forest studied was characterized as having high stem density, basal area and species richness, and many small stems (60% of the trees 0.70). The presence of ultramafic (UM) and non- ultramafic substrates (non-UM) combined with altitudinal and rainfall gradients were the main drivers of floristic dissimilarity, whereas the effect of geographic distance between the plots was surprisingly low. Floristic dissimilarity was very high between UM and non-UM substrates from species up to family level. About 75% of the species occurred on a single substrate type. The mixed rain forest on UM and non-UM substrates differed in floristic composition but not in structure. Conclusions NC-PIPPN proved to be an effective tool for investigating the woody species richness of New Caledonia as containing ca. 46% of its non-herbaceous species. However, the network's design, and more specifically its small plots, restricts its capacity to capture beta diversity and forest structure. High species richness and floristic dissimilarity confirm that New Caledonian mixed rain forest is exceptionally rich. (Resume d'auteur)

Changes in forest structure, fuels and potential fire behaviour since 1873 in the Lake Tahoe Basin, USA

Abstract: Questions: What were the characteristics of pre-Anglo-American (reference) forests before logging, grazing and fire exclusion, and how have they changed? What were the structural characteristics of canopy and surface fuels and potential fire behaviour in reference forests, and how do they compare to contemporary forests? How might information from reference conditions be used to inform current restoration and management practices? Location: Lake Tahoe Basin in the Sierra Nevada, California and Nevada, USA. Methods: Tree species composition, size structure, basal area, density, surface and canopy fuels, and potential fire behaviour were quantified for reference and contemporary conditions in 32 stands. This was accomplished by integrating field measurements and dendroecological techniques with vegetation and fire behaviour simulation models. Results: Contemporary Jeffrey pine and mixed conifer forests had more trees, more basal area, smaller trees and a different size structure than the reference forest. Contemporary red fir and lodgepole pine forests also had more and smaller trees, but basal areas were similar to the reference. Red fir forests also shifted in composition towards lodgepole pine. Vegetation and fire models indicate that contemporary Jeffrey pine and mixed conifer forests have higher flame length, rates of spread, lower crowning and torching indices, and more passive crown fire than the reference forests. In contrast, contemporary red fir and lodgepole pine forests only had lower crowning and torching indices, and flame length and rate of spread were only higher with extreme weather and high surface fuel load. Conclusions: Contemporary Jeffrey pine and mixed conifer forests deviate the most from the reference, and restoration objectives for these forests should emphasize density and basal area reduction of smaller diameter stems. Restoration objectives for red fir should shift species composition and reduce basal area by thinning smaller diameter lodgepole pine. For lodgepole pine forests, restoration objectives should include reduction of density and basal area of smaller diameter stems. Fire or other surface fuel treatments will be needed in all the forests to maintain lower fuel loads, albeit at different time intervals.

Twentieth century shifts in abundance and composition of vegetation types of the Sierra Nevada, CA, US

Abstract: Questions Has tree density changed consistently across vegetation types? Do changes in component species correspond with changes across vegetation types? Do patterns of changes suggest potential drivers of change? Location Northern two-thirds of the Sierra Nevada, CA, USA, ca. 45 000 km2. Methods Using two data sets that cover the span of elevations and land jurisdictions in the study area, we classified 4321 historical plots and 1000 modern plots into nine broad groups of vegetation types that are widely used by land managers and researchers in the region. We compared tree density and composition between historical and modern plots across and within these nine types. Results In the modern data set, tree density was significantly higher in eight of nine vegetation types. Total density was significantly higher in modern plots for all west slope types, especially for montane hardwood, where modern forests are 128% denser, and mixed conifer forests, which are 69% denser. Relative density of component species was also very different between data sets in these forests, and suggests a shift in dominance toward shade-tolerant conifers and evergreen oaks. Fire suppression is likely a driving factor in these types but density was also significantly higher in high-elevation types such as sub-alpine forest (+20%), where neither fire suppression nor logging have had major impacts on structure. East slope forest types (eastside P. jeffreyi forest and pinon-juniper woodland) were very similar in both modern and historical data sets, with no significant differences in density or composition. Conclusion West slope forest types, especially montane hardwood and mixed conifer forest, appear the most altered types of the mountain range. These types are more productive but have also been subject to greater disturbance than high-elevation and east slope forest types. Climate change may also be driving changes across the study area. Species such as Quercus chrysolepis and Calocedrus decurrens, which have each increased markedly in abundance, appear well positioned to dominate in the near future, especially under continued fire suppression and a warmer climate.

The natural regeneration of calcareous grassland at a landscape scale: 150 years of plant community re-assembly on Salisbury Plain, UK

Abstract: Questions: What is the time-scale for natural regeneration of calcareous grassland? Is this time-scale the same for individual plant species, plant community composition and functional traits? Location: Defence Training Estate Salisbury Plain, Wiltshire, UK. Methods: We investigated the rate of natural regeneration of species-rich calcareous grassland across a 20 000-ha landscape. We combined a large-scale botanical survey with historic land-use data (6–150 yrs before present) and examined differences between grassland age classes in the occurrence of individual plant species, plant community composition and plant community functional traits. Results: Many species showed a significant association with grasslands over 100 yrs old. These included the majority of those defined elsewhere as calcareous grassland indicators, although some appeared on grasslands <10 yrs old. Plant community composition showed increasing similarity to the oldest grasslands with increased grassland age, with the exception of very recently ex-agricultural grasslands. Most functional traits showed clear trends with grassland age, with dispersal ability differing most strongly between recent and older grasslands, whilst soil fertility and pH tolerance were more influential over longer time-scales. Conclusions: Even in a well connected landscape, natural regeneration to a community resembling ancient calcareous grassland in terms of functional traits and plant community composition takes over a century, although changes at the level of individual species may occur much earlier. These findings confirm the uniqueness of ancient calcareous grassland. They also suggest that the targets of re-establishment efforts should be adjusted to account for the likely time-scale of full community re-assembly.

Drought‐induced woody plant mortality in an encroached semi‐arid savanna depends on topoedaphic factors and land management

Abstract: Keywords Climate change; Climatic variability; Dieback; Flash drought; Grazing;Juniperus; Legacy effect; Rangelands; Scale; State transition; Vegetation change; Woody encroachment Abstract Questions: How do recent patterns of drought-induced woody plant mortality in Texas semi-arid savanna compare to the extended drought of the 1950s? Does the relative composition of the woody plant community shift ubiquitously across the landscape following woody plant mortality and dieback or are shifts dependent on differences among species, soils, land use and plant demography?

Species distribution modelling for plant communities: stacked single species or multivariate modelling approaches?

Abstract: Aim Landscape management and conservation planning require maps of vegetation composition and structure over large regions. Species distribution models (SDMs) are often used for individual species, but projects mapping multiple species are rarer. We compare maps of plant community composition assembled by stacking results from many SDMs with multivariate maps constructed using nearest-neighbor imputation. Location Western Cascades ecoregion, Oregon and California, USA. Methods We mapped distributions and abundances of 28 tree species over 4,007,110 ha at 30-m resolution using three approaches: SDMs using machine learning (random forest) to yield: (1) binary (RF_Bin); (2) basal area (abundance; RF_Abund) predictions; and (3) multi-species basal area predictions using a nearest-neighbor imputation variant based on random forest (RF_NN). We evaluated accuracy of binary predictions for all models, compared area mapped with plot-based areal estimates, assessed species abundance at two spatial scales and evaluated communities for species richness, problematic compositional errors and overall community composition. Results RF_Bin yielded the strongest binary predictions (median True Skill Statistics; RF_Bin: 0.57, RF_NN: 0.38, RF_Abund: 0.27). Plot-scale predictions of abundance were poor for RF_Abund and RF_NN (median Agreement Coefficient (AC): −1.77 and −2.28), but strong when summarized over 50-km radius tessellated hexagons (median AC for both: 0.79). RF_Abund's strength with abundance and weakness with binary predictions stems from predicting small values instead of zeros. The number of zero value predictions from RF_NN was closest to counts of zeros in the plot data. Correspondingly, RF_NN's map-based species area estimates closely matched plot-based area estimates. RF_NN also performed best for community-level accuracy metrics. Conclusions RF_NN was the best technique for building a broad-scale map of diversity and composition because the modelling framework maintained inter-species relationships from the input plot data. Re-assembling communities from single variable maps often yielded unrealistic communities. Although RF_NN rarely excelled at single species predictions of presence or abundance, it was often adequate to many (but not all) applications in both dimensions. We discuss our results in the context of map utility for applications in the fields of ecology, conservation and natural resource management planning. We highlight how RF_NN is well-suited for mapping current but not future vegetation.

The role of native woody species in the restoration of Campos Rupestres in quarries

Abstract: Questions Can shrub and tree seedlings be reintroduced into an extremely harsh environment through transplantation? Does the growth strategy of species affect their survival? What factors influence transplantation success? Do transplanted species influence their immediate vicinity, e.g. promote native species colonization? Location Campos Rupestres, Minas Gerais, Brazil. Methods We studied the reintroduction of four native tree and 14 native shrub species. Their transplantation success (survival, growth and reproduction) and their impact on their immediate vicinity (understorey composition, soil surface indicators, e.g. cover of moss, biological crust, bare ground, litter, herbaceous cover and soil characteristics) were assessed 4.5 yrs after transplantation. Results While some transplanted species had low survival ( 78% 4.5 yrs after transplantation. Plant growth was barely correlated with transplantation success in such a harsh environment. Transplanted species did not influence soil and understorey plant composition but significantly impacted soil surface indicators. The shrub species with higher survival usually allowed establishment of an understorey herbaceous cover, which may increase soil erosion control. This is also true for some species for which the survival was <40%: Diplusodon orbicularis (survival: 39%) and Lavoisiera campos-portoana (37%). Crown volume had a direct effect on light reaching the soil (e.g. Jacaranda caroba or Collaea cipoensis had a less dense canopy more permeable to light, allowing the development of understorey species). On the other hand, crown volume was positively correlated with amount of litter: Fabaceae, e.g. Chamaecrista semaphora and Mimosa foliolosa, had denser canopy and produced a thick layer of litter, limiting herbaceous species establishment. Three tree species (Enterolobium ellipticum, Kielmeyera petiolaris and Zeyhera tuberculosa) neither had high survival nor facilitated establishment of herbaceous cover. The layout and spacing of species and individuals must thus be considered carefully to ensure recolonization by native shrub and herbaceous species. Conclusion This study demonstrates the practical efficiency of using some species native to harsh tropical ecosystems, e.g. Campos Rupestres, to restore quarry ecosystems in terms of their transplantation success, effects on both the establishment of herbaceous species and soil conservation.

Does fire induce flowering in Brazilian subtropical grasslands

Abstract: Questions We aimed to analyse the effect of fire on flowering in subtropical grasslands, by addressing the following questions: will fire history affect flowering? If yes, do fire feedbacks influence flowering or is it just the removal of above-ground biomass? Are there differences in burned and mowed plots? Location Subtropical grasslands in Southern Brazil (30°03′S, 51°07′W). Methods We established plots in areas with different fire histories: 30 d (30 plots: five replicates), 1 yr (14 replicates), 3 yr (30 plots: five replicates) since the last fire, in experimentally burned and mowed plots (14 replicates each). We counted the number of flowering species, as well as the number of flowering stalks. Results Graminoid species flowered in highest numbers 1 yr after fire, whilst forbs had more species flowering just after fire, indicating different reproductive strategies in post-fire environments. Mowing was not as efficient as fire in stimulating flowering. Finally, the different functional groups showed different flowering responses to time since last fire and to the different types of management. Conclusions Our results show fire stimulated flowering. Although mowing can be a good alternative for maintaining plant diversity, our study showed that this practice is not as efficient as fire in stimulating flowering. However, fire season should be noted as a limiting factor to the recovery of C3 grasses in these subtropical grasslands, and annual burns may be harmful to C4 grasses, since they delay their flowering to the next post-fire growing season.

Functional diversity of ground‐layer plant communities in old‐growth and managed northern hardwood forests

Abstract: Questions: Do ecological sorting processes and functional diversity of forestground-layerplantcommunitiesvaryamong mature(65–85-yr-old)even-aged,managed uneven-aged and old-growth forest stands? How does functionaldiversityrelatetoenvironmentalvariableswithinstands?Location: Northern temperate deciduous forests of Wisconsin and the UpperPeninsulaofMichigan,USA.Methods: Ground-layer species cover and light availability were measured ateach of four old-growth, even-aged second-growth, and managed uneven-agedstands (n = 12 stands total). We used mixed-effect models and fourth-corneranalysis to assess relationships among forest structure, species traits and thethree components of functional diversity (functional richness, evenness, diver-gence)basedon32leaf,reproductiveandwholeplanttraitsfrom111species.Results: We identified differences in leaf phenology and morphology, life formand dispersal among stand types at the community level. Ground-layer plantcommunities of even-aged and uneven-aged stands were at opposite ends of aspectrumofstrategies aimedat toleratingstressfulvscompetitiveenvironments,respectively. In even-aged stands, communities were characterized by speciesadapted to relatively dark and closed conditions (heavy-seeded tree saplings,spring ephemerals). In contrast, managed uneven-aged stands were character-ized by species with potential for quick returns on investment of nutrients anddrymassinleaves(i.e.earlysummerspecieswithhighspecificleafarea,lowleafdrymattercontentandhighphosphorusconcentration).Old-growthstandshadfewer trait associations than managed stands, and were characterized by fernsandspecieswitheitherballisticorwind-assistedseeddispersal.Functionaldiver-sitymetricswererelatedincomplexwaystolight,managementandsoiltexture.Managedstandshadhigherfunctionalrichnessanddivergencethanold-growthstands,which,instead,showedhigherfunctionalevenness.Conclusions: Even-aged and managed stands support ground-layer specieswith a distinct set of traits relative to those found in old-growth forests.Although there is broad interest in uneven-aged management as a means torestore the structures and functions of old-growth forests, uneven-aged man-agement does not, at least initially, produce ground-layer plant communitiesmoresimilartoold-growthforeststhaneven-agedmanagement.IntroductionAnthropogenic changes in disturbance regimes havealtered the structure of temperate forests worldwide (Bur-rascano et al. 2013). In the northern temperate deciduousforests of the upper Great Lakes region of the United Statestimber harvesting has become the dominant disturbancewithin the last century. The widespread clear-cut loggingfollowing Euroamerican settlement resulted in a contem-porary landscape dominated by ca. 80–100-yr-old second-growth stands (Frelich 1995). In contrast, light to moder-ately severe wind was the prevalent disturbance prior to

Invasive grasses change landscape structure and fire behaviour in Hawaii

Abstract: Questions How does potential fire behaviour differ in grass-invaded non-native forests vs open grasslands? How has land cover changed from 1950–2011 along two grassland/forest ecotones in Hawaii with repeated fires? Location Non-native forest with invasive grass understory and invasive grassland (Megathyrsus maximus) ecosystems on Oahu, Hawaii, USA. Methods We quantified fuel load and moisture in non-native forest and grassland (Megathyrsus maximus) plots (n = 6) at Makua Military Reservation and Schofield Barracks, and used these field data to model potential fire behaviour using the BehavePlus fire modelling program. Actual rate and extent of land-cover change were quantified for both areas from 1950–2011 with historical aerial imagery. Results Live and dead fuel moisture content and fine fuel loads did not differ between forests and grasslands. However, mean surface fuel height was 31% lower in forests (72 cm) than grasslands (105 cm; P < 0.02), which drove large differences in predicted fire behaviour. Rates of fire spread were 3–5 times higher in grasslands (5.0–36.3 m·min−1) than forests (0–10.5 m·min−1; P < 0.001), and flame lengths were 2–3 times higher in grasslands (2.8–10.0 m) than forests (0–4.3 m; P < 0.01). Between 1950 and 2011, invasive grassland cover increased at both Makua (320 ha) and Schofield (745 ha) at rates of 2.62 and 1.83 ha·yr−1, respectively, with more rapid rates of conversion before active fire management practices were implemented in the early 1990s. Conclusions These results support accepted paradigms for the tropics, and demonstrate that type conversion associated with non-native grass invasion and subsequent fire has occurred on landscape scales in Hawaii. Once forests are converted to grassland there is a significant increase in fire intensity, which likely provides the positive feedback to continued grassland dominance in the absence of active fire management.

Red Lists and conservation prioritization of plant communities – a methodological framework

Abstract: Aims: Red Lists of threatened species are a well-established conservation tool throughout the world. In contrast, Red Lists of ecosystems, habitats or plant community types have only recently found interest at the global level, although they have a longer tradition in Central Europe. We contribute to the debate by presenting and discussing a comprehensive conservation assessment methodology for plant communities that was developed within the framework of the project ‘The plant communities of Mecklenburg-Vorpommern and their vulnerability’.

Phytosociology and ecology of the high-alpine to subnival scree vegetation of N and NW Iran (Alborz and Azerbaijan Mts.)

Abstract: Questions The vegetation of high-alpine and subnival scree habitats in Iranian mountains has been poorly investigated so far despite the large variety of narrowly distributed vascular plant species and the expected vulnerability of these ecosystems to global warming. Which plant communities occupy these ecosystems and what is their syntaxonomic position? Which environmental factors determine the species composition of these habitats? Location Alborz and Azerbaijan Mountains in N and NW Iran. Methods A total of 141 phytosociological releves were collected from 3200 to 4800 m a.s.l. This data set was classified using TWINSPAN, and the numerical classification was translated into a syntaxonomic system. Floristic differences between vegetation types were evaluated with detrended correspondence analysis (DCA). We determined the means and SD of measured environmental and vegetation parameters for all associations. Differences in the major environmental parameters among associations and alliances were analysed using ANOVA and post-hoc tests. Moreover, we determined the mean cover percentage of life forms in all associations. Results All high-alpine and subnival scree communities are arranged in one class (Didymophyso aucheri-Dracocephaletea aucheri), two orders (Physoptychio gnaphalodis-Brometalia tomentosi, Didymophysetalia aucheri), three alliances (Elymo longearistati-Astragalion macrosemii, Erigerontion venusti, Didymophysion aucheri) and ten associations, which are new to science, except for one association. The territory of the class extends from Alborz to NW Iran and probably to E Anatolia, Transcaucasia and the Zagros Mountains. Altitude, aspect and edaphic qualities are the major ecological factors influencing the species composition and vegetation mosaic. Conclusions Our study introduces a formal syntaxonomic classification of the scree vegetation at high altitudes in Iran, thus providing a scheme for ongoing ecological surveys and monitoring programmes to assess the impacts of climate warming and of human land use on these unique ecosystems.

Effects of grazing vs mowing on the functional diversity of sub-Mediterranean productive grasslands

Abstract: Questions In order to preserve the ecosystem functioning of semi-natural sub-Mediterranean calcareous grasslands of the Central Apennines, it is vital to understand how functional diversity (FD) changes in relation to different types of disturbance. To compare the effects of sheep grazing and those of late-summer mowing, we asked: do different types of disturbance (grazing and mowing) affect FD; are FD and species diversity positively correlated in both grazed and mown grasslands; do FD and species diversity take different paths in the two disturbance regimes; and are different FD values related to changes in the composition of traits linked to competitive ability, resource acquisition and resistance strategies? Location Grazed and mown sites in the Central Apennines (Italy). Methods We performed redundancy analysis and indicator species analysis to characterize the trait composition of the two disturbance regimes. We calculated FD for each selected trait and a compound FD for multiple traits, using Rao's quadratic entropy index. Differences in FD between disturbance regimes were tested with a nested ANOVA. We performed a regression analysis between FD and species diversity indices under the two disturbance types. Results Species and functional diversity were positively correlated in both disturbance types. FD was generally less correlated with species diversity variations in mown grasslands than in grazed ones, suggesting that late mowing leads to higher levels of functional redundancy (i.e. to a wider overlap of species functional composition). Late mowing promoted higher species and functional diversities and a wider variety of functional traits in the plant community. Grazing, besides negatively affecting the species diversity of grasslands, reduced their FD by favouring the dominance of traits related to avoidance and tolerance strategies. Conclusion The continuation of late mowing is recommended to preserve the richness and variability of functional groups and the ecosystem functioning of sub-Mediterranean grasslands.

Biogeographic patterns of base-rich fen vegetation across Europe

Abstract: Questions What is the distribution of base-rich fen vegetation and the specialist species along European biogeographic regions? How do the gradients in species composition correlate to geography and climate at continental scale? What are the implications of such patterns for the classification of these habitats? Location Fifteen countries of Central, Western and Northern Europe. Methods We compiled a vegetation plot database of base-rich fens and related communities including vascular plants and bryophytes. The initial data set with 6943 plots was filtered according to the presence of specialists using discriminant analysis. We used DCA to analyse the correlation of species composition with geography and climate, and kriging interpolation for mapping gradients in the study area. Modified TWINSPAN was used to detect major vegetation groups. The results of the whole data set (plot size 1–100 m2) were compared with those obtained from two subsets with plots of 1–5 m2 and 6–30 m2. Results Most of the specialists were distributed among all the biogeographic regions, but many were more represented in the Alpine than in the Atlantic, Boreal and Continental regions. Variation in species composition was mainly correlated to temperature, precipitation and latitude in the three data sets, showing a major gradient from (1) alpine belt fens characterized by spring species to (2) small sedge fens mainly distributed in mountain regions and (3) boreo-temperate fens reflecting waterlogged conditions. Conclusions Base-rich fen communities are widely distributed across European biogeographic regions, but the Alpine region can be considered as the compositional centre of this vegetation type. Large-scale gradients of species composition are mainly explained by climate, while the influence of latitude is probably correlated to increasing water table in the boreo-temperate regions. These gradients can be better understood by differentiating three major vegetation types, which should be considered when establishing classification systems of base-rich fens in Europe.

Fire and gap dynamics over 300 years in an old-growth temperate forest

Abstract: Questions: What are the long-term patterns of wildfire occurrence and gap dynamics in an old-growth deciduous forest? Are there temporal patterns in fire and gap dynamics over the last ca. 300 yrs? How is drought related to fire occurrence? Are there temporal interactions between gap dynamics and fire? Location: Lilley Cornett Woods Appalachian Research Station, Southeastern Kentucky, USA. LCW; 37°05′ N, 83°00′ W. Methods: We cross-dated and analysed annually-resolved tree-ring data from 35 tree cross-sections in an old-growth deciduous forest to reconstruct historical fire and canopy disturbance and explore connections among these processes. Canopy disturbance patterns as indicated by tree growth release within this collection [fire history collection: (FHC)] were compared to cores from 26 trees collected in 1983 for the purposes of climate reconstruction [climate collection: (CC)]. Results: Initiation dates in the FHC ranged from ca. 1670 to 1925. Thirty-three fire scars were identified from 1678 to 1956. The mean interval between fire events was 9.3 yrs, and there were many more fires after 1800 than before that date. Gap dynamics, as reconstructed through growth release detection, were relatively constant through the FHC record and were supported by a similar result in the CC. The mean number of years between detected release events was 5.2 yrs. Many individual trees, and the mean growth chronology for the FHC, indicate that many oak trees exhibit growth release after long periods of suppression and, after a final release, exhibit a step-change in growth rate suggesting canopy accession. Conclusions: Fire and gap dynamics occurred through much of the last ca. 350 yrs in this old-growth forest. There was not evidence to support that these two processes were temporally linked – gap dynamics were ostensibly independent of fire occurrence. Even so, we posit that these two processes may have a synergistic effect on long-term dynamics, wherein fire ‘filters’ the seedling pool and gap openings provide canopy accession opportunities. We also note several instances where release events are associated with stand-wide growth increases suggesting large-scale canopy accession. These events could influence the overstorey composition of the forest for centuries.

A simple test for alternative states in ecological restoration: the use of principal response curves

Abstract: Aims Ecological resistance and resilience and its link to alternative states is an important concept in ecological restoration. In many situations there is a need to flip one ecosystem state to another and then keep it there; thus there is a need to overcome the resistance/resilience of the starting community and create another one with sufficient resistance/resilience to maintain it in that state. The difficulty for ecological restoration is that these concepts are complicated to measure in practice, and hence tend to be discussed in rather abstract terms. Here, we describe the application of principal response curves (PRC) to test for the creation of alternative states or alternative stable states in ecological restoration studies. Location Six experiments on acid grassland and heathland invaded by Pteridium aquilinum across Great Britain. Methods We use PRC, a multivariate approach, to measure change in ecological restoration experiments that allows a formal test of whether alternative states are created. We used PRC to test for change in plant species composition in a series of replicated experiments designed to change a late-successional ecosystem, dominated by P. aquilinum, into either heathland or acid grassland. Here, we tested three Pteridium control treatments, including two ‘one-off’ treatments (applied only at the start) and a ‘repeated’ (applied regularly) treatment, against an untreated experimental control. Results In the heathland targets, alternative states were induced within 10 yrs using the ‘repeated’ treatment (cutting twice per year). All ‘one-off’ treatments either did not overcome the resistance of the starting community or if they did, produced a temporary displacement, but the resilience of the initial state was too high and there was a rapid reversion to the starting community. In the grassland community, alternative states were induced by ‘repeated’ treatment (cutting twice per year), but the ‘one-off’ treatment suggested creation of an alternative stable state that lasted 10 yrs. Conclusions For the first time, there is a methodology using PRC that tests for the creation of alternative states or alternative stable states in ecological restoration research. The drawback is that a long-term data set from replicated experiments with an untreated control treatment is needed.

Life after fire: smoke and ash as germination cues in ericads, herbs and graminoids of northern heathlands

Abstract: Question What is the impact of the fire cues smoke and ash on seed germination of important functional groups in the heathland system, namely ericads, herbs and graminoids? We predict that if germination from heathland seed banks is in part regulated by fire cues, there should be stronger responses to fire cue treatments in seed bank samples taken from heath that has not been recently burned in comparison with samples taken from newly burned heath, where seed banks have been exposed to the same cues in situ. Location Lygra, Lindas commune, western Norway. Methods The efficacy of smoke, charred wood, ash and heat in promoting germination has been documented in a wide range of species and systems, but relatively little work has been done on fire-related cues in northern European heathlands under anthropogenic fire regimes. We studied fire experimentally by testing the effects of aqueous smoke solution, ash and a combination of the two treatments, on the germination of graminoids, herbs and ericads. A greenhouse germination trial compared seed banks from old heath (28 yr since the last fire) with seed banks from newly burned heath (burned the previous year), where we expected that fire-cued germination had already occurred. Results We found that both ericads and graminoids responded to fire cues, whereas herbs did not. In line with our predictions, responses were stronger in the old heath than in the young heath. Further, the smoke treatment is a more effective cue than ash across all functional groups. Conclusions The prevalence of positive fire cue responses across functional groups underscores the importance of fire in the ecology of these heathlands, and hence of burning as a central tool for their management. The finding that the germination response is stronger in naive seed banks than in seed banks that have already been exposed to recent fire cues through in situ fires further supports the role of fire in the successional dynamics of these heathlands.

Effects of post-windthrow salvage logging on microsites, plant composition and regeneration

Abstract: Questions: How does windthrow influence plant diversity and composition aswell as regeneration and microsite characteristics? What are the consequencesofpost-windthrowsalvageloggingonthesekeyattributes?Location:Easternblackspruce–mossforest,Quebec,Canada.Methods:Atotalof92plotsweresampled,eachwitharadiusof11.28 m;49ofthese plots were salvaged while 43 were unsalvaged. Regeneration density,plantdiversityandseedbedswerecharacterized.Wetestedtheeffectofmicroto-pography and windthrow severity on species richness and Shannon diversityindex for salvaged and unsalvaged windthrows using a mixed model. Partialredundancyanalysis(RDA)determinedwhichenvironmentalandstandcharac-teristicsweremostimportantinexplainingdifferencesinplantspeciesandforestfloortypesamongthetreatments.Theeffectsof treatments(salvaged and unsal-vagedwindthrows),microtopographyattributes,windthrowseverityandregen-eration species on seedling and sapling abundance were tested using a linearmixedmodel.Results:Salvagedwindthrow,withalargeproportionofskidtrails,deadmossesand Sphagnum, had a lower degree of seedbed heterogeneity. Also, some under-storey species present in the unsalvaged ecosystem were absent from the sal-vaged windthrow. Sphagnum and other moss species were clearly associatedwith the unsalvaged treatment. White birches were positively associated withmoundmicrotopographyintheunsalvagedwindthrow.Conclusion: From an ecosystem-based forest management perspective, naturalpost-windthrow understorey conditions and microsite heterogeneity can be inpart maintained in salvaged cut blocks by incorporating retention patches thatinclude downed and standing dead wood and living trees of diverse sizes. Thesestepsshouldfavourplantregenerationandaugmentdiversityforsalvageloggingafterwinddisturbance.IntroductionIn many parts of the world, major disturbance episodesoften lead to salvage logging (often called sanitary loggingin Europe; Lindenmayer et al. 2004, 2008). Functionally,salvage logging can be distinguished from other harvestoperations in that, with salvaging after natural distur-bance, the ecosystem is subjected to two sequential distur-bances within a short period (Lindenmayer et al. 2008).Peterson & Leach (2008) suggest that multiple disturbanceimpacts need to be understood on the basis of cumulativeseverity. Indeed, recent conceptual advances (e.g. the cuspmodel of Frelich & Reich 1999; the three-axis model ofRoberts 2004, 2007) have begun to address the potentialfor multiple disturbances to change the trajectory of com-munity development, sometimes in undesirable directions(Paine et al. 1998). Because of the potential for thecombined severity of natural disturbance followed bysalvaging to yield unwanted ‘ecological surprises’ (Paineet al. 1998), guidelines are needed for the planning of