Diversity change of mountain hay meadows in the Swiss Alps

We investigated changes in plant diversity in the traditionally fertilised and species-rich Golden Oat meadows by repeating historic grassland relevés from the 1940s in two agricultural areas in the Swiss Alps. The effects of time on alpha and beta diversity at plot level were analysed within the study areas. The specificity of the two study areas was investigated by comparing the variability of species composition within and between study areas.In both regions, species richness at plot level (alpha diversity) was found to be lower in the recent relevés than in the historic ones. However, the variability of species composition within the study areas (beta diversity) was higher between the recent relevés than between the historic relevés. There was a significant floristic differentiation between the two study areas sixty years ago but not today.Plant diversity in Golden Oat meadows has changed significantly during the last sixty years. The decrease in species richness at plot level was anticipated, but not the increase in beta diversity between plots, which may indicate individualised management regimes of modern farmers. The loss of specificity between the study areas revealed an important and as yet hardly considered further dimension of biodiversity change, which leads to a homogenisation of plant diversity at a regional level.     

Effects of deferring grazing on the floristic diversity of Stipa tenacissima Loefl. ex L. rangelands in central Algerian steppe

The present work aims to study the effect of deferring grazing on the floristic diversity of Stipa tenacissima Loefl. ex L. rangelands in the central Algerian steppe in two different bioclimatic stages, namely semi‐arid and arid. This work is part of a perspective to know the floristic characteristics of an area excluded from grazing and an unrestricted rangeland, in two different environments in order to highlight the factors that are conceivably responsible for the diversification of flora in the steppe ecosystems. In the present study, a number of 96 floristic surveys were performed during the spring season of the years 2014, 2015 and 2016. The methodology adopted is a subjective sampling. The minimum area retained is 100 m² defined by the method of Braun Blanquet and de Bolos (1957, Annales Estacion Experimental de Aula Dei, 5, 266). This method has been used to study the floristic diversity represented by the floristic richness, Shannon index, the equitability, the biological and the phytochoric type. The climatic correction according to the altitudinal gradient was applied to determine the bioclimatic stage. The results from the surveys indicate that the rangelands at the studied sites contain 109 species, 27 families and 63 genera out of which 79 species and 22 families are in the semi‐arid bioclimatic stage. A two‐way analysis of variance was employed to examine the effect of the bioclimatic stage and the pasture land put at rest. Variance analysis of the diversity indices showed that the bioclimatic stage has a significant impact on the floristic richness and flora diversity of the S. tenacissima steppe (p ≤ 0.01) with a 5% threshold; on the other hand, the protection of these ecosystems does not have a remarkable influence on the floristic diversity (p > 0.05). In recent years, climatic disturbances have resulted in changes in vegetation, even in rested areas located between the study localities.     

Transit towards floristic homogenization on oceanic islands in the south-eastern Pacific: comparing pre-European and current floras

Aim  To quantify the occurrence of processes of homogenization or differentiation in the vascular flora of six oceanic islands.
Location  Six islands in the south-eastern Pacific drawn from the Desventuradas Archipelago, Easter Island and the Juan Fernández Archipelago.
Methods  Using published floristic studies, we determined the floristic composition of each island at two different stages: (1) pre-European colonization and (2) current flora. We compared changes in the number of shared plants and the floristic similarity among islands for each stage.
Results  The number of plant species doubled from 263 in pre-European flora to 531 species currently. Only three native species became extinct, four natives were translocated among the islands and 271 plant species were introduced from outside. The frequency of plant species shared by two or more islands is higher in the post-European floras than prior to European contact, and the level of floristic similarity between islands increased slightly.
Main conclusions  Considering the low naturalization rate of alien plants, the small number of extinctions and the meagre increase in floristic similarity, these islands are undergoing a slow process of floristic homogenization.     

The Effect of Restoration Methods on the Quality of the Restoration and Resistance to Invasion by Exotics

The methods employed in a restoration can impact the resulting plant community. This study investigated the effect of restoration method on several indices of plant community structure by comparing two restoration methods conducted over an 8‐year period to a naturally colonized postagricultural field and a remnant grassland. The restoration methods included (1) distributing seed over fallow fields and (2) planting established seedlings in combination with seeding a fallow field. We found greater plant community resemblance (i.e., floristic quality, native species richness, and native diversity) to remnant grasslands with the introduction of seedlings during the first 4 years of restoration. There was also a negative correlation between the native plant diversity and the density of exotic plants in the restoration. This relationship suggests that introducing native plants in postagricultural fields may represent an effective management strategy to reduce exotic plant density.     

Determinants of diversity in afrotropical herbivorous insects (Lepidoptera: Geometridae): plant diversity,vegetation structure or abiotic factors?

Aim This study was conducted to investigate the potential of predicting alpha diversity and turnover rates of a highly diverse herbivorous insect family (Geometridae) based on vascular plant species richness and vegetation structure. Location The study was carried out on the south‐western slopes of Mount Kilimanjaro within a wide range of habitats between 1200 and 3150 m elevation. Methods The floristic and structural composition of the vegetation was recorded at 48 plots of 400 m². Geometrid moths were sampled manually at light sources located at the plot centres. Principal components analysis, redundancy analysis and multiple linear regression were used to explore how alpha diversity and species turnover of geometrid moths are related to vegetation structure and plant species richness. Results Alpha diversity of geometrid moths was significantly correlated with species diversity patterns in the most common vascular plant families (R² = 0.49) and with plant structural parameters (R² = 0.22), but not with overall floristic diversity. Species turnover of geometrid moths was strongly linked to diversity changes in a range of plant families (40% explained variance), less strongly to changes in vegetation physiognomy (25%), and only weakly to overall floristic diversity (5%). Changes in elevation were a better predictor of both alpha diversity and species turnover of geometrid moths than any principal component extracted from the vegetation data. Main conclusions Vegetation composition, diversity and structure all showed significant correlations with the diversity and species composition of geometrid moth assemblages. Nevertheless, in most cases relationships were indirect, via environmental parameters such as temperature and humidity, which influenced both vegetation and moth fauna. Possible direct links between geometrid diversity and potential food plants were much weaker. The lack of a significant correlation between overall plant species richness and geometrid diversity indicates that tropical geometrid moths may not be very selective in their food plant choice. Accordingly, a clear correlation between floral diversity and herbivore species richness must be regarded as overly simplistic, and the diversity of vascular plants cannot universally be used as a suitable biodiversity indicator for diverse insect taxa at higher trophic levels.     

Longitudinal evaluation of vegetation richness and cover at wetland compensation sites: implications for regulatory monitoring under the Clean Water Act

There has been regulatory concern over the appropriate length of time to monitor wetland sites restored or created as compensation for impacts permitted by a U.S. Clean Water Act permit. However there is very little longitudinal research on wetland compensation sites, and conclusions on compensation site development are usually drawn from the analysis of a chronosequence of sites of different ages. This approach has limitations, given the extent of changes in wetland compensation practices and performance standards over the past few decades. In this study we conducted vegetation surveys of 22 wetland compensation sites in a rapidly developing part of the Minneapolis-St. Paul metropolitan area in 1997 and 2010. We present data on changes over time in floristic richness and cover at the site level and at the level of wetland community type within each site. Our findings do not support the assumption that wetland compensation sites progress on a trajectory toward increasing diversity, floristic quality, or native cover over time. We find that, when data from all sites are considered together, emergent communities have suffered significant declines in both floristic quality and native plant cover, while wet meadow communities have gained species richness but not species diversity. There is some evidence that site richness and cover characteristics are converging toward a regional mean over time, as the species composition of wet meadows became significantly more similar over the survey period, and all community types have significant increases in woody cover. Our study suggests the importance of selecting appropriate compensation sites that avoid foreseeable hydrologic stresses, and does not support the position that 5 years of monitoring can assure the ongoing biotic integrity of wetland compensation sites.     

Are long‐unburnt eucalypt forest patches important for the conservation of plant species diversity?

Question: Are long‐unburnt patches of eucalypt forest important for maintaining floristic diversity? Location: Eucalyptus forests of southeastern New South Wales, Australia. Methods: Data from 976 sites representing a range of fire history from three major vegetation formations – shrubby dry sclerophyll forest (SF), grassy dry SF and wet SF – were analysed. Generalized linear models were used to examine changes in species richness with increasing time since wildfire and analysis of similarities to examine changes in community composition. Chi‐squared tests were conducted to examine the distribution of individual species across four time since fire categories. Results: Plant species relationships to fire varied between the three formations. Shrubby dry SF supported lower plant species richness with increasing time since wildfire and this was associated with shifts in community composition. Grassy dry SF showed significant shifts in community composition and species richness in relation to time, with a peak in plant species richness 20–30 yr post fire (either prescribed fire or wildfire). Wet SF increased in species richness until 10–20 yr post wildfire then displayed a general declining trend. Species richness in each vegetation type was not related to the fire frequencies and fire intervals observed in this study. Conclusions: Long‐unburnt (30–50 yr post wildfire) forests appeared to play a minor role in the maintenance of plant species diversity in dry forest systems, although this was more significant in wet forests. Maintenance of a range of fire ages within each vegetation formation will assist in maintaining floristic diversity within regions.     

Phytogeographical and community similarities of alpine tundras of Changbaishan Summit,China, and Indian Peaks,USA

Abstract. We compared the diversity, phytogeography, and plant communities in two mid-latitude alpine tundras with comparable aerial and elevational extents: Changbaishan Summit in eastern Asia and Indian Peaks in western North America. Despite wide separation, the two areas shared 72 species. In all, 43% of the species on Changbaishan Summit are also distributed in the alpine zones of western North America, while 22% of the species on Indian Peaks are also distributed in the alpine zones of eastern Asia. Almost all the shared species also occur in the Beringian region. Phytogeographical profiles of species and genera showed that 69% of species and over 90% of genera in both alpine tundras belong to the three phytogeographical categories: cosmopolitan, circumpolar, and Asian-North American. We attributed the current floristic relationship between these widely separated areas to the periodic past land connection between the two continents during the Tertiary and Pleistocene. Indian Peaks has a closer floristic relationship with the Arctic tundra than does Changbaishan Summit. Indian Peaks also has 45% higher species richness and lower vegetation cover than Changbaishan Summit. Plant communities from the two areas were completely separated in the two-way indicator species analysis and non-metric multidimensional scaling on floristic data at both species and generic levels, whereas ordination of communities by soil data produced a greater overlap. The plant communities on Changbaishan Summit in general have lower alpha diversity, higher beta diversity (lower between-community floristic similarity), and more rare species than does Indian Peaks. Mosaic diversity does not differ in the two alpine tundras, although the analysis suggests that Changbaishan Summit communities are more widely spaced on gradients than the Indian Peaks communities.     

Plant families as predictors of plant biodiversity in Mexico

Three speciose plant families (Asteraceae, Fabaceae s.l. , and Poaceae) are evaluated for their appropriateness as predictors of overall regional patterns of plant diversity in Mexico. These families fulfil criteria for usefulness as indicators advocated by several authors, such as adequate taxonomic knowledge, wide geographical distribution, and occurrence in different plant communities. Known richness was determined from a database including 17,903 species from floristic inventories, review of taxonomic literature, and the study of herbarium specimens. Mexico was divided into 253 cells, each 1° latitude by 1° longitude; for each cell, total plant diversity and number of species in each predictor's family were determined. In addition, each species was categorized by 'preferred' vegetation type (temperate forest, dry tropical forest, humid tropical forest, xerophytic scrubland). Both multiple and simple regression models show that the three families are good predictors of total vascular floristic richness. Fabaceae s.l. has the highest semipartial correlations for all multiple models except with the xerophytic scrubland data set, for which it shares the highest values with Poaceae. Univariate models also predict satisfactorily the vascular floristic richness, especially when Fabaceae s.l. is used as the predictor, and the effect of vegetation type is included. Our results indicate that these three families can be used as potential predictors for total vascular plant species richness in Mexico although Fabaceae s.l. is the best predictor.     

不同演替阶段鼢鼠土丘群落植物多样性变化研究

用空间序列代替时间序列的方法对高寒草甸不同演替阶段高原鼢鼠土丘植物群落的物种组成和多样性变化进行了研究．结果表明,不同演替阶段鼠丘植物群落的物种组成及外貌特征与原生植被(对照)之间存在较大差异．在演替的早期阶段,r对策者如萼果香薷、灰绿藜、鹅绒委陵菜、细叶亚菊等演替先锋种在群落中占相对重要地位．随着演替的进展,k对策者如长毛风毛菊、垂穗披碱草、甘肃嵩草、线叶嵩草等在群落中的比例增加．α多样性分析表明,随着演替的进展,群落物种丰富度指数(O)显著增加,其排列顺序为：阶段1<阶段2<阶段3<阶段4<原生植被;均匀度指数(Pielou均匀度指数)的变化趋势与丰富度指数相同;多样性指数(Simpson指数D和Shannon-．Wiener指数H’)按群落的演替梯度呈增加趋势．卢多样性分析表明,阶段1与原生植被及阶段1与阶段4植物群落物种组成的相似系数最小,为0．18;阶段1与阶段2植物群落物种组成的相似系数最大,为0．62．同时,群落生活型功能群组成也随鼠丘的演替进展而发生变化,反映出不同演替阶段的鼠丘植物群落和微生境都发生了改变．     

Ecological features affect patterns of plant communities in Mediterranean temporary rock pools

In this paper, the results of a study on the ecology, floristic composition and spatial assemblages of temporary limestone rock pool plant communities of a central Mediterranean area (S Sicily, the Maltese Islands and Lampedusa) are presented. A total of 76 temporary pools were studied, distributed between the infra-mediterranean and thermo-mediterranean bioclimatic belt. For each temporary rock pools, the floristic composition and cover of the species were determined using standard relevé methods. Moreover, for 50 of these pools, pH, conductivity, soil depth, water-level, altitude and floristic richness and diversity index were assessed. The plant communities were analysed using unweighted pair group method using arithmetic averages and Euclidean distance classification and ordination methods such as canonical correspondence analysis (CCA). A total of four plant communities with specific floristic composition were established, each one with a different dominant species: Callitriche truncata; Elatine gussonei; Tillaea vaillantii and Lythrum hyssopifolia. According to the CCA, the spatial patterns of plant communities follow an ecological gradient related to water level and depth/size of the rock pools: these are the main ecological features affecting the distribution of the plant communities of rock pools. In addition, floristic richness and diversity index showed a slight increase in trend from temporary pools submerged for long periods towards pools submerged for short periods.     

The effect of prescribed burning on plant rarity in a temperate forest

Rare species can play important functional roles, but human‐induced changes to disturbance regimes, such as fire, can inadvertently affect these species. We examined the influence of prescribed burns on the recruitment and diversity of plant species within a temperate forest in southeastern Australia, with a focus on species that were rare prior to burning. Floristic composition was compared among plots in landscapes before and after treatment with prescribed burns differing in the extent of area burnt and season of burn (before–after, control‐impact design). Floristic surveys were conducted before burns, at the end of a decade of drought, and 3 years postburn. We quantified the effect of prescribed burns on species grouped by their frequency within the landscape before burning (common, less common, and rare) and their life‐form attributes (woody perennials, perennial herbs or geophytes, and annual herbs). Burn treatment influenced the response of rare species. In spring‐burn plots, the recruitment of rare annual herbs was promoted, differentiating this treatment from both autumn‐burn and unburnt plots. In autumn‐burn plots, richness of rare species increased across all life‐form groups, although composition remained statistically similar to control plots. Richness of rare woody perennials increased in control plots. For all other life‐form and frequency groups, the floristic composition of landscapes changed between survey years, but there was no effect of burn treatment, suggesting a likely effect of rainfall on species recruitment. A prescribed burn can increase the occurrence of rare species in a landscape, but burn characteristics can affect the promotion of different life‐form groups and thus affect functional diversity. Drought‐breaking rain likely had an overarching effect on floristic composition during our study, highlighting that weather can play a greater role in influencing recruitment and diversity in plant communities than a prescribed burn.     

Seabirds drive plant species turnover on small Mediterranean islands at the expense of native taxa

The analysis of long-term floristic changes was conducted on nine west-Mediterranean limestone islands (size range: 2–95 ha) which have recently undergone a severe demographic explosion in their yellow-legged gull Larus cachinnans colonies. A comparison of past and present plant inventories was used to quantify extinction-colonization events, both from a classical biogeographical perspective (per island approach) and a metapopulational perspective (per species approach). In the first approach, floristic turnover intensity was negatively related to island area and positively to gull nesting density, but was independent of island isolation. In the second, species turnover rate was compared with a set of plant species life history traits (dispersal mode, Grime CSR strategy, growth form, biogeographical type). Plants which exhibited the highest turnover rate were primarily ruderal, annual, wind-dispersed species with a wide geographic range. The severe disturbance induced by seabird activities has tended to select and favour some adapted plant species groups at the expense of indigenous island taxa. The relationships between specific turnover intensity and plant life history traits justify using the metapopulation approach and point to the importance of interspecific variations in extinction-colonization patterns. Received: 21 September 1998 / Accepted: 8 October 1999     

Nuovi reperti di intersessualità nelle Cucurbitacee

Abstract

The aim of this paper is to investigate differences in plant species composition between managed and unmanaged forests, and to assess if these difference give rise to a higher plant diversity in the unmanaged forest. Furthermore our aim is to relate forest structure to differences in plant species composition, identifying the structural attributes more strongly related to the unmanaged forest vegetation. We compared an old-growth forest and a managed highforest in the Abruzzo Lazio and Molise National Park (Central Italy). Plant species composition and diversity, deadwood components and live structure have been analyzed. We used permutational multivariate analysis of variance to test the response of species composition to management factor; furthermore, we compared species richness and beta diversity. Redundancy analysis has been used to relate plant species abundances to structural variables; the importance of dead and living wood components has been compared through variation partitioning. Plant species composition proved to be significantly different in the two sites, and the old-growth stand showed a higher plant diversity. From a structural point of view, we found differences especially in the amount and quality of deadwood, and in the diameter class distribution. These variables are also the most important in determining the old-growth stand plant species composition according to redundancy analysis. Variation partitioning confirmed the greater importance of the deadwood variables. Our results suggest that including deadwood surveys in traditional forest inventories could help in finding forests with both structural and floristic old-growth properties to be considered in conservation programmes. The imitation of natural dynamics, through the creation of gaps avoiding deadwood removal, could be an effective strategy for restoring old-growth conditions, also in terms of plant diversity.     

High Functional Diversity is Related to High Nitrogen Availability in a Deciduous Forest – Evidence from a Functional Trait Approach

The current study tested the assumption that floristic and functional diversity patterns are negatively related to soil nitrogen content. We analyzed 20 plots with soil N-contents ranging from 0.63% to 1.06% in a deciduous forest near Munich (Germany). To describe species adaptation strategies to different nitrogen availabilities, we used a plant functional type (PFT) approach. Each identified PFT represents one realized adaptation strategy to the current environment. These were correlated, next to plant species richness and evenness, to soil nitrogen contents. We found that N-efficient species were typical for low soil nitrogen contents, while N-requiring species occur at high N-contents. In contrast to our initial hypotheses, floristic and functional diversity measures (number of PFTs) were positively related to nitrogen content in the soil. Every functional group has its own adaptation to the prevailing environmental conditions; in consequence, these functional groups can co-exist but do not out-compete one another. The increased number of functional groups at high N-contents leads to increased species richness. Hence, for explaining diversity patterns we need to consider species groups representing different adaptations to the current environmental conditions. Such co-existing ecological strategies may even overcome the importance of competition in their effect on biodiversity.     

Large-scale diversity patterns of vascular epiphytes in Neotropical montane rain forests

Aim Epiphytes contribute up to 30% to the number of vascular plant species in certain global biodiversity hotspots, e.g. the Ecuadorian Andes. However, their large scale diversity patterns are still discussed on the base of results from a few, local epiphyte inventories. Consequently, explanatory models on epiphyte diversity concentrate on the impact of local climate on small scale epiphyte species richness. Our aim was to analyse large scale elevational patterns of epiphyte diversity integrating data from different geographic scales. Location Tropical America, with special emphasis on the Ecuadorian Andes. Methods Our study is based on two data sources. First, we analysed the elevational patterns of epiphyte diversity based on the Catalogue of the Vascular Plants of Ecuador and the Libro Rojo de las Plantas Endèmicas del Ecuador. Secondly, the floristic turnover between the epiphyte inventories of seven montane and four lowland study sites in the Neotropics was analysed. Results The floristic turnover between Neotropical montane epiphyte floras is higher than the one between lowland epiphyte floras. Montane study sites located only a few kilometres apart from each other show considerable differences in their epiphyte species inventories. Irrespectively of their similar dispersal mode, the floristic turnover is much higher for orchids than for Pteridophyta. The Orchidaceae are the species richest group in all of the examined 11 Neotropical epiphyte floras. At the larger scale of the Ecuadorian Flora, c. 50% of the species in the elevational zone with maximum epiphyte diversity (between 1000 and 1500 m) are orchids. Elevational patterns of epiphyte diversity strongly reflect patterns of Orchidaceae. Main conclusions Our results support the observation of a ‘mid‐elevation bulge’ of epiphyte diversity by Gentry and Dodson. It has been frequently shown that the high humidity in mid‐elevations is suitable to maintan a high epiphyte species richness. Our findings show that in addition, large scale epiphyte diversity in montane rain forest is increased by the high floristic turnover at local and regional scale. Based on the importance of Orchidaceae for epiphyte diversity, we discuss that speciation processes corresponding to the highly diverse environment are a driving force for endemism, floristic heterogeneity and consequently for large scale epiphyte species richness in montane forests.     

Floristic diversity along the roadsides of an urban biodiversity hotspot in Indian Himalayas

In the urban landscapes, scientific understanding of the roadside vegetation is a prerequisite for better planning and designing of sustainable cities. The Srinagar city, located in the Indian Himalayas, represents an urban biodiversity hotspot but the information about the floristic diversity especially along its roadsides is lacking. In order to fill this knowledge gap, the present study using field-based plant collection surveys was undertaken to investigate the floristic diversity growing along the roadsides of Srinagar. A total of 206 vascular plant species were recorded with the proportion of alien species relatively higher (52%) than the native species (48%). Of the 108 alien species, 24 were invasive, 44 naturalized, 12 casual and 23 were cultivated. Most of the species were herbs (165 spp.) and the majority of these were wild growing (155 spp.). Based on Raunkiaer’s lifeform characterization, therophytes (94 spp.) were the most dominant. Interestingly, the therophytes harboured the highest number of alien species (50 spp.), followed by phanerophytes (29 spp.). There was significant difference between the floristic spectrum obtained during the present study and the normal Raunkiaer’s spectrum. The present study provides policy-relevant baseline data which can guide the urban planners to develop sustainable planning in this Himalayan city.     

Seed bank dynamics in abandoned meadows during a 20-year period in the Białowieża National Park

1 The relationship between size and floristic composition of the seed bank and vegetation dynamics was studied between 1976 and 1996 in 0.75 ha of an abandoned Cirsietum rivularis meadow. The plot was divided into 100-m² (10 × 10 m) quadrats and sampled 5-yearly to map the vegetation and determine the soil seed bank.
2 Densities of seeds in the soil fluctuated as succession proceeded. The initially small seed bank trebled by 15 years after abandonment, before falling, after 20 years, to approximately the same as in the initial stage.
3 The floristic richness of the seed bank decreased during succession, with the number of species falling from 38 to 25. The diversity of life forms, however, increased in later periods, with tall herbs, shrubs and trees appearing after 10 years.
4 Seed bank floristic composition is apparently both a product of the species composition of the current vegetation and a record of the long-term substitution of species. Other factors, including the structure of the vegetation, also influence the accumulation of seeds in the soil.
5 Although changes in number of species show a directional pattern, the seed bank size fluctuated in the course of succession on these fertile wet meadows.     

Avian Composition Co‐varies with Floristic Composition and Soil Nutrient Concentration in Amazonian Upland Forests

Spatial heterogeneity in the plant species composition of tropical forests is expected to influence animal species abundance and composition because vegetation constitutes the primary habitat feature for forest animals. Floristic variation is tied to variation in soils, so edaphic properties should ultimately influence animal species composition as well. The study of covariation in floristic and faunistic turnover has been hindered by the difficulty of completing coordinated surveys in hyperdiverse tropical communities, but this can be overcome with the use of a few plant taxa that function as surrogates for general floristic turnover. We used avian and plant transect surveys and soil sampling in a western Amazonian upland (terra firme) forest landscape to test whether spatial variation in bird community composition is associated with floristic turnover and corresponding edaphic gradients. Partial Mantel tests and Non‐metric Multidimensional Scaling showed floristic distinctiveness between two forest types closely associated with differences in soil cation concentrations, and differences in both floristic composition and cation concentrations were further linked to compositional differences in avian species, independent of geographic distances among sites. Ten percent of bird species included in Indicator Species Analyses showed significant associations with one of the two forest types. The upland forest types that we sampled, each corresponding to a different geological formation, are intermediate relative to edaphically extreme environments in the region. Models of avian diversification should take into account this environmental heterogeneity, as should conservation planning approaches that aim to represent faunal diversity. Abstract in Spanish is available in the online version of this article.     

Effects of repeated burning on Mediterranean communities of the northeastern Iberian Peninsula

Question: In relation to a single fire, do repeated wildfires in Mediterranean type ecosystems (1) reduce plant species richness or diversity; (2) modify patterns of abundance or dominance of plant species or (3) alter plant composition? Location: Pinus halepensis dominated communities of Catalonia, northeastern Iberian Peninsula, western Mediterranean Basin. Methods: Regional, paired design with 14 study sites, each consisting of a once burnt area (1994) and a twice burnt area (1975–1993 and 1994). Ten years after the last fire, we recorded all vascular plant species present in nested plots and quantified their relative abundances on transects. We compared species richness, diversity, dominance and relative abundance and species‐area correlations between paired once and twice burnt areas and assessed their floristic composition similarity. Results: No statistically significant differences were found in species richness or diversity. Slopes of species‐area correlations were higher in once burnt areas. In twice burnt areas, dominance by one or two species was higher. P. halepensis showed lower relative abundance and nanophanerophytes showed higher relative abundance. No differences were found for resprouter, seeder or resprouter‐seeder species. Floristic composition similarity between paired areas tended to be higher in less productive sites. Conclusions: Fire recurrence had contrasting effects on species richness at different spatial scales. Repeated burning reduced the relative abundance of the dominant tree species, which resulted in a higher relative abundance of shrubs. It also promoted the dominance of herbs, particularly Brachypodium retusum. However, it did not change the relative abundance of regenerative groups. Paired areas were more similar as they were more Mediterranean in terms of climatic conditions.