Vegetation on the edge: a gradient analysis of the riparian zone, Poerua River, New Zealand

Forest vegetation patterns alongside the Poerua River, south Westland, were studied to determine whether a distinct riparian community could be defined either immediately adjacent to the river, or out to the limit of overbank flooding. Ten randomly located 100 m transects were established perpendicular to the river at each of two sites. Ground cover of alluvial sediment indicated that annual overbank flooding occurred up to 20 m into the forest (the flood zone). No significant difference in vascular plant species richness was found between the flood zone and non-flood zone at either site, however a significant difference in species richness was found between sites, and this was attributed to recent disturbance at the edge of one site. Detrended correspondence analysis separated plots by site and indicated a gradient of species change from the river’s edge to the ends of the transects. There were inconsistent differences in the densities and/or basal areas of trees and shrubs between sites and zones. No distinct band of vegetation was recognizable as a riparian zone alongside the Poerua River. Instead, there was evidence that edge processes had influenced vegetation patterns on a gradient away from the river, fluvial processes had eroded into, and influenced the vegetated edge, and historical disturbance events had had strong effects on vascular plant community composition. The riparian zone incorporates the whole floodplain and environmental management needs to take this into consideration.     

雅鲁藏布江河岸植物物种丰富度分布格局及其环境解释

沿环境梯度物种多样性的分布格局及其环境影响因子的研究是生态学研究的重点内容之一。雅鲁藏布江是我国海拔最高的大河, 目前还没有针对其流域的河岸植物群落物种丰富度分布格局的系统研究。作者沿海拔梯度从雅鲁藏布江上游源头区至下游共设置了15个海拔样带, 在每个海拔样带随机取6个5 m×5 m样方, 共对90个样方的河岸植物群落物种组成和植被类型进行了调查, 共记录到238种维管束植物。DCA排序结果表明物种组成变化主要受海拔和经度控制。CCA排序区分出5种大的植被类型, 即高寒草甸或高寒草原、高山草原、两种亚高山灌丛草原和林缘灌丛植被。各植被类型的分布和变化主要受海拔和经度影响。雅鲁藏布江河岸植物物种丰富度沿海拔和经度梯度呈浅“U”形分布格局, 物种丰富度与年均降水量和植被盖度成显著正相关。     

三江并流地区干旱河谷植物物种多样性海拔梯度格局比较

在滇西北三江并流地区典型干旱河谷段, 在怒江、澜沧江和金沙江的东、西坡共设置了6条海拔梯度样带, 通过标准样地的植物群落调查, 分析各条样带植物的物种丰富度、物种更替率的海拔梯度格局, 并比较了地理和植被变量对分布格局的解释。干旱河谷植被带位于海拔3,000 m以下, 以灌丛和灌草丛为主, 其在各河谷的分布上限自西向东依次升高。植物物种丰富度的分布主要与海拔、流域、经纬度和植被带有关, 沿纬度和海拔梯度升高而显著增加的格局主要表现在草本层和灌木层, 灌木物种丰富度还呈现自西向东显著增加的趋势。怒江的灌木和草本种物种丰富度显著高于金沙江和澜沧江, 三条江的乔木种丰富度差异则不显著。森林带的样方草本物种丰富度显著低于灌草丛带样方, 并且还拥有后者没有的乔木种。不同样带的植物物种更替速率呈现了不一致的海拔梯度格局, 但均在样带海拔下部的灌草丛群落与海拔上部森林群落之间的交错带出现峰值。森林-灌草丛植被交错带在怒江样带处于海拔1,900-2,100 m处, 在澜沧江河谷位于海拔2,300-2,400 m, 在金沙江河谷位于海拔2,700-2,900 m。所有海拔样带的森林段或灌草丛段相对于同一样带不同植被段之间的物种更替程度为最小, 不仅小于同一流域不同样带相同植被段之间物种更替率的均值, 更小于所有样带相同植被段之间的更替率均值。在三条河流6条海拔样带的12个植被带段之间的物种更替变化中, 空间隔离因素可以解释34.2%, 而植被类型差异仅能解释不到0.5%。本研究结果显示了环境差异对不同植被类型物种丰富度的首要影响, 和各河流之间的空间隔离对植物群落构建和物种构成的主要作用。     

Understorey plant species richness and composition in metropolitan forest archipelagos: effects of forest size, adjacent land use and distance to the edge

Aim To address the relative role of adjacent land use, distance to forest edge, forest size and their interactions on understorey plant species richness and composition in perimetropolitan forests. Location The metropolitan area of Barcelona, north‐eastern Spain. Methods Twenty sampling sites were distributed in two forest size‐categories: small forest patches (8–90 ha) and large forest areas (> 18,000 ha). For each forest‐size category, five sites were placed adjacent to crops and five sites adjacent to urban areas. Vascular plant species were recorded and human frequentation was scored visually in 210 10 × 10 m plots placed at 10, 50 and 100 m from the forest edge, and additionally at 500 m in large forest areas. Plant species were grouped according to their ecology and rarity categories. A nonmetric multidimensional scaling (NMS) ordination was carried out to detect patterns of variation in species assemblage, and to explore the relationships between these patterns and the richness of the species groups and the studied factors. Factorial anovas were used to test the significance of the studied factors on the richness of species groups. Relationships between human frequentation and the studied variables were assessed through contingency tables. Results Forest‐size category was the main factor affecting synanthropic species (i.e. those thriving in man‐made or man‐disturbed habitats). Synanthropic species richness decreased with increasing distance from the forest edge and, when forests were adjacent to crops, it was higher in small forest patches than in large forest areas. Richness of rare forest species was lower in small forest patches than in large forest areas when forests were adjacent to urban areas. Richness of common forest species and of all forest species together were higher close to the forest edge than far from it when forests were adjacent to urban areas. Forests adjacent to urban areas were more likely to experience high human frequentation, particularly in those plots nearest to the forest edge. Main conclusions Forest‐size category and adjacent land use were the most important factors determining species richness and composition. The preservation of large forests adjacent to crops in peri‐urban areas is recommended, because they are less frequented by humans, are better buffered against the percolation of nonforest species and could favour the persistence of rare forest species.     

Local‐ and landscape‐level effects of land use change on bird diversity in Abiata‐Shalla Lakes National Park,Ethiopia

Understanding the effects of anthropogenic disturbances on biodiversity is important for conservation prioritization. This study examined the effects of vegetation degradation on bird diversity in Abiata‐Shalla Lakes National Park, Ethiopia. We surveyed birds and vegetation structure between January and March 2015 in disturbed (impacted by settlement and agriculture) and undisturbed (not impacted) transects of two vegetation types (savannah woodland and gallery forest). We compared between disturbed and undisturbed transects at local (within vegetation types) and landscape (across vegetation types) levels: (a) avian species richness of the entire assemblage and feeding guilds and (b) species assemblage composition. We found significantly greater mean and total bird species richness of the entire assemblage and insectivore and granivore feeding guilds in the undisturbed transects, while the nectarivore guild was totally absent in the disturbed transects. We also found significant differences in bird species assemblage composition between the disturbed and undisturbed transects both within and across the vegetation types, and bird species assemblage composition at the landscape level was positively correlated with tree abundance and understorey vegetation height. In conclusion, our results demonstrate and add to the increasing body of evidence concerning the adverse effects of human‐induced vegetation change on bird diversity.     

Edge effect in different groups of organisms: vascular plant, bryophyte and fungi species richness across a forest-grassland border

Six transects were established on the edges of two deciduous forests near Krosno (Carpathian Foothills) to compare the species richness pattern of vascular plants, bryophytes and fungi. The transects had the shape of a cross with one arm 10 m along the forest edge and the other across the edge, 50 m into the forest interior and 12 m into the grassland. They consisted of 2×2 quadrats. The strongest edge effects were recorded for bryophyte, shrub and tree species richness, the weakest for herbaceous plant species richness. Overall vascular plant species richness and herbaceous species richness were higher in grassland than in the forest and peaked in grassland, 3 m from the forest edge. The shrub species richness was highest 1 m from the edge (in the forest) and the tree species richness 3 m from edge. Bryophyte species richness had roughly the same level across the grassland and within the first several meters of the forest, except for the 2 m zone on the edge itself where species richnes was as low as in the forest interior. Fungi species richness was low in the grassland and on the forest edge and rose dramaticaly a few meters from the edge, ramaining at the same level within the forest. The species composition across the forest-grassland border was analysed using detrended correspondence analysis. It revealed that in the case of bryophytes the increase in species richness did not correspond to a change in species composition, such as might have been caused by a general increase in bryophyte density.     

How forest edge-center transitions in the herb layer interact with beech dominance versus tree diversity

Aims Forest fragmentation and the associated augmentation of forest edge zones are increasing worldwide. Forest edges are characterized by altered plant species richness and community composition. As the tree layer and its species composition has been shown to influence herb layer composition, changes in tree species composition or richness may weaken or strengthen edge effects in forest ecosystems. We studied effects of the edge–center transition, tree species composition and their potential interaction on the understory vegetation in the Hainich National Park, Germany's largest connected deciduous forest, allowing to cover large edge–center transects.Methods We established 12 transects in an area of 75 km 2 of continuous forest, 6 beech-dominated and 6 in multispecies forest stands. Each transect reached from the forest edge up to 500 m into the forest interior. Vegetation relevés were conducted in regular, logarithmic distances along each transect.Important findings Herb species richness was influenced by an interaction of edge effects and tree diversity level. With increasing distance from the forest edge, herb species richness remained constant in multispecies forest stands but rapidly decreased in beech-dominated forest stands. Further, herb richness was higher in the interior of multispecies forest stands. Percent forest specialists increased and percent generalists decreased with distance from the edge and this contrasting pattern was much more pronounced in beech-dominated transects. By using structural equation modeling, we identified litter depth mediated by tree species composition as the most important driver of herb layer plant species richness.     

The effects of urban or rural landscape context and distance from the edge on native woodland plant communities

The increasing rate of urban sprawl continues to fragment European landscapes threatening the persistence of native woodland plant communities. The dynamics of woodland edges depend on the characteristics of woodland patches and also on landscape context. Our aim was to assess the extent of edge influences on the understorey vegetation of small native woodlands in rural and urban landscapes. The study was carried out in two cities of north-western France. Ten comparable woodlands, each of about 1.5 ha, were surveyed; five were situated adjacent to crops and five adjacent to built-up land. Vascular plant species were recorded in 420 3 × 3 m plots placed at seven different distances from the edge (from 0 to about 45 m from the edge). Soil pH, light levels, level of disturbance and tree and shrub cover were also recorded. Plant species were first classified as non-indigenous or indigenous and then three groups of indigenous species were distinguished according to their affinity for forest habitat (forest specialists, forest generalists and non-forest species). We inferred certain ecological characteristics of understorey vegetation by using Ellenberg values. An inter-class correspondence analysis was carried out to detect patterns of variation in plant community composition. Linear mixed models were used to test the effects of adjacent land use, distance from the edge and their interactions on the species richness of the different groups and on the ecological characteristics of vegetation. Total species richness, richness of forest generalists and of non-forest species decreased from edge to interior in both urban and rural woodlands. The number of non-indigenous species depended mainly on urban–rural landscape context. Urban woodland edges were not as rich in forest specialists as rural edges. More surprisingly, the number of forest specialists was higher in rural edges than in rural interiors. Community composition was mainly affected by urban–rural context and to a lesser degree by the edge effect: the community composition of urban edges resembled that of urban interiors whereas in rural woodlands vegetation near edges (up to 10 m) strongly differed from interiors with a pool of species specific to edges. Urban woodland vegetation was more nitrophilous than rural vegetation in both edges and interiors. A major difference between urban and rural vegetation was the distribution of basiphilous species according to distance from the edge. Generally edge vegetation was more basiphilous than interior vegetation however the presence of basiphilous species fell off quickly with distance from the edge in rural woodlands (in the first 10–15 m) and more slowly (from 25 m onwards) in urban woodlands. This pattern was linked to variation in measured soil pH. As regards the conservation of flora in small native woodlands, it appeared that invasion of exotic and non-forest species was currently limited in both urban and rural landscape contexts but might pose problems in the future, especially in urban woodlands. Forest species were not negatively affected by the edge effect and indeed edges seemed to provide important habitats for this group. Hence conservationists should pay particular attention to the protection of edges in urban woodlands.     

Distribution of carabid beetles (Coleoptera: Carabidae) across a forest-grassland ecotone in southwestern China

This paper studied the occurrence of carabid beetles (Coleoptera: Carabidae) in the forest edge, the adjacent forest interior, and the surrounding grassland in southwestern China. Beetles were collected with pitfall traps along five replicated transects. Forest species rarely penetrated into the grassland from the forest interior, and the grassland specialists were not found in the forest interior. The forest edge hosted additional species from the adjacent grassland that increased its overall species richness. Nearly all forest species (23 of 24 species) and grassland species (13 of 15 species) can be found in the forest edge. Carabids of the forest edge were more similar to those of the forest interior than to those of the grassland by ordination and cluster analysis. Based on the specificity and fidelity, carabids can be distinguished into five species groups: habitat generalists, grassland-associated species, forest generalists, forest specialists, and edge-associated species. Multiple linear regression analysis showed that canopy cover and/or shrub cover were the most important factors in determining the richness, abundance, and diversity of carabids. The forest edge may serve as a transition zone for dispersal and re-colonization of carabid beetles from adjacent habitats and therefore is important for natural conservation.     

Elevational gradient and vegetation‐environmental relationships in the central Hyrcanian forests of northern Iran

Tertiary‐relict Hyrcanian (Caspian) forest along the shores of the southern Caspian Sea is a center of biodiversity. Still, there is little information on plant diversity patterns in this area. This study evaluated plant diversity, variation in life forms, and geographical distribution of the zonal vegetation types and their relationships with environmental variables, in the educational and experimental forest of Kheyrudkenar, an important protected area in the central Hyrcanian forest of northern Iran. For this purpose, 226 vegetation plots of 400 m² were laid out along two altitudinal transects from the lowlands (100 m a.s.l.) to the timberline (2000 m a.s.l.). Four vegetation types were identified using modified TWINSPAN, indirect and direct gradient analyses. Species‐related (species diversity indices, life form and phytogeographical elements) and environmental variables (climate, topographic and soil variables) were calculated and subjected to one‐way ANOVA among the vegetation types. Both constrained (CCA) and unconstrained (DCA) ordination analyses showed an almost identical variation of the floristic composition along their axes and demonstrated that there are two main gradients in the Hyrcanian forest. Elevation together with annual precipitation and mean annual temperature were the most important factors controlling the floristic composition in the area. Topographic features such as slope inclination and heat index were found to be important within an elevation zone/vegetation type. Soil physical and chemical properties were of secondary importance for the separation of the vegetation types. This knowledge will be useful for forest management and conservation practices in the Hyrcanian area with its distinct and unique flora and vegetation.     

Relationships between seed banks and spatial heterogeneity of North American alvar vegetation

Abstract. This is the first quantitative study of seed bank characteristics in North American alvar habitats. We assessed seed bank density, species richness, and species composition in 75 plots distributed among five alvar sites in Bruce Peninsula National Park, Ontario, Canada, each of which displayed areas of high and low vegetation cover within the alvar and a fully forested perimeter area. Forested habitats immediately adjacent to alvar patches contained minimal seed banks for species restricted to the alvar patches. Open alvars contained less than 1% seeds from woody forest species. This suggests that forest is not invading adjacent alvar habitat via seeds and that adjacent forest does not contain a reservoir of alvar seeds. When compared to areas on the alvar with high vascular plant cover, areas with low cover contained a slightly smaller viable seed bank, but seed banks from high and low vegetation cover plots had similar species composition and species richness. High vegetation cover plots had slightly higher mean and maximum soil depths compared with low cover plots, but no differences in other physical and chemical parameters. Thus, spatial heterogeneity in plant cover is associated only weakly with heterogeneity in below‐ground factors. Despite the availability of seed and soil resources, vegetation dynamics are constrained in areas with low plant cover, and thus alvar community development seems to respond non‐linearly to resource availability.     

Species-richness patterns of vascular plants along seven altitudinal transects in Norway

Altitudinal richness patterns were investigated along altitudinal gradients located in northern Norway (two transects) and along a west–east gradient in southern Norway (five transects). The transects were sampled for vascular plant species richness using a uniform sampling method. Each transect consisted of 38–48 5×5 m sample plots regularly spaced from sea level or valley bottom to a local mountain top. In five transects species richness peaked at mid-altitudes, whereas in the two northern transects species richness decreased with altitude. The observations were qualitatively evaluated in relation to the influence of the area of the species pool, hard boundaries, temperature and precipitation, and mass effect. The observed patterns cannot be fully accounted for by any of these factors. However, the altitude of the peak in species richness was above the forest-limit for all the humped relationships, which may suggest that species richness above the forest-limit might be enhanced by a mass effect from forest taxa. The two monotonic relationships found in the north may be caused by the relatively low number of alpine species at these sites. The monotonic pattern may result from a decrease in "forest species" towards the mountain tops.     

Long‐term seed bank dynamics in a temperate forest under conversion from coppice‐with‐standards to high forest management

Questions: How do changes in forest management, i.e. in disturbance type and frequency, influence species diversity, abundance and composition of the seed bank? How does the relationship between seed bank and vegetation change? What are the implications for seed bank dynamics? Location: An ancient Quercus petraea — Carpinus betulus forest in conversion from coppice‐with‐standards to regular Quercus high forest near Montargis, France. Methods: Seed bank and vegetation were sampled in six replicated stand types, forming a chronosequence along the conversion pathway. The stand types represented mid‐successional stages of stands in transition from coppice‐with‐standards (to high forest (16 plots) and early‐ and mid‐successional high forest stands (32 plots). Results: Seed bank density and species richness decreased with time since last disturbance. Adjusting for seed density effects obscured species richness differences between stand types, but species of later seres were nested subsets of earlier seres, implying concomitant shifts in species richness and composition with time since disturbance. Later seres were characterized by species with low seed weight and high seed longevity. Seed banks of early seres were more similar to vegetation than to later seres. Conclusions: Abandonment of the coppice‐with‐standards regime altered the seed bank characteristics, as well as its relationship with vegetation. Longer management cycles under high forest yield impoverished seed banks. For their persistence, seed bank species will increasingly rely on management of permanently open areas in the forest landscape. Thus, revegetation at the beginning of new high‐forest cycles may increasingly depend on inflow from seed sources.     

The spatial configuration of taxonomic biodiversity along a tropical elevational gradient: α‐, β‐, and γ‐partitions

Biodiversity at larger spatial scales (γ) can be driven by within‐site partitions (α), with little variation in composition among locations, or can be driven by among‐site partitions (β) that signal the importance of spatial heterogeneity. For tropical elevational gradients, we determined the (a) extent to which variation in γ is driven by α‐ or β‐partitions; (b) elevational form of the relationship for each partition; and (c) extent to which elevational gradients are molded by zonation in vegetation or by gradual variation in climatic or abiotic characteristics. We sampled terrestrial gastropods along two transects in the Luquillo Mountains. One passed through multiple vegetation zones (tabonuco, palo colorado, and elfin forests), and one passed through only palm forest. We quantified variation in hierarchical partitions (α, β, and γ) of species richness, evenness, diversity, and dominance, as well as in the content and quality of litter. Total gastropod abundance linearly decreased with increasing elevation along both transects, but was consistently higher in palm than in other forest types. The gradual linear decline in γ‐richness was a consequence of opposing patterns with regard to α‐richness (monotonic decrease) and β‐richness (monotonic increase). For evenness, diversity, and dominance, α‐partitions and γ‐partitions evinced mid‐elevational peaks. The spatial organization of gastropod biodiversity did not mirror the zonation of vegetation. Rather, it was molded by: (a) elevational variation in productivity or nutrient characteristics, (b) the interspersion of palm forest within other forest types, and (c) the cloud condensation point acting as a transition between low and high elevation faunas. Abstract in Spanish is available with online material.     

A comparison of the vegetation of forested and non-forested solution dolines in Hungary: a preliminary study

The present study compares the vegetation characteristics of two large forested and one large non-forested solution dolines in Hungary. We investigated the species composition and vegetation pattern along north to south transects (across the doline bottoms) and compared the richness of different species groups (dry and wet groups) on the doline slopes. We applied linear regression models for each slope to explore the effects of topography on species richness, and Detrended Correspondence Analysis (DCA) to detect the major gradients of floristic variation within each site. We found that the vegetation changed significantly along all transects; and, regardless of the vegetation cover, the doline bottoms contained several cool-adapted species. Variations within the two species groups were more pronounced on the south-facing slopes. The changes were similar in the forested dolines, indicating the role of forest cover in maintaining many cool-adapted species on the north-facing slopes as well. However, the number of cool-adapted species increased significantly along both slopes of the non-forested doline from the upper edge to the bottom. Contrary to our expectations, the species turnover along the slopes of the non-forested doline was lower than that along the slopes of the forested ones. We conclude that both the forested and non-forested dolines serve as refuges for many plant species adapted to different environmental conditions. Apart from providing an understanding of population patterns along environmental gradients, our results may also contribute to our understanding of an even more fundamental question for a future research agenda: the probable effects of climate change on vegetation characteristics in climatic islands with environmental conditions substantially different from the surrounding areas.     

Stability of plant communities along a tropical inselberg ecotone in French Guiana (South America)

We questioned whether and how plant communities vary in space and time along an inselberg-rainforest ecotone in relation to present-day warming and whether biotic and non-biotic factors could explain the observed patterns. The study took place on a granitic inselberg in the French Guianan (South America) rainforest (Nouragues Natural Reserve: 4°5′N, 52°41′W). In a diachronic study (1995–2005) embracing a severe El-Niño event in 1997, we analysed vegetation structure and composition along three transects subsuming whole environmental and topographical variations in the transition zone from shrub vegetation at the fringe of open-rock vegetation to tall-tree rainforest. Data were analysed by PCA. Major variations in species and trait distribution were described in the low forest, with two floristic types evidenced by first PCA component and verified by cluster analysis: one with floristic composition reminiscent of open-rock vegetation but with higher and continuous canopy, the other typical of the low forest. There is no clear-cut boundary between typical open-rock and low forest vegetation. Variation in species composition of typical low forest was evidenced by second PCA component, which displayed differences according to slope and altitude. Small (∼1.5 m), although significant, shifts in the spatial distribution of plant species pointed to possible slow encroachment of typical low forest vegetation in the absence of disturbance. However, the stability of species and trait distribution was remarkable within the 10-yr interval considered, despite an otherwise recorded decrease in species richness and recruitment. The boundary between typical low forest and open-rock-like vegetation coincided with the spatial limit of the mineral soil above granite. Despite demographic accidents due to severe El Niño events, plant communities at the fringe of a tropical inselberg are stable at short-time both in composition and spatial distribution. In the absence of strong disturbances such as wildfire and further erosion, soil availability for roots could be interpreted as an environmental constraint to the successional development of forest vegetation. Soil development might thus act as an ecological barrier to forest encroachment, which could only be alleviated by erosion recovery, as otherwise demonstrated.     

Forest classification in an Amazonian rainforest landscape using pteridophytes as indicator species

Habitat classification systems are poorly developed for tropical rainforests, where extremely high plant species richness causes numerous methodological difficulties. We used an indicator species approach to classify primary rainforest vegetation for purposes of comparative wildlife habitat studies. We documented species composition of pteridophytes (ferns and fern allies) in 635 plots (2×100 m) along 8 transects within a continuous rainforest landscape in northeastern Peruvian Amazonia. Considerable floristic variation was found when the data were analyzed using multivariate methods. The obtained forest classification was interpreted with the help of indicator value analysis and known soil preferences of the pteridophyte species. The final classification included four forest types: 1) inundated forests, 2) terrace forests, 3) intermediate tierra firme forests and 4) Pebas Formation forests. This rapid and relatively simple vegetation classification technique offers a practical, quantitative method for large-scale vegetation inventory in complex rainforest landscapes.     

Taxonomic diversity as complementary information to assess plant species diversity in secondary vegetation and primary tropical deciduous forest

Question: Species diversity is commonly expressed as the number of species present in an area, but this unique value assumes that all species contribute equally to the area's biodiversity. Can taxonomic diversity be used as a complementary measure for species richness in order to assess plant biodiversity in remnants of primary forest and patches of secondary vegetation? Location: Veracruz, Mexico. Methods: Using data from six sampling transects of each vegetation type in an elevation gradient (400‐900 m a.s.l.), we compare the point, mean and cumulative floristic diversity of primary forest and secondary vegetation in a tropical deciduous landscape, using species richness and two measures of taxonomic diversity: average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+). We performed a randomization test to detect differences in the observed taxonomic diversity, from the expected values derived from the species pool of each vegetation type. Results: We found that the species of secondary vegetation are more closely related at low taxonomic levels (lower Δ+ value) than the species of primary forest remnants. Also, in secondary vegetation the distribution of species is uneven among the taxonomic levels and units (high Λ+ value). These patterns are consistent for point, mean and cumulative taxonomic diversity. Families Asteraceae, Euphorbiaceae, Fabaceae and Poaceae are over‐represented, while families Bromeliaceae, Cactaceae, Orchidaceae and Pteridaceae are under‐represented in secondary vegetation. Conclusions: Although in a previous paper we concluded that secondary vegetation is more alpha‐diverse than primary forest (in terms of both cumulative and mean species richness), and beta‐diversity between vegetation types is notoriously high, we now provide a wider view by highlighting the importance of taxonomic diversity in primary forest remnants. Our data indicate that to measure biodiversity accurately, we should seek to capture its different facets. This will allow us to make conservation recommendations based on a broader view, and not on a single dimension.     

Diversity patterns in sandy forest-steppes: a comparative study from the western and central Palaearctic

The Palearctic forest-steppe biome is a narrow vegetation zone between the temperate forest and steppe biomes, which provides important habitats for many endangered species and represents an important hotspot of biodiversity. Although the number of studies on forest–grassland mosaics is increasing, information currently available about the general compositional and structural patterns of Eurasian forest-steppes is scarce. Our study aimed to compare the habitat structure, species composition and diversity patterns of two distant sandy forest-steppes of Eurasia. We compared 72 relevés made in the main habitat components (forest, forest edge and grassland) of sandy forest-steppes in three Hungarian and three Kazakh sites. The size of the plots was 25 m². Species number, Shannon diversity and species evenness values were calculated for each plot. Fidelity calculations and linear mixed effects models were used for the analyses. We found that the vegetation and diversity patterns of the two forest-steppes are similar and their components play important roles in maintaining landscape-scale diversity. Despite the higher species richness in Hungary, Shannon diversity was higher in Kazakhstan. The deciduous forest edges of both areas had significantly higher species richness than the neighbouring habitats (forests and grasslands); therefore they can be considered local biodiversity hotspots. Due to the special characteristics of this vegetation complex, we emphasize the high conservation value of all landscape components as a coherent system throughout the entire range of the Eurasian forest-steppe biome.     

How does forest landscape structure explain tree species richness in a Mediterranean context?

Although the strong relationship between vegetation and climatic factors is widely accepted, other landscape composition and configuration characteristics could be significantly related with vegetation diversity patterns at different scales. Variation partitioning was conducted in order to analyse to what degree forest landscape structure, compared to other spatial and environmental factors, explained forest tree species richness in 278 UTM 10 × 10 km cells in the Mediterranean region of Catalonia (NE Spain). Tree species richness variation was decomposed through linear regression into three groups of explanatory variables: forest landscape (composition and configuration), environmental (topography and climate) and spatial variables. Additionally, the forest landscape characteristics which significantly contributed to explain richness variation were identified through a multiple regression model. About 60% of tree species richness variation was explained by the whole set of variables, while their joint effects explained nearly 28%. Forest landscape variables were those with a greater pure explanatory power for tree species richness (about 15% of total variation), much larger than the pure effect of environmental or spatial variables (about 2% each). Forest canopy cover, forest area and land cover diversity were the most significant composition variables in the regression model. Landscape configuration metrics had a minor effect on forest tree species richness, with the exception of some shape complexity indices, as indicators of land use intensity and edge effects. Our results highlight the importance of considering the forest landscape structure in order to understand the distribution of vegetation diversity in strongly human-modified regions like the Mediterranean.