Components Of Plant Diversity Research Articles

Assessing the impact of land use change on different components of plant diversity in a tropical montane cloud forest of Mexico

Assessing the impact of land use change on different components of plant diversity in a tropical montane cloud forest of Mexico

Landscape-driven effects on taxonomic, functional, and phylogenetic diversity of vegetation developing on sand-gravel pits of early successional stages

Among the key drivers of the progressive transformation of biomes are mining activities, usually leading to the establishment of novel ecosystems, characterized by new species assemblages, combinations of habitats, and unprecedented functioning. It remains unknown how the composition of surrounding land cover may influence species composition, community assembly processes, and the phylogenetic relatedness structure of vegetation developing spontaneously on these de novo established biological systems. In this study, I investigated the influence of different landscape types in the proximity of 31 sand-gravel pits of pioneer successional stages on vegetation's taxonomical, functional, and phylogenetic diversity. Further, I accounted for the effects of the surrounding landscape on ten ecological groups of plant species, and biotic novelty indices as a supporting explanation of mechanisms shaping the species' co-occurrence patterns. I explored that plants' functional and phylogenetic diversity was higher in pits surrounded by riverine landscape, and lower if the contribution of settlements in the surrounding landscape was higher. Both landscape features promoted the occurrence of exotic species on sand-gravel pits, but only the settlements' proportion exerted a positive effect on biotic novelty indices. On the other hand, pits with a prevalence of forests in the surroundings were dominated by phylogenetically diverse, but functionally more homogenous native taxa, reflected, inter alia, in negative effects of forests on biotic novelty indices. Comprehensive assessment of the impacts of the surrounding landscape on different components of plant diversity may be used as a useful predictor in the exploration of successional trajectories, as well as a helpful tool in the formulation of strategies for mining-transformed ecosystems management.

Characterizing and Quantifying Water Content in 14 Species of Bryophytes Present in Azorean Native Vegetation

Bryophytes are an important component of plant diversity, may be found from sea level to mountaintops, and are particularly conspicuous on the Azores islands. These plants rely on environmental water, which acquires intercepting rain and dew (liquid water) and uses fog (water vapor), and transports both externally, by capillary forces, and internally, in different cells (specialized or not). This study characterizes and quantifies the ability of six liverworts and eight mosses to retain water, through different pathways, and to lose water by evaporation. Twelve replicates of each species were collected in Azorean native vegetation during the summer of 2016. The absolute water content (AWC) was obtained through measurements of specimens saturated, without free water, and completely dry. Most of the 14-target species showed an ectohydric behavior pattern retaining more than 60% of water through gametophyte surface. The AWC value ranged from 646% in Polytrichum commune to 5584% in Sphagnum subnitens. The water loss by direct evaporation showed, for most of species, an exponential decay curve along time. Understanding how much native bryophytes, acquire, store, and release water into the system contributes not only to the knowledge of native vegetation resilience but also to potential impacts on the availability and quality of water—a major ecosystem service performed by bryophytes.

Changes in rainfall amount and seasonality modulate taxonomic, functional, and phylogenetic diversity in a gypsophilous plant community in the Chihuahuan Desert

ABSTRACT Background Climate change is expected to alter future rainfall regime in arid zones, which may impact gypsophilous plant diversity components in the Chihuahuan Desert. Aims We investigated the effects of different rainfall timings and amounts on the taxonomic, functional, and phylogenetic components of a gypsophilous plant community. Methods We used soil monoliths extracted from the southern Chihuahuan Desert in a greenhouse experiment with three rainfall timings (typical, early, and late) and two rainfall amounts (100% and 50%) and evaluated the effects on taxonomic, functional, and phylogenetic diversity. Results Irrigation treatment with 50% of average rainfall reduced species richness and plant abundance and altered species composition. At 100% irrigation, specific leaf area was lower in the treatments with typical and late rainfall timing than in the treatment with early rainfall. Phylogenetic diversity was significantly lower in the late timing treatment in November. Conclusion Our study evidence that the water shortage impacted drastically on the plant community by decreased species richness and diversity. Nevertheless, late rainfall can buffer the effects of water diminution but only on taxonomic and functional diversity, with the opposite effect on the phylogenetic diversity, in the gypsophilous communities in the Chihuahuan Desert.

Complex ecological and socioeconomic impacts on medicinal plant diversity.

Medicinal plant diversity (MPD) is an important component of plant diversity. Over-collection based on medicinal and economic value has the potential to damage the stability of the regional ecosystem. It is important to understand the current distribution of MPD and the factors influencing it. However, it is still unclear whether environmental and socioeconomic conditions have an impact on their distribution. We selected the Inner Mongolia as a representative study area which covers a wide area, accounting for 12.29% of China's national land area and 0.79% of the world's land area. At the same time, the region is a long-standing traditional medicinal area for Mongolians in China. Therefore, the region is significantly influenced by changes in environmental factors and socio-economic factors. We used 9-years field survey of the distribution of medicinal plants in Inner Mongolia for assessing the distribution of MPD as influenced by environmental and socioeconomic activities by combining spatial analyses, species distribution models, and generalized additive models. The results from the spatial analysis show that the western region of Inner Mongolia is the main cold spot area of the MPD, and the central-eastern and northeastern regions of Inner Mongolia are the main hot spot areas of the MPD. At the same time, the distribution of cold spots and hot spots of MPD is more obvious at large spatial scales, and with the refinement of spatial scales, the cold spots in scattered areas are gradually revealed, which is indicative for the conservation and development of MPD at different spatial scales. Under the future climate change of shared socioeconomic pathways (SSP), areas with high habitat suitability for medicinal plants remain mainly dominated by the Yellow River, Yin Mountains, and Greater Khingan Range. Notably, the SSP245 development pathway remains the most significant concern in either long- or short-term development. The nonlinear relationship between the driving factors of MPD at different spatial scales shows that temperature, precipitation and socioeconomic development do have complex effects on MPD. The presence of a certain temperature, altitude, and precipitation range has an optimal facilitation effect on MPD, rather than a single facilitation effect. This complex nonlinear correlation provides a reference for further studies on plant diversity and sustainable development and management. In this study, the spatial distribution of medicinal plant resources and the extent to which they are driven by ecological and socioeconomic factors were analyzed through a macroscopic approach. This provides a reference for larger-scale studies on the environmental and socioeconomic influences on the distribution of plant resources.

Plant diversity components of agroforestry in Tanjung Botung, Village, Barumun District, Padang Lawas Regency, North Sumatra

Agroforestry is a land-use pattern that combines crops in one land with spatial and temporal arrangements. This study aims (1) to identify the species components of agroforestry, (2) to analysis the species diversity in agroforestry, and (3) to calculate the benefits of species in agroforestry for the community around Tanjung Botung Village. Based on the results in this research, it is known that there are 33 species of plants found in agroforestry land which consists of 19 families. To determine the type that dominates the growth rate, it is seen from the value of the Important Value Index. The highest IVI level was in the shurbs level namely Elaeis guineensis (56.67), in the seedling level namely Hevea brasiliensis (83.57), in the sapling level namely Durio zibethinus (38.37), in the pole level namely Hevea brasiliensis (68.04) and in tree level namely Hevea brasiliensis (99.69). To find out the level of species diversity was calculated using the Shannon-Wiener Index (H’). From the results of the study, it was concluded that the value of species diversity ranged from 1.63 to 2.35, meaning that the value of species diversity (H’) for all growth levels was categorized as moderate.

Components of plant diversity as ecological indicators reflecting the effects of conservation management and degradation in different climatic conditions

AbstractAdditive partitioning of species diversity is a valuable approach for quantifying the spatial patterns of biodiversity sampled in hierarchically scaled studies. This approach may provide key insights into vegetation community restoration following terrestrial ecosystems degradation in different climatic conditions. The scale‐dependence of plant diversity in relation to different plant functional groups (e.g., herbaceous and woody) is still little understood. This research aims to investigate the influence of management options (protected vs. non‐protected) and climatic conditions (semiarid vs. Mediterranean) on different components of diversity in both herbaceous and woody species derived from local and regional scales (i.e., plot and site, respectively). In the studied areas, a total of 64 plots (1000 m2) at local scale and 128 micro‐plots (1 m2) among 16 sites at regional scale were selected for sampling the woody and herbaceous species data, respectively, by using a hierarchical sampling design. Diversity components of local (α1, β1) and regional (α2, β2) scales were extracted according to additive partitioning method. Differences in diversity component (α1, α21, β1 and β2) and floristic composition between management options and climatic conditions were evaluated using GLMM and DCA. The results indicate that all components of total species (both herbaceous and woody) diversity (α1, α2, β1 and β2) were significantly influenced by management options (p < 0.05) with greater values in the protected areas than the non‐protected areas. However, the climatic conditions only had significant effects on β2, with greater values in the Mediterranean compared to semi‐arid areas. Moreover, the separate analysis of herbaceous and woody species indicated that management options have a greater significant effect on different diversity components compared to the climatic condition. Detrended correspondence analysis showed that floristic variations along the axes are strongly affected by management in both climatic conditions. This indicates that protection measures mostly increased plant species diversity at the local and regional scales, which is independent of the climatic condition.

The relative and combined effects of herbivore assemblage and soil nitrogen on plant diversity.

Plant diversity can be affected by both herbivore grazing and soil resources. However, it is unclear if the joint effects of herbivores and soil resources might vary with components of plant diversity. Here, we evaluated the relative and combined effects of herbivore assemblage and soil nitrogen (N) quantity and heterogeneity on the α and β components of plant diversity in a grassland that was subjected to four years of grazing under differing herbivore assemblages (no grazing, cattle grazing, sheep grazing, and mixed grazing). We found that herbivore assemblage combined with soil N quantity explained 41% of the variation in plant α-diversity, while herbivore assemblage combined with soil N heterogeneity explained 15% of the variation in plant β-diversity. The independent effects of herbivore assemblage explained more than those of soil N for both α- and β-diversity (α-diversity: 12% vs. 4%; β-diversity: 18% vs. 16%). We concluded that the effects of herbivores are stronger than those of soil N, and that grazing-induced changes in soil resources are important drivers of plant diversity change, especially α-diversity. Therefore, we suggest that managing herbivore species by accounting for the effects that their grazing can have on soil resources may be significant for plant diversity maintenance.

Investigating the Relationship between Tree Species Diversity and Landsat-8 Spectral Heterogeneity across Multiple Phenological Stages

The emergence of the spectral variation hypothesis (SVH) has gained widespread attention in the remote sensing community as a method for deriving biodiversity information from remotely sensed data. SVH states that spectral heterogeneity on remotely sensed imagery reflects environmental heterogeneity, which in turn is associated with high species diversity and, therefore, could be useful for characterizing landscape biodiversity. However, the effect of phenology has received relatively less attention despite being an important variable influencing plant species spectral responses. The study investigated (i) the effect of phenology on the relationship between spectral heterogeneity and plant species diversity and (ii) explored spectral angle mapper (SAM), the coefficient of variation (CV) and their interaction effect in estimating species diversity. Stratified random sampling was adopted to survey all tree species with a diameter at breast height of > 10 cm in 90 × 90 m plots distributed throughout the study site. Tree species diversity was quantified by the Shannon diversity index (H′), Simpson index of diversity (D2) and species richness (S). SAM and CV were employed on Landsat-8 data to compute spectral heterogeneity. The study applied linear regression models to investigate the relationship between spectral heterogeneity metrics and species diversity indices across four phenological stages. The results showed that the end of the growing season was the most ideal phenological stage for estimating species diversity, following the SVH concept. During this period, SAM and species diversity indices (S, H′, D2) had an r2 of 0.14, 0.24, and 0.20, respectively, while CV had an r2 of 0.22, 0.22, and 0.25, respectively. The interaction of SAM and CV improved the relationship between the spectral data and H′ and D2 (from r2 of 0.24 and 0.25 to r2 of 0.32 and 0.28, respectively) at the end of the growing season. The two spectral heterogeneity metrics showed differential sensitivity to components of plant diversity. SAM had a high relationship with H′ followed by D2 and then a lower relationship with S throughout the different phenological stages. Meanwhile, CV had a higher relationship with D2 than other plant diversity indices and its relationship with S and H′ remained similar. Although the coefficient of determination was comparatively low, the relationship between spectral heterogeneity metrics and species diversity indices was statistically significant (p < 0.05) and this supports the assertion that SVH could be implemented to characterize plant species diversity. Importantly, the application of SVH should consider (i) the choice of spectral heterogeneity metric in line with the purpose of the SVH application since these metrics relate to components of species diversity differently and (ii) vegetation phenology, which affects the relationship that spectral heterogeneity has with plant species diversity.

Borealization and its discontents: drivers of regional variation in plant diversity across scales in interior Alaska

AbstractQuantitative studies of regional variation in plant diversity across eastern Beringia (northern Alaska and adjacent areas) are lacking due to an absence of datasets of sufficient scale and scope. We interrogated a landscape‐scale plant diversity dataset collected across two regions of interior Alaska with different disturbance, topographic, and climate attributes to investigate hypotheses regarding drivers of plant species richness. Our approach integrated a multi‐scale sampling design with an analytical framework focused on quantifying how components of plant diversity (growth forms, biogeographic groups, and dominant species) respond to site factors that vary along landscape gradients. Our results revealed essential similarities in both the composition of the overall floras and the influences on local and meso‐scale species richness across both regions. However, these continuities at smaller scales contrasted with differences in landscape‐level distribution of plant diversity patterns along elevation gradients. Our findings suggest that local drivers of richness and occupancy interacted with differing macro‐scale attributes (e.g., relative continentality) to produce distinctive landscape‐level diversity patterns. Our results confirm that high levels of local and meso‐scale plant richness in interior Alaska depend on conditions that foster richness of herbaceous and northerly distributed species groups. However, we found that important differences in landscape‐level richness patterns were driven by regional differences in climate, topoedaphic variables, and disturbance. In the warmer region, woody species and boreal plant communities extended to higher elevations and common species occupancy showed marginally greater influence of fire. Overall richness was relatively low in alpine areas of the warmer region but heterogeneous edaphic and topographic circumstances stimulated higher species turnover in lower elevations there, increasing landscape‐level richness. In contrast, in the cooler region, woody species showed restricted distribution across the elevation gradient while site attributes associated with increased species richness aligned with the elevation gradient and thus peak richness occurred in the alpine zone. Our results show how total and growth‐form richness, as well as community composition, vary regionally in relation to important drivers (including growing season warmth) across interior Alaska. Consequently, our study provides new insights into the potential trajectories of future change in biodiversity patterns in this rapidly warming region.

Climatic condition effects on the components of plant diversity in the western Iran grasslands using multiplicative partitioning methods

This study aimed to investigate the effects of different climatic conditions (arid vs. semi-arid) on patterns of species richness and plant diversity as well as plant composition in two over-grazed regions. The regions were located in the west of Iran, closed to each other and different in climatic conditions. Based on the aridity index of De Martonne climate classification, Rika (I = 9.94) and Dalab (I = 18.54) were categorized as arid and semi-arid regions, respectively. In each region, we collected plant vegetation data from a nested sampling design consisted of local (80 plots) and regional (8 sites) scales. Patterns of plant diversity and species richness in each region, and similarity of plant composition between the two regions were analyzed using multiplicative partitioning methods, species richness estimator and cluster analysis, respectively. The results showed that diversity components in all scales had significant difference with their expected values (p <0.000) resulted in non-random distribution of plant species among and within scales. In addition, the results showed that species richness in Rika region (arid, 89 species) was greater than Dalab region (semi-arid, 76 species). The results of cluster analysis suggested that Rika and Dalab regions had different plant species compositions. Based on our results, the role of seed dispersal might be more prominent in smaller scales (plot and sites) compared to region scale, since the highest possible amount of β-diversity was occurred between regions. Our results suggested that plant diversity in the largest scale (region) had the highest amount of diversity components where the rangeland manager should attend on this scale for conservation of plant diversity.

Does β diversity predict ecosystem productivity better than species diversity?

There is consensus that greater biodiversity is essential to maintain the ecosystem function and stability. Variation in spatial plant community heterogeneity (β diversity) affects productivity and ecosystems function; however, relatively few studies have addressed how β diversity and its components (i.e. species turnover and nestedness) may relate to ecosystems function. In this study, we assessed plant community diversity (richness and evenness) and spatial heterogeneity along a productivity gradient in different bioclimatic regions including desert-steppe, steppe, semi-steppe and Mediterranean rangelands in south west of Iran, and tested (1): how and to what extent the different components of plant diversity affect aboveground biomass (AGB; as ecosystem productivity) and (2): the mechanisms underlying the relationship between β diversity and ecosystem productivity; i.e. niche complementary and selection effects. Sampling was executed in each bioclimatic region by choosing eight sites and estimating AGB of plant species in 2 × 2 m plots nested within 3 macro plots of 30 × 30 m.The results showed that AGB was significantly predicted by species richness; positively in desert-steppe, steppe and semi-steppe rangelands and negatively in Mediterranean rangeland. Furthermore, AGB was negatively predicted by evenness in desert-steppe and semi-steppe rangelands. There were significantly negative relationships between β diversity and AGB in desert-steppe, steppe and semi-steppe rangelands, while, the significantly positive relationship was found for Mediterranean rangeland. The AGB was significantly and positively related to the turnover and nestedness components of β diversity in Mediterranean rangeland. However, a negative relationship was found with turnover in desert-steppe and semi-steppe rangelands.Our results indicate that niche complementarity may play a critical role in providing and provision ecosystems productivity in steppe and Mediterranean rangelands, while, both selection effects and niche complementarity hypotheses could be verified in low-productive regions (desert-steppe and semi-steppe rangelands). Comparing the strength of species diversity with β diversity in predicting ecosystems productivity across different bioclimatic regions, our results revealed that β diversity predict ecosystems productivity more effectively and provide support for biodiversity-ecosystems function theories.

Tree longevity drives conservation value of shade coffee farms for vascular epiphytes

Forest loss and fragmentation threaten the high diversity of tropical forests. Tropical epiphytes are a key component of plant diversity and significant for ecosystem functioning, and they are vulnerable to these forces. We explored the potential of shade trees in agroforestry systems to sustain and restore epiphyte communities where forest cover has been lost. We investigated epiphyte colonization patterns using surveys of 748 trees within 87 variously-aged plots in coffee agroecosystems in northern Nicaragua. Species richness increased with stand age, reflecting effects of area, time, and the niche differentiation possible within larger trees. Young trees near mature trees were almost five times more likely to support epiphytes than those surrounded by other young trees, suggesting that propagule sources severely limit colonization in young, even-aged stands. We identified three stages of epiphyte colonization: an initial stage where trees lack epiphytes; a colonization stage where epiphyte abundance increases slowly; and a mature stage where accumulation accelerates as trees become large enough to support distinct microhabitats. Atmospheric bromeliads and several fern species with traits that facilitate dispersal, colonization, and persistence under open, sunny environmental conditions colonized young trees first. Thus, both environmental filtering and dispersal limitation drive community assembly in these agroforests. Because epiphytes colonize gradually, consistent land tenure and long-term management allow time for newly planted trees in shade coffee farms to develop to the size and structural complexity needed to support diverse epiphyte communities. Because ideal conditions for epiphytes may be at odds with managing for maximum coffee yields and some epiphyte species may never colonize coffee farms, even mature shade trees in coffee plantations cannot replace protecting native forests.

Configurational crop heterogeneity increases within‐field plant diversity

Abstract Increasing landscape heterogeneity by restoring semi‐natural elements to reverse farmland biodiversity declines is not always economically feasible or acceptable to farmers due to competition for land. We hypothesized that increasing the heterogeneity of the crop mosaic itself, hereafter referred to as crop heterogeneity, can have beneficial effects on within‐field plant diversity. Using a unique multi‐country dataset from a cross‐continent collaborative project covering 1,451 agricultural fields within 432 landscapes in Europe and Canada, we assessed the relative effects of compositional and configurational crop heterogeneity on within‐field plant diversity components. We also examined how these relationships were modulated by the position within the field. We found strong positive effects of configurational crop heterogeneity on within‐field plant alpha and gamma diversity in field interiors. These effects were as high as the effect of semi‐natural cover. In field borders, effects of crop heterogeneity were limited to alpha diversity. We suggest that a heterogeneous crop mosaic may overcome the high negative impact of management practices on plant diversity in field interiors, whereas in field borders, where plant diversity is already high, landscape effects are more limited. Synthesis and applications. Our study shows that increasing configurational crop heterogeneity is beneficial to within‐field plant diversity. It opens up a new effective and complementary way to promote farmland biodiversity without taking land out of agricultural production. We therefore recommend adopting manipulation of crop heterogeneity as a specific, effective management option in future policy measures, perhaps adding to agri‐environment schemes, to contribute to the conservation of farmland plant diversity.

Legumes regulate grassland soil N cycling and its response to variation in species diversity and N supply but not CO2.

Legumes are an important component of plant diversity that modulate nitrogen (N) cycling in many terrestrial ecosystems. Limited knowledge of legume effects on soil N cycling and its response to global change factors and plant diversity hinders a general understanding of whether and how legumes broadly regulate the response of soil N availability to those factors. In a 17-year study of perennial grassland species grown under ambient and elevated (+180ppm) CO2 and ambient and enriched (+4gNm-2 year-1 ) N environments, we compared pure legume plots with plots dominated by or including other herbaceous functional groups (and containing one or four species) to assess the effect of legumes on N cycling (net N mineralization rate and inorganic N pools). We also examined the effects of numbers of legume species (from zero to four) in four-species mixed plots on soil N cycling. We hypothesized that legumes would increase N mineralization rates most in those treatments with the greatest diversity and the greatest relative limitation by and competition for N. Results partially supported these hypotheses. Plots with greater dominance by legumes had greater soil nitrate concentrations and mineralization rates. Higher species richness significantly increased the impact of legumes on soil N metrics, with 349% and 505% higher mineralization rates and nitrate concentrations in four-species plots containing legumes compared to legume-free four-species plots, in contrast to 185% and 129% greater values, respectively, in pure legume than nonlegume monoculture plots. N-fertilized plots had greater legume effects on soil nitrate, but lower legume effects on net N mineralization. In contrast, neither elevated CO2 nor its interaction with legumes affected net N mineralization. These results indicate that legumes markedly influence the response of soil N cycling to some, but not all, global change drivers.

Multiple plant diversity components drive consumer communities across ecosystems

Humans modify ecosystems and biodiversity worldwide, with negative consequences for ecosystem functioning. Promoting plant diversity is increasingly suggested as a mitigation strategy. However, our mechanistic understanding of how plant diversity affects the diversity of heterotrophic consumer communities remains limited. Here, we disentangle the relative importance of key components of plant diversity as drivers of herbivore, predator, and parasitoid species richness in experimental forests and grasslands. We find that plant species richness effects on consumer species richness are consistently positive and mediated by elevated structural and functional diversity of the plant communities. The importance of these diversity components differs across trophic levels and ecosystems, cautioning against ignoring the fundamental ecological complexity of biodiversity effects. Importantly, plant diversity effects on higher trophic-level species richness are in many cases mediated by modifications of consumer abundances. In light of recently reported drastic declines in insect abundances, our study identifies important pathways connecting plant diversity and consumer diversity across ecosystems.

Multifaceted Analysis of Patch-Level Plant Diversity in Response to Landscape Spatial Pattern and History on Mediterranean Dunes

Landscape structure is known to critically affect biodiversity. However, although the multi-facetted character of biodiversity is widely recognized, few studies have linked landscape spatial pattern and history simultaneously to multiple facets (taxonomic, functional, and phylogenetic) and spatial components (α, β, and γ) of plant diversity. We set out to reveal whether landscape parameters have specific effects on the separate diversity facets and components of plant diversity at a patch scale on coastal dune landscapes of Central Italy. For each landscape patch, we computed a set of patch-based metrics relying on multi-temporal land-cover maps. Based on a database of plant community plots, on functional traits from field measurements and on a dated phylogenetic tree, we calculated taxonomic (TD), functional (FD), and phylogenetic diversity (PD) within each patch at α, β, and γ level. Diversity measures were then related to the landscape metrics via linear mixed-effect models. Landscape pattern and transformations affected TD only moderately in coastal dune ecosystems. We found much stronger and contrasted effects on FD and PD. FD increased in patches surrounded by human-dominated habitats; PD was higher in fragmented patches, particularly in the Mediterranean macchia. Moreover, landscape pattern affected differently the single communities, the turnover among communities and the pool of species within the patch (α, β, and γ components). Our results call for the combined inclusion of FD and PD and their partitions into ecological analyses, being TD too crude to capture the comprehensive and contrasted response of plant diversity to landscape spatial pattern.

Different components of plant diversity suggest the protection of a large area for the conservation of a riparian ecosystem

AbstractRiparian ecosystems host an high level of biodiversity but anthropic activities have deeply altered their naturalness and functionality. The present study was carried out in a protected area along a recently regulated tract of the upper River Tiber (Tuscany, central Italy). The study’s aim is to explore different components of plant diversity (species richness, species composition, β-diversity) in the riparian habitats to determine the most relevant conservation issues. Twelve transects were allocated along the riparian zone and a stratified random sampling was performed on the habitat detected along the transects with 184 plots of 1 x 1 m. Species richness was analysed by the use of set of species-richness estimators. The different patterns of plant diversity were analysed by NMDS, Indicator Species Analysis and SDR with symplex analysis. Five habitat types were detected in the study area. Three well-represented habitats (riparian woodlands, shrublands and dry bars) showed a higher number of species; flooded banks and marshlands were much less common and were also less species rich. Species composition and indicator species analysis showed however that marshlands were the richest in taxa having high conservation value and in indicator species. The habitats differed greatly in species composition; β-diversity analysis showed a low number of shared species between the habitats. High values of species replacement and low similarity values were recorded between the plots within the habitats. The study shows some differences between quantitative and qualitative patterns of biodiversity in the study area. The results suggest that to maintain habitat species diversity, the best conservation strategy for the study area is to protect as large an area as possible

Variation of plant diversity components in different scales in relation to grazing and climatic conditions

Background: Understanding the role of livestock grazing on plant diversity can be improved by an accurate measurement of diversity at all hierarchical scales due to the changeability of diversity components in space.Aims: We evaluated the effects of grazing on plant species diversity at different scales of all common and rare species in two regions that have different climatic conditions (arid vs. semi-arid).Methods: In each region, we collected abundant data of plant species from a nested sampling design that consisted of local (80 plots) and regional (16 sites) scales. We partitioned total species diversity (γ) into within plots (αl), among plots (βl) and among sites (β2) using the additive partitioning.Results: Diversity among sites contributed the most to total diversity for all and rare plant species in both regions. In addition, α1 and β1 diversities in ungrazed areas were greater than those in grazed areas for all and common species in both climates.Conclusion: Abandonment of grazing after 10 years resulted in significant regeneration of common species at the local scale, with no change in rare species. We conclude that low grazing intensity is likely to be an important tool for conservation of plant diversity in which all scales should be considered.

¿La crisis de la biodiversidad es la crisis de la taxonomía?

El compromiso de integrar una lista florística que plasme el conocimiento de la diversidad vegetal a corto plazo, solamente será alcanzado con un cuerpo sólido de taxónomos especialistas, el cual, en lugar de fortalecerse, más bien parece estar en decaimiento. Los objetivos de este trabajo son discutir el papel que han jugado los taxónomos mexicanos en el conocimiento de la flora de México y cuál es el capital humano con que se cuenta en la actualidad, así como analizar el conocimiento que se tiene actualmente sobre la flora de México y su relevancia en las estrategias de conservación de la biodiversidad. Se proponen además, estudios novedosos que podrían complementar el conocimiento taxonómico para lograr definir las zonas más importantes de riqueza y endemicidad ( hotspots ) que complementen o actualicen nuestro Sistema Nacional de Áreas Naturales Protegidas. Los principales resultados señalan que la tasa de descripción de especies nuevas todavía muestra un sesgo importante en el número total de especies en la flora mexicana, ya que cada año se adiciona un número importante, ya sea como especies o como registros nuevos. Gran parte del descubrimiento de la diversidad faltante es obtenido con la revisión especializada del estudio de las colecciones científicas, aunque el número de taxónomos especialistas ha sufrido una disminución considerable. Se discuten algunas líneas emergentes de estudio que han ayudado a definir mejores estrategias de búsqueda y análisis de la biodiversidad, que seguramente facilitarán el trabajo de exploración e investigación de este componente desconocido de la diversidad vegetal del país. Se propone que, evitando la crisis que enfrenta actualmente la taxonomía, se minimizará de manera importante la crisis de la biodiversidad y de otras áreas de investigación afines. Desafortunadamente, el problema de la desaparición de los taxónomos en el mundo (y México no es la excepción), se debe en gran parte a los mecanismos de evaluación de la producción académica, a los ingresos obtenidos mediante recursos extraordinarios (subsidios a proyectos), y al factor de impacto de las revistas donde se publican los resultados. Se debe resolver esto para evitar considerarlos una especie en extinción.