Highest Number Of Plant Species Research Articles

Medicinal plants used in traditional medicine by Oromo people, Ghimbi District, Southwest Ethiopia.

BackgroundEthiopia is one of the six centres of biodiversity in the world with several topographies, climatic conditions and various ethnic cultures. Ethnobotanical study is a real and encourageable in rich biological resource areas for medicinal plant identification, documentation, ranking, conservation and sustainable usages. The purpose of this study was to identify the most effective medicinal plants for specific treatment through priority ranking and to assess the status of the transfer of Traditional Botanical Knowledge (TBK) based on age groups and educational levels.MethodologyEthnobotanical data were collected using field observation and semi-structured interview, A total of 30 key informants and 165 community members were interviewed and data on medicinal plant species and associated knowledge were recorded, quantified and verified using several preference ranking methods.ResultsThe study revealed a total of 49 medicinal plant species (belonging to 31 families and 46 genera) used to treat various human ailments, the majority of which 40 (81.6%) species were collected from wild while the rests from home garden. Herbs constituted the largest growth habit (18 species, 37%) followed by trees (16 species, 32%) and shrubs (15 species, 31%). Leaf `17 (35%) is the plant part widely used followed by root 13 (27%), leafy-stem 5 (10%), and seed 6 (12%). Oral administration was the dominant route (63%), followed by dermal route (22%) and nasal (11%). The highest number of plant species being used for infectious (48%) followed by two or more diseases and non-infectious disease. Of five and seven medicinal plants of preference ranking the highest ranks were given first for Croton macrostaychus used for malaria treatment and for Prunus africana as ‘’rare” for immediate collection and use in the traditional treatment. Significantly higher average number of medicinal plants (p < 0.05) were reported by informants of higher institution (14.3 ± 34) and adult age groups (11.6 ± 43).ConclusionThe Ghimbi people possess rich ethno-medicinal knowledge. This study can be used as a basis for developing management plans for conservation, sustainable use and drug development.

Plant-species diversity correlates with genetic variation of an oligophagous seed predator.

Several characteristics of habitats of herbivores and their food-plant communities, such as plant-species composition and plant quality, influence population genetics of both herbivores and their host plants. We investigated how different ecological and geographic factors affect genetic variation in and differentiation of 23 populations of the oligophagous seed predator Lygaeus equestris (Heteroptera) in southwestern Finland and in eastern Sweden. We tested whether genetic differentiation of the L. equestris populations was related to the similarity of vegetation, and whether there was more within-population genetic variation in habitats with a high number of plant species or in those with a large population of the primary food plant, Vincetoxicum hirundinaria. We also tested whether genetic differentiation of the populations was related to the geographic distance, and whether location of the populations on islands or on mainland, island size, or population size affected within-population genetic variation. Pairwise FST ranged from 0 to 0.1 indicating low to moderate genetic differentiation of populations. Differentiation increased with geographic distance between the populations, but was not related to the similarity of vegetation between the habitats. Genetic variation within the L. equestris populations did not increase with the population size of the primary food plant. However, the more diverse the plant community the higher was the level of genetic variation within the L. equestris population. Furthermore, the level of genetic variation did not vary significantly between island and mainland populations. The effect of the population size on within-population genetic variation was related to island size. Usually small populations are susceptible to loss of genetic variation, but small L. equestris populations on large islands seemed to maintain a relatively high level of within-population genetic variation. Our findings suggest that, in addition to geographic and species-specific ecological factors, the plant community affects population genetic structure of oligophagous herbivores.

Endozoochory by the guild of ungulates in Europe’s primeval forest

Seed dispersal by large herbivores helps to maintain the plant species diversity. Forest management and game management influence species composition and the structure of ungulate communities. This may disrupt ecological processes depending on services provided by animals. In European secondary forests, sets of plant species dispersed by guilds of herbivores overlap, and one species, red deer Cervus elaphus, may replace all other seed vectors in this process, although the proportion of dispersed forest species is very low. We hypothesize that some forest plant species with present-day low dispersal abilities were in the past dispersed by large ungulates which have since become extinct. In our opinion, in natural forests, where guilds of herbivores were complete, seed vectors dispersed different sets of plant species. We studied endozoochoric seed dispersal by European bison Bison bonasus, Eurasian moose Alces alces, red deer C. elaphus, roe deer Capreolus capreolus and wild boar Sus scrofa in the close-to-natural ecosystem of Białowieża Forest, Poland. Each of the studied ungulates dispersed a higher number of plant species than reported in any previous papers. This can be attributed to the high biodiversity of the study site, and to different methodological approach: year round collection of samples and 3-years long time frame for germination. Red deer and European bison were the most efficient seed dispersers – dispersing the richest sets of plant species, including ancient forest species, and the highest seed numbers. Moose and wild boar were the least efficient. Sets of plant species dispersed by each vector overlapped only partly. Our study stresses the importance of the completeness of the guild of seed dispersers for plant dispersal in forest habitats. Over half of overall plant species emerged from dung samples were dispersed by European bison – a species exterminated in most European forests centuries ago. The high number of plant species dispersed endozoochorically by the studied guild of animals, combined with the low similarity between sets of dispersed plant species, and the high share of species dispersed exclusively by only one of the vectors allows the conclusion that: (1) the dispersal efficiency of ungulates differs, but all species play a unique and important role in plant dispersal; (2) the species diversity of the guild of ungulates is very important for plant dispersal in temperate forests; and (3) seed dispersal in European forests has been seriously impoverished since their guilds of herbivores became deficient.

Invasive alien plants affect grassland ant communities, colony size and foraging behaviour

Ants are dominant members of many terrestrial ecosystems and are regarded as indicators of environmental changes. However, little is known about the effects of invasive alien plants on ant populations, particularly as regards the density, spatial distribution and size of ant colonies, as well as their foraging behaviour. We addressed these questions in a study of grassland ant communities on five grasslands invaded by alien goldenrods (Solidago sp.) and on five non-invaded grasslands without this plant. In each grassland, seven 100 m2 plots were selected and the ant colonies counted. Ant species richness and colony density was lower in the plots on the invaded grasslands. Moreover, both of these traits were higher in the plots near the grassland edge and with a higher number of plant species in the grasslands invaded by goldenrods but not in the non-invaded ones. On average, ant colony size was lower on the invaded grasslands than the non-invaded ones. Also, ant workers travelled for longer distances to collect food items in the invaded areas than they did in the non-invaded ones, even after the experimental removal of some ant colonies in order to exclude the effect of higher colony density in the latter. Our results indicate that invasive alien goldenrods have a profound negative effect on grassland ant communities which may lead to a cascade effect on the whole grassland ecosystem through modification of the interactions among species. The invasion diminishes a major index of the fitness of ants, which is a colony’s size, and probably leads to increased foraging effort of workers. This, in turn, may have important consequences for the division of labour and reproductive strategies within ant colonies.

Bird and Plant Diversity in Tropical Landscape Mosaics in East Usambaras, Tanzania

The role of land uses outside protected areas in conserving tropical biodiversity remains poorly understood and contested. This paper summarizes the results of plant and bird surveys conducted in three rural landscapes in the East Usambara Mountains of Tanzania, covering a gradient from Village forest reserves to tree-based and other agricultural land uses. The species richness and occurrence of conservationally important species across the land uses were analyzed. Twelve plots of 0.2 ha, stratified among land use types, were established to survey the large trees, with sub-plots of 1 × 40 m for tree saplings, shrubs and non-woody plants, and 5 × 40 m plots for small trees. Avian richness was measured in the same sites as the plants through mist netting and timed species counts. The village forests had higher plant species richness and more conservationally important plant species compared to other land uses. Agroforest and fallows supported a relatively high number of plant species, but the species composition was largely different to the adjacent village forests. Bird species of conservation importance were recorded across all land uses. Village forest reserves and some of the tree-based agricultural land uses were found to contribute to biodiversity conservation goals in tropical landscape mosaics. There is a need to better integrate them, and address their multiple functions, in village land-use planning and conservation efforts at the landscape level.

Plant diversity is linked to nutrient limitation of dominant species in a world biodiversity hotspot

AbstractQuestionsWhat is the role of nutrient limitation of dominant species in maintaining plant species diversity at small spatial scales, particularly in biodiversity hotspots?LocationSouthwest of Western Australia.MethodsThe extent of nutrient limitation was determined by measuring variation in the foliar nutrients of dominant plant species and total above‐ground biomass in relation to soil N and P across 16 plots. Plant species richness and evenness for the same plots were then regressed against foliar N:P and δ15N of the dominant species.ResultsFoliar N and P content as well as above‐ground biomass increased, while foliar N:P decreased with increasing soil N and P, suggesting that dominant species are limited by both N and P in southwest Australia. In contrast, foliar δ15N values only increased with decreasing soil P, indicating that δ15N enrichment reflects low P availability. Species richness increased at sites where foliar N:P was higher and δ15N more enriched, suggesting that a relatively greater number of rare plant species co‐exist where the growth of dominant vegetation is more nutrient‐limited.ConclusionsThe mechanisms that allow an exceptionally high number of plant species to co‐exist at small spatial scales in a southwest Australian biodiversity hotspot are linked to the extent to which the dominant plant species are limited in N and P. In addition, on nutrient‐impoverished soils, a foliar N:P ratio &gt;16 can reflect N as well as P limitation. While foliar δ15N also reflects availability of soil P, it is not necessarily a reliable indicator of nutrient limitation in southwest Australia, and perhaps in other environments where plants are highly adapted to low‐nutrient conditions.

Comparative study of the antimicrobial activity of native and exotic plants from the Caatinga and Atlantic Forest selected through an ethnobotanical survey

Context: The idea that many commonly used medicinal plants may lead to the discovery of new drugs has encouraged the study of local knowledge of these resources.Objective: An ethnobotanical survey of species traditionally used for the treatment of infectious diseases was undertaken in two areas of northeastern Brazil: one in the Caatinga (dry forest) and another in the Atlantic Forest (humid forest).Materials: Initially, diffusion tests using paper disks and subsequently, for extracts presenting significant results (inhibition halos above 15 mm), minimum inhibitory concentrations were determined. The activity was evaluated as a percentage for each species, comparing the diameters of the inhibition halos and the number of positive results against the seven microorganisms studied. Extracts were classified into three categories: strong activity—species with halos exceeding 16 mm, moderate activity—species with halos between 13 mm and 15 mm and low activity—species with halos below 12 mm. We selected 34 species, 20 from the Caatinga and 14 from the Atlantic Forest.Results: In the Caatinga, 50% of the 20 plant extracts studied had strong antimicrobial activity, 25% had moderate activity and 15% had low activity. In the Atlantic Forest, 28.5% of the 14 plant extracts studied showed strong activity, with 14.5% having moderate activity and 28.5% having low activity. The microorganism that was most susceptible to the extracts from the Caatinga, was Mycobacterium smegmatis; 85% of the species tested were able to inhibit its growth. The organism that was susceptible to the highest number of plant species (71%) from the Atlantic Forest was Staphylococcus aureus.Discussion and conclusions: Extracts from the Caatinga showed a trend of superior antimicrobial activity compared to the species from the Atlantic Forest, in terms of both inhibiting a greater variety of microorganisms and demonstrating higher activity against susceptible strains.

Structure prediction and binding sites analysis of curcin protein of Jatropha curcas using computational approaches

Ribosome inactivating proteins (RIPs) are defense proteins in a number of higher-plant species that are directly targeted toward herbivores. Jatropha curcas is one of the biodiesel plants having RIPs. The Jatropha seed meal, after extraction of oil, is rich in curcin, a highly toxic RIP similar to ricin, which makes it unsuitable for animal feed. Although the toxicity of curcin is well documented in the literature, the detailed toxic properties and the 3D structure of curcin has not been determined by X-ray crystallography, NMR spectroscopy or any in silico techniques to date. In this pursuit, the structure of curcin was modeled by a composite approach of 3D structure prediction using threading and ab initio modeling. Assessment of model quality was assessed by methods which include Ramachandran plot analysis and Qmean score estimation. Further, we applied the protein-ligand docking approach to identify the r-RNA binding residue of curcin. The present work provides the first structural insight into the binding mode of r-RNA adenine to the curcin protein and forms the basis for designing future inhibitors of curcin. Cloning of a future peptide inhibitor within J. curcas can produce non-toxic varieties of J. curcas, which would make the seed-cake suitable as animal feed without curcin detoxification.

Metal (Al, Mn, Pb and Zn) soils extractable reagents for available fraction assessment: Comparison using plants, and dry and moist soils from the Braçal abandoned lead mine area, Portugal

Eleven composite soil samples, developed either on schist materials or fine heterogeneous waste materials and coarse metallurgical slags, were collected in the Braçal (Portugal) abandoned lead mine. Plants growing in each sampling area were identified. A total of 49 plant samples of eight species –Acacia dealbata Link, Acacia melanoxilon R. Br., Cistus inflatus Pourr. ex Demoly, Erica arborea L., Eucalyptus globulus Labill., Pinus pinaster Aiton, Quercus robur L., and Ulex minor Roth – were collected. This study intends to evaluate the available fraction of aluminium, lead, manganese, and zinc in the soils using dry and moist samples in contact with five extractant solutions, degasified distilled water, and calcium chloride, calcium nitrate, ammonium acetate and DTPA aqueous solutions, and to compare together these results with the total elemental amounts in the aboveground part of the plant species. The available fraction is higher in moist than in the dry soil samples. The correlations between the soil available fraction of the elements and its concentration in the plants suggest that DTPA is not the best extractant for lead bioavailability evaluation. Variable results were observed for the bioavailable fraction of the elements evaluation suggesting that, in multielemental contaminated soils, calcium chloride seems to be a good extractant medium, once it correlates with the higher number of plant species.

Seasonal changes in species composition, resource use and reproductive patterns within a guild of nectar-feeding bats in a west Mexican dry forest

Abstract:Seasonal changes in resource use and reproduction within a guild of nectar-feeding phyllostomid bats were studied between 2002 and 2004 in a west Mexican dry forest using mist-net captures and diet analysis over 82 nights during both dry and wet seasons. The local guild consisted of three resident species,Glossophaga soricina,Leptonycteris yerbabuenae,Musonycteris harrisoni, and ofAnoura geoffroyi, which was mostly captured during the wet season. The proportion ofL. yerbabuenaefemales more than doubled during the dry season. Diet was accessed by identifying the pollen collected from the bats' bodies and by analysis of faecal material. Bats used at least 28 different nectar plants over the year. In the dry season, 91.9% of all bats carried pollen while only 54.6% did so in the wet season. Bat individuals used the highest number of plant species during the dry season, mainly the cactusPachycereus pecten-aboriginum, various Bombacaceae and the CapparaceaeCleome spinosa. Niche overlap was higher in the dry season than in the wet season.Musonycteris harrisoniandLeptonycteris yerbabuenaeshowed the largest overlap and both relied heavily on cactus flowers, whereasG. soricinasupplemented its nectar diet with fruits. While reproductive females of most species were found only in the flower-rich dry season,G. soricinashowed a bimodal reproductive pattern.

Effects of Medicago sativa, Taraxacum officinale and Bromus sterilis on the density and diversity of Collembola in grassy arable fallows of different ages

Abstract The density and diversity of Collembola of nine grassy arable fallows of different ages were investigated in a factorial design with the factors ‘plant species’ (legume: Medicago sativa, herb: Taraxacum officinale, grass: Bromus sterilis) and ‘age class’ (2–3, 6–8 and 12–15 years) including the random effect ‘site’ (1–9). In May 2008, four plots were selected randomly at each fallow. Within each plot five M. sativa, T. officinale and B. sterilis plants were extracted with their associated soil using steel cylinders. The material from each plant species was used for extraction of Collembola and for determination of environmental parameters. Thus, the new aspect of the present study compared to other field studies investigating the relationships between plant and Collembolan communities is the focus on the “micro-scale”, investigating the Collembolan communities of the soil associated with single plants. We found that species richness and density of total and euedaphic Collembola were significantly higher in B. sterilis than in T. officinale samples with the M. sativa samples being intermediate. Fine-root feeding euedaphic Collembola particularly benefited from the higher amount of fine roots in B. sterilis samples. We also discovered that the age of the fallows had no significant influence on the number of Collembolan species and the density of the Collembolan groups. Notably, however, species of the epedaphic genera Lepidocyrtus and Sminthurinus were associated with the 12–15 year-old fallows and presumably benefited from the high number of plant species in the old fallows. Finally, canonical correspondence analysis (CCA) indicated that the soil organic matter content and the microbial biomass, both potential food sources for many Collembolan species, were important structuring forces for the Collembolan communities.

Interrill erosion at disturbed alpine sites: Effects of plant functional diversity and vegetation cover

It has been hypothesized that a diverse vegetation cover with a high number of plant species and plant functional groups may be more effective at governing soil erosion processes than a vegetation cover with few species and fewer different plant functional groups. We investigated the influence of plant cover and diversity on interrill erosion on a disturbed alpine site. Rainfall simulations were conducted on micro-scale plots (25 × 25 cm) with different degrees of vegetation cover and plant functional group diversity. We selected plots with 10%, 30% and 60% of vegetation cover containing different plant functional groups: (i) grasses, (ii) forbs, (iii) cryptogams (moss and/or lichens), and all possible combinations of these three groups. On each plot a rain intensity of 375 ml min −1 (30 mm) was applied for 5 min. The degree of vegetation cover had the largest effect on interrill erosion. At 60% vegetation cover, the sediment yield was reduced by 83% in comparison to the un-vegetated ground. In the plots with 60% vegetation cover, an increase in functional group diversity decreased the sediment yield significantly. Sediment yield was three times lower in the presence of three plant functional groups than in systems with one plant functional group. Combinations of plant functional groups including grasses reduced the sediment yield more than other combinations. The findings of this study support the view that beside the re-establishment of a closed vegetation cover, a high plant functional diversity can be a relevant factor to further reduce interrill erosion at disturbed sites in alpine ecosystems.

Trophic relations between vespid wasps (Hymenoptera, Vespidae) and flowering plants in the Crimea

The results of the study of trophic relations between nectar-feeding adult wasps and flowering plants in the Crimea are given. In 2002–2009, a total of 55 wasp species were observed on flowers of 74 plant species belonging to 25 families. The highest number of plant species was visited by Polistes dominulus (36), Ancistrocerus nigricornis (18), Polistes nimphus (16), P. gallicus (13) and Dolichovespula sylvestris (13); these plants belonged to the families Apiaceae (15), Lamiaceae (10), Scrophulariaceae (8), Rosaceae (8) and Asteraceae (7). Plants of the families Scrophulariaceae, Apiaceae, Lamiaceae, Rosaceae, and Fabaceae were visited by 25, 24, 22, 11, and 11 wasp species, respectively. Other plant families were visited by 10 or less wasp species. The highest number of wasp species were observed on flowers of Scrophularia umbrosa (22), Mentha longifolia (12), Bupleurum fruticosum (10), Laserpitium hispidum (10), Koelreuteria paniculata (10), Sambucus ebulus (10), Dorycnium herbaceum (9), Foeniculum vulgare (8), Limonium platyphyllum (7), Torilis arvensis (7), Marrubium peregrinum (7), Butomus umbellatus (7), Eryngium campestre (6), Cynanchum acutum (6) and Scrophularia scopolii (6). One to five wasp species were recorded on flowers of plants belonging to other families. Two wasp species (Polistes nimphus and Vespula germanica) were registered as visitors of the nectarless flowers of the orchid Steveniella satyrioides.

How many plant species are cultivated?

Cultivation reflects an intense relationship between human and plants. Therefore, the number of cultivated plant species is of general interest. The number of cultivated crop species amounts to about 7,000 (“Mansfeld’s approach”). Amenity horticulture is a quickly developing area comprising ornamentals and other plants connected with gardening and landscaping. 28,000 plant species have been estimated to belong to this group. Cultivated forest plants are partly included in the first group and mostly in the second group. Thus, we propose that the total number of cultivated plants amounts to 35,000 species, i.e. about 14% of the number of higher plant species of the world.

Plant diversity in crop fields and woody hedgerows of organic and conventional farms in contrasting landscapes

The purpose of this study was to determine the effects of contrasting agricultural practices in organic and conventional farming (local factors), and to evaluate the influence of surrounding landscape features (regional factors) on plant assemblages, taking into account habitat structure. Plants were inventoried in crop fields and woody hedgerows (boundary and centre) of 16 conventional and 14 organic sites. Habitat structure, agricultural practices and landscape characteristics were quantified for each habitat. Hedgerow boundaries contained a higher number of plant species than adjacent habitats although many of them were exotics. However, exotics comprised a decreasing proportion of species richness from field to hedgerow centre. Many of the exotic species were shared between crop fields and adjacent boundaries. There was a clear difference in species richness and composition between the organic and conventional study sites. Fields and woody hedgerows situated in organic sites consistently harboured more native and exotic plant species than those in conventional systems. Numerous species were only found in organic hedgerows and included several long-lived herbaceous forest species. At the larger scale level, old-fields (areas with sparse shrubs and trees re-colonizing cleared land) were the only habitats that significantly influenced the species composition of hedgerows, particularly exotic species. Conversely, farm type was a significant predictor of native species richness.

Legacies of the past in the present‐day forest biodiversity: a review of past land‐use effects on forest plant species composition and diversity

AbstractParticularly in the temperate climate zone many forests have, at some moment in their history, been used as agriculture land. Forest cover is therefore often not as stable as it might look. How forest plant communities recovered after agriculture was abandoned allows us to explore some universal questions on how dispersal and environment limit plant species abundance and distribution. All studies looking at the effects of historical land use rely on adequate land use reconstruction. A variety of tools from maps, archival studies, and interviews to field evidence and soil analyses contribute to that. They allow us to distinguish ancient from recent forests and many studies found pronounced differences in forest plant species composition between them. A considerable percentage of our forest flora is associated with ancient forests. These ancient forest plant species (AFS) all have a low colonization capacity, suggesting that dispersal in space (distance related) and time (seed bank related) limit their distribution and abundance. However recent forests generally are suitable for the recruitment of AFS. There is clear evidence that dispersal limitation is more important than recruitment limitation in the distribution of AFS. Dispersal in time, through persistent seed banks, does not play a significant role. Ancient forests are not necessary more species‐rich than recent forest, but if diversity is limited to typical forest plant species then ancient forests do have the highest number of plant species, making them highly important for nature conservation. The use of molecular markers, integrated approaches and modelling are all part of the way forward in this field of historical ecology.

Effects of vegetation type on soil microbial community structure and catabolic diversity assessed by polyphasic methods in North China

Abstract Soil microbes play a major role in ecological processes and are closely associated with the aboveground plant community. In order to understand the effects of vegetation type on the characteristics of soil microbial communities, the soil microbial communities were assessed by plate counts, phospholipid fatty acid (PLFA) and Biolog microplate techniques in five plant communities, i.e., soybean field (SF), artificial turf (AT), artificial shrub (AS), natural shrub (NS), and maize field (MF) in Jinan, Shandong Province, North China. The results showed that plant diversity had little discernible effect on microbial biomass but a positive impact on the evenness of utilized substrates in Biolog microplate. Legumes could significantly enhance the number of cultural microorganisms, microbial biomass, and community catabolic diversity. Except for SF dominated by legumes, the biomass of fungi and the catabolic diversity of microbial community were higher in less disturbed soil beneath NS than in frequently disturbed soils beneath the other vegetation types. These results confirmed that high number of plant species, legumes, and natural vegetation types tend to support soil microbial communities with higher function. The present study also found a significant correlation between the number of cultured bacteria and catabolic diversity of the bacterial community. Different research methods led to varied results in this study. The combination of several approaches is recommended for accurately describing the characteristics of microbial communities in many respects.

Identification and authentication of herbal substances

Due to the increasingly high number of plant species used as starting materials for herbal medicinal products and the risk of admixtures and adulterations with related or similar species identification along the production and processing chain is a crucial problem. Identity and purity is usually tested by macro- and microscopic as well as chromatographic methods, preferably TLC. The most recent developments in HPTLC and the characterisation of herbal materials by specific chromatographic fingerprints will be discussed. In addition, DNA analysis has become a novel technique for identification and authentication of raw materials and monitoring throughout the production chain. Depending on their practicability the different DNA based methods may supplement or substitute other identity tests.

Potencial de infectividade de fungos micorrízicos arbusculares em áreas nativas e impactadas por mineração gesseira no semi-árido brasileiro

Foi avaliado o efeito da mineração gesseira sobre os fungos micorrízicos arbusculares (FMA). Amostras de solo (10/área) foram coletadas em quatro áreas de uma mineradora: caatinga nativa (CN), arredores da mina (AM), rejeito (R) e interface entre o rejeito e caatinga degradada (IN), nos períodos chuvoso (dezembro/2003) e seco (setembro/2004). Foram registradas 42 espécies de fanerógamas: 25 na CN, 14 nos AM, 10 na IN e cinco na R. A CN apresentou maior número de espécies vegetais, esporos e propágulos infectivos de FMA. Número de esporos e colonização radicular diferiram entre os períodos. Maior esporulação ocorreu no período chuvoso, o número mais provável (NMP) de propágulos e colonização foram maiores no seco. Houve correlação positiva entre NMP e esporos nos dois períodos. No período chuvoso, o NMP foi negativamente correlacionado com colonização. Esta foi maior nas áreas AM e R. A atividade mineradora diminuiu a diversidade vegetal, o NMP de propágulos e a quantidade de esporos em relação à caatinga nativa.

A LONG-TERM FIELD STUDY ON BIODIVERSITY × ELEVATED CO2INTERACTIONS IN GRASSLAND

Interactive effects of increases in atmospheric CO2 and reductions in plant species diversity were investigated in planted calcareous grassland communities in northwestern Switzerland. The experimental communities were composed of 5, 12, and 31 species assembled from the native species pool. The study aimed at testing whether the CO2 responses of ecosystems change when specific sets of species are lost from plant communities. Species were selected so that the proportion of grasses, legumes, and non-legume forb individuals remained constant across levels of diversity. The most diverse plant community had approximately the same diversity as the surrounding grassland, and species occurring in less diverse communities were subsets of the species in the more diverse communities. The factorial atmospheric-CO2 treatment was applied using 50-cm-tall, open-bottom, open-top wind screens. Plant community-level responses and the responses of the individual species were assessed over a period of five years. A significant positive correlation between plant community diversity and biomass was detected, but this effect was not present on all dates. Significant effects of elevated CO2 on community biomass were only found in the first years of treatment. CO2 effects were largest in the communities with the highest number of plant species and were primarily due to the presence of responsive species not present in the less diverse communities. The time dependency of community responses to elevated CO2 and species diversity was related to shifts in community structure of the experimental plots. Community responses at the beginning of the experiment were dominated by the response of species with a less competitive/stress-tolerant life history. These species were successively lost from experimental plots as the experiment proceeded, and the observed community-level effects became smaller. Changes in species composition over the experimental duration were affected by elevated CO2 in the way that species loss was reduced (i.e., coexistence of species performing well at the beginning and at the end of the five-year period increased) and the way that community evenness was increased (i.e., dominance was reduced). Based on these results our main conclusions are that (1) community-level responses to CO2 enrichment depend on the species present; (2) the positive correlation between productivity and species numbers was caused by different species at the beginning and at the end of the experiment; (3) therefore, a large, redundant species pool is important in assuring high productivity under altering environmental conditions; (4) elevated CO2 has the potential to substantially alter the structure of grassland communities, even if community productivity does not increase; and (5) a short-term effect of elevated CO2 may be misleading when attempting to predict longer-term effects.