Levels Of Plant Diversity Research Articles

A second look at fynbos biodiversity

book reviews ISSN 1948-6596 A second look at fynbos biodiversity Fynbos: Ecology, Evolution and Conservation of a Megadiverse Region. Nicky Allsopp, Jonathan F. Colville & G. Anthony Verboom (Editors), 2014, Oxford University Press. 395 pp. £65.00 (hardback) ISBN 978-0-19-967958-4; http://global.oup.com/ The exceptional levels of plant diversity and ende- mism of the Cape Floristic Region (CFR) in the southwestern corner of Africa continue to capti- vate scientists and naturalists from all over the world. Fynbos is the dominant vegetation type of the CFR—or the second-dominant if the CFR and the adjacent succulent karoo region are consid- ered together under the Greater Cape Floristic Region (GCFR). Either way, fynbos is renowned as the epitome of plant biodiversity in this region. This by itself explains the title of this book, as the editors point out in their preface, and although the book deals with five major vegetation types within the GCFR, fynbos receives the main focus throughout. The title also highlights the connection of this volume to Cowling’s (1992) influential book The Ecology of Fynbos: Nutrients, Fire and Diversi- ty, published more than 20 years ago and focused on ecological, evolutionary and biodiversity patterns of the CFR. The present book not only synthesises the knowledge gained on the topic since then, but it puts more emphasis on process- es than on patterns. By taking advantage of the rapid advances in DNA sequencing and molecular phylogenetic analyses in the last two decades, it aims at understanding how ecological and evolu- tionary processes affect the outstanding biodiver- sity of the CFR (or the GCFR) and how this can be preserved. It would be difficult, however, and probably unwise, to ignore the earlier book (Cowling 1992) in the review of this new volume. The new book describes the five major veg- etation types of the GCFR (fynbos, renosterveld, succulent karoo, thicket and forest) and the main environmental factors that determine their geo- graphical distribution: soils, topography, climate and fire. Although it is a very detailed description, complemented with a multivariate analysis to ex- plore floristic similarities between vegetation types, little is added to what was already known from the first book. However, thanks to more re- cent phylogenetic studies, the more recent book provides compelling new insights into the evolu- tionary history of the GCFR flora and vegetation. For instance, long-distance dispersal rather than vicariance can now explain the Australasian con- nections of the fynbos flora. Also, unlike the an- cient thicket and forest floras, a significant phylo- genetic clustering has been detected in fynbos, renosterveld and succulent karoo floras, sug- gesting either a recent origin or greater isolation through their evolutionary histories. While recent, rapid speciation seems to account for the high species richness of succulent karoo and renoster- veld vegetation, fynbos biodiversity is explained by less rapid speciation coupled with low extinc- tion due to long-term climatic and topographic stability. The extremely high species diversity of these vegetation types, particularly fynbos and succulent karoo, contrasts with their low levels of functional and structural diversity. Unquestionably the main novelty of this book, compared to the first fynbos book, is the incorporation of a rich body of knowledge on the evolutionary processes underlying the high biodi- versity of the GCFR flora through both phyloge- netic and population-level approaches. Several causes of plant speciation have been suggested, from topographic and edaphic (micro)habitat spe- cialisation to pollinator-driven diversification. Add to this the key role of fire in boosting plant diversi- fication in fynbos, which surprisingly was hardly mentioned in Cowling’s (1992) book. Fire in that book was only used to explain the transition from fynbos to forest or thicket in fire refugia, to ac- count for key reproductive traits in fynbos plants and, at the end of the book, in a chapter on CFR ecosystem management. Another new aspect of this new book, alt- hough less resolved, is the incorporation of faunal data to explore consistencies of both flora and frontiers of biogeography 7.2, 2015 — © 2015 the authors; journal compilation © 2015 The International Biogeography Society

Interactive effects of large herbivores and plant diversity on insect abundance in a meadow steppe in China

The structure and dynamics of insect community in grasslands can be influenced by grazing management via altered characteristics of plant community. However, attempts to better understand the complex relationships among plants, insects, and large herbivores is still hampered largely by the interactive effects of plants, insects, and large grazers on each other. In this study, we test the hypothesis that the effect of large herbivores on insect abundance is grazer species-specific and pre-grazing plant diversity-dependent using an experiment with manipulating four grazing treatments (i.e., control, cattle, goats, and sheep) at low, intermediate, and high plant diversity levels in a meadow steppe at northeast in China. We show that grazing significantly increased the abundance of the entire insect community. The abundance of each insect order responded differently to grazing treatments, with higher abundance of Orthoptera and Homoptera under sheep grazing, enhanced abundance of Coleoptera and Diptera under cattle grazing, and reduced Hemiptera abundance, but greater abundance of Lepidoptera under goats grazing. Thus different treatments profoundly changed insect taxonomic composition. The six most dominant species (Euchorthippus unicolor, Aelia nasuta, Trigonotylus ruficornis, Curculionidae sp., Coccinula quatuordecimpustulata, and Cicadellidae sp.) responded differently to grazing by large herbivores, with either increased or decreased its abundance. The effects of grazing on insect abundance were driven by their differential responsive mechanisms for vegetation. More importantly, the effects of grazing on insect abundance at both order- and species-levels potentially depended on plant diversity levels of pre-grazing. Our results suggest that different herbivore species should be used in the background of different plant communities for better conservation of insect community in managed grassland.

Impacts of grazing by different large herbivores in grassland depend on plant species diversity

Summary It is well documented that large herbivores have pronounced effects on plant communities in grassland ecosystems, and the extent and course of their effects can largely depend on both plant and herbivore characteristics. Previous studies highlighted the importance of plant productivity in predicting the impact of herbivores on grasslands. Yet, there has been little consideration of how different herbivores affect plant communities that, in turn, differ in plant diversity. In a 2‐year grazing experiment, we tested the effects of large herbivores (cattle or sheep, or both together) on plant communities under high and low plant diversity levels in eastern Eurasian steppe. We found that, for high plant diversity grassland, mixed grazing by cattle and sheep significantly increases plant diversity, but we found no effect of grazing by cattle or sheep alone. Grazing by cattle or sheep alone or mixed grazing by cattle and sheep did not significantly affect plant biomass in the high diversity grassland. However, for low plant diversity grassland, grazing by cattle alone and mixed grazing by cattle and sheep significantly increased plant diversity, but significantly decreased plant biomass. There was no significant impact on both plant diversity and biomass from sheep grazing. Synthesis and applications. We conclude that the effects of grazing in grassland strongly depend on herbivore assemblages and pre‐grazing plant diversity. Herbivore grazing might contribute more to the maintenance of grassland structure and ecosystem functioning under high plant diversity compared with low plant diversity. Furthermore, our data suggest that multiple‐species mixed grazing regimes in grassland systems with high plant diversity could represent the optimal protocol for grazing management. This study emphasizes the importance of maintaining both plant and herbivore diversity to optimize ecosystem functioning.

Habitat differentiation of obligate ultramafic Nepenthes endemic to Mount Kinabalu and Mount Tambuyukon (Sabah, Malaysia)

Localized ultramafic outcrops in Kinabalu Park (encompassing Mount Kinabalu and Mount Tambuyukon) in Sabah (Malaysia) are known for high levels of plant diversity and endemism, which have been stimulated by extreme soil chemistry and biogeographic factors, such as isolation. Characteristic of these outcrops are edaphic endemics of insectivorous pitcher plants from the Nepenthaceae-family including Nepenthes burbidgeae, N. edwardsiana, N. macrovulgaris, N. rajah and N. villosa, all of which (except N. macrovulgaris) are confined solely to the protected area of Kinabalu Park. Although the various aspects of plant taxonomy and nutrition of this genus have been extensively studied, the habitat of these rare species has to date not been studied in detail. It was hypothesized that while the Nepenthes of Mount Kinabalu and Mount Tambuyukon are excluders of excess trace elements, soil chemistry is nevertheless a major driver for creating the specific habitats in which ultramafic edaphic endemic Nepenthes occur, and that this is reflected in vegetation physiognomy and co-occurring species composition as well as in the foliar chemistry of Nepenthes. The results show that the characteristics of the physical environment and soil chemistry ‘induces’ a vegetation physiognomy that varies among sites and produces a series of different niches that are colonised by different Nepenthes-species. Although other plant species associated with these niches do not directly influence the distributions of the Nepenthes-species, some are characteristic. The unusual ultramafic soil chemistry is not reflected in the foliar chemistry of Nepenthes and they appear to be ‘Excluders’ of potentially toxic soil trace element concentrations. The populations of Nepenthes burbidgeae, N. edwardsiana, N, rajah, N. villosa are small (in particular, N. burbidgeae) and these species are thus likely to be vulnerable to the potential effects of climate change-induced drought and fire.

Phylogenetic analysis in Myrcia section Aulomyrcia and inferences on plant diversity in the Atlantic rainforest.

Myrcia section Aulomyrcia includes ∼120 species that are endemic to the Neotropics and disjunctly distributed in the moist Amazon and Atlantic coastal forests of Brazil. This paper presents the first comprehensive phylogenetic study of this group and this phylogeny is used as a basis to evaluate recent classification systems and to test alternative hypotheses associated with the history of this clade. Fifty-three taxa were sampled out of the 120 species currently recognized, plus 40 outgroup taxa, for one nuclear marker (ribosomal internal transcribed spacer) and four plastid markers (psbA-trnH, trnL-trnF, trnQ-rpS16 and ndhF). The relationships were reconstructed based on Bayesian and maximum likelihood analyses. Additionally, a likelihood approach, 'geographic state speciation and extinction', was used to estimate region-dependent rates of speciation, extinction and dispersal, comparing historically climatic stable areas (refugia) and unstable areas. Maximum likelihood and Bayesian inferences indicate that Myrcia and Marlierea are polyphyletic, and the internal groupings recovered are characterized by combinations of morphological characters. Phylogenetic relationships support a link between Amazonian and north-eastern species and between north-eastern and south-eastern species. Lower extinction rates within glacial refugia suggest that these areas were important in maintaining diversity in the Atlantic forest biodiversity hotspot. This study provides a robust phylogenetic framework to address important ecological questions for Myrcia s.l. within an evolutionary context, and supports the need to unite taxonomically the two traditional genera Myrcia and Marlierea in an expanded Myrcia s.l. Furthermore, this study offers valuable insights into the diversification of plant species in the highly impacted Atlantic forest of South America; evidence is presented that the lowest extinction rates are found inside refugia and that range expansion from unstable areas contributes to the highest levels of plant diversity in the Bahian refugium.

Isolated cork oak trees affect soil properties and biodiversity in a Mediterranean wooded grassland

Mediterranean wooded grasslands are multipurpose systems that support high plant and animal diversity levels and are habitats of European importance (i.e., 6310 – Dehesas with evergreen Quercus spp.). Moreover, these systems offer a number of agro-ecosystem services such as forage production, soil carbon sequestration, nutrient recycling and soil protection. The scattered trees enhance the ecological complexity of grassland influencing the soil properties, the herbaceous layer diversity and composition and the soil communities. Understanding how isolated trees influence the other components of the system is essential to comprehend their role supporting high levels of above and below ground biodiversity and ecosystem services.In the present study, we present a hypothetical framework of the effects of isolated trees on soil properties, plant and soil fauna assemblages, the latter here represented by the class Collembola. The floor litter and the associated input of organic matter to the soil was a key factor linking the components of the tree-soil-biodiversity system in a Mediterranean cork oak wooded grassland.Topsoil C increased by +50% under the tree canopy in comparison with the areas beyond the tree canopy. Plant diversity was lower under tree canopy, but contributed to enhance the total species richness of the grassland. Collembolan diversity was higher under the peculiar conditions beneath the tree canopy. Relationships between plant and collembolan species emerged.The findings of this study suggest that isolated trees have direct and indirect effects on soil properties, plant and collembolan assemblages, hence they can influence the ecological processes of wooded grasslands, with implications for food webs, nutrient cycling and productivity of the agro-ecosystem.

Plant diversity effects on soil microbial functions and enzymes are stronger than warming in a grassland experiment.

Anthropogenic changes in biodiversity and atmospheric temperature significantly influence ecosystem processes. However, little is known about potential interactive effects of plant diversity and warming on essential ecosystem properties, such as soil microbial functions and element cycling. We studied the effects of orthogonal manipulations of plant diversity (one, four, and 16 species) and warming (ambient, +1.5 degrees C, and +3 degrees C) on soil microbial biomass, respiration, growth after nutrient additions, and activities of extracellular enzymes in 2011 and 2012 in the BAC (biodiversity and climate) perennial grassland experiment site at Cedar Creek, Minnesota, USA. Focal enzymes are involved in essential biogeochemical processes of the carbon, nitrogen, and phosphorus cycles. Soil microbial biomass and some enzyme activities involved in the C and N cycle increased significantly with increasing plant diversity in both years. In addition, 16-species mixtures buffered warming induced reductions in topsoil water content. We found no interactive effects of plant diversity and warming on soil microbial biomass and growth rates. However, the activity of several enzymes (1,4-beta-glucosidase, 1,4-beta-N-acetylglucosaminidase, phosphatase, peroxidase) depended on interactions between plant diversity and warming with elevated activities of enzymes involved in the C, N, and P cycles at both high plant diversity and high warming levels. Increasing plant diversity consistently decreased microbial biomass-specific enzyme activities and altered soil microbial growth responses to nutrient additions, indicating that plant diversity changed nutrient limitations and/or microbial community composition. In contrast to our expectations, higher plant diversity only buffered temperature effects on soil water content, but not on microbial functions. Temperature effects on some soil enzymes were greatest at high plant diversity. In total, our results suggest that the fundamental temperature ranges of soil microbial communities may be sufficiently broad to buffer their functioning against changes in temperature and that plant diversity may be a dominant control of soil microbial processes in a changing world.

Impacts of burrows and mounds formed by plateau rodents on plant species diversity on the Qinghai-Tibetan Plateau

The relationships among environmental factors, rodent activity disturbance and plant-community diversity were studied across four sites in a prefecture of the ‘Three-River-Source’ region of the Qinghai-Tibetan Plateau. It was found that burrow number and mound area had little impact on plant diversity indices, which were mainly affected by altitude, soil total P and pH. Altitude and mound area, especially mound area, can strongly affect the aboveground biomass and the vegetation cover of plants was mainly influenced by mound area. There was some evidence that moderate levels of disturbance by rodents could lead to the highest levels of plant diversity. These findings indicated that moderate levels of disturbance by rodents may be beneficial to grassland productivity and plant diversity. Understanding these impacts is vital for better rangeland management practices so that rodents should be controlled within a suitable range rather than being exterminated.

Effects of plant litter diversity, species, origin and traits on larval toad performance

Decreased plant diversity is expected to reduce ecosystem function. Although many studies have examined effects of plant species on trophic interactions, information regarding effects of native or non‐native plant diversity on performance of individuals of higher trophic levels is limited. We reared larval American toadAnaxyrus americanustadpoles in outdoor mesocosms containing litter of 1, 3, 6 or 12 plant species drawn randomly from a pool of 24 (15 native, 9 nonnative) species. Tadpole performance varied significantly among litter types in single litter treatments and pH and litter C:N were significant predictors of tadpole performance. Metamorphs were larger in mixtures than expected based on performance in single species treatments, suggesting a non‐additive effect of diversity. Litter diversity did not affect probability of survival or probability of metamorphosis. Plant origin (native or non‐native) had no significant effect on amphibian performance. Our study suggests some benefits to tadpole development at low levels of plant diversity, but questions assumed benefits of increased plant diversity and assumed detrimental effects of nonnative plant species for a common larval amphibian. Presence of specific plant species with strong negative effects on tadpole performance may outweigh diversity benefits in brown food webs.

Paleocene wind-dispersed fruits and seeds from Colombia and their implications for early Neotropical rainforests

Abstract Extant Neotropical rainforests are well known for their remarkable diversity of fruit and seed types. Biotic agents disperse most of these disseminules, whereas wind dispersal is less common. Although wind-dispersed fruits and seeds are greatly overshadowed in closed rainforests, many important families in the Neotropics (e.g., Bignoniaceae, Fabaceae, Malvaceae, Orchidaceae, Sapindaceae) show numerous morphological adaptations for anemochory (i.e. wings, accessory hairs). Most of these living groups have high to moderate levels of plant diversity in the upper levels of the canopy. Little is known about the fossil record of wind-dispersed fruits and seeds in the Neotropics. Six new species of disseminules with varied adaptations for wind dispersal are documented here. These fossils, representing extinct genera of Ulmaceae, Malvaceae, and some uncertain families, indicate that wind-dispersed fruit and seed syndromes were already common in the Neotropics by the Paleocene, coinciding with the early development of multistratal rainforests. Although the major families known to include most of the wind-dispersed disseminules in extant rainforests are still missing from the Paleogene fossil record of South and Central America, the new fossils imply that anemochory was a relatively important product and/or mechanism of plant evolution and diversification in early Neotropical rainforests.

Habitat requirements and dispersal ability of the Spanish Fritillary (Euphydryas desfontainii) in southern Portugal: evidence-based conservation suggestions for an endangered taxon

A high level of plant and insect diversity, and more specifically high butterfly diversity characterizes the Mediterranean Basin. However, alarming negative trends have been reported for butterfly populations in that region emphasizing the urgent need to better understand the drivers of their population declines. Habitat specialists of grasslands are strongly affected, mainly by land use change and climate change. Thorough assessments of habitat requirements and dispersal abilities are crucial to establish appropriate conservation measures to counter these threats. Here, we investigate the ecological requirements and dispersal ability of Euphydryas desfontainii, one of Portugal's rarest butterflies, to develop targeted conservation strategies. The assessment of habitat requirements showed differences between occupied and unoccupied patches in terms of host plant abundance and area. Mark-release-recapture data were used to model demographic parameters: survival rates decreased linearly over the flight period and recruitment followed a parabolic curve with separate peaks for males and females. The movement data were fitted to an inverse power function and used to predict the probability of long-distance dispersal. The obtained probabilities were compared to related checkerspot butterflies and interpreted regarding the structural connectivity of the investigated habitat network. We suggest focusing on the preservation of remaining habitat patches, whilst monitoring and safeguarding that their vegetation structure does provide sufficiently diversified microclimates in order to best conserve E. desfontainii populations. © 2014 Springer International Publishing Switzerland.

Effects of transformation processes on plant species richness and diversity in homegardens of the Nuba Mountains, Sudan

Traditional homegardens (HGs) are considered to harbor high levels of plant diversity and have been therefore characterized as sustainable agro-ecosystems suitable for on-farm (incl. circa situm) conservation of plant genetic resources. While the functional structure of traditional HGs is poorly understood specifically for semi-arid and arid regions, their plant species richness and diversity is increasingly threatened by recent and fast evolving agricultural transformation processes. This has been particularly claimed for traditional jubraka HG systems of Sudan. Therefore, sixty-one HGs in four villages of the Nuba Mountains, South-Kordofan Province, Sudan, were randomly selected, geographically recorded and plant richness and abundance determined and plant diversity parameters calculated. In addition, socio-economic household data were assessed by interviews and soil samples taken to allow a comprehensive analysis of putative factors affecting HG plant diversity across different villages, levels of commercialization and plant species composition based clusters. A total of 110 species from 35 plant families were grown in the HGs along with 71 ornamentals. Perennial species accounted for 57 % including 12 indigenous fruit tree (IFT) species and six exotic fruit tree species. Mean species richness of useful plant species (excluding ornamentals) per HG was 23 (range 6–46). On average, 41 % of the 23 species per HG were of exotic origin, however, with a large range (21–83 %) among locations. Mean diversity and evenness indices were 1.46 (range 0.49–2.42) and 0.48 (0.15–0.87), respectively. The level of commercialization of HGs only marginally affected species diversity measures although the species richness was significantly higher for commercial than subsistence HGs. Species richness was higher on lower (6.6–7.2) pH soils. IFT richness was highly variable, but non-significantly different across the four locations. Plant species richness and diversity was high in comparison with other HG systems in semi-arid regions. Cluster analysis was found to be a valuable tool to classify HGs and to extract homogeneous HG types with low, intermediate and high richness and diversity. In addition, the share of exotic and ornamental species in HGs indicated a trend towards the loss of traditional farming practices, particularly in areas with good market access. The data did not indicate the hypothesized loss of inter-specific diversity due to commercialization and species richness was numerically even higher for market-oriented HGs compared to subsistence ones.

Positive interactions between herbivores and plant diversity shape forest regeneration

The effects of herbivores and diversity on plant communities have been studied separately but rarely in combination. We conducted two concurrent experiments over 3 years to examine how tree seedling diversity, density and herbivory affected forest regeneration. One experiment factorially manipulated plant diversity (one versus 15 species) and the presence/absence of deer (Odocoileus virginianus). We found that mixtures outperformed monocultures only in the presence of deer. Selective browsing on competitive dominants and associational protection from less palatable species appear responsible for this herbivore-driven diversity effect. The other experiment manipulated monospecific plant density and found little evidence for negative density dependence. Combined, these experiments suggest that the higher performance in mixture was owing to the acquisition of positive interspecific interactions rather than the loss of negative intraspecific interactions. Overall, we emphasize that realistic predictions about the consequences of changing biodiversity will require a deeper understanding of the interaction between plant diversity and higher trophic levels. If we had manipulated only plant diversity, we would have missed an important positive interaction across trophic levels: diverse seedling communities better resist herbivores, and herbivores help to maintain seedling diversity.

Anticipating the spatio-temporal response of plant diversity and vegetation structure to climate and land use change in a protected area.

Vegetation is a key driver of ecosystem functioning (e.g. productivity and stability) and of the maintenance of biodiversity (e.g. creating habitats for other species groups). While vegetation sensitivity to climate change has been widely investgated, its spatio-temporally response to the dual efects of land management and climate change has been ignored at landscape scale. Here we use a dynamic vegetation model called FATE-HD, which describes the dominant vegetation dynamics and associated functional diversity, in order to anticipate vegetation response to climate and land-use changes in both short and long-term perspectives. Using three contrasted management scenarios for the Ecrins National Park (French Alps) developed in collaboration with the park managers, and one regional climate change scenario, we tracked the dynamics of vegetation structure (forest expansion) and functional diversity over 100 years of climate change and a further 400 additional years of stabilization. As expected, we observed a slow upward shift in forest cover distribution, which appears to be severely impacted by pasture management (i.e. maintenance or abandonment). The tme lag before observing changes in vegetation cover was the result of demographic and seed dispersal processes. However, plant diversity response to environmental changes was rapid. Afer land abandonment, local diversity increased and spatial turnover was reduced, whereas local diversity decreased following land use intensification. Interestingly, in the long term, as both climate and management scenarios interacted, the regional diversity declined. Our innovative spatio-temporally explicit framework demonstrates that the vegetation may have contrasting responses to changes in the short and the long term. Moreover, climate and land-abandonment interact extensively leading to a decrease in both regional diversity and turnover in the long term. Based on our simulations we therefore suggest a continuing moderate intensity pasturing to maintain high levels of plant diversity in this system.

Quality over quantity: buffer strips can be improved with select native plant species.

Native plants attractive to beneficial insects may improve the value of buffer strips by increasing biodiversity and enhancing the delivery of insect-derived ecosystem services. In a 2-yr field experiment, we measured the response of insect communities across nine buffers that varied in plant diversity. We constructed buffers with plants commonly found in buffers of USDA-certified organic farms in Iowa (typically a single species), recommended for prairie reconstruction, or recommended for attracting beneficial insects. We hypothesized that the diversity and abundance of beneficial insects will be 1) greatest in buffers composed of diverse plant communities with continuous availability of floral resources, 2) intermediate in buffers with reduced species richness and availability of floral resources, and 3) lowest in buffers composed of a single species. We observed a significant positive relationship between the diversity and abundance of beneficial insects with plant community diversity and the number of flowers. More beneficial insects were collected in buffers composed of species selected for their attractiveness to beneficial insects than a community recommended for prairie restoration. These differences suggest 1) plant communities that dominate existing buffers are not optimal for attracting beneficial insects, 2) adding flowering perennial species could improve buffers as habitat for beneficial insects, 3) buffers can be optimized by intentionally combining the most attractive native species even at modest levels of plant diversity, and 4) plant communities recommended for prairie reconstruction may not contain the optimal species or density of the most attractive species necessary to support beneficial insects from multiple guilds.

Mechanisms linking plant community properties to soil aggregate stability in an experimental grassland plant diversity gradient

Soil aggregate stability depends on plant community properties, such as functional group composition, diversity and biomass production. However, little is known about the relative importance of these drivers and the role of soil organisms in mediating plant community effects. We studied soil aggregate stability in an experimental grassland plant diversity gradient and considered several explanatory variables to mechanistically explain effects of plant diversity and plant functional group composition. Three soil aggregate stability measures (slaking, mechanical breakdown and microcracking) were considered in path analyses. Soil aggregate stability increased significantly from monocultures to plant species mixtures and in the presence of grasses, while it decreased in the presence of legumes, though effects differed somewhat between soil aggregate stability measures. Using path analysis plant community effects could be explained by variations in root biomass, soil microbial biomass, soil organic carbon concentrations (all positive relationships), and earthworm biomass (negative relationship with mechanical breakdown). The present study identified important drivers of plant community effects on soil aggregate stability. The effects of root biomass, soil microbial biomass, and soil organic carbon concentrations were largely consistent across plant diversity levels suggesting that the mechanisms identified are of general relevance.

Host plant genus‐level diversity is the best predictor of ectomycorrhizal fungal diversity in a Chinese subtropical forest

Microbial diversity is generally far higher than plant diversity, but the relationship between microbial diversity and plant diversity remains enigmatic. To shed light on this problem, we examined the diversity of a key guild of root-associated microbes,that is, ectomycorrhizal (EM) fungi along a plant diversity gradient in a Chinese subtropical forest. The results indicated that EM fungal diversity was positively correlated with host plant diversity. Furthermore, this relationship was best predicted by host genus-level diversity, rather than species-level diversity or family-level diversity. The generality of this finding was extended beyond our study system through the analyses of 100 additional studies of EM fungal communities from tropical and temperate forests.Here as well, EM fungal lineage composition was significantly affected by EM plant diversity levels, and some EM fungal lineages were co-associated with some host plant genera. These results suggest a general diversity maintenance mechanism for host-specific microbes based on higher order host plant phylogenetic diversity.

Physical disturbance shapes vascular plant diversity more profoundly than fire in the sagebrush steppe of southeastern Idaho, U.S.A

Fire is thought to profoundly change the ecology of the sagebrush steppe. The Idaho National Laboratory provides an ideal setting to compare the effects of fire and physical disturbance on plant diversity in high-native-cover sagebrush steppe. Seventy-eight 1-hectare transects were established along paved, green-striped, gravel, and two-track roads, in overgrazed rangeland, and within sagebrush steppe involving different fire histories. Transects were sampled for the diversity and abundance of all vascular plants. Alpha, beta, and phylogenetic beta diversity were analyzed as a response to fire and physical disturbance. Postfire vegetation readily rebounds to prefire levels of alpha plant diversity. Physical disturbance, in contrast, strongly shapes patterns of alpha, beta, and especially phylogenetic beta diversity much more profoundly than fire disturbance. If fire is a concern in the sagebrush steppe then the degree of physical-disturbance should be more so. This finding is probably not specific to the study area but applicable to the northern and eastern portions of the sagebrush biome, which is characterized by a pulse of spring moisture and cold mean minimum winter temperatures. The distinction of sagebrush steppe from Great Basin sagebrush should be revised especially with regard to reseeding efforts and the control of annual grasses.

A checklist and floristic summary of the vascular plants of Napa County, California

Napa County contains particularly high levels of biological diversity in a variety of categories and is considered one of ten localized areas in California that contain the highest numbers of native and endemic plant species. Here we present a floristic summary based on a new annotated checklist of the flora of this uniquely diverse region. The checklist was developed by combining several local and statewide floristic data sources that represent herbarium collection records and other observations from Napa County. The final checklist of vascular plants for Napa County consists of 1,716 taxa, including 1,418 native taxa from 101 different families. Alarmingly, 126 native taxa in Napa County were listed as rare or threatened to some degree. The results of this study demonstrate that for its size, Napa County contains remarkably high levels of plant diversity as well as high concentrations of special status taxa as compared to other areas within the California Floristic Province, the State of California as a whole, and other regions within global biodiversity hotspots characterized by Mediterranean climates. In particular, this analysis highlights the floristic significance of Napa County at global and local levels, and thus, this review is an important step to help promote and facilitate long term research and conservation planning in the area.

Composição da flora arbórea e arborescente no Jardim Botânico de Bento Gonçalves, Rio Grande do Sul, Brasil

Este estudo teve como objetivo o levantamento florístico e fitossociológico de uma área de 178.000 m², situada nas coordenadas 29º10'38"S e 51º27'16"W, na localidade de Linha Palmeiro, Distrito de São Pedro, no Município de Bento Gonçalves, RS, Brasil, onde se encontra o Jardim Botânico de Bento Gonçalves, o qual se situa numa zona de transição de três formações vegetais distintas: Floresta Ombrófila Mista, Floresta Estacional Decidual e resquícios de Mata Atlântica. O local é uma área de conservação in situ no Jardim Botânico de Bento Gonçalves. O método de amostragem utilizado foi o de parcelas distribuídas ao acaso. Avaliaram-se 10 parcelas medindo 50 x 50 m cada. Dentro de cada parcela, foram amostrados indivíduos com circunferência à altura do peito (CAP) superior ou igual a 30 cm. Foram amostrados 1.947 indivíduos vivos dentro de 35 famílias botânicas, além de 109 indivíduos mortos ainda em pé. As famílias mais expressivas em número de indivíduos e em espécies foram Sapindaceae, Anacardiaceae, Myrtaceae, Oleaceae e Lauraceae. As espécies com maiores valores de importância foram Matayba elaeagnoides Radlk., Araucaria angustifolia (Bertol.) Kuntze, Lithraea brasiliensis Marchand, Ligustrum licidum W. T. Aiton e Sebastiania serrata (Klotzsch) Müll. Arg. O índice de diversidade de Shannon foi de 3,18 nats/indivíduos, enquanto a equabilidade de Pielou (J'), 0,71, valores esses considerados altos se comparados a de outros levantamentos. O número de espécies identificadas evidenciou nível alto de diversidade florística, que se caracterizou pela associação de diferentes contingentes florestais, com predomínio daquelas de ampla distribuição na área.