Summary1. The diversity of pathogens on highly abundant introduced hosts has been positively correlated with time since introduction, geographical range of the introduced species and diversity of invaded habitats. However, little is known about the ecological effects of pathogen accumulation on nonnative invasive plants.2. Pathogen accumulation on invasive plant species may result from ecological processes such as high plant densities, expanding geographical ranges and pathogen dispersal from the native range, or evolutionary mechanisms such as host range shifts and adaptation of native pathogens to invasive species. 3. Over time pathogen accumulation may cause decline in the density and distribution of invasive plants and facilitate recovery of native species. Alternatively, pathogens might build up on invasive species and then spill back onto co-occurring native species, further exacerbating the effects of invasions. 4. Synthesis. Research efforts should focus on determining the long-term outcomes of pathogen accumulation on invasive species. Such research will require multifaceted approaches including comparative studies of diverse invasive species and habitats, experimental manipulations of hosts and pathogens in nature and controlled environments, and predictive models of host-pathogen interactions within an invasion framework. Results of this research will improve our understanding and ability to predict the outcomes of biological invasions.

Despite the large contribution of rangeland and pasture to global soil organic carbon (SOC) stocks, there is considerable uncertainty about the impact of large herbivore grazing on SOC, especially for understudied subtropical grazing lands. It is well known that root system inputs are the source of most grassland SOC, but the impact of grazing on partitioning of carbon allocation to root tissue production compared to fine root exudation is unclear. Given that different forms of root C have differing implications for SOC synthesis and decomposition, this represents a significant gap in knowledge. Root exudates should contribute to SOC primarily after microbial assimilation, and thus promote microbial contributions to SOC based on stabilization of microbial necromass, whereas root litter deposition contributes directly as plant-derived SOC following microbial decomposition. Here, we used in situ isotope pulse-chase methodology paired with plant and soil sampling to link plant carbon allocation patterns with SOC pools in replicated long-term grazing exclosures in subtropical pasture in Florida, USA. We quantified allocation of carbon to root tissue and measured root exudation across grazed and ungrazed plots and quantified lignin phenols to assess the relative contribution of microbial vs. plant products to total SOC. We found that grazing exclusion was associated with dramatically less overall belowground allocation, with lower root biomass, fine root exudates, and microbial biomass. Concurrently, grazed pasture contained greater total SOC, and a larger fraction of SOC that originated from plant tissue deposition, suggesting that higher root litter deposition under grazing promotes greater SOC. We conclude that grazing effects on SOC depend on root system biomass, a pattern that may generalize to other C4-dominated grasslands, especially in the subtropics. Improved understanding of ecological factors underlying root system biomass may be the key to forecasting SOC and optimizing grazing management to enhance SOC accumulation.

Novel species of microfungi described in the present study include the following from South Africa: Camarosporium aloes, Phaeococcomyces aloes and Phoma aloes from Aloe, C. psoraleae, Diaporthe psoraleae and D. psoraleae-pinnatae from Psoralea, Colletotrichum euphorbiae from Euphorbia, Coniothyrium prosopidis and Peyronellaea prosopidis from Prosopis, Diaporthe cassines from Cassine, D. diospyricola from Diospyros, Diaporthe maytenicola from Maytenus, Harknessia proteae from Protea, Neofusicoccum ursorum and N. cryptoaustrale from Eucalyptus, Ochrocladosporium adansoniae from Adansonia, Pilidium pseudoconcavum from Greyia radlkoferi, Stagonospora pseudopaludosa from Phragmites and Toxicocladosporium ficiniae from Ficinia. Several species were also described from Thailand, namely: Chaetopsina pini and C. pinicola from Pinus spp., Myrmecridium thailandicum from reed litter, Passalora pseudotithoniae from Tithonia, Pallidocercospora ventilago from Ventilago, Pyricularia bothriochloae from Bothriochloa and Sphaerulina rhododendricola from Rhododendron. Novelties from Spain include Cladophialophora multiseptata, Knufia tsunedae and Pleuroascus rectipilus from soil and Cyphellophora catalaunica from river sediments. Species from the USA include Bipolaris drechsleri from Microstegium, Calonectria blephiliae from Blephilia, Kellermania macrospora (epitype) and K. pseudoyuccigena from Yucca. Three new species are described from Mexico, namely Neophaeosphaeria agaves and K. agaves from Agave and Phytophthora ipomoeae from Ipomoea. Other African species include Calonectria mossambicensis from Eucalyptus (Mozambique), Harzia cameroonensis from an unknown creeper (Cameroon), Mastigosporella anisophylleae from Anisophyllea (Zambia) and Teratosphaeria terminaliae from Terminalia (Zimbabwe). Species from Europe include Auxarthron longisporum from forest soil (Portugal), Discosia pseudoartocreas from Tilia (Austria), Paraconiothyrium polonense and P. lycopodinum from Lycopodium (Poland) and Stachybotrys oleronensis from Iris (France). Two species of Chrysosporium are described from Antarctica, namely C. magnasporum and C. oceanitesii. Finally, Licea xanthospora is described from Australia, Hypochnicium huinayensis from Chile and Custingophora blanchettei from Uruguay. Novel genera of Ascomycetes include Neomycosphaerella from Pseudopentameris macrantha (South Africa), and Paramycosphaerella from Brachystegia sp. (Zimbabwe). Novel hyphomycete genera include Pseudocatenomycopsis from Rothmannia (Zambia), Neopseudocercospora from Terminalia (Zambia) and Neodeightoniella from Phragmites (South Africa), while Dimorphiopsis from Brachystegia (Zambia) represents a novel coelomycetous genus. Furthermore, Alanphillipsia is introduced as a new genus in the Botryosphaeriaceae with four species, A. aloes, A. aloeigena and A. aloetica from Aloe spp. and A. euphorbiae from Euphorbia sp. (South Africa). A new combination is also proposed for Brachysporium torulosum (Deightoniella black tip of banana) as Corynespora torulosa. Morphological and c...

Summary 1.Restoration of habitats invaded by non-native plants should include both the removal of invasive plants and re-establishment of native plant communities. To develop appropriate restoration strategies and quantify the effects of invasions, experiments that evaluate multiple removal methods and native community responses to those removal methods are needed. 2. We evaluated the response of native plant communities to removal of the invasive grass Microstegium vimineum (Japanese stiltgrass) in eastern forests in the USA. At eight field sites in southern Indiana, we applied three common removal treatments and compared native community responses among treatments and to untreated reference plots. 3. After 2 years of treatment, native community responses to Microstegium removal varied significantly among methods and plant functional groups in autumn 2006. Graminoid richness was greater when the invader was removed with hand-weeding, while graminoid biomass was lower in plots treated with post-emergent herbicide compared to reference plots. Forb richness was greater with hand-weeding and post-emergent herbicide compared to plots treated with post-emergent plus pre-emergent herbicides or untreated plots. Forb biomass was greater across all removal treatments. Overall native community diversity was 24% greater when the invasion was removed with handweeding and 21% greater with post-emergent herbicide compared to reference plots. No positive response in plant diversity occurred with post-emergent plus pre-emergent herbicide. 4. By spring 2007, graminoid percentage cover was greater with hand-weeding but not with herbicide treatments compared to untreated plots. However, forb cover was greater across all removal treatments compared to plots where the invader was not removed. The density of native tree seedlings was 123% greater in post-emergent herbicide treated plots than in untreated plots, indicating that the invasion was inhibiting tree recruitment. Synthesis and applications.Our results demonstrate that multiple techniques can be used to control invasive plants but that the responses of native plant communities vary among removal methods. Further, greater native plant diversity and biomass following removal shows that invasions were suppressing native plant communities. Management of plant invasions should consider not only the effectiveness of removal methods but also how different methods influence native plant responses.

Emerging pathogens are a growing threat to human health, agriculture and the diversity of ecological communities but may also help control problematic species. Here we investigated the diversity, distribution and consequences of emerging fungal pathogens infecting an aggressive invasive grass that is rapidly colonising habitats throughout the eastern USA. We document the recent emergence and accumulation over time of diverse pathogens that are members of a single fungal genus and represent multiple, recently described or undescribed species. We also show that experimental suppression of these pathogens increased host performance in the field, demonstrating the negative effects of emerging pathogens on invasive plants. Our results suggest that invasive species can facilitate pathogen emergence and amplification, raising concerns about movement of pathogens among agricultural, horticultural, and wild grasses. However, one possible benefit of pathogen accumulation is suppression of aggressive invaders over the long term, potentially abating their negative impacts on native communities.