Summary: Ectomycorrhizal (EM) fungi play key roles in forest ecosystems, but the potential effects of invasive plants on EM fungal communities have not been assessed. In this study, we tested whether the non‐mycorrhizal herbaceous plant Alliaria petiolata (garlic mustard) can alter the abundance of EM fungal communities in North America. In three forests in New England, USA, we compared EM root tip abundance in soils where A. petiolata had invaded to adjacent areas without a history of A. petiolata invasion. At one site, we also intensively sampled EM root tip abundance across the edges of A. petiolata patches to determine the spatial pattern of A. petiolata effects on EM fungi. In a glasshouse experiment, we experimentally invaded soils with A. petiolata and Impatiens capensis, a native species and compared EM fungal colonization of white pine (Pinus strobus) seedlings grown in both soils. We also measured the effect of the A. petiolata allelochemical benzyl isothiocyanate on the growth of three species of EM fungi in pure culture. In the field, EM fungal root tip biomass was lower in invaded soils, with the strongest reductions observed in forests dominated by conifers. Alliaria petiolata invasion did not have a significant effect on total root biomass. The influence of A. petiolata on EM fungal abundance in the field was localized, with the strongest inhibition observed within 10 cm of the edge of A. petiolata patches. Pine seedlings growing in soils that were experimentally invaded with A. petiolata also had lower EM fungal root tip biomass compared to uninvaded soils. The native species I. capensis caused similar reductions in EM fungal colonization. Growth of pure cultures of all three species of EM fungi was completely inhibited by benzyl isothiocyanate. Synthesis. Alliaria petiolata inhibits the growth of EM fungi in forests of its introduced range. Changes in EM fungal communities caused by the invasion of A. petiolata may influence tree seedling establishment and biogeochemical cycling.

Garlic mustard (Alliaria petiolata) is a nonnative, shade-tolerant forb that was introduced into North America in the mid-1800s. Currently, garlic mu

The biological responses to precipitation within the terrestrial components of Earth system models, or land surface models (LSMs), are mechanistically simple and poorly constrained, leaving projections of terrestrial ecosystem functioning and feedbacks to climate change uncertain. A number of field experiments have been conducted or are underway to test how changing precipitation will affect terrestrial ecosystems. Results from these experiments have the potential to vastly improve modeled processes. However, the transformation of experimental results into model improvements still represents a grand challenge. Here we review the current state of precipitation manipulation experiments and the precipitation responses of biological processes in LSMs to explore how these experiments can help improve model realism. First, we discuss contemporary precipitation projections and then review the structure and function of current-generation LSMs. We then examine different experimental designs and discuss basic variables that, if measured, would increase a field experiment's usefulness in a modeling context. Next, we compare biological processes commonly measured in the field with their model analogs and find that, in many cases, the way these processes are measured in the field is not compatible with the way they are represented in LSMs, an effect that hinders model development. We then discuss the challenge of scaling from the plot to the globe. Finally, we provide a series of recommendations aimed to improve the connectivity between experiments and LSMs and conclude that studies designed from the perspective of researchers in both communities will provide the greatest benefit to the broader global change community.

Predicting the effects of climate change on tree species and communities is critical for understanding the future state of our forested ecosystems. We used a fully factorial precipitation (three levels; ambient, −50 % ambient, +50 % ambient) by warming (four levels; up to +4 °C) experiment in an old-field ecosystem in the northeastern USA to study the climatic sensitivity of seedlings of six native tree species. We measured whole plant-level responses: survival, total leaf area (TLA), seedling insect herbivory damage, as well as leaf-level responses: specific leaf area (SLA), leaf-level water content (LWC), foliar nitrogen (N) concentration, foliar carbon (C) concentration and C:N ratio of each of these deciduous species in each treatment across a single growing season. We found that canopy warming dramatically increased the sensitivity of plant growth (measured as TLA) to rainfall across all species. Warm, dry conditions consistently reduced TLA and also reduced leaf C:N in four species (Acer rubrum, Betula lenta, Prunus serotina, Ulmus americana), primarily as a result of reduced foliar C, not increased foliar N. Interestingly, these conditions also harmed the other two species in different ways, increasing either mortality (Populus grandidentata) or herbivory (Quercus rubra). Specific leaf area and LWC varied across species, but did not show strong treatment responses. Our results indicate that, in the northeastern USA, dry years in a future warmer environment could have damaging effects on the growth capacity of these early secondary successional forests, through species-specific effects on leaf production (total leaves and leaf C), herbivory and mortality.