1. With evidence of significant global insect declines mounting, urgent calls to mitigate such declines are also increasing. Efforts to reverse insect declines will only succeed, however, if we correctly identify and address their major causes.2. One potential cause that has received little mention is the global spread of non-native plants as invasive species, agroforestry products, and ornamental plants.3. Here we (a) review the theory predicting that most insect herbivores are evolutionarily constrained to use a fraction of available plant lineages; (b) document the extent to which nonnative plants have displaced native plant communities around the globe; (c) examine the evidence that non-native plants reduce insect abundance and diversity; and (d) suggest guidelines for measuring the impact of non-native plants on insect populations.4. We conclude that host range expansions to non-natives do occur among many insect herbivores but not at the frequency required to prevent insect declines when non-native plants replace native plant communities. Accordingly, we suggest that curbing the spread and use of non-native plants at local, national, and international scales will be a necessary and effective way to reduce some insect declines.

No abstract

Biochar has many potential benefits in agroecosystems such as increasing productivity of crops and modifying soil nutrient content. Biochar is sourced from many waste materials which could easily and sustainably remedy current challenges in concentrated agricultural operations that use manure-based fertilizers. However, relatively little is known about its effects on forage species in conjunction with manure or biochar enriched with manure effluent. Our objective was to look at the effect of biochar and dairy effluent soil amendments on a forage legume and a grass. In this study, sandy loam soil was amended with a variety of biochar (BC) in a greenhouse setting. Factors included (1) BC type; (2) BC loading percentage; (3) effluent saturation of BC; and (4) forage inclusion. The study was repeated twice: once with Trifolium incarnatum and once with Lolium multiflorum. Plant material was assayed for biomass (BM) and C and N content. Soil was assayed for nutrient content and micronutrients. Data were not normally distributed and were consequently analyzed for variance using non-parametric methods in R. Overall, T. incarnatum showed a very strong negative (p ≤ 0.05) impact associated with increasing loading percentages of blend and manure BC on herbage BM, while effluent saturation showed no effect (p > 0.05). In contrast, L. multiflorum showed a strong (p ≤ 0.05) positive impact of increasing loading percentages of saturated wood, blend, and manure BC on herbage BM. BC impact on soil nutrients and forage varied greatly depending on type of BC, loading percentage, and forage species included. Results indicated the importance of BC properties and rates, as well as forage species for nutrient tolerances when choosing a BC amendment and loading rate.

Nonnative plants alter the composition of native plant communities, with concomitant effects on arthropods. However, plant invasions may not be the only disturbance affecting native communities, and multiple disturbances can have compounding effects. We assessed the effects of invasion and drought on plant and arthropod communities by comparing grasslands dominated by nonnative Old World blue-stem grasses (OWBs, Dichanthium annulatum) to grasslands dominated by native plants during a period of decreasing drought severity (2011-2013). Native plant communities had more species of plants and arthropods (/ m2) than areas dominated by OWBs during extreme drought, but richness was comparable as drought severity decreased. Abundance of arthropods was greater in native plant communities than in OWB communities during extreme drought, but OWB communities had more arthropods during moderate and non-drought conditions. We observed a shift in the arthropod community from one dominated by detriti-vores to one dominated by herbivores following plant invasion; the magnitude of this shift increased as drought severity decreased. Both plant communities were dominated by nonnative arthropods. A nonnative leafhopper (Balclutha rubrostriata) and native mites (Mochlozetidae) dominated OWB communities as drought severity decreased, and OWBs may serve as refugia for both taxa. Nonnative woodlice (Armadil-lidium vulgare) dominated native plant communities during extreme and non-drought conditions and abundance of this species may be associated with an increase in plant litter and available nutrients. Given the importance of arthropods for ecosystem services, incorporating arthropod data into conservation studies may demonstrate how changes in arthropod diversity alter ecosystem function where nonnative plants are dominant.