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Invasive alien plants may profoundly transform ecosystems over wide areas. The study aimed to assess how the invader Reynoutria bohemica could transform ecosystem components of a native riparian forest in Northern Italy, after about 20 years of invasion. We selected 20 forest sites where we set up two 1 × 1 m plots, one in an invaded and one in a non‐invaded patch. Subsequently, we surveyed the properties of litter and mineral soil, soil biological quality (QBS‐ar), diversity of plant and microarthropod communities and light intensity at the ground level. To determine if the invader affected the quality of herb layer, we selected the native herb Allium ursinum as the indicator species of good quality forest stand and measured its traits in the paired plots. Following the application of linear mixed effects models, the invaded and non‐invaded plots showed differences in soil characteristics and plant community: the thickness of the organic horizon, soil C:N and available P were higher in invaded plots, whereas diversity, light intensity, Allium ursinum abundance and its vegetative vigour were found to be lower. Microarthropod communities and QBS‐ar were modestly influenced by R. bohemica. Redundancy analysis of plant community composition indicated that soil C:N and plant richness were the variables most linked to species invasion. This study highlights the ability of R. bohemica to transform certain ecosystem components in native riparian forests, after just a few decades since its first invasion, thereby underlining the need to implement measures to control its spread. [ABSTRACT FROM AUTHOR]

Studies on plant growth and trait variation along environmental gradients can provide important information for identifying drivers of plant invasions and for deriving management strategies. We used seeds of the annual plant invader Ambrosia artemisiifolia L. (common ragweed) collected from an agricultural site in Northern Italy (226 m. a.s.l; Mean Annual Air Temperature: 12.9 °C; precipitations: 930 mm) to determine variation in growth trajectories and plant traits when grown along a 1000-m altitudinal gradient in Northern Italy, and under different temperature conditions in the growth chamber (from 14/18 °C to 26/30 °C, night/day), using a non-liner modeling approach. Under field conditions, traits related to plant height (maximum height, stem height, number of internodes) followed a three-parameter logistic curve. In contrast, leaf traits (lateral spread, number of leaves, leaf length and width) followed non-monotonic double-Richards curves that captured the decline patterns evident in the data. Plants grew faster, reaching a higher maximum plant height, and produced more biomass when grown at intermediate elevations. Under laboratory conditions, plants exhibited the same general growth trajectory of field conditions. However, leaf width did not show the recession after the maximum value shown by plants grown in the field, although the growth trajectories of some individuals, particularly those grown at 18 °C, showed a decline at late times. In addition, the plants grown at lower temperatures exhibited the highest value of biomass and preserved reproductive performances (e.g., amount of male inflorescence, pollen weight). From our findings, common ragweed exhibits a high phenotypic plasticity of vegetative and reproductive traits in response to different altitudes and temperature conditions. Under climate warming, this plasticity may facilitate the shift of the species towards higher elevation, but also the in situ resistance and (pre)adaptation of populations currently abundant at low elevations in the invasive European range. Such results may be also relevant for projecting the species management such as the impact by possible biocontrol agents. [ABSTRACT FROM AUTHOR]

Using native seed mixtures to create or recover grassland habitats in rotation to crops or in strips surrounding fields is considered a cost-effective practice to enhance ecosystem resilience and agro-biodiversity. The aim of this research was to assess the effects of native hayseed mixtures on plant and microarthropod communities in an agricultural area of Northern Italy. Three different experimental treatments were set up. The first was a control (C) (i.e., non-seeded plots left to spontaneous vegetation succession after ploughing no deeper than 15 cm). The second, hayseed seeded (Hs) after ploughing no deeper than 15 cm. The third experimental treatment was hayseed overseeded (Ov) on the resident plant community after only a superficial harrowing. Ov plots exhibited the preeminent positive effects on the total productivity and quality of the grassland in terms of total vegetation cover, cover and richness of typical grassland species (i.e., Molinio-Arrhenatheretea species), and cover of legumes, grasses and perennial species. Moreover, Ov sites exhibited the highest abundance of microarthropod taxa and soil biological quality (QBS-ar) but only in spring, when the disturbance of ploughing negatively affected Hs and C plots. On the other hand, Hs sites showed a great reduction of invasive alien (i.e., Ambrosia artemisiifolia and Artemisia verlotiorum) and segetal weed species (i.e., Capsella bursa-pastoris and Spergula arvensis) in terms of cover. This study provides valuable indication on using hayseed mixtures to create grassland habitats as reservoir of native flora and soil biodiversity in agriculture areas. [ABSTRACT FROM AUTHOR]