Vascular plants occurrences in Dokdo Islands, Korea, based on herbarium collections and legacy botanical literature

The vascular flora of the Dokdo Islands has been reported, based on primary collections made in 2012 and 2013 and legacy botanical literature. The Dokdo Islands are the remotest islands of Korea, located in the East Sea approximately 87 km from Ulleungdo Islands. They comprise two main volcanic islands, Dongdo (east islands) and Seodo (west islands) and minor islets surrounding the two main islands. This research was conducted to document vascular plant species inhabiting Korea's most inaccessible islands. We present a georeferenced dataset of vascular plant species collected during field studies on the Dokdo Islands over the past seven decades. In the present inventory of the flora of Dokdo, there are listed 108 species belonging to 78 genera and 39 families, including 93 native species and 15 newly human-induced naturalised species for these Islands' flora. The Poaceae and Asteraceae families are the most diverse, with 22 and 15 taxa, respectively. Some of the previously-listed taxa were not found on Dokdo probably because they are rare and the limited time did not allow collectors to find rare species. The spread of introduced species, especially the invasive grass Bromus catharticus Vahl., affects several native species of Dokdo flora.

Allergenicity to worldwide invasive grass Cortaderia selloana as environmental risk to public health

Allergies to grass pollen affects about 20% of the population worldwide. In the last few decades, the South American grass Cortaderia selloana (CS, Pampas grass) has expanded worldwide in a variety of countries including the USA, Australia and Western Europe. In many of these locations, CS has strikingly spread and has now been classified an invasive species. Many pernicious consequences of CS have been reported for local biodiversity, landscape and structures. However, the effect on human health has not been studied. To investigate this issue, we have chosen a European region on the northern cost of Spain where CS spread is overwhelming, Cantabria. We obtained CS pollen extract and analysed the allergenic reaction of 98 patients that were allergic to pollen of local grasses. We determined the skin reaction and the presence of specific IgE antibodies (sIgE) to CS or to a typical autochthonous grass, Phleum pratense. We also compared the seasonal symptoms with reported grass pollen counts in the area. The results strongly suggest that CS can cause respiratory allergies at a similar extent to the local grasses. Given that CS pollinises later than the local grasses, this would extend the period of grass allergies in the region for about three months every year, as stated by most of the patients. This is the first study reported on the effects of the striking expansion of CS on human health. Considering the strong impact that respiratory allergies have on the population, our results suggest that CS can currently constitute a relevant environmental health issue.

Biogeochemical Effects of a Forest Understory Plant Invasion Depend More On Dissimilar Nutrient Economies Than Invader Biomass

There is an increasing need to better understand how and why invasion impacts differ across heterogeneous landscapes. One hypothesis predicts invader impacts are greatest where the invader is most abundant (the mass ratio hypothesis; MRH). Alternatively, invader impacts may be greatest in communities where the nutrient acquisition strategies of the invader are most dissimilar from those of native species (the nutrient economy dissimilarity hypothesis; NEDH). We tested whether the effects of an invasive grass, Microstegium vimineum, on soil biogeochemistry were best explained by MRH, NEDH, or both. At three locations (Indiana, North Carolina, and Georgia), invaded and reference plots were established across a nutrient economy gradient. Plots varied in the relative abundance of arbuscular mycorrhizal (AM) vs. ectomycorrhizal (ECM) associated overstory trees, reflecting gradients in biotic nutrient acquisition strategies and edaphic factors. At two locations, we found NEDH predicted invader effects on soil conditions. The net effect of M. vimineum homogenized soil properties across the nutrient economy gradient towards conditions consistent with AM-dominated stands; as such, the nutrient economy gradients observed in uninvaded plots were mostly absent in invaded plots. At one location with high N availability and intermediate acidity, both ECM-dominance (NEDH) and invader abundance (MRH) predicted differences in soil moisture, pH, and nitrification rates. Collectively, these results suggest the biogeochemical consequences of M. vimineum depend, in part, on pre-invasion soil nutrient economies. Where pre-invasion conditions are known, we provide a scalable and predictive approach to determine where impacts on biogeochemical cycling of C and N may be greatest.

Effects of post oak Quercus Stellata and Smooth Brome Bromus Inermis Competition on Water Uptake and Root Partitioning of Eastern Redcedar Juniperus Virginiana

Water availability may alter species competitive interactions, resulting in different outcomes as plants compete for available water. Eastern redcedar Juniperus virginiana (hereafter ERC) will likely continue to encroach into new habitats, which will affect soil and water budgets. We designed a greenhouse experiment to investigate changes in water uptake and rooting depths of two-year old ERC saplings in the presence of an invasive grass (Bromus inermis) and a native tree (Quercus stellata). We measured soil moisture content over two growing seasons. When grown together, ERC took up water from the deeper layers (21–40 cm) whereas B. inermis used water from the top layers of the soil (0–20 cm). Similarly, when ERC grew with Q. stellata, ERC took up water from the deeper layers and Q. stellata used water mostly from the top layers. This root partitioning can allow the co-existence of ERC, grasses, and other trees, which can facilitate ERC encroachment into grasslands and woodlands. However, when the three species grew together, we found root overlap between the ERC and Q. stellata. This overlap can affect ERC establishment and encroachment in habitats where grasses and trees co-occur. A major factor that affected ERC performance was higher mortality in treatments with B. inermis than in the ERC-alone or with Q. stellata. This indicates that competition with grasses is a major factor affecting ERC sapling establishment.

Prediction Models for Evaluating the Uptake of Heavy Metals by the Invasive Grass Vossia cuspidata (Roxb.) Griff. in the River Nile, Egypt: A Biomonitoring Approach

This study aimed to develop new prediction models that include sediment properties (pH, organic matter, and silt and clay concentrations) for estimating the potential uptake of heavy metals (HMs) by the invasive grass Vossia cuspidata. Plant and sediment samples were collected from the microsites that represent the natural distribution of the species in two Nile islands in Cairo, Egypt. The results show that the root was the main accumulating organ for the analyzed HMs (Fe, Mn, Zn, Cu, Ni, and Pb). The mean concentrations of Fe and Mn and the maximum concentrations of Cu, Ni, and Pb were phytotoxic. The values of the bioconcentration factor were >1, while the translocation factor was >1 for Zn and Cu in rhizome and stem, Mn in leaf, and Ni and Pb in stem and leaf. There were no significant differences between the measured and the predicted HM concentrations in all organs of the species. This indicates the excellent robustness of the developed regression models. Sixteen equations (out of 24) had high R2 values. Thus, V. cuspidata could be considered a biomonitor for HM pollution, and the developed equations will benefit the prediction of HM uptake by the species in the River Nile ecosystem.

Species introductions through coconut fibre

Based on plant material collected in the forest nursery of the Balearic Island Forestry Center (CEFOR) for autochthonous plant production and the University of the Balearic Islands experimental facilities, two new plant records are presented for the Mediterranean island of Mallorca. Dactyloctenium aegyptium, an invasive grass previously recorded in other areas of the Mediterranean basin, and Glinus oppositifolius, a new record for the European flora. In both cases the species are presumed to have arrived through contaminated batches of the coconut fibre substrate used in both facilities.

Invasive Grass Dominance over Native Forbs Is Linked to Shifts in the Bacterial Rhizosphere Microbiome

Rhizosphere microbiomes have received growing attention in recent years for their role in plant health, stress tolerance, soil nutrition, and invasion. Still, relatively little is known about how these microbial communities are altered under plant competition, and even less about whether these shifts are tied to competitive outcomes between native and invasive plants. We investigated the structure and diversity of rhizosphere bacterial and fungal microbiomes of native annual forbs and invasive annual grasses grown in a shade-house both individually and in competition using high-throughput amplicon sequencing of the bacterial 16S rRNA gene and the fungal ITS region. We assessed how differentially abundant microbial families correlate to plant biomass under competition. We find that bacterial diversity and structure differ between native forbs and invasive grasses, but fungal diversity and structure do not. Furthermore, bacterial community structures under competition are distinct from individual bacterial community structures. We also identified five bacterial families that varied in normalized abundance between treatments and that were correlated with plant biomass under competition. We speculate that invasive grass dominance over these natives may be partially due to effects on the rhizosphere community, with changes in specific bacterial families potentially benefiting invaders at the expense of natives.

Phytotoxicity and allelopathic potential of extracts from rhizomes and leaves of Arundo donax, an invasive grass in neotropical savannas

The perennial rhizomatous grass Arundo donax L. (Poaceae), the giant reed, is an exotic invasive species in several countries of Europe that is rapidly spreading in the savannas of Central Brazil, locally known as Cerrado. Allelopathy could facilitate the successful invasion of this species by hampering or suppressing the regeneration of the native vegetation. However, information on the phytotoxicity of A. donax extracts is limited. We investigated the allelopathic potential of A. donax leaf and rhizome extracts, screened them for phytochemicals by thin-layer chromatography (TLC) and nuclear magnetic resonance (1H-NMR), and tested the extracts for antioxidant activity, antimicrobial activity, and cytotoxicity against Artemia salina. Aqueous and methanolic extracts were initially tested in germination and seedling growth bioassays using Lactuca sativa L. (Asteraceae). The aqueous extracts were then tested on five Cerrado tree species and on Megathyrsus maximus, an invasive, alien grass in the Cerrado. Extracts negatively affected germination and seedling growth of the target species. Leaf extracts were more inhibitory. Extracts did not show antioxidant and cytotoxic activity and had very low antimicrobial activity. Flavonoids, and other phenolics were detected mostly in leaves. Terpenes, which were also present in the leaves, were the main secondary metabolites in rhizomes. Alkaloids were detected by TLC in leaf methanolic extracts. However, 1H-NMR revealed the presence of indole alkaloids in methanolic extracts from rhizomes and leaves. We confirmed the allelopathic potential of this species and caution against weed control methods relying on cutting the plant back to soil level for favouring release of allelochemicals.