The response of litter decomposition to extreme drought modified by plant species, plant part, and soil depth in a temperate grassland.

Plant litter decomposition is a key ecosystem process in carbon and nutrient cycling, and is heavily affected by changing climate. While the direct effects of drought on decomposition are widely studied, in order to better predict the overall drought effect, indirect effects associated with various drought-induced changes in ecosystems should also be quantified. We studied the effect of an extreme (5-month) experimental drought on decomposition, and if this effect varies with two dominant perennial grasses, plant parts (leaves vs. roots), and soil depths (0-5 cm vs. 10-15 cm) in a semi-arid temperate grassland. After 12 months, the average litter mass loss was 43.5% in the control plots, while only 25.7% in the drought plots. Overall, mass loss was greater for leaves (44.3%) compared to roots (24.9%), and for Festuca vaginata (38.6%) compared to Stipa borysthenica (30.5%). This variation was consistent with the observed differences in nitrogen and lignin content between plant parts and species. Mass loss was greater for deep soil (42.8%) than for shallow soil (26.4%). Collectively, these differences in decomposition between the two species, plant parts, and soil depths were similar in magnitude to direct drought effect. Drought induces multiple changes in ecosystems, and our results highlight that these changes may in turn modify decomposition. We conclude that for a reliable estimate of decomposition rates in an altered climate, not only direct but also indirect climatic effects should be considered, such as those arising from changing species dominance, root-to-shoot ratio, and rooting depth.

Composted Municipal Green Waste Infused with Biocontrol Agents to Control Plant Parasitic Nematodes-A Review.

The last few years have witnessed the emergence of alternative measures to control plant parasitic nematodes (PPNs). We briefly reviewed the potential of compost and the direct or indirect roles of soil-dwelling organisms against PPNs. We compiled and assessed the most intensively researched factors of suppressivity. Municipal green waste (MGW) was identified and profiled. We found that compost, with or without beneficial microorganisms as biocontrol agents (BCAs) against PPNs, were shown to have mechanisms for the control of plant parasitic nematodes. Compost supports a diverse microbiome, introduces and enhances populations of antagonistic microorganisms, releases nematicidal compounds, increases the tolerance and resistance of plants, and encourages the establishment of a "soil environment" that is unsuitable for PPNs. Our compilation of recent papers reveals that while the scope of research on compost and BCAs is extensive, the role of MGW-based compost (MGWC) in the control of PPNs has been given less attention. We conclude that the most environmentally friendly and long-term, sustainable form of PPN control is to encourage and enhance the soil microbiome. MGW is a valuable resource material produced in significant amounts worldwide. More studies are suggested on the use of MGWC, because it has a considerable potential to create and maintain soil suppressivity against PPNs. To expand knowledge, future research directions shall include trials investigating MGWC, inoculated with BCAs.

Toxicity mitigation by N-acetylcysteine and synergistic toxic effect of nano and bulk ZnO to Panagrellus redivivus.

To better understand the nanosize-relevant toxic effects and underlying mechanisms, N-acetylcysteine (NAC), as a mitigation agent, an ionic form of Zn (ZnCl2), and the binary mixture of ZnO with different particle sizes (15 nm and 140 nm), was used in toxicity assays with the nematode Panagrellus redivivus. The ZnCl2 concentrations were applied to show the amount of dissolved Zn ions present in the test system. Reactive oxygen species (ROS) measuring method was developed to fit the used test system. Our studies have shown that NAC can mitigate the toxic effects of both studied particle sizes. In the applied concentrations, ZnCl2 was less toxic than both of the ZnO particles. This finding indicates that not only ions and ROS produced by the dissolution are behind the toxic effects of the ZnO NPs, but also other particle size-dependent toxic effects, like the spontaneous ROS generation, are also relevant. When the two materials were applied in binary mixtures, the toxic effects increased significantly, and the dissolved zinc content and the ROS generation also increased. It is assumed that the chemical and physical properties of the materials have been mutually reinforcing to form a more reactive mixture that is more toxic to the P. redivivus test organism. Our findings demonstrate the importance of using mitigation agent and mixtures to evaluate the size-dependent toxicity of the ZnO.

Transgenerational and multigenerational stress gene responses to the insecticide etofenprox in Folsomia candida (Collembola).

Insecticide exposure may cause both transgenerational and multigenerational effects on populations, but the molecular mechanisms of these changes remain largely unclear. Many studies have focused on either transgenerational or multigenerational mechanisms but did neglect the comparative aspects. This study assessed whether the pyrethroid insecticide etofenprox (formulation Trebon® 30 EC) shows transgenerational and/or multigenerational effects on the survival and reproduction of Folsomia candida (Collembola). The activation of stress-related genes was studied to detect whether etofenprox modifies the expression of reproduction-associated genes in trans- and multigenerational treatments. A laboratory study was carried out for three generations with five insecticide concentrations in LUFA 2.2 soil. In the transgenerational treatment, only the parent generation (P) was exposed, but the subsequent generations were not. In the multigenerational treatment, all three generations were exposed to the insecticide in the same manner. Multigenerational exposure resulted in reduced reproduction effects over generations, suggesting that F. candida is capable of acclimating to enhanced concentration levels of etofenprox during prolonged exposure over multiple generations. In the transgenerational treatment, the heat shock protein 70 was up-regulated and cytochrome oxidase 6N4v1 expression down-regulated in a dose-dependent manner in the F2 generation. This finding raises the possibility of the epigenetic inheritance of insecticide impacts on parents. Furthermore, CYP6N4v1 expression was oppositely regulated in the trans- and multigenerational treatments. Our results draw attention to the differences in molecular level responses of F. candida to trans- and multigenerational etofenprox exposure.

Toxicity and uptake of nanoparticulate and bulk ZnO in nematodes with different life strategies.

Despite the increasing number and quantity of nanomaterials released in the environment, our knowledge on their bioavailability and possible toxicity to organisms is rather limited. Thus, we know quite little about sensitivity of various nematode feeding types and life strategies to treatments with nano metal oxides. The toxicity of zinc oxide nanoparticles (nano-ZnO) (with a particle size of 25 nm) and the bulk counterpart was investigated in two free-living nematode species of different life strategies: Xiphinema vuittenezi, a K-strategist plant-feeder nematode and Panagrellus redivivus, an r-strategist bacterivor nematode. The internal zinc concentration and the concentration of minor and trace elements were determined by total reflection X-ray fluorescence spectrometry. Concentration-dependent mortality in both nematode species was observed following a 24-h exposure both to nano-ZnO and bulk ZnO. The zinc concentration of the treating suspension had a significant effect on the internal zinc content of the animals in both cases. Particle size did not influence the internal zinc content. Our results show that nano and bulk ZnO have a similar dose-response effect on mortality of the bacterivor P. redivivus. In contrast, the nano-ZnO has stronger toxic effect on the mortality of X. vuittenezi. In general, X. vuittenezi did not react more sensitively to the treatments than P. redivivus, but appeared sensitive to the nano-ZnO treatment compared to bulk ZnO.