Biotic Effects Research Articles

Fagus sylvatica seedlings show provenance differentiation rather than adaptation to soil in a transplant experiment

BackgroundUnderstanding and predicting the response of tree populations to climate change requires understanding the pattern and scale of their adaptation. Climate is often considered the major driver of local adaptation but, although biotic factors such as soil pathogens or mutualists could be as important, their role has typically been neglected. Biotic drivers might also interact with climate to affect performance and mycorrhizae, in particular, are likely to play a key role in determining drought resistance, which is important in the context of adaptation to future environmental change. To address these questions, we performed a fully reciprocal soil–plant transplant experiment using Fagus sylvatica seedlings and soils from three regions in Germany. To separate the biotic and abiotic effects of inoculation, half of the plants were inoculated with natural soil from the different origins, while the rest were grown on sterilized substrate. We also imposed a drought stress treatment to test for interactions between soil biota and climate. After 1 year of growth, we measured aboveground biomass of all seedlings, and quantified mycorrhizal colonization for a subset of the seedlings, which included all soil–plant combinations, to disentangle the effect of mycorrhiza from other agents.ResultsWe found that plant origin had the strongest effect on plant performance, but this interacted with soil origin. In general, trees showed a slight tendency to produce less aboveground biomass on local soils, suggesting soil antagonists could be causing trees to be maladapted to their local soils. Consistently, we found lower mycorrhizal colonization rate under local soil conditions. Across all soils, seedlings from low elevations produced more annual biomass than middle (+ 290%) and high (+ 97%) elevations. Interestingly, mycorrhizal colonization increased with drought in the two provenances that showed higher drought tolerance, which supports previous results showing that mycorrhizae can increase drought resistance.ConclusionsOur findings suggest that soil communities play a role in affecting early performance of temperate trees, although this role may be smaller than that of seed origin. Also, other effects, such as the positive response to generalists or negative interactions with soil biota may be as important as the highly specialized mycorrhizal associations.

Zooplankton grazing pressure is insufficient for primary producer control under elevated warming and nutrient levels

Within a given ecosystem, species persistence is driven by responses to the effects of biotic and abiotic stressors. Ongoing climatic shifts and increased pollution pressure have created the need to assess potential effects and interactions of physical and biotic factors on coastal ecosystem processes to project ecosystem resilience and persistence. In coastal marine environments, primary production dynamics are driven by the interaction between bottom-up abiotic effects and biotic effects induced by top-down trophic control. Given the many environmental and climatic changes observed throughout coastal regions, we assessed the effects of interactions among temperature, nutrients and grazing in a laboratory-based microcosm experiment. We did this by comparing chlorophyll-a (chl-a) concentrations at two temperatures in combination with four nutrient regimes. To test for subsequent cascading effects on higher trophic levels, we also measured grazing and growth rates of the calanoid copepod Pseudodiaptomus hessei. We observed different phytoplankton and zooplankton responses to temperature (17 °C, 24 °C) and nutrients (nitrogen only (N), phosphates only (P), nitrogen and phosphates combined (NP), no nutrient additions (C)). Contributions of predictors to model fit in the boosted regression trees model were phosphates (42.7%), copepods (23.8%), nitrates (17.5%) and temperature (15.9%), suggesting phosphates were an important driver for the high chl-a concentrations observed. There was an increase in total phytoplankton biomass across both temperatures, while nutrient addition affected the phytoplankton size structure prior to grazing irrespective of temperature. Phytoplankton biomass was highest in the NP treatment followed by the N treatment. However, the phytoplankton size structure differed between temperatures, with microphytoplankton being dominant at 24 °C, while nanophytoplankton dominated at 17 °C. The P and C treatments exhibited the lowest phytoplankton biomass. Copepod abundances and growth rates were higher at 17 °C than at 24 °C. This study highlights that bottom-up positive effects in one trophic level do not always positively cascade into another trophic level. It was, however, evident that temperature was a limiting factor for plankton abundance, productivity and size structure only when nutrients were limiting, with top-down pressure exhibiting minimal effects on the phytoplankton.

Forest seedling community response to understorey filtering by tree ferns

AbstractQuestionsLarge pteridophytes frequently co‐occur with conifers and angiosperms in the understorey of temperate broad‐leaved podocarp forests but interactions between them are poorly understood. We evaluated the impact of tree ferns on the regeneration niche of vascular woody species to determine whether tree ferns function as biotic filters and influence seedling occurrence. We asked the following questions: (i) do understorey tree ferns influence the woody seedling bank, and (ii) which potential mechanisms drive any such influence?LocationAuckland and Waikato regions, northern New Zealand.MethodsWe measured woody seedlings in 164 1‐m2 plots in northern New Zealand temperate broad‐leaved podocarp forest and used multivariate analyses and modelling to assess the relative contributions of abiotic and biotic effects on community composition and seedling abundance. We manipulated the environments beneath 160 tree fern individuals by removing fronds and/or macro‐litter in a balanced factorial design, and recorded the response of the seedling community over 1 year. We then assessed the relative influences of shading and litter depth on the seedling community response.ResultsDistance to the nearest tree fern was the best predictor of understorey seedling abundance; seedling abundance decreased beneath tree ferns. There was no strong evidence, however, that tree ferns influence seedling community composition; although the palm Rhopalostylis sapida, was consistently present away from tree fern micro‐sites. Removal of tree fern shading and macro‐litter both influenced the local seedling community; conifers responded positively, and most consistently to frond removal. Frond‐shading and deep litter reduced seedling species richness and seedling abundance.ConclusionsTree ferns influence the woody seedling bank in temperate broad‐leaved podocarp forest through increased shading and macro‐litter accumulation, both of which reduce the abundance of angiosperm and conifer seedlings. A tree fern‐dominated understorey is likely to reduce conifer establishment and may limit direct competition among woody plants by reducing densities and regeneration opportunities immediately beneath tree fern canopies.

How species colonize gaps after soil disturbance in temporary ponds? Implication of species traits

AbstractThis work aims to review the existing theoretical literature and experiments on plant species colonising gaps after soil disturbance. It attempts to evaluate the various mechanisms by which plants regenerate among the soil openings within the Mediterranean temporary ponds. Intensity and frequency of disturbances are key factors in the response of communities. Knowing the specificity of plant strategies and the species assembly process is important for a better understanding of the impact of soil disturbance on the structure of temporary ponds community, and their mechanisms of resilience. Under the scope of these mechanisms, we will assess the contribution of seed bank by regrowth of buried seeds, vegetative propagules growth via clonal propagation and dispersion of propagules. Soil disturbance has a biotic effect on competition giving a chance to competitively inferior species.

Analysis of the Spatial Variability of Soil Texture in a Tropical Highland: The Case of the Jema Watershed, Northwestern Highlands of Ethiopia.

This study sought to analyze the degree of spatial association of soil texture with agro-climatic zones and slope classes on the farmlands of the Jema watershed, in the Northwestern Highlands of Ethiopia. The agro-climatic zones (elevation zones) determine the micro-climate and biota of the study area. Thirty six soil composite samples for texture (the proportion of clay, silt and sand) analysis from four agro-climatic (elevation) zones and seven slope classes were collected. One-Way-ANOVA was employed to compute the mean variability of texture among the identified terrain classes, and linear regression was used to analyze the degree of association between texture and the terrain attributes. The measured values of sand, silt and clay in the watershed ranged from 11.4 to 43.4, 6.0 to 34.8, and 21.8 to 77.8, respectively. The One-Way-ANOVA indicated a significant (p < 0.05) soil texture variation in both slope and agro-climatic zone classes. Heavy clay, clay and clay loam were identified as the major texture classes in the lower, middle and upper parts of the watershed, respectively. The regression analysis showed that texture was more influenced by the difference in the elevation values than in slope values in the watershed. The standardized beta coefficients of slope and elevation for clay particles were 0.499 and 0.767, respectively. For sand, the regression coefficients for slope and agro-climatic zone were 0.485 and 0.812, respectively. This implies that an interactive effect of micro-climate and biota governed by elevation influenced the spatial distribution of soil texture more than slope.

Ecosystem context illuminates conflicting roles of plant diversity in carbon storage.

Plant diversity can increase biomass production in plot-scale studies, but applying these results to ecosystem carbon (C) storage at larger spatial and temporal scales remains problematic. Other ecosystem controls interact with diversity and plant production, and may influence soil pools differently from plant pools. We integrated diversity with the state-factor framework, which identifies key controls, or 'state factors', over ecosystem properties and services such as C storage. We used this framework to assess the effects of diversity, plant traits and state factors (climate, topography, time) on live tree, standing dead, organic horizon and total C in Québec forests. Four patterns emerged: (1) while state factors were usually the most important model predictors, models with both state and biotic factors (mean plant traits and diversity) better predicted C pools; (2) mean plant traits were better predictors than diversity; (3) diversity increased live tree C but reduced organic horizon C; (4) different C pools responded to different traits and diversity metrics. These results suggest that, where ecosystem properties result from multiple processes, no simple relationship may exist with any one organismal factor. Integrating biodiversity into ecosystem ecology and assessing both traits and diversity improves our mechanistic understanding of biotic effects on ecosystems.

Fungal Frequency and Mite Load Trends Interact with a Declining Mountain Pine Beetle Population

The mite and fungal biota associated with the mountain pine beetle (MPB) (Dendroctonus ponderosae Hopk.) may not be stable throughout an irruptive event. In congeneric beetles, variations in the frequency of their associated organisms affect population trends and similar effects may occur in MPB. We studied fungi and mite trends in a declining irruptive MPB population as it attacked three different pine hosts in the Colorado Front Range. During the study, we found two new associates including one biologically relevant mite and one beneficial blue-stain fungus. Fungi hyperphoretic on mites were also documented. This included beneficial and potentially detrimental species to the MPB. The frequency of several organisms varied between some years or pine hosts but not within male or female beetles. A large increase of Trichouropoda sp. and T. ips mites trended inversely with the declining beetle population, while a decrease in the beneficial blue-stain fungi trended similarly to the declining beetle population. We discuss the interactions and potential effects of phoretic biota in relation to (1) the MPB associates’ population trends, (2) the MPB incursions into cooler areas, and (3) the redundancy of blue-stain fungi carried by the MPB holobiont. These findings increase our knowledge of the mechanisms that influence MPB populations.

Causes of inhibition of bioleaching by Cu are also thermodynamic

AbstractBACKGROUNDCu is an indispensable natural resource for society, as its use is widespread and essential for many technologies. Consequently, worldwide production is around 18×106 tn year−1, and close to 25% is produced by bioleaching. Bioleaching enables Cu extraction from minerals in atmospheric conditions by virtue of the catalytic activity of microorganisms. Microbial catalysis is mainly based on Fe3+ production as a leaching agent, a process known as Fe2+ bio‐oxidation. However, bio‐oxidation is inhibited by Cu2+ which limits the use of bioleaching with Cu mineral ores.RESULTSThis paper, for the first time, examines the effect of Cu2+ on continuous Fe2+ bio‐oxidation using a packed bed bioreactor with supported cells. Bio‐oxidation was possible in the presence of 20 g L−1 Cu2+, with a less than 25% reduction in rate. About 15% of this drop in rate is due to biological inhibition and the rest to a reduction in oxygen solubility because of salting‐out. The biotic effect is reversed when Cu2+ is removed from the input, and the salting‐out effect can be overcome by improving aeration conditions.CONCLUSIONThese results, apart from having important ramifications for designing Cu ore bioleaching facilities, contribute to a more versatile and competitive idea of this clean technology. © 2018 Society of Chemical Industry

A contribution of nanoscale particles of road-deposited sediments to the pollution of urban runoff by heavy metals

Road-deposited sediments (RDS) present a sink for traffic-related pollutants including heavy metals (HMs). HMs associated with RDS particles enter the urban aquatic environment during rainfall events and have adverse effects for biota. RDS nanoscale particles (NSPs) require special consideration due to their specific properties, extremely high mobility in the environment, and ability to penetrate into living organisms. In the present work, the contribution of NSPs of RDS to the pollution of urban runoff by HMs has been evaluated for the first time. It has been shown that bulk RDS samples are polluted by HMs as compared to background urban soils (geo-accumulation indexes of Cu and Zn may attain 2-3). Meanwhile, NSPs of RDS are enriched by HMs as compared to bulk samples; concentration factor for Ni, Cu, Zn, Cd, Sn, and Pb in NSPs being varied from 2 to 10. The water-soluble fractions of RDS samples were also analyzed. Results have shown that the content of water-soluble HMs in RDS is insignificant and rarely exceeds 0.5% of the total contents of HMs in the bulk samples; the highest contents are identified for Cu and Pb. It should be noted that the water-soluble fraction is nearly free from Zn and this element is almost entirely present as particulate matter (NSPs). In general, the overall contribution of NSPs and water-soluble fraction of HMs to the pollution of urban runoff is comparable.

Radiosensitivity and transgenerational effects in non-human species.

The ALLIANCE working group on effects of ionising radiation on wildlife brings together European researchers to work on the topics of radiosensitivity and transgenerational effects in non-human biota. Differences in radiation sensitivity across species and phyla are poorly understood, but have important implications for understanding the overall effects of radiation and for radiation protection; for example, sensitive species may require special attention in monitoring and radiation protection, and differences in sensitivity between species also lead to overall effects at higher levels (community, ecosystem), since interactions between species can be altered. Hence, understanding the mechanisms of interspecies radiation sensitivity differences may help to clarify mechanisms underpinning intraspecies variation. Differences in sensitivity may only be revealed when organisms are exposed to ionising radiation over several generations. This issue of potential long-term or hereditary effects for both humans and wildlife exposed to low doses of ionising radiation is a major concern. Animal and plant studies suggest that gamma irradiation can lead to observable effects in the F1 generation that are not attributable to inheritance of a rare stable DNA mutation. Several studies have provided evidence of an increase in genomic instability detected in germ or somatic cells of F1 organisms from exposed F0 organisms. This can lead to induced radiosensitivity, and can result in phenotypic effects or lead to reproductive effects and teratogenesis. In particular, studies have been conducted to understand the possible role of epigenetic modifications, such as DNA methylation, histone modifications, or expression of non-coding RNAs in radiosensitivity, as well as in adaptation effects. As such, research using biological models in which the relative contribution of genetic and epigenetic processes can be elucidated is highly valuable.

Frontiers of monoclonal antibodies: Applications in medical practices.

With the flourishing of innovation in drug discovery into a new era of personalized therapy, the use of monoclonal antibodies (mAbs) in the treatment of various ailments lies at the forefront. Major improvements in genetic sequencing and biomedical techniques as well as research into mAbs emphasize on determining new targets for advanced therapy while maximizing efficacy for clinical application. However, a balance has to be achieved concerning developing a target with low toxicity combined with high specificity and versatility, to allow a specific antibody to facilitate several biotic effects, ranging from neutralization of virus mechanisms to modulation of immune response and maintaining low global economic cost. Presently, there are approximately 30 mAbs' permitted for therapeutic use with many more being tested in clinical trials. Nevertheless, the heavy cost of mAbs' production, stowage and management as well as the subsequent hindrances to their development are outweighed by mAbs' clinical advantages. Compared to conventional drugs, since mAbs use as pharmacologic iotas have specific physical features and modes of action, they should be considered as a discrete therapeutic category. In this review, the history of mAb generation and the innovative technological applications of mAbs that has advanced in clinical practices is reviewed.

Sediment quality assessment in a coastal lagoon (Ravenna, NE Italy) based on SEM-AVS and sequential extraction procedure

Sediments from the Pialassa Piomboni coastal lagoon (NE Italy) were studied to assess the degree of contamination and ecological risk related to trace metals by combining a geochemical characterization of bulk sediments with the assessment of the bioavailable forms of trace metals. With this purpose, sediment contamination (Cd, Cu, Hg, Ni, Pb, and Zn) was assessed by Enrichment Factors (EFs), and potential bioavailability by the Simultaneously Extracted Metals and Acid Volatile Sulfides (SEM-AVS) approach (Cd, Cu, Ni, Pb, and Zn), and by Sequential Extraction Procedure (Co, Cr, Cu, Ni, Pb, and Zn). On average, Cr and Ni exhibited no contamination (EF ≤1.5), and a predominance in the residual fraction of the sediment, indicating natural origin for these metals. Cu, Pb and Zn displayed a local contamination, which resulted in a higher proportion of Cu bound to the reducible and oxidizable fractions (~30% and ~40% as median, respectively), and Pb mostly associated with the reducible phase (~60% as median). Hence, Cu and Pb could be mobilized when environmental conditions become reducing or oxidizing. Zn resulted mainly partitioned into the reducible and residual fractions (~50% as median, in both fractions). The Risk Assessment Code (RAC) indicated that approximately 30% of samples had >10% of total Zn weakly bound to the sediment, suggesting a medium risk of exposure for aquatic organisms. RAC results were consistent with the ∑SEM-AVS findings, pointing to possible adverse effects for aquatic biota in ~30% of samples, with Zn mostly accounting for the total metal bioavailability. Hg showed a moderate to very severe enrichment, indicating that a substantial amount of this metal derives from anthropogenic sources and may pose adverse effects on the aquatic biota of the Pialassa Piomboni lagoon.

Support media can steer methanogenesis in the presence of phenol through biotic and abiotic effects

A wide variety of inhibitors can induce anaerobic digester disruption. To avoid performance losses, support media can be used to mitigate inhibitions. However, distinguishing the physico-chemical from the biological mechanisms of such strategies remains delicate. In this framework, the impact of 10 g/L of different types of zeolites and activated carbons (AC) on microbial community dynamics during anaerobic digestion of biowaste in the presence of 1.3 g/L of phenol was evaluated with 16 S rRNA gene sequencing. In the presence of AC, methanogenesis inhibition was rapidly removed due to a decrease of phenol concentration. This abiotic effect related to the physico-chemical properties of AC led to increased final CH4 and CO2 productions by 29–31% compared to digesters incubated without support. Interestingly, although zeolite did not adsorb phenol, final CH4 and CO2 production reached comparable levels as with AC. Nevertheless, compared to digesters incubated without support, methanogenesis lag phase duration was less reduced in the presence of zeolites (5 ± 1 days) than in the presence of activated carbons (12 ± 2 days). Both types of support induced biotic effects. AC and zeolite both allowed the preservation of the major representative archaeal genus of the non-inhibited ecosystem, Methanosarcina. By contrast, they distinctly shaped bacterial populations. OTUs belonging to class W5 became dominant at the expense of OTUs assigned to orders Clostridiales, Bacteroidales and Anaerolinales in the presence of AC. Zeolite enhanced the implantation of OTUs assigned to bacterial phylum Cloacimonetes. This study highlighted that supports can induce biotic and abiotic effects within digesters inhibited with phenol, showing potentialities to enhance anaerobic digestion stability under disrupting conditions.

Environmental instability during the latest Paleocene at Zumaia (Basque-Cantabric Basin): The bellwether of the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene transition is well represented in the bathyal Zumaia section (Basque-Cantabric Basin, Northern Spain), where numerous studies have documented the sedimentological, environmental and biotic effects of the Paleocene-Eocene Thermal Maximum (PETM). The extinction of more than half of the species of deep-sea benthic foraminifera has been previously reported, but the triggering causes and the exact sequence of events leading the to the extinction event still remain uncertain. The combined study of benthic foraminifera and geochemical proxies allowed us to assess the consequences of an extreme, global warming event, and to investigate its environmental precursors, with special attention to the analysis of the uppermost Paleocene.Geochemical and micropaleontological data indicate that environmental instability started ~42.6 kyr before the onset of the carbon isotope excursion (CIE) that officially marks the Paleocene/Eocene boundary. Perturbations during the late Paleocene include fluctuations in trophic and redox conditions, as well as in detrital input. Previous studies on calcareous nannofossils suggest that early warming started during the last ~18.8–12 kyr of the Paleocene. The gradual but rapid disappearance of benthic foraminifera reveals significant environmental stress during the last ~12 kyr of the Paleocene, and the main phase of extinction of benthic foraminifera coincided with the onset of the negative CIE. The gradual onset of the extinction is recorded across an interval with high % CaCO3 content, suggesting that carbonate corrosiveness was not the main trigger of the extinctions. Geochemical and micropaleontological data point to oligotrophy and increased temperatures in surface waters prior to the onset of the CIE. The increasing food demand of benthic foraminifera due to accelerated metabolic rates at higher temperatures was exacerbated by more oligotrophic conditions during the last ~12 kyr of the Paleocene, possibly triggering the gradual but rapid extinction, which culminated during the onset of the CIE, when carbonate dissolution was pervasive at Zumaia. Dilution of carbonate-rich material by terrigenous matter, combined with effects of dissolution, resulted in a very low % CaCO3 content in the lowermost 350 cm of the Eocene. The environmental changes observed during the late Paleocene are the bellwether of the PETM, and are in line with the early warming recorded prior to the PETM at other locations.

Community-based biotic effects as determinants of tree resistance to pests and pathogens

Abstract In the light of the global increase in forest pests and diseases, accompanied by withdrawal of chemical pesticides and fungicides, we review recent advances in how forest tree resistance to pests and diseases might be influenced by manipulation of characteristics of the trees’ community of associated plants and other organisms. These include associational resistance (AR), effected by manipulation of tree species composition or richness, genotypic diversity, or by tree density/frequency of resistant species or genotypes, use of hybrids, and strategic use of bacterial and fungal symbionts to engender systemic induced resistance, or defense priming. Due to the rotation times in forest production systems, none of the community-based actions that attempt to disrupt a tree-pest or tree-pathogen interaction, can be used in a rapidly mobilised targeted response to currently known pests or pathogens or to unknown ones that are yet to emerge. The only exception is the possible use of non-pathogenic or mutualistic organisms to induce systemic resistance or prime tree defence systems against attack. Due to the range of permutations of participating species and assemblages and the idiosyncratic nature of their ecological interactions and processes, it is not currently possible to formulate predictive rules to protect forests using only these community-based methods. It is however possible to use them as part of a long-term prophylactic strategy by structuring future forests to increase their general resistance, and reduce the probability of impacts of pests and diseases, e.g. via diversification of tree species and genotypes.

P-Coumaric can alter the composition of cucumber rhizosphere microbial communities and induce negative plant-microbial interactions

Phenolics from root exudates or decaying residues are usually referred as autotoxins of several plant species. However, how phenolics affect soil microbial communities and their functional significances are poorly understood. Rhizosphere bacterial and fungal communities from cucumber (Cucumis sativus L.) seedlings treated with p-coumaric acid, an autotoxin of cucumber, were analyzed by high-throughput sequencing of 16S rRNA gene and internal transcribed spacer amplicons. Then, feedback effects of the rhizosphere biota on cucumber seedlings were evaluated by inoculating non-sterilized and sterilized rhizosphere soils to sterilized background soils. p-Coumaric acid decreased the bacterial diversity of rhizosphere but increased fungal diversity and altered the compositions of both the bacterial and fungal communities. p-Coumaric acid increased the relative abundances of microbial taxa with phenol-degrading capability (such as Chaetomium, Humicola, and Mortierella spp.) and microbial taxa which contained plant pathogens (such as Fusarium spp.). However, p-coumaric acid inhibited the relative abundances of Lysobacter, Haliangium, and Gymnoascus spp., whose species can have pathogen-antagonistic and/or plant-growth-promoting effects. The positive effect of cucumber rhizosphere microbiota on cucumber seedling growth was reduced by p-coumaric acid. Overall, our results showed that, besides its direct phytotoxicity, p-coumaric acid can inhibit cucumber seedling growth through generating negative plant-soil microbial interactions.

Biotic effects during the settlement process of non-indigenous species in marine benthic communities

Biotic effects during the settlement process of non-indigenous species in marine benthic communities

Trophic predator-prey relationships promote transport of microplastics compared with the single Hypoaspis aculeifer and Folsomia candida.

Although the roles of earthworms and soil collembolans in the transport of microplastics have been studied previously, the effects of the soil biota at different trophic levels and interspecific relationships remain poorly understood. Here, we examine three soil microarthropod species to explore their effects on the transport of microplastics. The selected Folsomia candida and Hypoaspis aculeifer are extensively used model organisms, and Damaeus exspinosus is a common and abundant indigenous species in China. A model food chain (prey-collembolan and predator-mite) was structured to test the role of the predator-prey relationship in the transport of microplastics. Commercial Polyvinyl chloride (PVC) particles (Diameter: 80-250 μm) were selected as the test microplastics, because large amounts of PVC have persisted and accumulated in the environment. Synchronized soil microarthropods were held in plates for seven days to determine the movement of microplastics. The 5000 microplastic particles were carefully placed in the center of each plate prior to the introduction of the animals. Our results clearly show that all three microarthropod species moved and dispersed the microplastics in the plates. The 0.54%, 1.8% and 4.6% of the added microplastic particles were moved by collembolan, predatory mite and oribatid mite, respectively. Soil microarthropods (<0.2 cm) transported microplastic particles up to 9 cm. The avoidance behavior was observed in the collembolans in respect of the microplastics. The predatory -prey relationship did promote the transport of microplastics in the plates, increasing transport by 40% compared with the effects of adding single species (P < .05). Soil microarthropods commonly occur in surface soils (0-5 cm) and, due to their small body size, they can enter soil pores. Our results therefore suggest that the movement of microplastics by soil microarthropods may influence the exposure of other soil biota to microplastics and change the physical properties of soils.

Temperate forest dynamics and climate

Forest Ecology![Figure][1] Temperate forest composition and disturbance regimes may shift during climate change, with consequences for the climate system. PHOTO: HERBERT KRATKY/IMAGE BROKER/AURORA PHOTOS Climate change affects biota, and biotic effects feed into the climate system. In a modeling study, Thom et al. investigated how the present cooling effect of temperate forest on local climate might change over the next 200 years as climate warming shifts the patterns of forest disturbance. Their model, applied to temperate forest in Austria, indicates marked nonlinear changes in tree species composition and disturbance regimes over time, with potential reductions in the climate regulation function of the forest. The results also indicate how the composition of these forests might best be managed to achieve optimal levels of carbon storage, evaporative cooling, and albedo to mitigate climate change. Ecol. Monogr. 10.1002/ecm.1272 (2017). [1]: pending:yes

Beyond biomass: Soil feedbacks are transient over plant life stages and alter fitness

Abstract Plants influence associated soil biotic communities that in turn can alter the performance of the subsequently growing plants. Although such “plant–soil feedbacks” (PSFs) are considered as important drivers of plant community assembly, past PSF studies have mainly addressed plant biomass production. However, plant performance is not only the production of biomass but comprises a sequence of different life stages: from seed germination over vegetative growth up to the production of a viable progeny. Here, we assessed the effects of soil biotic communities that were previously conditioned for 3 years by a focal plant species monoculture or species mixtures on key plant life stages from germination and vegetative growth to flowering and the production of viable seeds. We used three common grassland herb species that were grown in a sterile substrate and inoculated with a sterile control soil or with living soils. Living soils were conditioned either by the focal species in monoculture or a four‐ or eight‐species mixture that included the focal species to represent a decrease in the target plants’ conspecific influence on the soil communities. We show that the effect of soil biota changed from positive at the plants’ juvenile life stages to neutral or negative at the plants’ adult life stages and ultimately decreased plant fitness. A higher conspecific influence on the soil communities pronounced the positive effects at the juvenile life stage but also the negative effects at adult life stages. Further, we observed direct soil biotic effects on flower production and plant fitness that were not mediated by adult biomass production. This suggests that soil biotic effects may alter plant resource allocation and even may have transgenerational effects on plant fitness. Synthesis. We conclude that there is no overarching effect of soil biota that remains consistent at all the life stages of a plant. Thus, our results highlight the importance to consider plant life stage and ultimately plant fitness especially when plant–soil interactions are used to explain plant community dynamics.