Short-term Laboratory Studies Research Articles

Does biochar mitigate rainfall-induced soil erosion? A review and meta-analysis

Biochar has emerged as a promising soil amendment for improving soil structure. Yet, its impact on rainfall-induced soil erosion varies across individual studies. To address this gap, we conducted a statistical meta-analysis of 174 paired comparisons from 45 published studies to integratedly evaluate the impacts of biochar on rainfall-induced soil erosion through biochar and soil properties, as well as experimental conditions. Overall, biochar significantly reduced soil erosion by 27.86%. The response ratio (lnRR) of biochar-induced soil erosion exhibited significant variability across different subgroups. Concerning biochar properties, a more favorable influence was observed in other sources biochar (e.g., manure and sewage sludge biochar) compared to wood based and crop waste biochar, and those produced at lower pyrolysis temperatures (< 500 °C). Increasing biochar dosage was not consistently effective. The optimal range was 0.8%–2%, resulting in a 36.07% reduction in soil erosion. Regarding the soil properties, a higher sand/clay ratio of soil significantly enhanced the performance of biochar (p < 0.0001). Specifically, an insignificant effect was observed in fine-grained soils, whereas the highest reduction of 52.97% was noted in coarse-grained soils. Moreover, long-term field experiments induced greater reductions in soil erosion with biochar (35.30%) compared to short-term laboratory studies (29.62% and 12.59%). This meta-analysis demonstrates that biochar, as a potential soil amendment, could effectively mitigate rainfall-induced soil erosion by considering a combination of soil properties along with specific biochar properties.

Are menstrual disturbances associated with an energy availability threshold? A critical review of the evidence.

Exercising women have a high prevalence of menstrual disturbances. In 2003, it was suggested that disruption in luteinizing hormone (LH) pulsatility occurs below a threshold of energy availability (EA) of 30kcal/kg lean body mass (LBM)/day. This paper is a critical review of the evidence regarding the theory that disruptions to the reproductive axis and menstrual disturbances occur below the proposed threshold. Short-term laboratory studies demonstrated that 4-5 days of an EA below 30kcal/kg LBM/day, induced with or without exercise, decreased serum triiodothyronine and LH pulse frequency, and increased LH pulse amplitude in sedentary, regularly menstruating women. Fewer studies have investigated downstream ovarian effects after long-term exposure to low EA. The Sargent Camp Study was the first randomized trial that induced luteal phase defects, delayed menses, and anovulation by causing weight loss (-4± 0.3kg) with an abrupt increase in exercise volume for two menstrual cycles. The BioEnergetics Study was a randomized controlled trial that induced varying levels of energy deficits by manipulating energy intake and expenditure for three menstrual cycles. LH pulse frequency and triiodothyronine decreased, and 57% of women developed luteal phase defects, anovulation, and/or oligomenorrhea. An EA below 30kcal/kg fat free mass/day increased the chance of experiencing a menstrual disturbance by 50%. However, menstrual disturbances were observed above and below that EA threshold, and changes in LH pulse frequency predicted only luteal phase defects, not oligomenorrhea or anovulation. The proposed EA threshold is not a cut-off below which menstrual disturbances occur, but represents an increased risk of experiencing menstrual disturbances.

Level-adaptive sound masking in the open-plan office: How does it influence noise distraction, coping, and mental health?

In the open-plan office, intelligible speech is a major distractor, reducing cognitive performance. Sound masking emits an electronic broadband sound to increase the background sound level in a controlled manner. To date, most studies on sound masking are short-term laboratory studies that do not consider aspects of mental health. The current study aims to evaluate, using a longitudinal field study with intervention (N = 42) and control (N = 41) floors at two organizations, whether level-adaptive sound masking could reduce intelligible speech and increase mental health, while being exposed to level-adaptive sound masking for two to three months. The study consists of two subjective measurements, prior- and post-intervention, using survey questions on coping strategies, noise distraction, and ten mental health indicators (short-and long-term consequences). The increase in background noise level (at company 1 from 28.7 dB(A) to 41.9 dB(A) and at company 2 from 32.4 dB(A) to 42.6 dB(A)) at both organizations significantly reduced intelligible speech distraction. Short-term mental health aspects were rated more positively, and level-adaptive sound masking also reduced the frequency with which people put on radio or headphones to cope with noise.

EFFICIENCY OF UTILIZATION OF ORGANIC SUBSTANCES PRODUCED FROM ORGANIC WASTE ON ORDINARY CHERNOZEM

The authors presented in the article the results of studying the effect of solid and liquid organic fertilisers obtained at their installation and when composting from agricultural waste on spring wheat yield and quality in a laboratory experiment on ordinary chernozems of the Orenburg region. The effectiveness of using the obtained substances as liquid and solid organic fertilisers was assessed. The authors substantiated that according to all options for studying the norms and types of organic fertilisers in the soil, the content of organic matter, ammonium nitrogen, mobile phosphorus and potassium increased. The data on the green mass of spring wheat for all research options in the laboratory experiment are given. It has been established that when liquid organic fertilisers are applied to the soil, ammonium nitrogen is highly mobile and available to plants, so plants become taller at the initial vegetation stage. The authors determined the lower efficiency of applying solid organic fertilisers in short-term laboratory studies. As a result, it has been established that 4 t/ ha for solid organic fertilisers and 8 t/ha for liquid organic fertilisers is the most effective. With such a rate of application of liquid organic fertilisers, the germination of spring wheat reaches 98.7%, and the yield of green mass of plants increases by three times compared to the control. In addition, the trend of the highest efficiency of applying liquid organic fertilisers compared to solid ones was noted.

Examining Participant Adherence with Wearables in an In-the-Wild Setting.

Wearable devices offer a wealth of data for ubiquitous computing researchers. For instance, sleep data from a wearable could be used to identify an individual's harmful habits. Recently, devices which are unobtrusive in size, setup, and maintenance are becoming commercially available. However, most data validation for these devices come from brief, short-term laboratory studies or experiments which have unrepresentative samples that are also inaccessible to most researchers. For wearables research conducted in-the-wild, the prospect of running a study has the risk of financial costs and failure. Thus, when researchers conduct in-the-wild studies, the majority of participants tend to be university students. In this paper, we present a month-long in-the-wild study with 31 Japanese adults who wore a sleep tracking device called the Oura ring. The high device usage results found in this study can be used to inform the design and deployment of longer-term mid-size in-the-wild studies.

Facilitated remediation of heavy metals contaminated land using Quercus spp. with different strategies: Variations in amendments and experiment periods

Phytoremediation using trees combined with soil amendments has gained much attention for its highly cost-effective trait. In natural field conditions, however, the results may not reflect the true performance of amendments based on short-term laboratory studies. In this three-year field trial, various soil amendments such as rice straw biochar, palygorskite, a combined biochar of rice straw biochar and palygorskite, and hydroxyapatite were used to systematically study the potential of the low-accumulator (Quercus fabri Hance) and high-accumulator (Quercus texana Buckley) for cadmium (Cd) and zinc (Zn) to remediate severely contaminated soils. Soil amendments enhanced the dendroremediation capacity of Quercus as the growth period prolonged. In 2021, the rice straw biochar treatment increased Cd and Zn accumulation by 1.76 and 2.09 times in Q. fabri, respectively, compared to the control. Cd and Zn accumulation increased to 1.78 and 2.10 times, respectively, under combined biochar treatment for Q. texana compared to the control. Metals accumulation was mainly enhanced by soil amendments through increasing the growth biomass of Q. fabri and improving the biomass and bioconcentration ability of Q. texana. Overall, soil amendments effectively improved the phytoremediation efficiency of Quercus in the long term, and selecting suitable amendments should be fully considered in phytoremediation.

Biochar as a Soil Amendment for Restraining Greenhouse Gases Emission and Improving Soil Carbon Sink: Current Situation and Ways Forward

The global exponential rise in greenhouse gas (GHG) emissions over the last few decades has triggered an urgent need to contextualize low-cost and evergreen technologies for restraining GHG production and enhancing soil carbon sink. GHGs can be mitigated via incorporating biochar into soil matrix to sequestrate the mineralized carbon in a stable form upon organic matter decomposition in soil. However, the efficiency of using biochar to offset GHG emissions from soil and terrestrial ecosystems is still debatable. Moreover, in the literature, biochar shows high functionality in restraining GHG emissions in short-term laboratory studies, but it shows minimal or negative impacts in field-scale experiments, leading to conflicting results. This paper synthesizes information on the ability of biochar to mitigate carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) emissions from soil and organic biomass, with an emphasis on cropland soils. The feedstock type, pyrolysis temperature, and application rate factors showed significant effects on controlling the effectiveness of biochar in restraining GHG emissions. Our study demonstrates that biochar, taken as a whole, can be seen as a powerful and easy-to-use tool for halting the rising tide of greenhouse gas emissions. Nonetheless, future research should focus on (i) identifying other indirect factors related to soil physicochemical characters (such as soil pH/EH and CaCO3 contents) that may control the functionality of biochar, (ii) fabricating aged biochars with low carbon and nitrogen footprints, and (iii) functionalizing biologically activated biochars to suppress CO2, CH4, and N2O emissions. Overall, our paradoxical findings highlight the urgent need to functionalize modern biochars with a high capacity to abate GHG emissions via locking up their release from soil into the carbonaceous lattice of biochar.

Uptake, transformation, and environmental impact of zinc oxide nanoparticles in a soil-wheat system.

Zinc oxide nanoparticles (ZnO-NPs) are metal-based nanomaterials, but their long-term effects on plant growth and the soil environment in the field remain unclear with most previous studies using short-term laboratory and glasshouse studies. In this study, we used a field experiment to examine the long-term effects of ZnO-NPs in a soil-wheat (Triticum aestivum) system. It was found that although ZnO-NPs had no significant effect on either yield or the concentration of other nutrients within the grain, the application of ZnO-NPs significantly increased Zn concentrations. Indeed, for grain, the application of ZnO-NPs to both the soil and foliage (SFZnO) (average of 33.1 mg/kg) significantly increased grain Zn concentrations compared to the the control treatment (21.7 mg/kg). Using in situ analyses, nutrients were found to accumulate primarily in the crease tissue and the aleurone layer of the grain, regardless of treatment. Specifically, the concentration of Zn in the aleurone layer for the SFZnO treatment was 2-3 times higher than that in the control, being >300 mg/kg, whilst the Zn concentration in the crease tissue was ca. 600 mg/kg in the SFZnO treatment, being two times higher than for the control. Although the application of ZnO-NPs increased the total Zn within the grain, it did not accumulate within the grain as ZnO-NPs with this being important for food safety, but rather mainly as Zn-phytate, with the remainder of the Zn complexed with either cysteine or phosphate. Finally, we also observed that ZnO-NPs caused fewer changes to the soil bacterial community structure and that it had no nano-specific toxicity.

Effects of slag and biochar amendments on microorganisms and fractions of soil organic carbon during flooding in a paddy field after two years in southeastern China

Incorporating amendments of industrial waste such as biochar and steel slag in cropland has been used to enhance the storage of soil organic carbon (SOC) while sustaining crop production. Short-term laboratory and field studies have identified important influences of biochar on active SOC fractions associated with soil microbial activity in paddy soils, but the long-term effects remain poorly understood. To address these knowledge gaps, we examined the effects of slag, biochar, and slag+biochar treatments on total SOC concentration, active SOC fractions and soil microbial communities in a paddy field two years after incorporation. Across both two seasons, the addition of slag, biochar, slag+biochar increased soil salinity by 26–80%, 1.3–37% and 42–79%, and also increased soil pH by 0.8–5.7%, 2.1–2.4% and 4.0–6.3%, respectively, relative to the control. SOC concentration was higher in the slag, biochar, and slag+biochar treatments across both rice seasons by 4.3–5%, 0.5–17% and 4.3–7%, respectively. Soil C-pool activity and C-pool management indices in the late paddy season were significantly lower in the slag+biochar treatment than the control by 26.3 and 21.3%, respectively, indicating that the amendments contributed to the stability of SOC. The C concentrations of the biochar and slag amendments affected bacterial abundance more than fungal abundance and affected C cycling. Our study suggests that combined slag and biochar amendments may increase bacterial abundance that may maintain SOC storage and reduce the abundances of potential SOC decomposers in key functional genera, indicating strong coupling relationships with changes of soil properties such as salinity, pH, and SOC concentration. These outcomes due to the amendments (e.g. slag+biochar) may increase microbial C-use efficiency and support the stability of active SOC fractions, with opportunities for long-term C sequestration.

Impact of climate change on soil nitric oxide and nitrous oxide emissions from typical land uses in Scotland

Soil emissions of NO and N2O from typical land uses across Lowland and Highland Scotland were simulated under climate change conditions, during a short-term laboratory study. All locations investigated were significant sources of N2O (range: 157–277 µg N2O–N m−2 h−1) and low-to-moderate sources of NO emissions (range: 0.4–30.5 µg NO–N m−2 h−1), with a general tendency to decrease with altitude and increase with fertiliser and atmospheric N inputs. Simulated climate warming and extreme events (drought, intensive rainfall) increased soil NO pulses and N2O emissions from both natural and managed ecosystems in the following order: natural Highlands < natural Lowlands < grazed grasslands < natural moorland receiving high NH3 deposition rates. Largest NO emission rates were observed from natural moorlands exposed to high NH3 deposition rates. Although soil NO emissions were much smaller (6–660 times) than those of N2O, their impact on air quality is likely to increase as combustion sources of NO x are declining as a result of successful mitigation. This study provides evidence of high N emission rates from natural ecosystems and calls for urgent action to improve existing national and intergovernmental inventories for NO and N2O, which at present do not fully account for emissions from natural soils receiving no direct anthropogenic N inputs.

Low energy availability in female athletes: From the lab to the field

ABSTRACT Decades of laboratory research have shown impairments to several body systems after only 4–5 days of strictly controlled consistent low energy availability (LEA); where energy availability (EA) = Energy Intake (EI) − Exercise Energy Expenditure (EEE)/Fat-Free Mass. Meanwhile, cross-sectional reports exist on the interrelatedness of LEA, menstrual dysfunction and impaired bone health in females (the Female Athlete Triad). These findings have demonstrated that LEA is the key underpinning factor behind a broader set of health and performance outcomes, recently termed as Relative Energy Deficiency in Sport (RED-S). There is utmost importance of early screening and diagnosis of RED-S to avoid the development of severe negative health and performance outcomes. However, a significant gap exists between short-term laboratory studies and cross-sectional reports, or clinically field-based situations, of long-term/chronic LEA and no definitive, validated diagnostic tests for RED-S exist. This review aims to highlight methodological challenges related to the assessment of the components of EA equation in the field (e.g. challenges with EI and EEE measures). Due to the uncertainty of these parameters, we propose the use of more chronic “objective” markers of LEA (i.e. blood markers). However, we note that direct extrapolations of laboratory-based outcomes into the field are likely to be problematic due to potentially poor ecological validity and the extreme variability in most athlete’s daily EI and EEE. Therefore, we provide a critical appraisal of the scientific literature, highlighting research gaps, and a potential set of leading objective RED-S markers while working in the field. Highlights Direct application of short-term laboratory-based findings in the field is problematic. Calculation of energy availability (EA) in the field is methodologically challenging and prone to errors. The use of several biomarkers may allow the detection of early exposure to low EA in the female athlete.

EMF exposure and non-specific physical symptoms

OPS 26: Radiation, EMF, cancer and mortality, Room 114, Floor 1, August 26, 2019, 4:30 PM - 5:45 PM Background/Aim: Some people attribute non-specific physical symptoms (NSPS) such as headache and fatigue to exposure to radiofrequency electromagnetic fields (RF-EMF). Most studies into exposure-response associations in electrosensitivity were short-term laboratory studies, only suitable to detect symptoms elicited by acute exposure. We will present the results from two studies with an ambulatory design using body worn exposimeters and electronic diaries that aimed to analyse exposure-response relationships in self-declared electrosensitive persons both at a group and individual level. Methods: In study 1, seven participants registered NSPS and perceived RF-EMF exposure in an electronic diary daily at three set times for a period of three weeks. During the same period personal exposure was monitored using exposimeters. A second study including 57 participants used a similar design but the study period was five days and diaries were completed at quasi-random times with 2-3 hour intervals. Associations between EMF exposure and NSPS were analysed using ARIMA and (linear) mixed models. Results: In study 1, we found statistically significant associations between perceived and actual exposure to WiFi and base stations for mobile telecommunications and NSPS scores in four participants. In two persons a higher EMF exposure was statistically significantly associated with higher symptom scores, and in two other persons it was associated with lower scores. Strengths of the associations were in the order of a 0.4 to 0.9 increase or decrease in symptom scores (on a five-point scale) for an increase of 2 standard deviations in EMF exposure. In study 2, at group level, there was no statistically significant association between EMF exposure and NSPS. Analyses at an individual level are ongoing and will be presented at the conference. Conclusions: RF-EMF exposure was associated either positively or negatively with NSPS in some but not all of the selected self-declared electrohypersensitive persons.

Long-term effects of the use of a sound masking system in open-plan offices: A field study

Noise in open-plan offices, and more specifically conversational noise, is a major source of annoyance for employees. The principle of sound masking consists in artificially increasing the background noise in the office, which leads to a decrease in speech intelligibility and therefore a reduction in acoustic annoyance. Nevertheless, the arguments in favour of this technology are based on short-term laboratory studies, whose lack of representativeness limits the application of their conclusions in real open-plan offices. This justifies the present study, which aims to evaluate, in situ and over the long term, the effectiveness of a sound masking system that meets the main scientific and normative recommendations (for example, a masking level below 45 dB(A) and a spectrum with a slope of approximately − 5 dB per octave). Such a sound masking system was installed for several months in an office of a major French banking company. The experiment spanned 26 weeks, 14 of which corresponded to nominal operation of the masking system. The protocol was based on subjective measurements using questionnaires on perceived fatigue, mental workload and perception of the soundscape. The study did not reveal any significant improvement in the assessed psychological factors nor in annoyance caused by office noise. On the contrary, it showed an increase in annoyance caused by noise from office equipment. This highlights the fact that a masking level of 45 dB(A) might already be too high. The results therefore suggest that, in real conditions, a masking system, even if it is used according to specifications that seem to be agreed upon, is not a turnkey solution to the problem of noise in open-plan offices. It is recommended that the installation of these systems be preceded by a holistic analysis of the office: acoustic quality of the room, layout of the workstations and the activities that take place there.

Using natural analogues to investigate the effects of climate change and ocean acidification on Northern ecosystems

AbstractNorthern oceans are in a state of rapid transition. Still, our knowledge of the likely effects of climate change and ocean acidification on key species in the food web, functionally important habitats and the structure of Arctic and sub-Arctic ecosystems is limited and based mainly on short-term laboratory studies on single species. This review discusses how tropical and temperate natural analogues of carbonate chemistry drivers, such as CO2 vents, have been used to further our knowledge of the sensitivity of biological systems to predicted climate change, and thus assess the capacity of different species to show long-term acclimation and adaptation to elevated levels of pCO2. Natural analogues have also provided the means to scale-up from single-species responses to community and ecosystem level responses. However, to date the application of such approaches is limited in high latitude systems. A range of Arctic and sub-Arctic sites, including CO2 vents, methane cold seeps, estuaries, up-welling areas, and polar fronts, that encompass gradients of pH, carbonate saturation state, and alkalinity, are suggested for future high latitude, in-situ ocean acidification research. It is recommended that combinations of monitoring of the chemical oceanography, observational, and experimental (in situ and laboratory) studies of organisms around these natural analogues be used to attain better predictions of the impacts of ocean acidification and climate change on high latitude species and ecosystems.

No evidence of increased growth or mortality in fish exposed to oxazepam in semi-natural ecosystems

An increasing number of short-term laboratory studies on fish reports behavioral effects from exposure to aquatic contaminants or raised carbon dioxide levels affecting the GABAA receptor. However, how such GABAergic behavioral modifications (GBMs) impact populations in more complex natural systems is not known. In this study, we induced GBMs in European perch (Perca fluviatilis) via exposure to a GABA agonist (oxazepam) and followed the effects on growth and survival over one summer (70days) in replicated pond ecosystems. We hypothesized that anticipated GBMs, expressed as anti-anxiety like behaviors (higher activity and boldness levels), that increase feeding rates in laboratory assays, would; i) increase growth and ii) increase mortality from predation. To test our hypotheses, 480 PIT tagged perch of known individual weights, and 12 predators (northern pike, Esox lucius) were evenly distributed in 12 ponds; six control (no oxazepam) and six spiked (15.5±4μgl−1 oxazepam [mean±1S.E.]) ponds. Contrary to our hypotheses, even though perch grew on average 16% more when exposed to oxazepam, we found no significant difference between exposed and control fish in growth (exposed: 3.9±1.2g, control: 2.9±1g [mean±1S.E.], respectively) or mortality (exposed: 26.5±1.8individuals pond−1, control: 24.5±2.6individuals pond−1, respectively). In addition, we show that reduced prey capture efficiency in exposed pike may explain the lack of significant differences in predation. Hence, our results suggest that GBMs, which in laboratory studies impact fish behavior, and subsequently also feeding rates, do not seem to generate strong effects on growth and predation-risk in more complex and resource limited natural environments.

Impacts of neonicotinoid use on long-term population changes in wild bees in England.

Wild bee declines have been ascribed in part to neonicotinoid insecticides. While short-term laboratory studies on commercially bred species (principally honeybees and bumblebees) have identified sub-lethal effects, there is no strong evidence linking these insecticides to losses of the majority of wild bee species. We relate 18 years of UK national wild bee distribution data for 62 species to amounts of neonicotinoid use in oilseed rape. Using a multi-species dynamic Bayesian occupancy analysis, we find evidence of increased population extinction rates in response to neonicotinoid seed treatment use on oilseed rape. Species foraging on oilseed rape benefit from the cover of this crop, but were on average three times more negatively affected by exposure to neonicotinoids than non-crop foragers. Our results suggest that sub-lethal effects of neonicotinoids could scale up to cause losses of bee biodiversity. Restrictions on neonicotinoid use may reduce population declines.

Salisbury biochar did not affect the mobility or speciation of lead in kaolin in a short-term laboratory study

Salisbury biochar (produced from British broadleaf hardwood) with two different particle sizes (≤2mm and ≤0.15mm) was applied on a kaolin with three different lead (Pb2+) contamination levels (50mg/kg, 300mg/kg and 1000mg/kg) at the dosage of 1% in w/w. The short-term impact of biochar on the mobility and speciation of Pb2+ in the kaolin was investigated using attenuation periods of 1, 7 and 28 days. The leachability and extractability of Pb2+ in carbonic acid leaching and EDTA extraction tests as well as the speciation of Pb2+ in soils were not significantly affected by biochar treatment during all periods. The insignificant effects of biochar on Pb2+ immobilisation were most likely attributed to the high adsorption capacity of Pb2+ on the kaolin and biochar failed to competitively adsorb Pb2+ against kaolin. The kaolin immobilised Pb2+ primarily through cation exchange, which represents the readily bioavailable fractions of Pb2+ in soils and may still pose environmental risks. This paper suggests the inefficiency of biochar treament on heavy-metal contaminated clay-rich soils. Therefore a laboratory treatablity study with respect to the soil type may be crucial when large-scale biochar applications in heavy-metal associated soil remediation are evaluated.

Effects of long-term manure applications on the occurrence of antibiotics and antibiotic resistance genes (ARGs) in paddy soils: Evidence from four field experiments in south of China

Most studies of the effects of manure amendment on the occurrence of antibiotics and antibiotic resistance genes (ARGs) in soil employ the investigation of grab samples or short-term laboratory studies. However, the effects of long-term manure applications on antibiotics, ARGs and their vertical distribution in paddy soil in field experiments are lacking. We assessed the concentrations of antibiotics, ARGs and their vertical distribution in paddy soil receiving long-term manure applications in four field experiments. High concentrations of tetracyclines were detected in most manured soils, while sulfonamides were not detectable. Long-term manure amendments generally increased the antibiotic concentrations and ARGs abundances in the paddy soil over decades. However, in some sites such significant trends of ARGs could not be observed. The abundance of ARGs was statistically correlated with antibiotics and soil properties including pH and soil organic matter (SOM), indicating their importance in the selection of resistance genes. Tetracyclines could be detected in soil at different depths and the concentrations of tetracyclines and abundance of ARGs generally decreased with increasing soil depths.

Climate change triggers effects of fungal pathogens and insect herbivores on litter decomposition

Increasing infestation by insect herbivores and pathogenic fungi in response to climate change will inevitably impact the amount and quality of leaf litter inputs into the soil. However, little is known on the interactive effect of infestation severity and climate change on litter decomposition, and no such study has been published for deciduous forests in Central Europe. We assessed changes in initial chemical quality of beech (Fagus sylvatica L.) and maple litter (Acer platanoides L.) in response to infestation by the gall midge Mikiola fagi Hart. and the pathogenic fungus Sawadaea tulasnei Fuckel, respectively, and investigated interactive effects of infestation severity, changes in temperature and soil moisture on carbon mineralization in a short-term laboratory study. We found that infestation by the gall midge M. fagi and the pathogenic fungus S. tulasnei significantly changed the chemical quality of beech and maple litter. Changes in element concentrations were generally positive and more pronounced, and if negative less pronounced for maple than beech litter most likely due to high quality fungal tissue remaining on litter after abscission. More importantly, alterations in litter chemical quality did not translate to distinct patterns of carbon mineralization at ambient conditions, but even low amounts of infested litter accelerated carbon mineralization at moderately increased soil moisture and in particular at higher temperature. Our results indicate that insect herbivores and fungal pathogens can markedly alter initial litter chemical quality, but that afterlife effects on carbon mineralization depend on soil moisture and temperature, suggesting that increased infestation severity under projected climate change potentially increases soil carbon release in deciduous forests in Central Europe.

C mineralization and microbial activity in four biochar field experiments several years after incorporation

Most studies looking into the effect of amendment of biochar on soil microbial functioning employ short-term laboratory studies and probably describe relatively transient phenomena. Multi-year experiments, spanning beyond initial degradation of biologically labile biochar constituents, on the other hand are more scarce, although these are much needed to establish the medium-term effect of biochar on soil organisms. In the present study, soil was sampled from biochar-amended and control plots of four biochar field trials at Lincoln (UK), Rivignano, Rocca Bernarda and Beano in Italy. Air-dried pre-incubated soil samples were incubated at 15 °C for 8–9 weeks to follow-up carbon dioxide (CO2) emissions. We then determined soil β-glucosidase and dehydrogenase enzyme activity, and used PLFA analysis to quantify the total soil microbial biomass and community structure. The analysis indicated that soil microbial activity was either not affected or inhibited to different extents in the biochar-amended plots. At Lincoln, with the highest application rate (49 t ha−1), an overall inhibition of all investigated measures of microbial activity, a lower sum of extracted PLFAs and lower fungal abundance were observed. On the other end at Beano, depth dispersion of biochar by deep tillage and a lower application rate (20 t ha−1) probably explain the absence of any significant effect on microbial activity in that experiment. At Rivignano and Rocca Bernarda, dehydrogenase activity was lower in the biochar amended soil and C-mineralization was lower as well for Rivignano. Interestingly, however, β-glucosidase activity and the sum of extracted PLFAs was not affected by biochar treatment. Several mechanisms could reconcile the different effect of biochar application on overall microbial activity on the one hand and microbial abundance and rate of cellulose degradation on the other. Biochar amendment led to a lowered or equal soil microbial activity and abundance in most field sites. In contrast to many short-term laboratory studies, it therefore seems unlikely that biochar would still function as a substrate 1–4 years after incorporation in the field.