Soil nitrogen mineralisation (N
), the conversion of organic into inorganic N, is important for productivity and nutrient cycling. The balance between mineralisation and immobilisation (net N
) ...varies with soil properties and climate. However, because most global-scale assessments of net N
are laboratory-based, its regulation under field-conditions and implications for real-world soil functioning remain uncertain. Here, we explore the drivers of realised (field) and potential (laboratory) soil net N
across 30 grasslands worldwide. We find that realised N
is largely explained by temperature of the wettest quarter, microbial biomass, clay content and bulk density. Potential N
only weakly correlates with realised N
, but contributes to explain realised net N
when combined with soil and climatic variables. We provide novel insights of global realised soil net N
and show that potential soil net N
data available in the literature could be parameterised with soil and climate data to better predict realised N
.
•Biochar effects in mixed perennial communities are largely unknown.•We compared prairie development following 3 biochar and 2 manure treatments.•Biochar increased species richness and aboveground ...biomass for planted species.•Phosphorus cycling was governed by complex biochar-manure interactions.
Biochar and composted manure can impart benefits, such as improved nutrient cycling, increased productivity, and carbon sequestration, when they are applied to agricultural soils. There are limited data, however, on how these additives effect mixed perennial communities. We compare plant and soil community responses by using factorial applications of Royal Oak biochar (0%, 2.6%, and 5.2%) and composted manure (0 and 4.5kgm−2) in a tallgrass prairie restoration in Iowa. We found that biochar contributed to ecosystem function by increasing total carbon in the soil. We also found that biochar increased plant species richness and the 5.2% biochar treatment increased the biomass of plant species in the seed mix. Phosphorus cycling was altered by both the biochar and manure treatments; in soils with manure, biochar addition reduced phosphorus (P) availability compared with the control, but in soils without manure, biochar increased P availability. Belowground, the biochar and manure treatments affected the relative density of gram-negative bacteria, the relative density of actinobacteria, and root colonization by mycorrhizae. Contrary to our hypotheses, however, the biochar and manure treatments did not change total plant cover, total aboveground peak biomass, overall plant community, soil pH, inorganic nitrogen concentrations, extractable soil K, plant tissue N, soil microbial biomass-carbon, nematode density, and overall microbial community composition. Overall, we found several benefits and few externalities associated with biochar and composted manure addition to tallgrass prairie. However, these products can vary considerably and their interactions with soil, plants, and microbes can be situation specific. More study is needed to identify the characteristics of biochar that can affect mixed perennial communities prior to widespread use.
Human activities have increased nitrogen (N) and phosphorus (P) inputs in terrestrial ecosystems and altered carbon (C) availability, shifting the stoichiometry of microbial substrates in soils, such ...as the C:N:P ratios of the dissolved organic matter pool. These stoichiometric deviations between microbial biomass and its substrate may control microbial processes of N cycling. We studied the effects of this stoichiometric mismatch using a full factorial N and P addition experiment replicated in six grassland ecosystems in South Africa, the USA, and the UK. We found that N and P addition changed the dissolved organic matter C:N ratio, but not the C:N ratio of the soil microbial biomass. Compared to P addition, N addition decreased microbial N acquisition via non-symbiotic N2 fixation by −55% and increased microbial N release via net N mineralization by +134%. A possible explanation is that the dissolved elements, e.g., dissolved organic C (DOC) and dissolved total N (DN), serve as the main microbial substrate and its C:N ratio defines whether N is scarce or abundant with respect to microbial demands. If N is available in excess relative to microbial demands, net N mineralization increases. In contrast, when N is scarce, immobilization outweighs release decreasing net N mineralization. However, the activity of leucine aminopeptidases, which decompose peptides, was not affected by nutrient additions. Further, C rather than P availability may control the rates of non-symbiotic N2 fixation in the six studied grassland sites. In conclusion, globally increasing nutrient inputs change processes of microbial N acquisition and release in grassland ecosystems and these changes are largely driven by shifts in substrate stoichiometry.
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•We investigated N cycling processes upon N and P addition in six grassland soils.•N and P addition had no significant effect of microbial biomass stoichiometry.•N cycling processes were largely driven by changes in substrate stoichiometry.•N addition decreased microbial N2 fixation and increased net N mineralization.•N and P addition did not affect the activity of leucine-aminopeptidases.
Despite growing interest in adult attention-deficit/hyperactivity disorder (ADHD), little is known about predictors of persistence of childhood cases into adulthood.
A retrospective assessment of ...childhood ADHD, childhood risk factors, and a screen for adult ADHD were included in a sample of 3197 18–44 year old respondents in the National Comorbidity Survey Replication (NCS-R). Blinded adult ADHD clinical reappraisal interviews were administered to a sub-sample of respondents. Multiple imputation (MI) was used to estimate adult persistence of childhood ADHD. Logistic regression was used to study retrospectively reported childhood predictors of persistence. Potential predictors included socio-demographics, childhood ADHD severity, childhood adversity, traumatic life experiences, and comorbid DSM-IV child-adolescent disorders (anxiety, mood, impulse-control, and substance disorders).
Blinded clinical interviews classified 36.3% of respondents with retrospectively assessed childhood ADHD as meeting DSM-IV criteria for current ADHD. Childhood ADHD severity and childhood treatment significantly predicted persistence. Controlling for severity and excluding treatment, none of the other variables significantly predicted persistence even though they were significantly associated with childhood ADHD.
No modifiable risk factors were found for adult persistence of ADHD. Further research, ideally based on prospective general population samples, is needed to search for modifiable determinants of adult persistence of ADHD.
A total of 1500 nonthoracic MRI examinations were performed on patients with a non–MRI-conditional pacemaker or ICD, after programming of the devices in accordance with a standardized protocol. No ...patient whose device was appropriately programmed had device or lead failure.
The use of magnetic resonance imaging (MRI) poses potential safety concerns for patients with an implanted cardiac device (cardiac pacemaker or implantable cardioverter–defibrillator ICD). These concerns are a consequence of the potential for magnetic field–induced cardiac lead heating, which could result in myocardial thermal injury and detrimental changes in pacing properties.
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As a result, it has long been recommended that patients with an implanted cardiac device not undergo MRI scanning, even when it otherwise may be considered to be the most appropriate diagnostic imaging method for the patient’s clinical care.
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Over the past two decades, cardiac devices have been . . .
To evaluate the prevalence, comorbid conditions, and impairments of attention-deficit/hyperactivity disorder (ADHD) among young adolescents in Porto Alegre, Brazil.
1,013 students aged 12 to 14 years ...were evaluated at 64 state schools, using a screening instrument based on the 18 DSM-IV ADHD symptoms. All positive screened students (n = 99) and a random subset of negative screened subjects (n = 92) had a psychiatric evaluation carried out within a hospital setting or at home.
The prevalence of ADHD was estimated to be 5.8% (95% confidence interval = 3.2-10.6), and the comorbidity with other disruptive behavior disorders was high (47.8%). Youths with ADHD (n = 23) had significantly higher rates of school repetitions, suspensions, and expulsions (p < .01) than controls (n = 168). No association was identified between ADHD and alcohol, marijuana, and inhalant use.
The results extend to adolescents well-documented findings in children, indicating that ADHD is quite prevalent in early adolescence and affected youths are at high risk for impairment and dysfunction in multiple domains.
The separate components of evapotranspiration (ET) elucidate the pathways and time scales over which water is returned to the atmosphere, but ecosystem‐scale measurements of transpiration (T) and ...evaporation (E) remain elusive. We propose a novel determination of E and T using multiyear eddy covariance estimates of ET and gross ecosystem photosynthesis (GEP). The method is applicable at water‐limited sites over time periods during which a linear regression between GEP (abscissa) and ET (ordinate) yields a positive ET axis intercept, an estimate of E. At four summer‐rainfall semiarid sites, T/ET increases to a peak coincident with maximum GEP and remains elevated as the growing season progresses, consistent with previous, direct measurements. The seasonal course of T/ET is related to increasing leaf area index and declining frequency of rainy days—an index of the wet surface conditions that promote E—suggesting both surface and climatic controls on ET partitioning.
Key Points
A new method is developed to partition ET using multiyear carbon and water flux measurements
The method is applied to semiarid sites and shows that E peaks at the start of rainy season and declines as the growing season progresses
Magnitudes and trends in E and T/ET are consistent with field observations and known effects from surface and climate controls
Drylands account for approximately 40% of the global land surface and play a dominant role in the trend and variability of terrestrial carbon uptake and storage. Gross ecosystem photosynthesis – ...termed gross primary productivity (GPP) – is a critical driver of terrestrial carbon uptake and remains challenging to be observed directly. Currently, vegetation indices that largely capture changes in greenness are the most commonly used datasets in satellite-based GPP modeling. However, there remains significant uncertainty in the spatiotemporal relationship between greenness indices and GPP, especially for relatively heterogeneous dryland ecosystems. In this paper, we compared vegetation greenness indices from PhenoCam and satellite (Landsat and MODIS) observations against GPP estimates from the eddy covariance technique, across three representative ecosystem types of the southwestern United States. We systematically evaluated the changes in the relationship between vegetation greenness indices and GPP: i) across spatial scales of canopy-level, 30-meter, and 500-meter resolution; and ii) across temporal scale of daily, 8-day, 16-day, and monthly resolution. We found that greenness-GPP relationships were independent of spatial scales as long as land cover type and composition remained relatively constant. We also found that the greenness-GPP relationships became stronger as the time interval increased, with the strongest relationships observed at the monthly resolution. We posit that the greenness-GPP relationship breaks down at short timescales because greenness changes more slowly than plant physiological function, which responds rapidly to changes in key biophysical drivers. These findings provide insights into the potential for and limitations of modeling GPP using remotely sensed greenness indices across dryland ecosystem types.
•Variation in dominant land cover mediates VI-GPP relationship in the spatial domain.•VI better captures changes in GPP at longer temporal intervals.•Alternative remote sensing proxies needed to better monitor short-term GPP changes
Reintroduction of imperiled native freshwater fish is becoming an increasingly important conservation tool amidst persisten anthropogenic pressures and new threats related to climate change. We ...summarized trends in native fish reintroductions in the current literature, identified predictors of reintroduction outcome, and devised recommendations for managers attempting future native fish reintroductions. We constructed random forest classifications using data from 260 published case studies of native fish reintroductions to estimate the effectiveness of variables in predicting reintroduction outcome. The outcome of each case was assigned as a success or failure on the basis of the author's perception of the outcome and on whether or not survival, spawning, or recruitment were documented during post-reintroduction monitoring. Inadequately addressing the initial cause of decline was the best predictor of reintroduction failure. Variables associated with habitat (e.g., water quality, prey availability) were also good predictors of reintroduction outcomes, followed by variables associated with stocking (e.g., genetic diversity of stock source, duration of stocking event). Consideration of these variables by managers during the planning process may increase the likelihood for successful outcomes in future reintroduction attempts of native freshwater fish. La reintroducción de peces nativos de agua dulce que se encuentran en peligro se está convirtiendo cada vez más en una herramienta importante de conservación frente a las presiones antropogénicas persistentes y nuevas amenazas relacionadas con el cambio climático. Resumimos las tendencias encontradas en la literatura actual sobre la reintroducción de peces nativos, identificamos pronosticadores de resultados de la reintroducción e ideamos recomendaciones para administradores que intenten reintroducciones de peces nativos en el futuro. Construimos clasificaciones de bosque aleatorio a partir de datos de 260 estudios de caso publicados sobre la reintroducción de peces nativos para estimar la efectividad de las variables en la predicción del resultado de la reintroducción. El resultado de cada caso fue asignado como un éxito o un fracaso con base en la percepción del autor a partir del resultado y dependiendo de si se documentó o no la supervivencia, el desove o el reclutamiento durante el monitoreo posterior a la reintroducción. Abordar inadecuadamente a la causa inicial de la declinación fue el mejor pronosticador del fracaso de la reintroducción. Las variables asociadas con el hábitat (p. ej.: calidad del agua, disponibilidad de la presa) también fueron buenos pronosticadores de los resultados de la reintroducción, seguidas por las variables asociadas con el stock (p. ej.: la diversidad genética de la fuente del stock, duración del evento de stock). Que los administradores consideren estas variables durante el proceso de planeación puede incrementar la probabilidad de resultados exitosos en futuros intentos de reintroducción de peces nativos de agua dulce.
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