45 research outputs found

    Microbial Community Structure and Litter Decomposition in Stratified Soils of a Long Term Reduced Tillage Experiment

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    The aim of the present study was to examine decomposition of plant material (maize straw, green and rooibos tea) in stratified soils of the long-term tillage experiment, established in 1999 and shifted from conventional to organic farming system in 2015. The plowing in conventional tillage (CT) has been done by moldboard plow 20 cm deep, while in minimum tillage (MT), soil disturbance has been up to 10 cm deep by a Special disc harrow. More than 15 years of long term Minimum tillage, with reduced soil disturbances and improved residue management, resulted in stratification of soil organic carbon and nutrients with highest concentrations in the very topsoil

    Follow-up Imaging of Disk Candidates from the Disk Detective Citizen Science Project: New Discoveries and False Positives in WISE Circumstellar Disk Surveys

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    The Disk Detective citizen science project aims to find new stars with excess 22 m emission from circumstellar dust in the All WISE data release from the Wide-field Infrared Survey Explorer. We evaluated 261 Disk Detective objects of interest with imaging with the Robo-AO adaptive optics instrument on the 1.5 m telescope at Palomar Observatory and with RetroCam on the 2.5 m du Pont Telescope at Las Campanas Observatory to search for background objects at 0 1512 separations from each target. Our analysis of these data leads us to reject 7% of targets. Combining this result with statistics from our online image classification efforts implies that at most7.9%0.2% of All WISE-selected infrared excesses are good disk candidates. Applying our false-positive rates to other surveys, we find that the infrared excess searches of McDonald et al. and Marton et al. all have false-positiverates >70%. Moreover, we find that all 13 disk candidates in Theissen & West with W4 signal-to-noise ratio >3are false positives. We present 244 disk candidates that have survived vetting by follow-up imaging. Of these,213 are newly identified disk systems. Twelve of these are candidate members of comoving pairs based on Gaia astrometry, supporting the hypothesis that warm dust is associated with binary systems. We also note the discovery of 22 m excess around two known members of the ScorpiusCentaurus association, and we identifyknown disk host WISEA J164540.79-310226.6 as a likely Sco-Cen member. Thirty of these disk candidates arecloser than 125 pc (including 26 debris disks), making them good targets for both direct-imaging exoplanetsearches

    Follow-up Imaging of Disk Candidates from the Disk Detective Citizen Science Project: New Discoveries and False Positives in WISE Circumstellar Disk Surveys

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    The Disk Detective citizen science project aims to find new stars with excess 22 μm emission from circumstellar dust in the AllWISE data release from the Wide-field Infrared Survey Explorer. We evaluated 261 Disk Detective objects of interest with imaging with the Robo-AO adaptive optics instrument on the 1.5 m telescope at Palomar Observatory and with RetroCam on the 2.5 m du Pont Telescope at Las Campanas Observatory to search for background objects at 0.”15–12'' separations from each target. Our analysis of these data leads us to reject 7% of targets. Combining this result with statistics from our online image classification efforts implies that at most 7.9% ± 0.2% of AllWISE-selected infrared excesses are good disk candidates. Applying our false-positive rates to other surveys, we find that the infrared excess searches of McDonald et al. and Marton et al. all have false-positive rates >70%. Moreover, we find that all 13 disk candidates in Theissen & West with W4 signal-to-noise ratio >3 are false positives. We present 244 disk candidates that have survived vetting by follow-up imaging. Of these, 213 are newly identified disk systems. Twelve of these are candidate members of comoving pairs based on Gaia astrometry, supporting the hypothesis that warm dust is associated with binary systems. We also note the discovery of 22 μm excess around two known members of the Scorpius–Centaurus association, and we identify known disk host WISEA J164540.79-310226.6 as a likely Sco-Cen member. Thirty of these disk candidates are closer than ~125 pc (including 26 debris disks), making them good targets for both direct-imaging exoplanet searches

    Attachment Manifestations in Daily Interpersonal Interactions

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    The predominant focus in attachment research on trait-like individual differences has overshadowed investigation of the ways in which working models of attachment represent dynamic, interpersonally responsive socio-affective systems. Intensive longitudinal designs extend previous work by evaluating to what extent attachment varies over social interactions and the functional processes that underlie its fluctuation. We examined momentary activation of attachment orientations in the stream of peoples’ daily lives and how those patterns were linked to interpersonal behavior. Based on an event-contingent, ambulatory 7-day assessment protocol (N=263; 3971 interactions) operationalized using Contemporary Integrative Interpersonal Theory, we examined whether contextually activated working models accounted for patterns of interpersonal (anti-)complementarity. Our analyses revealed that the situational activation of working models varied as a function of interpersonal perceptions of warmth, which were linked to greater state security and lower levels of anxious or avoidant expectations. These reactivity patterns, in turn, accounted for interpersonal complementarity. Avoidant attachment was linked to diminished and secure attachment to enhanced expressions of warmth. The analyses were robust even when controlling for momentary positive and negative affect and closeness of the relationship. Attachment expectations wax and wane across daily social interactions, and such fluctuations are reflective primarily of a process in which perceptions of others’ warmth activate secure attachment expectations and lower insecure ones

    Consequences of minimum soil tillage on abiotic soil properties and composition of microbial communities in a shallow Cambisol originated from fluvioglacial deposits.

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    A long-term field experiment was run for 12 years to evaluate the impact of minimum tillage (MT) compared to conventional mouldboard ploughing (CT) on soil chemical, physical and microbial properties in a shallow Cambisol formed over fluvioglacial deposits of Drava river in Slovenia. Significant differences between MT and CT were found in vertical distribution of soil organic C (SOC) and nutrients (total N and plant available potassium); under MT, concentrations decreased from the soil surface to the lower layers, as opposed to CT which maintained rather uniform distribution down to the ploughing depth. MT in comparison with CT also increased the proportion of water-stable 2–4-mm-sized aggregates (80.9 and 61.3 %, respectively), water holding capacity (24.8 and 22.2 %, respectively) and plant available water (13.4 and 10.3 %, respectively) in the upper 0–10-cm soil layer. Bulk density, porosity, the proportion of water-stable 1–2-mm-sized aggregates and infiltration rate showed no significant differences between the tillage treatments. SOC content in the upper 0–10-cm soil layer was not significantly different between MT and CT (1.60 ± 0.07 and 1.45 ± 0.05 %, respectively), as well as the overall stock in the investigated soil profile (0–60 cm) remained unaffected (57.4 ± 0.8 and 59.1 ± 2.2 t ha−1, respectively). Microbial biomass, estimated by the total soil DNA, was higher in MT than CT in the 0–10-cm layer. Furthermore, a positive linear dependence of microbial biomass on SOC content was observed. Fingerprinting of bacterial, fungal and archaeal communities indicated that microbial community composition changed by long-term MT, whereas changes in microbial diversity were not detected for any domain. The most pronounced shifts in the composition were found for bacterial communities in the 10–20-cm layer, while the composition of fungal communities slightly changed in the upper 0–10 cm of MT soil. The composition of archaeal communities was not affected by the tillage or by the soil depth. Our results indicate that MT generates modest changes in soil structure and soil water retention properties and could support measures against erosion, drought and nutrient leaching. Considering increased microbial biomass in the topsoil of MT and shifts in microbial diversity, the impacts of MT on soil microbiome are also evident and need to be further investigated to identify the affected functional traits
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