1,471 research outputs found
Soil carbon pools are affected by species identity and productivity in a tree common garden experiment
The formation and turnover of soil organic carbon (C), the largest terrestrial C pool, is strongly impacted by the ultimate source of that C: leaves, wood, roots, and root exudates. The quantity and quality of these inputs is determined by the identity of the plants involved. Yet substantial uncertainty surrounds the complex relationships among plant traits and soil C, precluding efforts to maximize whole-ecosystem C uptake in nature-based climate mitigation scenarios. In this study, we leveraged a biodiversity-ecosystem function experiment with trees (IDENT) to explore the effects of interspecific variation in plant traits on soil C dynamics in the very early stages of stand development (9 years since planting). Mineral soil C stocks to 5 cm depth were quantified in monospecific plots of 19 tree species planted on a former agricultural field, and analyzed in relation to tree growth and functional traits. We found that tree species identity affected soil bulk density and, to a lesser extent, the carbon content of the topsoil, and thereby total C pools. Among species and across plots, mineral soil C stocks were positively correlated with rates of tree growth and were significantly larger beneath broadleaf trees with âfastâ functional traits vs. conifers with more conservative leaf traits, when comparisons were made over equivalent soil depth increments. Thus, plant functional traits mediate interspecific differences in productivity, which in turn influence the magnitude of belowground C stocks. These results highlight important linkages between above- and belowground carbon cycles in the earliest stages of afforestation
Beta-delayed-neutron studies of Sb and I performed with trapped ions
Beta-delayed-neutron (n) spectroscopy was performed using the
Beta-decay Paul Trap and an array of radiation detectors. The n
branching ratios and energy spectra for Sb and I were
obtained by measuring the time of flight of recoil ions emerging from the
trapped ion cloud. These nuclei are located at the edge of an isotopic region
identified as having n branching ratios that impact the r-process
abundance pattern around the A~130 peak. For Sb and I,
n branching ratios of 14.6(11)%, 17.6(28)%, and 7.6(28)% were
determined, respectively. The n energy spectra obtained for Sb
and I are compared with results from direct neutron measurements, and
the n energy spectrum for Sb has been measured for the first
time
Coupled hybrid modelling within the Fire Dynamics Simulator; transient transport and mass storage
Crystallographic analyses of an active HIV-1 ribonuclease H domain show structural features that distinguish it from the inactive form
Climate change reduces extent of temperate drylands and intensifies drought in deep soils
Drylands cover 40% of the global terrestrial surface and provide important
ecosystem services. While drylands as a whole are expected to increase in
extent and aridity in coming decades, temperature and precipitation forecasts
vary by latitude and geographic region suggesting different trajectories for
tropical, subtropical, and temperate drylands. Uncertainty in the future of
tropical and subtropical drylands is well constrained, whereas soil moisture
and ecological droughts, which drive vegetation productivity and composition,
remain poorly understood in temperate drylands. Here we show that, over the
twenty first century, temperate drylands may contract by a third, primarily
converting to subtropical drylands, and that deep soil layers could be
increasingly dry during the growing season. These changes imply major shifts
in vegetation and ecosystem service delivery. Our results illustrate the
importance of appropriate drought measures and, as a global study that focuses
on temperate drylands, highlight a distinct fate for these highly populated
areas
Effect of formant frequency spacing on perceived gender in pre-pubertal children's voices
<div><p>Background</p><p>It is usually possible to identify the sex of a pre-pubertal child from their voice, despite the absence of sex differences in fundamental frequency at these ages. While it has been suggested that the overall spacing between formants (formant frequency spacing - ÎF) is a key component of the expression and perception of sex in children's voices, the effect of its continuous variation on sex and gender attribution has not yet been investigated.</p><p>Methodology/Principal findings</p><p>In the present study we manipulated voice ÎF of eight year olds (two boys and two girls) along continua covering the observed variation of this parameter in pre-pubertal voices, and assessed the effect of this variation on adult ratings of speakers' sex and gender in two separate experiments. In the first experiment (sex identification) adults were asked to categorise the voice as either male or female. The resulting identification function exhibited a gradual slope from male to female voice categories. In the second experiment (gender rating), adults rated the voices on a continuum from âmasculine boyâ to âfeminine girlâ, gradually decreasing their masculinity ratings as ÎF increased.</p><p>Conclusions/Significance</p><p>These results indicate that the role of ÎF in voice gender perception, which has been reported in adult voices, extends to pre-pubertal children's voices: variation in ÎF not only affects the perceived sex, but also the perceived masculinity or femininity of the speaker. We discuss the implications of these observations for the expression and perception of gender in children's voices given the absence of anatomical dimorphism in overall vocal tract length before puberty.</p></div
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Properties of ion implanted Ti-6Al-4V processed using beamline and PSII techniques
The surface of Ti-6Al-4V (Ti64) alloy has been modified using beamline implantation of boron. In separate experiments, Ti64 has been implanted with nitrogen using a plasma source ion implantation (PSII) technique utilizing either ammonia (NH{sub 3}), nitrogen (N{sub 2}), or their combinations as the source of nitrogen ions. Beamline experiments have shown the hardness of the N-implanted surface saturates at a dose level of {approximately} 4 {times} 10{sup 17} at/cm{sup 2} at {approximately} 10 GPa. The present work makes comparisons of hardness and tribological tests of (1) B implantation using beamline techniques, and (2) N implanted samples using ammonia and/or nitrogen gas in a PSII process. The results show that PSII using N{sub 2} or NH{sub 3} gives similar hardness as N implantation using a beamline process. The presence of H in the Ti alloy surface does not affect the hardness of the implanted surface. Boron implantation increased the surface hardness by as much as 2.5x at the highest dose level. Wear testing by a pin-on-disk method indicated that nitrogen implantation reduced the wear rate by as much as 120x, and boron implantation reduced the wear rate by 6.5x. Increased wear resistance was accompanied by a decreased coefficient of friction
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