15 research outputs found
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Geophysical constraints on deep weathering and water storage potential in the Southern Sierra Critical Zone Observatory
The conversion of bedrock to regolith marks the inception of critical zone processes, but the factors that regulate it remain poorly understood. Although the thickness and degree of weathering of regolith are widely thought to be important regulators of the development of regolith and its water-storage potential, the functional relationships between regolith properties and the processes that generate it remain poorly documented. This is due in part to the fact that regolith is difficult to characterize by direct observations over the broad scales needed for process-based understanding of the critical zone. Here we use seismic refraction and resistivity imaging techniques to estimate variations in regolith thickness and porosity across a forested slope and swampy meadow in the Southern Sierra Critical Zone Observatory (SSCZO). Inferred seismic velocities and electrical resistivities image a weathering zone ranging in thickness from 10 to 35m (average=23m) along one intensively studied transect. The inferred weathering zone consists of roughly equal thicknesses of saprolite (P-velocity<2kms-1) and moderately weathered bedrock (P-velocity=2-4kms-1). A minimum-porosity model assuming dry pore space shows porosities as high as 50% near the surface, decreasing to near zero at the base of weathered rock. Physical properties of saprolite samples from hand augering and push cores are consistent with our rock physics model when variations in pore saturation are taken into account. Our results indicate that saprolite is a crucial reservoir of water, potentially storing an average of 3m3m-2 of water along a forested slope in the headwaters of the SSCZO. When coupled with published erosion rates from cosmogenic nuclides, our geophysical estimates of weathering zone thickness imply regolith residence times on the order of 105years. Thus, soils at the surface today may integrate weathering over glacial-interglacial fluctuations in climate. © 2013 John Wiley & Sons, Ltd
Externalizing and tantrum behaviours in children with ASD and ADHD compared to children with ADHD
OBJECTIVE: Compare rates of externalizing in children with autism spectrum disorder (ASD) and attention deficit/hyperactivity disorder (ADHD) symptoms to children with ADHD. METHOD: Parents/caregivers of 85 children with ASD and/or ADHD were surveyed about their children\u27s behaviours using the Autism Spectrum Disorders-Comorbidity for Children and the Autism Spectrum Disorders-Behaviour Problem for Children. RESULTS: Specific main effects analyses were then conducted. Children with ASD exhibited a higher number of externalizing (F(1, 83) = 83.34, p \u3c 0.001) and tantrum behaviours (F(1,83) = 781.86, p \u3c 0.001) than children without ASD. CONCLUSIONS: ASD exacerbates the externalizing symptoms of ADHD during childhood. This study adds to the literature on the importance of assessing for a wide-range of possible behaviour problems in children presenting with ADHD symptomatology. The implications of these findings are discussed in the context of other research