Dissolved Organic Carbon Retention in Soils McCracken, Kimberly L.; McDowell, William H.; Harter, Robert D. ...
Soil Science Society of America journal,
March 2002, Volume:
66, Issue:
2
Journal Article
Peer reviewed
Open access
Interactions between dissolved organic C (DOC) and mineral soils were examined in a laboratory column study. Specific emphasis was given to comparisons of soil and solution measurements of organic C ...(OC) retention in four soil parent materials. Soil columns were leached with one of three concentrations of forest floor (FF) leachate or distilled water every third day for 1 yr. The concentration of DOC in solution was analyzed before and after percolation through soil columns to assess net release or retention of DOC. Changes in soil chemical properties (pH, loss‐on‐ignition LOI, extractable Al and Fe) following leaching were consistent with podzolization. Micromorphological investigation of the soil materials following leaching showed increased accumulation of organo‐metallic coatings in materials treated with high concentrations of DOC relative to distilled water or low concentrations of DOC. The most dramatic changes in soil chemical properties were found in soils leached with high concentrations of DOC. Comparison of solution and soil measures of OC retention indicates that only ∼50% of the DOC lost from solution was measured as soil OC at the end of the experiment. This finding suggests that microbial decomposition is a significant factor regulating OC concentrations in soils and that soil solution data alone do not yield a complete picture of soil OC dynamics.
This study examined the relations among expressive phonology, phonological sensitivity, and early decoding skills in children attending kindergarten through 2nd grade. Extant literature suggests that ...children with disordered speech may be at additional risk for reading difficulties; however, due to methodological shortcomings, findings from previous research are questionable. A total of 140 children between the ages of 5 and 8-years of age were randomly selected from a pool of 392 children recruited from local schools to participate in assessments involving oral language, expressive phonology, phonological sensitivity, and early decoding skills. Results from correlational analyses revealed significant relations between most measures of phonological sensitivity, expressive phonology, and decoding skills, even after partialling out variance common to oral language. Additionally, results from simultaneous multiple regression analyses demonstrated that the Phonological Sensitivity, Lexical Access and Multisyllabic speech production jointly predicted early decoding skills. Phonological Memory and single-naming speech production did not. Additionally, Phonological Sensitivity, Lexical Access, and Multisyllabic speech production each predicted unique variance in Decoding. Finally, hierarchical multiple regression results indicated that whereas for the youngest group of children, those with poorer speech skills (as measured by multisyliabic word productions) or poorer phonological sensitivity skills also displayed poorer decoding skills, this relation was not found to be significant for the older children. Age did not moderate the relations between Lexical Access and Decoding. Results support extant literature suggesting that reading deficits stem from an underlying phonological deficit and that speech may serve as an early indicator of potential reading problems. Clinical implications include the need to use more sensitive, complex expressive phonological measures and to incorporate exposure to written language into speech therapy sessions. Additionally, future research should focus on extending current findings by examining the relations among speech and reading in a longitudinal nature.
This study examined the relations among expressive phonology, phonological sensitivity, and early decoding skills in children attending kindergarten through 2nd grade. Extant literature suggests that ...children with disordered speech may be at additional risk for reading difficulties; however, due to methodological shortcomings, findings from previous research are questionable. A total of 140 children between the ages of 5- and 8-years of age were randomly selected from a pool of 392 children recruited from local schools to participate in assessments involving oral language, expressive phonology, phonological sensitivity, and early decoding skills. Results from correlational analyses revealed significant relations between most measures of phonological sensitivity, expressive phonology, and decoding skills, even after partialling out variance common to oral language. Additionally, results from simultaneous multiple regression analyses demonstrated that the Phonological Sensitivity, Lexical Access and Multisyllabic speech production jointly predicted early decoding skills (ΔR2 = .34). Phonological Memory and single-naming speech production did not. Additionally, Phonological Sensitivity, Lexical Access, and Multisyllabic speech production each predicted unique variance in Decoding. Finally, hierarchical multiple regression results indicated that whereas for the youngest group of children, those with poorer speech skills (as measured by multisyllabic word productions) or poorer phonological sensitivity skills also displayed poorer decoding skills, this relation was not found to be significant for the older children. Age did not moderate the relations between Lexical Access and Decoding. Results support extant literature suggesting that reading deficits stem from an underlying phonological deficit and that speech may serve as an early indicator of potential reading problems. Clinical implications include the need to use more sensitive, complex expressive phonological measures and to incorporate exposure to written language into speech therapy sessions. Additionally, future research should focus on extending current findings by examining the relations among speech and reading in a longitudinal nature.
Thesis (Ph. D.)--Florida State University, 2004.
Advisor: Dr. Howard Goldstein, Florida State University, College of Communication, Dept. of Communication Disorders. Title and description from ...dissertation home page (viewed July 9, 2004). Includes bibliographical references.
This paper describes an exploratory study to identify which environmental and student factors best predict intention to persist in the computer science major. The findings can be used to make ...decisions about initiatives for increasing retention. Eight indices of student characteristics and perceptions were developed using the research-based Student Experience of the Major Survey: student-student interaction; student-faculty interaction; collaborative learning opportunities; pace/workload/prior experience with programming; teaching assistants; classroom climate/pedagogy; meaningful assignments; and racism/sexism. A linear regression revealed that student-student interaction was the most powerful predictor of students' intention to persist in the major beyond the introductory course. Other factors predicting intention to persist were pace/workload/prior experience and male gender. The findings suggest that computer science departments interested in increasing retention of students set structured expectations for student-student interaction in ways that integrate peer involvement as a mainstream activity rather than making it optional or extracurricular. They also suggest departments find ways to manage programming experience gaps in CS1.
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