Programa e Resumos - I Congresso IbÃ©rico de CiÃªncia do Solo 2004

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I Congresso Ibérico da Ciência do Solo – 15 a 18 de Junho de 2004, Bragança, Portugal Assessment of changes in soil C and N – components, methodologies, issues and implications Partap K. Khanna Institute of Soil Science and Forest Nutrition, Buesgenweg 2, 37077 Goettingen, GERMANY e- mail address: pkhanna@gwdg.de Resumo Comunicação: Oral In recent years demands by policy makers to assess changes due to land management practices in soil organic C (SOC) and N (SON) contents have given a fresh impetus to understand what factors and processes affect such changes and in what way one can bring about certain desired changes in SOC and SON contents. The primary issues are related to: changes in greenhouse gases, the productivity levels of ecosystems, adverse effects on the ground water quality and the maintenance of biological diversity. Most ecosystems are continually changing in their structure and sometimes in their functioning, both leading to changes in SOC. This paper will present some of these issues in terms of their needs and the level of accuracy required for assessing SOC changes. SOC and SON occur as multi-component substances and any assessment of change would need the description of individual components and their degree of change, the significance of which requires further consideration in relation to the natural variability in the spatial and temporal scales. Components are arbitrarily grouped into two types – those which are easily and in short term mobilizeable and those which are resistant or protected and need long time to mobilize, with major consequences on the assessment methodology and implications. These are sometimes distinguished by physical (size and density based fractions), chemical (soluble, extractable or to a varying degree oxidisable), biological (microbial biomass, respiration potential) and biochemical (lignin, alkyl, phenol and polysaccharides contents). The paper will summarize some of the essential methods including the use of stable isotopes in terms of their limitations and usefulness to assess changes in SOC and SON. Quantitative assessment of SOC and SON requires a reliable estimate of any changes bulk density (BD). Do we have a reliable method of assessing BD of soils Sources of SOC and SON are primarily related to plant growth (specifically root growth) whereas minor inputs can be those of agricultural residues and waste materials. Any retention of C and N by soils will primarily depend upon microbial and faunal decomposition activities and soil factors controlling the accessibility (protection factors – high clay, high Al and Ca, aggregation), retardation (high N, low pH) and acceleration (priming effects of dissolved OC, low molecular weight organic acids). Commonly three continuous phases of litter decomposition are outlined which will be described in terms of their effects on the assessment of SOC changes. There are strong interactions between SOC and SON and during the discussion on SOC changes, the role of SON is not adequately considered. The implications of such interactions will be described in terms of developing greenhouse gases, and changing productivity, biodiversity and health of ecosystems. – 28 –
I Congresso Ibérico da Ciência do Solo – 15 a 18 de Junho de 2004, Bragança, Portugal La enseñanza de la Ciencia del Suelo asistida por ordenador Carlos Dorronsoro Fernández Dpto. Edafologia y Química Agricola, Facultad de Ciencias, Universidad de Granada, 18002 Granada, Spain, FAX 34 958 244160, cfdorron@ugr.es Resumo Comunicação: Oral Los avances alcanzados en la digitalización de imágenes con calidad fotográfica han posibilitado la utilización del ordenador personal para elaborar programas multimedia con alta capacidad docente y muy atractivos para el alumnado, lo que era impensable hace tan solo muy pocos años. En el Departamento de Edafología de las Universidades de Salamanca y Granada, hemos venido realizando desde 1988 un conjunto de programas multimedia de autoaprendizaje personalizado interactivo. Los programas en un principio corrían sólo en ordenadores Apple Macintosh pero actualmente han sido reelaborados para los ordenadores PC en entorno Windows. Para presentar en este 1 er Congreso Ibérico de la Ciencia del Suelo se han elaborado los siguientes programas: i) HorSol.html. Este programa se pretende mostrar como el suelo es un material heterogéneo constituido por una secuencia de capas homogéneas llamadas horizontes. ii) ClasSol.html. Nos ocupamos aquí la técnica de la clasificación de los suelos, según la “Base Referencial del Recurso Suelo” (FAO, 1998). iii) TetrisSol.html. Este programa complementa la línea de morfología y clasificación de suelos presentada en los dos anteriores. Se trata aquí de construir una imagen del perfil de un suelo a partir de un conjunto de fotografías de horizontes de suelos. iv) AgroMap.html A partir de un determinado mapa cartográfico se han de evaluar las capacidades de uso de los suelos con sólo datos referentes a la clase de suelo, del relieve y de la litología. iv) AgroBloq.html. Técnicas de evaluación de suelos según el sistema de Clases Agrológicas del USDA (1965). Todos los programas son autoevaluadores de forma que califica automáticamente los ejercicios realizados. Han sido escritos en lenguaje multiplataforma (Windows-PC, Apple-Macintosh, Linus …) HTML/JavaScript. Se ha desarrollado un navegador de alta seguridad (soile v1.0) para examinar a los alumnos que anula algunas opciones no deseadas de los navegadores de Internet (navegación a través de la barra de menú principal, refresco de la pantalla, ver código, acceso y manipulación de las páginas visitadas) y dotado de grabación automática, en un archivo, de todo lo realizado durante cada sesión de prácticas. – 29 –
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Programa e Resumos - I Congresso IbÃ©rico de CiÃªncia do Solo 2004

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