Correlations between precipitation patterns in southern mexico and the El Niño sea surface temperature index

Historical data for regional climate research in the tropics is typified by extreme unevenness in both temporal and spatial coverage. Spatial interpolation techniques were applied in order to fill the gaps in time series of rainfall records for the state of Chiapas. The method involved iterated universal Kriging that combines a spatial covariance function with a polynomial trend surface. Automated outlier removal was used to prevent spurious records distorting the results. The procedure was applied 612 times in order to produce complete monthly time series from 1950 to 2000. In order to trace temporal trends the time series were decomposed into seasonal, trend and irregular components and analyzed using loess smoothing (STL). The seasonal values were removed, and the remainder smoothed to find the trend. An identical procedure was applied to the El Niño3.4 index. The trend component of each data set was analyzed for autocorrelation and cross correlation. The autocorrelation function for the standardized number of days with rainfall shows significant positive correlations between data points around three to four months apart. There is significant negative cross correlation between the standardized El Niño sea surface temperature index and rainfall. The technique thus led to a clear description of a pattern that might be used in order to partly predict precipitation driven events such as floods and wildfire

How predictive is traditional ecological knowledge? the case of the Lacandon Maya Fallow Enrichment System

La habilidad de predecir mediante una asociación estadística o conocimiento causal es la clave característica del conocimiento científico. Sin embargo, el poder predictivo del conocimiento ecológico tradicional basado en datos obtenidos de observaciones pocas veces ha sido evaluado o criticado. Analizamos el poder predictivo de los resultados de un estudio de caso en el manejo de acahuales (vegetación secundaria). Para este propósito aplicamos tres análisis estadísticos contrastantes; análisis de covarianza, modelación espacial descriptiva y modelo gráfico. Nuestros resultados sugieren la necesidad de contar con cierto grado de abducción o explicación a posteriori para el análisis de las observaciones derivadas de las estrategias realizadas por los indígenas. A pesar de ello pudimos reconocer el poder predictivo del conocimiento indígena a partir de una combinación de experiencia, deducción e inducción probabilística. El presente estudio de caso sugiere que el conocimiento ecológico tradicional lacandón es de utilidad para guiar los esfuerzos hacia la restauración del ecosistema selvático, particularmente con el uso de Ochroma pyramidale como agente de enriquecimiento del suelo.

The ability to predict through causal understanding or statistical association is a key feature of scientific knowledge. However, the predictive power of traditional ecological knowledge in an observational setting is rarely critically evaluated. We analyze the results of an applied case study of indigenous fallow management in the context of its predictive power. In order to do this we applied three contrasting statistical analyses; visual pattern matching, general linear modelling and graphical models. Our results suggest that a degree of abduction or a posteriori explanation is typically needed in the analysis of the observations of natural phenomena that indigenous people make. Despite this, contextually useful predictive power may be extracted from such information through a combination of experience, deduction and probabilistic induction. The present case study suggested that the traditional ecological knowledge of the Lacandon people could provide useful guidance for the restoration of ecosystem function. In particular, the results support the use of Ochroma pyramidale as a soil enriching agent.

A habilidade de predizer mediante uma associação estatística ou conhecimento causal é a clave característica do conhecimento científico. No entanto, o poder preditivo do conhecimento ecológico tradicional baseado em dados obtidos de observações poucas vezes tem sido avaliado ou criticado. Analisamos o poder preditivo dos resultados de um estudo de caso no manejo de "acahuales" (vegetação secundária). Para este propósito aplicamos três analises estatísticas contrastantes; analise de co variação, modelação espacial descritiva e modelo gráfico. Nossos resultados sugerem a necessidade de contar com certo grau de abdução ou explicação a posteriori para a análise das observações derivadas das estratégias realizadas pelos indígenas. A pesar disto podemos reconhecer o poder preditivo do conhecimento indígena a partir de uma combinação de experiência, dedução e indução probabilística. O presente estudo de caso sugere que o conhecimento ecológico tradicional lacandon é de utilidade para guiar os esforços para a restauração do ecossistema selvático, particularmente com o uso de Ochroma pyramidale como agente de enriquecimento do solo.