Modelacion de caudales recesivos para periodos estivales en la cuenca del Estero Upeo, Region del Maule.

134 p.El estudio que se presenta a continuación tiene coma objetivo estimar los caudales recesivos originados por los aportes de las aguas subterráneas del estero Upeo, ubicado en la VII Región de Chile. La información de entrada requerida para tal fin fue aportada por la Dirección General de Aguas y corresponde a los limnigramas y curvas de descarga del estero Upeo, en Upeo. Se ajustaron y evaluaron cuatro modelos predicativos, de los cuales tres fueron exponenciales (Q (t) = Qo e-α (t-t°), Q (t) = Q0 • e-α (t-t°)n , Q(t) = Q0 • e(-2α√t )) y uno potencial (Q(t) = Q0(1+α • t)-2 ), donde Q0 es el caudal inicial; α el coeficiente de agotamiento; n el parámetro específico, t tiempos y e constante de Neper. Los ajustes consistieron en la obtención de los coeficientes de agotamiento bajo los lapsos de 48, 72, 168, 240 horas y el total de horas de cada crecida. Con esta información, se determinó el caudal inicial de las crecidas seleccionadas bajo dos planteamientos: el original (segundo punto de quiebre en la curva de bajada del hidrograma) y el modificado (tercer punto de quiebre). Estos puntos fueron identificados a través de la grafica semilogarítmica del caudal (Q) v/s tiempo (t). La evaluación de los resultados se realizó a partir de las predicciones de cada modelo, cuyos valores se contrastaron con los observados, utilizando para ello el coeficiente de determinación (R2), la prueba U de Mann- Whitney, el error estándar de estimación y el test de concordancia de Bland y Altman (ACBA). De los cuatro modelos analizados, el que obtuvo mejores resultados fue el modelo exponencial 3 Q (t) = Qo • e(-2α√t) seguido del modelo potencial Q(t) = Qo (1 + α • t)-2. Además, el planteamiento modificado dio mejores resultados por sobre el planteamiento original. Finalmente, el mejor lapso para la estimación fue el correspondiente a las 240 horas, en base al test de Bland y Altman

Hongos micorrícicos arbusculares (HMA) asociados a poblaciones naturales de Peumus boldus en Chile Central

The positive contribution of tree-related mycorrhizae in the soil to plant ecosystems is well known, through symbioticrelationships. The regeneration and establishment of Peumus boldus (boldo), an endemic species of major economic andenvironmental relevance in Chile, is a complicated natural process, and the identification of tree-related mycorrhizalfungi (AMF) represents an important contribution to the recovery of native forest formations. The present study is aquantitative description of AMF, within natural boldo formations in central Chile. Twenty-three AMF species of severalfamilies --Acaulosporaceae (Acaulospora), Entrophosporaceae (Entrophospora), Glomeraceae (Funneliformis, Glomus,Rhizophagus, and Sclerocystis) and Paraglomeraceae (Paraglomus aff. Laccatum) -- were identified. Among these species,Funneliformis badius and Funneliformis constrictus were present at all sites. Likewise, Simpson index generally showsa high dominance of AMF species at all six studied sites. Shannon index, however, indicated that there is low speciesdiversity. This study will serve as a basis to optimize boldo’s establishment techniques, by knowing which types of AMFcan improve the success of the survival and development of the species, either in the form of commercial plantation ornatural sclerophyllous forest.Es conocido el aporte positivo a la vegetación que tiene la presencia de micorrizas arbusculares en el suelo a través de unarelación simbiótica. La regeneración y establecimiento de Peumus boldus, boldo, especie endémica de mayor importanciaeconómica y ambiental de Chile, es complicada, por lo que la identificación de hongos micorrícicos arbusculares (HMA)representa un importante aporte a la recuperación de formaciones naturales, así como al establecimiento de plantacionesde la especie. El presente estudio corresponde a una descripción cuantitativa de HMA presentes en formacionesnaturales de Peumus boldus en Chile Central. Se identificaron 23 especies de HMA de las familias Acaulosporaceae(Acaulospora), Entrophosporaceae (Entrophospora), Glomeraceae (Funneliformis, Glomus, Rhizophagus y Sclerocystis)y Paraglomeraceae (Paraglomus aff. laccatum). Dentro de las especies encontradas, se destacan a Funneliformis badius yFunneliformis constrictus cuya presencia se detectó en todos los sitios. Asimismo, el índice de Simpson muestra en generaluna alta dominancia de especies de HMA en seis sitios estudiados. El índice de Shannon, por su parte, indica que existe unabaja diversidad de especies en los sitios estudiados. Finalmente, este estudio servirá como base para optimizar las técnicasde establecimiento de boldo, al conocer que tipos de HMA pueden mejorar el éxito de la sobrevivencia y desarrollo de laespecie bajo esquema de plantación, así como de enriquecimiento y restauración en formaciones naturales de la especie ydel bosque esclerófilo

Annual and monthly runoff analysis in the Elqui River, Chile, a semi-arid snow-glacier fed basin

Balocchi, F., Pizarro, R., Meixner, T., & Urbina, F. (November-   December, 2017). Annual and monthly runoff analysis in   the Elqui River, Chile, a semi-arid snow-glacier fed basin.   Water Technology and Sciences (in Spanish), 8(6), 23-35, DOI:   10.24850/j-tyca-2017-06-02.   Climate change and its relationship to temperature are   critical factors affecting glaciers, especially when populations   depend on these ice reservoirs. The use of the precipitationrunoff   coefficient in semi-arid, mountainous regions that   are fed by glaciers can lead to important findings about   how glacial melt responds to climate change. This study   analyzed 40 years of monthly and annual precipitation   and runoff data (1970-2009) from four sub-basins of the   Elqui River (29° 27’- 30° 34’ S and 71° 22’- 69° 52’ W), in   the Coquimbo region of Chile. The Elqui basin has a rainsnow-   glacial melt regime. The areal average rainfall was   estimated using the Thiessen polygon method. Gumbel   and Goodrich probability distribution functions and the   Log-Normal Probability Density Function (PDF) were used   to understand the temporal behavior of precipitation and   streamflow. The data-time behavior and PP Q-1 coefficients   were also analyzed. And the Mann-Kendall (MK) test was   used to compare the results. No trends were found for flow,   while a negative trend in rainfall was identified. The summer   flows were notable, which remained constant. In spite of the   differences between the PP Q-1 coefficient and the MK test,   the flow clearly does not come from rainfall but rather from   glacial melt

Modelamiento matemático de caudales recesivos en la región mediterránea andina del Maule; el caso del estero Upeo, Chile

En el presente estudio se analizaron cuatro modelos matemáticos de estimación de caudales recesivos, con el fin de determinar cuál de ellos obtiene los mejores resultados en una cuenca andina del Maule, zona mediterránea de Chile central. Esto se realizó a través del análisis de 25 crecidas en la época estival 1971-2003, en donde se consideró el aporte exclusivo de las aguas subterráneas a partir del tercer punto de quiebre de la curva de bajada del hidrograma. Los resultados obtenidos demuestran que el modelo exponencial 3 es el que presenta las mejores estimaciones. En el caso del mejor lapso para el ajuste de los modelos, el tiempo de 240 horas es el que obtiene los mejores resultados, según el test de Bland y Altman

Contribution of advanced regeneration of Pinus Radiata D. Don. to transpiration by a fragment of Native forest in central Chile is out of proportion with the contribution to sapwood area

The transpiration of Nothofagus glauca (Phil.) Krasser and advanced Pinus radiata D. Don. regeneration was measured in a fragment of native N. glauca forest. Over the eight months of this study, P. radiata contributed approximately 60% of the total stand transpiration. This was out of proportion with the approximately 34% of the stand sapwood area contributed by P. radiata. This was due to the significantly greater sap flux density of the P. radiata compared to the N. glauca between May and October. Though the results are from a small study conducted as part of a larger experiment, it is argued that they suggest that invasion by P. radiata may substantially increase the risk from climate change to reserves of N. glauca forest in the Maule region of central Chile. In some reserves of N. glauca forest, Forestal Arauco S.A. manually removed P. radiata that regenerated after the wildfire of January 2017. This was a costly operation and there is a need for indices to assess competition. The ratio of sapwood area to leaf area is suggested as a potential index for assessing competition to identify stands at risk. © 2020 by the author

Contribution of advanced regeneration of Pinus Radiata D. Don. to transpiration by a fragment of Native forest in central Chile is out of proportion with the contribution to sapwood area

The transpiration of Nothofagus glauca (Phil.) Krasser and advanced Pinus radiata D. Don. regeneration was measured in a fragment of native N. glauca forest. Over the eight months of this study, P. radiata contributed approximately 60% of the total stand transpiration. This was out of proportion with the approximately 34% of the stand sapwood area contributed by P. radiata. This was due to the significantly greater sap flux density of the P. radiata compared to the N. glauca between May and October. Though the results are from a small study conducted as part of a larger experiment, it is argued that they suggest that invasion by P. radiata may substantially increase the risk from climate change to reserves of N. glauca forest in the Maule region of central Chile. In some reserves of N. glauca forest, Forestal Arauco S.A. manually removed P. radiata that regenerated after the wildfire of January 2017. This was a costly operation and there is a need for indices to assess competition. The ratio of sapwood area to leaf area is suggested as a potential index for assessing competition to identify stands at risk. © 2020 by the author

Rendimiento y composición mineral del forraje de una pradera permanente fertilizada con magnesio

This research was conducted for two years to evaluate magnesium fertilizer application (0, 24, 48 and 96 kg ha-1 year-1 of Mg) on a permanent pasture composed by Lolium perenne and Trifolium repens as an agronomic alternative of hypomagnesaemia management in grazing herds. The effect on magnesium, calcium, potassium and sodium concentration in the pasture dry matter and the ratio between cations were evaluated. The research was carried out on an Hapludand (Valdivia serie) with an initial available magnesium content of 0.8 cmolc kg-1. Pasture dry matter production was not affected by magnesium fertilization, nevertheless, the concentration of magnesium in the pasture dry matter increased proportionally to the magnesium applied. A weighed average showed an increase of 0.006 and 0.012 g kg-1 of dry matter for each kg of magnesium applied during the first and second year, respectively. In addition, the magnesium fertilization decreased the calcium dry matter concentration, but it did not affect potassium and sodium dry matter concentration. The ratios between calcium/magnesium, potassium/magnesium and sodium/magnesium decreased with the increase of the magnesium fertilization rate.This research was conducted for two years to evaluate magnesium fertilizer application (0, 24, 48 and 96 kg ha-1 year-1 of Mg) on a permanent pasture composed by Lolium perenne and Trifolium repens as an agronomic alternative of hypomagnesaemia management in grazing herds. The effect on magnesium, calcium, potassium and sodium concentration in the pasture dry matter and the ratio between cations were evaluated. The research was carried out on an Hapludand (Valdivia serie) with an initial available magnesium content of 0.8 cmolc kg-1. Pasture dry matter production was not affected by magnesium fertilization, nevertheless, the concentration of magnesium in the pasture dry matter increased proportionally to the magnesium applied. A weighed average showed an increase of 0.006 and 0.012 g kg-1 of dry matter for each kg of magnesium applied during the first and second year, respectively. In addition, the magnesium fertilization decreased the calcium dry matter concentration, but it did not affect potassium and sodium dry matter concentration. The ratios between calcium/magnesium, potassium/magnesium and sodium/magnesium decreased with the increase of the magnesium fertilization rate.Como una alternativa de manejo agronómico de la hipomagnesemia en rebaños a pastoreo se estudió, durante dos años, el efecto de la fertilización magnésica (0, 24, 48 y 96 kg ha-1 año-1 de Mg) sobre la concentración de magnesio, calcio, potasio y sodio y sus relaciones en la materia seca del forraje cosechado de una pradera permanente compuesta por Lolium perenne y Trifolium repens. El ensayo se realizó en un suelo Hapludand (Serie Valdivia) con un nivel inicial de 0,8 cmolc kg-1 de Mg. No se detectó un efecto de la fertilización magnésica sobre la producción de materia seca de la pradera, pero la concentración de magnesio en la materia seca se incrementó proporcionalmente a la dosis de magnesio aplicada. Considerando el promedio ponderado anual el aumento de la concentración de magnesio fue de 0,006 y 0,012 g kg-1 de materia seca por cada kg de magnesio aplicado, durante el primero y segundo año, respectivamente. La fertilización magnésica disminuyó la concentración de calcio, pero no afectó la concentración de potasio ni de sodio en la materia seca del forraje cosechado. Las relaciones entre Ca/Mg, K/Mg y Na/Mg en general disminuyeron en la medida que aumentó la dosis de fertilización con magnesio

Is the reputation of Eucalyptus plantations for using more water than Pinus plantations justified?

The effect of Eucalyptus plantations on water balance is thought to be more severe than for commercial alternatives such as Pinus species. Although this perception is firmly entrenched, even in the scientific community, only four direct comparisons of the effect on the water balance of a Eucalyptus species and a commercial alternative have been published. One of these, from South Africa, showed that Eucalyptus grandis caused a larger and more rapid reduction in streamflow than Pinus patula. The other three, one in South Australia and two in Chile, did not find any significant difference between the annual evapotranspiration of E. globulus and P. radiata after canopy closure. While direct comparisons are few, there are at least 57 published estimates of annual evapotranspiration of either a Eucalyptus or Pinus species. This paper presents a meta-analysis of these published data. Zhang et al. (2004) fitted a relationship between the crop factor and the climate wetness index to published data from catchment studies and proposed this approach for comparing land uses. We fitted the same model to the published data for Eucalyptus and Pinus and found that the single parameter of this model did not differ significantly between the two genera (p=0.48). This implies that for a given climate wetness index the two genera have similar annual water use. The residuals compared to this model were significantly correlated with soil depth for Eucalyptus, but this was not the case for Pinus. For Eucalyptus the model overestimates the crop factor on deep soils and underestimates the crop factor on shallow soils.</p

Is the reputation of Eucalyptus plantations for using more water than Pinus plantations justified?

The effect of Eucalyptus plantations on water balance is thought to be more severe than for commercial alternatives such as Pinus species. Although this perception is firmly entrenched, even in the scientific community, only four direct comparisons of the effect on the water balance of a Eucalyptus species and a commercial alternative have been published. One of these, from South Africa, showed that Eucalyptus grandis caused a larger and more rapid reduction in streamflow than Pinus patula. The other three, one in South Australia and two in Chile, did not find any significant difference between the annual evapotranspiration of E. globulus and P. radiata after canopy closure. While direct comparisons are few, there are at least 57 published estimates of annual evapotranspiration of either the Eucalyptus or Pinus species. This paper presents a meta-analysis of these published data. Zhang et al. (2004) fitted a relationship between the vegetation evaporation efficiency and the climate wetness index to published data from catchment studies and proposed this approach for comparing land uses. We fitted this model to the published data for Eucalyptus and Pinus and found that the single parameter of this model did not differ significantly between the two genera (p = 0.48). This was also the case for all parameters of an exponential relationship between evapotranspiration and rainfall (p = 0.589) and a linear relationship between the vegetation evaporation index and rainfall (p = 0.155). These results provide strong evidence that, for a given climate wetness index, the two genera have similar annual water use. The residuals compared to the model of Zhang et al. (2004) were significantly correlated with soil depth for Eucalyptus, but this was not the case for Pinus. For Eucalyptus, the model overestimates the vegetation evaporation efficiency on deep soils and underestimates the vegetation evaporation efficiency on shallow soils