Efectos de la dinámica urbana sobre la estructura de la vegetación y la temperatura de la superficie del Gran San Miguel de Tucumán, Argentina

Ponencia presentada en: VII Congreso de la Asociación Española de Climatología: clima, ciudad y ecosistemas, celebrado en Madrid entre el 24 y 26 de noviembre de 2010.[ES]La urbanización del planeta implica un cambio importante en los usos del suelo y, consecuentemente, de las propiedades térmicas de las superficies terrestres. En este trabajo se analiza el impacto de la urbanización en el Gran San Miguel de Tucumán (Argentina). Se estudia el tipo de vegetación que se recupera en la zona tras el proceso de construcción de la ciudad, la transición de vegetación natural a vegetación de parques y jardines. Además se analiza, a través de imágenes de satélite, la temperatura de las superficies de la zona en estudio, relacionándose los patrones térmicos con las zonas vegetadas de la ciudad. A partir de la temperatura de superficie se calcula el valor de la Isla de Calor Urbana Superficial que, calculada para imágenes diurnas, da valores negativos para finales de invierno y primavera, y positivos para el verano. También a través de las imágenes de satélite se obtiene el aumento de la zona construida entre los años 1992 y 2008 se observa un incremento de la superficie urbana del 66%. Finalmente, se presenta un modelo que podrá ayudar a planificar y afrontar el crecimiento urbano y el consecuente cambio que este provoca en los patrones térmicos de la zona y en su vegetación.[EN]The urbanization of the planet involves an important change in the soil uses. Therefore, thermal properties of the surfaces have changed. In this work the impact of the urbanization is analyzed in the Gran San Miguel de Tucuman (Argentina). It is studied the change from natural vegetation cover to urban vegetation as squares or gardens. Moreover, satellite images are used to study the surface temperature, and it is observed that the thermal patterns are connected with the vegetated areas in the city. Land surface temperature is used to measure the value of the Surface Urban Heat Island. This phenomenon is measured using daytime images, negative values are obtained in winter and spring while positive values for summer time. The growing of the built area is monitored with satellite images observing an increase of the urban area of the 66% between year 1992 and year 2008. Finally, an urban growing model is presented; this would help to plan and face up the urban growing and changes in thermal patterns and vegetation.Este proyecto ha sido financiado por la Agencia Española de Cooperación Internacional para el desarrollo (AECID), bajo el proyecto A/018766/08-Efectos de la dinámica urbana sobre la estructura de la vegetación y la temperatura de superficie del Gran San Miguel de Tucumán

Vegetation productivity trends in response to urban dynamics

Urbanization is a global phenomenon with still unknown consequences for vegetation dynamics of urban ecosystems, especially in subtropical areas of developing countries. In this paper we analyze the vegetation productivity trend associated to urban densification and urban expansion during the last decade, in twelve cities of northern Argentina. We used time series analysis of MODIS-NDVI images to reconstruct the phenological patterns to retrieve a productivity trend under three spatial classes of urban dynamics: (1) urban, (2) expansion and (3) periphery. Our results show that trends in vegetation productivity are more associated to the environmental characteristics (basal productivity and climate) than to the land cover class. The average trend in productivity in urban areas ranged between -2.54% year-1 (Metán) and -0.22% year-1 (Concepción). In contrast, the range was much tighter between classes; it was -1.37% year-1 in urban areas and -1.21% in the periphery. In this sense we found significant differences between cities, but no significant differences were observed between classes. Urban growth and urban expansion patterns found in our study suggest the system dynamics is dominated by sprawl patterns rather than by a homogeneous densification. Related to this phenomenon, our results dismissed the idea of urban expansion as the main factor affecting vegetation phenology and supported the hypothesis of regional warming as an explanation for the decrease in vegetation productivity, probably due to the decrease of water balance in arid regions.Fil: Paolini, Leonardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad del Norte Santo Tomás de Aquino; ArgentinaFil: Aráoz, Ezequiel. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad del Norte Santo Tomás de Aquino; ArgentinaFil: Gioia, Antonela. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad del Norte Santo Tomás de Aquino; ArgentinaFil: Powell, Priscila Ana. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentina. Universidad del Norte Santo Tomás de Aquino; Argentin

Primary productivity in cities and their influence over subtropical bird assemblages

Changes in ecosystem structure caused by urbanization produce a reduction in photosynthetic productivity, which can lead to reductions in resource availability for birds. Here, we analyzed the relation between photosynthetic productivity and bird assemblages in a subtropical urban ecosystem, in North-Western Argentina. We used Generalized Linear Models to assess the responses of bird abundance, richness and diversity to photosynthetic productivity, vegetation cover and distance to main natural forest. We found higher bird richness and diversity with increasing photosynthetic productivity and vegetation cover, and with decreasing distance to forests; while total bird abundance was positively related to vegetation cover. When we classified bird species in different groups, based on their use of the environment, we found that species adapted to urban environments were more dependent on photosynthetic productivity, while species related to native forests were more dependent on the distance to source forests. Understanding the factors that affect bird assemblages in cities is important for the development of strategies for urban planning and conservation.Fil: Haedo, Josefina. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Gioia, Antonela. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Aráoz, Ezequiel. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Paolini, Leonardo. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; ArgentinaFil: Malizia, Agustina. Universidad Nacional de Tucumán. Instituto de Ecología Regional. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto de Ecología Regional; Argentin

Size matters: vegetation patch size and surface temperature relationship in foothills cities of northwestern Argentina

Urbanization is one of the most extreme forms of land alteration. Energy fluxes are severely affected and cities tend to have the Urban Heat Island (UHI) phenomenon, although vegetated areas inside cities could have a positive effect in mitigating UHI effect. Our main objective was to analyze the relationship between vegetation characteristics, patch size and land surface temperature (LST) in three urban areas of northwestern Argentina. We selected 38 green spaces of different size distributed in four cities, all located in the eastern foothills of the subtropical mountain forests. We used Landsat TM satellite images to calculate Normalized Difference Vegetation Index (NDVI) and LST. We assessed the net effect of patch size on LST by computing a Difference Temperature Index. At the regional scale, our results showed that vegetation patch size had a direct effect on reducing the LST of the green space. At a local scale, the analysis of the relationship between vegetation on urban green spaces and LST along a gradient of urbanization showed that green spaces with more vegetation tends to reduce LST. The results showed that largest green spaces were between 1.5 and 2.8 °C cooler than the surrounding built. In order to mitigate the UHI effect in cities, larger green spaces appear to be a possible solution.Fil: Gioia, Antonela. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales E Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Paolini, Leonardo. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales E Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Malizia, Agustina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales E Instituto Miguel Lillo. Instituto de Ecología Regional; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Oltra Carrió, Rosa. Universidad de Valencia; EspañaFil: Sobrino, José Antonio. Universidad Politecnica de Valencia; Españ