URBAN TREES AS BIOMONITORS OF ENVIRONMENTAL CHANGES AND STRESS CONDITIONS IN CITIES OF ARID ZONES. STUDY CASE: MENDOZA METROPOLITAN AREA-ARGENTINA.

MARTINEZ CLAUDIA FERNANDA

Simposio; 1 st AFRICA FORUM ON URBAN FORESTS; 2021

FAO - UNOHABITAT

The urban forest of Mendoza-Argentina is integrated of the set of public trees aligned in parallel to road channels and arranged in green spaces, parks and squares. It has great environmental, urban and cultural importance. This intense afforestation has turned a natural arid region into a suitable place for the development of human life, the habitability of public space and gives the province the character of an "oasis city". However, climate change on a global scale and stress conditions on a local scale, such as water scarcity, increased pollutants and increased urban temperatures, condition the sustainability and the urban trees growth. Previous evidence shows symptoms of water stress associated with thermal stress, whose impact on tree growth is significant and necessary to evaluate from variables such as photosynthetic rates, water status and evolution of the forest canopy. The proposed methodology considers the field survey of urban trees, measurement of dasonomic, dendrochronological and ecophysiological variables. The impact of water stress is carried out by determining the evolution of the forest canopy using ´i-Tree Canopy´, complemented with a spatial analysis with QGIS and the development of vegetation indices such as NDVI, SAVI and ICAU. The study of thermal stress is carried out by thermographic analysis in urban cases of differential construction density, complemented with measurement of leaf temperature. The methodology is completed with the analysis of elements that indicate water stress and pollutants (Calcium and heavy metals) in the annual growth rings. The results obtained so far indicate that variations in water supply and environmental temperatures are reflected in the growth of the annual rings. Water availability and summer temperature play an important role. Warm summers show less growth and formation of narrow annual rings. The correlation models show that the availability of water in the soils is the variable with the greatest influence, and the higher air temperature during the growth period accentuates the dehydration of the soils, causes water deficit, thermal stress and consequently, lower growth. forest. The analysis of thermographic images reveals that the forest canopy is at a lower temperature than the surrounding environment. The average surface temperatures are 29.7ºC for Platanus hispanica and 28.9ºC for Morus alba, lower than the average air temperature and the temperatures of the horizontal and vertical surfaces.