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Monitoring urban trees sap flow and carbon allocation

Grant number: 20/14163-2
Support type:Scholarships in Brazil - Doctorate (Direct)
Effective date (Start): December 01, 2020
Effective date (End): June 30, 2024
Field of knowledge:Biological Sciences - Botany
Principal researcher:Giuliano Maselli Locosselli
Grantee:Leticia Figueiredo Candido
Home Institution: Instituto de Botânica. Secretaria do Meio Ambiente (São Paulo - Estado). São Paulo , SP, Brazil
Associated research grant:19/08783-0 - Functional forests: biodiversity in the benefit of cities, AP.JP

Abstract

Urban expansion results in significant changes in the local climate conditions due to the conversion of the native vegetation by built areas. This land-use change results in an increase in the convective activities in the city, affecting heat transfers, cloud formation and the precipitation regime. Part of these changes can be mitigated by planting urban forests that lead to changes in energy and water flows in cities. Water flow is an essential process for plants to which nutrient transport, respiration and photosynthesis are associated. Due to the assimilation of carbon by the photosynthetic process, trees are also essential instruments as carbon sink. The carbon assimilated by the trees can be allocated in different tissues as structural carbon, especially in wood tissues. In these tissues, the residence time of structural carbon can be from decades to centuries according to the longevity of the species. Another part of the assimilated carbon is allocated to the reserves in the form of starch, with a residence time of a few hours up to about a decade, or in the form of soluble sugars readily available for mobilization. Non-structural carbon reserves are one of the main mechanisms of tree resilience to adverse environmental conditions. These reserves can be used in the maintenance of water flows within the plant body, in addition to being used during the reactivation of the cambium activity and growth, and in extreme events that impact the process of carbon assimilation of trees. These contributions of trees to environmental conditions in cities, mediated by physiological processes, are known as ecosystem services, an essential element in the proposals for Nature-Based Solutions. However, the urban environment itself has the potential to affect the development of trees, through the modulation of these essential physiological processes, thus affecting the magnitude of ecosystem services. In order to understand the contribution of tree species to the urban environment, by means of water vapor fluxes, and carbon sink, and to define groups of species more tolerant to the urban environment, this project aims to determine the volume of transpired water and amount of assimilated carbon for 6 tree species present in Ibirapuera and Fontes do Ipiranga Parks. The sapflow will be estimated using sapflow sensors that will be installed in three individuals of each species. In these same individuals the dynamics structural carbon allocation will be analyzed by means of X-ray densitometry of the growth rings and analysis of cell-wall monosaccharides. The concentrations of non-structural carbon, soluble sugars and starch, will be analyzed once every three months. This project is part of the project "Functional Forests - biodiversity in favor of cities" (2019/08783-0), which will allow the temporal comparison of evapotranspiration rates and the allocation of carbon with similar flows measured in these urban forests through the Eddy Covariance System. The data will be analyzed using linear models, time series and complex correlation networks to analyze the water and carbon balance between shade-tolerant and intolerant species. (AU)