Seasonality of water availability, plant phenology, and plant transpiration in a brazilian Caatinga environment investigated by in situ and remote sensing data

• Autor(a) principal: Rennan Andres Paloschi
• Data de Publicação: 2020
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações do INPE
• Texto Completo: http://urlib.net/sid.inpe.br/mtc-m21c/2021/01.13.15.06

The vegetation water use was investigated in three experimental areas in Caatinga, the largest seasonally dry forest in South America. In one of the sites, environmental drivers on phenology of woody species and their relationship with transpiration were identified and analyzed. In the other sites, the relationship between Remote Sensing data with the phenological response and the water condition of the soil was evaluated. To monitor the phenological evolution with Remote Sensing, vegetation indices were used: normalized difference vegetation index (NDVI); soil-adjusted vegetation index (SAVI) and; green chromatic coordinate (GCC). The GCC extracted from automated digital camera images in the field was used as a representative of phenology and ground truth. Were obtained NDVI, SAVI and GCC indexes from the Sentinel-2A and 2B satellites data, NDVI MYD13Q1 and MOD13Q1 from the MODIS sensor on the Terra and Aqua platforms and the NDVI calculated from the WFI camera data of the CBERS-4 satellite. Environmental factors included rain, air temperature, soil moisture, liquid radiation and vapor pressure deficit. To monitor the water condition we have installed sensors for humidity and soil matric potential. To monitor vegetation water use sap flow sensors were installed. Our study demonstrated that GCC data close to the surface played an important role in allowing individual species monitoring, while species flow data were better correlated with orbital NDVI, SAVI and GCC than with GCC close to the surface of the species. The plants wood density seemed to affect the transpiration cessation times in the dry season, since species with less wood density reach negligible transpiration values earlier, in the beginning of the dry season, than those with high density. The results show that the availability of water in the soil is the main limiting factor for transpiration for more than 80 % of the year, and that both the phenological response given by the vegetation indices and the use of water given by the sap flow are directly related to water availability when the relative saturation in the soil profile is below 0.25.