## 5 Conclusions  
The cycles of ecosystem productivity and evapotranspiration are strongly associated in the Caatinga biome, where the number of dry days is a more limiting factor for WUE than the actual amount of precipitated water. The seasonality of productivity pulses is directly related to variations in local precipitation. The characterization of canopy phenology showed a good correlation between the EVI and NDVI seasonality, and energy fluxes and local productivity. Our results showed that both vegetation indices peaked a few days before the end of the wet season, which was also observed through GPP data. GPP was positively associated with the variation in rain days, suggesting a coupling between the production of new leaves and photosynthetic capacity phenology, with a pattern of higher productivity and maximum carbon assimilation at the peak of the wet season, under non-limiting water availability conditions. The NDVI and EVI managed to accurately describe interannual variations in vegetation response to environmental factors, corroborating the fact that water availability (also associated with days with/without rain) is the main phenological factor of this ecosystem. Indeed, it can alter vegetation phenology during extreme years and consequently affect ecosystem productivity. Despite GPP MODIS data considerably overrating tower-measured GPP, our study retrieved better correlations between datasets if compared to other similar studies conducted in tropical forests, highlighting the potential usability of these remote sensing tools for the monitoring of Caatinga phenology.  
In the present research article, the individual contributions were followed by: conceptualization: G.B.C., K.R.M., C.M.Se.S. and B.G.B.; methodology: G.B.C., K.R.M., L.B.V., G.V.A., P.R.M., T.V.M. and R.R.F.; software and data analysis: G.B.C., K.R.M., L.B.V., G.V.A., T.V.M. and R.R.F.; formal analysis: G.B.C., K.R.M., C.M.Se.S., B.G.B., C.P.O., W.A.G., P.E.O. and S.C.; resources: A.C.D.A. and R.S.C.M.; data curation: G.B.C., K.R.M., L.B.V. and G.V.A.; writing--original draft preparation G.B.C., K.R.M., C.M.Se.S. and B.G.B; writing--review and editing. T.V.M., C.P.O., W.A.G., P.E.O. and M.U.G.A.; project administration, C.M.S.S. and B.G.B.; funding acquisition, A.C.D.A. and R.S.C.M. All authors have read and agreed to the published version of the manuscript.  
The authors are thankful to the Brazilian National Institute of Semi-Arid (INSA) for funding the project which originated the EC data used in this study. We are also thankful to ICMBio (Chico Mendes Institute for Biodiversity Conservation) for providing access to the experimental site and to the ESEC-Serido (Ecological Station of Serido) for supporting experimental activities. The authors are also thankful to the Coordination for the Improvement of Higher Education Personnel (CAPES) for the postdoctoral funding granted to KRM and to the National Council for Scientific and Technological Development (CNPq) for the research productivity grant of the last author (Process n\({}^{\circ}\) 303802/2017-0) and financial support of CNPq, through undergraduate research project (PIBIC-UFOPA) and the project NOWCDCB: National Observatory of Water and Carbon Dynamics in the Caatinga Biome(INCT -MCTI/CNPq/CAPES/FAPs 16/2014, grant: 465764/2014-2) and (MCTI/CNPq N\({}^{\circ}\) 28/2018, grant 420854/2018-5).  
**Data Availability Statement:** Not applicable.  
**Conflicts of Interest:** The authors declare no conflict of interest and the funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.