## 5 Conclusions  
In this study, a relationship between the Total Leaf Area (TLA) and the Normalized Difference Vegetation Index (NDVI) was developed to analyse the effect of missing vines on NDVI values at pixel level (\(10\times 10\) m). This study has demonstrated that it is possible to estimate quantitatively the impact that the decrease in vegetation in a vineyard has on the NDVI values. Our results show that it is possible to use the NDVI calculated from the Sentinel-2 images to identify the change in the vegetation in the pixel. Furthermore, it is worth noting that the reduction in the NDVI values is proportional tothe reduction in the vegetation, following a linear relationship. The quantitative relationship obtained in this study is valuable since a vineyard, once established, generally loses grapevines each year due to diseases, abiotic stress, etc., so it is worth analysing the effect of the missing vines in order to have a clear understanding of the vineyard vigour.  
The field experiment was conducted in a vineyard with a vertical trellis and this system has become a standard in today's viticulture. Moreover, in this work, the results of the two experiments are very similar, since the greenhouse experiment simulated the same row and plant distance as the field experiment, so the results obtained in this study could be used as a reference for vineyards with similar trellis characteristics (distance between rows and vines). However, it might be worthwhile to check whether this result can be extrapolated to other trellis systems or vineyards with different canopy or soil management practices, analysing the influence of the elimination of vegetation in vineyards with different soils and different characteristics. Further research would be desirable in this direction.  
In further studies, it might be interesting to explore the possibility of removing a specific area of vines within a vineyard to calibrate the entire vineyard and use this technique to calibrate the background adjustment factor (L) of vegetation indexes such as SAVI, or even develop new indexes that take into account parameters related to the canopy, such as the influence of shadows or the linear meters of vertical trellis contained in each pixel.  
Although the results are clear and promising, the limitations of this study should be considered due to the complexity and effort involved in an operation of this type in a vineyard. Operations on a larger scale are desirable in order to cover a greater number of pixels and vines to obtain more robust results covering different vineyard conditions.  
Conceptualization: S.V., E.B., J.A.R., C.P.-E.; methodology: S.V., E.B., J.A.R., C.P.-E., R.V.; Data acquisition: S.V., E.B., R.V., C.P.-E.; Data processing: S.V., E.B., R.V., C.P.-E.; Data analysis: S.V., E.B., C.P.-E.; resources, S.V., E.B., J.A.R., C.P.-E.; writing--original draft: [PERSON]; writing--review and editing: [PERSON], C.P.-E.; supervision: [PERSON], J.A.R., C.P.-E.; project administration: [PERSON], J.A.R.; funding acquisition: [PERSON], J.A.R. All authors have read and agreed to the published version of the manuscript.  
This work has been possible thanks to the economic support of Junta de Castilla y Leon (Spain), Instituto Tecnologico Agrario de Castilla y Leon (ITACyL), the project INIA RTA2014-00077-C02, FPI-INIA2016-017 and FEDER funds.  
We thank the staff of Viticulture for their cooperation in the vineyard operations.  
The authors declare no conflict of interest.