The Polylepis forests in the central Andes of Peru remain in hostile environments due to their location above 4000 meters of altitude. They are home to a great biodiversity with a high level of endemism and are extremely vulnerable to climate change and human pressure. Variations in rainfall and temperature have been affecting plant health. These aspects have led to the analysis of the physiological response of plants through water stress and NDVI, in dry periods and related to altitudinal gradients and slope, of five forests located in the regions of Junin and Lima, where the species Polylepis rodolfo vasquezii, P. canoi and P.flavilpila are found. Seven 15 x 21 m plots and 10 sub-plots were established, distributed in the lower, middle and upper parts of the forest. The water potential of leaflets was measured by a Scholander pressure pump in a Pascale unit, microclimate variations by means of installed soil and air humidity and temperature sensors; the NDVI by means of multispectral images captured by an unmanned airborne vehicle. Water stress was different among species and changed according to the altitudinal gradient, soil hydrological variation and temperature. Leaflet size adaptation related to stress changes and a high correlation of NDVI with plant stress status were observed.