Polylepis woodland occurs in Peru's tropical highlands at elevations between 3,500 and 5,000 m above sea level and Polylepis is the most common tree at timberline in South America. The objective of this study was to assess the total ecosystem carbon stock in a Polylepis incana woodland, i.e., aboveground biomass (canopy trees and understory), root biomass and soil carbon stocks were all quantified. As part of this study, an allometric equation for the quantification of the aboveground biomass of individual P. incana trees was developed for the first time. The most important carbon pool was the soil (39.7 ± 6.9 kg m-2) followed by the aboveground biomass of Polylepis trees (3.8 ± 0.7 kg m-2). The total ecosystem carbon stock was estimated to be 43.9 ± 7.6 kg m-2; thus, 90.6 % of the ecosystem carbon stock is soil carbon. © 2014 Swiss Botanical Society.