In temperate environments, ring width, cell size and cell wall thickness within the xylem of trees are known to be affected by climate conditions. Less is known about the effect of climate conditions on the chemical characteristics of the xylem, which are important for the susceptibility of the tissue towards fungal infections as well as for the degradability of the material within the forest ecosystem. We explored the use of infrared microspectroscopy to investigate the possible effects of temperature and drought on the relative amount of cell wall biopolymers, ie the ratios between cellulose, hemicellulose and lignin in the earlywood xylem cell walls of Norway spruce (Picea abies (L.) Karst.) in temperate forests. Drought and warm temperatures were significantly correlated to the hemicellulose to lignin ratio of the earlywood formed the following year, perhaps due to a reduced amount of stored resources being available for xylem formation.