Researchers used forest inventory data and growth models to assess the quality of timber in Norway spruce trees over time. They analyzed tree age, height, and diameter to predict internal structure and wood properties. In the Vosges district, they found that between 1973 and 1981, forest area and volume increased, and between 1981 and 1992, volume continued to rise. They also compared tree heights and ages, as well as timber properties, over the three time points. The study suggests that fertility changes should be considered in models predicting tree growth and wood quality.