Combining satellite-derived forest deadwood estimates and vegetation modelling to predict drought impacts on Norway spruce forest biomass, timber harvest and carbon cycling in Central Europe

Between 2018 and 2020, severe summer droughts caused unprecedented mortality of Norway spruce (Picea abies) in Central Europe. Large amounts of standing deadwood remained in forests, appearing grey or brown and contrasting with surrounding vegetation, making them detectable via remote sensing. Remote sensing-based monitoring of tree mortality is an important source, alongside ground-based observations, providing consistent spatial and temporal coverage over large areas.

In this study, we used satellite-derived standing deadwood data to develop a weather-driven empirical model of Norway spruce mortality and integrated it into the European forestry version of the dynamic vegetation model LPJ-GUESS. The model successfully reproduces observed patterns of tree mortality and associated biomass declines in Germany for 2010–2020. Summer solar radiation anomalies emerged as a key predictor, reflecting the combined effects of drought stress, canopy heat stress, and increased bark beetle activity. Incorporating large-scale satellite data substantially improved the model’s explanatory power, outperforming previous approaches based solely on ground-based mortality data.

Future simulations (2021–2070) under RCP2.6 and RCP8.5 scenarios indicate recurring drought-induced mortality comparable to post-2018 events, resulting in substantial reductions in forest carbon stocks and increases in calamity timber, while harvests of target-diameter timber are projected to decline in subsequent years. Without the weather-driven mortality component, LPJ-GUESS strongly underestimates drought impacts.

Our results highlight the significant risks to carbon storage in Norway spruce-dominated forests under recurring droughts in Germany. Given the central role of forests in Germany’s climate mitigation strategy, continued reliance on Norway spruce plantations poses challenges to both climate goals and the stability of the timber industry. We strongly recommend a rapid transition to diverse mixed forests across Central Europe to mitigate these risks.