Leaf area index and soil water content responses to pre-commercial thinning in Norway spruce plantations under climate change

Global climate change (GCC) and increasing drought frequency pose athreat tothe stability ofEuropean forests, particularly those ofNorway spruce [Picea abies (L.) Karst.] plantations. Weinvestigated how different pre-commercial thinning (PCT) intensities affect leaf area index (LAI) and its relationship tosoil water content (SWC) inyoung spruce stands innortheastern Czechia. Three permanent research plots ina13-year-old monoculture were subjected tomild PCT, heavy PCT, orleft asanunthinned control inwinter 2019/2020. Thinning caused animmediate decrease inLAI, with averages of8.3 ±1.1 m2·m–2 (mild), 3.8 ±0.5 m2·m–2 (heavy) and 11.1 ±1.1 m2·m–2 (control) in2020. By2023, LAI inthe mildly thinned stand had largely converged with the control, whereas the heavily thinned stand maintained significantly lower LAI. The strongest relationship between LAI and SWC occurred inthe heavily thinned plot (R2 =0.715 in2021), while correlations were weak ortransient inthe mildly thinned and control plots. These results indicate that PCT intensity influences both the magnitude and duration ofLAI reduction and isassociated with differences instand water dynamics. Appropriately adjusted thinning may therefore modestly affect water availability and could contribute toadaptive management ofspruce forests under GCC.