Is European larch (Larix decidua Mill.) a suitable substitute for Norway spruce (Picea abies (L.) Karst.) for agricultural land afforestation?

The European larch (Larix decidua Mill.) is one of the most economically important European coniferous species. With the expected decline of Norway spruce (Picea abies (L.) Karst.), the importance of this tree species may increase in the afforestation of new areas and subsequent CO2 fixation in the context of climate change mitigation if its wood production and quality relative to spruce is high enough. This study aims to assess the suitability of larch for afforestation of former agricultural land compared to spruce, not only in regards to production and stand structure, but also the quality of the wood produced - wood density, shrinkage, and compression strength. The monospecific stands and wood of both species from afforested agricultural land were compared with original forest land in the Orlicke hory Mountains (Czech Republic) based on 24 measured research plots, and 598 trees. The biomass of larch stands aged 66-71 years was significantly higher on agricultural land (506 t ha(-1)) compared to forest land (399 t ha(-1)), similar to spruce (508 vs. 314 t ha(-1)), with no difference between tree species detected. By contrast, larch stands achieved higher structural differentiation and complex diversity when compared to spruce, especially on forest land. For both species, the stands on forest land also showed a lower proportion of stem rot (32%) compared to agricultural land (67%). Primarily, lower (by 10%) incidence of parasitic fungal infestation of larch was observed compared to spruce. Regarding wood quality, a significant effect of land use on wood density was confirmed for both species. Larch is therefore clearly a suitable alternative to spruce for the afforestation of former agricultural land without impact on fungal pathogens and deterioration of wood quality. Moreover, larch and spruce stands on afforested agricultural land have a high production potential and biomass carbon sequestration (by +45% on average) compared to forest land.