Growth and carbon capture of grey alder (Alnus incana (L.) Moench.) under north European conditions - Estimates based on reported research

Biomass from woody crops is regarded as a future major source of renewable energy. Wood production therefore has to be enhanced to meet the energy needs of an increasing population. This can be reached by using fast-growing tree species. Grey alder (Alnus incana (L.) Moench.) is an indigenous and fast-growing species, which is well adapted to the harsh climate of northern Europe, and could complement other biomass-oriented species used today. This study aimed to assess the potential for wood production and carbon (C) sequestration in biomass and soil of grey alder plantations under north European conditions. The estimates were based on literature data on above- and below ground biomass production, including fine roots, biomass allocation patterns and litter decomposition. By applying logistic functions on production figures and adding an estimated breeding response, grey alder would be able to produce on average 6-7 Mg ha−1 yr−1 of above ground woody biomass during a rotation up to 25 years. This would significantly contribute to increased biomass availability in the Nordic and Baltic countries when applied on agricultural land. By assuming that grey alder will mostly be used on areas suitable for the species, e.g. sites with harsh climate or moist conditions, an estimate of 560,000 ha of newly abandoned agricultural land will be available. Thus, afforestation of those areas with grey alder would result in a total annual increase of aboveground woody biomass of 3.7 Tg, corresponding to 69,000 TJ yr−1. Grey alder would also be an efficient C sink when used on newly abandoned agricultural land. Using the same areas as for biomass the annual C sequestration in biomass and soil would reach 2.6 Tg C. These figures show that grey alder has a potential to be a significant contributor for increasing biomass supply and capture C in northern Europe.