Polyculture affects biomass production of component species but not total standing biomass and soil carbon stocks in a temperate forest plantation

Abstract

& Key message Over-yielding of stand biomass did not occur in a tree polyculture comprised of Betula pendula, Alnus glutinosa and Fagus sylvatica selected for contrasting traits. This was due to antagonistic interactions between the component species. Fine root dynamics and soil C stocks were unaffected by species mixture. & Context Increasing CO 2 fixation in tree biomass through afforestation and forest management actions has potential for costeffective climate mitigation. The influences of tree mixture on biomass production and subsequent soil C accumulation in polyculture still remain uncertain. & Aims We studied the polyculture of Alnus glutinosa (L.) Gaertn, Betula pendula Roth and Fagus sylvatica L. in a plantation forest to examine the effectiveness of species mixtures as a tool for increased biomass production and soil C accumulation. & Methods Tree biomass was estimated by developing species-specific allometric models and 3 years tree measurement. Fine root biomass and production were estimated by root coring and root-mesh methods. The 'relative yield of mixture' approach was used to examine the mixture effect. & Results In mixture, an additive effect was observed in A. glutinosa (13% increase in basal diameter relative to the monoculture); however, there was no overall effect of mixture on total standing biomass due to the suppression of F. sylvatica (2.75 g m −2 reduction in woody biomass). Fine root biomass production showed no mixture effect. The quantity and quality of soil C (top 0.5 m) was not affected by tree mixture. & Conclusion We conclude that the contrasting growth responses of the A. glutinosa, B. pendula and F. sylvatica in polyculture resulted in no over-yielding of standing biomass despite the complementary traits of the component species.

Carbon stocks, partitioning, and wood composition in short-rotation forestry system under reduced planting spacing

“…The higher soil carbon stock in the topsoil may be related with the accumulation of vegetal residue, the amount of organic matter, the root activity, and the microorganism's activity (Lal 2005;Babujia et al 2010;Dawud et al 2016;Ahmed et al 2019). This result agrees with that observed by Lima (2004), who reported the highest carbon content in the 0-5-cm layer in Eucalyptus forest compared with pasture, mostly justified by the presence of forest litter and microorganism's activity.…”