Comparative growth and yield performance of sweet chestnut in high-forest and coppice systems in young plantations

We compare growth and yield of sweet chestnut in coppice and high-forest systems up to 24 years of age in northern Portugal. In the coppice, data from 4 permanent plots submitted to different management models for small (P1), medium (P2) and large (P4) diameters, including a plot without intervention (P3), were used. Management model in P4 (1 shoot at the end of rotation) is converging to a similar product as high-forest over time. Site index (SI) for the coppice is 15 m of dominant height (hdom) at 20 years. The same SI was used when selecting data from permanent plots in high-forest for the comparison. Individual-tree equations previously developed were used to obtain stem volumes. Biomass of stem was obtained from volume using wood density. Results show that coppice for similar ages and SI, produces more stem volume ha^‑1 than high-forest in any situation up to 24 years. At this age, height of the mean tree (hg) and hdom are lesser in the high-forest than in the coppice’s management model with similar target (P4). In contrast, diameter of the mean tree (dg) and dominant diameter (ddom) are similar in both systems. Results also show that P4 in coppice system produced more 100 m³ ha^‑1 of stem volume than the high-forest at age 24. However, mean annual increment (MAI) in stem volume in high-forest is still increasing as opposed to the coppice. Thus, coppice system produces more biomass in young ages than high-forest (MAI in biomass: 9 t ha^‑1 year^‑1 against almost 4 t ha^‑1 year^‑1, respectively). Managing coppice for a final target similar to high-forest introduces flexibility in sylviculture, allowing both high amount of biomass production in young stages, and long-life products at the end of rotation.