Effects of tree mixture on forest productivity: tree species addition versus substitution

Abstract

1. Mixture effect on stand productivity is usually apprehended through a substitutive approach, whereby productivity in mixed stands is compared to productivity in monocultures, at equivalent stand density. This approach has proved that in many cases mixed stands perform better than monospecific forests, however, we do not yet have a solid theory about species behaviour in the mixture or even guidelines for combining species. The addition of a second tree species to an existing mono-specific stand has received much less consideration. Yet, this approach has the potential to separate the facilitation effect from the complementarity effect.2. We compared the effect of tree species substitution vs. addition on the productivity of maritime pine and silver birch in a young tree diversity experiment implemented in 2008 in SW France.3. Substituting pines with birches to create two-species mixtures resulted in an increase of tree productivity at stand level beyond what was expected from monocultures (i.e., overyielding). In contrast, creating mixture through the addition of birches to pine stands had no effect on the maritime pine stand productivity (transgressive mixture effect not significant). This absence of effect is produced by two distinct density-dependence responses at an individual level.

Restoring tree species mixtures mitigates the adverse effects of pine monoculture and drought on forest carabids

“…Previous studies at the same experimental site have shown that pines and birches are much taller than oaks because the latter have a lower growth rate (Damien et al 2016;Toïgo et al, 2022). While maritime pines were on average 7.80 m tall in 2016 and birches 6.48 m, oaks were only 1.38 m (Pyrenean oak), 1.42 m (pedunculate oak) and 1.77 m (green oak), that is, similar average height as the understory vegetation 1.03 m (Figure S2).…”

Optimal forest management of pure and mixed forest plantations in the southeastern United States

“…A recent study of mixtures of Pinus pinaster and Betula pendula in France found the same effect (Toigo et al, 2022). The addition of the pioneer species (B. pendula) with low demands on soil, water and nutrients can boost the productivity of the whole stand.…”

Динаміка Продуктивності Деревостанів Східного Полісся України

“…Подібна тенденція наявна під час порівняння за матеріалами лісовпорядкування фактичної продуктивності деревостанів із природною (Vorobyov 1959) або потенційною (Turkevich et al 1973, Ostapenko & Tkach 2002, Vedmid & Gavrilov 2004, Tkach et al 2018. Величини середнього запасу на 1 га змінюються внаслідок зміни площі вкритих лісовою рослинністю земель, вікової структури деревостанів та участі деревних порід у складі мішаних деревостанів (Vasiliev 1962, Toïgo et al 2022.…”