Growth performance, windthrow, and insects: meta-analyses of parameters influencing performance of mixed-species stands in boreal and northern temperate biomes

Stand structure is a key attribute of forest ecosystems. Mixed-tree plantations are widely felt to be the appropriate option for providing a broad range of goods and environmental services and to reduce susceptibility to natural hazards. However, the debate continues whether mixed plantations can achieve greater financial return than monocultures can. In this study, mixed-species stands of conifers and hardwood species were analyzed in consideration of economically relevant factors. Growth performance and resistance to hazards and pests are widely noted in the literature and are of general economic interest. Thus meta-analyses of relevant studies were conducted to test the following hypotheses: (1) mixing tree species has no significant influence on growth performance or resistance against hazards and pests and, if refuted, (2) mixing tree species causes mainly negative effects on growth performance and resistance against hazards and pests. However, a positive impact of mixing tree species was proven for resistance against windthrow and pests. The meta-analysis on growth performance just as well indicates a positive effect of mixing tree species. Overall, these positive results underscore the need for a large number of additional studies to examine different silvicultural systems to develop optimal management prescriptions to benefit from positive interactions. La structure du peuplement est un attribut cle des ecosystemes forestiers. Les plantations mixtes sont largement considerees comme une option appropriee pour fournir une large gamme de produits et de services environnementaux ainsi que pour reduire la predisposition aux catastrophes naturelles. Cependant, le debat persiste a savoir si les plantations mixtes peuvent procurer un meilleur rendement financier que les monocultures. Dans cette etude, des peuplements mixtes composes d'especes feuillues et resineuses ont ete analyses en tenant compte de facteurs pertinents du point de vue economique. La croissance et la resistance aux catastrophes et aux ravageurs sont couramment mentionnees dans la litterature et presentent un interet economique general. Des meta-analyses des etudes pertinentes ont par consequent ete realisees pour tester les hy-potheses suivantes: (1) le fait de melanger les especes d'arbre n'a aucun effet significatif sur la croissance ou la resistance aux catastrophes et aux ravageurs et si cette hypothese est refutee, (2) le fait de melanger les especes d'arbre a surtout des effets negatifs sur la croissance et la resistance aux catastrophes et aux ravageurs. Toutefois, un effet positif du melange des especes a ete demontre dans le cas de la resistance au chablis et aux ravageurs. La meta-analyse indique egalement que le melange des essences a un effet positif sur la croissance. Dans l'ensemble, ces resultats positifs soulignent la necessite d'ef-fectuer un grand nombre d'etudes additionnelles pour examiner differents systemes sylvicoles dans le but d'elaborer des prescriptions d'amenagement optimales pour beneficier des interactions positives. [Traduit par la Redaction]
Introduction Until the end of the 18th century, central European deciduous forests were degraded. Although foresters as well as scientists have been discussing whether or not pure or mixed-species stands [...]