|Aim of study: We aim at (i) developing a reference definition of mixed forests in order to harmonize comparative
research in mixed forests and (ii) briefly review the research perspectives in mixed forests.
Area of study: The definition is developed in Europe but can be tested worldwide.
Material and methods: Review of existent definitions of mixed forests based and literature review encompassing
dynamics, management and economic valuation of mixed forests.
Main results: A mixed forest is defined as a forest unit, excluding linear formations, where at least two tree species
coexist at any developmental stage, sharing common resources (light, water, and/or soil nutrients). The presence of
each of the component species is normally quantified as a proportion of the number of stems or of basal area, although
volume, biomass or canopy cover as well as proportions by occupied stand area may be used for specific objectives.
A variety of structures and patterns of mixtures can occur, and the interactions between the component species and
their relative proportions may change over time.
The research perspectives identified are (i) species interactions and responses to hazards, (ii) the concept of maximum
density in mixed forests, (iii) conversion of monocultures to mixed-species forest and (iv) economic valuation of
ecosystem services provided by mixed forests.
Research highlights: The definition is considered a high-level one which encompasses previous attempts to define
mixed forests. Current fields of research indicate that gradient studies, experimental design approaches, and model
simulations are key topics providing new research opportunities|