Effect of tree species mixing on stand structural complexity

The proportion of mixed-species forests is presently increasing since they are commonly seen as providing a higher level of many ecosystem goods and services than monospecific stands. This may be due to a more complex three-dimensional distribution pattern of plant elements, which has often been noted, but to date rarely been quantified. In the present study, we used terrestrial laser scanning data to analyze the relationship between tree species mixing and stand structural complexity in three regions of Germany. We examined 60 forest plots representing commercially important and typical species combinations for Central Europe. The results showed an increasing but saturating relationship between stand structural complexity and tree species diversity. Moreover, we found that as the proportion of broadleaved trees increased, the stand structural complexity of coniferous stands also increased. Our study provides evidence that the conversion of monospecific conifer stands into mixed forests with broadleaved tree species as well as mixing tree species with interspecific differences in physiological and morphological traits can promote the development of structurally more complex stand structures.