Why is stand structure important to biodiversity? 

A forest stand with diverse stand structure provides a greater diversity of habitats than do sites with very little structural diversity.

For example, the presence of understorey brush provides protective and thermal cover for small mammals and nesting birds. 

These brush areas also play an important role in forest productivity, through litter fall and in their association with nitrogen-fixing bacteria. 

Multi-layered canopies are able to provide a number of habitats for different bird species. The upper canopy is frequented by raptors, for perching and nesting. As well, researchers are discovering unique populations of insects, lichens, and epiphytic plants in the upper canopies of old forests. 

Insect feeding birds, such as the pygmy nuthatch and brown creeper are found foraging for insects from the bark in the mid and lower layers of a stand. Juncoes and winter wrens are more frequently found feeding within the ground layer of a stand.

Vertical diversity influences the interior environment of a forest. An old forest, for example, is noted for its relatively stable microclimate (moderated wind, high humidity). These conditions are often critical for the survival of some forest-dwelling plants and animals such as the Northern Spotted Owl.

Name several examples of forest-dwelling plants and animals

Structural diversity is a natural feature of forests. We do not know all there is to know about how it affects ecosystem function but we assume that these features are inherently critical to the long-term sustainability of ecosystem function and health. Therefore, there are many biodiversity guidelines that propose practices aimed at promoting the structural attributes of old forests in managed stands, and across managed landscapes. 

The more diverse we can manage the forests the greater the likelihood of their being able to withstand the pressures of change.