In this part

• Components of stand structure 
• Why is stand structure important to biodiversity?
• Application to forest management

1. Describe stand structure 

2. Identify forest management applications for stand structure 

3. Describe the role of stand structure in forest biodiversity

 The questions on the left side of the page are to assist you in keeping actively involved in the material and your learning Answer them silently or write out the answers.

Background
to forest management

In BC, typical forest management objectives were designed to optimize the production of wood products from the working forest.

Consequently, the goal of stand level activities was to harvest the sites and quickly restock them with commercial species, and to apply stand-tending practices that would ensure full site occupancy and maximum growth production.

In some environments where uneven-aged stands originally occurred, (note that these are not all that common) stands have been simplified through forest management.

In other environments where large areas of one age and species occurred naturally, forest management has increased forest-level and stand level diversity.   

Forest management has impacted the stand structural diversity in some or all of the following ways:

• Reduced size, quality, and distribution of coarse woody debris
• Reduced the natural distribution of standing dead trees/wildlife trees
• Reduced canopy layering and gaps
• Reduced diversity of understorey vegetation
• Reduced variability in tree sizes, and ages

All of these contribute, in varying degrees, to the risk of reducing stand level biodiversity in BC. We do not yet know the severity of the risk, but many suggest that there will be a decline in native species diversity, and an increase in the number of endangered species.

A diminished level of diversity could also reduce opportunities for economic diversification.

Components of stand structure

Figure 7: Horizontal and vertical stand structure

Stand structures refers to the vertical and horizontal make-up or appearance of the stand. Old forests tend to have high structural diversity, with some or all of the following characteristics:

• Multiple canopy layers of trees

• Wide variety of tree sizes (heights and diameters)

• Some very large trees (relative to the rest of the trees), scattered throughout the stand

• Mixed species of conifers and deciduous patches

• Significant amounts of course woody debris of all sizes and stages of decay

• Scattered windthrown trees

• Brush pockets associated with canopy gaps

• Varying amounts of decadence, (i.e., broken tops, split trunk, multiple tops, large limbs)

• Significant amounts of lichens growing above ground level on very large trees

These features create a range of habitats for a wild variety of plants and animals. Many management practices aimed at promoting biodiversity actually focus on promoting or protecting some of these features.

The structural diversity of stands reflects the natural disturbance patterns across a landscape, and the natural successional processes that have occurred since the disturbance.

Before reading on, what do you already know about them?

There are two kinds of stand structures:

      1. Horizontal structure

      2. Vertical structure