What is the primary purpose of a prism in forestry?

The primary purpose of a prism in forestry is to determine if a tree is in or out of a specified sample plot. This is primarily done using a tool known as a wedge prism or a basal area prism, which helps foresters assess tree density and manage forests more effectively. When the prism is viewed from a certain angle, it allows the forester to assess whether a tree meets the criteria for inclusion within a sample plot based on its size. This helps in obtaining accurate measurements of forest density and basal area, which are critical for sustainable forest management practices.

The other options relate to different aspects of forestry or tree assessment. While measuring tree height, assessing soil quality, and estimating tree age are all important forestry practices, they are not functions of a prism. Instead, those activities typically require other tools or methods, highlighting the specific role that prisms play in the context of forest sampling and management.